Sensors and bioassays powered by upconverting materials

In recent years, considerable efforts have been done to better understand the peculiar emission properties of upconverting materials due to their widespread applications in different and important technological fields such as upconversion-based photoactivated cancer therapies, photoactivated drug-delivery, magnetic resonance imaging contrast agents, bioimaging. However, one of the most promising applications of upconverting materials concerns the field of sensing, due to their unique emission properties. In fact, the minimal autofluorescence, blinking, photo-bleaching, and high photostability makes them an excellent alternative to organic dyes or quantum dots. This article reviews the state-of-the-art, design, and sensing strategies of upconversion-based sensing platforms, with special attention to upconverting nanoparticles, as well as how the incorporation of these materials into pre-existing diagnostic tests and bioassays have improved their capabilities for the detection of different kinds of analytes. [Display omitted] •Heterogeneous assays in sensors based on upconverting nanoparticles (UCNPs)•Homogenous assays in sensors based on resonance energy transfer and UCNPs•Optical cellular pH sensors, nano-thermometers, and gas sensors based on upconverting nanoparticles•Overview of the next generation of UCNPs, future challenges and limits for their applications