Determination Of Acridine Orange By Reversible Regulation Of Quantum Dot - DNA - Acridine Orange Fluorescence

In this thesis, we have established a new method for the detection of acridine orange(AO), based on the reversible fluorescence control among the quantum dots (QDs)-DNA-acridine orange(AO) interaction. The main results are described as follows:1. Single nuclear mercaptoethylamine copped ZnSe QDs were synthesized. Their particle sizes, morphology and fluorescence quantum yield were characterized by transmission electron microscope(TEM)and fluorescence spectrometry, UV-Vis absorption spectrometry. The influence factors on the analytical performance was investigated, such as reaction time, reaction temperature and the initial ratio of Zn and Se, the concentration of CA-ZnSe QDs, the concentration of herring sperm DNA(hs-DNA), different acidity andcoexistent matteron the determination of systems were investigated.As a result, It was confirmed that we successfully synthesized the CA-ZnSe QDs with good monodispersity and photostability, the partical sizeand quantum yields of whichare 3-4nm and 65.8%,respectively.2. Through the choices and attempts of different stabilizers, different DNA quenching agents, it was preliminary confirmed that under the following conditions:using QDs(CA-ZnSe QDs),fluorescence quencher(herring sperm DNA, hs-DNA) and acridine orange (AO) as the substance to be detected, we can gain the expectant experiment outcome:CA-ZnSe QDs were quenched by herring sperm DNA;after the addition of acridine orange into the hs-DNA/CA-ZnSe QDs composite system,the fluorescence intensity of CA-ZnSe QDs was recovered. Through the optimization of experimental conditions, it was identified that the best conditions was:the concentrations of CA-ZnSe QDs and hs-DNA were 2.5×10-4mol/L and 2.25×10-3mol/L,respectively.The reaction time in the process of fluorescence quenching/recovery of QDs were 3min and 15min,respectively, and the acidity of the whole system is 6.0from beginning to end.3. We explored and researched the mechanisms during the process of fluorescence quenching/restoration of CA-ZnSe QDs, and its quenching type is also investigated vis fluorescence spectrometry and UV-Vis absorption spectrometry. Experimental results show that QDs were quenched by herring sperm DNA because of electronstatic interaction;the fluorescence intensity of CA-ZnSe QDs was recovered after the addition of acridine orange, due to the strong insertion of acridine orange into the double-helical structure of hs-DNA and form a more stable hs-DNA/AO compounds.4.Through the optimization of experimental conditions, including the concentration of CA-ZnSe QDs, the concentration of hs-DNA and the reaction time in the process of fluorescence quenching/restoration of CA-ZnSe QDs; we can get the conclusion:under the optimum conditions, the CA-ZnSe QDs fluorescence probe offers good sensitivity and selectivity for detecting AO. The probe offers good linear relationship between 75 and 210 μmol/L for the detection of AO(the correlation coefficient was 0.9920), with limit of detection is 15μmol/L. The method was successfully employed for the analysis of AO content in tap water and simulated dyeing wastewater. The results show that this method is simple, rapid, selective, high sensitive for the detection of AO.