1
|
Hoshi N, Nakamura M. Enhancement of the Activity for the Oxygen Reduction Reaction on Well-defined Single Crystal Electrodes of Pt by Hydrophobic Species. CHEM LETT 2021. [DOI: 10.1246/cl.200608] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Nagahiro Hoshi
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Masashi Nakamura
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| |
Collapse
|
2
|
WADA N, KUMEDA T, NAKAMURA M, HOSHI N. Effects of the Alkane on the Oxygen Reduction Reaction on Well-Defined Pt Surfaces. ELECTROCHEMISTRY 2020. [DOI: 10.5796/electrochemistry.20-00043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Naoya WADA
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University
| | - Tomoaki KUMEDA
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University
| | - Masashi NAKAMURA
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University
| | - Nagahiro HOSHI
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University
| |
Collapse
|
3
|
Yasini P, Afsari S, Peng H, Pikma P, Perdew JP, Borguet E. Potential-Induced High-Conductance Transport Pathways through Single-Molecule Junctions. J Am Chem Soc 2019; 141:10109-10116. [DOI: 10.1021/jacs.9b05448] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
4
|
Cyclic Voltammetry and <i>in situ</i> Infrared Reflection Absorption Spectroscopy on Kinetic Effect of Physisorbed Dioctadecylsulfide on a Cu-UPD Process on Au(111) Electrode Surface. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2018. [DOI: 10.1380/ejssnt.2018.60] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
5
|
Afsari S, Li Z, Borguet E. Amine-Directed Hydrogen-Bonded Two-Dimensional Supramolecular Structures. Chemphyschem 2016; 17:3385-3389. [DOI: 10.1002/cphc.201600686] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Sepideh Afsari
- Department of Chemistry; Temple University; Philadelphia Pennsylvania 19122 USA
| | - Zhihai Li
- Department of Chemistry; Ball State University; Muncie Indiana 47306 USA
| | - Eric Borguet
- Department of Chemistry; Temple University; Philadelphia Pennsylvania 19122 USA
| |
Collapse
|
6
|
Potential-dependent morphological change of n-hexadecane small droplets on a Au(1 1 1) electrode in aqueous solution: A voltammetric and electrochemical fluorescence microscopic study. J Electroanal Chem (Lausanne) 2016. [DOI: 10.1016/j.jelechem.2016.05.040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
7
|
Yasuda S, Kumagai R, Nakashima K, Murakoshi K. Electrochemical Potential Stabilization of Reconstructed Au(111) Structure by Monolayer Coverage with Graphene. J Phys Chem Lett 2015; 6:3403-3409. [PMID: 26279244 DOI: 10.1021/acs.jpclett.5b01488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The electrochemical properties of a monolayer graphene grown on a Au(111) electrode were studied using cyclic voltammetry (CV) and electrochemical scanning tunneling microscopy (EC-STM). CV and EC-STM measurements in 0.1 M H2SO4 aqueous solution revealed that graphene grown on the reconstructed (22 × √3) Au(111) structure effectively inhibited potential-induced structural transitions between reconstructed (22 × √3) and unreconstructed (1 × 1), and the adsorption/desorption of SO4(2-) ions, which are intrinsic behavior of the bare Au(111) surface. The underlying reconstructed structure was significantly stabilized by covering with monolayer graphene over a wide potential range between -0.2 V and +1.35 V vs Ag/AgCl (saturated KCl), which is much wider than that for bare Au(111) (-0.2 to + 0.35 V vs Ag/AgCl (saturated KCl)). Such high stability has not been reported to date; therefore, these results are considered to be important for understanding the fundamentals of surface reconstruction and also serve to open a new branch of electrochemistry related to graphene/metal-electrolyte interfaces.
Collapse
Affiliation(s)
- Satoshi Yasuda
- Department of Chemistry, Faculty of Science, Hokkaido University , Sapporo, Hokkaido 060-0810, Japan
- Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology, Kawaguchi, Saitama 332-0012, Japan
| | - Ryota Kumagai
- Department of Chemistry, Faculty of Science, Hokkaido University , Sapporo, Hokkaido 060-0810, Japan
| | - Koji Nakashima
- Department of Chemistry, Faculty of Science, Hokkaido University , Sapporo, Hokkaido 060-0810, Japan
| | - Kei Murakoshi
- Department of Chemistry, Faculty of Science, Hokkaido University , Sapporo, Hokkaido 060-0810, Japan
| |
Collapse
|
8
|
Smetanin M, Sek S, Maran F, Lipkowski J. Molecular resolution visualization of a pore formed by trichogin, an antimicrobial peptide, in a phospholipid matrix. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:3130-6. [DOI: 10.1016/j.bbamem.2014.08.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 08/05/2014] [Accepted: 08/07/2014] [Indexed: 11/16/2022]
|
9
|
Josephs EA, Shao J, Ye T. Nanografting sodium dodecyl sulfate under potential control: new insights into tip-directed molecular assembly. NANOSCALE 2013; 5:4139-4143. [PMID: 23571812 DOI: 10.1039/c3nr00771e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We have demonstrated that under potential control, sodium dodecyl sulfate can form ordered and stable patterns within nanoscale regions of a pre-existing SAM where thiol molecules have been mechanically removed. The results offer novel insights into the mechanism of nanografting and new routes to fabricating diverse chemical structures on surfaces.
