A Computational Investigation Of Zinc Selenide And Cadmium Selenide Nanocrystallite Surface Effects Using A Tight Binding Technique

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A Computational Investigation of Zinc Selenide and Cadmium Selenide Nanocrystallite Surface Effects Using a Tight-binding Technique

Author : Jordan Ang
Publisher :
ISBN 13 : 9780494400708
Total Pages : 292 pages
Book Rating : 4.4/5 (7 download)

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Book Synopsis A Computational Investigation of Zinc Selenide and Cadmium Selenide Nanocrystallite Surface Effects Using a Tight-binding Technique by : Jordan Ang

Download or read book A Computational Investigation of Zinc Selenide and Cadmium Selenide Nanocrystallite Surface Effects Using a Tight-binding Technique written by Jordan Ang and published by . This book was released on 2007 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work is a theoretical investigation of surface effects on the electronic and optical properties of quantum dots. Computations are done using the atomistic Empirical Tight-Binding method based on a nearest-neighbour approximation. Surface effects are "turned off" or "turned on" by respectively passivating surface dangling bonds or allowing them to hang freely. Considered are passivated and unpassivated ZnS and CdS; mixed ZnCdS alloy; and core/shell ZnS/CdS and CdS/ZnS semiconductor nanocrystallites, all at various sizes ranging between & sim;13--46 A in diameter. The computational results show that passivated crystallites yield clean bandgaps that increase in size as crystallite size decreases, causing a monotonic blue shift in the position of the corresponding absorption onset. When the surface is left unpassivated, surface states populate energies in and around the fundamental bandgap. Their locations, however, are not size dependant and consequently the corresponding optical spectra are also devoid of monotonic size dependencies.

Investigation of Trapping Phenomena in Zinc Selenide and Cadmium Sulfide Using Photo-Hall Techniques

Author : Alan Carl Naisuler
Publisher :
ISBN 13 :
Total Pages : 346 pages
Book Rating : 4.:/5 (19 download)

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Book Synopsis Investigation of Trapping Phenomena in Zinc Selenide and Cadmium Sulfide Using Photo-Hall Techniques by : Alan Carl Naisuler

Download or read book Investigation of Trapping Phenomena in Zinc Selenide and Cadmium Sulfide Using Photo-Hall Techniques written by Alan Carl Naisuler and published by . This book was released on 1974 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Exciton Dynamics in Cadmiun Selenide/zinc Selenide Core/core-shell Nanocrystals as Effected by Surface Ligand Modification Using Femtosecond Fluorescence Upconversion

Download Exciton Dynamics in Cadmiun Selenide/zinc Selenide Core/core-shell Nanocrystals as Effected by Surface Ligand Modification Using Femtosecond Fluorescence Upconversion PDF Online Free

Author : Tadd Kippeny
Publisher :
ISBN 13 :
Total Pages : 204 pages
Book Rating : 4.:/5 (622 download)

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Book Synopsis Exciton Dynamics in Cadmiun Selenide/zinc Selenide Core/core-shell Nanocrystals as Effected by Surface Ligand Modification Using Femtosecond Fluorescence Upconversion by : Tadd Kippeny

Download or read book Exciton Dynamics in Cadmiun Selenide/zinc Selenide Core/core-shell Nanocrystals as Effected by Surface Ligand Modification Using Femtosecond Fluorescence Upconversion written by Tadd Kippeny and published by . This book was released on 2005 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Chemical Abstracts

Author :
Publisher :
ISBN 13 :
Total Pages : 2566 pages
Book Rating : 4.3/5 (91 download)

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Book Synopsis Chemical Abstracts by :

Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2566 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Anisotropic Surface Effects on Cadmium Selenide

Author : Rucelle L. Consigny
Publisher :
ISBN 13 :
Total Pages : 125 pages
Book Rating : 4.:/5 (114 download)

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Book Synopsis Anisotropic Surface Effects on Cadmium Selenide by : Rucelle L. Consigny

Download or read book Anisotropic Surface Effects on Cadmium Selenide written by Rucelle L. Consigny and published by . This book was released on 1969 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Reaction Chemistry and Ligand Exchange at Cadmium Selenide Nanocrystal Surfaces

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (727 download)

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Book Synopsis Reaction Chemistry and Ligand Exchange at Cadmium Selenide Nanocrystal Surfaces by :

