Microencapsulation of citronella oil for solar-activated controlled release as an insect repellent

This study investigates the functionalization of titanium dioxide nanoparticles on the surface of polymeric microcapsules as a mean to control the release of encapsulated citronella through solar radiation.This allows for the release of a mosquito repellent without human intervention, as the sunlight works asa release activator. The TiO2 nanoparticles were synthetized using a modified sol-gel and hydrothermalmethod, with a crystallite size of the order of 10 nm and a specific surface area >250 m2/g. Transmissionelectron microscopy observations enabled the confirmation of the mesoporous structure. The nitrogendoping effect and changes in pH (pH = 3, 6 and 9) of the precursor solution was studied from photocatalytic and photoluminescence experiments. Polyurethane microcapsules were prepared using a modifiedinterfacial polymerization method. The surface topography ofthe microcapsules was observed with scanning electron microscopy, while the release efficiency was quantified using gas chromatography coupledwith mass spectroscopy. In-vitro bioassays using live mosquitoes further attested the controlled releaserepellence effect of these photocatalytic microcapsules by inhibition of these vectors. The results showedthat functionalizing the microcapsules with nanoparticles on their surface and then exposing them toultraviolet radiation effectively increased the output of citronella into the air, repelling the mosquitoes