Lignin-based metal oxide nanocomposites for UV protection applications: A review

Use of agri-biomass is a promising sustainable approach for the production of functional materials while utilizing agro-biomass at the same time. In this respect, lignin derivable from agri-biomass is an economic source to generate functional biomaterials with the biocompatibility and sustainability. As such, lignin has been favorably utilized as a raw material for the preparation of various substances including metal oxide nanocomposites (MONCs). As is the case of MONCs, the applicabilities of lignin-derived MONCs should be extendible to versatile fields [e.g., Ultraviolet (UV) protection, photocatalysis, and antimicrobial agents]. Fabrication of lignocellulosic biomass as a raw material should be a plausible option for the development of UV protective material from the industrial perspective. This review aims to highlight the notable research findings (e.g., in viewpoint of lignin as an economically and environmentally better alternative to the raw chemical material for MONCs synthesis) made over the past few years. In this respect, our emphasis was placed on the development of lignin-based ZnO and TiO2 composites for UV protective applications. The use of lignin for the synthesis of MONCs is thus found as a significant technological advancement over the existing chemical-based methods. This review will also aid in expanding the future applications of lignin-based MONCs, especially with an emphasis on UV-protecting agents in diverse product forms (e.g., coatings, films, and sunscreen).