Luminescent chemical sensing, biosensing, and screening using upconverting nanoparticles.

Upconverting nanoparticles (UCNPs) display the unique property of converting near-infrared light (with wavelengths of typically 800-1,000 nm) into visible luminescence. Following a short introduction into the mechanisms leading to the effect, the main classes of materials used are discussed. We then review the state of the art of using UCNPs: (1) to label biomolecules such as antibodies and (synthetic) oligomers for use in affinity assay and flow assays; (2) to act as nanolamps whose emission intensity is modulated by chemical indicators, thus leading to a novel kind of chemical sensors; and (3), to act as donors in luminescence resonance energy transfer in chemical sensors and biosensors.