Photocatalytic performance of CuI/Cu2+ -TiO2 for controlling Magnaporthe oryzae infection in rice plants.

Abstract

This study presents the synthesis, characterisation, and photocatalytic antifungal performance of a Cu+/Cu2+-TiO2 nanocomposite designed to control rice blast disease caused by Magnaporthe oryzae. The heterostructure was fabricated through a chemical precipitation process in which TiO2 was first doped with Cu2+ ions, followed by partial reduction to Cu+ to form CuI. X-ray Photoelectron Spectroscopy (XPS) confirmed the coexistence of both Cu+ and Cu2+ oxidation states. A notable feature of this material is its Cu+/Cu2+ redox cycling, which enhances charge separation during photocatalysis and supports the sustained production of reactive oxygen species (ROS), such as ●O2- and ●OH. These reactive species are intensified under visible-light LED irradiation, thereby imposing strong oxidative stress on the fungal pathogen. The optical bandgap energy (Eg) was calculated from UV-Vis diffuse reflectance spectra (DRS) using a Tauc plot method implemented in a Python-based analysis. Eg decreased systematically from 3.02 eV for pristine TiO2 to 2.67 eV for the optimized 3CuT3 composite. Correspondingly, the UV-Vis absorption edge exhibited a red shift from approximately 410-465 nm, indicating enhanced visible-light absorption. The 3CuT3 sample, containing the highest Cu loading (9.52 wt%), exhibited the strongest antifungal activity, achieving 91.55% inhibition of M. oryzae at 500 ppm after 10 days. In comparison, the 1CuT1 and 2CuT2 samples showed lower inhibition efficiencies of 78.22% and 83.55%, corresponding to their lower Cu contents of 2.73 wt% and 4.04 wt%, respectively. These findings suggest that the Cu species (Cu+/Cu2+) incorporated into the nanocomposite play a critical role in enhancing antifungal performance. This work provides a basis for further evaluation of the practical applicability and ecological safety of the Cu+/Cu2+-TiO2 nanocomposite for sustainable crop protection. ppm after 10 days. In comparison, the 1CuT1 and 2CuT2 samples showed lower inhibition efficiencies of 78.22% and 83.55%, corresponding to their lower Cu contents of 2.73 wt% and 4.04 wt%, respectively. These findings suggest that the Cu species (Cu+/Cu2+) incorporated into the nanocomposite play a critical role in enhancing antifungal performance. This work provides a basis for further evaluation of the practical applicability and ecological safety of the Cu+/Cu2+-TiO2 nanocomposite for sustainable crop protection.