Preparation And Optical Properties Of CdS/CdSe Quantum Dots In Paraffin Liquid And Oleic Acid

Quantum dots (QDs), also known as“man-made”atomic, are quasi-zero-dimensionalfluorescence semiconductor nanomaterials, which are 1-10 nm in diameter and generallycomprised of II-VI group or III-V group elements. Due to its special effects, such as broadabsorption spectrum, narrow emission spectrum and symmetrical distribution, photochemicalstability and so on, quantum dots have widespread application prospects in chemical catalysis,electronic devices, optical fiber communication components, semiconductor devices, solarcells, biological fluorescence probes and so on. Recently, the most common method tosynthesize excellent optical performance quantum dots is the metal organic synthesis.Although high quality quantum dots could be obtained, the high cost and high pollutiondefects of the solvent TOP and TOPO hinder the application of quantum dots. For this reason,seeking a cheap, green, simple and easy, low toxic, less pollution and mild reaction conditionis still very important in the filed of quantum dots preparation. In addition, it is moresignificant and valuable to achieve the development of electronic devices through improvingthe surface and photochemical properties of the particles.In this thesis, paraffin liquid is chosen as solvent, oleic acid as the complex agent, CdS,CdSe quantum dots are successfully synthesized via green oil phase synthetic process,characterized by various measures and its optical properties have been investigated. In orderto control the size of as-prepared quantum dots, the influences of reaction time, concentrationof reactants and reaction temperature in the green synthetic process have been investigated tofurther improve the process of the preparation of CdS, CdSe quantum dots and enhance thecontrollability of the products. Surface modification on the preparation of the steady CdS,CdSe quantum dots is also employed, mainly through wrapping CdS to form CdSe/CdScore-shell quantum dots, aims at enhancing the fluorescence quantum yield. The method ofmodification has been explored and a set of effective processes been summarized.Surface morphology, crystal structure characterization and optical performance areinvestigated by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction(XRD), fluorescence spectrometer (PL) and ultraviolet-visible absorption spectrometer(UV-vis). The results show that well dispersion, uniform particle size, small size, goodfluorescence CdS quantum dots, CdSe quantum dots and CdSe/CdS core-shell quantum dotsare prepared in this method. It can be seen that the optical performance of quantum dots isimproved through the experiment.