The Experts below are selected from a list of 6291 Experts worldwide ranked by ideXlab platform
Samy M Elshall - One of the best experts on this subject based on the ideXlab platform.
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Vapor Phase Synthesis of upconverting y 2o 3 nanocrystals doped with yb 3 er 3 ho 3 and tm 3 to generate red green blue and white light
Journal of Physical Chemistry C, 2008Co-Authors: Garry Glaspell, John E Anderson, James R Wilkins, Samy M ElshallAbstract:We report the Vapor Phase Synthesis of upconverting Y 2O 3 nanocrystals doped with Yb 3+, Er 3+, Ho 3+, and Tm 3+ to generate red, green, blue, and white light. Incorporating Er 3+ within the Yb 3+ doped Y 2O 3 nanocrystals under 980 nm laser excitation produced orange and yellow upconversion luminescence tunable by varying the Yb 3+ concentration. The Yb 3+, Er 3+, and Tm 3+ codoped Y 2O 3 nanocrystals exhibited nearly equal intensities of the red, green, and blue emissions upon 980 nm laser excitation. White light can be produced by adjusting the concentrations of the Ln 3+ ions within the Y 2O 3 nanocrystals.
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Vapor Phase Synthesis of supported pd au and unsupported bimetallic nanoparticle catalysts for co oxidation
Catalysis Communications, 2006Co-Authors: Yonglai Yang, Victor Abdelsayed, Sarojini Deevi, Khaled Saoud, Garry Glaspell, Samy M ElshallAbstract:We report the Vapor Phase Synthesis and characterization of supported Pd, Au and unsupported bimetallic nanoparticle catalysts for CO oxidation. The approach utilized in the present work is based on the laser Vaporization/controlled condensation technique which uniquely combines the features of pulsed laser Vaporization with the controlled condensation process from the Vapor Phase to synthesize nanoparticle catalysts of controlled size and composition. The results indicate that supported Pd/CeO2, Au/CeO2, and unsupported bimetallic CuPd, CuAu, and AuPd nanoparticle catalysts exhibit excellent activity for CO oxidation. The significance of the current method lies mainly in its simplicity, flexibility and the control of the different factors that determine the activity of the nanoparticle catalysts.
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Vapor Phase Synthesis and characterization of bimetallic alloy and supported nanoparticle catalysts
Journal of Nanoparticle Research, 2006Co-Authors: Victor Abdelsayed, Khaled Saoud, Samy M ElshallAbstract:The laser Vaporization controlled condensation (LVCC) technique coupled with a differential mobility analyzer (DMA) is used to synthesize size-selected alloy nanoparticles and nanoparticle catalyst systems. The formation of Au–Ag alloy nanoparticles is concluded from the observation of only one plasmon band. The maximum of the plasmon absorption is found to vary linearly with the gold mole fraction. For the Au–Pd system, the XRD data confirms the formation of the alloy nanoparticles with no evidence of any of the pure components. The Au/CeO2 nanoparticle catalyst prepared by the LVCC method is a promising catalyst for low temperature CO oxidation due to its high activity and stability.
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Vapor Phase Synthesis of metallic and intermetallic nanoparticles and nanowires magnetic and catalytic properties
Pure and Applied Chemistry, 2006Co-Authors: Garry Glaspell, Victor Abdelsayed, Khaled Saoud, Samy M ElshallAbstract:In this paper, we present several examples of the Vapor-Phase Synthesis of inter- metallic and alloy nanoparticles and nanowires, and investigate their magnetic and catalytic properties. In the first example, we report the Vapor-Phase Synthesis of intermetallic alu- minide nanoparticles. Specifically, FeAl and NiAl nanoparticles were synthesized via laser Vaporization controlled condensation (LVCC) from their bulk powders. The NiAl nanoparti- cles were found to be paramagnetic at room temperature, with a blocking temperature of ap- proximately 15 K. The FeAl nanoparticles displayed room-temperature ferromagnetism. In the second example, we report the Vapor-Phase Synthesis of cobalt oxide nanoparticle cata- lysts for low-temperature CO oxidation. The incorporation of Au and Pd nanoparticles into the cobalt oxide support leads to significantly improved catalytic activity and stability of the binary catalyst systems. Finally, we report the Synthesis of nanowires of Ge, Mg, Pd, and Pt using the Vapor-liquid-solid (VLS) method where the Vapor-Phase growth of the wire is cat- alyzed using a proper metal catalyst present in the liquid Phase.
