Green Carbon Dots/CaCO3/Abamectin Colloidal Pesticide Formulation for Safer and More Effective Pest Management

An ideal green leaf-deposited pesticide formulation should offer advantages such as good water dispersibility, strong foliar affinity, sustained or controlled release of active ingredients, photostability and rain-fastness, minimal nontarget toxicity, use of nontoxic organic solvents, and degradable adjuvants. In line with this objective, we present green preparation of a colloidal pesticide formulation using optimized lysine-derived carbon dots (LysCDs)-modified CaCO3 (LysCDs/CaCO3) particles as the carrier and abamectin (Abm) as the active ingredient. The loading capacity of abamectin in this colloidal pesticide (LysCDs/CaCO3/Abm) is 1.7 to 2.1 times higher than that of its counterpart (CaCO3/Abm) prepared without LysCDs, which is attributed to the increased specific surface area and pore volume of LysCDs/CaCO3 particles. Due to the acid-induced degradation of CaCO3, the release of abamectin for LysCDs/CaCO3/Abm is accelerated under weakly acidic conditions, which is accompanied by the release of Ca2+ ions and the fluorescence changes of LysCDs. The incorporation of LysCDs enhances the photostability and foliar adhesiveness of this colloidal pesticide, resulting in the highest degree of foliar retention when exposed to ultraviolet (UV) light or rainfall, compared to free-form abamectin and CaCO3/Abm. This results in the best performance of pest control on Plutella xylostella for LysCDs/CaCO3/Abm in both indoor and outdoor tests. Nontarget biocompatibility evaluations show that LysCDs/CaCO3/Abm exhibits lower acute toxicity to zebrafish and earthworms than free-form abamectin. In addition, this colloidal pesticide is favored by the minimal residue of the adjuvant material after abamectin release, which is converted into harmless Ca2+ ions, CO2, and LysCDs. Therefore, this work designs a safer and more effective colloidal pesticide formulation to deliver abamectin with minimal adjuvant residue, realizing its trajectory as basically "circular and green".