Synthesis of Carbon Quantum Dots Combined with Cu₂O Nanocubes and Their Application in Metals Ion Detection

In this study, carbon quantum dots/Cu₂O nanocubes (CQDs/Cu₂O NCBs) nanomaterial has been successfully synthesized using a simple and easy-to-implement method with a quick reaction time (90 min) at 80°C. In particular, carbon quantum dots (CQDs) were obtained by green and environmentally friendly synthesis methods, using abundant and naturally available raw materials from rice flour and applying hydrothermal approach. Besides, cuprous oxide nanocubes (Cu₂O NCBs) were also synthesized through non-toxic compounds. The morphology and composition of CQDs/Cu₂O NCBs and Cu₂O NCBs were analyzed through UV-vis, FTIR, XRD, FE-SEM, TEM, and EDX spectroscopy. The results showed that Cu₂O NCBs have a cubic shape with an average particle size of ~ 29-31 nm, and CQDs have spherical shape with a size of ~ 4-8 nm. In addition, CQDs/Cu₂O NCBs nanomaterial was also employed as a "turn-on" fluorescence sensor" for application in metal ions detection. The obtained results showed that the CQDs/Cu₂O NCBs are potential and promising in detecting Pb²⁺ ions in the wide range from 1.8 M to 10^- 9 M and extremely low limit of detection of 27.8 nM at the excitation wavelength of 340 nm. CQDs/Cu₂O NCBs-based sensors are highly sensitive and selective for Pb²⁺ detection. Therefore, CQDs/Cu₂O are promising as photocatalytic materials for various applications, including sensors, bio-probes biomedical, optoelectronics, etc.