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Siddiqui AR, N'Diaye J, Santiago-Carboney A, Martin K, Bhargava R, Rodríguez-López J. Spectroelectrochemical determination of thiolate self-assembled monolayer adsorptive stability in aqueous and non-aqueous electrolytes. Analyst 2024; 149:2842-2854. [PMID: 38600773 DOI: 10.1039/d4an00241e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2024]
Abstract
Self-assembled monolayers (SAM) are ubiquitous in studies of modified electrodes for sensing, electrocatalysis, and environmental and energy applications. However, determining their adsorptive stability is crucial to ensure robust experiments. In this work, the stable potential window (SPW) in which a SAM-covered electrode can function without inducing SAM desorption was determined for aromatic SAMs on gold electrodes in aqueous and non-aqueous solvents. The SPWs were determined by employing cyclic voltammetry, attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), and surface plasmon resonance (SPR). The electrochemical and spectroscopic findings concluded that all the aromatic SAMs used displayed similar trends and SPWs. In aqueous systems, the SPW lies between the reductive desorption and oxidative desorption, with pH being the decisive factor affecting the range of the SPW, with the widest SPW observed at pH 1. In the non-aqueous electrolytes, the desorption of SAMs was observed to be slow and progressive. The polarity of the solvent was the main factor in determining the SPW. The lower the polarity of the solvent, the larger the SPW, with 1-butanol displaying the widest SPW. This work showcases the power of spectroelectrochemical analysis and provides ample future directions for the use of non-polar solvents to increase SAM stability in electrochemical applications.
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Affiliation(s)
- Abdur-Rahman Siddiqui
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA.
| | - Jeanne N'Diaye
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA.
- The Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA
| | | | - Kristin Martin
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA.
| | - Rohit Bhargava
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA.
- The Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA
- Department of Bioengineering and Cancer Center at Illinois, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA
| | - Joaquín Rodríguez-López
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA.
- The Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801, USA
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Karunarathne DJ, Aminifazl A, Abel TE, Quepons KL, Golden TD. Corrosion Inhibition Effect of Pyridine-2-Thiol for Brass in An Acidic Environment. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27196550. [PMID: 36235087 PMCID: PMC9573544 DOI: 10.3390/molecules27196550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 09/20/2022] [Accepted: 09/28/2022] [Indexed: 11/07/2022]
Abstract
In this study, the inhibitive performance of pyridine-2-thiol added to a corrosive solution was investigated for brass using potentiodynamic polarization, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy. Electrochemical experiments were performed with different inhibitor concentrations in 0.5 M H2SO4 as the corrosive medium. For potentiodynamic polarization, icorr values decreased significantly for the inhibited solutions in contrast with the uninhibited solution. Pyridine-2-thiol had an optimum inhibition concentration of 0.25 mM, giving an icorr value of 1.8 µA/cm2 compared to 26 µA/cm2 for the blank solution. EIS data indicated that Rp and Rct values increased substantially after the addition of the corrosion inhibitor and corrosion inhibition efficiencies of more than 85% was achieved for the majority of the inhibited solutions. Scanning electron microscopy showed defect free and less scale formation for the inhibited surface but the bare brass surface had larger amounts of scale formation. X-ray photoelectron spectroscopy and UV-vis spectroscopy was used to investigate surface chemical composition and inhibitor structural changes over time.
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Cai ZF, Käser T, Kumar N, Zenobi R. Visualizing On-Surface Decomposition Chemistry at the Nanoscale Using Tip-Enhanced Raman Spectroscopy. J Phys Chem Lett 2022; 13:4864-4870. [PMID: 35617121 DOI: 10.1021/acs.jpclett.2c01112] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Chemical imaging of molecular decomposition processes at solid-liquid interfaces is a long-standing problem in achieving mechanistic understanding. Conventional analytical tools fail to meet this challenge due to the lack of required chemical sensitivity and specificity at the nanometer scale. In this work, we demonstrate that high-resolution hyperspectral tip-enhanced Raman spectroscopy (TERS) imaging can be a powerful analytical tool for studying on-surface decomposition chemistry at the nanoscale. Specifically, we present a TERS-based hyperspectral approach to visualize the on-surface decomposition process of a pyridine-4-thiol self-assembled monolayer on atomically flat Au(111) surfaces under ambient conditions. Reactive intermediates involved in the degradation process are spectroscopically detected with 5 nm spatial resolution. With supporting density functional theory simulations, a key species could be assigned to the disulfide reaction intermediate. This work opens a new application area for studying on-surface decomposition chemistry and related dynamics quantitatively at solid-liquid interfaces with nanometer spatial resolution.
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Affiliation(s)
- Zhen-Feng Cai
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, Zurich CH-8093, Switzerland
| | - Timon Käser
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, Zurich CH-8093, Switzerland
| | - Naresh Kumar
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, Zurich CH-8093, Switzerland
| | - Renato Zenobi
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, Zurich CH-8093, Switzerland
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Bennett TLR, Alshammari M, Au-Yong S, Almutlg A, Wang X, Wilkinson LA, Albrecht T, Jarvis SP, Cohen LF, Ismael A, Lambert CJ, Robinson BJ, Long NJ. Multi-Component Self-Assembled Molecular-Electronic Films: Towards New High-Performance Thermoelectric Systems. Chem Sci 2022; 13:5176-5185. [PMID: 35655580 PMCID: PMC9093172 DOI: 10.1039/d2sc00078d] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 04/14/2022] [Indexed: 12/02/2022] Open
Abstract
The thermoelectric properties of parallel arrays of organic molecules on a surface offer the potential for large-area, flexible, solution processed, energy harvesting thin-films, whose room-temperature transport properties are controlled by quantum interference (QI). Recently, it has been demonstrated that constructive QI (CQI) can be translated from single molecules to self-assembled monolayers (SAMs), boosting both electrical conductivities and Seebeck coefficients. However, these CQI-enhanced systems are limited by rigid coupling of the component molecules to metallic electrodes, preventing the introduction of additional layers which would be advantageous for their further development. These rigid couplings also limit our ability to suppress the transport of phonons through these systems, which could act to boost their thermoelectric output, without comprising on their impressive electronic features. Here, through a combined experimental and theoretical study, we show that cross-plane thermoelectricity in SAMs can be enhanced by incorporating extra molecular layers. We utilize a bottom-up approach to assemble multi-component thin-films that combine a rigid, highly conductive ‘sticky’-linker, formed from alkynyl-functionalised anthracenes, and a ‘slippery’-linker consisting of a functionalized metalloporphyrin. Starting from an anthracene-based SAM, we demonstrate that subsequent addition of either a porphyrin layer or a graphene layer increases the Seebeck coefficient, and addition of both porphyrin and graphene leads to a further boost in their Seebeck coefficients. This demonstration of Seebeck-enhanced multi-component SAMs is the first of its kind and presents a new strategy towards the design of thin-film thermoelectric materials. Through an experimental and theoretical study, cross-plane thermoelectricity in Self-Assembled Monolayers (SAMs) was enhanced by adding extra molecular layers, presenting a new strategy towards the design of high thermoelectric materials.![]()
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Affiliation(s)
- Troy L R Bennett
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Majed Alshammari
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, Jouf University Skaka Saudi Arabia
| | - Sophie Au-Yong
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | - Ahmad Almutlg
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Mathematics, College of Science, Qassim University Almethnab Saudi Arabia
| | - Xintai Wang
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Luke A Wilkinson
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - Tim Albrecht
- Department of Chemistry, Birmingham University Edgbaston Birmingham B15 2TT UK
| | - Samuel P Jarvis
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | - Lesley F Cohen
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Ali Ismael
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
| | - Colin J Lambert
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | | | - Nicholas J Long
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
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Hermann JM, Müller H, Daccache L, Adler C, Keller S, Metzler M, Jacob T, Kibler LA. Formic acid oxidation reaction on Au(111) electrodes modified with 4-mercaptopyridine SAM. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.138547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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6
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Hydrogen Peroxide Oxidation Reaction on a 4-Mercaptopyridine Self-Assembled Monolayer on Au(111) Metallized by Platinum Nanoislands. Electrocatalysis (N Y) 2021. [DOI: 10.1007/s12678-021-00647-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
AbstractA systematic investigation of the hydrogen peroxide oxidation reaction (HPOR) in phosphate buffer (pH = 7.3) on an Au(111) single crystal modified with a 4-mercaptopyridine self-assembled monolayer (SAM) has been conducted before and after metallization with Pt. While bare Au(111) shows considerable electrocatalytic activity towards the HPOR, the inhibition of the oxidation reaction after modification with the SAM implies that adsorbed 4-mercaptopyridine molecules do not catalyze the HPOR. However, SAM-modified Au(111) recovers catalytic activity for the HPOR already after a single metallization step fabricating Pt islands on-top. Hydrogen peroxide (HP) may then either react at the (non-metallic) Pt nanoislands or on reactivated Au sites, made accessible by structural changes of the SAM induced by the metallization. The shape of the voltammetric profiles for the HPOR on repeatedly metallized SAMs suggests that the contribution of Au to the total current density gradually diminishes with increasing Pt coverage while the contribution of the Pt islands increases. The electrochemical behavior is dominated by the Pt islands at a coverage of 0.5 ML obtained by three subsequent metallization steps.
