p‐Type Optoelectronic and Transparent Conducting Oxide Properties of Delafossite CuAl1/2Fe1/2O2

CuAl_1/2Fe_1/2O₂ delafossite was prepared using a solid‐state reaction method to investigate its optical and electronic transport properties. CuAl_1/2Fe_1/2O₂ formed a hexagonal delafossite structure with an Rm space group. The positive Seebeck coefficient and the direct optical gap of 3.6 eV confirmed that the CuAl_1/2Fe_1/2O₂ delafossite in a p‐type transparent conducting oxide. The fluorescence emission at 390 nm (green emission) confirmed that CuAl_1/2Fe_1/2O₂ has a direct transition band gap. Thermogravimetric analysis indicated a weight loss of 1.2%, caused by the intercalation of O atoms, which produced hole carriers from the different ionic radii at the B sites. The electric conductivity at room temperature was thermally activated, as predicted by the small‐polaron hopping mechanism, with an activation energy of 75 meV and a charge transport energy of 61 meV. CuAl_1/2Fe_1/2O₂ delafossite exhibited p‐type optoelectronic behavior and is a transparent conducting oxide, which may be crucial in the p‐type photonic and electrode industries.     

Characteristics and Catalytic Properties of Mesocellular Foam Silica Supported Pd Nanoparticles in the Liquid-Phase Selective Hydrogenation of Phenylacetylene

Abstract  

An ultra-large pore mesocellular foam silica (MCF) was employed as a support for preparation of supported Pd catalysts for the liquid-phase selective hydrogenation of phenylacetylene. The catalysts were prepared by three different routes: (i) incipient wetness impregnation using Pd(II)acetate solution (Pd/MCF-imp), (ii) impregnation of colloidal Pd nanoparticles obtained by the solvent reduction method (Pd/MCF-col), and (iii) in situ synthesis of MCF in the presence of the Pd colloid (Pd/MCF-ss). The conventional impregnation method resulted in more agglomeration of Pd particles and partial collapse of MCF structure, hence the Pd/MCF-imp exhibited the lowest selectivity towards styrene at total conversion of phenylacetylene. Only the Pd/MCF-ss, in which most of the Pd nanoparticles were encapsulated by the silica matrix, was found to retain high styrene selectivity (>80%) after complete conversion of phenylacetylene. Comparing to the other highly efficient Pd catalysts reported in the literature under similar reaction conditions, it can be emphasized that coverage of Pd surface by the support produces great beneficial effect for enhancing styrene selectivity, regardless of the type of supports used (i.e., TiO₂, carbon nanotubes, or mesostructured silica).     

Demonstration of a single-wavelength spectral-imaging-based Thai jasmine rice identification

A single-wavelength spectral-imaging-based Thai jasmine rice breed identification is demonstrated. Our nondestructive identification approach relies on a combination of fluorescent imaging and simple image processing techniques. Especially, we apply simple image thresholding, blob filtering, and image subtracting processes to either a 545 or a 575 nm image in order to identify our desired Thai jasmine rice breed from others. Other key advantages include no waste product and fast identification time. In our demonstration, UVC light is used as our exciting light, a liquid crystal tunable optical filter is used as our wavelength seclector, and a digital camera with 640 active pixels × 480 active pixels is used to capture the desired spectral image. Eight Thai rice breeds having similar size and shape are tested. Our experimental proof of concept shows that by suitably applying image thresholding, blob filtering, and image subtracting processes to the selected fluorescent image, the Thai jasmine rice breed can be identified with measured false acceptance rates of <22.9% and <25.7% for spectral images at 545 and 575 nm wavelengths, respectively. A measured fast identification time is 25 ms, showing high potential for real-time applications.