| Abstract
| - The chemical stability of electrochemically alkylated porous silicon is studied. The hydride-terminatedsurface of p-type or p++-type porous silicon is stabilized by electrochemical reduction of organohalides inacetonitrile solutions. Reduction of 6-iodo-ethylhexanoate, 1-iodo-6-(trifluoroacetylamino)hexane, iodomethane, 1-bromohexane, or ethyl 4-bromobutyrate at a porous Si cathode results in removal of thehalogen and attachment of the organic fragment to the porous Si surface via a Si−C bond. A two-stepprocedure involving attachment of the functional group of interest followed by attachment of methylgroups (by reduction of iodomethane) to residual, more sterically inaccessible sites on the porous Si surfaceis found to yield a more stable material. Three tests of the chemical stability of the modified surfaces areperformed: treatment with dimethyl sulfoxide (a chemical oxidant for porous Si), treatment with aqueousCu2+, and exposure to 10% ethanol in a solution of phosphate buffered (pH = 7.4) aqueous saline. Thereactions are characterized by atomic force microscopy, Fourier transform infrared (FT-IR) and opticalreflectivity spectroscopies. The data indicate that electrochemical alkylation greatly improves the stabilityof porous Si against oxidation and corrosion, and that the methyl capping procedure provides the moststable material.
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