Fabrication of a hollow mesoporous silica hybrid to improve the targeting of a pesticide

Nanomaterials offer a great opportunity to develop new strategies for designing stimuli-responsive controlled release formulations (CRFs) of pesticides. In this study, a pH sensitive controlled release system, poly(glycidyl methacrylate-co-acrylic acid) (P(GMA-AA)) grafted hollow mesoporous silica (HMS@P(GMA-AA) was fabricated. HMS was fabricated using a hard template and functionalized with 3-(trimethoxysilyl)propyl methacrylate. Then, P(GMA-AA) was grafted onto HMS by seeded precipitation polymerization. Abamectin (aba) was selected as the model pesticide to test the pH-sensitivity property. Detailed investigations showed that Aba@HMS@P(GMA-AA) exhibited a high pesticide-loading efficiency (33 wt%) and superior stability. The release of Aba from Aba@HMS@P(GMA-AA) was pH-dependent. In addition, Aba@HMS@P(GMA-AA) showed a strong combination with rice leaves, mainly benefitting from its low contact angle and high adhesion work on leaves. Bioactivity studies in a greenhouse and the field indicated that Aba@HMS@P(GMA-AA) was more toxic than Aba emulsifiable concentrate (Aba-EC) in controlling rice pest Cnaphalocrocis medinalis (Guenee) larvae, and it possessed long-term efficacy in practice. Importantly, there was no obvious influence on the growth of rice seedlings treated with Aba@HMS@P(GMA-AA). The results suggest that the proposed controlled release system is a promising candidate for the management of pests.