1
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He S, Jin X, Wang D, Hao D, Li Y, Zhu Z, Tian Y, Jiang L. Interfacial Water-Dictated Oil Adhesion Based on Ion Modulation. J Am Chem Soc 2023; 145:24145-24152. [PMID: 37874995 DOI: 10.1021/jacs.3c07975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
Oil adhesion on ionic surfaces is ubiquitous in organisms and natural environments and is generally determined by surface chemical component and texture. However, when adhesion occurs, water molecules at the solid-liquid interface, acting as a bridge not only influenced by the structure and composition of the solid surface but also interacting with the neighboring oil molecules, play a crucial role but are always overlooked. Herein, we investigate the oil adhesion process on a carboxyl-terminated self-assembled monolayer surface (COOH-SAM) in ionic solutions and observe the interfacial water structure via surface-enhanced Raman scattering (SERS) in this system. It is found that the lower the tetracoordinated water content, the stronger the oil adhesion. Compared to monovalent ions, the strengthened binding of multivalent ions to the COOH-SAM surface makes the interfacial water more disordered, which eventually leads to a stronger oil adhesion. Notably, the amount of oil adhesion decreases with an increase in the thickness of the interfacial water region. The interfacial water-dictated oil adhesion has been demonstrated in capillary to simulate the water-driven oil recovery, providing a molecular-level explanation for enhanced oil recovery from low salinity water flooding and also indicating potential applications in intelligent microfluidic and seawater desalination.
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Affiliation(s)
- Shaofan He
- Key Laboratory of Bioinspired Smart Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xu Jin
- Research Institute of Petroleum Exploration and Development PetroChina, Beijing 100083, China
| | - Dianyu Wang
- School of Chemical Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Dezhao Hao
- Key Laboratory of Bioinspired Smart Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yulong Li
- Key Laboratory of Bioinspired Smart Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhongpeng Zhu
- Suzhou Institute for Advanced Research, University of Science and Technology of China, Suzhou, Jiangsu 215123, China
| | - Ye Tian
- Key Laboratory of Bioinspired Smart Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- Suzhou Institute for Advanced Research, University of Science and Technology of China, Suzhou, Jiangsu 215123, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lei Jiang
- Key Laboratory of Bioinspired Smart Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing 100049, China
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2
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Saito T, Kubo M, Tsukada T, Shoji E, Kikugawa G, Surblys D, Kubo M. Molecular dynamics simulations for interfacial structure and affinity between carboxylic acid-modified Al2O3 and polymer melts. J Chem Phys 2023; 159:164708. [PMID: 37888762 DOI: 10.1063/5.0169721] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 10/10/2023] [Indexed: 10/28/2023] Open
Abstract
Controlling the dispersion state of nanoparticles in a polymer matrix is necessary to produce polymer nanocomposites. The surface modification of nanoparticles is used to enable their dispersion in polymers. Moreover, molecular dynamics (MD) simulations are useful for revealing the interfacial properties between nanoparticles and polymers to aid in the design of materials. In this study, the effect of surface coverage, modifier length, and polymer species on the interfacial structure and affinity between surface-modified Al2O3 and polymer melts were investigated using all-atom MD simulations. Hexanoic, decanoic, and tetradecanoic acids were used as surface modifiers, and polypropylene (PP), polystyrene (PS), and poly (methyl methacrylate) (PMMA) were used as polymers. The work of adhesion Wadh and the work of immersion Wimm were selected as quantitative measures of affinity. Wadh was calculated using the phantom-wall approach, and Wimm was calculated by simply subtracting the surface tension of polymers γL from Wadh. The results showed that Wadh and Wimm were improved by surface modification with low coverage, owing to a good penetration of the polymer. The effect of modifier length on Wadh and Wimm was small. Whereas Wadh increased in the following order: PP < PS < PMMA, Wimm increased as follows: PMMA < PS < PP. Finally, the trend of Wadh and Wimm was organized using the Flory-Huggins interaction parameter χ between the modifier and the polymer. This study demonstrates that the interfacial affinity can be improved by tuning the surface coverage and modifier species depending on the polymer matrix.
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Affiliation(s)
- Takamasa Saito
- Department of Chemical Engineering, Tohoku University, 6-6-07 Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Masaki Kubo
- Department of Chemical Engineering, Tohoku University, 6-6-07 Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Takao Tsukada
- New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Eita Shoji
- Department of Mechanical Systems Engineering, Tohoku University, 6-6-01 Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Gota Kikugawa
- Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Donatas Surblys
- Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Momoji Kubo
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
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3
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Singh D, Poddar P. Scalable Synthesis of Dodecanethiol-Capped Bismuth Nanoparticles by a Solvent-Free Solid-State Grinding Method for Reduction of 4-Nitrophenol to 4-Aminophenol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:11888-11897. [PMID: 37561936 DOI: 10.1021/acs.langmuir.3c01694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
Thiol-capped metal nanoparticles have two constituents: an inorganic metal and an organic molecule as a shell. Both characters are inbuilt in the structure of the metal thiolate. Herein, we have investigated bismuth dodecanethiolate as a precursor for the synthesis of dodecanethiol-capped bismuth nanoparticles (Bi NPs) by a solid-state grinding method. By using sodium borohydride and bismuth dodecanethiolate, crystalline bismuth nanoparticles are synthesized in a solvent-free environment at room temperature (24 ± 4 °C). Bi NPs are tested for catalytic activity by reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with an excess of NaBH4. Dodecanethiol-capped bismuth nanoparticles exhibit an efficient reduction of 4-NP to 4-AP within 12 min. Additionally, these nanoparticles remain catalytically active for up to three cycles.
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Affiliation(s)
- Dinesh Singh
- Physical & Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Sector 19, Kamla Nehru Nagar, Ghaziabad, Uttar Pradesh 201002, India
| | - Pankaj Poddar
- Physical & Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Sector 19, Kamla Nehru Nagar, Ghaziabad, Uttar Pradesh 201002, India
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4
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Park S, Kim E, Choi Y, Jang J, Kwak K, Cho M, Yoon HJ. Thermoresponse of Odd-Even Effect in n-Alkanethiolate Self-Assembled Monolayers on Gold Substrates. Chemistry 2023; 29:e202203536. [PMID: 36548089 DOI: 10.1002/chem.202203536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/22/2022] [Accepted: 12/22/2022] [Indexed: 12/24/2022]
Abstract
This study examines thermoresponse of odd-even effect in self-assembled monolayers (SAMs) of n-alkanethiolates (SCn , n=3-18) formed on template-stripped gold (AuTS ) using macro- and microscopic analytical techniques, contact angle goniometry (CAG) and vibrational sum frequency generation (VSFG) spectroscopy, respectively. Both CAG and VSFG analyses showed that the odd-even effect in liquid-like SAMs (n=3-9) disappeared upon heating at 50-70 °C, indicating that the heating led to increased structural disorder regardless of odd and even carbon numbers. In contrast, the opposite thermoresponse was observed for odd and even SCn molecules in wax- and solid-like SAMs (n=10-18). Namely, temperature-dependent orientational change of terminal CH3 relative to the surface normal was opposite for the odd and even molecules, thereby leading to mitigated odd-even effect. Our work offers important insights into thermoresponse of supramolecular structure in condensed organic matter.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea
| | - Eunchan Kim
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul, 02841, Republic of Korea
| | - Youngjin Choi
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul, 02841, Republic of Korea
| | - Jiung Jang
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea
| | - Kyungwon Kwak
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul, 02841, Republic of Korea
| | - Minhaeng Cho
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul, 02841, Republic of Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea
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5
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Thennakoon CA, Rajapakshe RBSD, Malikaramage AU, Gamini Rajapakse RM. Factors Affecting the Hydrophobic Property of Stearic Acid Self-Assembled on the TiO 2 Substrate. ACS OMEGA 2022; 7:48184-48191. [PMID: 36591204 PMCID: PMC9798506 DOI: 10.1021/acsomega.2c06217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
The self-assembled monolayer (SAM) on inorganic metal oxides is highly applicable in making different kinds of surface phenomena such as superhydrophobicity, functional group-modified surfaces, corrosion resistance, and so on. The formation of stearic acid SAMs on the TiO2 substrate depends on a few factors, and the cleanability of the substrate surface can be considered as the critical criterion for the formation of the SAM layer. The solvent, concentration of the adsorbate, immersion time, and temperature can be identified as other factors that are crucial for growing a uniform and highly dense monolayer. SAM layers always build up spontaneously on a suitable substrate, but the growth rate and arrangement can be changed by varying the external factors. These factors highly affect the chemisorption of stearic acid molecules onto the TiO2 substrate and building a well-ordered pattern on the surface without defects. This study mainly focuses on identifying the critical conditions of the external factors in obtaining a high-performance superhydrophobic surface. The crystal structure and surface morphologies of the substrate materials are characterized by powder X-ray diffraction and scanning electron microscopy, and the surface wettability is characterized by contact angle measurements. High superhydrophobicity is observed at the optimum conditions of the factors. Ethanol is used as the solvent; the temperature is about 40 °C; and 600 ppm of stearic acid is the critical concentration in obtaining a superhydrophobic surface with 100 min of immersion time, while the contact angle is 151.38°. Simultaneously, if the concentration is 1000 ppm and the immersion time is 120 min, the surface shows high superhydrophobicity with a contact angle of 162.06°. These critical conditions are found to be adequate for building well-ordered stearic acid SAMs on the TiO2 substrate.
