Attapulgite-based herbicide particles with smart wetting surface for environmental-safe glyphosate delivery induced by consecutive base-acid stimuli

To minimize the pesticide loss and enhance the efficiency of active ingredient utilization, the pH-responsive controlled-release pesticide with easy operation has been widely applied despite for its potential on bothering the non-target organisms while using acid or alkaline alone. To overcome that obstacle, we developed an environmentally safe herbicide particle with a smart wetting surface that can be regulated through consecutive base-acid stimuli to maintain stable pH levels. Herein, attapulgite (ATP) is mixed with glyphosate (Gly) initially and the resultants are coated by suspensions of phenylamine-modified ATP (ph-ATP) and amino silicon oil (ASO), ultimately the outmost polyvinyl pyrrolidone (PVP) are constructed to acquire the smart herbicide (AG@ph-AA@PVP). The base may destroy the outmost PVP membrane, and the later acid treatment turns ph-AA layer gradually from hydrophobic to hydrophilic due to protonation of aniline groups, both of which allow water to invade further and promote Gly release. Therefore, the AG@ph-AA@PVP appears with excellent base-acid sensitivity and controlled-release performance, being demonstrating by the burst Gly release in water and significant weeds control efficiency in pot experiments. The interaction of the materials and the surface wettability were analyzed for explaining the controlled-release mechanism. Besides, AG@ph-AA@PVP possesses high environmental stability and good biosafety. This work develops a simple and feasible technology for environmental-safe and on-demand Gly delivery, assisting for advancement of sustainable and green agriculture.