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From Artificial Atoms to Nanocrystal Molecules: Preparation and Properties of More Complex Nanostructures

Description: Quantum dots, which have found widespread use in fields such as biomedicine, photovoltaics, and electronics, are often called artificial atoms due to their size-dependent physical properties. Here this analogy is extended to consider artificial nanocrystal molecules, formed from well-defined groupings of plasmonically or electronically coupled single nanocrystals. Just as a hydrogen molecule has properties distinct from two uncoupled hydrogen atoms, a key feature of nanocrystal molecules is tha… more
Date: October 20, 2009
Creator: Choi, Charina L & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Colloidal nanocrystal synthesis and the organic-inorganicinterface

Description: Colloidal nanocrystals are nanometer-sized, solution-grown inorganic particles stabilized by a layer of surfactants attached to their surface. The inorganic cores exhibit useful properties controlled by composition as well as size and shape, while the surfactant coating ensures that these structures are easy to fabricate and process. It is this combination of features that makes colloidal nanocrystals attractive and promising building blocks for advanced materials and devices. But their full po… more
Date: May 12, 2005
Creator: Yin, Yadong & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Preparation of Asymmetric Nanostructures through Site SelectiveModification of Tetrapods

Description: CdTe tetrapods have been deposited on a substrate and partially coated with a protective polymer layer, exposing just one arm. The exposed arm was then decorated with Au nanoparticles in a site selective fashion. The modified arms were readily broken off from the remainder of the tetrapods and released from the substrate, yielding CdTe nanorods asymmetrically modified with Au nanoparticles. These nanostructures with reduced symmetry may show interesting optoelectronic properties.
Date: September 9, 2004
Creator: Liu, Haitao & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Correlation Analysis of TEM Images of Nanocrystal Molecules

Description: Quantitative characterizataion of images of naocrystals and nanostructures is a challenging but important task. The development and optimization of methods for the construction of complex nanostructures rely on imaging techniques. Computer programs were developed to quantify TEM images of nanocrystal/DNA nanostructures, and results are presented for heterodimers annd trimers of gold nanocrystals. The programs presented here have also been used to analyze more complex trimers and tetramers linke… more
Date: May 21, 2008
Creator: Micheel, Christine; Zanchet, Daniele & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Pyramidal and Chiral Groupings of Gold Nanocrystals Assembled Using DNA Scaffolds

Description: Nanostructures constructed from metal and semiconductor nanocrystals conjugated to, and organized by DNA are an emerging class of material with collective optical properties. We created discrete pyramids of DNA with gold nanocrystals at the tips. By taking small angle X-ray scattering (SAXS) measurments from solutions of these pyramids we confirmed that this pyramidal geometry creates structures which are more rigid in solution than linear DNA. We then took advantage of the tetrahedral symmetry… more
Date: March 30, 2009
Creator: Mastroianni, Alexander; Claridge, Shelley & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Crystal Splitting in the Growth of Bi2S3

Description: Novel Bi{sub 2}S{sub 3} nanostructures with a sheaf-like morphology are obtained via reaction of bismuth acetate-oleic acid complex with elemental sulfur in 1-octadecence. We propose these structures form by the splitting crystal growth mechanism, which is known to account for the morphology some mineral crystals assume in nature. By controlling the synthetic parameters, different forms of splitting, analogous to observed in minerals, are obtained in our case of Bi{sub 2}S{sub 3}. These new and… more
Date: June 15, 2006
Creator: Tang, Jing & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Faceting of Nanocrystals during Chemical Transformation: FromSolid Silver Spheres to Hollow Gold Octahedra

Description: Sustained progress in nanocrystal synthesis has enabled recent use of these materials as inorganic, macromolecular precursors that can be chemically transformed into new nanostructures. The literature now contains several cases with chemical transformations being accompanied by varying degrees of modification of properties, including crystal structure and particle shape. As a recent example, we demonstrated that as-synthesized metallic nanocrystals yield, upon oxidation, nanostructures with mod… more
Date: June 23, 2006
Creator: Yin, Yadong; Erdonmez, Can & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Electrical Contacts to Individual Colloidal Semiconductor Nanorods

Description: We report the results of charge transport studies on single CdTe nanocrystals contacted via evaporated Pd electrodes. Device charging energy, E{sub c}, monitored as a function of electrode separation drops suddenly at separations below {approx}55 nm. This drop can be explained by chemical changes induced by the metal electrodes. This explanation is corroborated by ensemble X-Ray photoelectron spectroscopy (XPS) studies of CdTe films as well as single particle measurements by transmission electr… more
Date: April 1, 2008
Creator: Trudeau, Paul-Emile; Sheldon, Matt; Altoe, Virginia & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Reaction chemistry and ligand exchange at cadmium selenide nanocrystal surfaces

Description: 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-octylpho… more
Date: December 2, 2008
Creator: Owen, Jonathan; Park, Jungwon; Trudeau, Paul-Emile & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Near-Infrared Localized Surface Plasmon Resonances Arising from Free Carriers in Doped Quantum Dots

Description: Quantum confinement of electronic wavefunctions in semiconductor quantum dots (QDs) yields discrete atom-like and tunable electronic levels, thereby allowing the engineering of excitation and emission spectra. Metal nanoparticles, on the other hand, display strong resonant interactions with light from localized surface plasmon resonance (LSPR) oscillations of free carriers, resulting in enhanced and geometrically tunable absorption and scattering resonances. The complementary attributes of thes… more
Date: October 12, 2010
Creator: Jain, Prashant K.; Luther, Joey; Ewers, Trevor & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Independent control of the shape and composition of ionic nanocrystals through sequential cation exchange reactions

