Synthesis and Characterization of Quantum Dots Nanopaticles for Photocatalytic Applications

Abstract

newlineCarbon quantum dots (CQDs) have come into the picture as potential nanomaterials for environmental application, especially in the remediation of water pollution via photocatalytic degradation of organic pollutants. Industrial waste effluents and domestic wastewater accumulate a vast range of poisonous dyes, which are a great environmental threat. Novel photocatalysts like CQDs provide a green and efficient way to degrade these pollutants, thereby preventing water pollution. In the present work, CQDs were prepared through three different methods-microwave-assisted synthesis, pyrolysis, and green synthesis-using different combinations of precursors. The structure and optical characteristics of the CQDs were well established through spectroscopic and microscopic studies, which proved that they were in the nanoscale range and exhibited prominent photoluminescence characteristics. Photocatalytic activity of the CQDs was evaluated by degradation of three dyes: Rhodamine B (RhB), Methylene Blue (MB), and Cresol Red (CR) using UV light as an irradiating source. newlineIn the CQDs prepared by the microwave method, the samples obtained from citric acid and L-cysteine (CQDs-1) showed the most prominent photocatalytic activity and resulted in 99.17% degradation of MB in 90 minutes and 99.7% degradation of RhB in 150 minutes. Their enhanced performance was ascribed to successful charge separation and higher mineralization of dye molecules, which are imperative for decontaminating water. Pyrolysis-derived CQDs exhibited different photocatalytic efficiencies depending on the composition of precursors. Citric acid- and polyethyleneimine-derived CQDs (CQDs-3) registered the maximum efficiency in RhB degradation (99.63% after 100 minutes), while other pyrolysis-derived CQDs possessed slightly inferior efficiencies. Interestingly, MB degradation efficiency was less, with the highest being 79% by CQDs-1. These findings confirm that pyrolysis-based CQDs can efficiently degrade organic pollutants in wastewater treatment. newlineGreen-synthesized CQDs demonstrated photocatalytic activity selectivity, with banana peel-derived CQDs (CQDs-2) reporting the best CR degradation efficiency (96.67% in 120 minutes). Green-synthesized CQDs had inferior performance for degradation of RhB and MB, indicating that the precursor material exerts a crucial effect on photocatalytic functionality. The observations reveal that eco-friendly green synthesis is feasible, but precursor material selection and reaction conditions need optimization to enhance the efficiency of CQDs towards water purification technology. newlineThis study highlights the critical role of CQDS size, surface functionalization, and precursor composition in determining photocatalytic efficiency. The results emphasize that smaller CQDs with well-defined surface functional groups exhibit enhanced photocatalytic performance, making them effective for wastewater treatment. The microwave-assisted and pyrolysis methods yielded CQDs with superior performance, while green-synthesized CQDs demonstrated selectivity. The capability of CQDs to decompose toxic dyes suggests their potential for large-scale application in industrial effluent treatment plants. Yet more research is needed to enhance the CQDs stability, recyclability, and visible-light efficiency to make them more practical for actual environmental applications. newlineWith the growing problem of water pollution, CQDs offer a promising, green, and cost-effective solution to traditional photocatalysts. Their photoluminescence, tunable properties, and high surface area make them prime candidates for future sustainable wastewater treatment technologies. Future research needs to emphasize the improvement of CQDs synthesis techniques, elucidation of reaction mechanisms in intricate wastewater matrices, and scaling up production for commercial use. Through the enhancement of CQDs efficiency and resolution of practical implementation issues, this work opens the door to the creation of sophisticated nanomaterials for cleaner and safer water resources globally. newline newline