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 groups were generated, which was attributed to the photocatalytic activity of TiO2. The •OH 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.