Upconversion fluorescent nanoparticles technology in food inspection

Upconversion fluorescent nanoparticles technology) is a new emerging technique that has attracted increasing attention in recent years. Compared with other labeling techniques such as radioisotopic labeling, enzymatic labeling, chemiluminescent labeling, organic fluorescent dyes, and quantum dots (QDs), upconversion fluorescence nanoparticles have unique advantages such as high photostability, high detection sensitivity, good selectivity, easyobservation and operation, no damage to the sample, and no background fluorescence. In addition, this technique has overcome several shortcomings of other prevalent methods, such as radioactive contamination, enzyme-instability, poor sensitivity, and poor reproducibility of chemiluminescence. It has been widely applied to imaging studies of cells and tissues, quantitative detection of biomolecules, etc., and has achieved remarkable outcomes. In this study, three upconversion mechanisms of UCNPs (e.g., excited-state absorption), their composition, four preparation methods (e.g., hydrothermal method), and six surface modification methods (e.g., Stober method) were reviewed. Subsequently, it provides a perspective to the application of UPNT in food inspection.