Mechanism Research Of Luminol Chemiluminescence Enhancing By ZnO Nanoparticles And Their Application

Chemiluminescence(CL) detection has many advantages, such as high sensitivity,relatively inexpensive instrument, wide calibration range and suitable for automation.Nanoparticles have a series of excellent properties. It has been reported nanoparticles have been applied in electronics, optics, energy and biological medicine. In recent years,nanoparticles as a catalyst used in the chemical luminescence, making the research of chemical luminescence is no longer confined to the level of molecules and ions, and to get rapid development. In this thesis, the review involves the concepts and characteristics of CL, photocatalytic properties of nanoparticles and the application of nanoparticles in the CL.In this thesis, Zn O nanoparticles(Zn ONPs) as a catalyst in luminol–H2O2 CL system were explored. And luminol–H2O2–Zn ONPs was applied for the analysis of H2O2 in rainwater. Selfdecomposition of H2O2 could cause signal of luminol–H2O2 CL unstable, and maked reproducibility poor. H2O2 is a strong oxidant, which can react with luminol, producing strong CL signals and high background values. In this study, it was found that in the presence of Zn ONPs, ethylenediamine tetraacetic acid disodium(EDTA) and luminol could generate strong CL without other oxidizing agent.EDTA is a kind of chelating agent and used as electron donor commonly. Itself has no oxidation, good stability and solubility in water. A new CL system of luminol–EDTA–Zn ONPs was established. In this paper, the effect of different particle sizes of Zn ONPs on CL of luminol–EDTA was studied. Mechanism of the luminol–EDTA–Zn ONPs CL systems was investigated. Moreover, a method for determination of caffeic acid and metal ion was developed. The main research results are as follows:① Mechanism of luminol–H2O2–Zn ONPs CL systems was investigated. Based on the Zn ONPs amplifying a weak CL of luminol–H2O2 system, a simple and sensitive CL method was been developed for the determination of H2O2. Experimental parameters affecting CL including p H and concentration of Zn ONPs, luminol and H2O2 were optimized. Under optimal conditions, the logarithm of CL peak area was linear over the logarithm of concentration of H2O2 ranging from 0.06 to 20 mmol/L with the limit of detection of 0.016 m mol/L(3σ). The method had been successfully applied for the analysis of H2O2 in rainwater, giving recovery in the range of 95%~102% and RSD(n=11) of 2.41%.②In this study, it was found that in the presence of Zn ONPs, EDTA and luminol can produce strong CL without other oxidizing agent. Hereby, a new CL system of luminol–EDTA–Zn ONPs was established. Different particle sizes and dispersibility of Zn ONPs colloidal solutions can enhance the CL differently. The results indicated that Zn ONPs with smaller sizes and better dispersibility could initiate stronger CL emission.The results of UV-visible absorption and the CL spectra showed that the CL luminophor was 3-aminophthalate. The experimental results indicated that dissolved oxygen was involved in the CL process. Zn ONPs is a semiconductor nanomaterial, which could be activated by visible light. Electron transferred from the valence band to the conduction band. Excess electron accumulating on the conduction band of Zn ONPs reacted with dissolved oxygen to produce superoxide anion radical(O2·-). The O2·-reacted with luminol, accompanying a light emission. EDTA is a chelating agent and frequently used as a common electron donor. Surface complex between Zn ONPs and EDTA were formed. EDTA served as electron donor to the conduction band of Zn ONPs, Which was assumed to accelerate the electron transfer process and to facilitate radical generation.The new CL system had the advantages of low background, good stability and economy.③ It had been found that caffeic acid strongly inhibits the CL of luminol–EDTA–Zn ONPs. Under the optimized conditions, the relative CL intensity was linear over the logarithm of concentration of caffeic acid ranging from 1.0×10-7 to1.0×10-5mol/L with the limit of detection of 3.78×10-8mol/L(3σ). The new method had been successfully applied for the analysis of caffeic acid tablets, giving values recovery in the range of 97% ~ 101% and RSD(n=11) of 3.53%. EDTA is a chelating agent,which can be bound to metal ions. When EDTA chelated with metal ions, the amount of EDTA in the CL system was reduced, thus CL intensity weakened. According to the relationship of relative CL intensity and concentration of metal ions, the new CL system had a wide application for the determination of metal ions.