Silicon nanoparticles for biophotonics

Over the past several years there has been tremendous research activity in the application of inorganic nanoparticles, particularly semiconductor quantum dots, in bioimaging, bioassays, and other biological applications where they may have tremendous advantages over more traditional organic fluorophores. Much of that work has focused on quantum dots of compound semiconductor materials such as cadmium selenide (CdSe). Photoluminescent quantum dots of silicon can offer most of the features of those compound semiconductor quantum dots, but with reduced toxicity concerns, greater flexibility and stability of surface functionalization, and other potential advantages. However, use of silicon quantum dots in bioimaging and other biophotonics applications has been quite limited. This is primarily due to the lack of simple, reproducible, and widely available methods for preparing uniform, high quality samples of them. The optical properties of silicon nanoparticles, in particular the need to us ultraviolet light to excite their photoluminescence, also offer some challenges for their application in biophotonics. In this chapter, we consider the properties, preparation, surface functionalization, and biophotonics applications of silicon nanoparticles, with an eye toward their advantages and disadvantages relative to other inorganic nanomaterials and more traditional fluorophores.