Collapse
Affiliation(s)
- Eric A Josephs
- School of Engineering, University of California, Merced, Merced, California, USA
| | | | | |
Collapse
|
10
|
Direct visualization of the alamethicin pore formed in a planar phospholipid matrix. Proc Natl Acad Sci U S A 2012; 109:21223-7. [PMID: 23236158 DOI: 10.1073/pnas.1201559110] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We present direct visualization of pores formed by alamethicin (Alm) in a matrix of phospholipids using electrochemical scanning tunneling microscopy (EC-STM). High-resolution EC-STM images show individual peptide molecules forming channels. The channels are not dispersed randomly in the monolayer but agglomerate forming 2D nanocrystals with a hexagonal lattice in which the average channel-channel distance is 1.90 ± 0.1 nm. The STM images suggest that each Alm is shared between the two adjacent channels. Every channel consists of six Alm molecules. Three or four of these molecules have the hydrophilic group oriented toward the center of the channel allowing for water column formation inside the channel. The dimensions of the central pore in the images are consistent with the dimension of the water column in a model of hexameric pore proposed in the literature. The images obtained in this work validate the barrel-stave model of the pore formed in phospholipid membranes by amphiphatic peptides. They also provide direct evidence for cluster formation by such pores.
Collapse
|
11
|
Mali KS, Adisoejoso J, De Cat I, Balandina T, Ghijsens E, Guo Z, Li M, Sankara Pillai M, Vanderlinden W, Xu H, De Feyter S. Physisorption for Self-Assembly of Supramolecular Systems: A Scanning Tunneling Microscopy Perspective. Supramol Chem 2012. [DOI: 10.1002/9780470661345.smc146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
12
|
Ahn S, Matzger AJ. Additive Perturbed Molecular Assembly in Two-Dimensional Crystals: Differentiating Kinetic and Thermodynamic Pathways. J Am Chem Soc 2012; 134:3208-14. [DOI: 10.1021/ja210933h] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Seokhoon Ahn
- Department of Chemistry and the Macromolecular Science
and Engineering Program, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Adam J. Matzger
- Department of Chemistry and the Macromolecular Science
and Engineering Program, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| |
Collapse
|
13
|
Geitner NK, Bhattacharya P, Steele M, Chen R, Ladner DA, Ke PC. Understanding dendritic polymer–hydrocarbon interactions for oil dispersion. RSC Adv 2012. [DOI: 10.1039/c2ra21602g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
14
|
Sadegh Hassani S, Kim YG, Borguet E. Self-assembly of insoluble porphyrins on Au(111) under aqueous electrochemical control. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:14828-14833. [PMID: 22111691 DOI: 10.1021/la201308g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Self-assembled monolayers of a water-insoluble porphyrin, tetraphenyl porphyrin (TPP), in the presence of an aqueous electrolyte were characterized in situ with electrochemical scanning tunneling microscopy (EC-STM) at working electrode potentials of between 0.5 and -0.2 V. Isolated domains of TPP monolayers with differing orientation were observed on Au(111) in 0.1 M HClO(4) over this entire potential window. Individual TPP molecules could be resolved over a range of 700 mV, from open circuit potential (OCP) to near the hydrogen evolution potential. The unit cell is square, and the distance between neighboring molecules is about 1.4 ± 0.1 nm. High-resolution images allow the internal molecular structure to be discerned. No changes in the STM contrast of individual molecules were observed as the potential was changed. In a neutral electrolyte (0.1 M KClO(4), pH ~6), the potential range of stability of ordered structures is reduced. On HOPG, TPP forms ordered hexagonal structures with a lattice constant of about 2.6 nm in the double-layer potential region in 0.1 M HClO(4).
