Solution-phase synthesis and high photocatalytic activity of wurtzite ZnSe ultrathin nanobelts: a general route to 1D semiconductor nanostructured materials.
ABSTRACT A general and facile synthetic route has been developed to prepare 1D semiconductor nanomaterials in a binary solution of distilled water and ethanol amine. The influence of the volume ratio of mixed solvents and reaction temperature on the yield and final morphology of products was investigated. Significantly, this is the first time that wurtzite ZnSe ultrathin nanobelts have been synthesized in solution. It has been confirmed that the photocatalytic activity of ZnSe nanobelts in the photodegradation of the fuchsine acid is higher than that of TiO(2) nanoparticles. The present work shows that the solvothermal route is facile, cheap, and versatile. Thus, it is very easy to realize scaled-up production, and brings new light on the synthesis and self-assembly of functional materials.
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ABSTRACT: The photocatalyticH2Osplitting activities of CdSe and CdSe/CdS core/shell quantum dots are contrasted. CdSe/CdS core/shell quantum dots constructed from 4.0 nm CdSe quantum dots are shown to be strongly active for visible-light-driven photocatalyticH2 evolution in 0.1MNa2S/Na2SO3 solution with a turnover number of 9.94 after 5 h at 103.9 μmol/h. CdSe quantum dots themselves are only marginally active in 0.1 M Na2S/Na2SO3 solution with a turnover number of 1.10 after 5 h at 11.53 μmol/h, while CdSe quantum dots in pure H2O are found to be completely inactive. Broad-band transient absorption spectroscopy is used to elucidate the mechanisms that facilitate the enhancement in the CdSe core/shell quantum dots, which is attributed to passivation of surface-deep trap states with energies lying below the reduction potential necessary for H2O reduction. Thus, surface trapping dynamics and energetics can be manipulated to dictate the photocatalytic activities of novel CdSe quantum dot based photocatalytic materials.Journal of Physical Chemistry Letters 10/2011; 2(10.1021/jz2013193):2688-2694. · 6.59 Impact Factor
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ABSTRACT: CdSe nanospheres and dendrites have been successfully synthesized via an ionic liquid-assisted hydrothermal synthetic method. The samples are characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Our experimental results demonstrate that the CdSe dendrites are obtained by self-assembly from nanospheres under the driving force of oriented attachment process. Moreover, we found that the sizes and morphologies of the crystals depended on the concentration of the ionic liquid, and we obtained the CdSe nanospheres with low concentration of [BMIm][SeO(2)(OCH(3))] and CdSe dendrites with high concentration of [BMIm][SeO(2)(OCH(3))]. The effects of [BMIm][SeO(2)(OCH(3))] on the formation of the CdSe have been investigated systematically. This method is expected to be a useful technique to prepare other metal selenides for controlling the diverse shapes and sizes.Dalton Transactions 03/2011; 40(9):1924-8. · 3.81 Impact Factor
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ABSTRACT: The primary photodynamics of water-solubilized 2D CdSe nanoribbons (NRs) was characterized with femtosecond transient absorption spectroscopy and modeled using global analysis. The measured signals were decomposed into the constituent dynamics of three transient populations: hot tightly bound excitons, relaxed tightly bound excitons, and separated trapped carriers (holes and electrons). The influences of three external factors affecting the observed dynamics were explored: (1) excitation wavelength, (2) excitation fluence, and (3) presence of the hole scavenger HS–. Both higher-energy excitation photons and higher-intensity excitation induce slower relaxation of charge carriers to the band edge due to the need to dissipate excess excitation energy. Nonlinear decay kinetics of the relaxed exciton population is observed and demonstrated to arise from bimolecular trapping of excitons with low-density trap sites located at CdSe NR surface sites instead of the commonly resolved multiparticle Auger recombination mechanism. This is supported by the observed linear excitation-fluence dependence of the trapped-carrier population that is numerically simulated and found to deviate from the excitation fluence dependence expected of Auger recombination kinetics. Introducing hole scavenging HS– has a negligible effect on the exciton kinetics, including migration and dissociation, and instead passivates surface trap states to induce the rapid elimination of holes after exciton dissociation. This increases the lifetime of the reactive electron population and increases measured photocatalytic H2 generation activity. A broad (200 nm) and persistent (20 ps) stimulated emission observed in the tightly bound excitons suggests their potential use as broadband microlasers.The Journal of Physical Chemistry C. 09/2011; 115(40).