Characterization of thiol self-assembled films by laser desorption Fourier transform mass spectrometry

Li, Yunzhi; Huang, Jingyu; McIver, Robert T.; Hemminger, John C.

doi:10.1021/ja00033a018

Cited by 203 publications

(191 citation statements)

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“…Previous results from ellipsometry and x-ray photoelectron spectroscopy have found preferential adsorption of longer chain alkanethiols from mixed thiol solutions. 22 Previous mass spectrometric studies using direct laser desorption 11,12 and TOFSIMS 7-10 demonstrated only the monomer species as the parent ion. The direct laser desorption results can be reconciled with our results in the following manner: low-energy electrons, that are formed by UV photoemission from the Au surface, are subsequently attached to the laser-desorbed dimer neutrals, leading to dissociation to form RS -monomer ions.…”

Section: Resultsmentioning

confidence: 99%

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Laser Desorption/Vacuum Ultraviolet Photoionization of Alkanethiolate Self-assembled Monolayers

Trevor

Hanley

Lykke

1997

Rapid Commun. Mass Spectrom.

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Self-assembled monolayers of straight-chain alkanethiolates (RS) on gold were studied by nitrogen laser desorption followed by vacuum ultraviolet (118 nm) photoionization of secondary neutrals in a time-of-flight mass spectrometer. The dominant feature of all photoionization mass spectra were the dimers (RSSR + ) for all thiolates studied. No monomer ions (RS + ) were observed, in contrast with previous results from time-of-flight secondary ion and direct laser desorption mass spectrometry. Results are presented from experiments on the tetradecyl (C 14 ) and hexadecyl (C 16 ) mercaptan monolayers. Mixed C 14 /C 16 monolayers generated both pure and mixed dimers, indicating a facile association between different monomer chain lengths. © 1997 by John Wiley & Sons, Ltd. Received 23 January 1997; Accepted 12 February 1997; Rapid. Commun. Mass Spectrom. 11, 587-589 (1997) Self-assembled monolayers (SAMs) have been intensely studied owing to their ability to form stable, well ordered molecular arrays on surfaces. Their ability to be further functionalized into layers of ordered molecules has promised applications in the fields of chemical sensing, lithography and molecular-based electronics.1 These robust molecules have also been extensively studied as model organic surfaces for fundamental studies of molecular adsorption, wetting and electron transfer.2 Understanding the interaction of alkanethiols with noble metal surfaces has been addressed by several experimental methods.3,4 These methods indicate that SAMs form densely packed, crystalline-like assemblies on the surface: straight-chain alkanethiols chemisorbed on Au(111) adopt a (z √3 × √3)R30° (z = 1-6) overlayer lattice with the carbon chains tilted 30° off the surface normal at saturation coverages.5 These structures have average domain sizes of 5-20 nm and can adopt a series of different phases at lower coverages and under different surface preparation conditions. 6Various mass spectrometric methods have also been applied to alkanethiolate SAMs. Thermal desorption mass spectrometry was originally used to demonstrate that alkanethiols (RSH) form SAMs by cleaving their S -H bond and chemisorbing as thiolates.5 Several studies 7-10 of thiols and disulfides on gold with time-offlight secondary ion mass spectrometry (TOFSIMS) in the negative-and positive-ion modes detected these thiolates as the real or pseudo-molecular ion of the monomer (i.e., RS ± , RSX ± or related species). Direct (single) laser desorption mass spectrometry has also been used to examine SAMs and has detected negative monomer ions. 11,12 In contrast, a recent thermal desorption mass spectrometry study of octadecanethiolate monolayers observed dimer ions (RSSR + ) using electron ionization of desorbed neutrals. 13In this work, we used laser desorption/118 nm singlephoton ionization TOFMS to examine straight-chain alkanethiolate SAMs on gold. Soft ionization by singlephoton ionization allows the major ion channel to be observed. We present here results for tetradecanethiol (C 14 ), hexadecanet...

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Section: Resultsmentioning

confidence: 99%

“…Direct (single) laser desorption mass spectrometry has also been used to examine SAMs and has detected negative monomer ions. 11,12 In contrast, a recent thermal desorption mass spectrometry study of octadecanethiolate monolayers observed dimer ions (RSSR + ) using electron ionization of desorbed neutrals. …”

mentioning

confidence: 88%

Laser Desorption/Vacuum Ultraviolet Photoionization of Alkanethiolate Self-assembled Monolayers

Trevor

Hanley

Lykke

1997

Rapid Commun. Mass Spectrom.

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“…Hemminger and coworkers first demonstrated that negative ions of SAMs can be formed by direct laser desorption. 44 Negative ions can only be formed with laser wavelengths shorter than 337 nm, indicating that the thermally desorbed neutrals are ionized by attachment of photoemitted electrons. 4 This mechanism of negative ion formation works well in the case of self-assembled monolayers, but is not a general method of analysis.…”

Section: Ion Formation During Single-laser Desorptionmentioning

confidence: 99%

Surface mass spectrometry of molecular species

et al. 1999

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“…Involvement of alkylthiolates (RS ± ) in Equation 1 is inferred by the formation of indistinguishable monolayers from the alkane thiols and dialkyl disulfides of the same hydrocarbon chains, [173] and substantiated by FTIR, [174] FTIR±mass spectrometry, [175] Raman spectroscopy, [176,177] XPS, [178±180] and electrochemical [181] measurements. However, no evidence has been obtained for the formation of molecular hydrogen.…”

Section: Self-assembled Monolayers (Sams)mentioning

confidence: 99%

Reflection and Absorption Techniques for Optical Characterization of Chemically Assembled Nanomaterials

Roy

Fendler²

2004

Advanced Materials

123

122

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This review discusses recent developments in the areas of fabrication, certain types of optical characterization, and applications of a selected class of chemically assembled nanomaterials, namely i) gold and silver nanoparticles deposited onto optically transparent glass substrates; ii) thiol‐functionalized self‐assembled monolayers (SAMs); iii) chemically stabilized gold and silver nanoparticles (monolayer protected clusters, MPCs); and iv) MPCs linked to metallic substrates and adsorbates. Six linear optical techniques for the characterization of these materials are discussed: transmission localized surface plasmon resonance spectroscopy, T‐LSPR; propagating surface plasmon resonance spectroscopy, P‐SPR; polarization‐selective Fourier transform infrared reflection absorption spectroscopy, PS‐FTIRRAS; polarization‐modulation Fourier transform infrared reflection absorption spectroscopy, PM‐FTIRRAS; surface‐enhanced infrared reflection absorption spectroscopy, SEIRRAS; and infrared ellipsometry. The review focuses particularly on providing a unified treatment of these six optical techniques by using a relatively simple stratified multilayer model.

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Characterization of thiol self-assembled films by laser desorption Fourier transform mass spectrometry

Cited by 203 publications

References 1 publication

Laser Desorption/Vacuum Ultraviolet Photoionization of Alkanethiolate Self-assembled Monolayers

Laser Desorption/Vacuum Ultraviolet Photoionization of Alkanethiolate Self-assembled Monolayers

Surface mass spectrometry of molecular species

Reflection and Absorption Techniques for Optical Characterization of Chemically Assembled Nanomaterials

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