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.