Advancement in the Synthesis and Nanocomposite Formation of Upconversion Nanomaterials in the Fluorescence Detection of Food Contaminants

To secure proper food safety, it is desirable to develop rapid, multiplexed, miniaturized, and point-of-care sensors against food contaminants. In this perspective, upconversion nanoparticles (UCNPs) are recognized as prominent candidates for sensing food contaminants with the aid of their exceptional physicochemical attributes (e.g., minimal auto-fluorescence (FL) and minimal photodamage to biological specimens). Therefore, this review delineates the structural and functional attributes of UCNPs with brief descriptions on their synthesis methods. The manuscript further addresses various strategies for the synthesis of the UCNPs and the formation of their nanocomposites with other materials for the sensing applications toward a variety of food impurities (e.g., heavy metals, mycotoxins, pathogenic bacteria, pesticides, polychlorinated biphenyls, and antibiotics). This review also summarizes the performance of UCNP-based biosensors in terms of key parameters (e.g., assay time, storage stability, detection limit, linear detection range, and figure of merit) along with the discussions on the technical challenges and future prospects towards food safety monitoring. Accordingly, this review highlights the practical utility of UCNPs for safeguarding food securities in foreseeable future.