Preparation, Characterization And Optical Spectroscopy Properties Of Composite Based On Cdse Quantum Dots

With the development of science and technology, composite materials havebecome an important trend. Immobilization of rare earth ions, nano-crystals andorganic fluorescent dye by sol-gel technique to prepare new composite opticalmaterials with superior performance to meet some special requirements hasbecome a hot research topic. In this thesis, we chose a green chemical synthesisprocedure, using non-toxic, easy-to-handle CdO and Se powders as the precursorof Cd and Se to synthesis a series of different-sized organic-soluble CdSequantum dots (QDs) in oleic acid, dodecylphosphonic acid andtrinoctylphosphine system at280℃. We monitored the kinetics of CdSe growth,which present narrow size distribution and good monodispersity, by UV-visibleabsorption spectroscopy. Red shift of the emission peak in the growth process ofCdSe QDs, corresponding to the change of photoluminescence (PL) color fromlight green to dark green, were monitored by emission spectroscopy. PL quantumyield is calculated to be about10-22%. Then, organic-soluble CdSe QDs weretransferred into water-soluble CdSe QDs. The replacement of mecapto-group onCdSe QD surface was characterized by infrared (IR) spectroscopy. Water-solubleCdSe QDs, which also present good monodisperse, were characterized byUV-visible absorption and emission spectra, and their PL quantum yield wasfound to decrease to5%. Using the water-soluble CdSe QDs, we prepareddifferent concentrations of Eu3+/CdSe QDs and Rhodamine B/CdSe QDscomposite solution. Their optical spectroscopy properties were characterized byUV-visible absorption and emission spectra. The results showed that energytransfer exist in the Eu3+/CdSe QDs composite solution and not obvious energytransfer exist in the Rhodamine B/CdSe QDs composite solution. While, electrontransfer exist in the Rhodamine B/CdSe QDs composite solution. With theintroducing of CdSe QDs, PL effect of Rhodamine B/CdSe QDs compositesolution becomes weak. Finally, by using tetraethylorthosilicate and3-glycidoxypropyltrimethoxysilane as precursor silica source, differentconcentrations of Eu3+/CdSe QDs and Rhodamine B/CdSe QDs co-doped composite SiO2gel glasses were prepared using sol-gel technique, which werecharacterized by X-ray diffraction and IR spectra. The results showed thatmajority of composite SiO2gel glass were amorphous. Their optical spectroscopyproperties were investigated using UV-visible absorption spectra, excitation andemission spectra. The results showed partially quench of the luminescence ofcomposite SiO2gel glass matrix. There is an energy transfer among the dopedEu3+, CdSe QDs and SiO2matrix in Eu3+/CdSe QDs codoped composite SiO2gelglass. The introducing of CdSe QDs weakened the luminescence of Rhodamine Band SiO2gel glass matrix.