HREELS characterization of surfaces and interfaces in self-assembled molecular monolayers

Vilar, M. Rei; Bouali, Y; Kitakatsu, N.; Lang, P.; Michalitsch, Richard; Garnier, F.; Dubot, Pierre

doi:10.1016/s0040-6090(98)00636-1

Cited by 13 publications

(8 citation statements)

References 9 publications

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“…Molecular Self-Assembly and Orientation by IR Spectroscopy. IRRAS Spectra of CH 3 (CH 2 ) 9 -SH and CH 3 (CH2) 17 -SH on Zn. To characterize the organization of the monolayer and the interaction between the alkyl chains, IRRAS spectroscopy was performed on Zn platelets.…”

Section: Resultsmentioning

confidence: 99%

“…The character of the bond created between the SAM and the substrate is governed by both the nature of the surface and the reactive group of the molecules. In particular, thiol moieties have a high affinity toward metals (oxidation state 0) such as Au − or Ag, , Pt, − Cu, − Al, , Fe, , Ni, − Ti, and Zn. , More recently, thiols have been adsorbed onto nonmetallic substrates: GaAs, InP, ITO, − and ZnSe . Because of their intrinsic properties, SAMs provide an original path for surface modification and open up new perspectives for applications in materials science.…”

Section: Introductionmentioning

confidence: 99%

“…The character of the bond created between the SAM and the substrate is governed by both the nature of the surface and the reactive group of the molecules. In particular, thiol moieties 4 have a high affinity toward metals (oxidation state 0) such as Au [5][6][7][8][9][10] or Ag, 11,12 Pt, [13][14][15][16][17][18] Cu, [19][20][21][22][23] Al, 24,25 Fe, 26,27 Ni, [28][29][30] Ti, 31 and Zn. 32,33 More recently, thiols have been adsorbed onto nonmetallic substrates: GaAs, 34 InP, 35 ITO, [36][37][38] and ZnSe.…”

Section: Introductionmentioning

confidence: 99%

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Self-Assembled Alkanethiol Monolayers on a Zn Substrate: Structure and Organization

Noguès

Lang

2007

Langmuir

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This work concerns a first step toward the use of self-assembled monolayers derived from thiols as coupling layers between a zinc surface and organic coatings. The adsorption, structure, and aging of alkanelthiol monolayers on zinc substrates have been studied by contact angle measurements, infrared spectroscopy, and electrochemistry. The thiols self-assemble on the zinc surface to form a highly hydrophobic monolayer. The molecules are well organized with very few gauche defects, oriented nearly normal to the surface, and protect the zinc from oxidation in a neutral aqueous medium.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The character of the bond created between the SAM and the substrate is governed by both the nature of the surface and the reactive group of the molecules. In particular, thiol moieties 4 have a high affinity toward metals (oxidation state 0) such as Au [5][6][7][8][9][10] or Ag, 11,12 Pt, [13][14][15][16][17][18] Cu, [19][20][21][22][23] Al, 24,25 Fe, 26,27 Ni, [28][29][30] Ti, 31 and Zn. 32,33 More recently, thiols have been adsorbed onto nonmetallic substrates: GaAs, 34 InP, 35 ITO, [36][37][38] and ZnSe.…”

Section: Introductionmentioning

confidence: 99%

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Self-Assembled Alkanethiol Monolayers on a Zn Substrate: Structure and Organization

Noguès

Lang

2007

Langmuir

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“…Two approaches have emerged for forming SAMs on Pt surfaces. The first approach attempts to avoid surface oxidation by minimizing exposure of samples to oxygen: deoxygenating solvents, handling samples in inert atmosphere, etc. − In the second approach, no explicit attempt is made to control the oxidation, and the deposition is carried out under more typical laboratory conditionsPt cleaning by mechanical polishing or in a piranha solution, followed by alkanethiol deposition from an ethanolic solution. In this report, we use standard techniques to characterize the formation and longevity of alkanethiol SAMs on Pt under ambient conditions, in part to provide a direct comparison between SAMs on Au and those on Pt.…”

