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SrAl2O4nanosized particles (NPs) undoped as well as doped with Eu2+and Dy3+were prepared by combustion synthesis for the discussion of their intensively debated spectroscopic properties. Emission spectra of SrAl2O4:Eu2+(,Dy3+) NPs are composed by a green band at 19 230 cm−1(520 nm) at room temperature, assigned to anomalous luminescence originated by Eu2+in this host lattice. At low temperatures, a blue emission band at 22 520 cm−1(444 nm) is observed. Contrary to most of the interpretations provided in the literature, we assign this blue emission band very reliably to a normal 4f6(7FJ)5d(t2g)→4f7(8S7/2) transition of Eu2+substituting the Sr2+sites. This can be justified by the presence of a fine structure in the excitation spectra due to the different7FJlevels (J=0⋯6) of the 4f6core. Moreover, Fano antiresonances with the6IJ(J=9/2,7/2) levels could be observed. In addition, the Stokes shifts (ΔES=1980 cm−1and 5 270 cm−1for the blue and green emission, resp.), the Huang-Rhys parameters ofS=2.5and 6, and the average phonon energies ofħω=480 cm-1and 470 cm−1coupled with the electronic states could be reliably determined.

One of the challenges in the development of germanium nanowires (Ge NWs) is to increase their length beyond the 10 μm limit without enlarging the NW diameter, i.e. minimizing the tapering. Here we report how it is possible to overcome this hurdle by using isobutyl germane (iBuGe) as a metal organic precursor during MOCVD growth, instead of the commonly used germane. We have grown and characterized by transmission electron microscopy, scanning electron microscopy and Raman various samples and we have analyzed the effect of growth time, precursor flux and growth temperature on the NW length. The use of iBuGe coupled to optimized growth conditions permitted to obtain Ge NWs with lengths up to 30 μm with minimal tapering. To explain why a new precursor has this impact on the morphology of the NWs we consider two possible causes: (i) the role of carbon radicals produced by isobutyl decomposition and (ii) the reduced growth rate of Ge on the sidewalls. On the basis of Raman characterization and temperature-dependence of tapering, we conclude that the reduced tapering is probably due to lower growth rates on the sidewalls.

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new Aerosol assisted CVD method of synthesizinglarge amount ofhigh quality carbon nanotubes (CNTs) with good structural parameters has been developed. We report the optimization of the process by experimental variables of thesynthesis condition. The effect of temperature in the hot zone of the reactor was investigated, and 840-950 0C was chosen as an optimum synthesis temperature. CNTs, obtained with different solvents as a carbon source have been analyzed, and ferrocene volume in cyclohexane solvent was varied, as the result of which has been grown MWCNTs with diameters of 10-85 nm and a small percent of SWCNTs with diameters of 0.85 and 1.14 nm. The position of Fe nanoparticles in the CNTs was defined by TEM observations, which show that Fe nanoparticles