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nanoparticles from the Vapor Phase Synthesis and characterization of si ge moo3 and wo3nanocrystals
Journal of Cluster Science, 1999Co-Authors: I N Germanenko, Samy M ElshallAbstract:In this paper, we present two studies of nanocrystals prepared by the pulsed laser Vaporization–controlled condensation (LVCC) technique. In the first study, we present a comparison between the surface oxidation, morphology and the photoluminescence (PL) properties of Si and Ge nanocrystals. In the second study, we compare the photochromic properties of Mo and W oxides nanoparticles with the properties of the corresponding bulk materials. We also present evidence for a novel photoreduction of the white WO3 nanoparticles into the blue W2O5 following the irradiation of the particles with the second harmonic of the Nd:YAG laser in air. These studies illustrate the novel properties of the nanoscale particles, which could lead to significant practical and technological applications.
Xinfeng Liu - One of the best experts on this subject based on the ideXlab platform.
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one step Vapor Phase Synthesis and quantum confined exciton in single crystal platelets of hybrid halide perovskites
Journal of Physical Chemistry Letters, 2019Co-Authors: Zhixiong Liu, Qihua Xiong, Xinwei Guan, Ming-hui Chiu, Moh R. Amer, Abdulrahman Alhussain, Jie Liu, Jinlan Wang, Xinfeng LiuAbstract:To investigate the quantum confinement effect on excitons in hybrid perovskites, single-crystal platelets of CH3NH3PbBr3 are grown on mica substrates using one-step chemical Vapor deposition. Photoluminescence measurements reveal a monotonous blue shift with a decreasing platelet thickness, which is accompanied by a significant increase in exciton binding energy from approximately 70 to 150 meV. Those phenomena can be attributed to the one-dimensional (1D) quantum confinement effect in the two-dimensional platelets. Furthermore, we develop an analytical model to quantitatively elucidate the 1D confinement effect in such quantum wells with asymmetric barriers. Our analysis indicates that the exciton Bohr radius of single-crystal CH3NH3PbBr3 is compressed from 4.0 nm for the thick (26.2 nm) platelets to 2.2 nm for the thin (5.9 nm) ones. The critical understanding of the 1D quantum confinement effect and the development of a general model to elucidate the exciton properties of asymmetric semiconductor quantum wells pave the way toward developing high-performance optoelectronic heterostructures.
Sebastian V R Mastrangelo - One of the best experts on this subject based on the ideXlab platform.
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Vapor Phase Synthesis of al doped titania powders
Journal of Materials Research, 1994Co-Authors: Kamal M Akhtar, Sotiris E Pratsinis, Sebastian V R MastrangeloAbstract:The role of aluminum as dopant in gas Phase Synthesis of titania powders was experimentally investigated in an aerosol flow reactor between 1300 and 1700 K. Titania was produced by Vapor Phase oxidation of titanium tetrachloride in the presence of dopant aluminum trichloride Vapor. The presence of aluminum altered the particle morphology from polyhedral to irregular crystals. Energy dispersive analysis and transmission electron microscopy indicated that the powders were mixtures of crystalline titania and amorphous alumina. Analysis by XPS indicated significant enrichment of aluminum on the particle surface. Some aluminum titanate (up to 17% by volume) was formed at 1700 K when a high concentration of AlCl3 was used (AlCl3/TiCl4 ≥ 0.07). Measurements of lattice parameters by x-ray diffraction indicated that aluminum formed a solid solution in titania. While titania synthesized in the absence of aluminum was about 90% anatase, the introduction of aluminum resulted in pure rutile at AlCl3/TiCl4 = 0.07. The effects of aluminum on titania Phase composition and morphology are explained by the creation of oxygen vacancies in the titania crystallites and by the enhancement of the sintring rate of titania grains.
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dopants in Vapor Phase Synthesis of titania powders
Journal of the American Ceramic Society, 1992Co-Authors: Kamal M Akhtar, Sotiris E Pratsinis, Sebastian V R MastrangeloAbstract:Gas-Phase Synthesis of titania by TiCl4 oxidation in the presence of dopants (SiCl4, POCl3, and BCl3) was investigated in an aerosol reactor as a function of temperature (1300–1700 K) and dopant concentration (0–25 mol% of TiCl4). The addition of dopants, most notably silicon and phosphorus, drastically altered the morphology of titania particles from polyhedral to spheroidal, increased the extent of aggregation, increased the specific surface area, reduced the primary particle size, and decreased the rutile content. The observed morphology/crystallinity changes were explained in terms of ionic radii and valence of the dopant element.
Zhixiong Liu - One of the best experts on this subject based on the ideXlab platform.
