| Carbon dots have been widely used in various research fields as fluorescent probes, bioimaging, catalysis and drug delivery, due to their unique luminescence, stable chemical properties, good water-solubility, low toxicity and outstanding biocompatibility. However, the studies about the ratio of fluorescent probes and chemiluminescence based on carbon dots is less. This thesis has carried out the following work for these problems:First of all, nitrogen-doped carbon dots with QYs of 10 % were synthesized in one step by using pyrolyzing ethanolamine as the source of carbon and nitrogen. Series of characterization experiments have indicated that the obtained NCDs are near-spherical and uniform in size( ~ 6.0 nm in diameter) and the proportion of C, N, O was 67.25 %, 11.93 and 20.82 %, respectively. The absorption of NCDs is rather strong in ultraviolet region than in visible region and excitation-dependent PL behavior. With doped with N, a high electronegativity element, in carbon dots, luminescence properties and quantum yield were improved by two ways: elevating the chance of electron-hole pair recombinated by enhancing the electron density of carbon rings and reducing non-radiative recombination centers by amino and amide modified and passivated.Carbon dots were designed into two kinds of novel analytical methods. In section one, a ratiometric fluorescence probe has been developed by simply mixing the blue-emisssion NCDs with yellow-emission calcein. The ratiometric fluorescence probe exhibits dual emissions at 428 nm and 515 nm under a single excitation wavelength, in which the former is an intern reference peak and the latter is a recognition peak. Due to the chelating ability of calcein on the surface of NCDs to europium ion(Eu3+), the fluorescence of the calcein could be selectively quenched in the presence of Eu3+ while the fluorescence of the NCDs remained constant. Eu3+ ions exhibit higher affinity to the oxygen-donor atoms originated from phosphates than that from carboxylate groups, therefore, “turn-on” flurescence can be observed with the addition of ATP due to the strong coordination between ATP and Eu3+. Based on this “on-off-on” form, we built a ratiometric strategy for detecting ATP with high selectivity, fast response and abroad linear ranges of 5.0×10-8 mol L-1 ~2.0×10-6 mol L-1, as well as low detection limits of 2.0×10-8 mol L-1. Furthermore, the recovery result for ATP in real samples by this ratiometric strategy was satisfying. Compared with calcein-europium probe without carbon dots, this ratio-fluorescent probe could reduce interference and improve accuracy effectively.In section two, the enhancement effects of NCDs on the ultra-weak CL reaction between acid-KMnO4 and sodium sulfite was explored and a novel CL system for direct detection of sodium sulfite was established. Sodium sulfite was sensitively detected with a detection limit of 4.7×10-6 mol L-1 and had a wide detection range of 1.6×10-5 mol L-1~ 4.0×10-4 mol L-1. This method has been successfully applied to the determination of sulfite in red dates, raisins, oats and sugar, with recoveries in the range of 86.2-108 % and the relative standard deviation below 6.0 %. On the basis of UV-visible absorption spectral, fluorescence spectral and CL spectral, a possible CL enhancement mechanism of NDCs on the acid-KMnO4 and sodium sulfite was proposed. It was suggested that SO2* and the excited oxidized NCDs might be the emitters in this system, and NCDs act as catalysts and emitting species in acid NCDs- KMnO4- sodium sulfite system. |
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