The Optical Properties of Colloidal Cadmium Sulphide PDF Download
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Author: Simon Richard Stebbing
Publisher:
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Category :
Languages : en
Pages :
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Author: Simon Richard Stebbing
Publisher:
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Category :
Languages : en
Pages :
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Author: Johannes Frenzel
Publisher:
ISBN:
Category :
Languages : en
Pages : 123
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Category :
Languages : en
Pages : 6
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The objectives of this paper are to determine the role of surface states in determining the electrical and optical properties of semiconductor quantum dots in colloidal suspensions, and to use biomolecules to facilitate the chemically-directed assembly of quantum dots networks with densities approximating 10(exp 17) cu cm. Absorption spectra and photoluminescence (PL) spectra of colloidal cadmium sulfide (CdS) quantum dots are analyzed to investigate the role of surface states in determining the electrical and optical properties of these semiconductor quantum dots. In addition, this work demonstrates the utility of using glycine-glycine-glycine-cysteine (GGGC) peptides and crossing-linking chemical reactions to achieve integrated networks of ZnS-coated CdSe quantum dots and CdS quantum dots.
Author: Saraswathi Amma B
Publisher: LAP Lambert Academic Publishing
ISBN: 9783838362670
Category :
Languages : en
Pages : 124
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Semiconductor nanoparticles have drawn much attention due to their size dependent properties. Cadmium Sulphide (CdS), due to its large Bohr exciton diameter, has applications in various areas like optoelectronics, photo catalysis, biological assays, optical data storage and sensing. The optical properties of CdS nanoparticles capped with different capping agents, synthesized in aqueous and non-aqueous medium are presented in this monograph. As surface states have significant influence on the optical properties, surface passivation is important for improving Photoluminescence property apart from controlling the particle size. Stability and the optical properties of CdS - Polyvinyl Alcohol (PVA) nanocomposite films are dealt. The effects of electron irradiation and also, a Zinc Sulphide (ZnS) coating on the luminescence properties of CdS nanoparticles are also given. This monograph is specially targeted to researchers working in the field of semiconductor nanoparticles as well as postgraduate students of Physics, Chemistry, Electrical and Materials Engineering.
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Languages : en
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In this work, the structural, electronic, and optical properties of CdS nanoparticles with sizes up to 4nm have been calculated using density-functional theory (DFT). Inaccuracies in the description of the unoccupied states of the applied density-functional based tight-binding method (DFTB) are overcome by a new SCF-DFTB method. Density-functional-based calculations employing linear-response theory have been performed on cadmium sulfide nanoparticles considering different stoichiometries, underlying crystal structures (zincblende, wurtzite, rocksalt), particle shapes (spherical, cuboctahedral, tetrahedral), and saturations (unsaturated, partly saturated, completely saturated). For saturated particles, the calculated onset excitations are strong excitonic. The quantum-confinement effect in the lowest excitation is visible as the excitation energy decreases towards the bulk band gap with increasing particle size. Dangling bonds at unsaturated surface atoms introduce trapped surface states which lie below the lowest excitations of the completely saturated particles. The molecular orbitals (MOs), that are participating in the excitonic excitations, show the shape of the angular momenta of a hydrogen atom (s, p). Zincblende- and wurtzite-derived particles show very similar spectra, whereas the spectra of rocksalt-derived particles are rather featureless. Particle shapes that confine the orbital wavefunctions strongly (tetrahedron) give rise to less pronounced spectra with lower oscillator strengths. Finally, a very good agreement of the calculated data to experimentally available spectra and excitation energies is found.
Author: Paul Edward Sotak
Publisher:
ISBN:
Category : Cadmium sulfide
Languages : en
Pages : 218
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Author: Paul A. Faeth
Publisher:
ISBN:
Category : Cadmium crystals
Languages : en
Pages : 28
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Author: Stephen William Clark
Publisher:
ISBN: 9780542396274
Category :
Languages : en
Pages : 80
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Colloidal semiconductor quantum dots are novel materials whose electronic and optical properties can be greatly enhanced from the bulk semiconductor properties by quantum confinement. A brief introduction to colloidal quantum dots and the effect of size on its electronic and optical properties will be given. CdSe/ZnS, PbS, and PbSe quantum dots will be described in more detail with regards to the research done in this dissertation. CdSe/ZnS quantum dots have luminescence that can be tuned in the visible, making them particularly suited for fluorescent labels in biological applications. In particular, their potential use as voltage sensors to detect cell membrane potentials and sphingosine phosphorylation will be discussed. PbS and PbSe quantum dots emit in the near infrared, wavelengths that are important to telecommunications. Their small third-order nonlinearity and relatively long (microsecond) lifetimes will be discussed in terms of dielectric screening. Fluoresence resonant energy transfer between PbS quantum dots will also be discussed.
Author: Stanislav I. Sadovnikov
Publisher: Springer
ISBN: 3319563874
Category : Technology & Engineering
Languages : en
Pages : 329
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Book Description
This book presents and analyzes the influence of small size particles of lead, cadmium and silver sulfide on the properties of nonstoichiometric semiconductors. Important nonstoichiometry aspects in nanostructures are discussed, such as the distribution of sulfur atoms in nanofilms, a non-periodic distribution of the atomic planes in nanoparticles, interdependent changes in crystal structure of nanocrystalline material. Tuning the stoichiometry allows to obtain superionic conductivity and catalytic activity under visible light. The wavelength of the luminescence of nanoparticles changes with the size of the nanoparticles. Various methods to prepare nanostructured sulfides are described. Special attention is given to the hydrochemical bath deposition as a universal method for the synthesis of sulfides as nanofilms, stable colloidal solutions, quantum dots, isolated nanoparticles with a protective shell and heteronanostructures. The effect of nanoparticle size and nonstoichiometry on the band gap, optical and thermal properties of nanostructured sulfides is also considered. The novel applications of sulfide nanoparticles in nanoelectronics, catalysis, nanobiology and nanomedicine are sketched.
Author: Aleksandr Ivanovich Gusev
Publisher: Cambridge Int Science Publishing
ISBN: 1898326266
Category : Technology & Engineering
Languages : en
Pages : 365
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In the monograph, the first of this type in the world, the authors discuss systematically the current state of investigations into nanocrystalline materials. The experimental results on the effect of the nanocrystalline state on the microstructure and the mechanical, thermophysical, optical, and magnetic properties of metals, alloys and solid-phase compounds are generalised. Special attention is given to the main methods of production of isolated nanoparticles, ultrafine powders and dense nanocrystalline materials. The dimensional effects in isolated nanoparticles and high-density nanocrystalline materials are discussed in detail, and the important role of the interface in the formation of the structure and properties of dense nanocrystalline materials is shown. The modelling considerations, explaining special features of the structure and anomalous properties of substances in the nanocrystalline condition, are analysed.
