TITLE:
Study of Photocatalytic Activity of a Nanostructured Composite of ZnS and Carbon Dots
AUTHORS:
Irié Bi Irié Williams, Essy Kouadio Fodjo, Pomi Bi Boussou Narcisse, Aka Alla Martin, Koffi Koffi Kra Sylvestre, Trokourey Albert, Zhen Gu
KEYWORDS:
Fluorescent Carbon Dots (CDs), Photocatalytic Degradation of Methylene Blue, Sunlight Reflectance Property, Synthesis of ZnS Nanoparticles
JOURNAL NAME:
Advances in Nanoparticles,
Vol.11 No.4,
November
22,
2022
ABSTRACT: Environmental pollution jeopardizes our existence. For this purpose, research is moving more and more towards the search for economic means and green chemistry to curb this phenomenon. In this context, the photocatalytic activity of zinc sulfide nanoparticles (ZnS NPs) and nanostructured composite ZnS/carbon dots (ZnS/CDs) was evaluated after their synthesis. The results of X-ray diffraction (XRD) analysis indicate that the crystal structure of ZnS/CDs is identical to that of the cubic phase structure of ZnS, revealing that the cubic phase structure of ZnS was not altered in the presence of CDs. Indeed, there is no additional peak in the crystal structure of ZnS/CDs, revealing that the crystalline structure of ZnS is not responsible for the difference in photocatalytic activity between ZnS/CDs and ZnS NPs. Moreover, analysis performed by transmission electron microscopy (TEM) shows aggregation of the synthesized ZnS and ZnS/CDs nanoparticles with an average size estimated around 10 nm and 12 nm, respectively. In addition, the reflectance study in the visible range shows a reduction in the sunlight reflection intensity using ZnS/CDs compared to the capability of ZnS NPs. Photocatalytic degradation tests reveal that ZnS/CDs have the best methylene blue (MB) degradation rate. Indeed, under the optimal conditions, the photocatalytic activity can reach 100% efficiency within 100 min and 240 min of sunlight exposure for the degradation of 7.5 mg/L MB using ZnS/CDs and ZnS, respectively. This improvement in photocatalytic activity of ZnS/CDs may be due to the presence of CDs which can permit to undergo a reduction of reflection properties of ZnS NPs in the visible range. These results show that CDs can play a key role in enhancing the photocatalytic activity of ZnS, and suggest that ZnS/CDs could be used as eco-friendly composite materials for the degradation of organic pollutants of similar structures in the aquatic environment under solar irradiation.