Graphical abstract
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Yao Z, Buck M, Bühl M. Density Functional Theory Study of Pd Aggregation on a Pyridine-Terminated Self-Assembled Monolayer. Chemistry 2020; 26:10555-10563. [PMID: 32428284 PMCID: PMC7497155 DOI: 10.1002/chem.202001242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/13/2020] [Indexed: 11/08/2022]
Abstract
By using density functional theory calculations, the initial steps towards Pd metal cluster formation on a pyridine-terminated self-assembled monolayer (SAM) consisting of 3-(4-(pyridine-4-yl)phenyl)propane-1-thiol on an Au(1 1 1) surface are investigated. Theoretical modelling allows the investigation of structural details of the SAM surface and the metal/SAM interface at the atomic level, which is essential for elucidating the nature of Pd-SAM and Pd-Pd interactions at the liquid/solid interface and gaining insight into the mechanism of metal nucleation in the initial stage of electrodeposition. The structural flexibility of SAM molecules was studied first and the most stable conformation was identified, planar molecules in a herringbone packing, as the model for Pd adsorption. Two binding sites are found for Pd atoms on the pyridine end group of the SAM. The strong interaction between Pd atoms and pyridines illustrates the importance of SAM functionalisation in the metal nucleation process. Consistent with an energetic driving force of approximately -0.3 eV per Pd atom towards Pd aggregation suggested by static calculations, a spontaneous Pd dimerisation is observed in ab initio molecular dynamic studies of the system. Nudged elastic band calculations suggest a potential route with a low energy barrier of 0.10 eV for the Pd atom diffusion and then dimerisation on top of the SAM layer.
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Affiliation(s)
- Zhen Yao
- EaStCHEM School of ChemistryUniversity of St AndrewsNorth HaughSt AndrewsFifeKY16 9STUK
| | - Manfred Buck
- EaStCHEM School of ChemistryUniversity of St AndrewsNorth HaughSt AndrewsFifeKY16 9STUK
| | - Michael Bühl
- EaStCHEM School of ChemistryUniversity of St AndrewsNorth HaughSt AndrewsFifeKY16 9STUK
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8
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Uzundal CB, Sahin O, Gokturk PA, Wu H, Mugele F, Ulgut B, Suzer S. X-ray Photoelectron Spectroscopy with Electrical Modulation Can Be Used to Probe Electrical Properties of Liquids and Their Interfaces at Different Stages. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:16989-16999. [PMID: 31794669 DOI: 10.1021/acs.langmuir.9b03134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Operando X-ray photoelectron spectroscopy (o-XPS) has been used to record the binding energy shifts in the C 1s peak of a pristine poly(ethylene glycol) (PEG) liquid drop in an electrowetting on dielectric (EWOD) geometry and after exposing it to several high-voltage breakdown processes. This was achieved by recording XPS data while the samples were subjected to 10 V dc and ac (square-wave modulation) actuations to extract electrical information related to the liquid and its interface with the dielectric. Through analysis of the XPS data under ac actuation, a critical frequency of 170 Hz is extracted for the pristine PEG, which is translated to a resistance value of 14 MΩ for the liquid and a capacitance value of 60 pF for the dielectric, by the help of simulations using an equivalent circuit model and also by XPS analyses of a mimicking device under similar conditions. The same measurements yield an increased value of 23 MΩ for the resistance of the liquid after the breakdown by assuming that the capacitance of the dielectric stays constant. In addition, an asymmetry in polarity dependence is observed with respect to both the onset of the breakdown voltage and also the leakage behavior of the deteriorated (PEG + dielectric) system such that deviations are more pronounced at positive voltages. Both dc and ac behaviors of the postbreakdown system can also be simulated, but only by introducing an additional element, a diode or a polarity- and magnitude-dependent voltage source (VCVS), which might be attributed to negative charge accumulation at the interface. Measurements for a liquid mixture of PEG with 8% ionic liquid yields an almost 2 orders of magnitude smaller resistance for the drop as a result of the enhanced conductivity by the ions. Coupled with modeling, XPS measurements under dc and ac modulations enable probing unique electrochemical properties of liquid/solid interfaces.
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Affiliation(s)
- Can Berk Uzundal
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
| | - Ozgur Sahin
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
| | | | - Hao Wu
- Physics of Complex Fluids , University of Twente , 7522 NB , Enschede , The Netherlands
| | - Frieder Mugele
- Physics of Complex Fluids , University of Twente , 7522 NB , Enschede , The Netherlands
| | - Burak Ulgut
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
| | - Sefik Suzer
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
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9
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She Z, Yao Z, Ménard H, Tobish S, Lahaye D, Champness NR, Buck M. Coordination controlled electrodeposition and patterning of layers of palladium/copper nanoparticles on top of a self-assembled monolayer. NANOSCALE 2019; 11:13773-13782. [PMID: 31305824 DOI: 10.1039/c9nr03927a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A scheme for the generation of bimetallic nanoparticles is presented which combines electrodeposition of one type of metal, coordinated to a self-assembled monolayer (SAM), with another metal deposited from the bulk electrolyte. In this way PdCu nanoparticles are generated by initial complexation of Pd2+ to a SAM of 3-(4-(pyridine-4-yl)phenyl)propane-1-thiol (PyP3) on Au/mica and subsequent reduction in an acidic aqueous CuSO4 electrolyte. Cyclic voltammetry reveals that the onset of Cu deposition is triggered by Pd reduction. Scanning tunneling microscopy (STM) shows that layers of connected particles are formed with an average thickness of less than 3 nm and lateral dimensions of particles in the range of 2 to 5 nm. In X-ray photoelectron spectra a range of binding energies for the Pd 3d signal is observed whereas the Cu 2p signal appears at a single binding energy, even though chemically different Cu species are present: normal and more noble Cu. Up to three components are seen in the N 1s signal, one originating from protonated pyridine moieties, the others reflecting the SAM-metal interaction. It is suggested that the coordination controlled electrodeposition yields layers of particles composed of a Pd core and a Cu shell with a transition region of a PdCu alloy. Deposited on top of the PyP3 SAM, the PdCu particles exhibit weak adhesion which is exploited for patterning by selective removal of particles employing scanning probe techniques. The potential for patterning down to the sub-10 nm scale is demonstrated. Harnessing the deposition contrast between native and PdCu loaded PyP3 SAMs, structures thus created can be developed into patterned continuous layers.
