Fluorescent Analytical Methods For Small Molecular Pollutants

Analytical methods based on fluorimetry have high sensitivity, good selectivity, and low equipment cost, so fluorescence-based methods have attracted much attention from the field of chemical sensor, medical diagnosis and bioimaging. In addition, the fluorescent probes can react with the analyte and produce obvious color changes, which can be readily employed for visual detection. By taking the advantages of fluorescence-based methods, we have designed several fluorescent probes for the sensitive detection of small molecular pollutant gases such as sulfur dioxide, hypochlorous acid, hydrogen sulfide, and etc. The contents of research work can be summarized as the following.1. We have fabricated an "off-on" ratiometric fluorescent probe by functionalizing CdTe quantum dots with amino groups and coumarin-3-carboxylic acid. The ratiometric probe displays dual emission bands at 425 and 628 nm under single-wavelength excitation at 340 nm. The fluorescent probe can rapidly responses to SO₂, with fluorescence intensity at 628 nm enhanced and at 628 nm remained. This probe has a high sensitivity for SO₂, and a good selectivity over other relevant gaseous. The method affords a visual detection limit of 6 ppb for gaseous SO₂.2. We have synthesized a new near-infrared fluorescent probe for hypochlorous acid by an electrophilic substitution reaction between diethanolamine and chlorine cyanine. The probe can be applied in detection of HOC1 in living cells. The probe shows good solubility in water and has potential for hypochlororous acid in biosystem. This fluorescent probe can react with hypochlorous acid immediately by electrophilic addition reaction and oxidation reaction and the fluorescence intensity would be quenched at the same time. The probe can act as a selective and sensitive indicator for HOC1 and the limit of detection for HOC1 is estimated to be 22 nM. What’s more, this probe shows a good application prospect in visualizing HOC1 molecules in living cells.3. We have fabricated a fluorescent ligand based on 4-chloro-7-nitro-1,2,3-benz-oxadiazole （NBD-C1）. The ligand can react with copper to form a complex which shows low fluorescent intensity. The metal copper center can recognize sulfide and release the fluorephore, hence the fluorescence intensity enhanced. In aqueous solution, the method can realize a high sensitivety and selectively for S^2- with detection limit of micromolar range. In addition, the method also has a good recovery test for S^2- in tap water.4. We have firstly fabricated a new ligand for copper（II） by the reaction between 11-mercaptoundecanoic acid and a nitrogen-containing organic complex. A new organic-inorganic hybrid fluorescent probe for detection of copper ions was then obtained by modifying this ligand and dithiothreitol on the surface of red-emitting CdSe/ZnS quantum dots. In the absence of copper ions, the probe shows red fluorescence. Whereas in the prescence of copper ions, the hybrid probe react with copper and its fluorescence will gradually decrease as a result of fluorescence resonance energy transfer between the hybrid fluorescent probe and Cu²⁺. The probe can be used to detection of Cu²⁺ quickly and high selectively.