Functionalization of boron nitride nanosheets via thiol terminated polyethyleneimine to enhance aqueous dispersibility and efficiency as carriers for essential oils and pesticides

Abstract

The development of an efficient and environmental-friendly approach for the functionalization of boron nitride nanosheets (BNNSs) with response to pathogen microenvironment (i.e., reductive environment) is a critical issue pertaining to nanocarriers in the agricultural field. Herein, a strategy for BNNS functionalization was designed via thiol terminated polyethyleneimine (PEI-SH) linked with biocompatible poly(ethylene glycol) diacrylate (PEG), while simultaneously introducing disulfide bonds through thiol oxidation. The incorporation of hydrophilic polymer chains promoted aqueous dispersibility of BNNS at high concentrations of 30 mg mL−1. The attached hydrophilic chains could detach from BNNS in reducing environment ascribed to disulfide bond cleavage. Such features promote BNNS-PEI-PEG as an efficient and safe carrier with very low cytotoxicity for controlled release by redox stimuli. The presence of abundant positive charges on BNNS-PEI-PEG surface was found to favor the loading capacity of pesticides and essential oils with value of 338 and 389 mg g−1, respectively, while enhancing lipid foliar wettability with a reduced contact angle of 35.7 ± 1.9°. Furthermore, the antibacterial activity of essential oils was determined based on inhibition of volatilization by BNNS-PEI-PEG, with larger initial inhibition zone diameter against Escherichia coli and only reducing 34.4% after placing for 12 days. Our system provides an aqueous dispersible and controllable platform response to redox stimuli to load and release pesticides and essential oils in the field of agriculture.