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Affiliation(s)
- Zhe She
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK.
| | - Zhen Yao
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK.
| | - Hervé Ménard
- Leverhulme Research Centre for Forensic Science, University of Dundee, Dundee, DD1 4HN, UK
| | - Sven Tobish
- Drochaid Research Services, North Haugh, St. Andrews, KY16 9ST, UK
| | - Dorothée Lahaye
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Neil R Champness
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Manfred Buck
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK.
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Yi S, Lee WK, Park JH, Lee JS, Seo JH. One-Pot Synthesis of a Zwitterionic Small Molecule Bearing Disulfide Moiety for Antibiofouling Macro- and Nanoscale Gold Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:1768-1777. [PMID: 30103611 DOI: 10.1021/acs.langmuir.8b01532] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The goal of this study is to develop a simple one-pot method for the synthesis of a zwitterionic small molecule bearing disulfide moiety, which can effectively inhibit nonspecific protein adsorption on macroscopic and nanoscopic gold surfaces. To this end, the optimal molecular structure of a pyridine disulfide derivative was explored and a zwitterionic small molecule was successfully synthesized from the tertiary amine residue on the pyridine ring through a one-pot method. The coating conditions of the synthesized zwitterionic molecules on the gold surface were optimized through contact angle measurements, and the strong interactions between the gold surface and the disulfide moiety of the zwitterion small molecule were confirmed by surface plasmon resonance (SPR) analysis and X-ray photoelectron spectroscopy. The antibiofouling properties of the coated gold surface were analyzed by fluorescence microscopic observations after contacting with FITC-labeled bovine serum albumin (BSA) and SPR sensor as contacting with BSA solution. In addition, the effect of zwitterion-coating on the salt stability of and protein adsorption on nanoscopic gold surfaces were examined through a NaCl stability test and BSA adsorption test, respectively. From the obtained results, it was confirmed that the simply synthesized zwitterionic small molecule was effective in inhibiting nonspecific protein adsorption on macroscopic and nanoscopic gold surfaces; further, it enhanced the salt stability of gold nanoparticle surfaces.
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Affiliation(s)
- Seungjoo Yi
- Department of Materials Science and Engineering , Korea University , 145 Anam-ro , Seongbuk-gu , Seoul 02841 , Korea
| | - Won Kyu Lee
- Department of Materials Science and Engineering , Korea University , 145 Anam-ro , Seongbuk-gu , Seoul 02841 , Korea
| | - Ji-Ho Park
- Department of Chemistry , Sogang University , 35 Baekbeom-ro , Mapo-gu , Seoul 04107 , Korea
| | - Jae-Seung Lee
- Department of Materials Science and Engineering , Korea University , 145 Anam-ro , Seongbuk-gu , Seoul 02841 , Korea
| | - Ji-Hun Seo
- Department of Materials Science and Engineering , Korea University , 145 Anam-ro , Seongbuk-gu , Seoul 02841 , Korea
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11
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Wattanavichean N, Gilby M, Nichols RJ, Arnolds H. Detection of Metal–Molecule–Metal Junction Formation by Surface Enhanced Raman Spectroscopy. Anal Chem 2019; 91:2644-2651. [DOI: 10.1021/acs.analchem.8b03576] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Nungnit Wattanavichean
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom
| | - Matthew Gilby
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom
| | - Richard J. Nichols
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom
| | - Heike Arnolds
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom
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Schneider S, Partes C, Wiesner A, Terfort A. Potential-induced phase transition of benzoxazole-2-thiol, naphthaleneoxazole-2-thiol and anthraceneoxazole-2-thiol monolayers on gold electrodes. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2018.06.123] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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13
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Herrera S, Tasca F, Williams FJ, Calvo EJ. Adsorption of 4,4'-Dithiodipyridine Axially Coordinated to Iron(II) Phthalocyanine on Au(111) as a New Strategy for Oxygen Reduction Electrocatalysis. Chemphyschem 2018; 19:1599-1604. [PMID: 29601134 DOI: 10.1002/cphc.201800139] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Indexed: 11/08/2022]
Abstract
The coordination of PySSPy to FePc was monitored by UV/Vis spectroscopy while the adsobed FePc, anchored by PyS-Au(111), was examined by in situ STM in 0.1 M HClO4 and X-ray photoelectron spectroscopy (XPS). Rotating-disc-electrode (RDE) and linear-sweep-voltammetry (LSV) studies on the resulting FePc-modified Au(111) electrodes in an oxygen-saturated 0.1 M NaOH electrolyte exhibit excellent electrocatalytic properties for the oxygen reduction reaction (ORR), with a smaller overpotential than that observed for Au(111) with FePc deposited by direct adsorption from a benzene solution.
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Affiliation(s)
- Santiago Herrera
- Department of Inorganic Chemistry, Analytical and Chemical Physics, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires Ciudad Universitaria, Pabellón 2, Buenos Aires, C1428EHA, Argentina
| | - Federico Tasca
- Department of Chemistry Materials, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. Libertador Bernardo O'Higgins, 3363, Santiago, Chile
| | - Federico J Williams
- Department of Inorganic Chemistry, Analytical and Chemical Physics, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires Ciudad Universitaria, Pabellón 2, Buenos Aires, C1428EHA, Argentina
| | - Ernesto J Calvo
- Department of Inorganic Chemistry, Analytical and Chemical Physics, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires Ciudad Universitaria, Pabellón 2, Buenos Aires, C1428EHA, Argentina
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14
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Müller H, Metzler M, Barth N, Conings B, Boyen HG, Jacob T, Kibler LA. Electrocatalytic Behavior of Pd and Pt Nanoislands Deposited onto 4,4′-Dithiodipyridine SAMs on Au(111). Electrocatalysis (N Y) 2018. [DOI: 10.1007/s12678-018-0467-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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15
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Herrera S, Tasca F, Williams FJ, Calvo EJ, Carro P, Salvarezza RC. Surface Structure of 4-Mercaptopyridine on Au(111): A New Dense Phase. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:9565-9572. [PMID: 28849939 DOI: 10.1021/acs.langmuir.7b01627] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
4-Mercaptopyridine (4MPy) self-assembled on Au(111) has been studied by in situ electrochemical scanning tunneling microscopy (EC-STM) in HClO4, cyclic voltammetry, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). Samples prepared by varying the immersion time at constant concentration named short time (30 s) and long time (3 min) adsorption have been studied. Cyclic voltammetry and XPS showed that the chemistry of the adsorbed molecules does not depend on the adsorption time resulting in a well established chemisorbed thiol self-assembled monolayer on Au(111). EC-STM study of the short time adsorption sample revealed a new self-assembled structure after a cathodic desorption/readsorption sweep, which remains stable only if the potential is kept negative to the Au(111) zero charge potential (EPZC). DFT calculations have shown a correlation between the observed structure and a dense weakly adsorbed phase with a surface coverage of θ = 0.4 and a (5 × √3) lattice configuration. At potentials positive to the EPZC, the weakly adsorbed state becomes unstable, and a different structure is formed due to the chemisorption driven by the electrostatic interaction. Long time adsorption experiments, on the other hand, have shown the typical (5 × √3) structure with θ = 0.2 surface coverage (chemisorbed phase) and are stable over the whole potential range. The difference observed in long time and short time immersion can be explained by the optimization of molecular interactions during the self-assembly process.
