Obtenção e caracterização de nanocompósitos prata/argila organofílica

Abstract

The aim of this work was to investigate the application of organoclay as support in the synthesis of silver nanoparticles focusing the increase of the antimicrobial activity of Ag-montmorillonite nanocomposite (Ag-MMT). The experimental work development consists of the following steps: removal of organic matter with hydrogen peroxide and modification of the basal spacing of the clay with cetyltrimethylammonium bromide. To obtain the purified and the organoclay Ag-MMT nanocomposite, silver nitrate (AgNO3) and sodium borohydride (NaBH4) were used as the precursor of silver and reducing agent for Ag+ adsorbed on clays, respectively. The properties of nanocomposites were studied in function of the concentration of the solution of AgNO3 (0.005 M, 0.01 M, 0.02 M, 0.05 M and 0.1 M) and in function of the concentration of NaBH4 (0.001 M, 0.005 M and 0.01 M). Another synthesis route to prepare nanocomposite was used to compare the ability of adsorbing silver nanoparticle from a previously prepared colloid. Adsorption data were fitted in Langmuir and Freundlich isotherms, but the best correlation coefficient (R²) was obtained by the Langmuir model. It indicates that Ag+ adsorbed on the purified MMT and organoclay surface formed predominantly a monolayer. The X-ray Diffraction shows that the purified MMT structure was gradually exfoliated with the increase of AgNO3concentration, while the organoclay structure remained intact. Samples of Ag+-MMT were reduced with NaBH4 to produce Ag0 and were observed with UV-vis spectra that particle diameter is dependent on the concentration of NaBH4. The Ag-MMT organoclay nanocomposite showed higher antimicrobial activity in the bacterium Escherichia coli due to higher concentration of silver nanoparticles present in the structure. The adsorption process B showed that increasing the basal spacing with alkylammonium ion contributed to increased adsorption of Ag0.