Synchronic coupling of Cu2O(p)/CuO(n) semiconductors leading to Norfloxacin degradation under visible light: Kinetics, mechanism and film surface properties

- Cu2O(p)/CuO(n) cohabit sputtered thin film on polystyrene.
- Norfloxacin degradation was achieved under visible light on the sputtered film.
- Redox processes were monitored by (XPS) during Norfloxacin degradation.
- Synchronic interfacial charge transfer between Cu2O(p) and CuO(n) was observed.

The study presents the first evidence for Norfoxacin photodegradation by uniform, adhesive and robust CuOx-polystyrene (CuOx-PES) films under visible light. Repetitive Norfloxacin degradation was attained on CuOx-PES films activated by visible light. The smooth CuOx-PES surface properties were investigated by diffuse reflectance spectroscopy (DRS). The band-gap of the Cu2O and CuO making up CuOx films were estimated by Tauc's method. By atomic force microscopy (AFM) the CuOx micro-agglomerated size was determined as well as the relatively small roughness of 22.4 ± 10% nm and the distance between the Norfloxacin anchoring points on the CuO peaks. Evidence is presented by transmission electron microscopy (TEM) for the uniform distribution of Cu-clusters on the PES. The degradation of Norfloxacin was monitored in the range 2-20 mg/L, a Norfloxacin concentration far above the concentrations found in treated wastewaters. Proof of redox processes occurring in the CuOx during Norfloxacin degradation were monitored by (XPS). Deconvolution of the Cu2p3/2 peaks revealed Cu2O and CuO in different percentages before and after Norfloxacin degradation. The CuOx-PES samples were made up by Cu2O(p) and CuO(n) with an approximate ratio of Cu2O: CuO = 3: 1 before Norfloxacin degradation. Highly oxidative radical species and photogenerated holes Cu2Ovb (h+) were identified during Norfloxacin degradation. A mechanism is suggested for the Norfloxacin degradation involving highly oxidative radicals detected by scavenging experiment and the limits for the validity of this method are discussed.

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