Lignocellulose Enabled Highly Transparent Nanopaper with Tunable Ultraviolet-Blocking Performance and Superior Durability

Lignin-containing cellulose nanopaper (LCNP) has emerged as a new generation of sustainable film for packaging and electronics. While compared with pure cellulose nanopaper (CNP), it still exhibits relatively lower transparency or declining mechanical performance, which greatly hinders its practical application. To address these issues, we reported a highly available route involving a TEMPO-mediated oxidation method followed by a homogenization process to prepare lignin-containing cellulose nanofibers (LCNFs) based on a lignocellulose material and then directly processed the LCNFs into a dense film (LCNP) via a mature papermaking process. Due to small fibers produced by this method, the resultant LCNP exhibits an ultrahigh visible light transmittance (∼91%) close to CNP. Moreover, the high lignin reservation (∼16%) endows the nanopaper excellent UVA-blocking efficiency (∼68%) and better environmental durability than CNP. The retaining lignin was found to serve as a reinforcing agent filled in LCNP, resulting in a significant improvement on toughness, wet mechanical property, and thermal stability. Overall, this fully biobased LCNP with outstanding performance is a promising candidate to replace conventional petroleum-based materials in the fields like flexible electronics, packaging, and protective products.