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CdTe0.5Se0.5/Cd0.5Zn0.5S core/shell quantum dots (QDs) with a tunable photoluminescence (PL) range from yellow to dark red (up to a PL peak wavelength of 683 nm) were fabricated using various reaction systems. The core/shell QDs created in the reaction solution of trioctylamine (TOA) and oleic acid (OA) at 300 °C exhibited narrow PL spectra and a related low PL efficiency (38%). In contrast, the core/shell QDs prepared in the solution of 1-octadecene (ODE) and hexadecylamine (HDA) at 200 °C revealed a high PL efficiency (70%) and broad PL spectra. This phenomenon is ascribed that the precursor of Cd, reaction temperature, solvents, and ligands affected the formation process of the shell. The slow growth rate of the shell in the solution of ODE and HDA made QDs with a high PL efficiency. Metal acetate salts without reaction with HDA led to the core/shell QDs with a broad size distribution. [ABSTRACT FROM AUTHOR]

Abstract: Comparing with the other metal chalcogenide semiconductors, copper selenide has still not been well researched in nanoscience and nanotechnology, probably due to the difficulty in the controllable synthesis of its various phase. In the present work, Cu2−δ Se and CuSe were synthesized open to air through a green paraffin-acetate method. The morphology study indicated that the copper selenide mainly showed hexagonal nanoplates/nanowires or only hexagonal nanoplates. The SDBS-modified sample exhibited good dispersivity in water. The phase, composition (δ value) and morphology of the products could be controlled by adjusting the reaction parameters. Stability, redox and the effective Cu/Se ratio were thought as the major factors that determine the phase of the final products, and a concentration-limited growth mechanism was proposed to explain the formation of the various morphologies. The optical properties of the copper selenide were characterized by UV–visible diffuse reflectance spectroscopy (UV-DRS). [ABSTRACT FROM AUTHOR]

Abstract: Eu3+ doped yttrium zirconate ((Y1−x Eu x )2Zr2O7) nanocrystals were synthesized by a simple sol–gel combustion method, and characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV–vis absorption and photoluminescence (PL) spectroscopy. Photoluminescence spectra of (Y1−x Eu x )2Zr2O7 (x =0.005–0.15) show multi-peaks corresponding to the f–f transitions 5 D 0–7 F J (J =1, 2, 3, 4 and 5) of Eu3+. Both the 5 D 0–7 F 1 magnetic dipole transition and the 5 D 0–7 F 2 electric dipole transition are intense and the 5 D 0–7 F 2 emissions split into several peaks depending on the doping concentration. The fine structure of the PL spectra is related to host lattice and the local situation around Eu3+. [Copyright &y& Elsevier]

Abstract: The large scale synthesis of multiple crystalline silver nanowires (NWs) with uniform diameter were carried out by using glycerol and ethylene glycol (EG) as co-mediated solvents in the presence of poly(vinyl pyrrolidine) (PVP). Experimental results and structural characterizations reveal that Ag NWs are evolved from the multiple crystalline seeds initially generated by the reduction of AgNO3 with EG and glycerol. Owing to the different reduction ability and viscosity of EG and glycerol, which play an important role for controlling the nucleation at the beginning of reaction, glycerol with high viscosity slows down the migration velocity of Ag0 in favor of forming the uniform Ag NWs with small diameter (40 nm) in the presence of PVP molecules selectively adsorbed on the surface of Ag seeds. The yield of the Ag NWs is dependent on the volume ratio of EG and glycerol. In the absence of EG, large amount of Ag nanoparticles (NPs) and few Ag NWs were created. In contrast, Ag nanorods and polyhedral particles are prepared in the case of no glycol added. This paper provides a new approach for the large scale synthesis of Ag NWs with uniform diameter by simply adjusting the solvent components. Furthermore, V-shaped Ag nanostructure was obtained and the possible growth mechanism was discussed. [Copyright &y& Elsevier]

Porous ZnFe 2 O 4 nanotubes and nanobelts have been fabricated through an efficient and facile approach of electrospinning followed by two-step calcination in atmosphere. The influences of electrospinning parameters such as metallic salt content, PVP content, the ratio of ethanol to water, stirring time and applied voltage on the composite fibers have been fully investigated. When the calcination temperature was increased from 600 °C to 650 °C, the ZnFe 2 O 4 nanotubes evolved into well-crystalline nanobelts due to the faster gas diffusion, more active grain growth and atomic diffusion rate caused by the relative high temperature. The plausible formation mechanism of ZnFe 2 O 4 nanotubes and nanobelts was proposed and discussed in detail. The photocatalytic activities for the photo-degradation of Rhodamine B (RhB) over ZnFe 2 O 4 nanotubes and nanobelts were evaluated under the UV-light irradiation. The degradation efficiency of nanotubes and nanobelts both can reach 99.7% after 20 min UV irradiation in presence of H 2 O 2 because of synergistic effects of Fe 3+ and H 2 O 2 , respectively, indicating the excellent Fenton-like photocatalytic properties of ZnFe 2 O 4 nanotubes and nanobelts. Additionally, the Fenton-like photocatalytic mechanism was also discussed. [ABSTRACT FROM AUTHOR]

