CdS:Mn–Polysulfido Complex Nanoclusters with H₂O₂-Dependent and Site-Specific Color Changes

Hydrogen peroxide (H2O2) is a potent oxidant that influences the growth and well-being of living organisms, and development of a probe to monitor H2O2 in biological media is of broad interest to chemistry, biology, and medicine. Herein, CdS:Mn–polysulfido nanoclusters (NCs) are demonstrated to be chromogenic probes that can monitor H2O2 in a fast and site-specific way. The NC complex is formed by a reaction between manganese ions and both polysulfido chains and small CdS nanoparticles. The NCs exhibit two color changes from beige to bright yellow and then colorless in the presence of H2O2. The bright yellow color appears within 15 s after the NCs come in contact with H2O2 and fades at a rate that is positively related to the H2O2 concentration. The appearance of the bright yellow color is accompanied by the production of a strong absorption peak at 387 nm related to free Mn-bonded polysulfido chains. Our results demonstrate potential applications of inorganic chromogenic nanomaterials to the monitoring of chemical and biological reactions.