Determination of copper based on fluorescence switch of CdTe quantum dots-dithizone

The surface of CdTe quantum dots was coated by dithizone. The fluorescence quenching of CdTe occurred due to fluorescence resonance energy transfer between dithizone and CdTe quantum dots. The fluorescence resonance energy transfer was prohibited due to the formation of bidentate chelate after copper ion was added,then the fluorescence intensity of CdTe quantum dot was recovered. Based on this, a new determination method of trace copper by fluorescent switch was established. Under the optimal conditions, copper ions of different concentration were added into the solution which was composed of 0.5 mL of dithizone @CdTe quantum dots (Dit@CdTe),1.5 mL of Tris-HCl buffer solution (pH 7.5). After standing for 10 min, the fluorescence intensity of solution was measured at 431 nm/591 nm (excitation wavelength/emission wavelength). The enhanced fluorescence intensity showed good linear relationship to Cu²⁺ concentration in the range of 0.01-10.0 μmol/L with correlation coefficient of 0.990 3. The detection limit was 0.004 μmol/L.The proposed method was applied to the determination of copper in actual water sample. The relative standard deviation was less than 6.8%, and the recovery was 97%-105%. The determination results were consistent with those obtained by inductively coupled plasma mass spectrometry (ICP-MS).