A novel double Ag@AgCl/Cu@Cu2O plasmonic nanostructure: Experimental design and LC-Mass detection of tetracycline degradation intermediates

Abstract

Here a novel sunlight-driven double-plasmonic Ag@AgCl/Cu@Cu2O nanophotocatalyst was constructed via photochemical-conversion and photoreduction methods for the first time. The as-prepared Ag@AgCl/Cu@Cu2O was characterized by several characterizations techniques. The Scherrer equation showed the crystallite sizes of 37, 25, and 40 nm for the as-prepared Ag@AgCl, Cu@Cu2O and Ag@AgCl/Cu@Cu2O catalysts, while their band gap energies were 3.36, 2.51, and 3.04 eV (DRS results), respectively. TC (tetracycline) served as a probe to study its photocatalytic activity under sunlight. It was found that the as-prepared nanophotocatalyst with suitable Ag@AgCl and Cu@Cu2O content not only demonstrated superior photocatalytic activity to both Ag@AgCl and Cu@Cu2O plasmonic nanoparticles, but also had remarkable photostability due to the presence of two simultaneous surface plasmon resonance (SPR) in metallic Ag and Cu NPs and the hetero-junction structure formed at the interface between Ag@AgCl and Cu@Cu2O. The main active species were detected through a trapping experiment which confirmed that •O2− and •OH were the main active species in the photocatalytic system. Central composite design (CCD) was used for the modeling and optimization of the photodegradation process. The possible photocatalytic degradation pathway of TC was proposed based on the identified intermediates. The photodegradation rate constant of TC was about 0.043 min−1 (t1/2 = 0.910 min) (in the range of 5–60 min). The optimum RSM run had the conditions the TC concentration of 2.0 (mg/L), Ag@AgCl/Cu@Cu2O dosage of 0.53 (g/L), irradiation time 18 (min), and pH value of 6.5.