Characterisation and larvicidal effects of different zinc oxide nanoparticles against Aedes aegypti larvae

Abstract

This work reports the characterisation and larvicidal effects of two ZnO nanoparticle types towards Aedes aegypti (Ae. aegypti) larvae. ZnO-AG (as-grown ZnO produced by gas-phase synthesis) and ZnO-BM (ball-milled for one week) were the two types of ZnO nanoparticles. ZnO-AG and ZnO-BM were characterised for structural, optical, and morphology properties by XRD, UV–vis, and FESEM, respectively. The colloidal nanoparticles were centrifuged and dried for the ZnO-BM sample before the bioassay procedure was performed on the third instar Ae. aegypti larvae. Bioassay procedures were done following WHO standards for both samples. The results revealed that ZnO-BM had a smaller crystallite size (34.88 nm) and higher EDX O: Zn ratio (0.831) compared to that of ZnO-AG (crystallite size 47.4 nm and 0.675 of O: Zn EDX ratio). Moreover, bioassay results showed ZnO-BM has lower LC50 (48.6 mg/L) compared to ZnO-AG (73.47 mg/L), which suggested the stronger toxicity of the ball-milled sample toward Ae. aegypti larvae. The higher mortality rate of the ZnO-BM sample can be attributed to its larger surface area-to-volume ratio that led to enhanced ROS (reactive oxygen species) generation and increased zinc dissolution that caused internal organ damage inside the Aedes larvae.