Sonochemically activated synthesis of gradationally complexed Ag/TEMPO-oxidized cellulose for multifunctional textiles with high electrical conductivity, super-hydrophobicity, and efficient EMI shielding

Abstract

With growing concerns over electronic device malfunction and the resulting information loss caused by electromagnetic interference (EMI), extensive studies have been performed in developing EMI shielding techniques. In particular, developments in flexible and wearable electronics have drawn great interest in EMI shielding textiles. However, conventional electro-conductive textiles prepared by the coating of a conductive layer over the textile core have suffered from durability issues over repeated use as well as their relatively poor electrical conductivity. To address these problems, we present a novel method of directly growing the Ag layer onto the cellulose textile surface even without the use of any polymeric binder or adhesive species. To this end, TEMPO-mediated oxidation as an effective means to selectively convert the hydroxymethyl to carboxyl moieties in cellulose textiles was used under sonochemical activation, and the synthesis of Ag nanoparticles (NPs) was subsequently carried out to form a uniformly coated Ag layer around the TEMPO-oxidized cellulose (TOC). Since Ag NPs were generated from the interior region of the TOC and propagated outward, a gradationally changing profile in Ag concentration along the cross-section of the textiles was developed. Therefore, this strongly anchored Ag coating layer on the cellulose surface would ensure remarkably high mechanical durability and a very low sheet resistance of 1.02 Ohm sq⁻¹ of Ag/TOC textiles. Finally, investigation of the EMI shielding performances of Ag/TOC textiles confirmed a shielding efficiency of 47 dB (a single Ag/TOC layer with a 188 μm thickness), which could be further improved to 69 dB with a triple stack.