Showing papers by "Michael H. Huang published in 2007"

Seed-Mediated Synthesis of Monodispersed Cu2O Nanocubes with Five Different Size Ranges from 40 to 420 nm

Abstract: We report the high yield growth of monodispersed Cu 2 O nanocubes with approximate average sizes of 40, 65, 100, 230, and 420 nm using a seed-mediated synthesis approach in aqueous solution. The nanocubes are formed in 2 hours at room temperature. The standard deviation of the nanocube sizes in each sample is below 10 %. Structural analysis revealed that these nanocubes have six {100} faces, and possess truncated {110} edges and {111} corners. The combination of sodium dodecyl sulfate (SDS) and CuSO 4 was found to be critical to the formation of structurally well-defined Cu 2 O nanocubes. The nanocubes presumably were formed through the controlled aggregation of Cu 2 O seed particles and then surface reconstruction under the influence of SDS capping surfactant and sulfate ions to yield this truncated cubic structure. Optical characterization showed that nanocubes smaller than 100 nm absorb at -490 nm, while nanocubes larger than 200 nm display an absorption band at 515-525 nm. Additional absorption feature was observed in the red and near-infrared regions for the larger Cu 2 O nanocubes due to the light scattering effect. The investigation of the application of these nanocubes for the photodegradation of rhodamine B revealed the {111} crystal surfaces as the active surfaces responsible for the photocatalytic activity of Cu 2 O nanostructures. This simple and rapid synthesis of monodispersed Cu 2 O nanocubes should allow further examination of their various properties as a function of nanocrystal sizes.

Growth of ultralong ZnO nanowires on silicon substrates by vapor transport and their use as recyclable photocatalysts

Abstract: We report the growth of ultralong ZnO nanowires on silicon (100) substrates via the gold-catalyzed vapor transport approach. An ample supply of zinc vapor generated through carbothermal reduction o...

Direct high-yield synthesis of high aspect ratio gold nanorods

Abstract: We report a new development for the direct high-yield synthesis of high aspect ratio gold nanorods. By using a modified seed-mediated synthesis approach for the preparation of high aspect ratio gol...

Investigation of the Growth Process of Gold Nanoplates Formed by Thermal Aqueous Solution Approach and the Synthesis of Ultra-Small Gold Nanoplates

Abstract: The growth process of gold nanoplates formed by a thermal aqueous solution approach was investigated by withdrawing drops of a heated solution containing HAuCl4, cetyltrimethylammonium bromide (CTAB), and trisodium citrate and examined the intermediate products formed by a transmission electron microscopy analysis. The formation process proceeds extremely rapidly within seconds of reaction to form large aggregated structures, which are composed of wormlike structures just several nanometers in diameter. These tiny nanostructures are fused extensively toward the central region to form a thicker mass. The central core grows in size via incorporating the exterior wormlike nanostructures and eventually evolves into the plate morphology. Appropriate amounts of CTAB and trisodium citrate were also found to be critical to the formation of nanoplates. This synthesis approach has been extended to prepare ultrasmall triangular gold nanoplates with average widths of 40 ± 7 and 58 ± 10 nm. Because of their relatively...

Synthesis and Optical Properties of 1-Alkyl-3-Methylimidazolium Lauryl Sulfate Ionic Liquids

Abstract: We report the synthesis of a new series of imidazolium-based halogen-free ionic liquids 1-alkyl-3-methylimidazolium lauryl sulfates. By reacting 1-methylimidazole (MIM) with butyl, hexyl, octyl, and decyl bromides and exchanging bromide ion with lauryl sulfate anion, a series of ionic liquids [RMIM][C12H25OSO3] were produced. The high purity of these ionic liquids was verified with 1H-NMR, 13C-NMR, FT-IR and mass spectrometry (MS), demonstrating the effectiveness of this synthetic approach. Solubility test of these ionic liquids showed that they are soluble in most organic solvents except nonpolar solvents such as hexane and cyclohexane. The optical properties of [BMIM]Br and [BMIM][C12H25OSO3], where B refers to butyl, were examined. Both ionic liquids absorbed light in the UV region, yet essentially no absorption was recorded beyond 450 nm. Furthermore, both ionic liquids showed excitation wavelength-dependent fluorescence behavior. As an example, with an excitation wavelength of 360 nm, [BMIM][C12H25OSO3] showed an emission band maximum at 447 nm. Increasing the excitation wavelength to 440 nm, the emission band maximum was shifted to ∼500 nm.

Spin-Coated Periodic Mesoporous Organosilica Thin Films with Molecular-Scale Order within the Organosilica Wall

Abstract: Periodic mesoporous organosilica (PMO) thin films with long-range molecular order within the organosilica framework have been successfully prepared by spin-coating a solution of 1,4-bis(triethoxysilyl)benzene (BTEB), water, ethanol, HCl, and cetyltrimethylammonium bromide (CTAB) on silicon substrates. Powder XRD patterns of these thin films reveal the presence of a hexagonal phase mesostructure as well as ordered molecular-scale structure. The strong high-angle diffraction peaks indicate the long-range molecular order within the organosilica framework. The degree of organosilica condensation is relatively low, and hydroxyl groups formed in the hydrolysis reaction link the BTEB precursor molecules together in an end-to-end fashion via hydrogen bonding. Infrared spectra of these thin films suggest that the PMO films contain a significant number of hydroxyl groups in a hydrogen bonding environment with a peak at 3200 cm−1. Results from the 29Si magic-angle spinning (MAS) NMR spectroscopy provide additional e...

Eight Tesla Superconducting Solenoid Magnet for the Magnetic Circular Dichroism Study

Abstract: This study describes the design and testing of a superconducting solenoid magnet for soft X-ray magnetic circular dichroism (SXMCD) experiments at the National Synchrotron Radiation Research Center (NSRRC). The superconducting solenoid magnet provides an uniform field of up to 8 T in a bore of 55 mm in diameter and 0.5 m long. The superconducting solenoid is operated in a 4.5-K liquid helium bath for reducing the vibration level during the experiments. The magnet and its cryostat are optimized to prevent magnet quenching and lower liquid helium consumption. The magnet quench test and magnetic field measurements are also performed.