Superconductivity and its enhancement under high pressure in “F-free” single crystals of CeOBiS2

“F-free” CeOBiS2 single crystals have successfully grown, thoroughly eliminating a concern about F-contamination by using a high-purity CsCl flux. The obtained crystals have a plate-like shape with a size of 1.0–3.0 mm in the well-developed plane. Single crystal X-ray structural analysis clearly revealed that the CeOBiS2 crystallizes with a space group P4/nmm (with lattice parameters of a = 4.0189 (6) Å, c = 13.573 (2) Å). The bond valence sum estimation and X-ray photoelectron spectroscopy analysis showed that the chemical state of Ce was in the mixed valence of Ce3+ and Ce4+. The single crystals show superconductivity with zero resistivity at ∼1.3 K. This is the first conclusive evidence of superconductivity driven by Ce valence fluctuation in surely non-doped CeOBiS2. The superconducting transition temperature was enhanced up to ∼3.8 K by applying hydrostatic pressure

Modified spontaneous emission properties of CdS quantum dots embedded in novel three-dimensional microcavities

Modified spontaneous emission properties in the presence of confined photon modes inside the three-dimensional (3-D) optical microcavities are demonstrated. Self-formed pyramidal-shaped semiconductor structures fabricated by selective-area growth technique are utilized as an optical microcavity in which discrete photon modes are generated. Noticeable modification of spontaneous emission from active layers embedded in microcavity structures is clearly observed in μ-PL spectra at room temperature. Almost perfect coincidence between enhanced photoluminescence peak wavelengths and the resonance modes inside microcavity is observed. Furthermore, Purcell factors calculated from the obtained Q values reach ∼9, which is inaccessible in the planar microcavities with only one-dimensional photon confinement normal to the layers. These results indicate that the effective coupling between electronic system and 3-D confined optical fields is realized by the achievement of present low-loss 3-D microcavities with small cavity volume Vc whose dimension is comparable with λ3

Polydimethylsiloxane-coated macroporous silica adsorbent in thermal desorption gas chromatography

Polydimethylsiloxane (PDMS)-coated macroporous silica (MPSi) particles were developed for the extraction of volatile organic compounds (VOCs) from air samples in thermal desorption-gas chromatographic analysis. The gas sample was collected by a gas sampling pump at 100 mL/min. Different amounts of PDMS coating were prepared, and the fundamental extraction and desorption performances were investigated using even numbered n-alkanes of C8–C28. The extraction efficiency increased by increasing PDMS coating, and the desorption efficiency showed more than 99% at a desorption temperature of 310°C for all the investigated adsorbents. This remarkable desorption performance showed a higher peak area of the analytes than that of the Tenax TA-packed thermal desorption tube, especially for higher molecular weight compounds. Furthermore, an activated carbon particle of Carbopack X was introduced on the latter side of the PDMS-MPSi to extract low-molecular weight compounds. This double-bed-type extraction tube showed a successful determination of a wide range of VOCs. The double-bed-type extraction tube was then applied to the extraction of VOCs related to sick building syndrome (SBS). The results for the extraction and desorption performances of the SBS-related VOCs were well agreed with that of alkanes, and the applicability of the extraction tube to the determination of other types of conventional VOCs were confirmed