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Affiliation(s)
- Charith Anuruddha Thennakoon
- Department
of Chemistry, Faculty of Science, University
of Peradeniya, Peradeniya 20400 Sri Lanka
- Postgraduate
Institute of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
| | - R. B. S. Dilan Rajapakshe
- Department
of Chemistry, Faculty of Science, University
of Peradeniya, Peradeniya 20400 Sri Lanka
- Postgraduate
Institute of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
| | - Asitha Udayanga Malikaramage
- Department
of Chemistry, Faculty of Science, University
of Peradeniya, Peradeniya 20400 Sri Lanka
- Postgraduate
Institute of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
| | - Rajapakse Mudiyanselage Gamini Rajapakse
- Department
of Chemistry, Faculty of Science, University
of Peradeniya, Peradeniya 20400 Sri Lanka
- Postgraduate
Institute of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
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6
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Molecular ensemble junctions with inter-molecular quantum interference. Nat Commun 2022; 13:4742. [PMID: 35961982 PMCID: PMC9374774 DOI: 10.1038/s41467-022-32476-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 08/01/2022] [Indexed: 11/08/2022] Open
Abstract
We report of a high yield method to form nanopore molecular ensembles junctions containing ~40,000 molecules, in which the semimetal bismuth (Bi) is a top contact. Conductance histograms of these junctions are double-peaked (bi-modal), a behavior that is typical for single molecule junctions but not expected for junctions with thousands of molecules. This unique observation is shown to result from a new form of quantum interference that is inter-molecular in nature, which occurs in these junctions since the very long coherence length of the electrons in Bi enables them to probe large ensembles of molecules while tunneling through the junctions. Under such conditions, each molecule within the ensembles becomes an interference path that modifies via its tunneling phase the electronic structure of the entire junction. This new form of quantum interference holds a great promise for robust novel conductance effects in practical molecular junctions. Quantum interference effect in the conductance of single molecule junctions has been attracting intensive interest in recent years. Here, Li and Selzer show the presence of intermolecular quantum interference over 40,000 molecules in a molecular ensemble junction with bismuth as the top electrode.
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7
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Kumakli H, Hoque A, White RJ. Observing Real-Time Formation of Self-Assembled Monolayers on Polycrystalline Gold Surfaces with Scanning Electrochemical Cell Microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:9148-9156. [PMID: 35850518 DOI: 10.1021/acs.langmuir.2c00667] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Self-assembled monolayers (SAMs) of alkanethiols on gold have become a central focus of controllable surface chemistry because they can be easily formed from the solution phase and characterized using various techniques. Understanding the formation processes occurring at a nanoscale level is crucial to form defect-free SAMs for tailored applications in bio- and nanotechnology. Although many reports study and characterize SAMs after they are formed on gold surfaces, typical methods have not extensively studied the SAM formation process at the nanoscale. This paper focuses on the formation of defect-free SAMs and elucidates the formation mechanism occurring at the nanoscale level during the formation process. Exploiting the strength of scanning electrochemical cell microscopy, we monitored SAM formation via a soluble redox reporter on a polycrystalline gold foil using voltammetric and amperometric techniques. We formed SAMs by varying the concentration of 3-mercapto-1-propanol [HS(CH2)3OH], 6-mercapto-1-hexanol [HS(CH2)6OH], and 9-mercapto-1-nonanol [HS(CH2)9OH] to determine the effects of the thiol chain length, concentration, and location on the substrate (grain boundaries) on monolayer formation. We observed real-time changes in the quasisteady-state current of our redox reporter during the self-assembly process. Importantly, we formed defect-free SAMs at the nanoscale level using different concentrations of HS(CH2)6OH and HS(CH2)9OH and found that SAM formation at the nanoscale is concentration-dependent and varies when at a boundary between two crystal grains.
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Affiliation(s)
- Hope Kumakli
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - Abdul Hoque
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
| | - Ryan J White
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
- Department of Electrical Engineering, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States
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8
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Pensa E, Azofra LM, Salvarezza RC, Carro P. Effect of Ligands on the Stability of Gold Nanoclusters. J Phys Chem Lett 2022; 13:6475-6480. [PMID: 35816759 DOI: 10.1021/acs.jpclett.2c01616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Gold nanoclusters (AuNCs) are atomic architectures that can be precisely tailored for catalytic applications. In this work, we studied two benchmark AuNCs, Au25(SR)18 and Au144(SR)60, covered by aromatic and aliphatic ligands to envision how the 3D structure of the ligand impacts the stability of the nanomaterial. Surprisingly, we found that increasing the alkanethiol length has a poor or null effect on the stability of the AuNCs, a trend opposite to that on Au(111) surfaces. When considering the aromatic or aliphatic nature, the AuNC stability follows the same trend as on Au(111): the thermodynamical stability is dictated by the ligand density rather than its chemical nature, where the aliphatic ligand imparts more stability than the aromatic one. Our findings provide a tool to predict how an ultrasmall gold core can interact with the environment, substrate, and themselves according to the stability of its protecting ligand shell.
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Affiliation(s)
- Evangelina Pensa
- Fakultät für Physik, Ludwig-Maximilians-Universität München, 80539 Munich, Germany
| | - Luis Miguel Azofra
- Instituto de Estudios Ambientales y Recursos Naturales (i-UNAT), Universidad de Las Palmas de Gran Canaria (ULPGC), Campus de Tafira, 35017 Las Palmas de Gran Canaria, Spain
| | - Roberto C Salvarezza
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET, La Plata 1900, Argentina
| | - Pilar Carro
- Área de Química Física, Departamento de Química, Facultad de Ciencias, Universidad de La Laguna, Instituto de Materiales y Nanotecnología, 38200 La Laguna, Spain
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9
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Du C, Wang Z, Chen J, Martin A, Raturi D, Thuo M. Role of Nanoscale Roughness and Polarity in Odd–Even Effect of Self‐Assembled Monolayers. Angew Chem Int Ed Engl 2022; 61:e202205251. [PMID: 35580255 PMCID: PMC9400998 DOI: 10.1002/anie.202205251] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Indexed: 11/13/2022]
Abstract
The dependency of substrate roughness on wetting properties of self‐assembled monolayers (SAMs) has been studied extensively, but most previous studies used limited selection of probing liquid and range of surface roughness. These studies disregarded the limit to observation of sub‐nanometer odd–even parity effect, hence are inconclusive. In this work we report the role of solvent polarity on the roughness‐dependency of wetting behavior of SAMs by studying static con‐tact angle of a variety of probing liquids, with different polarities, on SAMs formed on Ag‐based substrate with different surface morphology. By overlapping the roughness ranges with previous studies on Au, the limitation of surface roughness (RMS=1 nm) to observation of the odd–even effect using water as probing liquid was confirmed, but other probing liquid yielded different roughness‐dependent behaviors, with more polar solvent showing more roughness‐dependent behavior. Based on these observations, we concluded that there exists a phase‐transition like behavior in SAMs due to substrate roughness and molecule chain length, but whose determination is dependent on the probing liquid.
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Affiliation(s)
- Chuanshen Du
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Zhengjia Wang
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Jiahao Chen
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
- Micro-electronic research center Iowa State University 133 Applied Sciences Complex, 1925 Scholl Road Ames IA 50011 USA
| | - Andrew Martin
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Dhruv Raturi
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Martin Thuo
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
- Micro-electronic research center Iowa State University 133 Applied Sciences Complex, 1925 Scholl Road Ames IA 50011 USA
- Biopolymer and Biocomposites Research Team Center for Bioplastics and Biocomposites Iowa State University 1041 Food Sciences Building Ames IA 50011 USA
- Department of Electrical Engineering Iowa State University 2215 Coover Hall Ames IA 50011 USA
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10
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Yadav HOS, Kuo AT, Urata S, Funahashi K, Imamura Y, Shinoda W. Adsorption characteristics of peptides on ω-functionalized self-assembled monolayers: a molecular dynamics study. Phys Chem Chem Phys 2022; 24:14805-14815. [PMID: 35695085 DOI: 10.1039/d2cp01348g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecular dynamics simulations were employed to investigate the adsorption behavior of a variety of amino-acid side-chain analogs (SCAs) and a β-hairpin (HP7) peptide on a series of liquid-like self-assembled monolayers (SAMs) with terminal functional groups of -OH, -OCH3, -CH3, and -CF3. The relationships between the adsorption free energy of the SCAs and the interfacial properties of water on the SAMs were examined to determine the acute predictors of protein adsorption on the SAM surfaces. The structural changes of HP7 on the SAM surfaces were also investigated to understand the relationship between the surface nature and protein denaturation. It was found that the adsorption free energy of the SCAs was linearly related to the surface hydrophobicity, which was computed as the free energy of cavity formation near the SAM-water interfaces. In addition, the hydrophobic -CH3 and -CF3 SAMs produced substantial conformational changes in HP7 because of the strong hydrophobic attractions to the nonpolar side chains. The hydrophilic surface terminated by -OH also promoted structural changes in HP7 resulting from the formation of hydrogen bonds between the hydrophilic tail and HP7. Consequently, the moderate amphiphilic surface terminated by -OCH3 avoided the denaturation of HP7 most efficiently, thus improving the biocompatibility of the surface. In conclusion, these results provide a deep understanding of protein adsorption for a wide range of polymeric surfaces, and they can potentially aid the design of appropriate biocompatible coatings for medical applications.
