Non-stoichiometric CuxIn1−xS quantum dots for robust photodegradation of gemifloxacin: influencing parameters, intermediates, and insights into the mechanism

Abstract

Non-stoichiometric quantum dots (QDs) have gathered wide attention in advanced oxidation processes for environmental remediation due to their ability to generate highly reactive oxygen active species. Here, a series of promising non-stoichiometric Cu_xIn_1−xS QDs were fabricated via the reflux method and examined toward the degradation of gemifloxacin (GMF) under visible light. Cu_0.75In_0.25S QD showed optimum activity toward GMF degradation (95% in 2 h, rate const = 258 × 10⁻⁴ min⁻¹) with a TOC (total organic carbon) efficiency of 70% due to the non-stoichiometric arrangement of Cu and In metals, which not only promoted the spatial excitons separation efficiency but also bestowed the reducing power of photo-induced electrons as supported by the required characterization. Further, the compositional ratio and phase pure chalcopyrite Cu_xIn_1−xS QDs indicate the good formation of the composition tunable materials. Additionally, an in-depth study was performed to study the effect of anions and pH on the degradation efficiency. Moreover, the scavenging experiments illustrate that ˙O₂⁻ and ˙OH (indirect route) radicals play a dominant role in GMF degradation, whereas the cycling test showed long-term durability of Cu_0.75In_0.25S QD. Eventually, the degradation route was traced by recognizing the intermediate products via. LC-MS study. This research provides an innovative platform for efficient photocatalytic pollutant degradation by non-stoichiometric Cu_xIn_1−xS QDs in a sustainable environment.