Cost-Effective Synthesis of Silicon Quantum Dots

Silicon (Si) nanomaterials with bright luminescence in the visible region are promising materials for use as the next-generation light source in displays, lighting, and biomedical imaging. A scalable and cost-effective method for the synthesis of Si quantum dots (SiQDs) is essential for research and development in the field of quantum dots. Herein, we show a facile and cost-effective method for controlling the structure and properties of SiQDs, obtained using the pyrolysis of hydrogen silsesquioxane (HSQ) polymer precursors synthesized using methanol. The amount of methanol added to trichlorosilane prior to the addition of water is a key factor that determines the structure and cross-linking density of the HSQ polymer used as the precursor. In turn, these features control the SiQD size, crystallinity, and luminescence efficiency. Dodecyl-passivated SiQDs of size 3-4 nm are obtained as a final product and show red photoluminescence (PL) at approximately 700-800 nm with the peak wavelength depending on the size of SiQDs. The PL quantum yield ranged from 10 to 25% with the highest value obtained for the smaller SiQDs with higher crystallinity. The present study provides new insight into the SiQD synthesis procedure and the understanding of the reaction mechanism. Furthermore, it was found that only methanol is the crucial reagent and the facile and cost-effective synthesis method can be controlled merely by changing the amount of methanol.