Synthesis and characterization of colloidal CdTe nanocrystals (original) (raw)
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Influence of Growth Time in the Formation of CdTe Nanostructure
Cadmium Telluride (CdTe) nanostructures are grown chemically using a simple cost effective method as chemical reduction route. Ethylenediamine (EDA) has been used as a capping agent while Sodium borohydride is used as a reducing agent. CdTe nanostructures are grown by varying growth time from 3 hours to 9 hours. The samples are all grown at room temperature. The grown nanostructures are characterized structurally by X-Ray diffraction (XRD) and transmission electron microscopy (TEM). The grown nanostructures are characterized optically by Optical Absorption, Photoluminescence (PL) study. Transmission electron microscopy picture indicates that nanostructure changes from nanoparticle to nanorods as growth time increases. An increase in band gap is observed compared to bulk CdTe in each growth condition. This shows quantum confinement. Also band gap decreases as the growth time increases indicating size dependence of band gap. An attempt is made to correlate the structural and optical properties.
Colloidal CdTe Nano Crystals Synthesis and Characterization
2008
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Journal of Applied Spectroscopy, 2012
A colloidal suspension method is used to obtain CdTe nanocrystals modified with thioglycolic acid in aqueous solutions of ethylene glycol. Their photoluminescence spectrum is shifted to shorter wavelengths relative to that of CdTe nanocrystals synthesized in water. It is found that the ethylene glycol molecules participate in the stabilization of the nanocrystals and passivation of surface defects, with an optimum concentration of 10% ethylene glycol in the reactive mixture for production of stably dispersed CdTe. It is difficult to observe plasmon effects in these nanoparticles when Ag nanoparticles are present because cadmium iodide is used as a precursor salt, which leads to the appearance of I 2 , an oxidant for Ag nanoparticles, in the solution. When a protective polyelectrolyte intermediate layer of thickness ~11.7 nm is deposited on a colloidal silver substrate, the photoluminescence intensity of the CdTe nanoparticles increases by a factor of 1.7. The chemical features of these nanoparticle solutions cause their luminescence characteristics to be highly sensitive to the presence of Ag nanoparticles in the solution. Changes in the position and intensity of the photoluminescence peak are observed for concentrations of Ag nanoparticles in the solution as low as 10 -11 mol/l.
GROWTH AND CHARACTERIZATION OF CDTE NANOSTRUCTURES GROWN BY CHEMICAL REDUCTION ROUTE
CdTe nano particles are grown by varying temperature and keeping ratio of reagent constant. The samples are characterized structurally and optically. An increase in band gap is observed compared to bulk CdTe in each growth condition. Also the nanorods formation is found to be favourable at particular temperature. An attempt is made to correlate the structural and optical properties.
Synthesis and characterization of brightly photoluminescent CdTe nanocrystals
Surface Science, 2007
A new synthesis procedure for the preparation of spherical shaped CdTe nanocrystals (NCs) is presented, exhibiting bright luminescence with exceptionally high quantum efficiency (up to 85%). The growth of these NCs occurs in a non-coordinating solvent, octadecene, with the addition of oleic acid/tri-octylphosphine stabilizers, CdO as a precursor for the Cd monomers and additional Cd metal particles as a supplementary Cd reservoir source. The dependence of the crystalline quality and the optical properties of the CdTe NCs, on the initial Cd:Te precursors' molar ratio, and the reaction duration were investigated. It was demonstrated that the NCs' properties improved significantly as the initial Cd:Te molar ratios are increased. The obtained NCs' properties were correlated with measurements of the Cd 0 concentration in Cd metal particles, CdTe NCs and in Cd monomer solutions.
Growth of CdTe nanocrystals by vapor
The CdTe monodisperse nanoparticles and quasi-one-dimensional nanocrystals were obtained by the vapor deposition method. Transmission electron microscopy and X-ray powder diffraction were used to characterize these nanocrystals. It was found that nanocrystals had wurtzite or sphalerite structure depending on the growth conditions.
Luminescence studies of heat treatment influence on size distribution of CdTe nanocrystals
physica status solidi (c), 2006
Variations in absorption and emission spectra induced by thermal treatment are reported for aqueous solutions of thiol-stabilized CdTe nanocrystals with different Cd 2+ :Te 2molar ratios. Heating of colloids was shown to result in appearance of two photoluminescence lines that were assigned to two ensembles of nanocrystals with different mean diameters. Effect of heat treatment on size distribution, absorption and emission properties, and stability of nanocrystals with various Cd 2+ :Te 2molar ratios is discussed in the terms of different coverage of the nanocrystal surfaces with tellurium atoms (ions?) and with thioglycolic acid molecules.
Synthesis and optical properties of CdTe nanocrystals with improved optical properties
Indian Journal of Engineering and Materials Sciences, 2009
CdTe nanocrystals are prepared by hydrothermal route using the reaction between Cd 2+ and KHTc in the presence of thioglycolic acid as the stabilizing agent. Hydrothermal synthesis under optimum conditions resulted in a rapid growth. CdTe nanocrystals with high PL intensity and narrow PL spectra are obtained in less time. The growth mechanism of CdTe nanocrystals is investigated. The growth rate in the initial stage of synthesis is higher in hydrothermal synthesis resulting in an increased growth in diffusion controlled focused region.
Luminescence of CdTe nanocrystals
Journal of Luminescence, 2003
The growth of highly luminescent CdTe nanocrystals synthesized in a mixture of tri-octylphosphine and dodecylamine was investigated. The CdTe nanocrystals grow in time to a constant size which is dependent on the reaction temperature. In the initial stage of the growth particles show a broad defect emission band which is replaced by an efficient excitonic emission after a few minutes of growth. Quantum yields up to 45% were obtained. The life time of the exciton emission increases with quantum yield and reaches a constant value of about 10 ns for the most efficient particles. The life time increase is explained by the reduction of the (fast) non-radiative decay for samples with a higher quantum yield. In CdTe samples aged at room temperature sharp absorption peaks at discrete energies were observed.
2019
Molar concentrations of chemical ingredients in synthesis of nanocrystals were found significant roles in the structural, surface morphology and visible range optical properties of CdTe quantum dots thin films. XRD, FESEM and UV spectrum analysis revealed that the average particle sizes approach 6-11nm quantum dots with increasing molar concentrations. The study of X-ray line profiles proved that peak intensity was increased with increasing of Cd +2 and Te 2ions in the films. The phase structure of the films were found to possess cubic zinc blend structure with (100), (110), (200), (220) and (321) reflection planes at x = 0.1, 0.2, 0.4 and 0.6M and additional planes were also observed at x = 0.8M. In all the films, (200) reflection plane showed most prominent which facilitated estimation of nanoparticle sizes. The sized dependent nanoparticles showed maximum absorption blue shift near 325nm wavelength in ultraviolet regime ascribed as first excitonic transition. This may be attribut...