Preparation and characterization of organic nanoparticles by laser ablation in liquids technique and their biological activity

The laser ablation in liquids (LAL) method was used for the synthesis of organic colloidal nanoparticles in deionized water as a liquid medium. The effect of variations of the lens-target distance and laser wavelength on the size, structure, and morphology of the nanoparticles was studied. A target of bulk organic bifenthrin compound (agricultural insecticide) was elaborated for the ablation process. By means of ultraviolet-visible (UV-vis) absorption spectroscopy, the characteristic absorbance spectra were analyzed, confirming the presence of nanoparticles. Furthermore, the absorbance was related to the nanoparticles concentration. Structural characterization and size determination were carried out by transmission electron microscopy (TEM). The crystalline structure of the nanoparticles was studied by comparing the interplanar distance of the nanoparticles determined by high-resolution transmission electron microscopy (HR-TEM) with the interplanar distances of the bulk material observed by x-ray diffraction (XRD). The study of chemical composition was carried out by gas chromatography coupled to mass spectrometry (GC-MS). The nanoparticles sizes varied between 3 and 20 nm, with a narrow size distribution. According to the results, both the size and structure of the nanoparticles are mainly determined by the incident energy density on the target, whilst wavelength affects morphology. On the other hand, the preliminary biological tests of the nanoparticles carried out with Drosophila melanogaster, showed an enhanced insecticide activity at significant lower concentrations in comparison with doses used with bulk bifenthrin.