Quenching of the Luminescence of Upconverting Luminescent Nanoparticles by Heavy Metal Ions (original) (raw)

2011, Chemistry a European Journal

AI-generated Abstract

We report that the luminescence of upconverting luminescent nanoparticles (UCLNPs) is quenched by heavy metal ions and halide ions in aqueous solution. The UCLNPs consist of hexagonal NaYF 4 nanocrystals doped with trivalent rare earth ions and were synthesized by both the oleic acid (solvothermal) method and the ethylenediaminetetraacetic acid (coprecipitation) method. Quenching was studied for the Cu II , Hg II , Pb II , Cd II , Co II , Ag I , Fe III , Zn II , bromide, and iodide ions and is found to be particularly strong for Hg II . Stern-Volmer plots are virtually linear up to quencher concentrations of 10-25 mm, but deviate from linearity at higher quencher concentrations, because static quenching causes an additional effect. The UCLNPs display two main emission bands (blue, green, red or near-infrared), and the quenching efficiencies for these are found to be different. The effect seems to be generally associated with UCLNPs because it was observed for all UCLNPs doped with trivalent lanthanide ions including Yb III UCLNPs have found applications in chemical sensing, labeling of biomolecules, in enzymatic and affinity assays, and in intracellular sensing of temperature because of their brightness and other attractive features. Despite many studies on the spectral properties of UCLNPs, it is rather surprising that the quenching of their luminescence by heavy metal (HM) ions has not been investigated so far. It is known that UCLNPs undergo surface-quenching effects associated with the size-dependent luminescence, but this is not related to external quenchers. We report here, for the first time, that the luminescence of UCLNPs nanocrystals is strongly quenched by HM ions. We also discuss the mechanism of quenching and envision applications of this new effect.