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CdS Quantum Dots (cd + quantum_dot)
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] Electroluminescent Cu-doped CdS Quantum DotsADVANCED MATERIALS, Issue 28 2009Jan W. Stouwdam Incorporating Cu-doped CdS quantum dots into a polymer host produces efficient light-emitting diodes. The Cu dopant creates a trap level that aligns with the valence band of the host, enabling the direct injection of holes into the quantum dots, which act as emitters. At low current densities, the luminance efficiency maximizes at 9,cd A,1, providing an external quantum efficiency of 5%. [source] Circularly Polarized Luminescent CdS Quantum Dots Prepared in a Protein Nanocage,ANGEWANDTE CHEMIE, Issue 39 2010Dr. Masanobu Naito In Ferritin (einem ,-Helix-reichen, rhombischen, dodekaedrischen Protein) hergestellte CdS-Quantenpunkte (CdS-QDs) zeigen linkshändige circular polarisierte Lumineszenz (CPL) aus einem direkten Übergang und aus Oberflächenstörstellen, die relativ große Anisotropiefaktoren aufweisen. Bei Laser-Photoätzen findet man mit abnehmender QD-Größe eine Blauverschiebung der PL/CPL-Banden von Oberflächenstörstellen, und die Bande des direkten Übergangs verschwindet. [source] Magnetoabsorption coefficient of donor impurities in CdS quantum dotPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2006A. Didi Seddik Abstract A theoretical study of the donor-related absorption coefficient in spherical CdS quantum dots (QD) in the presence of a uniform magnetic field is performed. The wave functions and the eigenvalues of the initial and final states are obtained in the effective-mass approximation by using a variational method and a perturbation method, respectively. The results obtained show that the absorption coefficient presents essentially two peaks; one associated with on-center donors and another related to transitions involving donors at the QD edge. The dependences of the absorption coefficient on sample dimensions, the magnetic field strength and the light polarization are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of Quantum Dots Modified Acetylcholinesterase Biosensor for the Detection of TrichlorfonELECTROANALYSIS, Issue 22 2006Xiao-Hua Li Abstract Poly (N -vinyl-2-pyrrolidone) (PVP)-capped CdS quantum dots (QCdS-PVP) was synthesized with CdCl2 and Na2S in the presence of PVP. QCdS-PVP has been used for the immobilization and stabilization of the acetylcholinesterase (AChE). The electrocatalytic activity of QCdS-PVP leads to a greatly improved electrochemical detection of the enzymatically generated thiocholine product, and higher sensitivity and stability. The GCE/QCdS-PVP/AChE biosensor was used for the detection of organophosphate pesticides (OPs), such as trichlorfon. The sensor performance, including pH and inhibition time, was optimized with respect to operating conditions. Under the optimal conditions, the biosensor was used to measure as low as 12 ppb trichlorfon with a 5-min inhibition time. [source] Photosensitization 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] Electroluminescent Cu-doped CdS Quantum DotsADVANCED MATERIALS, Issue 28 2009Jan W. Stouwdam Incorporating Cu-doped CdS quantum dots into a polymer host produces efficient light-emitting diodes. The Cu dopant creates a trap level that aligns with the valence band of the host, enabling the direct injection of holes into the quantum dots, which act as emitters. At low current densities, the luminance efficiency maximizes at 9,cd A,1, providing an external quantum efficiency of 5%. [source] Grazing incidence small-angle X-ray scattering studies of the synthesis and growth of CdS quantum dots from constituent atoms in SiO2 matrixJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2003U.V. Desnica Grazing incidence small angle X-ray scattering was applied to study the synthesis and growth of CdS quantum dots (QDs) from Cd and S atoms implanted in SiO2. For a dose of 1017/cm2, the partial synthesis of CdS QDs occurred already during implantation, with only moderate size increase upon subsequent annealing up to Ta=1073 K. The dynamics of QD synthesis and growth were considerably different for just two times lower dose, where synthesis started only if the implanted samples were annealed at Ta = 773 K or higher, with a strong increase of the size of QDs upon annealing at higher Ta. The results suggest that high-dose implantation followed by low-temperature annealing could lead to better defined sizes and narrower size distributions of QDs. [source] Raman spectroscopy of II,VI semiconductor nanostructures: CdS quantum dotsJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2003B. Schreder Abstract Information about confinement effects and dot,matrix interactions of CdS nanoparticles was obtained from resonance Raman spectroscopy. The quantum dots had diameters of 3 and 5 nm and were prepared with and without organic spacer groups. It was found that the spacer improves the quality of the nanocrystallites. No phonon confinement shift could be observed even for the small quantum dots. The linewidths of the overtone series point to a mechanism of vibrational relaxation which is dominated by the decay of the LO phonons into acoustic phonons. Copyright © 2003 John Wiley & Sons, Ltd. [source] Magnetoabsorption coefficient of donor impurities in CdS quantum dotPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2006A. Didi Seddik Abstract A theoretical study of the donor-related absorption coefficient in spherical CdS quantum dots (QD) in the presence of a uniform magnetic field is performed. The wave functions and the eigenvalues of the initial and final states are obtained in the effective-mass approximation by using a variational method and a perturbation method, respectively. The results obtained show that the absorption coefficient presents essentially two peaks; one associated with on-center donors and another related to transitions involving donors at the QD edge. The dependences of the absorption coefficient on sample dimensions, the magnetic field strength and the light polarization are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Quantum dots , electrospray ionization mass spectrometry: 3-mercaptopropanic acid capped CdS quantum dots as accelerating and enrichment probes for microwave tryptic digestion of proteinsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2009Kamlesh Shrivas First page of article [source] Donor,Acceptor Systems: Energy Transfer from CdS Quantum Dots/Rods to Nile Red DyeCHEMPHYSCHEM, Issue 14 2008Suparna Sadhu Abstract We demonstrate strong evidence of shape-dependent efficient resonance energy transfer between CdS quantum dots (QDs) and quantum rods (QRs) (donor) to Nile Red dye (acceptor). We also report a simple solution-based method for the preparation of high quality CdS QDs and CdS QRs at relatively low temperature. The observed quenching of PL intensities are 78.8,% and 63.8,% for CdS QDs and QRs, respectively in the presence of Nile Red dye. The calculated energy-transfer efficiencies are 45,% and 19,% from QDs and QRs to dyes, respectively. The energy transfer varies with changing the shape of the nanoparticles. The estimated Förster distances (R0) are 37.8 and 33.8 Å for CdS QDs and QRs, respectively. In the present study, the estimated distances (r) between one donor and one acceptor are 39.1 and 43.1 Å for QDs and QRs, respectively, using the efficiency of Förster resonance energy transfer (FRET) which depends on the inverse sixth power of the distance of separations between one nanocrystal and one dye molecule. Considering single donor and multiple acceptors interactions, the calculated average distances (rn) between the donor and acceptor are 47.7 and 53.9 Å for QD's and QR's, respectively. The steady-state and time-resolved spectroscopic analysis of nanoassemblies confirm the formation of one donor and multiple acceptors. [source] | |||||||||||||