ABSTRACT
Fluorescent silicon clusters and nanoparticles are also attractive in biomedical applications because nanoscale silicon and silicon dioxide are considered to be nontoxic, or at least considerably less harmful than fluorescent nanoparticles of other materials. This chapter discusses the foundations of silicon cluster experiments and cluster production. It introduces the underlying principles behind the fluorescence of silicon clusters and nanoparticles, such as quantum confinement and surface passivation. The chapter also discusses nonradiative decay at nanocrystal surfaces. The structures of silicon clusters grown in the gas phase differ from the structures of silicon nanocrystals that have been produced, for example, by etching of bulk crystalline silicon. The electronic level structure associated with dense packing, suggesting very small band gap energies for small- and medium-sized silicon clusters and even the absence of band gaps, is unfavorable toward fluorescence.
