Surface Modification of p‐type ZnO Nanorods by Nitrogen Doped SiO2 Dots as an Efficient Solar Photocatalyst for Degradation of Ciprofloxacin in Water

Abstract

AbstractA simple two step hydrothermal method is developed for synthesizing p‐type zinc oxide (ZnO) nanorods surface modified with nitrogen doped silicon dioxide dots (ZnO/N‐SiO2). The structure, morphology, and chemical compositions are confirmed by X‐ray diffraction, Raman spectroscopy, Fourier transformed infrared spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy, and by Mott‐Schottky studies. The N‐SiO2 dots on the surface of p‐type ZnO nanorods are formed during hydrothermal treatment at 90 °C (i.e., at 363 K), named as [ZnO/N‐SiO2]363K. While N‐SiO2 dots are embedded in the ZnO nanorods of the batch synthesized at 453 K. The band gap of the batches of ZnO/N‐SiO2 are wider (3.24–3.30 eV) than the pristine ZnO (3.16 eV). The modification of ZnO nanorods by the N‐SiO2 dots is corroborated by changes in the flat band potential, revealed from Mott‐Schottky measurements. The EPR and photoluminescence studies confirm p‐type ZnO attributable to zinc vacancies (VZn). The batch [ZnO/N‐SiO2]363 exhibits maximum photocatalytic degradation of ciprofloxacin in water. The specific rate constant is k′ = 0.97 min−1 g−1, which is nearly three times higher than that exhibited by the irregularly spherical pristine ZnO nanoparticles (k′ = 0.36 min−1 g−1). The enhanced photocatalytic degradation is attributed to holes mediated hydroxyl radical generation. The degradation mechanism is proposed by carrier mobility studies, radical scavenging studies and by identifying the degradation products.