A Comprehensive Review on Recent Advances in Chitosan and Graphene Oxide Nanocomposites for Environmental, Biomedical and Smart Material Applications

Chitosan–graphene oxide (CS–GO) nanocomposites combine the biodegradability, biocompatibility, cationic character, and film-forming ability of chitosan with the high surface area, oxygen-rich functionality, mechanical reinforcement, and tunable physicochemical properties of graphene oxide, enabling applications in environmental remediation, biomedical engineering, food packaging, sensing, and smart materials. This review critically examines recent advances in CS–GO preparation, interfacial chemistry, characterization, structure–property relationships, sustainability, scale-up, and application performance, with particular emphasis on chitosan molecular weight and degree of deacetylation, GO oxidation level and loading, dispersion, cross-linking, and processing conditions. Hydrogen bonding, electrostatic attraction, covalent coupling, coordination, and π–π interactions govern CS–GO assembly and strongly influence mechanical, adsorption, biological, barrier, electrical, and multifunctional behavior. Environmental remediation and biomedical applications currently have the strongest evidence base, while emerging uses include microplastic capture, desalination, sensing, supercapacitors, proton-exchange membranes, and hydrogen-generation catalysis. Key challenges include inconsistent characterization, limited real-matrix validation, regeneration cost, nanoparticle migration, long-term toxicity, life-cycle impacts, and scalable green manufacturing. Future translation requires standardized characterization, application-specific safety assessment, real-world validation, life-cycle evaluation, and reproducible large-scale fabrication.