Conformation of Alkanethiols on Au, Ag(111), and Pt(111) Electrodes: A Vibrational Spectroscopy Study

Hines, Margaret A.; Todd, J. A.; Guyot‐Sionnest, Philippe

doi:10.1021/la00002a022

Cited by 105 publications

(117 citation statements)

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“…1 (top, solid line) with five resonance components (bottom, solid lines). The SFG spectrum is in agreement with that previously reported [3,12,13]. Three dominant peaks attributed to CH3 group of ODT monolayer were observed.…”

Section: Methodssupporting

confidence: 91%

Conformational Order of Octadecanethiol (ODT) Monolayer at Gold/Solution Interface: Internal Reflection Sum Frequency Generation (SFG) Study

Nihonyanagi

Fujishima

et al. 2001

Studies in Surface Science and Catalysis

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Section: Methodssupporting

confidence: 91%

Conformational Order of Octadecanethiol (ODT) Monolayer at Gold/Solution Interface: Internal Reflection Sum Frequency Generation (SFG) Study

Nihonyanagi

Fujishima

et al. 2001

Studies in Surface Science and Catalysis

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“…8 Hines et al have shown that alkanethiolate SAMs on gold and silver are relatively more ordered than those prepared on platinum; however, the latter can be "straightened" by applying electrochemical potentials. 9 Yeganeh et al discovered that SFG spectra of alkanethiolate monolayers on a gold(111) surface exhibit an azimuthal angle dependence and attributed this behavior to the binding pattern of the molecules. 16 Liu et al studied the role of water during the adsorption of OTS on a fused silica surface by monitoring conformational changes of the monolayers.…”

Section: Introductionmentioning

confidence: 99%

Probing the Molecular Conformation of Self-Assembled Monolayers at Metal/Semiconductor Interfaces by Vibrational Sum Frequency Generation Spectroscopy

et al. 2009

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The conformation of self-assembled monolayers (SAMs) buried at metal-semiconductor interfaces plays a crucial role in the functioning of the molecular junctions thus formed. We have studied by vibrational sum frequency generation (SFG) spectroscopy the influence of deposited gold films on the molecular orientation of a series of n-alkyl monolayers that are covalently bonded to silicon(111) via Si-C linkages (≡Si-C n H 2n+1 , n ) 10, 12, 14, and 18). The SFG spectra indicate that the gold contacts (overlayers) introduce significant gauche defects within the initially highly oriented alkyl chains. The methyl tilt angles of the buried n-alkyl monolayers depend on the gold deposition method (vacuum evaporation vs sputtering) and the alkyl chain length. These observations are supported by solid-state electrical measurements.

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“…Although a very powerful technique, the analysis of SFG spectra becomes complicated when several interfaces exist in the same system, which might occur in an organic multilayer in a biological system such as lung surfactant, since more than one of them may be SFG active. The interpretation is further complicated when different supporting substrates are used because these can have nonresonant responses of different magnitudes depending on the electromagnetic interaction between the laser light and the substrate [9][10][11]. Our fundamental understanding of the nonlinear optical response from multiple interface systems is still very limited and the development of a rigorous physical model is an essential prerequisite if the technique is to be meaningfully used for more complex systems.…”

mentioning

confidence: 99%

Optical Sum-Frequency Emission from Langmuir-Blodgett Films of Variable Thickness: Effects of the Substrate and Polar Orientation of Fatty Acids in the Films

et al. 2006

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The nonlinear optical response arising from a model multilayer structure, i.e., Langmuir-Blodgett (LB) films comprised of different numbers of per-protonated (H) and per-deuterated (D) fatty acid layers on solid substrates, has been evaluated by sum-frequency generation (SFG) spectroscopy. The SFG signals depend significantly on the absolute polar orientation of the fatty acids in the individual layers and on the nonlinear optical response of the substrate. The SFG spectra on gold and fused quartz substrates demonstrate a totally different dependence on the number of the contributing H layers, which it is possible to analyze quantitatively. The results provide important information for understanding the origin of the nonlinear optical responses from ordered systems composed of multiple interfaces and therefore for extracting exact structural information about each interface from the observed SFG signals. DOI: 10.1103/PhysRevLett.96.077402 PACS numbers: 78.67.Pt, 42.65.ÿk, 68.47.Pe Ultrathin organic films are the fundamental molecular building blocks of cell membranes, bilayers, and vesicles and consequently of great interest to physicists and biologists alike [1]. They are also the essential components of many nanotechnologies. For example, it is possible to control the size and shape of nanoparticles by using a fatty acid film as a restraining matrix. Although it is believed that the functionalities of organic films depend significantly on their interfacial molecular structures, there is a paucity of such structural information available due to a lack of effective experimental probes, particularly ones capable of operating under ambient conditions. The inherent structural information available from vibrational spectra, hitherto obtained from IR or Raman spectroscopy, has been greatly extended by the introduction of sumfrequency generation (SFG), a 2nd-order nonlinear optical process in which two laser beams at frequencies ! 1 and ! 2 impinge on a medium, mix and generate a sum-frequency output at ! s ! 1 ! 2 [2]. Usually, vibrational SFG spectrum is achieved using a fixed frequency visible laser beam (! 1 ) and a tunable frequency infrared laser beam (! 2 ). The intensity of SFG is enhanced when ! 2 coincides with a vibrational transition of the interfacial species. By this means a vibrational spectrum of the interface is obtained upshifted into the visible or UV region of the spectrum. SFG is forbidden in a bulk medium with inversion symmetry and only occurs at a surface or interface where the inversion symmetry is necessarily broken. As a surface sensitive probe, SFG offers several advantages over traditional infrared and Raman spectroscopic techniques due to its extremely high surface specificity and sensitivity [2,3]. Consequently, it is now widely employed for investigating the molecular structure of various surfaces and interfaces comprised of organic thin films such as selfassembled monolayers (SAMs), Langmuir-Blodgett (LB) films, as well as thin polymer films [4 -8]. Although a very powerful techniq...

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Conformation of Alkanethiols on Au, Ag(111), and Pt(111) Electrodes: A Vibrational Spectroscopy Study

Cited by 105 publications

References 1 publication

Conformational Order of Octadecanethiol (ODT) Monolayer at Gold/Solution Interface: Internal Reflection Sum Frequency Generation (SFG) Study

Conformational Order of Octadecanethiol (ODT) Monolayer at Gold/Solution Interface: Internal Reflection Sum Frequency Generation (SFG) Study

Probing the Molecular Conformation of Self-Assembled Monolayers at Metal/Semiconductor Interfaces by Vibrational Sum Frequency Generation Spectroscopy

Optical Sum-Frequency Emission from Langmuir-Blodgett Films of Variable Thickness: Effects of the Substrate and Polar Orientation of Fatty Acids in the Films

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