pH-responsive and NIR-triggered nanopesticide for precision control of sclerotinia sclerotiorum in oilseed rape

A composite consisting of upconversion nanoparticles (UCNPs) and methylene blue (MB)-loaded zeolitic imidazolate framework-8 (ZIF-8), referred to as UCNP@ZIF-8@MB, was synthesized via a simple hydrothermal and one-pot approach for the targeted control of Sclerotinia sclerotiorum ( S. sclerotiorum ) in oilseed rape ( Brassica napus L. ). Taking advantage of the pH-responsive nature of ZIF-8, the composite responds selectively to the acidic microenvironment associated with pathogen infection. Upon 980 nm excitation, UCNPs emit at 650 nm, which activates MB to generate reactive oxygen species (ROS) via photolysis, thereby exerting antifungal effects. The physicochemical properties of UCNP@ZIF-8@MB, including its optical behavior, MB release profile, and adhesion capacity, were systematically characterized. Under mildly acidic conditions (pH 5.5–4.0), MB release exceeded 80 %, indicating efficient responsiveness to the infection milieu. In vitro antifungal assays demonstrated a minimum inhibitory concentration (MIC) of approximately 10 μg/mL under 980 nm laser irradiation. Pot experiments further confirmed significant antifungal activity under light exposure. Additionally, UCNP@ZIF-8@MB exhibited targeted release and favorable biocompatibility with plant tissues and the surrounding environment. These results underscore the potential of UCNP@ZIF-8@MB as an environmentally friendly nanopesticide for the precise management of sclerotinia disease, offering a promising strategy for sustainable agriculture.