| Fluorescence labeling technique has become an essential analytical technique in the fields of chemistry, biology and medicine owing to its good selectivity, high sensitivity and easy operation. Quantitative and qualitative analysis can be realized by measuring the alternation of fluorescence signal which is resulted in the reaction between fluorescent molecules and the target object. Nanomaterials with excellent photophysical and photochemical properties have attracted many researchers and become the next generation of fluorescent material. In this article, we summarize the recent progress in the applications of fluorescent probes and highlight the preparation,properties and analytical applications of the metal nanoclusters and carbon dots. The thesis is divided into three main chapters:Chapter 1: Poly(vinyl pyrrolidone) capped copper nanoclusters(PVP-Cu NCs)were fabricated by chemical reduction of Cu(II) ions using formaldehyde as the reductant and poly(vinyl pyrrolidone) as the protecting agent. The resulting PVP-Cu NCs were characterized by TEM, FT-IR, UV-vis, XPS and fluorescence spectroscopy.The PVP-Cu NCs display a luminescence quantum yield of about 12.6%, and the emission peaks shift from 398 to 457 nm on increasing the excitation wavelength from310 to 390 nm. The PVP-Cu NCs possess a storage stability of at least 2 months and are stable in the presence of high concentrations of salt. Their fluorescence is strongly quenched by hypochlorite, while other common cations, anions and hydrogen peroxide have minor(or no) effects on fluorescence. On this basis, a fluorometric hypochlorite assay was developed that has a 0.1 μM detection limit and a linear range that extendsfrom 1 to 30 μM. This method was successfully used to the determination of hypochlorite in local tap water samples, and the results agreed well with those obtained by a colorimetric method.Chapter 2: Nitrogen doped carbon dots(N-CDs) were facilely obtained by one-step hydrothermal treatment of ascorbic acid as the carbon source and ethylenediamine as the surface passivation reagent. The luminescent N-CDs exhibit an excitation-dependent emission with a high quantum yield of 11.2%, which is 4 times about that of the undoped carbon dots. It is found that the fluorescence of N-CDs is significantly quenched by Au(III) while other common anions and cations have minor or no effects,thus a highly sensitivity and selectivity method was developed for the determination of Au(III) in the linear range of 0-30 μM with a detection limit of 17 nM. The quenching mechanism is attributed to the formation of gold nanoparticles(Au NPs). On this basis,the as-prepared N-CDs is potentially applicable to the determination of trace Au(III) in real samples.Chapters 3: In the present work, we report the synthesis of highly luminescent boron and nitrogen co-doped carbon dots(B,N-CDs) by a facile hydrothermal synthesis route using boric acid, ethylenediamine and ascorbic acid as the precursors. The resulting B,N-CDs display a storage stability of about 1 month and keep stable in the presence of high concentrations of salt, which can be used as photoluminescent probes for selective and sensitive determination of picric acid(PA) in aqueous solution with a detection limit of 17 nm in the linear range of 0-50 μM. It is worth mentioning that the reaction completed in only 1 minute. The sensing mechanism is proposed as resonance energy transferring from B,N-CDs to PA which resulted in fluorescence quenching. The proposed method provides a promising candidate for the detection of picric acid in real samples. |
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