Upconversion Nanoparticle-Organic Dye Nanocomposites for Chemo- and Biosensing

The emerging nanocomposite of lanthanide-doped upconversion nanoparticles (UCNPs) and organic dyes (ODs), which combines the advantages of each component, possesses a series of attractive properties, making the nanocomposite suitable for sensing. With the rising demand for chemo- and biosensing, a variety of sensors based on UCNP-OD nanocomposites have been developed for various analytes. The recent evolution of UCNP-OD-based sensors has enabled the detection of targeted analytes in situ, in vitro, and in vivo. In this review, beginning with a brief introduction to the fabrication and working principles of UCNP-OD-based sensors, we discuss UCNP-OD-based sensors for chemo- and biosensing. Concentrating on recent representative examples, we review UCNP-OD-based sensors for detecting different analytes, including ions, reactive oxygen species, reactive nitrogen species, gases, and biomolecules, by paying particular attentions to the design strategies and working principles. We lastly point out some remaining challenges and potential directions for the further development of UCNP-OD-based sensors.