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Affiliation(s)
- Hari O S Yadav
- Department of Materials Chemistry, Nagoya University, Nagoya 464-8603, Japan
| | - An-Tsung Kuo
- Materials Integration Laboratories, AGC Inc., Yokohama, Kanagawa, 230-0045, Japan
| | - Shingo Urata
- Planning Division, AGC Inc., Yokohama, Kanagawa, 230-0045, Japan
| | - Kosuke Funahashi
- Innovative Technology Laboratories, AGC Inc., Yokohama, Kanagawa, 230-0045, Japan
| | - Yutaka Imamura
- Innovative Technology Laboratories, AGC Inc., Yokohama, Kanagawa, 230-0045, Japan
| | - Wataru Shinoda
- Department of Materials Chemistry, Nagoya University, Nagoya 464-8603, Japan.,Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan. .,Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan
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11
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Du C, Wang Z, Chen J, Martin A, Raturi D, Thuo M. Role of Nanoscale Roughness and Polarity in Odd–Even Effect of Self‐Assembled Monolayers. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Chuanshen Du
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Zhengjia Wang
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Jiahao Chen
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
- Micro-electronic research center Iowa State University 133 Applied Sciences Complex, 1925 Scholl Road Ames IA 50011 USA
| | - Andrew Martin
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Dhruv Raturi
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
| | - Martin Thuo
- Department of Materials Science and Engineering Iowa State University 2220 Hoover Hall Ames IA 50011 USA
- Micro-electronic research center Iowa State University 133 Applied Sciences Complex, 1925 Scholl Road Ames IA 50011 USA
- Biopolymer and Biocomposites Research Team Center for Bioplastics and Biocomposites Iowa State University 1041 Food Sciences Building Ames IA 50011 USA
- Department of Electrical Engineering Iowa State University 2215 Coover Hall Ames IA 50011 USA
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12
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Khadka K, Ferguson GS. Does the Roll-off Angle Depend on Work of Adhesion? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:4820-4825. [PMID: 35412835 DOI: 10.1021/acs.langmuir.1c03425] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The roll-off angle of hexadecane droplets was measured on a family of nearly ideal surfaces having similar structures but different interfacial free energies. The variation in interfacial energy was reflected in the contact angles of hexadecane, which provide a measure of the work of adhesion. The hysteresis in the contact angle on these surfaces was low and approximately constant, thereby approximately removing it as a variable and allowing for an assessment of any dependence of the roll-off angle on work of adhesion directly. The results revealed no such dependence, consistent with the descriptions of early researchers in this area.
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Affiliation(s)
- Kiran Khadka
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Gregory S Ferguson
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
- Department of Materials Science & Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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13
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Weiand E, Ewen JP, Koenig PH, Roiter Y, Page SH, Angioletti-Uberti S, Dini D. Coarse-grained molecular models of the surface of hair. SOFT MATTER 2022; 18:1779-1792. [PMID: 35112700 DOI: 10.1039/d1sm01720a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We present a coarse-grained molecular model of the surface of human hair, which consists of a supported lipid monolayer, in the MARTINI framework. Using coarse-grained molecular dynamics (MD) simulations, we identify a lipid grafting distance that yields a monolayer thickness consistent with both atomistic MD simulations and experimental measurements of the hair surface. Coarse-grained models for fully-functionalised, partially damaged, and fully damaged hair surfaces are created by randomly replacing neutral thioesters with anionic sulfonate groups. This mimics the progressive removal of fatty acids from the hair surface by bleaching and leads to chemically heterogeneous surfaces. Using molecular dynamics (MD) simulations, we study the island structures formed by the lipid monolayers at different degrees of damage in vacuum and in the presence of polar (water) and non-polar (n-hexadecane) solvents. We also use MD simulations to compare the wetting behaviour of water and n-hexadecane droplets on the model surfaces through contact angle measurements, which are compared to experiments using virgin and bleached hair. The model surfaces capture the experimentally-observed transition of the hair surface from hydrophobic (and oleophilic) to hydrophilic (and oleophobic) as the level of bleaching damage increases. By selecting surfaces with specific damage ratios, we obtain contact angles from the MD simulations that are in good agreement with experiments for both solvents on virgin and bleached human hairs. To negate the possible effects of microscale curvature and roughness of real hairs on wetting, we also conduct additional experiments using biomimetic surfaces that are co-functionalised with fatty acids and sulfonate groups. In both the MD simulations and experiments, the cosine of the water contact angle increases linearly with the sulfonate group surface coverage with a similar slope. We expect that the proposed systems will be useful for future molecular dynamics simulations of the adsorption and tribological behaviour of hair, as well as other chemically heterogeneous surfaces.
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Affiliation(s)
- Erik Weiand
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - James P Ewen
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - Peter H Koenig
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Yuri Roiter
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Steven H Page
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Stefano Angioletti-Uberti
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Department of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
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14
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Carlson S, Becker M, Brünig FN, Ataka K, Cruz R, Yu L, Tang P, Kanduč M, Haag R, Heberle J, Makki H, Netz RR. Hydrophobicity of Self-Assembled Monolayers of Alkanes: Fluorination, Density, Roughness, and Lennard-Jones Cutoffs. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:13846-13858. [PMID: 34787431 DOI: 10.1021/acs.langmuir.1c02187] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The interplay of fluorination and structure of alkane self-assembled monolayers and how these affect hydrophobicity are explored via molecular dynamics simulations, contact angle goniometry, and surface-enhanced infrared absorption spectroscopy. Wetting coefficients are found to grow linearly in the monolayer density for both alkane and perfluoroalkane monolayers. The larger contact angles of monolayers of perfluorinated alkanes are shown to be primarily caused by their larger molecular volume, which leads to a larger nearest-neighbor grafting distance and smaller tilt angle. Increasing the Lennard-Jones force cutoff in simulations is found to increase hydrophilicity. Specifically, wetting coefficients scale like the inverse square of the cutoff, and when extrapolated to the infinite cutoff limit, they yield contact angles that compare favorably to experimental values. Nanoscale roughness is also found to reliably increase monolayer hydrophobicity, mostly via the reduction of the entropic part of the work of adhesion. Analysis of depletion lengths shows that droplets on nanorough surfaces partially penetrate the surface, intermediate between Wenzel and Cassie-Baxter states.
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Affiliation(s)
- Shane Carlson
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Maximilian Becker
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Florian N Brünig
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Kenichi Ataka
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Rubén Cruz
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Leixiao Yu
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Peng Tang
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Matej Kanduč
- Department of Theoretical Physics, Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia
| | - Rainer Haag
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Joachim Heberle
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Hesam Makki
- Polymer and Color Engineering, Amirkabir University of Technology, 424 Hafez Ave, Tehran 15875-4413, Iran
| | - Roland R Netz
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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15
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Grabarek A, Walczak Ł, Cyganik P. Odd-Even Effect in Peptide SAMs-Competition of Secondary Structure and Molecule-Substrate Interaction. J Phys Chem B 2021; 125:10964-10971. [PMID: 34554757 PMCID: PMC8503877 DOI: 10.1021/acs.jpcb.1c06625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Peptide-based self-assembled
monolayers (SAMs) are well known to
be crucial for biocompatible surface formation on inorganic substrates
applied for implants, biosensors, or tissue engineering. Moreover,
recently these bioinspired nanostructures are also considered
particularly interesting for molecular electronics applications due
to their surprisingly high conductance and thickness-independent capacitance,
which make them a very promising element of organic field-effect transistors
(OFETs). Our structural analysis conducted for a series of prototypic
homooligopeptides based on glycine (Gly) with cysteine (Cys) as a
substrate bonding group chemisorbed on Au and Ag metal substrates
(GlynCys/Au(Ag), n =
1–9) exhibits the formation by these monolayers secondary structure
close to β-sheet conformation with pronounced odd–even structural effect strongly affecting packing density and conformation
of molecules in the monolayer, which depend on the length of molecules
and the type of metal substrate. Our experiments indicate that the
origin of these structural effects is related to the either cooperative
or competitive relationship between the type of secondary structure
formed by these molecules and the directional character of their chemical
bonding to the metal substrate. The current analysis opens up the
opportunity for the rational design of these biologically inspired
nanostructures, which is crucial both for mentioned biological and
electronic applications.
