Amino acid-functionalized CQDs/yttrium-doped ZnO nanocomposite for photocatalytic mineralization of antibiotics in water

Abstract

The designing of a novel photocatalyst, with efficient charge carrier separation and high photo-redox capability, is crucial for the efficient degradation of antibiotics from wastewater, and yet remains a significant scientific challenge. Herein, a series of carbon quantum dots-yttrium-doped zinc oxide, YZC, nanocomposites have been developed by incorporating amino acid functionalized-carbon quantum dots, A-CQDs, on yttrium-doped zinc oxide, YZnO, via hydrothermal process. The as-prepared YZC, specifically YZC-1.0, exhibited significant photodegradation activity against Amoxicillin with 90 % degradation in 180 min, Cephalexin with 81.17 % degradation in 300 min, and their mixture with 70.2 % degradation in 300 min by visible light illumination. The yttrium-doping in ZnO reduced the band gap and aided in the creation of oxygen vacancies in ZnO. While the incorporation of π-conjugated A-CQDs in YZnO served as a photosensitizer, thus facilitating electron excitation at higher wavelengths, thereby, extending the photo-response in the visible region. The synthesized YZnO and YZC photocatalysts have been characterized using XRD, FE-SEM, HR-TEM, FT-IR, BET, and XPS techniques. The optical and electrochemical properties have been studied via UV-DRS, photoluminescence, electrochemical impedance spectroscopy, and photocurrent density. Furthermore, the radical quenching experiment, electron spin resonance, and liquid chromatography-mass spectrometry were employed to investigate the degradation intermediates and their confirmation. Also, the nanocomposite YZC-1.0 manifested good reusability performance for six consecutive cycles and exhibited exceptional efficiency against real wastewater treatment, revealing its potential for application in wastewater treatment.