title: Silicon (100) electrodes resistant to oxidation in aqueous solutions: an unexpected benefit of surface acetylene moieties.
abstract: Here we report on the functionalization of alkyne-terminated alkyl monolayers on highly doped Si(100) using "click" reactions to immobilize ferrocene derivatives. The reaction of hydrogen-terminated silicon surfaces with a diyne species was shown to afford very robust functional surfaces where the oxidation of the underlying substrate was negligible. Detailed characterization using X-ray photoelectron spectroscopy, X-ray reflectometry, and cyclic voltammetry demonstrated that the surface acetylenes had reacted in moderate yield to give surfaces exposing ferrocene moieties. Upon extensive exposure of the redox-active architecture to oxidative environments during preparative and characterization steps, no evidence of SiOx contaminants was shown for derivatized SAMs prepared from single-component 1,8-nonadiyne, fully acetylenylated, monolayers. An analysis of the redox behavior of the prepared Si(100) electrodes based on relevant parameters such as peak splitting and position and shape of the reduction/oxidation waves depicted a well-behaved redox architecture whose spectroscopic and electrochemical properties were not significantly altered even after prolonged cycling in aqueous media between -100 and 800 mV versus Ag|AgCl. The reported strategy represents an experimentally simple approach for the preparation of silicon-based electrodes where, in addition to close-to-ideal redox behavior, remarkable electrode stability can be achieved. Both the presence of a distal alkyne moiety and temperatures of formation above 100 degrees C were required to achieve this surface stabilization.
authors.affiliation: School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Simone
authors.initials: S
authors.lastname: Ciampi
authors.forename: Paul K
authors.initials: PK
authors.lastname: Eggers
authors.forename: Guillaume
authors.initials: G
authors.lastname: Le Saux
authors.forename: Michael
authors.initials: M
authors.lastname: James
authors.forename: Jason B
authors.initials: JB
authors.lastname: Harper
authors.forename: J Justin
authors.initials: JJ
authors.lastname: Gooding
mesh_terms: D000114:Acetylene / Q000737:chemistry*; D004566:Electrodes; D006859:Hydrogen / Q000737:chemistry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D012825:Silicon / Q000737:chemistry*; D012996:Solutions; D013057:Spectrum Analysis; D013499:Surface Properties
chemical_list: D012996:Solutions; D006859:Hydrogen; D000114:Acetylene; D012825:Silicon