Flexible TEMPO-cellulose/silver selenide nanocomposites with advanced optical, electrical, and antimicrobial performance

Abstract

Transforming dielectric polymers into conductive or semiconductive materials opens new avenues for advanced and unprecedented applications. Herein, flexible films were fabricated from TEMPO-oxidized cellulose nanofibers/silver selenide (T-CNF/Ag₂Se) nanocomposites. Ag₂Se particles were in situ prepared in the presence of TEMPO-oxidized cellulose nanofibers to limit the Ag₂Se formation within the nanopores of the TEMPO-oxidized cellulose nanofibers. XRD and FTIR patterns verified the effective embedding of Ag₂Se nanoparticles within the T-CNF matrix, where Ag₂Se crystallized exclusively in the orthorhombic β-Ag₂Se phase. For optoelectronic applications, the optical features were investigated, and Ag₂Se has a great impact on transmittance, reflectance, optical band gap, and Urbach energy of CNF. The transmittance was reduced from 10% to 2% in the visible region, while the optical band gap dropped from 4.46 eV for CNF to 2.65 eV for CNF/Ag₂Se I. Compared with pure CNF, the CNF/Ag₂Se I nanocomposites showed broader M″ peaks that shifted towards higher frequencies, indicating enhanced charge-carrier dynamics due to the additional conductive pathways introduced by the Ag₂Se nanoparticles. At 313 K, conductivity followed the order of CNF < CNF/Ag₂Se III < CNF/Ag2_Se < CNF/Ag₂Se II < CNF/Ag₂Se I, with the conductivity increased by three orders of magnitude for CNF/Ag₂Se I compared with that for the pure CNF. The antimicrobial performance of CNF/Ag₂Se at different concentrations was evaluated, and it exhibited high toxicity against E. coli, S. typhimurium, and C. albicans, while S. mutans exhibited more resistance against the nanocomposite materials.