Emerging applications of natural dyes and pigments: A review

Natural dyes and pigments are attracting renewed scientific interest as sustainable alternatives to synthetic colorants due to growing environmental and health concerns associated with conventional dyes. Unlike many synthetic counterparts, natural pigments are generally biodegradable, biocompatible, and derived from renewable bio-resources, making them attractive for emerging technological applications beyond traditional textile and food industries. This review provides a comprehensive overview of the sources, chemical classification, extraction techniques, and functional properties of natural dyes and pigments, with emphasis on their roles in renewable energy, biomedical, and sensing technologies. Advanced extraction strategies, including supercritical fluid extraction, microwave-assisted extraction, and solid-phase extraction, are discussed in relation to pigment stability, purity, and structure–property relationships that govern functional performance. Particular focus is placed on the application of natural pigments as photosensitizers in dye-sensitized solar cells, where molecular structure, anchoring groups, and interfacial interactions with semiconductor photoanodes critically influence charge transfer and device efficiency. The biomedical potential of natural dyes as photosensitizers and fluorescent probes for cancer imaging and photodynamic therapy is also examined, highlighting their intrinsic photochemical activity and reduced cytotoxicity compared to synthetic agents. In addition, recent advances in colorimetric and fluorescence-based sensing and biosensing platforms utilizing natural pigments are reviewed, demonstrating their responsiveness to environmental and biological stimuli. Finally, current limitations related to stability, scalability, and resource sustainability, are critically assessed, and future research directions are proposed to enable the translation of natural pigment-based systems from laboratory studies to practical, environmentally responsible technologies. • Natural dyes and pigments offer sustainable alternatives to synthetic colorants for advanced technologies. • Green extraction methods strongly influence pigment stability, purity, and functional performance. • Molecular structure and anchoring groups govern electron injection efficiency in DSSC photoanodes. • Natural pigments exhibit strong potential as photosensitizers and fluorescent probes in cancer therapy. • Colorimetric and fluorescent responses enable effective sensing and biosensing applications. • Stability, scalability, and resource sustainability remain key challenges for industrial translation.