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Affiliation(s)
- Agnieszka Grabarek
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Krakow, Poland
| | - Łukasz Walczak
- Science & Research Division, PREVAC sp. z o.o., Raciborska 61, 44-362 Rogow, Poland
| | - Piotr Cyganik
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Krakow, Poland
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16
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Du C, Norris SR, Thakur A, Chen J, VanVeller B, Thuo M. Molecular Conformation in Charge Tunneling across Large-Area Junctions. J Am Chem Soc 2021; 143:13878-13886. [PMID: 34415163 DOI: 10.1021/jacs.1c06622] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Self-assembled monolayers are predicated on thermodynamic equilibrium; hence, their properties project accessible relaxation pathways. Herein, we demonstrate that charge tunneling correlates with conformational degrees of freedom(s). Results from open chain and cyclic head groups show that, as expected, distribution in tunneling data correlates with the orientation of the head group, akin to the odd-even effect and more importantly the degree of conformational freedom, but fluctuates with applied bias. Trends in nature of distributions in current density illuminate the need for higher statistical moments in understanding these rather dynamic systems. We employ skewness, kurtosis, and estimation plots to show that the conformational degree of freedom in the head group significantly amplifies the odd-even effect and may lead to enhanced or perturbed tunneling based on whether the head group is on an odd- or even-parity spacer.
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Affiliation(s)
- Chuanshen Du
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, Iowa 50011 United States
| | - Sean R Norris
- Department of Chemistry, Iowa State University, 3126 Hach Hall, 2438 Pammel Drive, Ames, Iowa 50011-3111, United States
| | - Abhishek Thakur
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Jiahao Chen
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, Iowa 50011 United States.,Micro-Electronic Research Center, Iowa State University, 133 Applied Sciences Complex I, 1925 Scholl Road, Ames, Iowa 50011, United States
| | - Brett VanVeller
- Department of Chemistry, Iowa State University, 3126 Hach Hall, 2438 Pammel Drive, Ames, Iowa 50011-3111, United States
| | - Martin Thuo
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, Iowa 50011 United States.,Micro-Electronic Research Center, Iowa State University, 133 Applied Sciences Complex I, 1925 Scholl Road, Ames, Iowa 50011, United States.,Biopolymer and Biocomposites Research Team, Center for Bioplastics and Biocomposites Iowa State University, 1041 Food Sciences Building, Ames, Iowa 50011, United States
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17
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Cheng HW, Yan S, Shang G, Wang S, Zhong CJ. Strain sensors fabricated by surface assembly of nanoparticles. Biosens Bioelectron 2021; 186:113268. [PMID: 33971524 DOI: 10.1016/j.bios.2021.113268] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/05/2021] [Accepted: 04/16/2021] [Indexed: 01/02/2023]
Abstract
Harnessing interparticle spatial properties of surface assembly of nanoparticles (SAN) on flexible substrates is a rapidly emerging front of research in the design and fabrication of highly-sensitive strain sensors. It has recently shown promising potentials for applications in wearable sensors and skin electronics. SANs feature 3D structural tunability of the interparticle spatial properties at both molecular and nanoscale levels, which is transformative for the design of intriguing strain sensors. This review will present a comprehensive overview of the recent research development in exploring SAN-structured strain sensors for wearable applications. It starts from the basic principle governing the strain sensing characteristics of SANs on flexible substrates in terms of thermally-activated interparticle electron tunneling and conductive percolation. This discussion is followed by descriptions of the fabrication of the sensors and the proof-of-concept demonstrations of the strain sensing characteristics. The nanoparticles in the SANs are controllable in terms of size, shape, and composition, whereas the interparticle molecules enable the tunability of the electrical properties in terms of interparticle spatial properties. The design of SAN-derived strain sensors is further highlighted by describing several recent examples in the explorations of their applications in wearable biosensor and bioelectronics. Fundamental understanding of the role of interparticle spatial properties within SANs at both molecular and device levels is the focal point. The future direction of the SAN-derived wearable sensors will also be discussed, shining lights on a potential paradigm shift in materials design in exploring the emerging opportunities in wearable sensors and skin electronics.
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Affiliation(s)
- Han-Wen Cheng
- School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai, 201418, China; Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA.
| | - Shan Yan
- Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Guojun Shang
- Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Shan Wang
- Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Chuan-Jian Zhong
- Department of Chemistry, State University of New York at Binghamton, Binghamton, NY, 13902, USA.
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18
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Kong GD, Song H, Yoon S, Kang H, Chang R, Yoon HJ. Interstitially Mixed Self-Assembled Monolayers Enhance Electrical Stability of Molecular Junctions. NANO LETTERS 2021; 21:3162-3169. [PMID: 33797252 DOI: 10.1021/acs.nanolett.1c00406] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Electrical breakdown is a critical problem in electronics. In molecular electronics, it becomes more problematic because ultrathin molecular monolayers have delicate and defective structures and exhibit intrinsically low breakdown voltages, which limit device performances. Here, we show that interstitially mixed self-assembled monolayers (imSAMs) remarkably enhance electrical stability of molecular-scale electronic devices without deteriorating function and reliability. The SAM of the sterically bulky matrix (SC11BIPY rectifier) molecule is diluted with a skinny reinforcement (SCn) molecule via the new approach, so-called repeated surface exchange of molecules (ReSEM). Combined experiments and simulations reveal that the ReSEM yields imSAMs wherein interstices between the matrix molecules are filled with the reinforcement molecules and leads to significantly enhanced breakdown voltage inaccessible by traditional pure or mixed SAMs. Thanks to this, bias-driven disappearance and inversion of rectification is unprecedentedly observed. Our work may help to overcome the shortcoming of SAM's instability and expand the functionalities.
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Affiliation(s)
- Gyu Don Kong
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyunsun Song
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Seungmin Yoon
- Department of Chemistry, Kwangwoon University, Seoul 01897, Korea
| | - Hungu Kang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Rakwoo Chang
- Department of Applied Chemistry, University of Seoul, Seoul 02543, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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19
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Martin A, Chang BS, Pauls AM, Du C, Thuo M. Stabilization of Undercooled Metals via Passivating Oxide Layers. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202013489] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Andrew Martin
- Department of Materials Science and Engineering Iowa State University Ames IA 50010 USA
| | - Boyce S. Chang
- Department of Materials Science and Engineering Iowa State University Ames IA 50010 USA
| | - Alana M. Pauls
- Department of Materials Science and Engineering Iowa State University Ames IA 50010 USA
| | - Chuanshen Du
- Department of Materials Science and Engineering Iowa State University Ames IA 50010 USA
| | - Martin Thuo
- Department of Materials Science and Engineering Iowa State University Ames IA 50010 USA
- Department of Electrical and Computer Engineering Iowa State University Ames IA 50010 USA
- Micro-Electronics Research Centre Ames IA 50014 USA
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20
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Martin A, Chang BS, Pauls AM, Du C, Thuo M. Stabilization of Undercooled Metals via Passivating Oxide Layers. Angew Chem Int Ed Engl 2021; 60:5928-5935. [PMID: 33381886 DOI: 10.1002/anie.202013489] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 12/10/2020] [Indexed: 11/08/2022]
Abstract
Undercooling metals relies on frustration of liquid-solid transition mainly by an increase in activation energy. Passivating oxide layers are a way to isolate the core from heterogenous nucleants (physical barrier) while also raising the activation energy (thermodynamic/kinetic barrier) needed for solidification. The latter is due to composition gradients (speciation) that establishes a sharp chemical potential gradient across the thin (0.7-5 nm) oxide shell, slowing homogeneous nucleation. When this speciation is properly tuned, the oxide layer presents a previously unaccounted for interfacial tension in the overall energy landscape of the relaxing material. We demonstrate that 1) the integrity of the passivation oxide is critical in stabilizing undercooled particle, a key tenet in developing heat-free solders, 2) inductive effects play a critical role in undercooling, and 3) the magnitude of the influence of the passivating oxide can be larger than size effects in undercooling.
