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We demonstrate a novel way to realize room-temperature polariton parametric scattering in a one-dimensional ZnO microcavity. The polariton parametric scattering is driven by a polariton condensate, with a balanced polariton pair generated at the adjacent polariton mode. This parametric scattering is experimentally investigated by the angle-resolved photoluminescence spectroscopy technique under different pump powers and it is well described by the rate equation of interacting bosons. The direct relation between the intensity of the scattered polariton signal and that of the polariton reservoir is acquired under nonresonant excitation, exhibiting the explicit nonlinear characteristic of this room-temperature polariton parametric process. [ABSTRACT FROM AUTHOR]

Hollow Gd2O3:Ln (Ln = Eu3, Sm3) microspheres were successfully fabricated by using carbon spheres as a template and urea as a precipitating agent, which involved the deposition of an inorganic coating on the surface of carbon spheres and subsequent calcination in the air. Various approaches including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence spectroscopy as well as kinetic decays were used to characterize the samples. The results indicate that the as-prepared products can be indexed to pure cubic Gd2O3phase. The samples are composed of uniform hollow Gd2O3:Ln spheres with a mean particle size of about 300 nm. The possible mechanism of evolution from glucose to carbon microspheres and the chemical reaction of each step to form the final hollow spheres are proposed. In particular, the urea-assisted precipitation process was carried out in aqueous solution without any organic solvent, and the hollow spheres formation process was achieved by simple calcination without using any etching agents. The hollow Gd2O3:Ln phosphors exhibit light emission under ultraviolet excitation, which may find promising applications in the fields of field emission displays (FED) and MRI contrast agents. [ABSTRACT FROM AUTHOR]

Hollow Gd2O3:Ln (Ln = Eu3+, Sm3+) microspheres were successfully fabricated by using carbon spheres as a template and urea as a precipitating agent, which involved the deposition of an inorganic coating on the surface of carbon spheres and subsequent calcination in the air. Various approaches including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence spectroscopy as well as kinetic decays were used to characterize the samples. The results indicate that the as-prepared products can be indexed to pure cubic Gd2O3phase. The samples are composed of uniform hollow Gd2O3:Ln spheres with a mean particle size of about 300 nm. The possible mechanism of evolution from glucose to carbon microspheres and the chemical reaction of each step to form the final hollow spheres are proposed. In particular, the urea-assisted precipitation process was carried out in aqueous solution without any organic solvent, and the hollow spheres formation process was achieved by simple calcination without using any etching agents. The hollow Gd2O3:Ln phosphors exhibit light emission under ultraviolet excitation, which may find promising applications in the fields of field emission displays (FED) and MRI contrast agents. [ABSTRACT FROM AUTHOR]

Abstract: LaPO4, LaPO4:Ce3+ and LaPO4:Ce3+, Tb3+ particles with different morphologies and sizes have been successfully synthesized via a simple EDTA assisted hydrothermal method. The effects of the doping components, pH value, and the chelating reagent on the phases, structures and morphologies were well investigated by means of X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Photoluminescent (PL) spectra and kinetic decays were used to characterize the fluorescent properties of the samples. The results reveal that all the samples are of high purity and assigned to the single-crystalline monoclinic structure of LaPO4 phase. The aspects ratio of the nanostructures synthesized in acid synthetic condition is larger than those obtained in alkaline solution. Additionally, the Ce3+ or/and Tb3+ doped LaPO4 particles show less smoother surface compared with pure LaPO4. Furthermore, the tendency for anisotropic growth under hydrothermal conditions can be simply enhanced by selecting the chelating ligands (EDTA). The possible growth mechanism of the LaPO4:Ln3+ (Ln = Ce3+, Tb3+) nanostructures has been proposed as well. Upon ultraviolet excitation, LaPO4:Ce3+ and LaPO4:Ce3+, Tb3+ phosphors show the characteristic 5d–4f emissions of Ce3+ and 5D4–7F j (j = 6–3) emission lines of Tb3+, respectively. [ABSTRACT FROM AUTHOR]

β-Ga2O3 cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates at 750–1000°C for 2 h in air. The controllable synthesis of β-Ga2O3 nanowires with different diameters and lengths was achieved by adjusting the heating temperature and time. The as-synthesized products were characterized by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the β-Ga2O3 nanowires are single crystalline with a monoclinic structure and have a controllable diameter and length in the range of 30–100 nm and 0.5–1.5 μm, respectively. A possible mechanism was also proposed to account for the formation of β-Ga2O3 cone-like nanowires. Photoluminescence spectra of the β-Ga2O3 nanowires obtained at different temperatures were measured at room temperature, and a strong blue photoluminescence with peaks at 430 and 460 nm and a weak red photoluminescence with peak at 713 nm were observed. The blue light emission intensity decreases with increasing the reaction temperature, however, the red light emission intensity hardly changes. The blue and red light emissions originate from the recombination of an electron on an oxygen vacancy with a hole on a gallium-oxygen vacancy pair and the nitrogen dopants, etc., respectively. [ABSTRACT FROM AUTHOR]

High-quality In2O3 polyhedrons with different morphologies were fabricated and studied as vertical Fabry-Pérot (FP) microcavities. By using the microphotoluminescence technique, we identified a series of FP resonant modes in such systems, whose energies lie in the visible spectral range and are scalable with the cavity size. Experimental results are in good agreement with full-wave numerical simulations and can be well fitted with a plane wave interference model. Compared with the conventional one dimensional nanowire/nanobelt FP cavities, such vertical FP microcavities have much less optical loss and provide efficient optical modulations, which may find many applications in developing optical devices. [ABSTRACT FROM AUTHOR]

We demonstrate the observation of the strong excitons-photons coupling in pencil-like ZnO microwires at room temperature. The pencil-like ZnO microwires with high optical quality were fabricated by using a carbothermal growth method at 1100 °C. The strong coupling of excitons and photons is evidenced by using angle-resolved photoluminescence spectroscopy. By scanning excitations spot from the arm to the tip of the pencil-like ZnO microwires, we found that the confinement of the tip is weaker than that of the arm due to the shrinked size. With increasing the excitation power, the lowest energy states of exciton-polariton modes are remarkably populated, and lasing phenomena are observed. By using the coupled oscillator model, the polariton effect can be well described. [ABSTRACT FROM AUTHOR]

Abstract: Straight and zigzag-shaped nanowires of GaN have been grown in situ on the surface of the gallium grains and alumina ceramic substrates by heating metallic gallium grains on alumina ceramic wafers in the presence of NH3 at 1000 and 1050°C for 0.5h, and their controllable synthesis was achieved by changing the reaction temperature. The growth of straight and zigzag-shaped GaN nanowires is governed by a vapor–solid (V–S) process, and the evolution of straight GaN nanowires to zigzag-shaped nanowires may arise from the change of Ga/N ratio and GaN vapor concentration in the reaction system. A strong UV emission band centered at 372(362)nm and a weak blue emission peak at 460nm were observed from the straight and zigzag-shaped GaN nanowires. [Copyright &y& Elsevier]