Fluorescent Metal Nanoclusters for Bioimaging Applications in the NIR

Metal nanoclusters (NCs) stabilized by organic ligands have emerged as highly promising fluorescent probes for bioimaging. Their ultrasmall size, molecular-like photoluminescence, and tunable emission make them attractive alternatives to conventional dyes and larger nanoparticles. This chapter focuses on NCs emitting in the near-infrared region (NIR), particularly the NIR-I (650–900 nm) and NIR-II (1000–1700 nm) windows, which offer advantages such as reduced tissue autofluorescence, enhanced imaging depth, and improved signal-to-background ratios. The chapter systematically reviews applications of NIR-emitting NCs in in vitro, ex vivo, and in vivo imaging, highlighting advances in cellular targeting, biodistribution, and real-time imaging. Particular attention is given to gold NCs due to their biocompatibility and versatile emission profiles. These properties collectively position NIR-emitting NCs as strong candidates for future use in clinical bioimaging applications.