研究目的
The aim of the present research is the development and characterization of a nanoinsecticide using the LAL technique. This nanoinsecticide will be synthesized from a conventional insecticide of the pyrethroids family, namely bifenthrin (the third-generation insecticides). Due to the size of the nanoparticles (<100 nm) it is expected a high effectiveness of the colloid. The small particle size and the high surface area will increase its activity compared with the micro-sized material currently of commercial use.
研究成果
It was shown the possibility of synthesizing colloidal organic nanoparticles using the laser ablation in liquids technique at different experimental conditions. The composition of the nanoparticles is the same of the starting material. The distance between the focusing lens and the target plays an important role as it defines the energy density (fluence) deposited on the target. The wavelength also plays an important role in the synthesis of the nanoparticles because the morphology can vary when this parameter is changed. Preliminary biological tests show insecticidal activity of bifenthrin nanoparticles with a significant decrease in the doses used in comparison to the doses needed when bulk bifenthrin is used.
研究不足
The stability of the nanoparticles is limited due to the agglomeration-sedimentation phenomenon. The use of high fluences induces the incorporation of big particles into the colloid, reducing the stability of the colloid. The filtration procedure to remove large particles also removes a considerable amount of nanoparticles, reducing the absorbance intensity.
1：Experimental Design and Method Selection:
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.
2：Sample Selection and Data Sources:
A target of bulk organic bifenthrin compound (agricultural insecticide) was elaborated for the ablation process.
3：List of Experimental Equipment and Materials:
A Nd:YAG laser that could be operated at 2 wavelengths; 1064 or 532 nm, 10 Hz of repetition rate, a pulse duration of 5 ns, and an output laser energy of 70 mJ. The laser beam was focused on the target surface immersed in water through a series of mirrors and a lens with 20 cm of focusing distance.
4：Experimental Procedures and Operational Workflow:
The targets were irradiated by a Nd:YAG laser. The laser beam was focused on the target surface immersed in water through a series of mirrors and a lens with 20 cm of focusing distance. The target in the beaker rotates at 15 rpm to avoid drilling.
5：Data Analysis Methods:
The optical absorbance of laser-synthesized colloidal solutions was recorded in the wavelength range from 190 to 1100 nm, using a UV–vis spectrophotometer. 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).
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