Amine functionalized NaY/GdF4:Yb,Er upconversion-silver nanoparticles system as fluorescent turn-off probe for sensitive detection of Cr(III)

In this work, a label-free fluorimetric method for sensitive and selective detection of Cr(III) was developed by utilizing NaY/GdF 4 :Yb,Er upconversion nanoparticles (UCNPs) and citrate-modified silver nanoparticles (Cit-AgNPs) mixed system. The photophysical and morphological properties of the prepared UCNPs were characterized by various spectroscopic and microscopic techniques. The fluorescence of amino-modified UCNPs can be quenched due to the Cr(III) induced aggregation of Cit-AgNPs by means of inner filter effect. The observed quenching in the fluorescence intensity of the UCNPs is found to be dependent on the concentration of Cr(III). The fluorescence decreases linearly within the investigated concentration of 0.5–40 μM Cr(III) with a limit of detection 34 nM. The practical applicability of the present sensing method is ascertained by detecting Cr(III) in spiked tap water and instant tea samples.