Obtenção de nanohíbrido de liberação lenta baseado na adsolubilização de 2-undecanona em matriz lamelar de zinco

Abstract

Considering the increase in the use of agrochemicals, especially insecticides, due to the growing demand in food production, the present study proposed the development of a slow releaser through the intercalation of the surfactant species Sodium Dodecyl Sulfate (SDS) in an inorganic matrix of Zinc Hydroxy nitrate (ZHN), enabling the adsolubilization of the pheromone of interest 2-Undecanone (2-UN), aiming to increase its effectiveness since this compound has high volatility. Layered hydroxy salts (LHSs) have the general formula M2+(OH)2-x (Am-)x/m ⋅ y H2O, in which M2+ corresponds to the divalent metal cation (Zn2+) and Am- corresponds to intercalated anions; SDS, on the other hand, helps in the hydrophobicity of the interlamellar environment by providing the inclusion of neutral structures. The aggregation pheromone 2- Undecanone is released by the male specimen Lobiopa Insularis, better known as the strawberry borer, and can be used to premeditate the technique of sexual confusion, helping to combat the pest. This action contributes to the cultivation of strawberries free of toxic products. The syntheses begin with the intercalation of the SDS in the LHS matrix, generating a precursor (LHS/SDS) that was then adsolubilized with 2 mL and an excess of 25 mL of 2-UN considering the ion exchange of the system, resulting in two compounds called (LHS/SDS-2UN and LHS/SDS-2UN(EX). In addition, a sample synthesized by the research group of the Laboratory of Materials and Interface Phenomena (LAMAFI) in 2019 was also characterized to investigate changes considering storage time. For the characterization of the solids, the techniques used were X-ray diffraction (XRD), vibrational spectroscopy in the Fourier transform infrared region (FTIR), thermogravimetric analysis (TGA/DSC), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS). To evaluate the release kinetics, isothermal tests were performed at TGA at a constant temperature of 45°. The XRD results revealed an increase in the baseline distance calculated by Bragg's law concerning the ZHN – 9.8 Å being the LHS/SDS – 35.5 Å, LHS/SDS-2UN – 36.3 Å, LHS/SDS-2UN(2019) – 37.1 Å and lamellar contraction for the LHS/SDS-2UN(EX) – 33.7 Å, that is, after surfactant intercalation and pheromone adsolubilization; The incorporation of 2-UM could be confirmed in the adsolubilization structures due to the presence of the 1720 cm-1 band characteristic of C=O. The SEM/EDS results indicated the presence of plates and layers characteristic of ZHN with the compact pore filling after the synthetic processes, the presence of elements such as (C), (O), (Zn), and (S), indicating the presence of the compounds studied. The TGA/DSC indicates thermal events of dehydration, surfactant degradation, and collapse of the ZHN matrix, most of which are endothermic. There was a 25-fold increase in pheromone release time, and these data were adjusted using the Korsmeyer-Peppas and Higuchi models. It was found that storage did not significantly alter the LHS/SDS-2UN(2019) sample; the 2- UN present in the hybrids is dispensed in a considerable period, characterizing the intercalation matrices as slow releasers, providing a material that aims to contribute to the integrated management of the strawberry borer and to reduce the use of toxic insecticides.