Photocatalytic degradation efficiency of Cu/Cu2O core–shell structured nanoparticles for endosulfan mineralization

Solar light-driven photocatalytic degradation of endosulfan pesticide (ESP) by copper nanoparticles (Cu NPs) based on Cu:Cu2O core–shell model is reported in this work. Localized surface plasmon resonance (LSPR) transition of Cu NPs generates hot electrons which are transferred to Cu2O shell’s conduction band, leaving positive charges on Cu NPs and alignment of electronic states. The positively charged Cu core accepts electrons from electron donors to reduce electron–hole recombination rate. The photo-generated electrons/holes from Cu2O shell along with Cu core LSPR transferred electrons produce –OH(ullet), O2−(ullet), and –OH− reactive oxygen species for photocatalytic degradation of surface adsorbed ES molecules via oxidation, reduction, and hydrolysis reactions. The structure, morphology, and size of Cu NPs are revealed from XRD, TEM, and SEM studies. The photocatalytic degradation of ES by Cu/Cu2O NP dispersion is revealed from FTIR, UV–Vis, and electron spin resonance (ESR) investigations. IR transmittance spectra in 4000–500 cm−1 region showed the absence of chloro carbon (–C–Cl), sulfite (–SO3) functional groups, and their bonding to ES skeleton stretching/bending modes in ES-treated solutions. UV–Vis spectra have the strong broad absorption peak of Cu NP core and an additional shoulder of Cu2O shell in UV and visible regions respectively, in treated samples. ESR spectra exhibit the broad ferromagnetic resonance signal pertaining to Cu2O shell in powdered Cu NPs and ESP-treated solutions, while Cu:Cu2O dispersion showed the very strong narrow signal superimposed over broad resonance signal owing to the free radicals of solvent used for preparing dispersion.