Synthesis of sulfhydryl functionalized silicon quantum dots with high quantum yield for imaging of hypochlorite in cells and zebrafish.

Sulfhydryl functionalized silicon quantum dots (S-SiQDs) with a fluorescence quantum yield of 38.5% were synthesized using 3-mercaptopropyltrimethoxysilane (MPTMS) and m-phenylenediamine by a simple one-pot method. It is worth noting that by oxidizing the surface sulfhydryl groups and statically quenching, the fluorescence of S-SiQDs at 492 nm (excitation at 383 nm) can be selectively quenched by hypochlorite (ClO) in a linear range of 0.05 to 1.8 μM with a low detection limit of 13 nM. The reaction was completed in 10 s with no interference from other ROS, metal ions, anions and reducing species. The silicon source containing sulfhydryl groups was used to synthesize silicon quantum dots for the first time, and the surface of the S-SiQDs was provided with sulfhydryl groups and reacted rapidly and sensitively with ClO. The S-SiQDs have good photostability and biocompatibility, and can be further used for ClO imaging in MCF-7 cells and zebrafish, showing great promise in biological imaging. The proposed assay demonstrates that 3-mercaptopropyltrimethoxysilane is a good choice to obtain a functionalized fluorescent nanoprobe for redox species.