Organic Functionalization of Porous Silicon via Hydrosilylation Pathways

Organic Functionalization of Porous Silicon via Hydrosilylation Pathways: Probing Monolayer Stability through Desorption/Degradation Studies Lon A. Porter, Jr. , Department of Chemistry, Wabash College, Crawfordsville, IN 47933 Surface Chemistry on Nanostructured Silicon: Borrowing from solution phase synthetic methods, a selection of hydrosilylation reactions has been recently reported for functionalizing organic groups onto oxide-free, hydride-terminated silicon surfaces. All of these methods result in the formation of stable monolayers which protect the underlying silicon surface from ambient oxidation and chemical attack. However, no direct comparison of monolayer stability resulting from these diverse mechanisms has been reported. Monolayer Stability Studies via FTIR: While unfunctionalized control samples oxidize and degrade in a window of hours, alkyl functionalized porous silicon samples remain largely unaffected for weeks in simulated acellular plasma (blood). Control samples exhibit little oxidation in simulated gastric fluid, yet oxidize quickly in the presence of the simulated intestinal fluid. In each of the four reactions pathways tested, the stability of the underlying silicon substrate was greatly improved after alkyl functionalization in comparison to the unfunctionalized control. Preliminary data suggests that thermal, mircowave, and Lewis acid mediated reactions afford a higher level of protection against oxidation than the carboncation route. This is most likely due to some chemisorption of the trityl species.