Adaptable lignin-containing cellulose nanofibers: A design approach toward high-performance green electronics.

The growing demand for sustainable technology development has generated considerable interest in environmentally friendly lignin-containing nanocellulose fibers (LCNFs). Cellulose nanofibers (CNFs) have attracted attention as promising materials owing to their exceptional mechanical strength, flexibility, and optical transparency. However, their practical applications are hindered by energy-intensive production processes and poor water stability. To overcome these limitations, LCNFs are developed using a cost-effective deep eutectic solvent (DES) treatment. The optimized lignin-containing cellulose nanopapers demonstrated outstanding mechanical properties (tensile strength of 198.5 MPa, Young's modulus of 13 GPa), high optical transmittance (79.8 % at 550 nm, haze of 40 %), and improved water resistance. Conductive LCNF papers were also developed by coating them with silver nanowires (AgNWs) for transparent electrodes and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) for water-resistant electrodes. The AgNW-coated LCNF papers exhibit a low sheet resistance of 40.1 Ω sq.-1 while maintaining a high transmittance of 75.1 % at 550 nm. Notably, the PEDOT:PSS-coated LCNFs preserve excellent electrical properties (sheet resistance: 6.6 Ω sq.-1) even after 24 h of water immersion, demonstrating superior wet stability compared to traditional CNF-based electrodes. These findings highlight the potential of lignocellulosic biomass, such as LCNFs, as a viable alternative to conventional CNFs for a wide range of practical applications.