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one step Vapor Phase Synthesis and quantum confined exciton in single crystal platelets of hybrid halide perovskites
Journal of Physical Chemistry Letters, 2019Co-Authors: Zhixiong Liu, Qihua Xiong, Xinwei Guan, Ming-hui Chiu, Moh R. Amer, Abdulrahman Alhussain, Jie Liu, Jinlan Wang, Xinfeng LiuAbstract:To investigate the quantum confinement effect on excitons in hybrid perovskites, single-crystal platelets of CH3NH3PbBr3 are grown on mica substrates using one-step chemical Vapor deposition. Photoluminescence measurements reveal a monotonous blue shift with a decreasing platelet thickness, which is accompanied by a significant increase in exciton binding energy from approximately 70 to 150 meV. Those phenomena can be attributed to the one-dimensional (1D) quantum confinement effect in the two-dimensional platelets. Furthermore, we develop an analytical model to quantitatively elucidate the 1D confinement effect in such quantum wells with asymmetric barriers. Our analysis indicates that the exciton Bohr radius of single-crystal CH3NH3PbBr3 is compressed from 4.0 nm for the thick (26.2 nm) platelets to 2.2 nm for the thin (5.9 nm) ones. The critical understanding of the 1D quantum confinement effect and the development of a general model to elucidate the exciton properties of asymmetric semiconductor quantum wells pave the way toward developing high-performance optoelectronic heterostructures.
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One-Step Vapor-Phase Synthesis and Quantum-Confined Exciton in Single-Crystal Platelets of Hybrid Halide Perovskites
2019Co-Authors: Zhixiong Liu, Xinwei Guan, Abdulrahman Al-hussain, Ming-hui Chiu, Moh R. AmerAbstract:To investigate the quantum confinement effect on excitons in hybrid perovskites, single-crystal platelets of CH3NH3PbBr3 are grown on mica substrates using one-step chemical Vapor deposition. Photoluminescence measurements reveal a monotonous blue shift with a decreasing platelet thickness, which is accompanied by a significant increase in exciton binding energy from approximately 70 to 150 meV. Those phenomena can be attributed to the one-dimensional (1D) quantum confinement effect in the two-dimensional platelets. Furthermore, we develop an analytical model to quantitatively elucidate the 1D confinement effect in such quantum wells with asymmetric barriers. Our analysis indicates that the exciton Bohr radius of single-crystal CH3NH3PbBr3 is compressed from 4.0 nm for the thick (26.2 nm) platelets to 2.2 nm for the thin (5.9 nm) ones. The critical understanding of the 1D quantum confinement effect and the development of a general model to elucidate the exciton properties of asymmetric semiconductor quantum wells pave the way toward developing high-performance optoelectronic heterostructures
Qihua Xiong - One of the best experts on this subject based on the ideXlab platform.
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one step Vapor Phase Synthesis and quantum confined exciton in single crystal platelets of hybrid halide perovskites
Journal of Physical Chemistry Letters, 2019Co-Authors: Zhixiong Liu, Qihua Xiong, Xinwei Guan, Ming-hui Chiu, Moh R. Amer, Abdulrahman Alhussain, Jie Liu, Jinlan Wang, Xinfeng LiuAbstract:To investigate the quantum confinement effect on excitons in hybrid perovskites, single-crystal platelets of CH3NH3PbBr3 are grown on mica substrates using one-step chemical Vapor deposition. Photoluminescence measurements reveal a monotonous blue shift with a decreasing platelet thickness, which is accompanied by a significant increase in exciton binding energy from approximately 70 to 150 meV. Those phenomena can be attributed to the one-dimensional (1D) quantum confinement effect in the two-dimensional platelets. Furthermore, we develop an analytical model to quantitatively elucidate the 1D confinement effect in such quantum wells with asymmetric barriers. Our analysis indicates that the exciton Bohr radius of single-crystal CH3NH3PbBr3 is compressed from 4.0 nm for the thick (26.2 nm) platelets to 2.2 nm for the thin (5.9 nm) ones. The critical understanding of the 1D quantum confinement effect and the development of a general model to elucidate the exciton properties of asymmetric semiconductor quantum wells pave the way toward developing high-performance optoelectronic heterostructures.
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Vapor Phase Synthesis of organometal halide perovskite nanowires for tunable room temperature nanolasers
Nano Letters, 2015Co-Authors: Jun Xing, Qing Zhang, Son Tung Ha, Yan Wen Yuan, Chao Shen, Qihua XiongAbstract:Semiconductor nanowires have received considerable attention in the past decade driven by both unprecedented physics derived from the quantum size effect and strong isotropy and advanced applications as potential building blocks for nanoscale electronics and optoelectronic devices. Recently, organic–inorganic hybrid perovskites have been shown to exhibit high optical absorption coefficient, optimal direct band gap, and long electron/hole diffusion lengths, leading to high-performance photovoltaic devices. Herein, we present the Vapor Phase Synthesis free-standing CH3NH3PbI3, CH3NH3PbBr3, and CH3NH3PbIxCl3–x perovskite nanowires with high crystallinity. These rectangular cross-sectional perovskite nanowires have good optical properties and long electron hole diffusion length, which ensure adequate gain and efficient optical feedback. Indeed, we have demonstrated optical-pumped room-temperature CH3NH3PbI3 nanowire lasers with near-infrared wavelength of 777 nm, low threshold of 11 μJ/cm2, and a quality fact...
