Synthesis, Characterization And Application Of Ⅱ-Ⅵ Group Luminescent Nanoparticles

Luminescent Semiconductor nanopaticles (NPs), commonly known assemiconductor quantum dots (QDs), have attracted a lot of interests during the lasttwo decades. As their sizes are smaller than the bulk exciton Bohr radius, theyexhibit many unique optical, electrical and chemical properties, giving rise tonumerous potential applications in physics, chemistry, biology and medicine. There are now two major routes in the synthesis of Group II-VI NPs bychemical methods. The first is the use of TOPO-TOP as capping agents andCd(CH3)2 as precursor as used by Bawendi and his colleagues in 1993. Recently,Peng et al. have developed a cheaper, easier and safer procedure by using CdOinstead of Cd(CH3)2. The second route is an aqueous path in the presence ofdifferent thiols as stabilizing agents, which will be more attractive for industrialproduction of these nanoparticles as the process is environmental friendly. In Chapter 1, nano technology, nano materials, nano particles are introduced.Especially, the synthesizing methods of QDs are reviewed. In Chapter 2, CdSe nanoparticles capped with CdS were synthesized inaqueous solution using 2-mercaptoethanol as stabilizer. The CdS capping with ahigher bandgap than that of the core crystallite has successfully eliminated the 胡 海 吉林大学硕士学位论文 2004中英文摘要 ·IV·surface traps. The X-ray powder diffraction, transmission electron microscopy andX-ray photoelectron spectroscopy were used to analyze the compositenanocrystals and determine their average size, size distribution, shape, internalstructure and elemental composition. However, these QDs have low quantumyield, poor reproducibility. In Chapter 3, CdTe NPs were prepared in aqueous solution usingmercaptopropinic acid (MPA) as the stabilizer. UV-Vis spectrophotometric &photoluminescent measurements have been used to obtain information on sizedistribution of CdTe NPs. The effects of pH, anion group and the opticalproperties of the film made of the colloidal NPs coating on glass are alsomentioned. In Chapter 4, CdTe NPs and formaldehyde dehydrogenase were immobilizedin electropolymerized polyaniline or polyaniline/poly(o-phenylenediamine)bilayer films. The photocurrent responses of enzyme-semiconductor nanoparticlesentrapped in electropolymerized films were measured. The hybridsemiconductor/enzyme coupled system is able to perform selectively catalyticoxidation of formaldehyde, and the preliminary results indicate that nanosizedCdTe/enzyme immobilized in electropolymerized films is an effective photoactivematerial to replace the NAD+/NADH role as charge transfer in the enzymaticreaction.