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Affiliation(s)
- Santiago Herrera
- Departamento de Química Inorgánica, Analítica y Química Física, INQUIMAE-CONICET, Facultad Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria , Pabellón 2, Buenos Aires C1428EHA, Argentina
| | - Federico Tasca
- Departamento de Química Inorgánica, Analítica y Química Física, INQUIMAE-CONICET, Facultad Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria , Pabellón 2, Buenos Aires C1428EHA, Argentina
| | - Federico J Williams
- Departamento de Química Inorgánica, Analítica y Química Física, INQUIMAE-CONICET, Facultad Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria , Pabellón 2, Buenos Aires C1428EHA, Argentina
| | - Ernesto J Calvo
- Departamento de Química Inorgánica, Analítica y Química Física, INQUIMAE-CONICET, Facultad Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria , Pabellón 2, Buenos Aires C1428EHA, Argentina
| | - Pilar Carro
- Área de Química Física, Departamento de Química, Facultad de Ciencias, Universidad de La Laguna, Instituto de Materiales y Nanotecnología , Avenida Francisco Sánchez, s/n 38200-La Laguna, Tenerife, Spain
| | - Roberto C Salvarezza
- INIFTA Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata - CONICET- Sucursal 4 Casilla de Correo 16, 1900) La Plata, Argentina
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16
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Structural studies of self-assembled monolayers of 4-mercaptopyridine on gold electrodes with surface-enhanced Raman spectroscopy. J Solid State Electrochem 2015. [DOI: 10.1007/s10008-015-2869-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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17
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Haidar I, Lau-Truong S, Aubard J, Renault JP, Félidj N, Maurel F, Boubekeur-Lecaque L. Oxadiazole-2-thiol adsorption on gold nanorods: a joint theoretical and experimental study by using SERS, XPS, and DFT. Chemphyschem 2014; 15:3646-54. [PMID: 25157617 DOI: 10.1002/cphc.201402197] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Indexed: 11/07/2022]
Abstract
The chemisorption of 1,3,4-oxadiazole-2-thiol (ODT) on gold nanorods has been investigated by using surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT). Although most of the SERS spectra have remarkable similarity to the normal Raman spectra of the pure analyte, the adsorption of ODT on a gold surface leads to a drastic change in its Raman spectrum and distinct vibrational features are obtained with gold nanorods and spherical nanoparticles. Simulated Raman spectra for hybrid systems that consist of an oxadiazole moiety coordinated to a Au20 gold cluster provided valuable information about the coordination mode and enabled us to assign vibration modes.
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Affiliation(s)
- Israa Haidar
- Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR CNRS 7086, 15 rue Jean-Antoine de Baïf, 75205 Paris Cedex 13 (France), Tel: (+33) 1-57-27-87-72
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18
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NISHIYAMA K, HARADA H, YOSHIMOTO S, YAMADA T, TANIGUCHI I. Effect of Annealing on 4- and 3-Pyridinethiol Self-assembled Monolayers on Au(111) and Au(100) Studied by High-resolution Electron Energy Loss Spectroscopy. ELECTROCHEMISTRY 2014. [DOI: 10.5796/electrochemistry.82.391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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19
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Traulsen CHH, Kunz V, Heinrich T, Richter S, Holzweber M, Schulz A, von Krbek LKS, Scheuschner UTJ, Poppenberg J, Unger WES, Schalley CA. Synthesis and coordinative layer-by-layer deposition of pyridine-functionalized gold nanoparticles and tetralactam macrocycles on silicon substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:14284-14292. [PMID: 24160686 DOI: 10.1021/la403222x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Coordination chemistry was applied to deposit pyridine-functionalized gold nanoparticles on silicon substrates. The particles were synthesized through the Brust/Schiffrin route with a subsequent ligand exchange reaction yielding well-defined particles of two different sizes. Multilayer deposition was carried out on a pyridine-terminated SAM, anchored on a hydroxyl-terminated silicon surface. Analogously, Hunter/Vögtle-type tetralactam macrocycle multilayers were deposited as well as mixed layers containing both either in an alternating sequence or as a macrocycle multilayer with a terminating nanoparticle layer. These composite layers were examined with respect to their ability to bind squaraine axles in the macrocycle cavities. The amount of guest bound is higher for the composite layer with alternating macrocycles and nanoparticles.
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Affiliation(s)
- Christoph H-H Traulsen
- Institut für Chemie und Biochemie der Freien Universität Berlin, Takustraße 3, 14195 Berlin, Germany
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20
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Bashir A, Azzam W, Rohwerder M, Terfort A. Polymorphism in self-assembled terphenylthiolate monolayers on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:13449-13456. [PMID: 24083467 DOI: 10.1021/la403116r] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Self-assembled monolayers (SAMs) of terphenylthiol (TPT) on gold Au(111) substrates exhibit well-ordered structures over large scales if they are annealed in ethanol at 40 °C after their formation. Using high-resolution STM, two distinct, ordered phases could be observed. The simpler phase, designated as α-phase, consists of closely packed molecules in the well-known (2√3 × √3)R30° structure. It could be demonstrated that under less suitable imaging conditions this phase can be mistaken as the hexagonal (√3 × √3)R30°, which resolves a discrepancy in between previous reports. The second phase is characterized by a stripe pattern with a periodicity of 2.0 nm and can be described by a point-on-line incommensurate (4 × n) ([Formula: see text]) lattice with n close to 8. This β-phase contains four pairs of terphenylthiolate molecules, which might be held together by either disulfide bonds or the recently discussed S-Au-S motif, and is thus 35% ± 15% less densely packed than the α-phase. The coexistence of these phases explains the variability of spectroscopic results obtained in the past for terphenylthiolate layers, since their relative proportion determines the average thicknesses/tilt angles found in these studies.
