Engineering luminescent metal nanoclusters for sensing applications

Metal nanoclusters (MNCs) have ultrasmall size (≤3 nm), precise molecular structure, strong luminescence, size-sensitive physicochemical properties, engineerable metallic composition, and rich yet tailorable surface chemistry, enabling them to be promising for the construction of luminescent sensors for diversified sensing applications in fields of environmental protection, food safety, agriculture, disease diagnosis, biomarker identification, etc. However, a systematic summary is urgently needed to correlate the physicochemical properties of MNCs with their influences on sensing applications, to summarize the synthetic strategies of highly luminescent MNCs towards sensor construction, and to discuss the general configurations and sensing mechanisms of MNCs-based luminescent probes. In this review, we first discuss relevant physicochemical properties of MNCs that may have major influences on the sensing mechanisms/performance of MNCs-based luminescent sensors, and then summarize the main synthetic strategies of highly luminescent MNCs. Then, we briefly illustrate the general configurations of MNCs-based sensors, and elaborately clarify their sensing mechanisms with the exemplification of representative sensing applications. We conclude the review with our perspectives on the opportunities/challenges of MNCs-based luminescent sensors. It is believed that this review will shed light on the design of MNCs-based luminescent sensors for future sensing applications.