Versatile silicon nanoparticles with potential uses as photoluminiscent sensors and photosensitizers

Silicon nanoparticles (including silicon clusters and 1–4 nm size silicon nanocrystals, SiCs) combine size – dependent photoluminescence, the capacity for singlet oxygen and superoxide radical anion generation, and the richness of silicon surface derivatization. Surface modifications as coating/linking with folate, antibodies, adjuvants, and a plethora of other substances may lead to an increased aqueous solubility, stability, biocompatibility, targeting potential, and circulation time in biological systems. Size, synthetic procedures and surface derivatization/oxidation may strongly affect the particles efficiency for reactive oxygen species photosensitization and the interaction with small molecules and biological entities. Thus, through intelligent design it is possible to develop multifunctional nanoparticles with potential applications in imaging, diagnosis, and therapy. Herein, we present and discuss the properties that make SiCs potential photosensitizers for biological uses and describe the most widely used synthesis and surface functionalization procedures in order to help understanding the basics of photoluminescent SiCs and as a guide for researchers aiming to find new applications based on these particles.