Polymeric optodes based on upconverting nanorods for fluorescence measurements of Pb2+ in complex samples

We reported here a lead ion selective optode incorporating NaYF4: Er,Yb upconverting nanorods, chromoionophore ETH 5418, and lead ionophore together in hydrophobic polymer matrixes. The absorption spectra of protonated and unprotonated ETH 5418 overlap the two emission peaks of the upconverting material, respectively, which allows the fluorescent ion sensing based on the inner filter effect. The proposed optodes exhibited highly selective and reproducible sensing property for measuring lead ions in the range of 10−6-10−2 M at pH 5. Because the excitation source is 980 nm and the emission wavelength lies in the near-infrared region, the sensors have been successfully used in complex samples for example plasma with minimized background absorption and sample autofluorescence. The lead levels in sheep plasma and artificial industry wastewater samples obtained by the optode were comparable with the known addition amounts of Pb(NO3)2, providing a new method for testing Pb2+ in the industry wastewater.