Acid hydrogel matrixes as reducing/stabilizing agent for the in-situ synthesis of Ag-nanocomposites by UV irradiation: pH effect

Abstract

Synthetic methods to obtain Ag-nanocomposites are widely studied in order to produce antimicrobial materials without using harmful agents for possible applications in biologic systems. In this way, the nanocomposites could be able to apply in biomedicine area avoiding going through exhaustive processes of purification. Biocompatible hydrogel based on N-isopropylacrylamide (NIPAM) copolymerized with different proportions of methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), were proposed as matrixes of Ag-nanocomposites. A comprehensive study of the physicochemical behavior, reducing and stabilizing character of the matrixes were carried out at pH 2 and 7. Hydrogel nanopores were used as photoreducing of Ag+ ions and stabilizing of Ag nanoparticles (Ag-NPs) at the same time. Most of the matrixes showed high reducing character at pH 7 while at pH 2 it was significantly reduced. Photoreducer character at pH 7 increased with MAA co-monomer concentration and Ag-NPs sizes of 4–5 nm were obtained. In addition, it was demonstrated that acidic co-monomers favor the stabilization of Ag-NPs avoiding agglomerations. It was possible to conclude that the photoreduction reaction takes mainly place at pH 7 when non bonding electron pairs from carboxylic and amide groups of the matrix are available. Therefore, biocompatible and antimicrobial nanocomposites can be easily synthesized without using damaging additives (reducer, solvent) and be applied in biomedicine.