Effective remediation of pollutants is challenging; although TiO2 and ZnO have unique photocatalytic properties, large band gaps/high recombination of electron¿hole pairs limit the practical use. ZnO/TiO2 increases electron mobility, improving the above limitations. The addition of biomass CQDs increases the specific surface area and surface oxygen vacancies due to their up-conversion properties, and is expected to further enhance photocatalytic activity. So, TiO2/ZnO-CQDs, which were prepared by dispersing TiO2/ZnO NPs in ethanol, to which CQDs were added, were characterized using various analytical techniques. In TEM for TiO2/ZnO/CQDs (~ 112 nm), CQDs on the TiO2/ZnO surface form a heterojunction between ZnO (d = 3.5 Å) and TiO2 (d = 2.81 Å). Photoluminescence intensities of TiO2/ZnO (361¿447 nm) correspond to interfacial defects that create deep oxygen vacancies and reduce radiative recombination. Thus, TiO2/ZnO/CQDs exhibit low-intensity emissions, confirming the h+/e¿ separation and consistent with electrochemical impedance, where a smaller Nyquist semicircle for TiO2/ZnO/CQDs results, giving lower interfacial resistance as TiO2/ZnO (2689 ¿) than for TiO2/ZnO/CQDs (2358 ¿). The greater LEVO adsorption (k = 5.0788 × 10¿5 mol/g) for TiO2/ZnO/CQDs, as compared to individual metal oxides; so, TiO2/ZnO/CQDs (0.5 g/L) oxidized LEVO efficiently (k = 1.30 × 10¿2 mM/s, 78.32% under sunlight; k = 6.00 × 10¿3 mM/s, 52.06% under visible light). The sample was recyclable over 10 cycles. The intermediates from LEVO oxidation were analyzed using 2D HPLC, agreeing with LC¿MS and DFT. TiO2/ZnO/CQDs against S. aureus (22.7%) and E. coli (21%) indicate their non-toxicity. This biomass-derived CQDs impacts the electronic properties of TiO2/ZnO, offering a sustainable environmental strategy.
