A B S T R A C TThe addition of silver (Ag) into the chemical synthesis of materials, transform them into materials technologically relevant to be used as antimicrobial additives. In this work, the sol-gel method was used to obtain materials based on silica and zirconia, with the inclusion of Ag. The solids were characterized by potentiometric titration, specific surface area (S BET ), X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and, the antifungal activity of the additives was assessed by agar plate inhibition against Chaetomium globosum and Alternaria alternata. In addition, the resistance to fungal growth on waterborne coatings was evaluated after the incorporation of the solids into paint formulation.Amorphous materials with different acidic and textural properties were obtained. Most of the tested solids showed antifungal activity at the highest concentration used, and the presence of Ag increased the percentage of inhibition. The mixed oxides Ag-additives improved the antifungal activity compare with the pure Ag-oxides (silica or zirconia). In this sense, a synergic effect between zirconia/silica and silver would be a promising result that would reduce the amount of silver in these bioactive materials. This work was performed as a preliminary study, in order to guide the selection of a suitable additive from a list of possible antifungal agents.

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In this work, the one-pot sol-gel synthesis of novel siliceous matrixes doped with carbon from spent batteries is reported. The obtained solids with silver nitrate were characterized by their antifungal activity against Aspergillus sp., Cladosporium sp. and Chaetomium globosum, three well-known cellulolytic microorganisms responsible for the deterioration of cotton fabric. In this research it was possible to develop a methodology for the impregnation of cotton fabrics (brin type) and to evaluate the antifungal efficacy. Cotton fabric containing the highest amount of carbon showed the highest antifungal activity against C. globosum and Aspergillus sp. This may be because as the amount of carbon in the silica increases, there is an increase in the surface area that facilitates an effective distribution of the active phase to act, inhibiting the fungal growth.

This study focused on the use of citrus bio-waste and obtention of silica-based materials through the sol-gel technique for promoting a greener and more sustainable catalysis. The sol-gel method is a versatile synthesis route characterized by the low temperatures the materials are synthesized in, which allows the incorporation of organic components. This method is carried out by acid or alkali hydrolysis combined with bio-waste, such as orange and lemon peels, generated as co-products in the food processing industry. The main objective was to obtain silica-based materials from the precursor TEOS with different catalysts—acetic, citric and hydro-chloric acids and ammonium hydroxide—adding different percentages of lemon and orange peels in order to find the influence of bio-waste on acids/alkali precursor hydrolysis. This was to partially replace these catalysts for orange or lemon peels. The solids obtained were characterized with different techniques, such as SEM, FT₋IR, potentiometric titration and XRD. SEM images were compared with pure silica obtained to contrast the morphology of the acidic and alkali hydrolysis. However, until now, few attempts have been made to highlight the renewability of reagents used in the synthesis or to incorporate bio-based catalytic processes on larger scales.