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  1. null (Ed.)
    We report on the different surface structures of tungsten oxides which have been synthesized using a simple post-annealing-free hot-filament CVD technique, including 0D nanoparticles (NPs), 1D nanorods (NRs), and 2D nanosheet assemblies of 3D hierarchical nanoflowers (NFs). The surface morphologies, crystalline structures, and material compositions have been characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy, respectively. The sensor performances based on the synthesized samples of various surface morphologies have been investigated, as well as the influences of operating temperature and applied bias. The sensing property depends closely on the surface morphology, and the 3D hierarchical nanoflowers-based gas sensor offers the best sensitivity and fastest response time to NH3 and CH3 gases when operated at room temperature. 
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  4. Diamond-based sensors have shown great potential in the past few years due to their unique physicochemical properties. We report on the development of high-performance nitrogen-doped ultrananocrystalline diamond (UNCD) nanowire-based methane (CH4) gas sensors, taking advantage of a large surface-to-volume ratio and a small active area offered by the 1D nanowire geometry. The morphologic surface and crystalline structures of UNCD are also characterized by using scanning electron microscopy (SEM) and Raman scattering, respectively. By using synthesized nanowire arrays combined with 4-pin electrical electrodes, prototypic highly sensitive CH4 gas sensors have been designed, fabricated and tested. Various parameters including the sensitivity, response and recovery times, and thermal effect on the performance of the gas sensor have also been investigated in order to quantitate the sensing ability. Enhanced by the small grain size and porosity of the nanowire structure, fabricated nanowire UNCD sensors demonstrated a high sensitivity to CH4 gas at room temperature down to 2 ppm, as well as fast response and recovery times which are almost 10 times faster than that of regular nanodiamond thin film based sensors. 
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    Abstract This paper reports the results of preparing alloy nanoparticles by mechanical grinding followed by filtration to sort the particles according to size. Although the long-term goal of this work is to prepare icosahedral quasicrystalline nanoparticles, the alloy used in this study is of Al 65 Cu 25 Fe 15 composition and multi phases, under the assumption that the established procedure is applicable to future quasicrystalline nanoparticle fabrication. The obtained particle size and elemental information were investigated using scanning electron microscopy and energy dispersive x-ray spectroscopy. Problems with filter fragment fall-out and salt contamination were encountered and procedures to address the problems have been suggested and tested. The study is successful in obtaining alloy particles with reduced sizes. 
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