Elemental Selenium Quantum Dots: A Versatile Fluorescent Nanoprobe for Simultaneous Detection and Scavenging of Hydroxyl Radicals

The creation of fluorescent nanoprobes capable of both detecting and neutralizing reactive oxygen species (ROS) has remained an elusive goal in biomedical research. In this study, we present a straightforward one-pot solvothermal approach to synthesize elemental selenium quantum dots (SeQDs), a novel class of metal-free nanomaterials, directly from bulk selenium using a bulk selenium-ethylenediamine precursor. When optimized at 180 °C for 4.5 h, the SeQDs achieve an impressive product yield of 7.1 ± 0.5% and a single-photon photoluminescence quantum yield (PLQY) of 21.4 ± 1.3%, along with strong two-photon fluorescence. Notably, these SeQDs serve as dual-responsive nanoprobes for hydroxyl radicals (^·OH). They enable selective detection with a low detection limit of 330 nM and a linear range of 5-100 μM, while simultaneously exhibiting efficient ^·OH scavenging capabilities. The mechanism underlying the fluorescence sensing and scavenging of ^·OH by SeQDs is likely attributed to the chemical reaction between SeQDs and ^·OH. Moreover, their low cytotoxicity and effective cellular uptake make them highly suitable for single- and two-photon fluorescence imaging as well as real-time monitoring of intracellular ^·OH. This work not only introduces a scalable strategy for synthesizing highly fluorescent SeQDs but also highlights their unique dual functionality in combating oxidative stress, presenting a promising platform for investigating and managing oxidative damage in living systems.