NO₂-sensing properties of semiconductor gas sensors using porous In₂O₃ powders loaded with and without 0.5 wt% Au (Au/In₂O₃ and In₂O₃ sensors, respectively) were examined in wet air (70% relative humidity at 25 °C). In addition, the effects of Au loading on the increased NO₂ response were discussed on the basis of NO₂ adsorption/desorption properties on the oxide surface. The NO₂ response of the Au/In₂O₃ sensor monotonically increased with a decrease in the operating temperature, and the Au/In₂O₃ sensor showed higher NO₂ responses than those of the In₂O₃ sensor at a temperature of 100 °C or lower. In addition, the response time of the Au/In₂O₃ sensor was much shorter than that of the In₂O₃ sensor at 30 °C. The analysis based on the Freundlich adsorption mechanism suggested that the Au loading increased the adsorption strength of NO₂ on the In₂O₃ surface. Moreover, the Au loading was also quite effective in decreasing the baseline resistance of the In₂O₃ sensor in wet air (i.e., increasing the number of free electrons in the In₂O₃), which resulted in an increase in the number of negatively charged NO₂ species on the In₂O₃ surface. The Au/In₂O₃ sensor showed high response to the low concentration of NO₂ (ratio of resistance in target gas to that in air: ca. 133 to 0.1 ppm) and excellent NO₂ selectivity against CO and ethanol, especially at 100 °C.

In this study, double-multilayer monochromators that generate intense, high-energy, pink X-ray beams are designed, installed and evaluated at the SPring-8 medium-length (215 m) bending-magnet beamline BL20B2 for imaging applications. Two pairs of W/B₄C multilayer mirrors are designed to utilize photon energies of 110 keV and 40 keV with bandwidths of 0.8% and 4.8%, respectively, which are more than 100 times larger when compared with the Si double-crystal monochromator (DCM) with a bandwidth of less than 0.01%. At an experimental hutch located 210 m away from the source, a large and uniform beam of size 14 mm (V) × 300 mm (H) [21 mm (V) × 300 mm (H)] was generated with a high flux density of 1.6 × 10⁹ photons s⁻¹ mm⁻² (6.9 × 10¹⁰ photons s⁻¹ mm⁻²) at 110 keV (40 keV), which marked a 300 (190) times increase in the photon flux when compared with a DCM with Si 511 (111) diffraction. The intense pink beams facilitate advanced X-ray imaging for large-sized objects such as fossils, rocks, organs and electronic devices with high speed and high spatial resolution.

Mesoporous and/or macroporous SnO₂-based powders have been prepared and their gas-sensing properties as thick film sensors towards H₂ and NO₂ have been investigated. The mesopores and macropores of various SnO₂-based powders were controlled by self-assembly of sodium bis(2-ethylhexyl)sulfosuccinate and polymethyl-methacrylate (PMMA) microspheres (ca. 800 nm in diameter), respectively. The introduction of mesopores and macropores into SnO₂-based sensors increased their sensor resistance in air significantly. The additions of SiO₂ and Sb₂O₅ into mesoporous and/or macroporous SnO₂ were found to improve the sensing properties of the sensors. The addition of SiO₂ into mesoporous and/or macroporous SnO₂ was found to increase the sensor resistance in air, whereas doping of Sb₂O₅ into mesoporous and/or macroporous SnO₂ was found to markedly reduce the sensor resistance in air, and to increase the response to 1,000 ppm H₂ as well as 1 ppm NO₂ in air. Among all the sensors tested, meso-macroporous SnO₂ added with 1 wt% SiO₂ and 5 wt% Sb₂O₅, which were prepared with the above two templates simultaneously, exhibited the largest H₂ and NO₂ responses.