Enhanced photocatalytic activity of CNQDs/CuNi/TiO2-x composites by utilizing surface plasmon resonance and quantum dot upconversion effect

In this paper, the new CNQDs/CuNi/TiO 2-x composites were prepared successfully for the efficient photocatalytic degradation of tetracycline hydrochloride (TCH) under visible light. The CNQDs/CuNi/TiO 2-x composite, which combined carbon nitride quantum dots (CNQDs) and bimetallic CuNi nanoparticles with defective TiO 2-x , showed excellent photocatalytic properties. The upconversion property of CNQDs transformed lower-energy light into higher-energy photons, broadening the light absorption into the visible spectrum. Moreover, the CuNi nanoparticles enhanced charge carrier dynamics through surface plasmon resonance (SPR) effects, improving the photogenerated electron-hole separation efficiency. Under optimal conditions (pH = 9), the CNQDs/CuNi/TiO 2-x composite with 2 % CNQDs achieved the highest degradation efficiency. When the initial TCH concentration was 10 mg/L and the catalyst concentration was 200 mg/L, the degradation efficiency of TCH exceeded 95 % within 60 min. The composite exhibited superior photocatalytic performance and offered the optimal balance of light absorption and charge separation. This research advances the development of sustainable and highly effective photocatalytic materials, providing a promising approach for wastewater treatment and environmental purification.