Generation of Schottky heterojunction (SnO2-Au NPs) transparent thin film for ciprofloxacin photodegradation

Abstract

In this study, transparent Schottky heterojunction thin films composed of SnO₂ and Au nanoparticles (Au NPs) were developed and applied for the photocatalytic degradation of ciprofloxacin (CIP) under UV light. The SnO₂-Au NPs films achieved a 75 % degradation of CIP and 70 % total organic carbon (TOC) mineralization within 180 min using only 0.02 g/L of catalyst, highlighting their exceptional efficiency compared to conventional powder-based systems. The incorporation of Au NPs significantly enhanced charge separation and reduced electron-hole recombination, as confirmed by structural and optical analyses. Optimal photocatalytic activity was observed at pH 7, following pseudo-first-order kinetics. Scavenger tests and fluorescence probing confirmed that hydroxyl radicals (•OH) and superoxide radicals (O₂•−) were the primary active species. QTOF-MS identified five degradation intermediates, suggesting mechanisms involving defluorination, hydroxylation, and ring cleavage. In silico toxicity assessments showed reduced toxicity for most transformation products. The catalyst exhibited high stability and reusability over four cycles without detectable leaching, indicating strong potential for sustainable water treatment applications.