An environmentally-conscious approach to the synthesis and separation of Ultrasmall Si nanoparticles

Silicon nanoparticles (SiNPs) are an attractive material due to their efficient emission, photostability, and biocompatibility. Given the size-dependent physiochemical and optical properties of SiNPs, the ability to generate a monodisperse population stands out as a crucial next step for translation to the commercial and health sectors. Unfortunately, such demand is hindered on two fronts: (1) the detrimental environmental impact of manufacturing silicon wafers (a prerequisite to generate SiNPs), and (2) the difficulty in achieving a narrow size distribution of SiNPs. Herein, we report on an efficient preparation method via used Si wafers and the size/charge-based separation of SiNPs via capillary electrophoresis (CE). We obtain blue-shifted fluorescent SiNPs with an average diameter of 3.17 nm as assessed via transmission electron microscopy and demonstrate the use of CE to further refine and narrow the distribution of SiNPs by particle diameter and surface charge. Ultimately, we propose an economical and environmentally-friendly alternative, and envision that size-based separation of SiNPs via CE can be expanded to other fields as a standard protocol for size characterization.