Quantum Dots Involved Lucigenin Chemiluminescence And Electrogenerated Chemiluminescence

Semiconductor quantum dots(QDs) are novel chemiluminescence(CL) and electrogenerated chemiluminescence(ECL) systems, which have been widely studied in recent years. Compared with the traditional luminescent systems, QDs exhibit many unique electronic and optical properties. On the other hand, QDs can also act as reductant, catalyst, energy acceptor, and microscale reaction platform to induce liquid CL. Acridine compound is one of traditional CL and ECL systems and lucigenin is most famous. However, the reported lucigenin CL and ECL are mainly operated under strong basic condition and often need the presence of coreactant, which limit the application of lucigenin CL and ECL. In this thesis, quantum dots involved lucigenin CL and ECL are investigated, and biosensing applications of the novel luminescent systems are also discussed. The main contents of this paper are as follows:1.Electrogenerated chemiluminescenceof quantum dots, including CdS, CdSe,CdTe, and CdSe@ZnS QDs, was comparatively studied in neutral lucigenin solution without coreactants. Cathodic ECL signals were obtained at-1.2 V at different QDs modified gold electrodes(QDs/GEs), the strongest ECL emission obtained at the CdSe@ZnS modified GE, which is about 7-times larger than other QDs modified GEs.The ECL spectrum and the electrochemical results revealed that the luminophor of the cathodic ECL is the excited state of QDs but not lucigenin, which reveals that lucigenin can act as coreactant to produce cathodic ECL with QDs. Several impact factors, such asthe supporting electrolytes, the amount of QDs, and the pH were investigated. Under the optimal condition, catechol exhibited apparent inhibiting effect on the cathodic ECL signal, based on which a new ECL sensor was developed and applied in the sensitive detection of catechol. The inhibited ECL intensity varied linearly with catechol concentration in the range of 5~1000 nM with a detection limit of 2 nM(S/N=3). The ECL sensor exhibited satisfied stability, repeatability, and selectivity.2.Strong anodic ECL was obtained in neutral lucigenin solution at a CdSe quantum dots modified glassy carbon electrode. Electrochemical results suggestedthat CdSe quantum dots can catalyze the oxidation of bromide and lucigenin, which can generate the anodic ECL. The ECL spectra and the fluorescence revealed that ECL resonance energy transfer(ECL-RET) can occur between CdSe andlucigenin quantum dots. Therefore, the oxidation product of bromide can promote ECL-RET and increase the anodic ECL signal significantly. Cytochrome C exhibited apparent inhibiting effect on the anodic ECL emission, based on which a sensitive ECL sensor for the detection of Cytochrome C was established.3.In alkaline medium, CdS quantum dots can strongly enhance chemiluminescence of lucigenin-H2 O system By combining the advantages of chemiluminescence and flow injection analysis,a new method for the determination of ascorbic acid has been established, and the possible reaction mechanism was discussed.The results showed that in the optimal conditions, CL intensity showed a good linear relationship with ascorbic acid concentrations in the range of0.1~5000nmol·L-1. The linear equation was determined as I/?A = 415.28 + 54.49C(×10-6 mol·L-1) with the correlation coefficient(R2)of 0.993. The detection limit was determined as 0.37×pmol·L-1(S/N = 3). The relative standard deviation for 11 times determination of 100nmol·L-1 ascorbic acid was 2.6%. The proposed CL system exhibited several advantageous, such as simple instrument, fast response, high sensitivity, and low detection limits, which can be used in the detection of ascorbic acid in fruit.