Synthesis and characterization of silver-rich coatings loaded with functionalized clay nanoparticles

Abstract

A synthetic exfoliated nanoclay smectite type, Laponite® S482, was incorporated as a functionalized load in a silica hybrid matrix synthesized by the sol–gel route. The previous functionalization was carried out through a “grafting” reaction with (3-glycidoxypropyl)trimethoxysilane (GPTMS) assisted by ultrasonic dispersion. The precursor sols were synthesized by acid-catalyzed hydrolytic condensation between tetraethoxysilane (TEOS) and functionalized GPTMS, a silver ions source was added in order to obtain a coating material with controlled silver releasing properties. Coatings were obtained by “dip-coating” on different substrates. Structural characterization of the coatings was conducted by SAXS and SEM-EDS, the results revealed a complex silica matrix with intercalated nanoclays, an organic fraction and a homogeneous content of Ag+. The electrochemical characterization was realized by EIS tests on stainless steel coated substrates AISI 316L type; the results showed good barriers properties and a high integrity of the coatings loaded with nanoclay. The evolution of the release of Ag+ ions was studied by XRF, through exposing the coatings to a leaching process at steady state and determining the residual content of Ag within the coat at different immersion times. It was found that the addition of 1.5 wt. % of clay, in respect to condensed silica, decreased the initial diffusion rate of Ag+ ions at near the half part, allowing its potential use in the development of antibacterial coatings with longer terms of life.