Collapse
|
15
|
Tang Y, Yan J, Zhu F, Sun C, Mao B. Comparative electrochemical scanning tunneling microscopy study of nonionic fluorosurfactant zonyl FSN self-assembled monolayers on Au(111) and Au(100): a potential-induced structural transition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:943-947. [PMID: 21214202 DOI: 10.1021/la103812v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We investigate the structure of nonionic fluorosurfactant zonyl FSN self-assembled monolayers on Au(111) and Au(100) in 0.05 M H(2)SO(4) as a function of the electrode potential by electrochemical scanning tunneling microscopy (ECSTM). On Au(111), a (3(1/2) × 3(1/2))R30° arrangement of the FSN SAMs is observed, which remains unchanged in the potential range where the redox reaction of FSN molecules does not occur. On Au(100), some parallel corrugations of the FSN SAMs are observed, which originate from the smaller distance and the repulsive interaction between FSN molecules to make the FSN molecules deviate from the bridging sites, and ECSTM reveals a potential-induced structural transition of the FSN SAMs. The experimental observations are rationalized by the effect of the intermolecular interaction. The smaller distance between molecules on Au(100) results in the repulsive force, which increases the probability of structural change induced by external factors (i.e., the electrode potential). The appropriate distance and interactions of FSN molecules account for the stable structure of FSN SAMs on Au(111). Surface crystallography may influence the intermolecular interaction through changing the molecular arrangements of the SAMs. The results benefit the molecular-scale understanding of the behavior of the FSN SAMs under electrochemical potential control.
Collapse
Affiliation(s)
- Yongan Tang
- State Key Laboratory for Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, PR China
| | | | | | | | | |
Collapse
|
16
|
Morrison CN, Ahn S, Schnobrich JK, Matzger AJ. Two-dimensional crystallization of carboxylated benzene oligomers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:936-942. [PMID: 21207984 DOI: 10.1021/la103794j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Various carboxylic acid substitution patterns on the 1,3,5-triphenylbenzene nucleus were explored, and their influence on the symmetry of the resulting two-dimensional (2D) crystal structures was assessed. The symmetry of 1,3,5-benzenetribenzoic acid (H(3)BTB) was reduced by modifying the substitution pattern of the arene and/or adding an additional carboxylic acid. Four analogues belonging to various point groups were studied. Comparison of the monolayers of the analogues to that of H(3)BTB shows that plane group symmetry and molecular symmetry are not correlated: H(3)BTB and its analogues exhibit the same plane group p2 at the heptanoic acid/graphite interface. The 2D crystal structure of the H(3)BTB analogues is more strongly controlled by the geometry of hydrogen-bonding interactions rather than molecular symmetry. Other significant observations in this study include porosity, uncommon hydrogen-bonding motifs, and an unusually high number of inquivalent molecules (Z' = 3) present in the 2D crystal of the lowest symmetry analogue. This research demonstrates that reduction of molecular symmetry based on geometric modification of noncovalent interactions allows for control over porosity of the 2D crystals (close-packed structures to nanoporous networks) without changing the core shape of the molecule.
Collapse
Affiliation(s)
- Christine N Morrison
- Department of Chemistry and the Macromolecular Science and Engineering Program, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | | | | | | |
Collapse
|
17
|
Zhang R, Yan Q, Shen Y, Gan L, Zeng QD, Zhao D, Wang C. Conformational polymorphism of multimeric perylene derivatives observed by using scanning tunneling microscopy. CrystEngComm 2011. [DOI: 10.1039/c1ce05273j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
18
|
Ahn S, Henssler JT, Matzger AJ. Conglomerate with periodic enantiomer inclusion: A mechanism for homochirality erosion. Chem Commun (Camb) 2011; 47:11432-4. [DOI: 10.1039/c1cc12317c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
19
|
|
20
|
Klymchenko AS, Furukawa S, Balandina T, Müllen K, Van der Auweraer M, De Feyter S. 2D analogues of the inverted hexagonal phase self-assembled from 4,6-dialkoxylated isophthalic acids at solid-liquid interfaces. NANOSCALE 2010; 2:1773-1780. [PMID: 20820709 DOI: 10.1039/c0nr00176g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Self-assembly of organic molecules at solid-liquid interfaces is a route for developing novel functional materials on surfaces and modeling assembly phenomena in 3D. 5-Alkoxylated isophthalic acids (ISA) are known to self-assemble into two-dimensional (2D) lamellae at the interface between a surface of Au(111) or HOPG (highly oriented pyrolytic graphite) and a solvent. Presently, the self-assembly of 4,6-dialkoxylated isophthalic acid derivatives with variable alkyl chain length is investigated at Au(111)-water, Au(111)-tetradecane and HOPG-tetradecane interfaces with a particular focus on the first one. The main aspect of this study is to evaluate the role of the molecular geometry and different interactions in the 2D assembly of amphiphilic molecules. In contrast to 5-alkoxylated ISA, 4,6-dialkoxylated ISA derivatives self-assemble preferentially into arrays of cyclic pentameric/hexameric structures, which appear as 2D analogues of the inverted hexagonal phase of lipids. As a general trend, the derivatives bearing shorter alkyl chains show a higher level of ordering at Au(111)-liquid interfaces. In particular, at the Au(111)-water interface, the 4,6-diheptyloxy ISA derivative forms exclusively pentamers, which are arranged in a quasi-hexagonal lattice. Moreover, the cyclic pentameric features are not empty but host a single isophthalic acid residue which is found to be dynamic. Finally, the packing of the diheptyloxy derivative shows a distinct potential dependence: while at more negative potentials the pentameric arrangement is converted into lamellae, at more positive potentials a loosely packed zig-zag pattern is formed. The present results show that at different solid-liquid interfaces 4,6-dialkoxylated ISA derivatives tend to form cyclic structures that are 2D analogues of an inverted hexagonal phase, akin to lipids having two hydrophobic alkyl chains and a small polar head group. Moreover, the substrate potential at the Au(111)-water interface can tune the 2D molecular arrangement.