The polyvinylpyrrolidone (PVP) hybrid luminescent micro-/nanofibers doped with the novel hybrid SiO 2 -coated CdTe nanocrystals (HS-CdTe NCs) have been fabricated for the first time via the electrospinning technique. The morphologies and photoluminescence (PL) emissions of HS-CdTe/PVP micro-/nanofibers prepared by doping the HS-CdTe NCs with the different PL peak wavelength (571, 616, and 643 nm) in PVP fibers were investigated by optical and PL microscope. The results revealed that all the HS-CdTe/PVP hybrid fibers showed an ultralong length for several hundreds of micrometers and a relatively uniform diameter of 1000 ∼ 1200 nm. The hybrid fibers displayed a wavelength-tunable PL emission, determining by the PL of doped HS-CdTe NCs. Moreover, similar to the original PL properties of HS-CdTe NCs before the electrospinning, the HS-CdTe/PVP fibers also showed a series of superior PL properties, such as narrow and symmetry PL spectrum, high, and uniform brightness. For comparison purpose, we also prepared three CdTe/PVP hybrid fibers by doping the 553 nm, 600 nm, and 633 nm PL-emitting CdTe NCs respectively in PVP electrospinning fibers. The characterization results showed that, the obtained three CdTe/PVP hybrid fibers had a basically satisfactory micro-/nanofiber morphology with a long length and relatively uniform diameter, but all the fibers exhibited very weak PL emissions. The enormous contrast in PL properties between HS-CdTe/PVP and CdTe/PVP fibers should mainly be ascribed to the different connection modes of ligands with the NCs and the passivation effect of inert hybrid silica shell on HS-CdTe. It is hopeful that the high luminescent HS-CdTe/PVP micro-/nanofibers with the tunable PL peak wavelength would be a good candidate in the optical sensor, light-emitting devices (LEDs), nanometer-scale waveguides, and the other related photonic materials. [ABSTRACT FROM AUTHOR]

Abstract: Undoped and Eu3+-activated Bi3TiNbO9 (BTNO) nanophosphors have been successfully synthesized by sol–gel combustion method. The effects of thermal annealing on the phase structure and crystallinity, morphology and UV–vis absorption of BTNO particles were investigated. Photoluminescence (PL) properties show that a broad blue emission was detected for BTNO nanoparticles, and the characteristic Eu3+ ion 5D0 → 7F J (J =1, 2, 3, 4) transitions were observed for the doped samples. Further investigation illuminates that the Eu3+ ions substituted for Bi3+ ions at A site in the pseudo-perovskite layers. It can be confirmed from high bright fluorescence image and short decay time that the novel orange-red phosphor has the potential applications in luminescence devices. [Copyright &y& Elsevier]

Abstract: Bi4Ti3O12 thin films with bismuth-layered perovskite structure have been successfully fabricated by means of chemical solution decomposition (CSD) and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV–vis spectrophotometry in this study. The photocatalytic activity of Bi4Ti3O12 thin films has been evaluated by photodegrading methyl orange solution, and the optimum processing parameters for the photocatalytic activity have been found. Moreover, it has been found that La-doping can improve the photocatalytic activity of Bi4Ti3O12 thin films and hinder the increase of crystallite sizes during calcination. [Copyright &y& Elsevier]

Abstract: A novel red luminescent material Li0.9Y0.9Zr0.1O2 doped with trivalent europium ions and dysprosium ions was synthesized by solution–combustion method. X-ray diffractometry, transmission electron microscopy and optical spectroscopy were used to valuate the crystallinity, the morphological characterization and the optical properties of the products. The results showed that combustion at 800°C was enough to obtain highly crystalline and phase-pure samples. Photoluminescence spectra of Li0.9Y(0.9−x−y)Zr0.1O2:Eu x 3+,Dy y 3+ samples indicated the dominant red emissions (613nm) at a single-wavelength ultraviolet excitation (395nm) due to 5D0 → 7F2 transition. The relation between the luminescence intensity and dopant concentration was also discussed. [Copyright &y& Elsevier]