Light-enhanced π-π stacking of alginate-based supra-amphiphiles for structured droplet's stability and foliar deposition

The limited foliar deposition of agrochemicals on superhydrophobic foliar surfaces, caused by interfacial incompatibility and environmental loss, critically constrains sustainable crop protection. To address the challenge, the work engineered hierarchical structured Pickering emulsions (PEs) droplets with UV-tuning liquid-liquid micro/nano-interfaces based on supramolecular chemistry. Azobenzene-modified alginate (HMSA-Azo) and guanine derivatives (GuA) served as foundational building blocks, assembling via π-π stacking interactions at the oil-water interfaces. Flexible interfacial particle films were constructed by these components through self-assembly, exhibiting exceptional mechanical stability and adaptive coupling deformation. Multiscale characterization combining molecular dynamics (MD) simulations, isothermal titration calorimetry (ITC), and dissipative quartz crystal microbalance (QCM-D) revealed that 365-nm irradiation reinforced π-π stacking between HMSA-Azo and GuA, thereby enhancing the mechanical stability of interfacial films. Meanwhile, 254-nm light triggered GuA-mediated photothermal conversion at the liquid-solid interfaces, inducing adaptive coupling deformation of flexible interfacial particle films. Environmental scanning electron microscopy (ESEM) visualized how this nonequilibrium rearrangement of self-assembled nanoparticles penetrated air barrier layers. The dual-light-tuning PEs achieved: 97 % energy dissipation efficiency through interfacial film strengthening, 46 % reduction in 3D network porosity during emulsion drying, 89.92 % rainfall-resistant foliar retention. Controlled potted trials validated biosafety of the emulsion delivery system and completed barnyard grass eradication (100 % mortality rate) with outstanding bioactivity. Furthermore, sequential UVA/UVC irradiation amplified the carrier's regulatory effect, improving the utilization efficiency of active ingredients. The key to this work hinged on light-mediated synergy between liquid-liquid and liquid-solid interfaces, enabling the deposition of targeted leaves with environmental adaptability.