In situ synthesis of Cu/Cu2O nanoparticles on the TEMPO oxidized cotton fabric

Abstract

Recent breakthrough in nanotechnologies had large impact on research in the field of medical textiles. So far many efforts have been made to fabricate antimicrobial textile materials with incorporated metal (Ag, Cu) and metal oxide (TiO2, ZnO, CuO, Cu2O) nanoparticles (NPs) and to learn more about the mechanism of their action1-3. The possible application of Cu, CuO and Cu2O NPs for antibacterial protection of cotton fabrics became the focus of many research groups since the copper in different forms (ionic, copper oxides, copper complexes) is very active against various bacterial strains and precursor salts of copper are much cheaper than those of silver. Unlike in the case of Ag NPs where the dip-coating from Ag NPs suspensions/colloids was mostly applied for nano-finishing of cotton fabrics, in situ synthesis of Cu, CuO and Cu2O NPs seems to be the method of choice in published studies until now4,5. Namely, the dominant approach relies on the introduction of carboxyl groups to cotton fibers by coating them with appropriate polymer or chemical modification of cellulose, adsorption of Cu2+-ions and their reduction. In our study we applied the TEMPO/NaClO/NaClO2 system under neutral conditions for selective oxidation of cellulose in order to enhance its ability to bind Cu2+-ions. We focused our study on much shorter oxidation times since the aim was to preserve the structure of cellulose fibers i.e. their mechanical strength. Therefore, the main goal of our study was to discuss the influence of the functional groups generated by TEMPO-mediated oxidation of cotton fabric at different reaction times on the amount, activity and stability of in situ synthetized Cu/Cu2O NPs using sodium borohydride as a reducing agent at room temperature.

In situ sinteza nanočestica Cu/Cu2O na pamučnoj tkanini diskutovana u ovom radu bazirana je na adsorpciji Cu2+-jona na karboksilnim grupama formiranim TEMPO oksidacijom celuloze i njihovoj redukciji natrijum-borhidridom. Hemijske promene nastale TEMPO oksidacijom su praćene titrimetrijski određivanjem sadržaja karboksilnih grupa u pamuku. Prisustvo nanočestica Cu/Cu2O na pamučnoj tkanini potvrđeno je SEM i AAS analizama. Promene obojenja tkanina su određene refleksionom spektrofotometrijom. Antibakterijska aktivnost generisanih nanočestica Cu/Cu2O je testirana prema Gram-negativnoj bakteriji E. coli i Gram-pozitivnoj bakteriji S. aureus. Produžavanje vremena TEMPO oksidacije za rezultat je imalo povećanje sadržaja karboksilnih grupa na pamučnoj tkanini. Stoga su veće količine Cu2+-jona mogle da se adsorbuju na supstratu. Ovo je dalje za posledicu imalo stvaranje većih količina nanočestica Cu/Cu2O. Svi ispitivani tekstilni nankompoziti su obezbedili maksimum redukcije bakterija E. coli i S. aureus. Takođe je utvrđeno da pamučne tkanine sa inkorporiranim nanočesticama Cu/Cu2O pružaju kontrolisano otpuštanje Cu2+ -jona u fiziološkom rastvoru što je imperativ za prevenciju infekcija.