The University of Manchester, UK
Title: Detection of aqueous uranyl (VI) species using rare-earth upconversion nanophosphors
Biography: Aruna Reddy
Upconverting nanophosphors (UCNPs) are typically composed of an inorganic lattice doped with luminescent lanthanide ions and demonstrate the ability to convert long-wavelength excitation in the near-infrared (with wavelengths of typically 800-1000 nm) into higher energy visible luminescence. Such materials display several advantages in analytical applications, in comparison to other fluorophores, including low autofluorescence and scattering of excitation radiation, reducing background noise. Lanthanides display multiple very specific emission bands allowing careful tuning of the emission profile of the UCNPs. These properties make them suitable candidates as the donor species in luminescence resonance energy transfer (LRET) in chemical sensors and biosensors. This project details the design of a chemical sensor based on Gd4O2S:Yb,Tm and Gd4O2S:Yb,Er UCNPs. A proof of principle technique for the detection of uranyl(VI) species in aqueous solutions has been developed. Luminescence resonance energy transfer efficiency is used to sense these species. Tm3+ and Er3+ doped upconversion nanophosphors exhibit emission bands at 475 nm and 410 nm respectively, which can be monitored by ratiometric analysis, relative to other emission bands. Recent work consists of improving the sensitivity of the current system to detect lower concentration of uranyl(VI) species.