DOI: https://doi.org/10.55373/mjchem.v24i4.46

Keywords: ZnO QDs, chitosan, microwave, photocatalysis, oxytetracycline

Abstract

This study reports the synthesis of chitosan-modified ZnO quantum dots (Chitosan-ZnO QDs) via the microwave method for the photodegradation of oxytetracycline (OTC) under visible light irradiation. The synthesised photocatalyst was characterised using Fourier transmission infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy and nitrogen adsorption-desorption (NAD) analysis. The XRD analysis indicates that Chitosan-ZnO QDs have a wurtzite hexagonal crystalline phase with an average crystallite size of 8.2 nm. The SEM analysis shows an evenly distributed micro-spherical structure. The NAD analysis indicates that the Chitosan-ZnO QDs is a mesoporous material with a Brunauer-Emmet-Teller (BET) surface area of 31.88 m2/g and an average pore size distribution of 11.7 nm. The band gap energy was determined to be 3.29 eV. The PL analysis detected the presence of various defects, enhancing its photocatalytic ability. The removal of OTC was 95.1% within 40 minutes which is higher compared to other ZnO‐based photocatalysts reported in the literature. Scavenging tests indicate that photogenerated holes (h+) and superoxide radicals (〖O_2〗^(⦁-)) were the primary reactive oxygen species responsible for photodegrading the OTC. The catalyst was stable to be recycled five times.