The structure of self-assembled monolayers of alkylsiloxanes on silicon: a comparison of results from ellipsometry and low-angle x-ray reflectivity

Wasserman, S.R.; Whitesides, George M.; Tidswell, I. M.; Ocko, B. M.; Pershan, Peter S.; Axe, J.D.

doi:10.1021/ja00197a054

Cited by 436 publications

(410 citation statements)

References 3 publications

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“…17 Å). Small systematic differences between XRR and ellipsometry data have been previously reported, 35 and do not constitute a reason of concern. 36 2.1.3 Derivatization of SAMs incorporating the redoxswitchable molecule 2.…”

Section: Assembly Of Surface Constructssupporting

confidence: 53%

The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes

Ciampi

James

Choudhury

et al. 2013

Phys. Chem. Chem. Phys.

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. (2013). The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes. Physical Chemistry Chemical Physics, 15 (24), 9879-9890.The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes AbstractIn this paper we explore a multi-step synthetic strategy toward fabrication of monolayer-modified Si(100) electrodes that can be electrochemically switched. The synthetic scheme is modular and benefits from an established intramolecular lactonization scheme of benzoquinone analogs. A redox-tagged pendant group can be released from the surface such as to allow for in situ monitoring of the switch process. We show that this model system can be used to elucidate chemical and structural events for a surface dynamic system that is rapidly gaining popularity. The influence of polarization times, overpotentials and semiconductor doping type on the kinetic of the switch event is also investigated. In both basic and acidic aqueous electrolytes the release of suitable redox-active markers is found to require unexpectedly large cathodic overpotentials. The release event is accompanied by minor oxidation of the electrode surface and the switched constructs can be regenerated by chemical means with no appreciable deterioration of surface quality. 2013 the Owner Societies. The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes † Simone Ciampi, a Michael James,z b Moinul H. Choudhury, a Nadim A. Darwish a and J. Justin Gooding* aIn this paper we explore a multi-step synthetic strategy toward fabrication of monolayer-modified Si(100) electrodes that can be electrochemically switched. The synthetic scheme is modular and benefits from an established intramolecular lactonization scheme of benzoquinone analogs. A redox-tagged pendant group can be released from the surface such as to allow for in situ monitoring of the switch process. We show that this model system can be used to elucidate chemical and structural events for a surface dynamic system that is rapidly gaining popularity. The influence of polarization times, overpotentials and semiconductor doping type on the kinetic of the switch event is also investigated.In both basic and acidic aqueous electrolytes the release of suitable redox-active markers is found to require unexpectedly large cathodic overpotentials. The release event is accompanied by minor oxidation of the electrode surface and the switched constructs can be regenerated by chemical means with no appreciable deterioration of surface quality.

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Section: Assembly Of Surface Constructssupporting

confidence: 53%

The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes

Ciampi

James

Choudhury

et al. 2013

Phys. Chem. Chem. Phys.

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“…well-established techniques for forming and characterizing them, [231][232][233][234][235][236][237] and in principle, their chemistry should be less complex and therefore more amenable to obtaining detailed molecular level insights. SAMs formed by reaction of trichloroalkylsilanes on SiO x surfaces, for example on the thin oxide layer on silicon, may be particularly relevant to reactions of organic compounds on dust and on building materials for which silicates can be major components.…”

Section: This Journal Is C the Owner Societies 2009mentioning

confidence: 99%

“…First, there was evidence for some multilayer formation on the ZnSe ATR crystal, which may be partly responsible for significantly more scatter in the kinetics data than is the case using a silicon ATR crystal where monolayer formation is well characterized. [231][232][233][234][235][236][237] Second, it may be that the mechanism of formation of CQO is not, indeed, L-H but rather a more complex one that leads to a similar parameterization of the rate data. Given the lack of a convincing mechanism that would lead to L-H kinetics for the disparate surfaces for which it has been suggested, it is clear that much more remains to be understood at a molecular level about the interaction of O 3 , and likely of other oxidants as well, with organics at interfaces.…”

Section: This Journal Is C the Owner Societies 2009mentioning

confidence: 99%

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

Finlayson-Pitts

2009

Phys. Chem. Chem. Phys.

229

272

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“…21 The advancing and receding contact angles of water on the SAMs of OTS of 110Ϯ2 and 97Ϯ2°, as well as the advancing contact angle of hexadecane on the SAMs of OTS of 43Ϯ2°, agreed well with literature values. [22][23][24][25][26] The advancing contact angles of water on 1Cl and 2Cl films at saturation coverage also were measured, and they were 102Ϯ3 and 105Ϯ3°, respectively. The advancing contact angles for all the n-alcohols used in the friction measurements also were measured on SAMs of OTS.…”

Section: Measurement Of Contact Anglesmentioning

confidence: 99%

The effect of chain density on the frictional behavior of surfaces modified with alkylsiloxanes and immersed in n-alcohols

Clear

Nealey

2001

The Journal of Chemical Physics

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Concepts of viscoelastic behavior of bulk polymer systems were used to describe maxima in the friction behavior of self-assembled monolayers ͑SAMs͒ measured with lateral force microscopy ͑LFM͒ as a function of sliding velocity and applied normal load in the presence of solvents ͑plasticizers͒. The objective of this study was to investigate whether decreases in the chain density of the SAMs caused maxima in the friction force to shift to higher sliding velocities; such a shift is indicative of shorter chain relaxation times in less dense, less ordered SAMs. Complete SAMs were formed from octadecyltrichlorosilane ͑OTS͒ and partial SAMs were formed from n-octadecylmethyldichlorosilane ͑2Cl͒ and n-octadecyldimethyldichlorosilane ͑1Cl͒, all on silicon/silicon dioxide substrates. With decreasing chain density, solvent partitioning into the monolayer should increase as OTSϽ2ClϽ1Cl. In butanol and pentanol, the maxima in the friction force shifted to higher sliding velocities with decreasing chain density, and the relaxation times calculated for the partial 2Cl films were an order of magnitude shorter than those for SAMs of OTS. For both SAMs of OTS and 2Cl films, maxima shifted to lower sliding velocities with increases in the applied normal load and with increases in the chain length n of the solvent. The higher compressibility of 2Cl films caused greater shifts in the maxima for similar increases in the applied normal load. The increase with n was consistent with both a mechanism of solvent partitioning controlled by the free volume distribution in the SAM and a mechanism of insertion. The relaxation times of the alkyl chains were related to a molecular model of energy dissipation involving the adsorption and desorption of the chain ends to and from the surface of the probe tip.

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The structure of self-assembled monolayers of alkylsiloxanes on silicon: a comparison of results from ellipsometry and low-angle x-ray reflectivity

Cited by 436 publications

References 3 publications

The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes

The detailed characterization of electrochemically switchable molecular assemblies on silicon electrodes

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

The effect of chain density on the frictional behavior of surfaces modified with alkylsiloxanes and immersed in n-alcohols

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