Frequency upconversion luminescence: New frontiers in bioapplications

Frequency upconversion luminescence (FUCL) is a specific anti-Stokes process whereby excitation of long wavelengths with low energy can be converted to emission of short wavelengths with high energy, which has attracted increasing attention in biological applications due to its superior features, such as low autofluorescence and excellent signal-to-noise ratios. In this review, we introduce the differences between traditional fluorescence and FUCL, summarize the composition, molecular design and characteristics of FUCL materials and conduct a survey of recent advances in FUCL systems, focusing on their broad applications in the fields of bioimaging, biodetection and cancer therapy. In addition, we further present the current challenges and perspectives with the expectation of making new breakthroughs in FUCL materials in the near future.