Thesis (M.Sc.)--Chulalongkorn University, 2012

In this research, a novel analytical method based on electrochemiluminescence (ECL) of CdTe quantum dots (QDs) using carbon nanotube (CNT)-modified screen-printed carbon electrodes (SPCNTEs) was developed. It was found that the SPCNTEs could greatly enhance the ECL intensity of CdTe QDs dispersed in aqueous solution. Thus, SPCNTEs would have a great merit to expand the application of QD ECL. The thioglycolic acid (TGA)-capped CdTe QDs used in ECL procedure based on the SPCNTEs were synthesized and characterized by UV–visible spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and infrared spectroscopy. From the charaterizations, the average size of TGA-capped CdTe QDs was approximately 2.53 nm, which considered close to the diameter of 2.47 nm resulting from the calculations using UV-visible absorption spectra of the QDs. Moreover, the concentration of synthezied TGA-CdTe QDs was found to be 7.39 x 10-3 M. Influences of some factors on the ECL intensity were investigated to determine homocysteine (Hcy) based on the quenching effect of CdTe QDs ECL. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of Hcy in the range of 5 to 35 μM with the limit of detection of 0.011 μM. This proposed method was successfully applied to determine Hcy in human urine and artificial urine samples.