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

Abstract A 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 (V_Zn). 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.