Fluorescence sensing of nitric oxide in aqueous solution by triethanolamine-modified CdSe quantum dots

The water-soluble luminescent CdSe quantum dots were prepared by ligand exchange with triethanolamine (TEA). Oxygen can reversibly enhance the fluorescence of the synthesized quantum dots (TEA-CdSe-QDs) in aqueous solution. Nitric oxide radical (NO) can react easily with dissolved oxygen in water and was found to have a significant quenching effect on the fluorescence of the TEA-CdSe-QDs. The fluorescence responses were concentration-dependent and can be well described by the typical Stern-Volmer equation. A good linear relationship (R(2 )= 0.9963) was observed over the range 5.92 x 10(-7 )to 1.85 x 10(-5) mol/L nitric oxide. Above this concentration was a second linear region ranging from 2.12 x 10(-5) to 1.12 x 10(-4 )mol/L NO with a gentler slope. The detection limit, calculated following the 3sigma IUPAC criteria, was 3.02 x 10(-7 )mol/L. The interference effect of some common interferents such as nitrite (NO2 (-)), nitrate (NO(3) (-)), glucose and l-ascorbic acid on the detection of NO was negligible for the proposed system, demonstrating the potential utility of this probe for the detection of NO in biological systems. The possible mechanism was also discussed.