Copper ions chelated mesoporous silica nanoparticles via dopamine chemistry for controlled pesticide release regulated by coordination bonding

Abstract Controlled release of pesticide is highly desirable for improving efficacy and reducing side effects. Hydrophobic, hydrogen bonding, and ionic interactions have been widely investigated to control the release of pesticides. However, metal coordination bonding is yet to be fully explored for controlled release of pesticides. In this study, copper ions (Cu2+) chelated mesoporous silica nanoparticles (MSNs) via dopamine chemistry (AZOX@MSNs-PDA-Cu) for controlled azoxystrobin (AZOX) release have been developed. The chemical properties and morphological features of the nanoparticles were characterized by SEM, TEM, FT-IR, TGA, XPS, and N2 adsorption/desorption. The coordination bonding interaction between copper ions and AZOX slows down the release of AZOX to the surrounding environment. Moreover, copper chelation could endow cargo molecules with pH-responsive release profiles because of the competitive coordination of protons to polydopamine (PDA) layers or hydroxide ions to Cu2+ to break down the coordination bonding architecture of “PDA–Cu2+–AZOX”. AZOX@MSNs-PDA-Cu exhibited better fungicidal activity against Pyricularia oryzae than AZOX technical under the same dose of active ingredient applied. Dynamic contact angle measurement demonstrated that the PDA coating could improve adhesion ability and deposition efficiency toward crop leaves. This strategy opens up a facile but powerful avenue for the design of pH-responsive systems and new opportunities for their application in pesticide delivery.