Applications Research Of Copper Nanoclusters And Graphene Quantum Dots As Fluorescent Probe

The research on fluorescent probes very active in analytical chemistry. In recent years, the research on various fluorescent probes, such as organic compounds,conjugated polymers, semiconductor quantum dots, have been rapidly developed.However, these fluorescent probes still suffers from some deficienciers, such as,complex chemical synthesis of organic compounds and conjugated polymers, high environmental toxicity of semiconductor quantum dots. Thus, there is a need to find a sensitive, specific, simple and low toxicity fluorescent probe. Based on that, we choose copper nanoclusters(Cu NCs) and graphene quantum dots as fluorescent probe to carry out research. The first is copper nanoclusters, it has the energy band gap between molecular and general nanoparticles, similar molecular fluorescence properties and the simple synthetic method, thus made it has good potential as a fluorescent probes. The second is doped graphene quantum dots, it is a kind of carbon nanomaterials which has the size less than 100 nm. Doping graphene quantum dots with heteroatoms can effectively improve luminescence quantum yield and solubility, tune the optical properties, thus increased the potential for the application as a fluorescent probe.Considering the good characters of both materials the above mentioned, we carry out our work to research the synthesis and applications of them as fluorescent probes. The major contents are summarized as follows.1. Copper sulfate was used as copper source, ascorbic acid as the reducing agent to prepare copper nanoclsters in facile conditions. The Cu NCs are characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy, luminescence,transmission electron microscopy and scanning electron microscopy. The Cu NCs show luminescence properties having excitation and emission maxima at 360 nm and430 nm, respectively, with a quantum yield of about 5.6%. The Cu NCs also exhibit strong photostability and very stable even in 1M NaCl. The Au3+ was Cu NCs reduced as Au NPs, thus the fluorescence(FL) of the Cu NCs is quenched, while, in the presence of biothiols, the biothiols have more stronger interaction with Au3+, thus the formation of Au NPs was inhibited, causing the fluorescence rescovery. Based on that, Cu NCs combine with Au3+ was used to detect biothiols. The proposed system could respond down to 30 nM with a linear range from 0.1 μM to 10 μM. Moreover, we demonstrate the feasibility of using Cu NCs for the detection of biothiols in blood samples,suggesting the feasibility of this method.2. In this work, citric acid and ethylenediamine was used as the carbon source and nitrogen source, a simple one-pot hydrothermal method was used to prepare N-doped graphene quantum dots(N-GQDs), further, the N-GQDs was used to quantatively detect picric acid(PA). The as-synthesized N-GQDs show luminescence properties having excitation and emission maxima at 360 nm and 445 nm, respectively, with a high quantum yield of 94%,and the N-GQDs were characterized by UV-vis spectroscopy,Fourier transform infrared spectroscopy and luminescence. Owing to electron-rich property of N-GQDs while the electron-deficient property of PA, the sensing mechanism to be hypothesized is the electrostatic interaction between PA and carboxyl and hydroxyl groups of the N-GQDs along with the decrease fluorescence signal. Also,the experiment were performed to investigate the effect of the concentration of N-GQDs,reaction time, pH, and ionic strength. Under optical conditions, the linear range from0.5 to 200 μM with the detection limit at 0.1 μM. Herein, a sensing PA system with highly sensitivity and selectivity is designed using stable and fluorescent N-GQDs.Moreover, we demonstrate the feasibility of using N-GQDs for determination of PA in environmental water smples.3. To obtain N, P co-doped graphene quantum dots(N, P-GQDs), a simple,one-step hydrothermal method for preparation of water soluble and fluorescent N,P-GQDs. For this, citric acid as the carbon source, ethylenediamine and phosphoric acid as the nitrogen source and phosphorus source, respectively. The N, P-GQDs were characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy and luminescence. The fluorescence of the N, P-GQDs is quenched by Hg2+ through an electron transfer mechanism, which was proved by the change of hydrate particle size and the Zeta potential of the system. Additionally, this optimization resulted in surprisingly high efficiency of selective Hg2+ sensing and other coexistence ions have no obvious effects on the sensing of Hg2+. Under optical conditions, the linear range from 0.01 μM to 20 μM with the detection limit at 3 nM. On the basis, we developed a feasible method for the detection of Hg2+ in real samples.