Fulvic Acid-Modified Carbon Nanohorns as a Pesticide–Fertilizer Bifunctional Nanocarrier for Controllable Delivery of a Phenylamide Derivative

While current nanopesticides often face challenges such as complex preparation, limited functionality, and potential environmental risk, this study develops a pH-responsive fulvic acid-functionalized carbon nanohorn (FA-CNH) carrier for delivering a chlorophenylamide (CPA) derivative, achieving combined pesticide and fertilizer functions. A total of 36 phenylamide-based compounds were designed, synthesized, and characterized by NMR and high-resolution mass spectrometry. A comparative study was conducted on the in vitro antifungal activity of these compounds against Rhizoctonia solani. The in vitro fungicidal activity of CNH-FA-CPA35 was better than that of CNH, CNH-FA, and CPA35, which was mainly due to the synergy between the materials. In vivo experimental results of rice indicated that CNH-FA-CPA35 could protect rice leaves and leaf sheaths from the infection of R. solani. The biosafety evaluation of the germination rate further verified that CNH-FA-CPA35 had no toxic effect on rice. CNH-FA-CPA35 exhibits sustained-release delivery capability and excellent antifungal activity, demonstrating its potential for application in sustainable agriculture.