Collapse
|
21
|
Tanaka KI. Surface Nano-Structuring by Adsorption and Chemical Reactions. MATERIALS 2010; 3:4518-4549. [PMID: 28883340 PMCID: PMC5445766 DOI: 10.3390/ma3094518] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 08/06/2010] [Accepted: 08/12/2010] [Indexed: 12/03/2022]
Abstract
Nano-structuring of the surface caused by adsorption of molecules or atoms and by the reaction of surface atoms with adsorbed species is reviewed from a chemistry viewpoint. Self-assembly of adsorbed species is markedly influenced by weak mutual interactions and the local strain of the surface induced by the adsorption. Nano-structuring taking place on the surface is well explained by the notion of a quasi-molecule provided by the reaction of surface atoms with adsorbed species. Self-assembly of quasi-molecules by weak internal bonding provides quasi-compounds on a specific surface. Various nano-structuring phenomena are discussed: (i) self-assembly of adsorbed molecules and atoms; (ii) self-assembly of quasi-compounds; (iii) formation of nano-composite surfaces; (iv) controlled growth of nano-materials on composite surfaces. Nano-structuring processes are not always controlled by energetic feasibility, that is, the formation of nano-composite surface and the growth of nano-particles on surfaces are often controlled by the kinetics. The idea of the “kinetic controlled molding” might be valuable to design nano-materials on surfaces.
Collapse
Affiliation(s)
- Ken-Ichi Tanaka
- Saitama Institute of Technology, Research Center of Advanced Sciences 1690 Okabe, Fukaya, Saitama, Japan.
| |
Collapse
|
22
|
|
23
|
McClelland AA, Ahn S, Matzger AJ, Chen Z. Deducing 2D crystal structure at the liquid/solid interface with atomic resolution: a combined STM and SFG study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:12847-12850. [PMID: 19852506 DOI: 10.1021/la902479v] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Sum frequency generation vibrational spectroscopy (SFG) has been applied to study two-dimensional (2D) crystals formed by an isophthalic acid diester on the surface of highly oriented pyrolytic graphite, providing complementary measurements to scanning tunneling microscopy (STM) and computational modeling. SFG results indicate that both aromatic and C=O groups in the 2D crystal tilt from the surface. This study demonstrates that a combination of SFG and STM techniques can be used to gain a more complete picture of 2D crystal structure, and it is necessary to consider solvent-2D crystal interactions and dynamics in the computer models to achieve an accurate representation of interfacial structure.
Collapse
Affiliation(s)
- Arthur A McClelland
- Applied Physics Program, University of Michigan, Ann Arbor, Michigan 48109, USA
| | | | | | | |
Collapse
|
24
|
Wang L, Ou-Yang L, Yau SL. Adlayer structure of octa-alkoxy-substituted copper(II) phthalocyanine on Au(111) by electrochemical scanning tunneling microscopy. Microsc Res Tech 2007; 71:20-5. [PMID: 17886341 DOI: 10.1002/jemt.20519] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Electrochemical scanning tunneling microscopy (ECSTM) has been used to examine the adlayer of octa-alkoxy-substituted copper(II) phthalocyanines (CuPc(OC(8)H(17))(8)) on Au(111) in 0.1 M HClO(4), where the molecular adlayer was prepared by spontaneous adsorption from a benzene solution containing this molecule. Topography STM scans revealed long-range ordered, interweaved arrays of CuPc(OC(8)H(17))(8) with coexistent rectangular and hexagonal symmetries. High-quality STM molecular resolution yielded the internal molecular structure and the orientation of CuPc(OC(8)H(17))(8) admolecules. These STM results could shed insight into the method of generating ordered molecular assemblies of phthalocyanine molecules with long-chained substitutes on metal surface.
