Silicon Modification with Molecules Derived from Ferrocene: Effect of the Crystallographic Orientation of Silicon in the Electron–Transfer Rates

Riveros, G.; Garín, Carolina; Meneses, S; Escobar, Sebastián

doi:10.1080/15421401003722559

Cited by 2 publications

(2 citation statements)

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“…Ferrocene has been widely used as a model system for understanding charge transfer across molecular interfaces to electrodes. 11−13,15,16,22,24−26,37,39−55 Most measurements of electron transfer rates across molecular layers have used self-assembled monolayers on metal surfaces, especially gold 10−26 while fewer studies have investigated electron transfer rates on covalently bonded substrates such as silicon, 46,49,50,52,53,56 conductive oxides, 51 or carbon-based electrodes. 44,48 An important distinction between metallic and nonmetallic substrates is that while on coinage metals adsorbed molecules are able to diffuse laterally to achieve dense, crystalline monolayers, once molecules are bonded onto covalent materials such as silicon and diamond they generally cannot diffuse at room temperature.…”

Section: ■ Introductionmentioning

confidence: 99%

“…A key question in the formation of redox-active surfaces is the electronic nature of the molecular tether linking the electroactive group to the surface. Ferrocene has been widely used as a model system for understanding charge transfer across molecular interfaces to electrodes. − ,,,,− ,,− Most measurements of electron transfer rates across molecular layers have used self-assembled monolayers on metal surfaces, especially gold − while fewer studies have investigated electron transfer rates on covalently bonded substrates such as silicon, ,,,,, conductive oxides, or carbon-based electrodes. , An important distinction between metallic and nonmetallic substrates is that while on coinage metals adsorbed molecules are able to diffuse laterally to achieve dense, crystalline monolayers, once molecules are bonded onto covalent materials such as silicon and diamond they generally cannot diffuse at room temperature. Furthermore, the distance between adjacent surface sites is not well matched to the optimum 5 Å spacing between ordered alkyl chains. − Consequently, molecular layers on covalent materials are typically less well-ordered than those on gold.…”

Section: Introductionmentioning

confidence: 99%

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Conformational Disorder Enhances Electron Transfer Through Alkyl Monolayers: Ferrocene on Conductive Diamond

2013

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We have investigated the electron-transfer kinetics of ferrocene groups covalently tethered to surfaces of conductive diamond electrodes. Electrochemical measurements show that the rates are only weakly dependent on chain length but are strongly dependent on the surface coverage; these observations are contrary to what is commonly observed for self-assembled monolayers on gold, pointing to important mechanistic differences in electron transfer processes on covalently bonded materials. Molecular dynamics simulations show that dependence on chain length and molecular density can be readily explained in terms of dynamic crowding effects. At low coverage, conformational flexibility of surface-tethered alkyl chains allows the redox-active ferrocene group to dynamically approach the diamond surface, leading to facile electron transfer for all surface molecules. As the coverage is increased, steric crowding causes the average ferrocene-to-surface distance to increase, decreasing the electron transfer rate. Even at the most dense packings, the mismatch between the spacing of surface lattice sites and the optimum alkyl chain density leads to voids and inherent disorder that facilitates electron transfer. These results are significant in the design and optimization of electrocatalytically active surfaces on covalently bonded materials relevant for electro- and photocatalysis.

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