A novel photodegradable insecticide: Preparation, characterization and properties evaluation of nano-imidacloprid

Imidacloprid (IMI) microcrystals were directly encapsulated with nature polysaccharides chitosan (CHI) and sodium alginate (ALG) through layer-by-layer (LbL) self-assembly. The coated colloids were characterized using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The in vitro controlled release pattern of IMI through the PE diffusion barrier was studied using a diffusion cell assembly at physiological pH of 7.4. Photocatalysts were characterized by Brunauer-Emmett-Teller (BET) surface area and SEM. The adsorption and photocatalytic activities of photocatalysts were evaluated by isothermal adsorption and IMI degradation under UV light and natural light illumination. The toxicity of the photodegradable insecticide was evaluated against the adult stage of Martianus dermestoides. The results showed that thermodynamically stable IMI microcrystals were obtained by association and had a mean length of 7 pm and a zeta-potential of -37.5. The drug loading and encapsulation efficiency were 56.15 +/- 0.96% and 81.57 +/- 0.96%, respectively. The polysaccharide capsules prolonged the release time of the encapsulated IMI crystals. Among the photocatalysts, SDS/Ag/TiO2 had the highest photocatalytic activity. Toxicity of the novel 50% nano-SDS/Ag/TiO2-IMI was higher in the adult stage compared to the 95% IMI as indicated by the lower LC50 value. (C) 2008 Elsevier Inc. All rights reserved.