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Affiliation(s)
- Andrew Martin
- Department of Materials Science and Engineering, Iowa State University, Ames, IA, 50010, USA
| | - Boyce S Chang
- Department of Materials Science and Engineering, Iowa State University, Ames, IA, 50010, USA
| | - Alana M Pauls
- Department of Materials Science and Engineering, Iowa State University, Ames, IA, 50010, USA
| | - Chuanshen Du
- Department of Materials Science and Engineering, Iowa State University, Ames, IA, 50010, USA
| | - Martin Thuo
- Department of Materials Science and Engineering, Iowa State University, Ames, IA, 50010, USA.,Department of Electrical and Computer Engineering, Iowa State University, Ames, IA, 50010, USA.,Micro-Electronics Research Centre, Ames, IA, 50014, USA
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21
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Belding L, Root SE, Li Y, Park J, Baghbanzadeh M, Rojas E, Pieters PF, Yoon HJ, Whitesides GM. Conformation, and Charge Tunneling through Molecules in SAMs. J Am Chem Soc 2021; 143:3481-3493. [DOI: 10.1021/jacs.0c12571] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Lee Belding
- Department of Chemistry and Chemical Biology, Harvard University 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Samuel E. Root
- Department of Chemistry and Chemical Biology, Harvard University 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Yuan Li
- Department of Chemistry and Chemical Biology, Harvard University 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Junwoo Park
- Department of Chemistry and Chemical Biology, Harvard University 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Mostafa Baghbanzadeh
- Department of Chemistry and Chemical Biology, Harvard University 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Edwin Rojas
- Department of Chemistry and Chemical Biology, Harvard University 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Priscilla F. Pieters
- Department of Chemistry and Chemical Biology, Harvard University 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - George M. Whitesides
- Department of Chemistry and Chemical Biology, Harvard University 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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22
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Han Y, Maglione MS, Diez Cabanes V, Casado-Montenegro J, Yu X, Karuppannan SK, Zhang Z, Crivillers N, Mas-Torrent M, Rovira C, Cornil J, Veciana J, Nijhuis CA. Reversal of the Direction of Rectification Induced by Fermi Level Pinning at Molecule-Electrode Interfaces in Redox-Active Tunneling Junctions. ACS APPLIED MATERIALS & INTERFACES 2020; 12:55044-55055. [PMID: 33237732 DOI: 10.1021/acsami.0c15435] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Control over the energy level alignment in molecular junctions is notoriously difficult, making it challenging to control basic electronic functions such as the direction of rectification. Therefore, alternative approaches to control electronic functions in molecular junctions are needed. This paper describes switching of the direction of rectification by changing the bottom electrode material M = Ag, Au, or Pt in M-S(CH2)11S-BTTF//EGaIn junctions based on self-assembled monolayers incorporating benzotetrathiafulvalene (BTTF) with EGaIn (eutectic alloy of Ga and In) as the top electrode. The stability of the junctions is determined by the choice of the bottom electrode, which, in turn, determines the maximum applied bias window, and the mechanism of rectification is dominated by the energy levels centered on the BTTF units. The energy level alignments of the three junctions are similar because of Fermi level pinning induced by charge transfer at the metal-thiolate interface and by a varying degree of additional charge transfer between BTTF and the metal. Density functional theory calculations show that the amount of electron transfer from M to the lowest unoccupied molecular orbital (LUMO) of BTTF follows the order Ag > Au > Pt. Junctions with Ag electrodes are the least stable and can only withstand an applied bias of ±1.0 V. As a result, no molecular orbitals can fall in the applied bias window, and the junctions do not rectify. The junction stability increases for M = Au, and the highest occupied molecular orbital (HOMO) dominates charge transport at a positive bias resulting in a positive rectification ratio of 83 at ±1.5 V. The junctions are very stable for M = Pt, but now the LUMO dominates charge transport at a negative bias resulting in a negative rectification ratio of 912 at ±2.5 V. Thus, the limitations of Fermi level pinning can be bypassed by a judicious choice of the bottom electrode material, making it possible to access selectively HOMO- or LUMO-based charge transport and, as shown here, associated reversal of rectification.
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Affiliation(s)
- Yingmei Han
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Maria Serena Maglione
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus de la UAB, Bellaterra 08193, Spain
| | - Valentin Diez Cabanes
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, Mons 7000, Belgium
| | - Javier Casado-Montenegro
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus de la UAB, Bellaterra 08193, Spain
| | - Xiaojiang Yu
- Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore
| | - Senthil Kumar Karuppannan
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Ziyu Zhang
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Núria Crivillers
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus de la UAB, Bellaterra 08193, Spain
| | - Marta Mas-Torrent
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus de la UAB, Bellaterra 08193, Spain
| | - Concepció Rovira
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus de la UAB, Bellaterra 08193, Spain
| | - Jérôme Cornil
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, Mons 7000, Belgium
| | - Jaume Veciana
- Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus de la UAB, Bellaterra 08193, Spain
| | - Christian A Nijhuis
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials and Graphene Research Center, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
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23
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Kumar S, Soni S, Danowski W, van Beek CLF, Feringa BL, Rudolf P, Chiechi RC. Correlating the Influence of Disulfides in Monolayers across Photoelectron Spectroscopy Wettability and Tunneling Charge-Transport. J Am Chem Soc 2020; 142:15075-15083. [PMID: 32786759 PMCID: PMC7472521 DOI: 10.1021/jacs.0c06508] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Indexed: 12/12/2022]
Abstract
Despite their ubiquity, self-assembled monolayers (SAMs) of thiols on coinage metals are difficult to study and are still not completely understood, particularly with respect to the nature of thiol-metal bonding. Recent advances in molecular electronics have highlighted this deficiency due to the sensitivity of tunneling charge-transport to the subtle differences in the overall composition of SAMs and the chemistry of their attachment to surfaces. These advances have also challenged assumptions about the spontaneous formation of covalent thiol-metal bonds. This paper describes a series of experiments that correlate changes in the physical properties of SAMs to photoelectron spectroscopy to unambiguously assign binding energies of noncovalent interactions to physisorbed disulfides. These disulfides can be converted to covalent metal-thiolate bonds by exposure to free thiols, leading to the remarkable observation of the total loss and recovery of length-dependent tunneling charge-transport. The identification and assignment of physisorbed disulfides solve a long-standing mystery and reveal new, dynamic properties in SAMs of thiols.
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Affiliation(s)
- Sumit Kumar
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Saurabh Soni
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Wojciech Danowski
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Carlijn L. F. van Beek
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Ben L. Feringa
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Petra Rudolf
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Ryan C. Chiechi
- Stratingh
Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike
Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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24
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Dionne ER, Ben Amara F, Badia A. An electrochemical immittance analysis of the dielectric properties of self-assembled monolayers. CAN J CHEM 2020. [DOI: 10.1139/cjc-2020-0005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The ability of organic self-assembled monolayers (SAMs) to act as insulating barriers to electron transfer, ion transport, or molecular diffusion is critical to their application in a variety of technologies. The use of appropriate analytical tools to characterize the dielectric properties of these molecular thin films is important for the control of structural defects and establishing structure–property relations. In this context, we analyze the ionic permeability and dielectric response of SAMs formed from a homologous series of n-alkanethiolates (CH3(CH2)nS, where n = 9, 11, 13, 15, 17, and 19) on gold using the immittance quantities of the complex impedance, capacitance, and permittivity available from the same electrochemical impedance spectroscopy (EIS) measurement. The most sensitive parameters and frequency range for characterizing the capacitive behavior and assessing the ion-blocking quality of the SAMs under non-Faradaic conditions are identified. We also investigate the effect of chain length on the interfacial capacitance and dielectric constant of ionic insulating SAMs. The advantages of the capacitance quantity and related permittivity data over traditional impedance representations and equivalent electric circuit modeling are discussed.
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Affiliation(s)
- Eric R. Dionne
- Département de chimie, Université de Montréal, Montréal, QC H3C 3J7 Canada
- Département de chimie, Université de Montréal, Montréal, QC H3C 3J7 Canada
| | - Fadwa Ben Amara
- Département de chimie, Université de Montréal, Montréal, QC H3C 3J7 Canada
- Département de chimie, Université de Montréal, Montréal, QC H3C 3J7 Canada
| | - Antonella Badia
- Département de chimie, Université de Montréal, Montréal, QC H3C 3J7 Canada
- Département de chimie, Université de Montréal, Montréal, QC H3C 3J7 Canada
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Yang W, Vansuch GE, Liu Y, Jin T, Liu Q, Ge A, Sanchez MLK, K Haja D, Adams MWW, Dyer RB, Lian T. Surface-Ligand "Liquid" to "Crystalline" Phase Transition Modulates the Solar H 2 Production Quantum Efficiency of CdS Nanorod/Mediator/Hydrogenase Assemblies. ACS APPLIED MATERIALS & INTERFACES 2020; 12:35614-35625. [PMID: 32662974 DOI: 10.1021/acsami.0c07820] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This study reports how the length of capping ligands on a nanocrystal surface affects its interfacial electron transfer (ET) with surrounding molecular electron acceptors, and consequently, impact the H2 production of a biotic-abiotic hybrid artificial photosynthetic system. Specifically, we study how the H2 production efficiency of a hybrid system, combining CdS nanorods (NRs), [NiFe] hydrogenase, and redox mediators (propyl-bridged 2,2'-bipyridinium, PDQ2+), depends on the alkyl chain length of mercaptocarboxylate ligands on the NR surface. We observe a minor decrease of the quantum yield for H2 production from 54 ± 6 to 43 ± 2% when varying the number of methylene units in the ligands from 2 to 7. In contrast, an abrupt decrease of the yield was observed from 43 ± 2 to 4 ± 1% when further increasing n from 7 to 11. ET studies reveal that the intrinsic ET rates from the NRs to the electron acceptor PDQ2+ are all within 108-109 s-1 regardless of the length of the capping ligands. However, the number of adsorbed PDQ2+ molecules on NR surfaces decreases dramatically when n ≥ 10, with the saturating number changing from 45 ± 5 to 0.3 ± 0.1 for n = 2 and 11, respectively. These results are not consistent with the commonly perceived exponential dependence of ET rates on the ligand length. Instead, they can be explained by the change of the accessibility of NR surfaces to electron acceptors from a disordered "liquid" phase at n < 7 to a more ordered "crystalline" phases at n > ∼7. These results highlight that the order of capping ligands is an important design parameter for further constructing nanocrystal/molecular assemblies in broad nanocrystal-based applications.