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Affiliation(s)
- Asif Bashir
- Max-Planck-Institut für Eisenforschung GmbH , Max-Planck-Straße 1, 40237 Düsseldorf, Germany
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21
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Koelsch P, Muglali M, Rohwerder M, Erbe A. Third-order effects in resonant sum-frequency-generation signals at electrified metal/liquid interfaces. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. B, OPTICAL PHYSICS 2013; 30:10.1364/JOSAB.30.000219. [PMID: 24235781 PMCID: PMC3825253 DOI: 10.1364/josab.30.000219] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Vibrational sum-frequency-generation (SFG) spectroscopy experiments at electrified interfaces involve incident laser radiation at frequencies in the IR and near-IR/visible regions as well as a static electric field on the surface. Here we show that mixing the three fields present on the surface can result in third-order effects in resonant SFG signals. This was achieved for closed packed self-assembled monolayers (SAMs) with molecular groups of high optical nonlinearity and surface potentials similar to those typically applied in cyclic voltammograms. Broadband SFG spectroscopy was applied to study a hydrophobic well-ordered araliphatic SAM on a Au(111) surface using a thin-layer analysis cell for spectro-electrochemical investigations in a 100 mM NaOH electrolyte solution. Resonant contributions were experimentally separated from non-resonant contributions of the Au substrate and theoretically analyzed using a fitting function including third-order terms. The resulting ratio of third-order to second-order susceptibilities was estimated to be [Formula: see text](10-10) m/V.
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Affiliation(s)
- Patrick Koelsch
- National ESCA and Surface Analysis Center for Biomedical Problems, Department of Bioengineering, University of Washington, Box 35170, Seattle, Washington 98195-1750, USA
| | - Mutlu Muglali
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf, Germany
| | - Michael Rohwerder
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf, Germany
| | - Andreas Erbe
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf, Germany
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22
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Houmam A, Muhammad H, Koczkur KM. Rapid formation of a dense sulfur layer on gold through use of triphenylmethane sulfenyl chloride as a precursor. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:16881-16889. [PMID: 23131048 DOI: 10.1021/la3032607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The use of triphenylmethane sulfenyl chloride as a new precursor leads to the efficient deposition of sulfur on polycrystalline gold and Au(111) substrates. The modified surfaces are characterized using X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning tunneling microscopy (STM). The XPS data shows the rapid deposition of polymeric sulfur within very short times. Electrochemical stripping cyclic voltammetry (CV) confirms the rapid deposition and shows that high coverage values are achieved. STM imaging shows the formation of a wide range sulfur layer and production of the well-known etch pits. High-resolution STM images confirm the high density of the sulfur layers and show formation of a long-range phase consisting of rhombus structures close to the previously described rectangular structures along with other parallelograms and partial parallelograms. The present results do not show the initial formation of any organic self-assembled monolayer (SAM) indicating that the formation of polymeric sulfur does not result from the decomposition of an initial SAM as previously observed with alkyl and aryl thiolate-based SAMs. The suggested mechanism involves an initial reductive process similar to the one reported for thiocyanates and sulfenyl chlorides. This is followed by the dissociation of the Ph(3)C-S bond, leaving only sulfur on the surface, through a process leading to the recombination of the remaining fragments to yield triphenylmethyl chloride.
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Affiliation(s)
- Abdelaziz Houmam
- Electrochemical Technology Centre, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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23
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Muhammad H, Koczkur KM, Kycia AH, Houmam A. Nitro-substituted arene sulfenyl chlorides as precursors to the formation of aromatic SAMs. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15853-15863. [PMID: 23078107 DOI: 10.1021/la303395e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The formation of aromatic SAMs on Au(111) using three nitro-substituted arene sulfenyl chlorides (4-nitrophenyl sulfenyl chloride (1), 2-nitrophenyl sulfenyl chloride (2), and 2,4-dinitrophenyl sulfenyl chloride (3)) is studied. The formation of SAMs and their quality are investigated as a function of the position of the nitro substituent(s) on the aromatic ring. The modified surfaces are characterized by X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), polarization modulation infrared reflection absorption spectroscopy (PMIRRAS), and cyclic voltammetry (CV). The results show that all three compounds are deposited on Au within very short times. The corresponding coverages are determined using CV. However, only compound 1 forms stable, long-range, well-ordered SAMs. The 4-nitrophenyl thiolate is adsorbed nearly vertically on the Au surface. Compounds 2 and 3 both form lower-quality SAMs where the adsorbed nitro-phenyl thiolates are more tilted. These SAMs are less stable than the ones obtained with the 4-nitrosubsituted precursor and decompose with time, leaving only sulfur on the gold surface.
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Affiliation(s)
- Hamida Muhammad
- Electrochemical Technology Centre, Department of Chemistry, University of Guelph, Guelph, Ontario, Canada
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24
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Metzler M, Fantauzzi D, Anton J, Jacob T. Surface Modification of a n-Si(111) Electrode through Aldehyde Grafting and Subsequent Metallization: Theory and Experiment. Z PHYS CHEM 2012. [DOI: 10.1524/zpch.2012.0309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
Motivated by our previous studies on metallic substrates, in the present work we addressed the functionalization and the subsequent metallization of a hydrogen-terminated n-Si(111) electrode. DFT provides atomistic insights on the grafting mechanism of 4-pyridinecarboxaldehyde (C6H5NO) what encouraged electrochemical investigations, i. e. cyclic voltammetry and in-situ STM, combined with XPS measurements which together provide evidence for a successful transfer of the so far obtained knowledge from metal single crystal to semiconductor surfaces.
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Affiliation(s)
- Martin Metzler
- Ulm University, Institute of Electrochemistry, Ulm, Deutschland
| | | | - Josef Anton
- Ulm University, Institute of Electrochemistry, Ulm, Deutschland
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25
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Richter S, Poppenberg J, Traulsen CHH, Darlatt E, Sokolowski A, Sattler D, Unger WES, Schalley CA. Deposition of Ordered Layers of Tetralactam Macrocycles and Ether Rotaxanes on Pyridine-Terminated Self-Assembled Monolayers on Gold. J Am Chem Soc 2012; 134:16289-97. [DOI: 10.1021/ja306212m] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Sebastian Richter
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Johannes Poppenberg
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Christoph H.-H. Traulsen
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Erik Darlatt
- BAM-Bundesanstalt für
Materialforschung und -prüfung, Unter den Eichen 44-46, 12203
Berlin, Germany
| | - Anja Sokolowski
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Dominik Sattler
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Wolfgang E. S. Unger
- BAM-Bundesanstalt für
Materialforschung und -prüfung, Unter den Eichen 44-46, 12203
Berlin, Germany
| | - Christoph A. Schalley
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
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26
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Pensa E, Cortés E, Corthey G, Carro P, Vericat C, Fonticelli MH, Benítez G, Rubert AA, Salvarezza RC. The chemistry of the sulfur-gold interface: in search of a unified model. Acc Chem Res 2012; 45:1183-92. [PMID: 22444437 DOI: 10.1021/ar200260p] [Citation(s) in RCA: 288] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Over the last three decades, self-assembled molecular films on solid surfaces have attracted widespread interest as an intellectual and technological challenge to chemists, physicists, materials scientists, and biologists. A variety of technological applications of nanotechnology rely on the possibility of controlling topological, chemical, and functional features at the molecular level. Self-assembled monolayers (SAMs) composed of chemisorbed species represent fundamental building blocks for creating complex structures by a bottom-up approach. These materials take advantage of the flexibility of organic and supramolecular chemistry to generate synthetic surfaces with well-defined chemical and physical properties. These films already serve as structural or functional parts of sensors, biosensors, drug-delivery systems, molecular electronic devices, protecting capping for nanostructures, and coatings for corrosion protection and tribological applications. Thiol SAMs on gold are the most popular molecular films because the resulting oxide-free, clean, flat surfaces can be easily modified both in the gas phase and in liquid media under ambient conditions. In particular, researchers have extensively studied SAMs on Au(111) because they serve as model systems to understand the basic aspects of the self-assembly of organic molecules on well-defined metal surfaces. Also, great interest has arisen in the surface structure of thiol-capped gold nanoparticles (AuNPs) because of simple synthesis methods that produce highly monodisperse particles with controllable size and a high surface/volume ratio. These features make AuNPs very attractive for technological applications in fields ranging from medicine to heterogeneous catalysis. In many applications, the structure and chemistry of the sulfur-gold interface become crucial since they control the system properties. Therefore, many researchers have focused on understanding of the nature of this interface on both planar and nanoparticle thiol-covered surfaces. However, despite the considerable theoretical and experimental efforts made using various sophisticated techniques, the structure and chemical composition of the sulfur-gold interface at the atomic level remains elusive. In particular, the search for a unified model of the chemistry of the S-Au interface illustrates the difficulty of determining the surface chemistry at the nanoscale. This Account provides a state-of-the-art analysis of this problem and raises some questions that deserve further investigation.