Download or read book Reaction Chemistry and Ligand Exchange at Cadmium Selenide Nanocrystal Surfaces written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Chemical modification of nanocrystal surfaces is fundamentally important to their assembly, their implementation in biology and medicine, and greatly impacts their electrical and optical properties. However, it remains a major challenge owing to a lack of analytical tools to directly determine nanoparticle surface structure. Early nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) studies of CdSe nanocrystals prepared in tri-n-octylphosphine oxide (1) and tri-n-octylphosphine (2), suggested these coordinating solvents are datively bound to the particle surface. However, assigning the broad NMR resonances of surface-bound ligands is complicated by significant concentrations of phosphorus-containing impurities in commercial sources of 1, and XPS provides only limited information about the nature of the phosphorus containing molecules in the sample. More recent reports have shown the surface ligands of CdSe nanocrystals prepared in technical grade 1, and in the presence of alkylphosphonic acids, include phosphonic and phosphinic acids. These studies do not, however, distinguish whether these ligands are bound datively, as neutral, L-type ligands, or by X-type interaction of an anionic phosphonate/phosphinate moiety with a surface Cd{sup 2+} ion. Answering this question would help clarify why ligand exchange with such particles does not proceed generally as expected based on a L-type ligand model. By using reagents with reactive silicon-chalcogen and silicon-chlorine bonds to cleave the ligands from the nanocrystal surface, we show that our CdSe and CdSe/ZnS core-shell nanocrystal surfaces are likely terminated by X-type binding of alkylphosphonate ligands to a layer of Cd{sup 2+}/Zn{sup 2+} ions, rather than by dative interactions. Further, we provide spectroscopic evidence that 1 and 2 are not coordinated to our purified nanocrystals.

An Investigation Into Chemical-mechanical Polishing Process of Zinc Selenide

Author : Hongyu Yao
Publisher :
ISBN 13 :
Total Pages : 174 pages
Book Rating : 4.:/5 (89 download)

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Book Synopsis An Investigation Into Chemical-mechanical Polishing Process of Zinc Selenide by : Hongyu Yao

Download or read book An Investigation Into Chemical-mechanical Polishing Process of Zinc Selenide written by Hongyu Yao and published by . This book was released on 2001 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:

PHOTOCATALYTIC PROPERTIES OF ZINC SELENIDE/CADMIUM SULFIDE CORE-SHELL NANOPARTICLES

Author : Jayalath Pathirannehelage Dimuthu Nuwan Perera
Publisher :
ISBN 13 :
Total Pages : 35 pages
Book Rating : 4.:/5 (879 download)

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Book Synopsis PHOTOCATALYTIC PROPERTIES OF ZINC SELENIDE/CADMIUM SULFIDE CORE-SHELL NANOPARTICLES by : Jayalath Pathirannehelage Dimuthu Nuwan Perera

Download or read book PHOTOCATALYTIC PROPERTIES OF ZINC SELENIDE/CADMIUM SULFIDE CORE-SHELL NANOPARTICLES written by Jayalath Pathirannehelage Dimuthu Nuwan Perera and published by . This book was released on 2013 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study investigates the photocatalytic activity of ZnSe/CdS core/shell semiconductor nanocrystals. These nanoparticles exhibit a spatial separation of photoinduced charges between the core and the shell domains, which makes them potentially viable for photocatalytic applications. Unfortunately, one of the excited charges remains inside the core semiconductor and thus cannot efficiently react with the external environment. Here, we explore this issue by investigating the mechanisms of hole extraction from the ZnSe core to the surface of the CdS shell. In particular, the effect of shell thickness in ZnSe/CdS core/shell nanocrystals on the ability of core-localized charges to perform oxidative reactions was determined. By using a combination of time-resolved spectroscopy and electrochemical techniques, we demonstrate that the use of holescavenging surfactants facilitates an efficient transfer of core-localized holes to the surface even in the case of shells exceeding 7 nm in thickness. These measurements further demonstrate that photoinduced holes can be extracted from the core faster than they recombine with shell-localized electrons, indicating that most of the absorbed energy in ZnSe/CdS nanocrystals can be used to drive catalytic reactions.

Synthesis and Characterization Cadmium Selenide and Zinc Selenide Nanoparticles

Author : Nkosinathi N. Dlamini
Publisher :
ISBN 13 :
Total Pages : 196 pages
Book Rating : 4.:/5 (873 download)

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Book Synopsis Synthesis and Characterization Cadmium Selenide and Zinc Selenide Nanoparticles by : Nkosinathi N. Dlamini

Download or read book Synthesis and Characterization Cadmium Selenide and Zinc Selenide Nanoparticles written by Nkosinathi N. Dlamini and published by . This book was released on 2012 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:

An Investigation of Cadmium Selenide Photoluminescence as a Chemical Sensing Method for Group V Hydrides and Group III Metal Trialkyls

Download An Investigation of Cadmium Selenide Photoluminescence as a Chemical Sensing Method for Group V Hydrides and Group III Metal Trialkyls PDF Online Free

Author : Edmund Jacques Winder
Publisher :
ISBN 13 :
Total Pages : 318 pages
Book Rating : 4.:/5 (89 download)

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Book Synopsis An Investigation of Cadmium Selenide Photoluminescence as a Chemical Sensing Method for Group V Hydrides and Group III Metal Trialkyls by : Edmund Jacques Winder

