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The slow solvent evaporation technique has been employed for the synthesis of l-arginine perchlorate (LAPCl) single crystals. The grown crystals are doped with 1, 2 and 3 mol% of MnCl2. The Powder X-ray Diffraction (PXRD) analysis confirmed that the pure and doped crystals belong to the orthorhombic crystal system with non-centrosymmetric space group P212121. The incorporation of dopants has been confirmed by Laser-Induced Breakdown Spectroscopy (LIBS) and Energy Dispersive X-ray Analysis (EDX). The modification in the linear optical properties has been analyzed by measuring the cut off wavelength, band gap, Urbach energy and the refractive index of the pure and doped crystals. The changes in the nonlinearity of the LAPCl have been studied by open aperture Z-scan technique and found that two-photon absorption (2PA) coefficient increased with increasing the dopant concentration. The dielectric properties, electronic polarizability and thermal properties of the pure and doped crystals are also studied. [ABSTRACT FROM AUTHOR]

Platinum nanocrystals in the size range of a few nanometers are especially interesting candidates for catalytic applications. We present an easy, low-temperature procedure, which allows for a precise size control of this material. Uniform platinum nanoparticles were obtained by reduction of platinum(IV)chloride with tetrabutylammonium borohydride in toluene solution at room temperature. Dodecylamine served as a ligand. The size of the resulting particles could be controlled in the range between 2 and 5 nm by slow addition of platinum monomers and the reducing agent to preformed 2 nm seeds. Furthermore, particles with a tetrapod shape could be synthesized. In contrast to the usual kinetic control leading to the formation of elongated structures, the analysis of the growth process of the tetrapods suggests a reactioncontrolled growth process. Their structure was investigated by powder X-ray diffraction and highresolution electron microscopy, which revealed that two branches of the tetrapods grow along the (111) direction, while the other two show growth in the (220) direction. This uncommon shape of the tetrapods is attributable to the presence of a twin defect parallel to the (220) direction. Thus, the method presented in the article allows for the formation of platinum particles with a single twin defect with a high yield. [ABSTRACT FROM AUTHOR]

Abstract: Phosphor powders of Yb3+ co-doped BaZrO3:Er3+ have been prepared by the urea combustion route. The formation of single-phase BaZrO3:Er3+ and BaZrO3:Er3+,Yb3+ was confirmed by X-ray powder diffraction (XRD). Green and red luminescence along with a weaker blue emission is observed upon excitation at ∼978nm with a diode laser. These emissions are caused by frequency upconversion in the Er3+-doped BaZrO3 (BZO) phosphor. Both the green and red upconversion emissions of the Er3+ are enhanced by about ∼3 and ∼43 times respectively when triply ionized ytterbium is incorporated as a co-dopant. The frequency upconversion processes responsible for the blue, green and red emissions are discussed on the basis of the experimental data. [Copyright &y& Elsevier]

Abstract: Tb3+ doped CaZrO3 has been prepared by an easy solution combustion synthesis method. The combustion derived powder was investigated by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy techniques. A room temperature photoluminescence study showed that the phosphors can be efficiently excited by 251nm light with a weak emission in the blue and orange region and a strong emission in green light region. CaZrO3:Tb3+ exhibits three thermoluminescence (TL) glow peaks at 126°C, 200°C and 480°C. Electron Spin Resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the centres responsible for the TL peaks. The room temperature ESR spectrum of irradiated phosphor appears to be a superposition of two distinct centres. One of the centres (centre I) with principal g-value 2.0233 is identified as an O− ion. Centre II with an axial symmetric g-tensor with principal values g =1.9986 and g ˔=2.0023 is assigned to an F+ centre (singly ionised oxygen vacancy). An additional defect centre is observed during thermal annealing experiments and this centre (assigned to F+ centre) seems to originate from an F centre (oxygen vacancy with two electrons). The F centre and also the F+ centre appear to correlate with the observed high temperature TL peak in CaZrO3:Tb3+ phosphor. [Copyright &y& Elsevier]