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Affiliation(s)
- Evangelina Pensa
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata - CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata, Argentina
| | - Emiliano Cortés
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata - CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata, Argentina
| | - Gastón Corthey
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata - CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata, Argentina
| | - Pilar Carro
- Departamento de Química Física, Instituto de Materiales y Nanotecnología, Universidad de La Laguna, Tenerife, Spain
| | - Carolina Vericat
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata - CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata, Argentina
| | - Mariano H. Fonticelli
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata - CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata, Argentina
| | - Guillermo Benítez
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata - CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata, Argentina
| | - Aldo A. Rubert
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata - CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata, Argentina
| | - Roberto C. Salvarezza
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata - CONICET, Sucursal 4 Casilla de Correo 16 (1900) La Plata, Argentina
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Traulsen CHH, Darlatt E, Richter S, Poppenberg J, Hoof S, Unger WES, Schalley CA. Intermixed terpyridine-functionalized monolayers on gold: nonlinear relationship between terpyridyl density and metal ion coordination properties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:10755-10763. [PMID: 22741945 DOI: 10.1021/la301644r] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Aiming at the functionalization of surfaces with terpyridine anchors for the coordinative deposition of additional layers, mixed self-assembled monolayers (SAMs) were prepared from binary solutions of 12-(2,2':6',2″-terpyridine-4'-yl)dodecane-1-thiol (TDT) and 1-decanethiol (DT). The SAMs and the order of the constituting molecules were analyzed by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and time-of-flight-secondary ion mass spectrometry (ToF-SIMS). The composition of the (TDT/DT)-SAMs and with it the surface density of terpyridyl groups correlates linearly with the relative concentrations of the two compounds in the solution used for depositing them. In marked contrast, the amount of terpyridine-coordinated Pd(II) ions significantly deviates from this trend with an optimum at a 1:3 ratio of TDT/DT. This indicates a major fraction of the terpyridines in TDT-rich SAMs not to be accessible for Pd(II) ion coordination. In agreement, NEXAFS spectroscopy reveals the alkyl backbones in TDT-rich SAMs not to be ordered, while they are preferentially upright oriented in the optimal 1:3-(TDT/DT)-SAMs. We interpret this in terms of terpyridine backfolding in TDT-rich SAMs, while they are located in accessible positions on top of the SAM in the 1:3-(TDT/DT)-SAM. While the alkyl backbones in the 1:3-(TDT/DT)-SAM are ordered, NEXAFS spectroscopy shows the terpyridyl groups not to have a preferential orientation in this SAM and thus retain enough flexibility to adjust to molecules that are deposited on top of the mixed SAM. In conclusion, the novel SAM does not undergo phase separation and consists predominantly of intermixed phases with adjustable surface density of quite flexible terpyridine anchor groups. The terpyridine-Pd(II) anchors are not only available for a future deposition of the next layer, but the metal ions also represent a sensitive probe for the accessibility of the terpyridyl groups.
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Affiliation(s)
- Christoph H-H Traulsen
- Institut für Chemie und Biochemie der Freien Universität Berlin, Takustrasse 3, 14195 Berlin, Germany
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28
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Ramírez EA, Cortés E, Rubert AA, Carro P, Benítez G, Vela ME, Salvarezza RC. Complex surface chemistry of 4-mercaptopyridine self-assembled monolayers on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:6839-6847. [PMID: 22497438 DOI: 10.1021/la204951u] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The adsorption of 4-mercaptopyridine on Au(111) from aqueous or ethanolic solutions is studied by different surface characterization techniques and density functional theory calculations (DFT) including van der Waals interactions. X-ray photoelectron spectroscopy and electrochemical data indicate that self-assembly from 4-mercaptopyridine-containing aqueous 0.1 M NaOH solutions for short immersion times (few minutes) results in a 4-mercaptopyridine (PyS) self-assembled monolayer (SAM) with surface coverage 0.2. Scanning tunneling microscopy images show an island-covered Au surface. The increase in the immersion time from minutes to hours results in a complete SAM degradation yielding adsorbed sulfur and a heavily pitted Au surface. Adsorbed sulfur is also the main product when the self-assembly process is made in ethanolic solutions irrespective of the immersion time. We demonstrate for the first time that a surface reaction is involved in PyS SAM decomposition in ethanol, a surface process not favored in water. DFT calculations suggest that the surface reaction takes place via disulfide formation driven by the higher stability of the S-Au(111) system. Other reactions that contribute to sulfidization are also detected and discussed.
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Affiliation(s)
- E A Ramírez
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
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Zhang J, Welinder AC, Chi Q, Ulstrup J. Electrochemically controlled self-assembled monolayers characterized with molecular and sub-molecular resolution. Phys Chem Chem Phys 2011; 13:5526-45. [PMID: 21336358 DOI: 10.1039/c0cp02183k] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Self-assembled organization of functional molecules on solid surfaces has developed into a powerful and sophisticated tool for surface chemistry and nanotechnology. A number of reviews on the topic have been available since the mid 1990s. This perspective article aims to focus on recent development in the investigations of electronic structures and assembling dynamics of electrochemically controlled self-assembled monolayers (SAMs) of thiol containing molecules on gold surfaces. A brief introduction is first given and particularly illustrated by a Table summarizing the molecules studied, the surface lattice structures and the experimental operating conditions. This is followed by discussion of two major high-resolution experimental methods, scanning tunnelling microscopy (STM) and single-crystal electrochemistry. In Section 3, we briefly address choice of supporting electrolytes and substrate surfaces, and their effects on the SAM structures. Section 4 constitutes the major body of the article by offering some details of recent studies for the selected cases, including in situ monitoring of assembling dynamics, molecular electronic structures, and the key external factors determining the SAM packing. In Section 5, we give examples of what can be offered by theoretical computations for the detailed understanding of the SAM electronic structures revealed by STM images. A brief summary of the current applications of SAMs in wiring metalloproteins, design and fabrication of sensors, and single-molecule electronics is described in Section 6. In the final two sections (7 and 8), we discuss the current status in understanding of electronic structures and properties of SAMs in electrochemical environments and what could be expected for future perspectives.
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Affiliation(s)
- Jingdong Zhang
- Department of Chemistry and NanoDTU, Technical University of Denmark, Lyngby, Denmark.
