TiO₂/Biochar with Light-Switchable Wettability as a Herbicide Safener and Foliar Fertilizer Adhesive

A light-switchable herbicide nanosafener (LHNS) was fabricated using TiO2, biochar (BC), and hydrogen silicone oil (HSO). Here, BC was used as a carrier for TiO2 to form a rough micro-nanocomposite TiO2/BC, which was then modified by HSO to obtain LHNS with high hydrophobicity. After being sprinkled on crop leaves, the LHNS could endow leaves with a hydrophobic surface and decrease the adhesion of glyphosate (Gly) and the adverse effects on crops. Under ultraviolet (UV) light, many (OH)-O-center dot groups were generated, which was attributed to the photocatalytic activity of TiO2. The (OH)-O-center dot could decompose HSO on the TiO2 surface and introduce a number of -OH groups and adsorbed water on the LHNS surface, yielding a product named hydrophilic LHNS (HL-LHNS). HL-LHNS could be used as an adhesive to improve the adhesion of foliar fertilizer. Under infrared (IR) light, the amount of water adsorbed by HL-LHNS decreased because of the photothermal effect of BC, forming a product named hydrophobic LHNS (HB-LHNS). Therefore, this work provides a promising approach to reduce the adverse effects of herbicides and enhance the utilization efficiency of foliar fertilizer, which may have potential application prospects.