Light-tuning the host–guest interfacial recognition of Alginate-based amphiphiles for oil-in-water droplet deposition

Encouraged by the strategy of increasing efficiency and reducing pesticide overuse, the development of polymer/surfactant as additives to enhance pesticide droplet deposition on hydrophobic leave is a promising project. Herein, Alginate-based supra-amphiphiles (SAs), host–guest self-assembled by host amphiphilic cyclodextrin-functionalized alginate derivative (Alg-CD) and guest azobenzene-based surfactant (Azo-DEMA), performed comprehensive characteristics, which integrated the viscosity effect and the ability to reduce surface tension. SAs enabled oil-in-water pesticide droplets to inhibit splashing and light-regulate wetting, thereby enhancing droplets deposition. By analyzing the impact dynamics of loaded-pesticide o/w droplets on hydrophobic surface, the addition of SAs rapidly afforded the pinning ability of droplets with the target surface, and in turn, resulted in inhibiting splashing. Afterward being exposed to UV light, the resulting SAs o/w droplets undergone disassembly so as to release small-molecular surfactant and reduce the surface tension of droplets for improving droplets' wettability. Importantly, quartz crystal microbalance with dissipation monitoring (QCM-D) was skillfully used for revealing the interaction mechanism between droplets and the waxy layer of hydrophobic surface, finding that SAs could form compact conformation on the waxy surface, while disassembled SAs undergoing UV irradiation exhibited the large adsorption amount and stronger interaction with waxy layer. Consequently, the herbicidal activity experiments exhibit sensitive pesticide control effects assessed under UV even natural sunlight. Light-regulating host–guest interfacial interaction of polysaccharide-based supra-amphiphiles may provide a novel, eco-friendly and feasible manner for comprehensive pesticide applications.