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Affiliation(s)
- Wenxing Yang
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
- Department of Chemistry-Ångström Laboratory, Physical Chemistry, Uppsala University, SE-75120 Uppsala, Sweden
| | - Gregory E Vansuch
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
| | - Yawei Liu
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
| | - Tao Jin
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
| | - Qiliang Liu
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
| | - Aimin Ge
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
| | - Monica L K Sanchez
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
| | - Dominik K Haja
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - R Brian Dyer
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
| | - Tianquan Lian
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
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Ben Amara F, Dionne ER, Kassir S, Pellerin C, Badia A. Molecular Origin of the Odd-Even Effect of Macroscopic Properties of n-Alkanethiolate Self-Assembled Monolayers: Bulk or Interface? J Am Chem Soc 2020; 142:13051-13061. [PMID: 32597648 DOI: 10.1021/jacs.0c04288] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Elucidating the influence of the monolayer interface versus bulk on the macroscopic properties (e.g., surface hydrophobicity, charge transport, and electron transfer) of organic self-assembled monolayers (SAMs) chemically anchored to metal surfaces is a challenge. This article reports the characterization of prototypical SAMs of n-alkanethiolates on gold (CH3(CH2)nSAu, n = 6-19) at the macroscopic scale by electrochemical impedance spectroscopy and contact angle goniometry, and at the molecular level, by infrared reflection absorption spectroscopy. The SAM capacitance, dielectric constant, and surface hydrophobicity exhibit dependencies on both the length (n) and parity (nodd or neven) of the polymethylene chain. The peak positions of the CH2 stretching modes indicate a progressive increase in the chain conformational order with increasing n between n = 6 and 16. SAMs of nodd have a greater degree of structural gauche defects than SAMs of neven. The peak intensities and positions of the CH3 stretching modes are chain length independent but show an odd-even alternation of the spatial orientation of the terminal CH3. The correlations between the different data trends establish that the chain length dependencies of the dielectric constant and surface hydrophobicity originate from changes in the polymethylene chain conformation (bulk), while the odd-even variation arises primarily from a difference in the chemical composition of the interface related to the terminal group orientation. These findings provide new physical insights into the structure-property relation of SAMs for the design of ultrathin film dielectrics as well as the understanding of stereostructural effects on the electrical characteristics of tunnel junctions.
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Affiliation(s)
- Fadwa Ben Amara
- Département de chimie, FRQNT Quebec Centre for Advanced Materials, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Eric R Dionne
- Département de chimie, FRQNT Quebec Centre for Advanced Materials, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Sahar Kassir
- Département de chimie, FRQNT Quebec Centre for Advanced Materials, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Christian Pellerin
- Département de chimie, FRQNT Quebec Centre for Advanced Materials, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Antonella Badia
- Département de chimie, FRQNT Quebec Centre for Advanced Materials, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, QC H3C 3J7, Canada
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27
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Zhou H, Wang J, Wang M, Lin S. Competing Dissolution Pathways and Ligand Passivation-Enhanced Interfacial Stability of Hybrid Perovskites with Liquid Water. ACS APPLIED MATERIALS & INTERFACES 2020; 12:23584-23594. [PMID: 32326693 DOI: 10.1021/acsami.0c03532] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Material instability issues, especially moisture degradation in ambient operating environments, limit the practical application of hybrid perovskite in photovoltaic and light-emitting devices. Very recent experiments demonstrate that ligand passivation can effectively improve the surface moisture tolerance of hybrid perovskites. In this work, the interfacial stability of as-synthesized pristine and alkylammonium-passivated methylammonium lead iodide (MAPbI3) with liquid water is systematically investigated using molecular dynamics simulations and reaction kinetics models. Interestingly, the more hydrophilic [PbI2]0 surface is more stable than the less hydrophilic [MAI]0 surface because of the higher polarity of the former surface. Linear alkylammoniums significantly stabilize the [MAI]0 surface with highly reduced (by 1-2 orders of magnitude) dissociation rates of both MA+ and ligands themselves, while branched ligands, surprisingly, lead to higher dissociation rates as the surface coverage increases. Such anomalous behavior is attributed to the aggregation-assisted dissolution of surfactant-like ligands as micelles during the degradation process. Short-chain linear alkylammonium at the full surface coverage is found to be the optimal ligand to stabilize the [MAI]0 surface. This work not only provides fundamental insights into the ionic dissolution pathways and mechanisms of hybrid perovskites in water but also inspires the design of highly stable hybrid perovskites with ligand passivation layers. The computational framework developed here is also transferrable to the investigation of surface passivation chemistry for weak ionic materials in general.
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Affiliation(s)
- Huanhuan Zhou
- Department of Mechanical Engineering, Materials Science and Engineering Program, FAMU-FSU College of Engineering, Florida State University, Tallahassee, Florida 32310, United States
| | - Jingfan Wang
- Department of Mechanical Engineering, Materials Science and Engineering Program, FAMU-FSU College of Engineering, Florida State University, Tallahassee, Florida 32310, United States
| | - Mingchao Wang
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800, Australia
| | - Shangchao Lin
- Institute of Engineering Thermophysics, School of Mechanical and Power Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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28
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Pradeilles JA, Zhong S, Baglyas M, Tarczay G, Butts CP, Myers EL, Aggarwal VK. Odd-even alternations in helical propensity of a homologous series of hydrocarbons. Nat Chem 2020; 12:475-480. [PMID: 32123339 DOI: 10.1038/s41557-020-0429-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 01/24/2020] [Indexed: 11/09/2022]
Abstract
Odd and even homologues of some n-alkane-based systems are known to exhibit notably different trends in solid-state properties; a well-known illustration is the zigzag plot of their melting point versus chain length. Odd-even effects in the solid state often arise from intermolecular interactions that involve fully extended molecules. These effects have also been observed in less condensed phases, such as self-assembled monolayers; however, the origins of these effects in such systems can be difficult to determine. Here we combined NMR and computational analysis to show that all-syn contiguously methyl-substituted hydrocarbons, with chain lengths from C6 to C11, exhibit a dramatic odd-even effect in helical propensity. The even- and odd-numbered hydrocarbons populate regular and less-controlled helical conformations, respectively. This knowledge will guide the design of helical hydrocarbons as rigid scaffolds or as hydrophobic components in soft materials.
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Affiliation(s)
| | - Siying Zhong
- School of Chemistry, University of Bristol, Bristol, UK
| | - Márton Baglyas
- Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, Budapest, Hungary.,MTA-ELTE, Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, Eötvös University, Budapest, Hungary
| | - György Tarczay
- Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, Budapest, Hungary.,MTA-ELTE, Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, Eötvös University, Budapest, Hungary
| | - Craig P Butts
- School of Chemistry, University of Bristol, Bristol, UK.
| | - Eddie L Myers
- School of Chemistry, National University of Ireland Galway, Galway, Ireland.
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Park S, Kang S, Yoon HJ. Power Factor of One Molecule Thick Films and Length Dependence. ACS CENTRAL SCIENCE 2019; 5:1975-1982. [PMID: 31893227 PMCID: PMC6936095 DOI: 10.1021/acscentsci.9b01042] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Indexed: 06/07/2023]
Abstract
There is a rapidly increasing interest in organic thin film thermoelectrics. However, the power factor of one molecule thick organic film, the self-assembled monolayer (SAM), has not yet been determined. This study describes the experimental determination of the power factor in SAMs and its length dependence at an atomic level. As a proof-of-concept, SAMs composed of n-alkanethiolates and oligophenylenethiolates of different lengths are focused. These SAMs were electrically and thermoelectrically characterized on an identical junction platform using a liquid metal top-electrode, allowing the straightforward estimation of the power factor of the monolayers. The results show that the power factor of the alkyl SAMs ranged from 2.0 × 10-8 to 8.0 × 10-12 μW m-1 K-2 and exhibited significant negative length dependence, whereas the conductivity and thermopower of the conjugated SAMs are the two opposing factors that balance the power factor upon an increase in molecular length, exhibiting a maximum power factor of 3.6 × 10-8 μW m-1 K-2. Once correction factors about the ratio of effective contact area to geometrical contact area are considered, the values of power factors can be increased by several orders of magnitude. With a newly derived parametric semiempirical model describing the length dependence of the power factor, it is investigated that one molecule thick films thinner than 10 nm composed of thiophene units can yield power factors rivaling those of famed organic thermoelectric materials based on poly(3,4-ethylenedioxythiophene)/polystyrenesulfonate (PEDOT/PSS) and polyaniline/graphene/double-walled carbon nanotube. Furthermore, how the transition of the transport regime from tunneling to hopping as molecules become long affects power factors is examined.
