EDITORA CIENTÍFICA DIGITAL LTDA 
2021
Ciência e engenharia de materiais: conceitos, fundamentos e aplicação
Priscyla Lima de Andrade and Iara Margolis Ribeiro et Al.

Abstract

In the work reported here, we investigated the surface topography and the electrocatalytical ability toward hexazinone herbicide of a hybrid organically modified silicate (ormosil) film using (3-aminopropyl)triethoxysilane and phosphotungstic acid (HPW), a polyoxometalate (POM) nanocluster. The morphology of the film on gold electrode was studied with a recent surface analysis technique based on atomic force microscopy coupled with infrared absorption spectroscopy. This hybrid ormosil film showed nanopores distributed throughout the surface and the interaction between HPW clusters and amine groups was electrostatic. The electrocatalytic reduction of hexazinone occurred at −0.20 V vs. Ag/AgCl in acidic medium pH 0.80 as shown by cyclic voltammetry analyses. Solid state 29Si nuclear magnetic resonance analyses showed that the distribution of silicate groups in the ormosil is formed by Q3 and Q4 species. Since a sensor for hexazinone was not aimed here, this system studied can contribute to the improvement of useful materials in environmental science research.

Link to surce: https://www.researchgate.net/profile/Iara-Ribeiro-6/publication/354596183_Ciencia_e_Engenharia_de_Materiais_conceitos_fundamentos_e_aplicacao/links/617391a8a767a03c149a7114/Ciencia-e-Engenharia-de-Materiais-conceitos-fundamentos-e-aplicacao.pdf

Ormosil and Film Preparations

This procedure was similar to described by (OLÍVIO et al., 2018). In a polypropylene
beaker, 25 mL of acetone, 0.25 mmol (59 µL) of (3-aminopropyl)triethoxysilane (APTS), 0.26 mmol (58 µL) of tetraethyl orthosilicate (TEOS), 0.78 mmol (14 µL) of deionized water and 100 µL of an aqueous solution of sulfuric acid (pH 0.8) were mixed and stirred for 15 minutes. Afterwards, 0.040 mmol (115 mg) of phosphotungstic acid hydrate (HPW) dissolved in 25 mL of acetone was added to the mixture. The stirring was maintained for an additional 15 minutes and the final solution was used to prepare the ormosil film.

Slides of glass coated with gold 3 cm × 1 cm in size were used as substrates. Ormosil
films were prepared using a dip coater elevator from Nadetech Innovations. The slide was immersed and removed from the ormosil solution at a speed of 150 mm min–1. When the slide was fully immersed in the solution, it was immediately withdrawn resulting in an immersion time near to zero. This cycle was repeated 20 times and after each withdrawal the slide was kept in the air for 60 s to dry.