Dissertation > Excellent graduate degree dissertation topics show

Study on the Preparation and Correlative Properties of ZnSe、CdSe、Cu2Se Nanomaterial

Author: YanWei
Tutor: HuChenGuo
School: Chongqing University
Course: Materials Physics and Chemistry
Keywords: CHM method ZnSe nanorods CdSe nanocrystals Cu2Se nanocrystals
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 358
Quote: 0
Read: Download Dissertation

Abstract


With the development of the science and technology, especially for semiconductor technology, the need for high efficiency material becomes more urgent. Especially, as the size of the nano-scaled materials and quantum dots are comparable to Bohr radius, novel electronic states and optical properties could be observed, therefore, there is great interest for researchers worldwide to study nano-semiconducting materials.We have first synthesized the crystalline nanorods of zinc selenide （ZnSe） by the composite-hydroxide-mediated （CHM） approach. The diameters of nanorods are about 200-300 nm, and the lengths are about 1-2μm. Humidity sensors based on ZnSe nanorods were fabricated. Their responsiveness to humidity for static and dynamic testing proved a high sensitivity of the sensors. The change of resistance is about three orders of magnitude as the relative humidity （RH） increases from 20% to 85%. The response-time and recovery-time of the resistance is 50 s and 81 s versus the changes of relative humidity from 20% to 85% and from 85% to 20%, respectively. The results indicate promising applications of ZnSe nanorods as a highly sensitive electronic device in environmental monitoring and humidity control.Single-crystalline CdSe nanostructures has been directly synthesized for the first time by the composite-hydroxide-mediated approach. The advantages of the method are of easy synthesis, at lower temperature, absence of capping agents and low cost, with a great potential for scale-up. The morphology of the CdSe can change from nanoparticles to uniform nanorods, whereas the phase transfers from zinc blende to wurtzite structure by adding small amount of water at fixed temperature. This result challenges the speculation that temperature is a cause of the phase transformation that has been proposed by other groups. Optical spectrum measurements of the two sorts of CdSe nanostructures exhibit same band gap. Humidity sensitivity is investigated for the first time on the sensors made from these CdSe nanostructures, exhibiting their ultrasensitive properties.Cu2Se nanocrystals starting from CuCl2.2H2O and Se powder were synthesized through a novel approach based on chemical reactions in composite-hydroxide-melts at 200℃for 24h. The XRD indicated that the sample was cubic structured Cu2Se with lattice constants of a = 5.787, and lattice symmetry group of pm 3m（225）. SEM showed that the crystals were nanosheets with the thickness and width of were about 10-20 nm, 200～300 nm sheets, respectively. When a small amount of deionized water was added in the vessel during synthesis process, some stick shape amorphous products appeared in the samples, which reduced the quality of the Cu2Se crystals. According to coordination polyhedron growth unit model, the binding energy of growth units has been calculated and the chemical interaction mechanism for synthesizing Cu2Se nanocrystals has been discussed in detail.

Related Dissertations

  1. Synthesis and Properties of Novel CdSe Nanocrystals,TB383.1
  2. Soluble zero-dimensional and one-dimensional semiconductor nanomaterials preparation and its application in the analysis -ZnSe , CdSe,TB383.1
  3. Synthesis and Temperature-dependent Band Gap of CdSe Colloidal Nanocrystals,TB383.1
  4. Green Syntheses and Characteristics of Semiconductor Nanocrystals CdSe and ZnSe,TB383.1
  5. Solution Chemical Synthesis of II-VI Semiconductor Nanocryatals and Their Photoelectrical Application,O649
  6. Synthesis and Properties of Tellurium Compound Nanomaterials,TB383.1
  7. Study of Ⅱ-Ⅵ Nanostructural Semiconductors by X-ray Absorption Fine Structure,TB383.1
  8. Hydrothermal Synthesis of Oxide Hollow Spheres,TB383.4
  9. Investigation of Fabrication, Characterization and Property of Fuctional Titanium Dioxide Nanoporous Materials,TB383.1
  10. Preparation of tungsten oxide based nanomaterials and gas properties,TB383.1
  11. Low- dimensional Nanomaterials solid state synthesis and characterization,TB383.1
  12. Inorganic / organic magnetic suspension preparation and application,TB383.1
  13. The Sythesis and Characterztion of Water-solubilty and Nano-Phthalocyanine Compound,TB383.1
  14. Preparation and Characterization of Rare-earth Luminescent Material CaWO4: Eu3+,TB383.1
  15. Synthesis, Characterization and Properties of One-dimensional Silicon Carbide Nanomaterials,TB383.1
  16. Synthesis of Silver Nanoparticles on Modified Multi-walled Carbon Nanotubes and Their Antimicrobial Effects,TB383.1
  17. The Research on Preparation Technology and Sintering Behavior of Rare Earth Aluminates (Dy3Al5O12、 NdAlO3、LaAl11O18),TB383.3
  18. Synthesis of SnO2 by Flame Spray Pyrolysis: Structures Design and the Gas Sensing Properties,TB383.1
  19. Effect of Cholesterol on Liposome Membrane Bilayer Structure、Liposome Properties and Function,TB383.2
  20. Hydrogenated nanocrystalline silicon photovoltaic materials in hydrogen bonding defects in material structure and the impact of,TB383.1
  21. A Study on the Fullerene Nanocomposites,TB383.1

CLC: > Industrial Technology > General industrial technology > Materials science and engineering > Special structural materials
© 2012 www.DissertationTopic.Net  Mobile