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Formation of colloidal semiconductor nanocrystals. The aspect of nucleation

Abstract

The present work describes different techniques to control some major parameters of colloidal nanocrystals. The individual techniques rely on the manipulation of the nucleation event. The sensitive control of the nanocrystals' size and shape is discussed. Furthermore the formation of hybrid nanocrystals composed of different materials is presented. The synthesis technique for the production of the different samples involves organic solvents and surfactants and reactions at elevated temperatures. The presence of magic size clusters offers a possibility to control the size of the nanocrystals even at very small dimensions. The clusters produced comprise ca. 100 atoms. In the case of CdSe, nanocrystals of this size emit a blue fluorescence and therefore extend the routinely accessible spectrum for this material over the whole visible range. Samples fluorescing in the spectral range from green to red are produced with standard recipes. In this work a reaction scheme for magic size clusters is presented and a theoretical model to explain the particular behaviour of their growth dynamics is discussed. The samples are investigated by optical spectroscopy, transmission electron microscopy, X-ray diffraction and elemental analysis. A method to form branched nanocrystals is discussed. The branching point is analysed by high resolution transmission electron microscopy  More>>
Authors:
Publication Date:
Aug 17, 2007
Product Type:
Thesis/Dissertation
Report Number:
ETDE-DE-1814
Resource Relation:
Other Information: TH: Diss.
Subject:
36 MATERIALS SCIENCE; NUCLEATION; SHAPE; HYBRIDIZATION; SYNTHESIS; SPECTRA; SURFACTANTS; TRANSMISSION ELECTRON MICROSCOPY; TWINNING; GOLD; ORGANIC SOLVENTS; X-RAY DIFFRACTION; COLLOIDS; CRYSTAL GROWTH; SEMICONDUCTOR MATERIALS; QUANTUM DOTS; PARTICLE SIZE; CADMIUM SELENIDES; CHEMICAL COMPOSITION; CRYSTAL DEFECTS; ZINC SELENIDES; CADMIUM TELLURIDES; PHONONS; LIGHT SCATTERING; RESONANCE SCATTERING; LEAD SELENIDES; CADMIUM SULFIDES; SOLUBILITY; ZINC SULFIDES; TEMPERATURE DEPENDENCE
OSTI ID:
21060444
Research Organizations:
Muenchen Univ. (Germany). Fakultaet fuer Physik
Country of Origin:
Germany
Language:
English
Other Identifying Numbers:
TRN: DE08G8064
Availability:
Commercial reproduction prohibited; OSTI as DE21060444
Submitting Site:
DE
Size:
327 pages
Announcement Date:
Aug 06, 2008

Citation Formats

Kudera, S. Formation of colloidal semiconductor nanocrystals. The aspect of nucleation. Germany: N. p., 2007. Web.
Kudera, S. Formation of colloidal semiconductor nanocrystals. The aspect of nucleation. Germany.
Kudera, S. 2007. "Formation of colloidal semiconductor nanocrystals. The aspect of nucleation." Germany.
@misc{etde_21060444,
title = {Formation of colloidal semiconductor nanocrystals. The aspect of nucleation}
author = {Kudera, S}
abstractNote = {The present work describes different techniques to control some major parameters of colloidal nanocrystals. The individual techniques rely on the manipulation of the nucleation event. The sensitive control of the nanocrystals' size and shape is discussed. Furthermore the formation of hybrid nanocrystals composed of different materials is presented. The synthesis technique for the production of the different samples involves organic solvents and surfactants and reactions at elevated temperatures. The presence of magic size clusters offers a possibility to control the size of the nanocrystals even at very small dimensions. The clusters produced comprise ca. 100 atoms. In the case of CdSe, nanocrystals of this size emit a blue fluorescence and therefore extend the routinely accessible spectrum for this material over the whole visible range. Samples fluorescing in the spectral range from green to red are produced with standard recipes. In this work a reaction scheme for magic size clusters is presented and a theoretical model to explain the particular behaviour of their growth dynamics is discussed. The samples are investigated by optical spectroscopy, transmission electron microscopy, X-ray diffraction and elemental analysis. A method to form branched nanocrystals is discussed. The branching point is analysed by high resolution transmission electron microscopy and proves for the occurrence of a multiple twinned structure are strengthened by simulation of the observed patterns. Two different techniques to generate nanocrystals of this type are presented. The first relies on a seeded growth approach in which the nucleation of the second material is allowed only on de ned sites of the seeds. The second technique uses the tips of pre-formed nano-dumbbells as sacrificial domains. The material on the tips is replaced by gold. Hybrid materials are formed by a seeded-growth mechanism. Pre-formed nanocrystals provide the nucleation sites for the second material. (orig.)}
place = {Germany}
year = {2007}
month = {Aug}
}