Visible to mid IR: A library of multispectral diagnostic imaging

Fluorescence imaging is an essential and interdisciplinary optical technique that uses light signals from molecules, cells, and living organisms to visualize dynamic biological processes. Moreover, with recent remarkable breakthroughs in the development of chemical mechanisms (e.g., aggregation-induced emission, donor-π-acceptor electron manipulation for near IR region II fluorescence emission, multi-photon absorption and molecular rotor), nanofabrication technologies, and newly discovered biomarkers, the opportunities to generate multifunctional bespoke probes for the rapid analysis and highly accurate diagnosis of early-stage cancers have increased. In this article, we mainly review the recent advances in some representative small molecule-based fluorescence probes and their nanocomposites with an emphasis on the design principles to enhance the recognition selectivity/sensitivity, improve the signal-to-background ratio, amplify the fluorescence emission brightness, and optimize the tissue penetration depth. Furthermore, we highlight the current challenges and further opportunities from the viewpoint of the practical applications of this emerging field.