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Muglali MI, Bashir A, Terfort A, Rohwerder M. Electrochemical investigations on stability and protonation behavior of pyridine-terminated aromatic self-assembled monolayers. Phys Chem Chem Phys 2011; 13:15530-8. [DOI: 10.1039/c1cp21469a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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31
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Theoretical studies of Pd metal deposition on the √3×√3 4-mercaptopyridine self-assembled monolayer. Electrochim Acta 2010. [DOI: 10.1016/j.electacta.2010.04.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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32
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Keith JA, Jacob T. Atomic‐Level Elucidation of the Initial Stages of Self‐Assembled Monolayer Metallization and Nanoparticle Formation. Chemistry 2010; 16:12381-6. [PMID: 20845415 DOI: 10.1002/chem.201001396] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- John A. Keith
- Institut für Elektrochemie, Universität Ulm, Albert‐Einstein‐Allee 47, 89081, Ulm (Germany), Fax: (+49) 731‐50‐25409
| | - Timo Jacob
- Institut für Elektrochemie, Universität Ulm, Albert‐Einstein‐Allee 47, 89081, Ulm (Germany), Fax: (+49) 731‐50‐25409
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Yeşildağ A, Ekinci D. Covalent attachment of pyridine-type molecules to glassy carbon surfaces by electrochemical reduction of in situ generated diazonium salts. Formation of ruthenium complexes on ligand-modified surfaces. Electrochim Acta 2010. [DOI: 10.1016/j.electacta.2010.06.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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34
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Eberle F, Metzler M, Kolb DM, Saitner M, Wagner P, Boyen HG. Metallization of Ultra-Thin, Non-Thiol SAMs with Flat-Lying Molecular Units: Pd on 1, 4-Dicyanobenzene. Chemphyschem 2010; 11:2951-6. [PMID: 20715271 DOI: 10.1002/cphc.201000309] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Felix Eberle
- Institute of Electrochemistry, University of Ulm, 89069 Ulm, Germany
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35
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Liu J, Schüpbach B, Bashir A, Shekhah O, Nefedov A, Kind M, Terfort A, Wöll C. Structural characterization of self-assembled monolayers of pyridine-terminated thiolates on gold. Phys Chem Chem Phys 2010; 12:4459-72. [PMID: 20407720 DOI: 10.1039/b924246p] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Self-assembled monolayers (SAMs) fabricated on Au(111) substrates from a homologous series of pyridine-terminated organothiols have been investigated using ultra high vacuum infrared reflection adsorption spectroscopy (UHV-IRRAS), X-ray photoelectron spectroscopy (XPS), scanning tunnelling microscopy (STM) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. A total of 4 different pyridine-based organothiols have been investigated, consisting of a pyridine unit, one or two phenyl units, a spacer of between one and three methylene units and, finally, a thiol unit. For all pyridine-terminated thiols the immersion of Au-substrates in the corresponding ethanolic solutions was found to result in the formation of highly ordered and densely packed SAMs. For an even number of the methylene spacers between the SH group and the aromatic moieties, the SAM unit-cell is rather large, (5sq.rt(3) x 3)rect, whereas in case of an odd number of methylene units a smaller unit cell is adopted, (2sq.rt(3) x sq.rt(3))R30 degrees. The tilt angle of the molecules amounts to 15 degrees . In contrast to expectation, the pyridine-terminated organic surfaces exposed by the corresponding SAMs showed a surprisingly strong resistance with regard to protonation.
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Affiliation(s)
- Jinxuan Liu
- Lehrstuhl für Physikalische Chemie I, Ruhr-Universität Bochum, 44780 Bochum, Germany
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36
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Vericat C, Vela ME, Benitez G, Carro P, Salvarezza RC. Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system. Chem Soc Rev 2010; 39:1805-34. [PMID: 20419220 DOI: 10.1039/b907301a] [Citation(s) in RCA: 767] [Impact Index Per Article: 54.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Self-assembled monolayers (SAMs) of alkanethiols and dialkanethiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology. Despite the progress made in the knowledge of these fascinating two-dimensional molecular systems, there are still several "hot topics" that deserve special attention in order to understand and to control their physical and chemistry properties at the molecular level. This critical review focuses on some of these topics, including the nature of the molecule-gold interface, whose chemistry and structure remain elusive, the self-assembly process on planar and irregular surfaces, and on nanometre-sized objects, and the chemical reactivity and thermal stability of these systems in ambient and aqueous solutions, an issue which seriously limits their technological applications (375 references).
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Affiliation(s)
- C Vericat
- Instituto de Investigaciones Fisicoquímicas Teóricasy Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET, Sucursal 4 Casilla de Correo 16, (1900) La Plata, Argentina
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37
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Kucera J, Gross A. Geometric and electronic structure of Pd/4-aminothiophenol/Au(111) metal–molecule–metal contacts: a periodic DFT study. Phys Chem Chem Phys 2010; 12:4423-30. [PMID: 20407715 DOI: 10.1039/b923700c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Jan Kucera
- Institute for Theoretical Chemistry, Ulm University, D-89069 Ulm, Germany
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38
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Welinder AC, Zhang J, Steensgaard DB, Ulstrup J. Adsorption of human insulin on single-crystal gold surfaces investigated by in situ scanning tunnelling microscopy and electrochemistry. Phys Chem Chem Phys 2010; 12:9999-10011. [DOI: 10.1039/c0cp01021a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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39
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Silien C, Buck M, Goretzki G, Lahaye D, Champness NR, Weidner T, Zharnikov M. Self-assembly of a pyridine-terminated thiol monolayer on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:959-967. [PMID: 19138159 DOI: 10.1021/la802966s] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Self-assembled monolayers (SAMs) of 3-(4-pyridine-4-yl-phenyl)-propane-1-thiol (PyP3) on Au(111)/mica have been studied by scanning tunneling microscopy (STM), polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), high-resolution X-ray photoemission spectroscopy (HRXPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The quality of the SAM is found to be strongly dependent on the solvent. Substantial gold corrosion is observed if pure ethanol is used. In contrast, highly ordered and densely packed SAMs are formed from acetonitrile or a KOH/ethanol mixture. The structure is described by a 2 radical3 x radical3 unit cell with the aromatic moiety oriented nearly perpendicular to the surface. The PyP3 films form with the pyridine moiety deprotonated. Variation of pH allows reversible protonation without measurable damage of the SAM.
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Affiliation(s)
- Christophe Silien
- EaStChem School of Chemistry, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, UK.
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40
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Kucera J, Gross A. Adsorption of 4-mercaptopyridine on Au(111: a periodic DFT study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:13985-92. [PMID: 19360938 DOI: 10.1021/la802368j] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We have studied the adsorption of 4-mercaptopyridine (Mpy) on Au(111) using periodic density functional theory calculations. Isolated Mpy molecules adsorb preferentially at near-bridge sites in a tilted configuration. The interaction with water influences the adsorption of Mpy only weakly whereas the binding of ions to Mpy can lead to substantial structural changes in the Mpy adsorption geometry. At higher coverages, the molecules become more upright in order to allow for a denser packing in the self-assembled monolayers (SAMs). Simulated STM images of the 7 x mean square root of 3 and 5 x mean square root of 3 structures compare favorably with experimental results. Using an ab initio thermodynamics approach, we determined the most stable molecular structure as a function of the chemical potential of mercaptopyridine. The stability of the 7 x mean square root of 3 structure is confirmed, but the experimentally observed 5 x mean square root of 13 structure does not appear to be a thermodynamically stable structure. Several possible reasons for the discrepancy between theory and experiment are discussed.
