Akademik Veri Yönetim Sistemi
Materials Chemistry and Physics, cilt.359, 2026 (SCI-Expanded, Scopus)
The performance of TiO2 under visible irradiation is frequently limited by interfacial recombination of photogenerated charge carriers rather than by instability of the crystalline lattice. In the present study, nitrogen doped carbon quantum dots derived from Agapanthus africanus leaves were used to construct a composite with TiO2 to examine how nitrogen containing surface functionalities influence interfacial charge redistribution under visible excitation. Structural and surface analyses confirm preservation of the anatase framework and Ti4+ chemical state after in situ formation of the composite, while XPS and Mott–Schottky measurements indicate that the intrinsic band edges of TiO2 remain unchanged. Diffuse reflectance spectroscopy reveals extended absorption toward longer wavelengths, and photoluminescence measurements show suppressed emission intensity, indicating reduced radiative recombination probability in the composite system. The composite containing 3 wt percent carbon quantum dots exhibits enhanced visible light degradation kinetics for methylene blue and malachite green, with apparent rate constants approximately three times higher than those of pristine TiO2. Reactive species trapping experiments identify superoxide species and photogenerated holes as the dominant oxidative pathways under the applied conditions. The combined spectroscopic, electrochemical, and kinetic results support a surface mediated interfacial charge redistribution mechanism in which nitrogen containing carbon domains facilitate electron transfer to adsorbed oxygen species without inducing bulk band reconstruction of TiO2. These findings demonstrate that visible light response enhancement originates from surface electronic modulation rather than intrinsic lattice modification.