Synthesis of CuxCo3-xO4 nanoparticles by a sonochemical method and characterization of structural and optical properties and photocatalytic activity for the degradation of methylene blue.

In the present investigation, CuxCo3-xO4 (x = 0, 0.02, 0.04, 0.06, 0.1) nanoparticles have been synthesized by the sonochemical method and subsequent calcination at high temperature. The synthesized nanoparticles were further characterized using X-ray diffraction, UV-vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The analysis results showed that nanoparticle size, band gap and photocatalytic activity of CuxCo3-xO4 compounds change by altering the Cu doping content. According to the XRD study, no impurity peaks associated with copper or copper oxide phases were observed in the diffractograms of doped samples. The highest degradation of methylene blue dye under visible light was observed in the presence of Cu0.02Co2.98O4 nanoparticles and found to be 87.51% after 330 minutes. This value increased with increasing the amount of photocatalyst and with decreasing dye concentration.

Extra-long and taper-free germanium nanowires: use of an alternative Ge precursor for longer nanostructures.

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.