4 - Photochemical and nonthermal chemical modification of porous silicon for biomedical applications

Abstract

Hydrogen-terminated silicon (Si) in the form of single crystals, nanocrystalline porous silicon (PSi), or nanoparticles is fairly unreactive. Thermal reactions often require high temperatures and long reaction times to induce significant reaction. Photochemical and nonthermal activation open up a number of reaction pathways in controlled and mild conditions. Substitution of hydrogen atoms can stabilize the surface, passivating it electrically and chemically. The formation of Si–O–R and Si–C–R moieties facilitates further chemical transformations that allow for the anchoring of species as varied as hydrocarbons and proteins with the possibility of direct patterning. This review begins with a discussion of the fundamentals of Si–H bond activation and then specifically investigates a variety of activation schemes from ultraviolet (UV) and white light irradiation through radical initiators to sonochemistry and microwaves.