One-step microwave synthesis of high-yield silica nanoparticles and the quenching mechanism of Fe and Hg ions

Fluorescent silica nanoparticles (SiNPs) have application prospects in cell imaging, optoelectronic devices, and ion detection due to their excellent optical properties, low cytotoxicity, and diverse array of surface modification methods. However, their low product yield using current preparation processes limits their further development. In this study, a high-yield one-step microwave hydrothermal synthesis method of fluorescent silica nanoparticles (SiNPs) was developed using 3-thiocyanopropyl triethoxysilane (3-TCPTES) as the silicon source and sodium citrate as the reductant. The product yield was 91.1 %, and the quantum yield (QY) was 49.1 %. In addition, the mechanism of SiNPs fluorescence quenching by different ions was analyzed, and the quenching contribution ratio of different mechanisms was estimated. The results showed that this method greatly improved the yield of SiNPs while maintaining their excellent luminescent properties and low cytotoxicity, which provides a new method for the large-scale production of high-quality SiNPs. The unique functional group structure on the surface of SiNPs realized fluorescence quenching by changing the proportion of Fe3+ and Hg2+ ions via static quenching, fluorescence resonance energy transfer, and aggregation-caused quenching, giving them potential applications as fluorescent probes.