Dual-Fiber Approach toward Flexible Multifunctional Hybrid Materials

Multifunctional paper-like materials containing metal oxide nanofibers are important for flexible electronics and other redox-based applications, but are often prone to mechanical failure. This work presents the coassembly of V2O5 nanofibers (VNFs) in a dual-fiber approach together with cellulose nanofibers to produce tough (0.26 MJ m−3), but strong (250 MPa) flexible hybrid materials. Indeed, nanotensile tests reveal a significant increase in toughness (200%) and strength (85%) of the hybrid films as compared to pristine VNF films. The microstructure of the films shows a transition from an anisotropic texture for the single-component films to an isotropic, entangled network in case of the hybrid films, which facilitates effective fracture resistance mechanisms. The flexible hybrid films display high electrical conductivity (0.2 S cm−1) and elastic properties originating from V2O5 nanofibers with excellent toughness and transparency endowed by the cellulose nanofibers. The self-supported hybrid films show reversible electrochromic behavior without the need for common substrates such as conducting indium tin oxide glass. It is conceivable that these self-supported films can be exploited in the future in smart, flexible optoelectronic devices.