Description: Size- and shape-controlled nanocrystal growth is intensely researched for applications including electro-optic, catalytic, and medical devices. Chemical transformations such as cation exchange overcome the limitation of traditional colloidal synthesis, where the nanocrystal shape often reflects the inherent symmetry of the underlying lattice. Here we show that nanocrystals, with established synthetic protocols for high monodispersity, can be templates for independent composition control. Specif… more
Date: July 6, 2009
Creator: Luther, Joseph Matthew; Zheng, Haimei; Sadtler, Bryce & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Hetero-Epitaxial Anion Exchange Yields Single-Crystalline Hollow Nanoparticles

Description: Anion exchange with S was performed on ZnO colloidal nanoparticles. The resulting hollow ZnS nanoparticles are crystal whose shape is dictated by the initial ZnO. Crystallographic and elemental analyses provide insight into the mechanism of the anion exchange.
Date: August 26, 2009
Creator: Park, Jungwon; Zheng, Haimei; Jun, Young-wook & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Nanoheterostructure Cation Exchange: Anionic Framework Conservation

Description: In ionic nanocrystals the cationic sub-lattice can be replaced with a different metal ion via a fast, simple, and reversible place-exchange, allowing post-synthetic modification of the composition of the nanocrystal, while preserving its size and shape. Here, we demonstrate for the first time that during such an exchange, the anionic framework of the crystal is preserved. When applied to nanoheterostructures, this phenomenon ensures that compositional interfaces within the heterostructure are c… more
Date: May 11, 2010
Creator: Jain, Prashant K.; Amirav, Lilac; Aloni, Shaul & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Synthesis and photovoltaic application of coper (I) sulfide nanocrystals

Description: We present the rational synthesis of colloidal copper(I) sulfide nanocrystals and demonstrate their application as an active light absorbing component in combination with CdS nanorods to make a solution-processed solar cell with 1.6percent power conversion efficiency on both conventional glass substrates and flexible plastic substrates with stability over a 4 month testing period.
Date: June 24, 2008
Creator: Wu, Yue; Wadia, Cyrus; Ma, Wanli; Sadtler, Bryce & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Strain-Dependent Photoluminescence Behavior of CdSe/CdS Nanocrystals with Spherical, Linear, and Branched Topologies

Description: The photoluminescence of CdSe/CdS core/shell quantum dots, nanorods, and tetrapods is investigated as a function of applied hydrostatic and non-hydrostatic pressure. The optoelectronic properties of all three nanocrystal morphologies are affected by strain. Furthermore, it is demonstrated that the unique morphology of a tetrapod is highly sensitive to non-isotropic stress environments. Seeded tetrapods can thereby serve as an optical strain gauge, capable of measuring forces on the order of nan… more
Date: August 13, 2009
Creator: Choi, Charina L.; Koski, Kristie J.; Sivasankar, Sanjeevi & Alivisatos, A. Paul
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Controlled Assembly of Hybrid Bulk-Heterojunction Solar Cells bySequential Deposition

Description: This work presents a technique to create ordered and easily characterized hybrid nanocrystal-polymer composites by sequential deposition of tetrapod-shaped cadmium telluride (CdTe) nanocrystals and poly(3-hexlythiophene). With controlled fabrication and composite morphology, these devices offer several advantages over traditional codeposited hybrid cells, and provide a model system for detailed investigation into the operation of bulk-heterojunction cells.
Date: August 13, 2006
Creator: Gur, Ilan; Fromer, Neil A. & Alivisatos, A. Paul
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Partner: UNT Libraries Government Documents Department
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Photovoltaic Devices Employing Ternary PbSxSe1-x Nanocrystals

Description: We report solar cells based on highly confined nanocrystals of the ternary compound PbSxSe1-x. Crystalline, monodisperse alloyed nanocrystals are obtained using a one-pot, hot injection reaction. Rutherford back scattering and energy filtered transmission electron microscopy suggest that the S and Se anions are uniformly distributed in the alloy nanoparticles. Photovoltaic devices made using ternary nanoparticles are more efficient than either pure PbS or pure PbSe based nanocrystal devices.
Date: February 5, 2009
Creator: Ma, Wanli; Luther, Joseph; Zheng, Haimei; Wu, Yue & Alivisatos, A. Paul
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Strain-dependent photoluminescence behavior in three geometries of CdSe/CdS nanocrystals

Description: In recent years, a new generation of quantum confined colloidal semiconductor structures has emerged, with more complex shapes than simple quantum dots1, 2. These include nanorods3 and tetrapods4. Beyond shape, it is also now possible to spatially vary the electron and hole potentials within these nanoparticles by varying the composition. Examples of these new structures include seeded dots, rods, and tetrapods, which contain a CdSe core embedded within a CdS shell5, 6. These structures may hav… more
Date: May 26, 2009
Creator: Choi, Charina L; Koski, Kristie J; Sivasankar, Sanjeevi & Alivisatos, A. Paul
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Optical properties of ZnO/ZnS and ZnO/ZnTe heterostructures forphotovoltaic applications

Description: Although ZnO and ZnS are abundant, stable, environmentallybenign, their band gap energies (3.44 eV, 3.72 eV) are too large foroptimal photovoltaic efficiency. By using band-corrected pseudopotentialdensity-functional theory calculations, we study how the band gap,opticalabsorption, and carrier localization canbe controlled by formingquantum-well like and nanowire-based heterostructures ofZnO/ZnS andZnO/ZnTe. In the case of ZnO/ZnS core/shell nanowires, which can besynthesized using existing met… more
Date: May 1, 2007
Creator: Schrier, Joshua; Demchenko, Denis O.; Wang, Lin-Wang & Alivisatos, A. Paul
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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