Collapse
Affiliation(s)
- Li Wang
- College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, China.
| | | | | |
Collapse
|
25
|
Abstract
Self-assembled monolayers (SAMs) of alkanols (1-C(N)H(2N+1)OH) with varying carbon-chain lengths (N = 10-30) have been systematically studied by means of scanning tunneling microscopy (STM) at the interfaces between alkanol solutions (or liquids) and Au(111) surfaces. The carbon skeletons were found to lie flat on the surfaces. This orientation is consistent with SAMs of alkanols on highly oriented pyrolytic graphite (HOPG) and MoS2 surfaces, and also with alkanes on reconstructed Au(111) surfaces. This result differs from a prior report, which claimed that 1-decanol molecules (N = 10) stood on their ends with the OH polar groups facing the gold substrate. Compared to alkanes, the replacement of one terminal CH3 group with an OH group introduces new bonding features for alkanols owing to the feasibility of forming hydrogen bonds. While SAMs of long-chain alkanols (N > 18) resemble those of alkanes, in which the aliphatic chains make a greater contribution, hydrogen bonding plays a more important role in the formation of SAMs of short-chain alkanols. Thus, in addition to the titled lamellar structure, a herringbone-like structure, seldom seen in SAMs of alkanes, is dominant in alkanol SAMs for values of N < 18. The odd-even effect present in alkane SAMs is also present in alkanol SAMs. Thus, the odd N alkanols (alkanols with an odd number of carbon atoms) adopt perpendicular lamellar structures owing to the favorable interactions of the CH3 terminal groups, similar to the result observed for odd alkanes. In contrast to alkanes on Au(111) surfaces, for which no SAMs on an unreconstructed gold substrate were observed, alkanols are capable of forming SAMs on either the reconstructed or the unreconstructed gold surfaces. Structural models for the packing of alkanol molecules on Au(111) surfaces have been proposed, which successfully explain these experimental observations.
Collapse
Affiliation(s)
- Hai-Ming Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, Xiamen University, Xiamen 361005, China
| | | | | | | | | |
Collapse
|
26
|
Müller T, Werblowsky TL, Florio GM, Berne BJ, Flynn GW. Ultra-high vacuum scanning tunneling microscopy and theoretical studies of 1-halohexane monolayers on graphite. Proc Natl Acad Sci U S A 2005; 102:5315-22. [PMID: 15758073 PMCID: PMC556233 DOI: 10.1073/pnas.0409576102] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A simple model system for the 2D self-assembly of functionalized organic molecules on surfaces was examined in a concerted experimental and theoretical effort. Monolayers of 1-halohexanes were formed through vapor deposition onto graphite surfaces in ultrahigh vacuum. Low-temperature scanning tunneling microscopy allowed the molecular conformation, orientation, and monolayer crystallographic parameters to be determined. Essentially identical noncommensurate monolayer structures were found for all 1-halohexanes, with differences in image contrast ascribed mainly to electronic factors. Energy minimizations and molecular dynamics simulations reproduced structural parameters of 1-bromohexane monolayers quantitatively. An analysis of interactions driving the self-assembly process revealed the crucial role played by small but anisotropic electrostatic forces associated with the halogen substituent. While alkyl chain dispersion interactions drive the formation of a close-packed adsorbate monolayer, electrostatic headgroup forces are found to compete successfully in the control of both the angle between lamella and backbone axes and the angle between surface and backbone planes. This competition is consistent with energetic tradeoffs apparent in adsorption energies measured in earlier temperature-programmed desorption studies. In accordance with the higher degree of disorder observed in scanning tunneling microscopy images of 1-fluorohexane, theoretical simulations show that electrostatic forces associated with the fluorine substituent are sufficiently strong to upset the delicate balance of interactions required for the formation of an ordered monolayer. The detailed dissection of the driving forces for self-assembly of these simple model systems is expected to aid in the understanding of the more complex self-assembly processes taking place in the presence of solvent.
Collapse
Affiliation(s)
- Thomas Müller
- Department of Chemistry and Columbia Materials Research Science and Engineering Center, Columbia University, New York, NY 10027, USA
| | | | | | | | | |
Collapse
|