Sunlight-Driven Photocatalytic Degradation of Ciprofloxacin by Carbon Dots Embedded in ZnO Nanostructures

Abstract

Surface modification of ZnO nanoparticles (NPs) is considered as a key for enhanced sustained generation of reactive oxygen species (ROS) in the reaction medium for improving the photocatalytic degradation phenomenon. Here, we present a simple chemical method of synthesizing carbon dots (CDs) embedded on the surface of ZnO NPs denoted as ZnO/CD nanocomposites (NCs) as a photocatalyst for efficient sunlight-driven degradation of ciprofloxacin (CIP). The X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies confirmed the formation of needle-shaped clusters of ZnO/CD NCs. The band gaps of ZnO/CD NCs and pristine ZnO are determined from Tauc's plot. Under optimized conditions, the batch of CIP at pH 6.3 ± 0.1 treated with 0.6 g L −1 of ZnO/CD NCs revealed 98% photocatalytic degradation of CIP in 110 min by harnessing longer UV and the visible components of sunlight. The rate of photocatalytic degradation was 0.30 min −1 , which was 3 times higher than that of the pristine ZnO NPs. The enhanced rate of degradation by ZnO/CD NCs is attributed to the improved mobility of charge carriers and the generation of enhanced ROS. This is confirmed by the scavenging studies of hydroxyl radicals and superoxide radicals. The higher ROS generation is attributed to the inhibition of charge carrier recombination facilitated by the CDs embedded on the surface of ZnO NPs. The applicability of ZnO/CD NCs as a photocatalyst is demonstrated from five cycles of repeatability studies. After five cycles of operation, the structure and surface morphology of the used ZnO/CD NCs were stable, confirmed by XRD, TEM, and Fourier transform infrared studies. It is concluded that ZnO/CD NCs are efficient sunlight-driven photocatalysts for improved photocatalytic degradation of CIP, a model emerging contaminant.

Photocatalytic activity study of ZnO modified with nitrogen–sulfur co-doped carbon quantum dots under visible light

“…In the figure, the XRD pattern of pure ZnO clearly shows (100), (002), (101), (102), (110), (103), (200), (112), (201), (004) and (202) crystallographic planes of typical hexagonal ZnO lead-zincite structures (JCPDS file number 36-1451). 48,49 The pattern indicated that the as-synthesized ZnO has good crystalline properties. Besides, there are no extra diffraction peaks in the pattern so that the synthesized ZnO is relatively pure and free of extra impurities.…”

Amine-Functionalized Crystalline Carbon Nanodots Decorated on Bi2WO6 Nanoplates as Solar Photocatalysts for Efficient Degradation of Tetracycline and Ciprofloxacin

“…The flip side of smaller band gap materials is associated with increased probability of photoinduced charge carrier recombination. In addition, the other challenges in developing photocatalysts arise from manipulating band positions for improving redox conditions for generation of reactive oxygen species and photon absorptivity. , Recently, a lot of attention has been given toward development of smaller band gap metal oxides as photocatalysts, e.g., Co 3 O 4 , MoSe 2 , Bi 2 MoO 6 , Bi 2 WO 6 , WO 3 , BiOX (X= Cl, I, Br), , Ag 2 O, and g-C 3 N 4 , to utilize abundant sunlight for degradation of hazardous substances. Mostly, these studies are focused on photocatalytic dye degradation.…”

High-performance supercapacitors based on amorphous carbon derived from natural Ramulus mori

“…27–29 Large quantities of mulberry-based by-products of extraction residues are generated during the process, which could be envisaged for value-added secondary-utilization as green energy storage materials. 30,31 The total production of Ramulus mori in 2018 in China is in the scope of 2.844–3.555 million tons. 32 A large share of Ramulus mori is consumed by agro-industries where the disposal of waste Ramulus mori is a great issue.…”