{Reference Type}: Journal Article {Title}: A Comprehensive Review on Upconversion Nanomaterials-Based Fluorescent Sensor for Environment, Biology, Food and Medicine Applications. {Author}: Jiang W;Yi J;Li X;He F;Niu N;Chen L; {Journal}: Biosensors (Basel) {Volume}: 12 {Issue}: 11 {Year}: Nov 2022 17 {Factor}: 5.743 {DOI}: 10.3390/bios12111036 {Abstract}: Near-infrared-excited upconversion nanoparticles (UCNPs) have multicolor emissions, a low auto-fluorescence background, a high chemical stability, and a long fluorescence lifetime. The fluorescent probes based on UCNPs have achieved great success in the analysis of different samples. Here, we presented the research results of UCNPs probes utilized in analytical applications including environment, biology, food and medicine in the last five years; we also introduced the design and construction of upconversion optical sensing platforms. Future trends and challenges of the UCNPs used in the analytical field have also been discussed with particular emphasis.