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30
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Xu X, Makaraviciute A, Kumar S, Wen C, Sjödin M, Abdurakhmanov E, Danielson UH, Nyholm L, Zhang Z. Structural Changes of Mercaptohexanol Self-Assembled Monolayers on Gold and Their Influence on Impedimetric Aptamer Sensors. Anal Chem 2019; 91:14697-14704. [PMID: 31650834 DOI: 10.1021/acs.analchem.9b03946] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Despite a large number of publications describing biosensors based on electrochemical impedance spectroscopy (EIS), little attention has been paid to the stability and reproducibility issues of the sensor interfaces. In this work, the stability and reproducibility of faradaic EIS analyses on the aptamer/mercaptohexanol (MCH) self-assembled monolayer (SAM)-functionalized gold surfaces in ferri- and ferrocyanide solution were systematically evaluated prior to and after the aptamer-probe DNA hybridization. It is shown that the EIS data exhibited significant drift, and this significantly affected the reproducibility of the EIS signal of the hybridization. As a result, no significant difference between the charge transfer resistance (RCT) changes induced by the aptamer-target DNA hybridization and that caused by the drift could be identified. A conditioning of the electrode in the measurement solution for more than 12 h was required to reach a stable RCT baseline prior to the aptamer-probe DNA hybridization. The monitored drift in RCT and double layer capacitance during the conditioning suggests that the MCH SAM on the gold surface reorganized to a thinner but more closely packed layer. We also observed that the hot binding buffer used in the following aptamer-probe DNA hybridization process could induce additional MCH and aptamer reorganization, and thus further drift in RCT. As a result, the RCT change caused by the aptamer-probe DNA hybridization was less than that caused by the hot binding buffer (blank control experiment). Therefore, it is suggested that the use of high temperature in the EIS measurement should be carefully evaluated or avoided. This work provides practical guidelines for the EIS measurements. Moreover, because SAM-functionalized gold electrodes are widely used in biosensors, for example, DNA sensors, an improved understanding of the origin of the observed drift is very important for the development of well-functioning and reproducible biosensors.
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Affiliation(s)
| | | | - Shalen Kumar
- School of Biological Sciences , Victoria University of Wellington , Wellington 6140 , New Zealand.,AuramerBio Limited, Callaghan Innovation Quarter , 69 Seaview Road , Gracefield, Lower Hutt 5010 , New Zealand
| | | | | | - Eldar Abdurakhmanov
- Department of Chemistry-BMC and Science for Life Laboratory , Uppsala University , P.O. Box 576, Uppsala SE-751 23 , Sweden
| | - U Helena Danielson
- Department of Chemistry-BMC and Science for Life Laboratory , Uppsala University , P.O. Box 576, Uppsala SE-751 23 , Sweden
| | - Leif Nyholm
- Department of Chemistry, The Ångström Laboratory , Uppsala University , P.O. Box 538, Uppsala SE-751 21 , Sweden
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31
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Chang BS, Thomas B, Chen J, Tevis ID, Karanja P, Çınar S, Venkatesh A, Rossini AJ, Thuo MM. Ambient synthesis of nanomaterials by in situ heterogeneous metal/ligand reactions. NANOSCALE 2019; 11:14060-14069. [PMID: 31313799 DOI: 10.1039/c9nr05448k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Coordination polymers are ideal synthons in creating high aspect ratio nanostructures, however, conventional synthetic methods are often restricted to batch-wise and costly processes. Herein, we demonstrate a non-traditional, frugal approach to synthesize 1D coordination polymers by in situ etching of zerovalent metal particle precursors. This procedure is denoted as the heterogeneous metal/ligand reaction and was demonstrated on Group 13 metals as a proof of concept. Simple carboxylic acids supply the etchant protons and ligands for metal ions (conjugate base) in a 1 : 1 ratio. This scalable reaction produces a 1D polymer that assembles into high-aspect ratio 'nanobeams'. We demonstrate control over crystal structure and morphology by tuning the: (i) metal center, (ii) stoichiometry and (iii) structure of the ligands. This work presents a general scalable method for continuous, heat free and water-based coordination polymer synthesis.
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Affiliation(s)
- Boyce S Chang
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, IA 50011, USA. and US DOE Ames Laboratory, Ames, Iowa, USA50011.
| | - Brijith Thomas
- US DOE Ames Laboratory, Ames, Iowa, USA50011. and Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA 50011, USA
| | - Jiahao Chen
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, IA 50011, USA.
| | - Ian D Tevis
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, IA 50011, USA.
| | - Paul Karanja
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, IA 50011, USA.
| | - Simge Çınar
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, IA 50011, USA.
| | - Amrit Venkatesh
- US DOE Ames Laboratory, Ames, Iowa, USA50011. and Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA 50011, USA
| | - Aaron J Rossini
- US DOE Ames Laboratory, Ames, Iowa, USA50011. and Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA 50011, USA
| | - Martin M Thuo
- Department of Materials Science and Engineering, Iowa State University, 2220 Hoover Hall, Ames, IA 50011, USA.
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Cheng HW, Wu ZP, Yan S, Li J, Shan S, Wang L, Porter MD, Zhong CJ. A simple vaporous probe with atomic-scale sensitivity to structural ordering and orientation of molecular assembly. Chem Sci 2019; 10:7104-7110. [PMID: 31588278 PMCID: PMC6677115 DOI: 10.1039/c9sc01656b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 06/12/2019] [Indexed: 11/29/2022] Open
Abstract
Understanding the structural ordering and orientation of interfacial molecular assemblies requires an insight into the penetration depth of the probe molecules which determines the interfacial reactivity. In contrast to the conventional liquid probe-based contact angle measurement in which penetration depth is complicated by the liquid cohesive interaction, we report here a new approach that features a simple combination of vaporous hexane, which involves only van der Waals interaction, and quartz crystal microbalance operated at the third harmonic resonance, which is sensitive to sub-monolayer (0.2%) adsorption. Using this combination, we demonstrated the ability of probing the structural ordering and orientation of the self-assembled monolayers with a sensitivity from penetrating the top portion of the monolayers to interacting with the very top atomic structure at the interface. The determination of the dependence of the adsorption energy of vaporous hexane on the penetration depth in the molecular assembly allowed us to further reveal the atomic-scale origin of the odd-even oscillation, which is also substantiated by density functional theory calculations. The findings have broader implications for designing interfacial reactivities of molecular assemblies with atomic-scale depth precision.
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Affiliation(s)
- Han-Wen Cheng
- School of Chemical and Environmental Engineering , Shanghai Institute of Technology , Shanghai 201418 , China .
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , USA .
| | - Zhi-Peng Wu
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , USA .
| | - Shan Yan
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , USA .
| | - Jing Li
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , USA .
| | - Shiyao Shan
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , USA .
| | - Lichang Wang
- Department of Chemistry and Biochemistry , Southern Illinois University , Carbondale , Illinois 62901 , USA
| | - Marc D Porter
- Department of Chemistry and Chemical Engineering , University of Utah , Salt Lake City , Utah 84112 , USA .
| | - Chuan-Jian Zhong
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , USA .
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33
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Chinwangso P, St Hill LR, Marquez MD, Lee TR. Unsymmetrical Spiroalkanedithiols Having Mixed Fluorinated and Alkyl Tailgroups of Varying Length: Film Structure and Interfacial Properties. Molecules 2018; 23:E2632. [PMID: 30322175 PMCID: PMC6222720 DOI: 10.3390/molecules23102632] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 09/19/2018] [Accepted: 09/25/2018] [Indexed: 02/01/2023] Open
Abstract
A custom-designed series of unsymmetrical spiroalkanedithiols having tailgroups comprised of a terminally fluorinated chain and a hydrocarbon chain of varying lengths were synthesized and used to prepare self-assembled monolayers (SAMs) on gold substrates. The specific structure of the adsorbates was of the form [CH₃(CH₂)n][CF₃(CF₂)₇(CH₂)₈]C[CH₂SH]₂, where n = 7, 9, and 15 (designated as F8H10-C10, F8H10-C12, and F8H10-C18, respectively). The influence of the length of the hydrocarbon chain in the bidentate dithiol on the structure and interfacial properties of the monolayer was explored. A structurally analogous partially fluorinated monodentate alkanethiol and the corresponding normal alkanethiols were used to generate appropriate SAMs as reference systems. Measurements of ellipsometric thickness showed an unexpectedly low film thickness for the SAMs derived from the bidentate adsorbates, possibly due to disruptions in interchain packing caused by the fluorocarbon chains (i.e., phase-incompatible fluorocarbon-hydrocarbon interactions), ultimately giving rise to loosely packed and disordered films. Analysis by X-ray photoelectron spectroscopy (XPS) were also consistent with a model in which the films were loosely packed; additionally, the XPS spectra confirmed the attachment of the sulfur headgroups of the bidentate adsorbates onto the gold substrates. Studies of the SAMs by polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS) suggested that as the length of the hydrocarbon chain in the adsorbates was extended, a more ordered surface was achieved by reducing the tilt of the fluorocarbon segment. The wettability data indicated that the adsorbates with longer alkyl chains were less wettable than those with shorter alkyl chains, likely due to an increase in interchain van der Waals forces in the former.
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Affiliation(s)
- Pawilai Chinwangso
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5003, USA.
| | - Lydia R St Hill
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5003, USA.
| | - Maria D Marquez
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5003, USA.
| | - T Randall Lee
- Department of Chemistry and the Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5003, USA.
