The chapter provides a comprehensive overview of the diverse applications of Fourier transform infrared (FTIR) spectroscopy in materials science with a particular focus on bionanocomposites. Through an analysis of various studies, it explores the instrumental role of FTIR in understanding surface functionalization of nanoparticles, hydrogel properties, nanocomposites, and the characterization of functional groups in materials such as graphene oxide, clay, chitosan, cellulose, proteins, and gelatin. Case studies highlight the efficacy of FTIR in elucidating chemical interactions, structural changes, and sorption behaviors. The chapter concludes by emphasizing the indispensable contribution of FTIR to tailoring material properties for enhanced performance across a range of applications. © 2024 Elsevier B.V., All rights reserved.