Download or read book An Investigation of Cadmium Selenide Photoluminescence as a Chemical Sensing Method for Group V Hydrides and Group III Metal Trialkyls written by Edmund Jacques Winder and published by . This book was released on 1997 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Facile Surface Exchange on 2D Cadmium Selenide Quantum Belts

Author : Yuewei Yao
Publisher :
ISBN 13 :
Total Pages : 143 pages
Book Rating : 4.:/5 (119 download)

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Book Synopsis Facile Surface Exchange on 2D Cadmium Selenide Quantum Belts by : Yuewei Yao

Download or read book Facile Surface Exchange on 2D Cadmium Selenide Quantum Belts written by Yuewei Yao and published by . This book was released on 2020 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents various surface-ligand exchange reactions on cadmium selenide quantum belts (QBs), specifically between L-type, Z-type and bound-ion-pair AX salt type ligation. The surface ligation of nanocrystals determines their optical and transport properties, and thus purposeful control of nanocrystal surface chemistry is under active investigation. Colloidal 2D II-VI (specifically CdSe) QBs provide an ideal system for the study of rapid, complete, and reversible surface exchange at room temperature. Interchange of different types of ligands is observed. The surface exchanges are characterized by a variety of means, and the absorption and emission spectra of the QBs are extremely sensitive to surface ligation. We demonstrate that L-type ligands are rapidly, reversibly, and completely exchanged by Z-type metal halide ligands. Amine-ligated {CdSe[n-octylamine]0. 53±0. 06} QBs undergo instantaneous, reversible exchange of the L-type amine ligation for Z-type ligation provided by the neutral metal halides MX2 (M= Cd, Zn; X= Cl, Br, I). Exchange from L-type to Z-type MX2 ligation results in large shifts of the quantum-belt absorption features to lower energy, which are 252, 151, and 157 meV for CdCl2, CdBr2, and CdI2 ligation, respectively. These reversible exchanges demonstrate the strong influence of surface ligation on the electronic properties of the 2D nanocrystals. We also demonstrate that Z-type ligation of CdSe QBs is exchangeable by bound-ion-pair X-type ligation. Simple salts AX (A= NR4+ or Na+) displace Z-type ligation to give bound-ion-pair X-type ligation. These exchange reactions are also rapid, complete, and fully reversible. The approach used here may shed light on a broad technological adaption of solution-processed metals, dielectrics, and semiconductors. Finally, we differentiate thiol and thiolate ligands on CdSe QBs. We identify various bonding modes and conclude that thiol and thiolate ligands are readily exchangeable on CdSe QBs.

Fundamental Studies of the Adsorption of Cadmium Selenide Quantum Dots to Surfactant-Functionalized Titania Films

Author : Scott Martin
Publisher :
ISBN 13 :
Total Pages : 66 pages
Book Rating : 4.:/5 (611 download)

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Book Synopsis Fundamental Studies of the Adsorption of Cadmium Selenide Quantum Dots to Surfactant-Functionalized Titania Films by : Scott Martin

Download or read book Fundamental Studies of the Adsorption of Cadmium Selenide Quantum Dots to Surfactant-Functionalized Titania Films written by Scott Martin and published by . This book was released on 2009 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our research group studies the adsorption of semiconductor quantum dots to self-assembled monolayers on metal oxide films and the interfacial electron transfer reactivity of these materials. This thesis will focus on understanding how the properties of the monolayer-functionalized titanium oxide (TiO2) film and the cadmium selenide (CdSe) quantum dots themselves affect the saturation surface coverages of these quantum dots. We performed equilibrium binding experiments to characterize the adsorption of mercaptoalkanoic acids (MAAs) onto nanocrystalline TiO2 films and CdSe onto these functionalized films. As the chain length of the MAAs increased, the maximum surface coverage of MAAs on TiO2 remained constant at 10-8 mol/cm2, and the surface adduct formation constant remained constant at around 104 M-1. However, the surface coverages of TOPO-capped CdSe on MAA-functionalized TiO2 films, varied with the MAA chain length. The longer chained MAAs showed a surface coverage of 10-6 mol/cm2 while those of chain lengths of 8 carbons or less showed a surface coverage an order of magnitude lower. We believe that the structure of the CdSe capping agent might play a role in this trend where the alkyl chain length of MAA must be equal to or greater than the capping agent for significant coverage of the CdSe. Further experiments using other capping agents such as amines bore out this affinity of quantum dots for surfactant-functionalized TiO2 films.

