One-Step Hydrothermal Synthesis of Silicon Quantum Dots for Dopamine Detection and Their Antibacterial Activity against Escherichia coli and Staphylococcus aureus

Silicon quantum dots (SiQDs@SPD) were synthesized via a hydrothermal method using N-[3-(trimethoxysilyl)-propyl]-ethylenediamine as the silicon source and spermidine as the reducing agent. The production method was simple and environmentally friendly, producing spherical nanoparticles with a mean size of 2.8 nm. High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and fluorescence spectroscopy were used to further analyze SiQDs@SPD. In addition to displaying specific responses to the well-known neurotransmitter dopamine, the as-prepared SiQDs@SPD demonstrated strong antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Dopamine was quantified based on the quenching effect on the SiQDs@SPD emission at 400 nm. Furthermore, by examining the morphologies of E. coli and S. aureus and the generation of reactive oxygen species (ROS), we found that these SiQDs@SPD shrank the bacteria and probably directly destroyed the bacterial structural integrity through the creation of singlet oxygen. It is possible that SiQDs@SPD can be used as a practical dopamine detection tool as well as a treatment for resistant bacterial infections.