Lignin nanoparticles: Preparation strategies, surface engineering, and emerging applications-A review

Lignin nanoparticles (LNPs) are renewable nanomaterials that translate the aromatic, antioxidant, and UV-absorbing chemistry of lignin into a more processable nanoscale form. Compared with bulk lignin, LNPs offer improved dispersibility, higher accessible surface area, tunable interfacial chemistry, and better compatibility with polymeric, biological, catalytic, and environmental systems. This review critically examines LNPs from a source-process-structure-performance perspective rather than treating preparation, surface engineering, and applications as separate topics. We discuss how lignin origin, isolation history, fabrication route, and surface modification govern particle formation, colloidal stability, redispersion behavior, and functional performance. Particular attention is given to the distinction between the intrinsic contribution of LNPs and the activity introduced by grafted, loaded, or hybridized components. Emerging applications in biomedical delivery, catalysis, environmental remediation, coatings, packaging, and functional composites are assessed with emphasis on practical relevance and current limitations. Finally, key challenges involving feedstock heterogeneity, mechanistic understanding, quantitative surface descriptors, reproducible manufacturing, safety evaluation, and industrial translation are highlighted. This review provides an integrated framework for the rational design and high-value utilization of lignin-based nanomaterials.