Upconversion photoluminescent Yb(Ⅲ)/Er(Ⅲ) doped nanoparticles interact with AuNPs for detection of Cr (Ⅲ) and sodium tripolyphosphate based on FRET

In this study, we designed a dual functional nanosensor for detecting Cr (Ⅲ) and sodium tripolyphosphate (STPP) based on fluorescence resonance energy transfer (FRET) mechanism between amine functionalized upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs), where UCNPs serve as energy donor and aggregated AuNPs as energy acceptor. UCNPs have red emission at 654 nm under 980 nm laser excitation and monodispersed AuNPs show strong absorbance around 520 nm. Monodispersed AuNPs form aggregate easily in the presence of Cr (Ⅲ), which leads to the red-shift of the absorption of AuNPs and quenches the red emission of UCNPs. In the presence of STPP, the formation of Cr (Ⅲ)-STPP complex weakens the aggregation extent of AuNPs and the red emission of UCNPs increases. Therefore, the content of Cr (Ⅲ) and STPP could be detected in wide range according to the linear variety of fluorescence intensities of UCNPs at 654 nm with the detection limits of 0.44 μM and 0.54 μM for detecting Cr (Ⅲ) and STPP, respectively. In addition, due to the high selectivity and accuracy for the detection of STPP, this nanosensor can be utilized to determine STPP in green tea drink and drinking water.