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34
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Kong GD, Jin J, Thuo M, Song H, Joung JF, Park S, Yoon HJ. Elucidating the Role of Molecule–Electrode Interfacial Defects in Charge Tunneling Characteristics of Large-Area Junctions. J Am Chem Soc 2018; 140:12303-12307. [DOI: 10.1021/jacs.8b08146] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gyu Don Kong
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Junji Jin
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Martin Thuo
- Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, United States
| | - Hyunsun Song
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | | | - Sungnam Park
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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35
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Cui X, Liu J, Xie L, Huang J, Liu Q, Israelachvili JN, Zeng H. Modulation of Hydrophobic Interaction by Mediating Surface Nanoscale Structure and Chemistry, not Monotonically by Hydrophobicity. Angew Chem Int Ed Engl 2018; 57:11903-11908. [PMID: 30043553 DOI: 10.1002/anie.201805137] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Indexed: 11/08/2022]
Abstract
The hydrophobic (HB) interaction plays a critical role in many colloidal and interfacial phenomena, biophysical and industrial processes. Surface hydrophobicity, characterized by the water contact angle, is generally considered the most dominant parameter determining the HB interaction. Herein, we quantified the HB interactions between air bubbles and a series of hydrophobic surfaces with different nanoscale structures and surface chemistry in aqueous media using a bubble probe atomic force microscopy (AFM). Surprisingly, it is discovered that surfaces of similar hydrophobicity can show different ranges of HB interactions, while surfaces of different hydrophobicity can have similar ranges of HB interaction. The increased heterogeneity of the surface nanoscale structure and chemistry can effectively decrease the decay length of HB interaction from 1.60 nm to 0.35 nm. Our work provides insights into the physical mechanism of HB interaction.
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Affiliation(s)
- Xin Cui
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
| | - Jing Liu
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
| | - Lei Xie
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
| | - Jun Huang
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
| | - Qi Liu
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
| | - Jacob N Israelachvili
- Department of Chemical Engineering, Materials Department, University of California Santa Barbara, CA, 93106, USA
| | - Hongbo Zeng
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada
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Cui X, Liu J, Xie L, Huang J, Liu Q, Israelachvili JN, Zeng H. Modulation of Hydrophobic Interaction by Mediating Surface Nanoscale Structure and Chemistry, not Monotonically by Hydrophobicity. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201805137] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Xin Cui
- Department of Chemical and Materials Engineering; University of Alberta; Edmonton Alberta T6G 1H9 Canada
| | - Jing Liu
- Department of Chemical and Materials Engineering; University of Alberta; Edmonton Alberta T6G 1H9 Canada
| | - Lei Xie
- Department of Chemical and Materials Engineering; University of Alberta; Edmonton Alberta T6G 1H9 Canada
| | - Jun Huang
- Department of Chemical and Materials Engineering; University of Alberta; Edmonton Alberta T6G 1H9 Canada
| | - Qi Liu
- Department of Chemical and Materials Engineering; University of Alberta; Edmonton Alberta T6G 1H9 Canada
| | - Jacob N. Israelachvili
- Department of Chemical Engineering; Materials Department; University of California Santa Barbara; CA 93106 USA
| | - Hongbo Zeng
- Department of Chemical and Materials Engineering; University of Alberta; Edmonton Alberta T6G 1H9 Canada
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37
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Dionne ER, Dip C, Toader V, Badia A. Micromechanical Redox Actuation by Self-Assembled Monolayers of Ferrocenylalkanethiolates: Evens Push More Than Odds. J Am Chem Soc 2018; 140:10063-10066. [PMID: 30070479 DOI: 10.1021/jacs.8b04054] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Microcantilever transducers can be valuable tools for the investigation of physicochemical processes in organized molecular films. Gold-coated cantilevers are used here to investigate the electrochemomechanics of redox-active self-assembled monolayers (SAMs) of ferrocenylalkanethiolates (Fc(CH2) nS) of different alkyl chain lengths. A significant odd-even effect is observed in the surface stress and cantilever movement generated by the oxidation of the SAM-confined ferrocenes as the number of methylene units n in the SAM backbone is varied. We demonstrate that stronger alkyl chain-chain interactions are at the origin of the larger surface stresses generated by SAMs with an even versus odd n. The findings highlight the impact of subtle structural effects and weak van der Waals interactions on the mechanical actuation produced by redox reactions in self-assembled systems.
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Affiliation(s)
- Eric R Dionne
- Département de chimie , Université de Montréal , C.P. 6128, succursale Centre-ville , Montréal , QC H3C 3J7 , Canada.,Quebec Center for Advanced Materials , FRQNT , Canada
| | - Christopher Dip
- Département de chimie , Université de Montréal , C.P. 6128, succursale Centre-ville , Montréal , QC H3C 3J7 , Canada.,Quebec Center for Advanced Materials , FRQNT , Canada
| | - Violeta Toader
- Department of Chemistry , McGill University , 801 rue Sherbrooke Ouest , Montréal , QC H3A 2K6 , Canada.,Quebec Center for Advanced Materials , FRQNT , Canada
| | - Antonella Badia
- Département de chimie , Université de Montréal , C.P. 6128, succursale Centre-ville , Montréal , QC H3C 3J7 , Canada.,Quebec Center for Advanced Materials , FRQNT , Canada
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38
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Substrate-Induced Liquid Layering: A New Insight into the Heterogeneous Nucleation of Liquid Metals. METALS 2018. [DOI: 10.3390/met8070521] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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39
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Chang B, Martin A, Gregory P, Kundu S, Du C, Orondo M, Thuo M. Functional Materials through Surfaces and Interfaces. ACTA ACUST UNITED AC 2018. [DOI: 10.1557/adv.2018.399] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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40
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Chen J, Giroux TJ, Nguyen Y, Kadoma AA, Chang BS, VanVeller B, Thuo MM. Understanding interface (odd–even) effects in charge tunneling using a polished EGaIn electrode. Phys Chem Chem Phys 2018; 20:4864-4878. [DOI: 10.1039/c7cp07531f] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Charge transport across large area molecular tunneling junctions is widely studied due to its potential in the development of quantum electronic devices.
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Affiliation(s)
- Jiahao Chen
- Department of Materials Science and Engineering
- Iowa State University
- Ames
- USA
| | - Thomas J. Giroux
- Department of Mechanical Engineering
- Iowa State University
- Ames
- USA
| | - Yen Nguyen
- Department of Chemistry
- Iowa State University
- Ames
- USA
| | - Atte A. Kadoma
- Department of Materials Science and Engineering
- Iowa State University
- Ames
- USA
| | - Boyce S. Chang
- Department of Materials Science and Engineering
- Iowa State University
- Ames
- USA
| | | | - Martin M. Thuo
- Department of Materials Science and Engineering
- Iowa State University
- Ames
- USA
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41
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Chen J, Wang Z, Oyola-Reynoso S, Thuo MM. Properties of Self-Assembled Monolayers Revealed via Inverse Tensiometry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13451-13467. [PMID: 28777587 DOI: 10.1021/acs.langmuir.7b01937] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Self-assembled monolayers (SAMs) have emerged as a simple platform technology and hence have been broadly studied. With advances in state-of-the-art fabrication and characterization methods, new insights into SAM structure and related properties have been delineated, albeit with some discrepancies and/or incoherencies. Some discrepancies, especially between experimental and theoretical work, are in part due to the misunderstanding of subtle structural features such as phase evolution and SAM quality. Recent work has, however, shown that simple techniques, such as the measurement of static contact angles, can be used to delineate otherwise complex properties of the SAM, especially when complemented by other more advanced techniques. In this article, we highlight the effect of nanoscale substrate asperities and molecular chain length on the SAM structure and associated properties. First, surfaces with tunable roughness are prepared on both Au and Ag, and their corresponding n-alkanethiolate SAMs are characterized through wetting and spectroscopy. From these data, chain-length- and substrate-morphology-dependent limits to the odd-even effect (structure and properties vary with the number of carbons in the molecules and the nature of the substrate), parametrization of gauche defect densities, and structural phase evolution (liquidlike, waxy, crystalline interfaces) are deduced. An evaluation of the correlation between the effect of roughness and the components of surface tension (polar-γp and dispersive-γd) reveals that wetting, at nanoscale rough surfaces, evolves proportionally with the ratio of the two components of surface tension. The evolution of conformational order is captured over a range of molecular lengths and parametrized through a dimensionless number, χc. By deploying a well-known tensiometry technique (herein the liquid is used to characterize the solid, hence the term inverse tensiometry) to characterize SAMs, we demonstrate that complex molecular-level phenomena in SAMs can be understood through simplicity.
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Affiliation(s)
- Jiahao Chen
- Department of Materials Science and Engineering, Iowa State University , 2220 Hoover Hall, Ames, Iowa 50011, United States
| | - Zhengjia Wang
- Department of Materials Science and Engineering, Iowa State University , 2220 Hoover Hall, Ames, Iowa 50011, United States
| | - Stephanie Oyola-Reynoso
- Department of Materials Science and Engineering, Iowa State University , 2220 Hoover Hall, Ames, Iowa 50011, United States
| | - Martin M Thuo
- Department of Materials Science and Engineering, Iowa State University , 2220 Hoover Hall, Ames, Iowa 50011, United States
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