Extending Near-Infrared Bioimaging Window Beyond 1500 nm.

Luminescent bioimaging has recently emerged as a crucial and indispensable tool for in vivo visualization and detection. Notably, due to significantly reduced photon scattering and minimal autofluorescence characteristic of the photon wavelength beyond 1500 nm, in vivo luminescent bioimaging offers enhanced capabilities, enabling the visualization of fine anatomical structures with superior tissue penetration depth and high spatial-resolution. In this regard, this review highlighted the recent significant progress of extending the high-resolution bioimaging window beyond 1500 nm and the corresponding novel luminescent materials. First, we systematically summarized the theoretical simulations that investigated potential superior bioimaging windows, including the 1500-1900 nm and 2100-2500 nm regions. Within such an extended region beyond 1500 nm, we then comprehensively concluded strategies for design of novel luminescent materials engineered for emission wavelength beyond 1500 nm, which included organic dyes with specific and large conjugated structures, quantum dots with size-tunable emission spectra, lanthanide-based nanocrystals, and complexes emitted from f-f transitions. Subsequently, pioneering opportunities that exhibited superior in vivo bioimaging performance for biomedical applications were analyzed across volumetric bioimaging and wide-field multiplexed bioimaging. Despite these promising achievements, opportunities for next-generation bioimaging windows and challenges in clinical translation were objectively discussed at last.