Transient Absorption and Raman Spectroscopy of Cadmium Selenide/Zinc Selenide Core/shell Alloy Particles

Author :
Publisher :
ISBN 13 :
Total Pages : 70 pages
Book Rating : 4.:/5 (881 download)

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Book Synopsis Transient Absorption and Raman Spectroscopy of Cadmium Selenide/Zinc Selenide Core/shell Alloy Particles by :

Download or read book Transient Absorption and Raman Spectroscopy of Cadmium Selenide/Zinc Selenide Core/shell Alloy Particles written by and published by . This book was released on 2004 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: The central premise of this thesis surrounds the effects of smoothing out the interface between core and shell of a nanoparticle system on the multi-exciton auger recombination kinetics as measured by transient absorption spectroscopy. Current research suggests smoothing out the interface between core and shell by alloying at high temperature reduces the auger rate [1], the rate at which multiexcitons combine down to a single exciton, and therefore increases the viability of the system for solar energy devices incorporating multiple exciton generation (MEG) technology. Auger recombination is so detrimental to these technologies because it occurs on a timescale of picoseconds, whereas radiative recombination, the primary mechanism for capturing energy in a nanoparticle and reemitting it, occurs on the nanosecond timescale. If multiexcitons were to be created in a nanocrystal sample with no means of controlling auger recombination, the auger mechanism would reduce these excitons down to one, and subsequent cooling of the hot carrier by phonon release would result in the loss of all of the extra energy that was stored in these excitons. In order to study this phenomenon multiple experimental techniques were performed on the nanoparticle samples, most notably UV-Vis, static fluorescence, Raman and transient absorption spectroscopies. As a result of this research, it is clear that alloying a core/shell particle has little effect on transient absorption kinetics, and that current theory on the subject needs to be reformulated. The experimental data contained herein is compared with calculations using a FORTRAN program developed by Professor David. F. Kelley, and confirms the process of alloying has little to no effect on auger rates of nanoparticles for this system. The calculations were also able to reproduce the UV-Vis and Raman spectra almost quantitatively if given the correct parameters, increasing confidence in the interpretation of the experimental results. This thesis does not aim to discuss what exactly controls the auger rate in nanoparticle systems, but a few conjectures based on sound observation and rooted in solid theory are presented.

Computational Studies of Reacting Flows with Applications to Zinc Selenide Nanoparticle Synthesis & Methane/hydrogen Separation

Author : Maria Koutsona
Publisher :
ISBN 13 :
Total Pages : 434 pages
Book Rating : 4.:/5 (515 download)

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Book Synopsis Computational Studies of Reacting Flows with Applications to Zinc Selenide Nanoparticle Synthesis & Methane/hydrogen Separation by : Maria Koutsona

Download or read book Computational Studies of Reacting Flows with Applications to Zinc Selenide Nanoparticle Synthesis & Methane/hydrogen Separation written by Maria Koutsona and published by . This book was released on 2002 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt:

EPR Studies of Electron Transfer in Cadmium Selenide Sensitised Titania

Author : Eva-Panduleni Beukes Stewart
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)

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Book Synopsis EPR Studies of Electron Transfer in Cadmium Selenide Sensitised Titania by : Eva-Panduleni Beukes Stewart

Download or read book EPR Studies of Electron Transfer in Cadmium Selenide Sensitised Titania written by Eva-Panduleni Beukes Stewart and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Semiconductor Nanocrystals

Author : Alexander L. Efros
Publisher : Springer Science & Business Media
ISBN 13 : 1475736770
Total Pages : 277 pages
Book Rating : 4.4/5 (757 download)

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Book Synopsis Semiconductor Nanocrystals by : Alexander L. Efros

Download or read book Semiconductor Nanocrystals written by Alexander L. Efros and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: A physics book that covers the optical properties of quantum-confined semiconductor nanostructures from both the theoretical and experimental points of view together with technological applications. Topics to be reviewed include quantum confinement effects in semiconductors, optical adsorption and emission properties of group IV, III-V, II-VI semiconductors, deep-etched and self assembled quantum dots, nanoclusters, and laser applications in optoelectronics.

Nanocrystals

Author : Sudheer Neralla
Publisher : BoD – Books on Demand
ISBN 13 : 9535107143
Total Pages : 214 pages
Book Rating : 4.5/5 (351 download)

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Book Synopsis Nanocrystals by : Sudheer Neralla

Download or read book Nanocrystals written by Sudheer Neralla and published by BoD – Books on Demand. This book was released on 2012-08-29 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystals research has been an area of significant interest lately, due to the wide variety of potential applications in semiconductor, optical and biomedical fields. This book consists of a collection of research work on nanocrystals processing and characterization of their structural, optical, electronic, magnetic and mechanical properties. Various methods for nanocrystals synthesis are discussed in the book. Size-dependent properties such as quantum confinement, superparamagnetism have been observed in semiconductor and magnetic nanoparticles. Nanocrystals incorporated into different material systems have proven to possess improved properties. A review of the exciting outcomes nanoparticles study has provided indicates further accomplishments in the near future.