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Affiliation(s)
- Jan Kucera
- Institute for Theoretical Chemistry, Ulm University, D-89069 Ulm, Germany
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41
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Koumoto K, Saito N, Gao Y, Masuda Y, Zhu P. Nano/Micro Patterning of Inorganic Thin Films. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2008. [DOI: 10.1246/bcsj.81.1337] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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42
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Lee CY, Tan YJ, Bond AM. Identification of Surface Heterogeneity Effects in Cyclic Voltammograms Derived from Analysis of an Individually Addressable Gold Array Electrode. Anal Chem 2008; 80:3873-81. [DOI: 10.1021/ac8002227] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chong-Yong Lee
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Yong-Jun Tan
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Alan M. Bond
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
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Shamsipur M, Kazemi S, Mehdinia A, Mousavi M, Sharghi H. Electron Transfer Behavior through Densely Packed Self-Assembled Monolayers of a Novel Heteroaromatic Thiol Derivative onto the Gold Surface. ELECTROANAL 2008. [DOI: 10.1002/elan.200704085] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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44
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Nishiyama K, Tsuchiyama M, Kubo A, Seriu H, Miyazaki S, Yoshimoto S, Taniguchi I. Conformational change in 4-pyridineethanethiolate self-assembled monolayers on Au(111) driven by protonation/deprotonation in electrolyte solutions. Phys Chem Chem Phys 2008; 10:6935-9. [DOI: 10.1039/b810777g] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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45
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Surface chemistry and electrocatalytic behaviour of tetra-carboxy substituted iron, cobalt and manganese phthalocyanine monolayers on gold electrode. Electrochim Acta 2007. [DOI: 10.1016/j.electacta.2007.08.044] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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46
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Manolova M, Kayser M, Kolb D, Boyen HG, Ziemann P, Mayer D, Wirth A. Rhodium deposition onto a 4-mercaptopyridine SAM on Au(111). Electrochim Acta 2007. [DOI: 10.1016/j.electacta.2006.08.038] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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47
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Yoshimoto S. Molecular Assemblies of Functional Molecules on Gold Electrode Surfaces Studied by Electrochemical Scanning Tunneling Microscopy: Relationship between Function and Adlayer Structures. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2006. [DOI: 10.1246/bcsj.79.1167] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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48
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Yang YC, Lee YL, Yang LYO, Yau SL. In situ scanning tunneling microscopy of 1,6-hexanedithiol, 1,9-nonanedithiol, 1,2-benzenedithiol, and 1,3-benzenedithiol adsorbed on pt(111) electrodes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:5189-95. [PMID: 16700612 DOI: 10.1021/la0529815] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM) were used to examine four dithiol molecules, including 1,6-hexanedithiol, 1,9-nonanedithiol, 1,2-benzenedithiol, and 1,3-benzenedithiol, adsorbed on well-ordered Pt(111) electrodes in 0.1 M HClO(4). The open-circuit potential (OCP) of Pt(111) electrodes decreased substantially from 0.95 to 0.3 V (versus reversible hydrogen electrode) upon the adsorption of dithol molecules, which indicates that these adsorbates injected electrons into the Pt electrode. For all dithiol molecules, ordered adlattices of p(2 x 2) and (square root 3 x square root 3)R30 degrees were formed when the dosing concentration was lower than 150 microM and the potential of Pt(111) was more negative than 0.5 V. Raising the potential of Pt(111) from 0.1 to 0.4 V or more positive values could transform p(2 x 2) to (square root 3 x square root 3)R30 degrees before it turned disarray. The insensitivity of the structure of dithiol adlayers with their chemical structures was explained by upright molecular orientation with the formation of one Pt-S bond per dithiol molecule. This molecular orientation was independent of the coverage of dithiol molecules, as nucleation seeds produced at the beginning of adsorption were also constructed with p(2 x 2). The triangular-shaped STM molecular resolution suggested 3-fold binding of sulfur headgroup on Pt(111). All dithiols were adsorbed so strongly on Pt(111) electrodes that switching the potential negatively to the onset of hydrogen evolution in 0.1 M HClO(4) or water reduction in 1 M KOH could not displace dithiol admolecules.
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Affiliation(s)
- Yaw-Chia Yang
- Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan 701
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49
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Boyen HG, Ziemann P, Wiedwald U, Ivanova V, Kolb DM, Sakong S, Gross A, Romanyuk A, Büttner M, Oelhafen P. Local density of states effects at the metal-molecule interfaces in a molecular device. NATURE MATERIALS 2006; 5:394-9. [PMID: 16582914 DOI: 10.1038/nmat1607] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Accepted: 01/23/2006] [Indexed: 05/08/2023]
Abstract
Clarifying the nature of interactions between metal electrodes and organic molecules still represent one of the challenging problems in molecular electronics that needs to be solved in order to optimize electron transport through a molecular device. For this purpose, electronic properties at metal-molecule interfaces were studied by combining experimental and theoretical methods. Applying a novel electrochemical approach, strictly two-dimensional Pd islands were prepared on top of 4-mercaptopyridine self-assembled monolayers (4MP-SAMs) which, in turn, were deposited on (111)-oriented Au single crystals. Electron spectroscopy together with density functional theory calculations revealed strong interactions between the molecules and the islands due to Pd-N bonds, resulting in a drastically reduced density of states (DOS) at the Fermi level EF for a nearly closed Pd monolayer, and even non-metallic properties for nanometre-sized islands. Similarly, a significantly reduced DOS at EF was observed for the topmost Au layer at the Au-SAM interface due to Au-S interactions, suggesting that these effects are rather general.
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Affiliation(s)
- Hans-Gerd Boyen
- Abteilung Festkörperphysik, Universität Ulm, D-89069 Ulm, Germany
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50
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Babić-Samardzija K, Lupu C, Hackerman N, Barron AR, Luttge A. Inhibitive properties and surface morphology of a group of heterocyclic diazoles as inhibitors for acidic iron corrosion. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:12187-96. [PMID: 16342991 DOI: 10.1021/la051766l] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The heterocyclic diazoles 3-amino-1H-isoindole, indazole, imidazole, 4-bromoimidazole, 4-methylimidazole, pyrazole, 4-nitropyrazole, and 4-sulfopyrazole were investigated as corrosion inhibitors of iron in 1 M HCl using ac and dc techniques. The polarization curves showed a decrease in corrosion current for the inhibitor-containing solution. Impedance spectra demonstrate that the charge-transfer resistance in the presence of these inhibitors was greater than in inhibitor-free solution, except for 4-nitropyrazole. The resistance increased with inhibitor concentration and with immersion time. The structural and electronic parameters of these diazoles were calculated using computational methodologies. The elemental composition and the speciation of the treated surfaces were investigated via XPS measurements, and morphological changes were monitored by vertical scanning interferometery.
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Affiliation(s)
- Ksenija Babić-Samardzija
- Department of Chemistry, Rice University, Houston, Texas 77005, and Department of Earth Science, Rice University, Houston, Texas 77005, USA
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