Section: Introductionmentioning

confidence: 99%

Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers

et al. 2006

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We have studied the formation of self-assembled monolayers (SAMs) of n-alkanethiols on platinum thin films using X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and contact angle (CA) measurements. Specifically, SAMs of 1-hexanethiol, 1-dodecanethiol, and 1-octadecanethiol were grown on polycrystalline Pt films, and the effects of Pt surface preparation, deposition conditions, and solvent treatments on the initial quality and stability of the monolayer in air were investigated. The SAMs prepared under ambient conditions on piranha-cleaned and UV/ozone-cleaned substrates were compared to monolayers formed on template-stripped Pt in an inert atmosphere. We found that alkanethiols deposited from 1 mM ethanolic solutions on piranha-cleaned Pt formed densely packed monolayers in which alkyl chains were oriented close to the surface normal. Stored in the laboratory ambient, these monolayers were unchanged over about 1 week but were largely oxidized in about 1 month. No evidence was found of molecules being weakly bound within the monolayer or having undergone C-S bond scission; however, three distinct sulfur states were observed for all samples in the XPS of the S 2p region. The lowest-and highest-binding-energy components are assigned to alkylthiolate and partially oxidized alkylthiolate species, respectively. The remaining S 2p component (approximately one-third of the sulfur layer), intermediate in binding energy between the other two components, is attributed to a chemisorbed species with a S binding configuration distinct from the majority alkylthiolate: for example, S bound to Pt bound to O, S with a different Pt coordination number, or S in an adsorbed disulfide.

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“…Thus, surface analysis techniques can give a good contribution to the study of SAMs whereas traditional methods requiring a more significant amount of matter are quite inefficient. In the last years, HREELS has been revealed as an exceptionally useful tool for this kind of investigation . Being one of the most surface sensitive spectroscopic techniques, HREELS can respond to the SAM analysis requirements: chemical nature of the functionalized surface (chains versus thienyl moieties); molecular orientation; organized domain size; surface electronic excitations.…”

Section: Introductionmentioning

confidence: 99%

HREELS Study of Self-Assembled Monolayers of Alkylthiols Functionalized with Oligothiophene Moieties: Extreme Surface Analysis and Evidence for Intermolecular Interactions

Vilar¹,

Lang²,

Horowitz³

et al. 2003

Langmuir

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SAMs (self-assembled monolayers) of alkanethiols functionalized by R-terthienyl (3T-SAMs) and R-quaterthienyl (4T-SAMs) were formed on a gold surface presenting (111) terraces and studied by highresolution electron energy loss spectroscopy (HREELS). The angular width of the elastic peak leads to a domain size of ca. 90 Å, comparable to that of the Au(111) terraces of the substrate. Enhancement of the spectral resolution by using a new generation spectrometer enables the improvement of the spectral analysis in the energy range of the vibrational losses. A detailed analysis of the differential cross sections of the different vibrational peaks indicates the nature of their mechanisms: impact mechanisms show that the extreme surface of the monolayers is mainly constituted by thienyl moieties with the thienyl density in 3T-SAMs higher than that in 4T-SAMs; dipolar mechanisms show that molecules are standing up slightly tilted on the substrate; a resonance via a negative ion formation was detected around 4.5 eV. On the other hand, the electronic excitation domain leads to excitonic gap values of 2.62 ( 0.08 and 2.90 ( 0.08 eV for 4T-SAMs and 3T-SAMs, respectively. A sharp feature located at 0.28 ( 0.08 above the electronic threshold was detected in the 3T-SAM spectra. This feature, also appearing in the spectra of the R-oligothiophene evaporated films, is here assigned to a vibronic excitation. Its intensity is always related to the organization degree of the SAMs. An additional band without equivalence in the optical spectra appearing in the 4T-SAM and 3T-SAM HREELS spectra with thresholds at 3.58 ( 0.08 and 4.15 ( 0.08 eV, respectively, is assigned to the electronic gap. The values of the excitonic and electronic gaps are well correlated with those found in the corresponding spectra of evaporated R-quaterthiophene, R-quinquethiophene, and R-sexithiophene films formerly studied. These results lead to the conclusion that thienyl functionalities present strong intermolecular interactions.

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HREELS characterization of surfaces and interfaces in self-assembled molecular monolayers

Cited by 13 publications

References 9 publications

Self-Assembled Alkanethiol Monolayers on a Zn Substrate: Structure and Organization

Self-Assembled Alkanethiol Monolayers on a Zn Substrate: Structure and Organization

Alkanethiols on Platinum: Multicomponent Self-Assembled Monolayers

HREELS Study of Self-Assembled Monolayers of Alkylthiols Functionalized with Oligothiophene Moieties: Extreme Surface Analysis and Evidence for Intermolecular Interactions

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