In this study, a novel Au nanocluster (NC)-based fluorescent sensor has been designed for near-infrared (NIR) and turn-on sensing of glutathione (GSH) in both living cells and human blood samples. The large Stokes-shifted (140 nm) fluorescent Au NCs with NIR emission and long-wavelength excitation have been rapidly synthesized for 2 h by means of a microwave-assisted method in aqueous solution. The addition of Hg(II) leads to an almost complete emission quenching (98%) of Au NCs because of the interaction of Hg(II) and Au(I) on the surface of Au NCs. After introducing GSH to the Au NC-Hg(II) system, a more than 20 times fluorescent enhancement is obtained because of the preferable affinity of GSH with Hg(II). Under optimum conditions, the fluorescence recovery is linearly proportional to the concentration of GSH between 0.04 and 16.0 μM and the detection limit is as low as 7.0 nM. This Au NC-based sensor with high sensitivity and low spectral interference has been proven to facilitate biosensing applications.

We have synthesized the near-infrared watersoluble conjugated polymer poly[2,5-di(propyloxysulfonate)-1,4-phenylene-ethynylene-9,10-anthrylene (referred to as PPEASO3). Its fluorescence (at wavelengths between 650 and 800 nm following photoexcitation at 550 nm) is efficiently quenched by Cu(II) ions, while other physiologically relevant metal ions do not cause significant quenching at the same concentrations. Under optimum conditions, fluorescence intensity is inversely proportional to the concentration of Cu (II). The calibration curve displays two linear regions over the range of 0-3.2×10 −7 mol L −1 and 3.2×10 −7 mol L −1 to 1.0× 10 −4 mol L −1 of Cu(II), respectively. The long-wavelength excitation and emission can substantially reduce interferences by the autofluorescence and light scattering of biological matter under UV excitation. The method was successfully applied to the determination of Cu(II) in synthetic and tea samples.

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Stable water-soluble CdHgTe nanorods with an emission wavelength at 722 nm, obtained by doping Hg 2+ into CdTe nanorods, has been used as a near-infrared region (NIR) probe to investigate their interaction with copper(II) ions. A new fluorimetric method for the determination of copper(II) ions has been developed based on the quenching effect of copper(II) ions on the emission of CdHgTe nanorods. The mechanism studies show that an effective electron transfer from nanorods to the copper(II) ions occurred based on the coordination reaction between copper(II) ions and the carboxyl groups on the nanorods surface, which could be responsible for the emission quenching of CdHgTe nanorods. Under optimum conditions, the linear range of the calibration curve for the determination of Cu 2＋ is from 8.0×10-9 to 1.0×10 -6 mol/L and the detection limit is 2.0×10 -9 mol/L. Owing to low background interference of NIR measurement, the proposed method displays relative high sensitivity and selectivity. Especially, some physiologically important cations almost do not interfere with the determination of Cu 2＋ . The proposed method was also applied to the determination of trace Cu 2＋ in real aqueous samples with satisfactory results.

A novel peroxyoxalate chemiluminescence system has been designed for the determination of Triton X-100 (TX-100), in which a hydrophobic fluorescent conjugated polymer, poly[2,5-bisnonyloxy-1,4-phenyleneethynylene-9,10-anthrylene] (PPEA) was employed as a fluorophor. A strong enhanced intensity of chemiluminescence (CL) was observed in the presence of TX-100, due to the improved emission efficiency of PPEA in the presence of TX-100. Under optimum conditions, the detection range of Triton X-100 is between 1.0×10 -7 and 1.0× 10 -4 mol•L -1 , with a detection limit at 6.0×10 -8 mol•L -1 . The relative standard deviation is 2.4% (n＝6) for 1.0×10 -6 mol•L -1 Triton X-100. This method provides satisfying results in the detection of TX-100 in nature water and biological samples with high sensitivity and wide linear range.