SÍNTESE DE PIGMENTOS DE ÓXIDOS DE ZINCO POR COMBUSTÃO DE POLISSACARÍDEOS (AMIDO E Aloe vera) E SUAS PROPRIEDADES ANTIPATOGÊNICAS

Abstract

The use of polysaccharides as fuel in solution combustion synthesis (SCS) for material synthesis is a simple and low-cost method. Furthermore, the use of less polluting fuels, such as plants, contributes to a low-cost synthesis due to their renewable and easily obtainable nature, making the synthetic route more sustainable. Among the benefits of using polysaccharides as fuel, we highlight the nonviolent propagation of combustion and the development of pores in the material through the release of gases during burning. In this study, cassava starch, and Aloe vera, were evaluated as fuels for material synthesis. The objective was to synthesize zinc oxide (ZnO) and cobalt-doped zinc oxide (ZnO:Co) at different concentrations (CoxZn1-xO; x = 1, 5, 10; % by mass) for application as antiviral pigments for architectural coatings. To characterize the pigments, analyses were conducted using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), Raman spectroscopy, visible-near infrared (VIS-NIR) spectroscopy, colorimetry (CIEL*a*b* method), and advanced techniques such as X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). XRD profiles showed that the obtained oxides have the wurtzite phase as the major phase. However, the ZnO:Co oxides obtained via combustion with Aloe vera exhibited a second phase, the spinel phase of ZnCo2O4, and NEXAFS data corroborated these results. To evaluate the antiviral properties of the pigments, ZnO and ZnO:Co particles were dispersed at a ratio of 10% (w/w) in two water-based acrylic paints: an additive-free acrylic binder (binder-A) and a commercial white paint (paint-B). These paints were then applied to polycarbonate (PC) plates, and the inactivation of the SARS-CoV-2 virus was measured using the RT-PCR protocol after exposing the surfaces containing the synthesized samples to the virus according to the adapted ISO 22196:2011 method. SEM/EDS characterized the coatings, and their wettability characteristics were evaluated. The results showed that the ZnO and ZnO:Co pigments obtained from combustion with starch exhibited excellent distribution and compatibility with the paints used in this study, while the particles obtained with Aloe vera agglomerated on the surface of the coatings when dispersed in both paints. Wettability tests were performed, and the results indicated the formation of hydrophilic surfaces with the addition of pigments in binder-A (AC < 90°C). The antiviral activity of the ZnO particles dispersed in the paints was compared to a reference control sample (PC plates). According to the RT-PCR results, all the pigments exhibited antiviral activity, with the surfaces obtained by dispersing the pigments in binder-A showing the best results against the SARS-CoV-2 virus, with a virus inactivation rate exceeding 80% after 24 hours of contact compared to the reference control (PC).