Preparation And Application Of Water Soluble CdSe Quantum Dots And CdSe Nanoparticles

Due to its unique fluorescence properties and significant size effect, CdSenano-materials have been extensively studied in physics, chemistry and biology fields.CdSe quantum dots （QDs） has been appreciated by lots of researchers for its excellentqualities. It is always a hot spot for researchers that how to get CdSe QDs with excellentfluorescence through the physical and chemical methods. CdSe possess1.7eV of bandgap and very excellent spectral response range. It is considered as an idealphotosensitive material and has potential applications in environmental remediation andenergy conversion, the most critical issue is how to improve the light utilizationefficiency. This thesis study the fluorescence properties and photocatalytic degradationactivity of CdSe QDs. Surfactant and the treatment of light oxidation were used toimprove the fluorescence properties of the CdSe QDs. In addition, CdSenanomicrospheres and CdSe/sulfhydryl cellulose （SC） nanocomposite material wereprepared and the ability to photocatalytic degradation dyes were studied. The mainimportant work of this paper as follows:1. CdSe quantum dots was prepared in aqueous phase modified by non-toxic,environment friendly and good biocompatibility sodium carboxymethyl cellulose（CMC）. The CdSe QDs is nearly monodispersed and the average particle size only2.1nm. Particle size of QDs could be controlled by adding different amount of sodiumselenosulphate, thus to adjust photoluminescence （PL） from480nm to560nm. AndQDs have narrow and symmetrical PL spectra, and the PL quantum yield increase to32%. The interaction with the Schiff base show that Schiff base can effectively enhancethe PL of QDs in a certain range, but excess Schiff base will quench the PL.2. Thioglycollic acid （TGA）-CdSe QDs were prepared in aqueous phase by additionof different surfactants. Several nanometer-sized, well-dispersed, fluorescence-enhancedCdSe QDs could be obtained by addition of long-chain anionic and non-ionicsurfactants. However, the PL of CdSe QDs is quenched and the particle aggregation bythe addition of cationic surfactants.3. The PL intensity of both CMC-CdSe QDs and TGA-CdSe QDs could be enhancedupon illumination. The X-ray photoelectron spectrum （XPS） and PL spectra confirm SeO₂formed by irradiation could passivate the CMC-CdSe QDs surface and give rise toa great increment in PL intensity. And CdS shell formed in the system of TGA-CdSeQDs could oxide water and produce hydroxyl radicals. It made TGA-CdSe QDs didn’thave selectivity for most of dyes and could achieve well results of degradation in a shorttime.4. CdSe microspheres and CdSe/SC nano-composite as photocatalysts wereprepared in aqueous phase. CdSe nano-microspheres could partially degrade RhodamineB （RhB） and light irradiation can increase the catalytic activity and enhance thephotocatalysis ability of the catalyst. The effect of light treatment in the photocatalyticdegradation of RhB is two sides: On one hand, it can enhance the degree ofcrystallization without change the form of crystal that increase the adsorption of RhB,and oxidize Se（-II） to Se（IV）. On the other hand, it can extend the spectral response.CdSe nanoparticles was loaded on SC successfully by coordinated bond，rather than thesimple doping or mixing. The nano-composite is excellent photocatalyst.