Dissertation > Excellent graduate degree dissertation topics show

Study of Relationship between Structure and Composition of Novel Biocompatible Hybrid Core/shell Nanocrystals

Author: LiuNing
Tutor: YangPing
School: Jinan University
Course: Materials Science and Engineering
Keywords: Semconductor nanocrystals CdTe Hybrid structure Photoluminescencequantum yields Photoluminescence lifetime
CLC:
Type: Master's thesis
Year: 2013
Downloads: 4
Quote: 0
Read: Download Dissertation

Abstract


The small size the semiconductor nanocrystals （NCs） made them owns a big specificsurface area, which let they have a lot of novel properties that different from the bulk materials.Rencetly, the synthesis and application of NCs become one of the most widely study fileds. Inthis paper, we focused on the subject of “Study of relationship between structure andcomposition of novel biocompatible hybrid core/shell nanocrystals” and obtained a novelfunctional sol-gel SiO2shell material, the relationship between the structures and properties offunctional core/shell NCs were study systemically. The main contents of the project are asfollows:Firstly, we use mercapto acids （such as thioglycolic acid （TGA） and3-mercaptopropionicacid （MPA）） as stabilizer to generate CdTe NCs for the stabilizer has a great effect on theproperties of the NCs. We could get CdTe NCs with the photoluminescence （PL） wavelengthtunable from530nm to750nm. During our experiment, the Te and NaBH4were used as anionprecursor, replaced toxic H2Te, which made the CdTe NCs more friend to the environment.Further more, such method owns the advantages of cheap, convenient and the products own alot of super properties, such as high PL quantum yield （PL QY, up to70%）, good stability andso on, which important for further applications.Secondly, the CdTe NCs obtained through the aqueous synthesis method reacted underlow temperature and undergo a long reaction time, which made the NCs have a low crystallinityand lots of surface defects. In order to overcome these weaknesses, we use the hydrothermalsynthesis method to get type-Ⅱ CdTe/CdSe core-shell NCs. During the preparation, we choosethe less toxic and stable Na2SeO3as Se precursor which made the process more convenient. Thetype-Ⅱ heterojunction of CdTe/CdSe core-shell NCs generated under high temperature andhigh pressure environment due to the difference band structure between CdTe and CdSematerials. Such type-Ⅱ heterojunction nanostructure made the type-ⅡNCs have a lot ofproperties that different from the type-Ⅰ NCs fundamentally （such as CdTe, CdS）, such as highPL QY, wide PL emission wavelength, controlled size and good stability in the PBS solution,which good for application.Further, the method relateed above have been greatly developed and their products also owned a lot of super PL properties. But it is relative difficult for the NCs to proceed surfacefunctionalization, which hinder their application in biologic hoods. According to the study, theproperties of the NCs are greatly depends on its composition and structure, as a result, it is animportant field for exploring the relation between NCs and its complex. In order to expend theapplication fields of the aqueous NCs, we obtained a new kind of hybrid core-shellnanostructure, that means generate a novel functional biocompatible sol-gel SiO2shell on theaqueous core NCs. Such hybrid SiO2nanostructure exhibited a serious of super properties thatdifferent from the traditional NCs greatly, such as narrow full-width at half-maximum （FWHM）of PL spectra, long PL lifetime, high PL QY （from30%improved to80%）, good stabilization inphosphate buffer solution （PBS） and so on. The NCs own a good biocompatibility for it is easyto surface functionalization. According to explore the details of the preparation conditions, weinvestigate the relationship among structure, properties and composition. As a result, the highPL QY hybrid NCs can be obtained through controlling the size of the core, the compositionand thickness of the shell material. Those novel properties made the NCs have great applicationin fluorescence labeling, fluorescence probe, photoelectrical devices. We use a serious ofmethods to characterize the properties of the NCs, such as transmission electron microscopy（TEM）, the absorption and PL spectra, X-ray powder diffractometer, PL lifetime measurementand total internal reflection fluorescence microscope （TIRFM）. By comparing the properties ofthe hybrid NCs to its core, we find that the functional hybrid SiO2shell can passivate thesurface of the core NCs, which made it owns a good stability and long PL lifetime （such as thelifetime of the hybrid SiO2-coated CdTe NCs was45.45ns compared to its core which lifetimeis26.80ns）.Lastly, the application of the high quality aqueous NCs based on CdTe NCs wasinvestigated as well as the PL properties of the NCs after being compound into the functionalfilms and nanofibers. According to the results, the functional film containing TGA-CdTe NCsexhibited multicolor emission, high stability, high PL brightness as well as high concentrationof NCs. Other sides, the PL properties of the NCs can be maintained effectively. The functionalnanofibers containing CdTe or hybrid SiO2-coated CdTe NCs own a stable PL emission, largedraw radio and the uniform diameter was range from50nm to150nm. All of the resultsindicate that the application area of the aqueous NCs can be expanded effectively by chosing super medium and optimizing preparation method.

Related Dissertations

  1. Studies on the Synthesis of Water-soluble Quantum Dots Modified by PEG and the Interaction with Peptide,O471.1
  2. Research of Hybrid Application Layer Multicast Model Based on Load-balance,TP393.02
  3. Direct Electrochemistry of Proteins on CdTe Quantum Dots,O646
  4. CdTe Quantum Dot Based Detection Method for Pathogenic Bacteria and Macrophages,TS207.4
  5. Applications of One-dimensional CdTe and CdHgTe Nanorods in Fluorescence Analysis,TB383.1
  6. Study on the Seismic Performance of SRC-RC Transfer Column,TU398.9
  7. Preparation of CdTe Quantum Dots and Its Preliminary Application,Q503
  8. Study on Three-Dimensional Photonic Crystal Operate the Illumination Properties of CdTe Quantum Dots,O614.242
  9. Synthesis and Water-soluble Modification of Quantum Dots,O649
  10. Analysis of Seismic Performance of SRC-RC Transfer Columns by Different Constructional Measure,TU398.9
  11. Self-assembly of CdTe QDs at the Air/Water Interface and Preparation of CdTe/Au Nanocomposite,TB383.1
  12. Biocampatible Modification of CdTe Quantum Dots and Its Interactions with Proteins,O629.73
  13. Studies on Cytotoxicity of Cadmium Telluride Quantum Dots Prepared in Aquous Phase Using Human Cervical Cancer Cells as a Model,R737.33
  14. The Seismic Performance Analysis of Steel Frame-Rc Core Wall Structure,TU352.11
  15. Studying on a CdTe Quantum Dots Electrochemiluminescent Sensor Based on Carbon Nano-tubes Supporting,TP212.2
  16. Photo-Assisted Photoluminescent Enhancement of Water-Soluble CdTe Nanocrystals,O614.242
  17. Preparation of the New Water-Soluble CdTe Quantum Dots Probe and Their Application on MDR Study,TQ617.3
  18. Studies on the Interaction of CdTe Quantum Dots with Microbiomolecular,Q6-3
  19. Preparation and Bioanalytical Application of CdTe/CdS Quantum Dots,Q503
  20. The Synthesis of CdX (X: Se, Te) Semiconductor Nanomaterial and Its Analysis Applications,TB383.1
  21. The Synthesis and Applications in Cell Immuno-Labeling of Fe3O4/CdTe Nanocomposites,TB383.1

CLC: >
© 2012 www.DissertationTopic.Net  Mobile