Experimental Determination Of The Extinction Coefficient Of CdSe And CdS With Zinc Blende Structure

Semiconductor nanocrystals due to their unique quantum size effect, surface effect, macroscopic quantum tunneling effect, Coulomb blockage effect, the dielectric confinement effect, small size effect, quantum tunneling effect of special character, in the new energy development and research, bio-In the field and new materials research and development has become increasingly important research value. In addition, light-emitting quantum dots of high purity, high luminous efficiency and good optical properties, and gradually began to replace the traditional dye-doped, in the light-emitting materials, optical materials, optical, catalytic materials, quantum lasers, and many also have a very wide range of applications Prospects.In recent years, based on the experimental conditions and environment improvement, a member of the family of semiconductor quantum dots tend to diversify. Single quantum dots from the traditional to the core-shell structure of quantum dots, doped quantum dots, the exchange-based quantum dots and quantum point of near-infrared quantum dots and other new development, while broadening the application field of quantum dots. Early studies of quantum dots for people to focus on continuous improvement in the preparation of this study for the quantum dots laid a good foundation. With in-depth and practical understanding of the needs, people are the theoretical study of quantum dots, from the shape size to the influencing factors controlled nucleation and growth theory and then discuss quantum dot research is experiencing greater challenges.In practical applications and theoretical research, semiconductor nanocrystals accurately determine the concentration of far-reaching significance. Because different experimental methods and understanding the limitations of the research team obtained II-VI semiconductor nanocrystal extinction coefficient and the relationship between the conclusions of different sizes. Which deeper understanding of the experimental group thought Peng careful experimental design through more perfect get more reliable results, the extinction coefficient of nanocrystalline on the issue of cross-age significance. However, their experiments there are still some loopholes.â…¡-â…¥semiconductor nanocrystals existence of two different crystal structures, and in their experiments, ignoring the different crystal structure and size on the extinction coefficient of the relationship.â…¡-â…¥of semiconductor nanocrystals as the longest and most complete theoretical development of the traditional quantum dots, and its position is self-evident. In the actual research and applications, CdS, CdSe and CdTe areâ…¡-â…¥semiconductor nanocrystals of the more basic subjects, and CdS, CdSe and because the synthesis of both in the preparation of reagents or reaction conditions is to lower the requirements, so CdTe has more extensive than the scope of the studyIn this paper, we CdS, CdSe as the research object, research and practical applications for quantum dots to determine the concentration of difficult problems were studied and discussed. Based on these facts, we focused on the structure of sphalerite and wurtzite crystal structures of two differentâ…¡-â…¥semiconductor nanocrystals separate study on the crystal structure of the nanoparticle situation. In our experiments, by using the now generally accepted into the organic phase prepared by the second heatâ…¡-â…¥semiconductor nanocrystals, also in accordance with the purification process of the present method of forming operations. This thesis consists of two parts. In the second chapter, we first study the precursor solvent and non-coordination mechanism, understanding of selenium powder and non-coordinated solvent ODE reaction mechanism, which occurred between the two redox reaction in the ODE the double bond is opened, the majority of zero price of selenium was reduced to hydrogen selenide, which is the formation of nanocrystals play the part. On this basis, we adopted the optimization of reaction conditions and reaction parameters of the regulation, can be prepared a series of controlled size, shape uniformity, better dispersion of high-quality single cubic structure of spherical CdSe nanocrystals. Its purification, post-treatment negative so obtained by calculating the extinction coefficient and the crystal size of the curve. In further experiments, we will both cubic and hexagonal crystal structure of CdSe nanocrystals, the extinction coefficient-size graph comparing the differences found in the crystal structure led to the extinction coefficient between the two-curves are very different sizes, and then the size range, as size increases, this difference is more significant.In the third chapter, we have a similar system of CdS nanocrystals with the family were likewise. On the traditional part of the heat injection method improved the quality of the CdS were prepared nanoparticles, TEM confirmed by absorption and has a good single-particle dispersion and homogeneity, tested by XRD the preparation of nano crystals Pure cubic crystal structure. Particles purified by the end has been pure nanoparticles, CdSe nanocrystals with the same system in the calculation, we get the cubic CdS Nanocrystals first exciton absorption peak and the particle size diagram and extinction coefficient and particle Size curve diagram of the system for future theoretical research and practical applications are of great significance...