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CdS Nanocrystals (cd + nanocrystal)
Selected AbstractsPhotosensitization of TiO2 Nanostructures with CdS Quantum Dots: Particulate versus Tubular Support ArchitecturesADVANCED FUNCTIONAL MATERIALS, Issue 5 2009David R. Baker Abstract TiO2 nanotube arrays and particulate films are modified with CdS quantum dots with an aim to tune the response of the photoelectrochemical cell in the visible region. The method of successive ionic layer adsorption and reaction facilitates size control of CdS quantum dots. These CdS nanocrystals, upon excitation with visible light, inject electrons into the TiO2 nanotubes and particles and thus enable their use as photosensitive electrodes. Maximum incident photon to charge carrier efficiency (IPCE) values of 55% and 26% are observed for CdS sensitized TiO2 nanotube and nanoparticulate architectures respectively. The nearly doubling of IPCE observed with the TiO2 nanotube architecture is attributed to the increased efficiency of charge separation and transport of electrons. [source] Synthesis and Self-Assembly of Triangular and Hexagonal CdS Nanocrystals,ADVANCED MATERIALS, Issue 24 2005H. Warner CdS nanocrystals with cubic, triangular, and hexagonal geometries have been synthesized using simple wet-chemistry techniques. Analysis of the crystal structures revealed that the cubic nanocrystals have a zinc-blende crystal structure whilst the triangular and hexagonal CdS nanocrystals have a wurtzite crystal structure. When dried, these CdS nanocrystals self-assemble to form complex structures such as linear rods (see Figure), nanoarrows and dimers. [source] Investigation of nanocrystalline CdS,glutathione particles by radial distribution functionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2003V. I. Korsounski Using high-energy synchrotron radiation, powder diffraction experiments were carried out on CdS nanocrystals stabilized with glutathione. The radial distribution function was calculated from the data and analysed. The nanoparticle core, of diameter estimated as 15,20,Å, consists of Cd and S atoms in the proportion 1:1. Inside the core, both Cd and S atoms coordinate each other approximately tetrahedrally. The surface S atoms are connected to just two or three Cd atoms of the core and belong to the glutathione molecules of the particle shell. These S atoms are also a part of the core structure and contribute about one half of the total number of S atoms per particle. First-neighbour Cd,S distances are 2.523,Å with a narrow distance distribution. No difference is observed between the lengths of Cd,S bonds involving the sulfur of the glutathione molecules and the sulfur atoms which are solely bound to Cd. The bond angle Cd,S,Cd at the surface bridging S atoms of glutathione is ca 99.5°, i.e. significantly smaller than an average one of 109.5° characteristic of the Cd and S atom packing inside the core. Beyond the range of the near interatomic distances, the influence of the surface and the defects cause a significant distinction of the particle core structure from those of zincblende and wurtzite, characteristic of bulk CdS. [source] Structure and Properties of CdS/Regenerated Cellulose NanocompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Dong Ruan Abstract Summary: Novel inorganic-organic hybrid materials composed of cadmium sulfide (CdS) semiconducting nanocrystals and regenerated cellulose (RC) were prepared by using in situ synthesizing method. Cellulose was dissolved in a 6 wt.-% NaOH/4 wt.-% urea/thiourea aqueous solution at low temperature followed by addition of cadmium chloride (CdCl2), resulting that the CdS nanocrystals were successfully grown in situ in the cellulose solution. Nanocomposite films containing homogeneous CdS nanoparticles were obtained by casting the resulting solution. Their structure and optical properties were characterized by X-ray photoelectron spectroscopy, wide-angle X-ray diffraction, thermogravimetry analysis, dynamic mechanical analysis, atomic force microscopy, transmittance electronic microscope, UV-vis spectroscopy, and photoluminescence spectroscopy. The experimental results confirmed that the CdS nanocrystalline existed in the composite films, and cellulose matrix provided a confined medium for CdS particle growth in uniform size. The CdS/RC composites showed narrow emission in photoluminescence spectra, and their optical absorbance in the UV range was higher than that of the cellulose film without CdS. This work provided a simple method to prepare cellulose functional materials in NaOH/urea aqueous solution. Photoluminescence of CdS/RC nanocomposites and TEM image of CdS nanocrystals dispersed in RC matrix. [source] Raman scattering spectra of CdS nanocrystals fabricated by a reverse micelle methodPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2009Aishi Yamamoto Abstract Raman scattering (RS) spectra of CdS nanocrystals (NCs) fabricated by a reverse micelle method were studied and were analysed using a phonon confinement model. One broad and red-shifted RS peak due to the LO phonon confined in CdS NCs was observed. The RS spectra were calculated using a phonon confinement model with the NC sizes estimated from the optical absorption spectra. The calculated RS spectra as suming that the NCs have the wurtzite structure reproduce the experimental spectra better than those assuming zincblende structure, which is consistent with the result of transmission electron microscope (TEM) observations. Our finding indicates that the crystal structure of the nanocrystal can be determined by the analyses of Raman scattering spectral shape. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Trap state emission of water-soluble CdS nanocrystalsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2009W. Lü Abstract We prepared water-soluble CdS nanocrystals (NCs) capped by the poly (ethylene glycol)-b-poly (2-(N,N -dimethylamino)ethyl methacrylate) chain. The photoluminescence (PL) properties of CdS NCs are investigated by time-resolved and temperature-dependent PL spectra. It is found that the PL band of CdS NCs is dominated by two trap state emissions, respectively. Due to the trap state emissions, fluorescent resonance energy transfer from CdS NCs to organic dyes (Texasred) can be observed, which suggests the potential application of trap states of CdS NCs for fabrication of biosensors. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Polarization-resolved degenerate four-wave mixing of CdS nanocrystals in a nonresonant regionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2006S. M. Ma Abstract The third-order susceptibilities of various concentrations of TOPO-passivated CdS nanocrystals (NCs) with the size near the Bohr radius were investigated using polarization-resolved degenerate four-wave mixing (DFWM) in a nonresonant excitation region with 532 nm wavelength and 8 ns pulse width. The second hyperpolarizabilities ,,hxxxx, and ,,hxyyx, of the CdS NCs were ,1.25 × 10,42 m5/V2 and ,3.66 × 10,43 m5/V2, respectively. The ratio (,,hxyyx,/,,hxxxx,) of the hyperpolarizabilities was ,0.29 that indicated a large contribution of electronic polarization process to the third-order nonlinearity of CdS NCs. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparison between laser-induced nucleation of ZnS and CdS nanocrystals directly into polymer matricesPOLYMER COMPOSITES, Issue 6 2010Athanassia Athanassiou The nucleation of two kinds of crystalline nanoparticles, zinc sulfide (ZnS), and cadmium sulfide (CdS), is achieved directly into specific sites of polymer matrices after their irradiation with UV laser pulses. The starting samples consist of polymers doped with precursors of Zn or Cd thiolate that are proved to decompose after the absorption of UV light, resulting into the nanoparticles formation. The growth of the crystalline nanostructures is followed throughout the irradiation of the samples with successive incident pulses, by different methods, such as transmission electron microscopy, atomic force microscopy, confocal microscopy, and X-ray diffraction. Special attention is paid to the difference of the formation pathways of the two kinds of nanoparticles studied, because the Cd thiolate precursor exhibits much higher absorption efficiency than the Zn thiolate one, at the applied UV wavelength. Indeed, CdS nanoparticles become evident after the very first incident UV pulses, whereas the formation of ZnS nanocrystals requires rather prolonged irradiation, always through a macroscopically nondestructive procedure for the polymer matrix. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] |