Electrooptic effect of water in electric double layer at interface of GaN electrode

We determined the Pockels constant of water in the electric double layer (EDL) at the GaN electrode interface. For a positive (negative) bias, the difference transmittance showed a blue (red) shift in the interference fringes in the visible. This was caused by a negative (positive) refractive index change both in the EDL of water and in the space charge layer (SCL) of the GaN. The latter was associated with the blue shift in the absorption edge in the UV due to the band population effect in the GaN. The voltage drops took place within the interfacial layer at a ratio of about 3: 1 for the SCL vs EDL at the modulation frequency of f = 20 Hz, estimated from the frequency dependence of the impedance. The Pockels constant of water in the EDL was determined to be r ₁₃ = 0:63 × 100 pm/V for the GaN electrodes. This is three times smaller than that at the surface of the indium tin oxide (ITO) electrode.     

Fluorometric determination of Ethofenprox in water by using solid-phase extraction

Ethofenprox (pesticide) exhibits a relatively strong fluorescence in the UV region. Its fluorescence properties were investigated in aqueous solution, organic solvents, and micellar media. The fluorescence intensity of Ethofenprox was enhanced by a factor of 1.2 to 2.7 in the presence of surfactants and by 1.4 in pure organic solvents without significant shift of the excitation and emission wavelengths. The conditions for solid-phase extraction of Ethofenprox from water samples were examined. Among the solid-phase extraction cartridges studied, a Sep Pak C8 with weak sorption ability was found to be the most useful due to the extremely high hydrophobicity of Ethofenprox. For the complete elution of Ethofenprox from the sorbent, an addition of 40%v/v methanol to the sample water was necessary and effective to eliminate the fluorescent impurities of the matrix. The calibration graph obtained was linear over the range of 0.03 to 2.4 mg L^–1 in 100 mL sample. The method was successfully applied to the determination of Ethofenprox in tap, well, and river waters with recoveries of 93.2–95.7%.     

Two-Dimensional Perovskite Oxynitride K2LaTa2O6N with an H+/K+ Exchangeability in Aqueous Solution Forming a Stable Photocatalyst for Visible-Light H2 Evolution

Undoped layered oxynitrides have not been considered as promising H₂-evolution photocatalysts because of the low chemical stability of oxynitrides in aqueous solution. Here, we demonstrate the synthesis of a new layered perovskite oxynitride, K₂LaTa₂O₆N, as an exceptional example of a water-tolerant photocatalyst for H₂ evolution under visible light. The material underwent in-situ H⁺/K⁺ exchange in aqueous solution while keeping its visible-light-absorption capability. Protonated K₂LaTa₂O₆N, modified with an Ir cocatalyst, exhibited excellent catalytic activity toward H₂ evolution in the presence of I⁻ as an electron donor and under visible light; the activity was six times higher than Pt/ZrO₂/TaON, one of the best-performing oxynitride photocatalysts for H₂ evolution. Overall water splitting was also achieved using the Ir-loaded, protonated K₂LaTa₂O₆N in combination with Cs-modified Pt/WO₃ as an O₂ evolution photocatalyst in the presence of an I₃⁻/I⁻ shuttle redox couple.     

A Peptide Nucleic Acid (PNA) Heteroduplex Probe Containing an Inosine–Cytosine Base Pair Discriminates a Single‐Nucleotide Difference in RNA

Selective discrimination of a single‐nucleotide difference in single‐stranded DNA or RNA remains a challenge with conventional DNA or RNA probes. A peptide nucleic acid (PNA)‐derived probe, in which PNA forms a pseudocomplementary heteroduplex with inosine‐containing DNA or RNA, effectively discriminates a single‐nucleotide difference in a closely related group of sequences of single‐stranded DNA and/or RNA. The pseudocomplementary PNA heteroduplex is easily converted to a fluorescent probe that distinctively detects a member of highly homologous let‐7 microRNAs.     

Adsorption of CO and O2 on W2C(0001)

CO, O(2), and H(2) adsorption on a clean W(2)C(0001)√13×√13 R ± 13.9° reconstructed surface at room temperature (RT) were investigated using high-resolution electron energy loss spectroscopy (HREELS). The W(2)C(0001) adsorbs CO molecularly and adsorbs O(2) dissociatively, but does not adsorb H(2) at RT. In the CO adsorption system, two C-O stretching (antisymmetric CCO stretching) modes were found at 242.3 meV (1954 cm(-1)) and at 253.0 meV (2041 cm(-1)). The low-frequency site is occupied at first with subsequent conversion to the high-frequency site with increasing coverage. Additionally, a small peak was apparent at 104.5 meV (843 cm(-1)), and a middle peak at 50-51 meV (400-410 cm(-1)), which are assignable to a symmetric stretching mode and a hindered translational mode, respectively, of a CCO (ketenylidene) species. These observations are consistent with the CO adsorption model on top of the surface carbon. For oxygen adsorption, two adsorption states were found at 65.2-68.1 meV (526-549 cm(-1)) and 73.6 meV (594 cm(-1)): typical frequencies to oxygen adsorption on metal surfaces. Results suggest that atomic oxygen adsorption occurred on a threefold hollow site of the second W layer.     

Flame Emission Measurement of Alkali and Alkali Earth Metals Using Atomic Absorption Apparatus (2) Determination of Na in River Water

Flame Emission measurement of Na using an ordinary atomic absorption apparatus is performed in order to determine the concentration of Na in the surface water of the river Izumi, which is used for the irrigation of rice field in summer time.

The effect of acids and K on Na emission are studied and found to be eliminated when the proper conditions and positions of the flame is chosen. The recovery ratio of 8 ppm and 200 ppm Na added to the well water and river water, respectively, are found to be within 92–105%. This method can be applied to the routine analysis of Na in river water samples.     

Switchable Chemoselectivity of Reactive Intermediates Formation and Their Direct Use in A Flow Microreactor

A chemoselectivity switchable microflow reaction was developed to generate reactive and unstable intermediates. The switchable chemoselectivity of this reaction enables a selection for one of two different intermediates, an aryllithium or a benzyl lithium, at will from the same starting material. Starting from bromo-substituted styrenes, the aryllithium intermediates were converted to the substituted styrenes, whereas the benzyl lithium intermediates were engaged in an anionic polymerization. These chemoselectivity-switchable reactions can be integrated to produce polymers that cannot be formed during typical polymerization reactions.     

Ab initio calculation of chain structures in chalcohalide glasses

Local structure of Te₃X₂ (X = Cl, Br) chalcohalide glasses were studied using ab initio molecular orbital (MO) theory. The calculation results were compared with Mössbauer spectroscopic parameters in terms of electric-field gradient and electron density at each Te site. In addition, the existence of terminal bond –Te–X was examined. The MO analysis of Te-chain and Te-chain with Cl atoms within a picture of the frontier orbital theory elucidated that the localized orbital at –TeCl₂– site is important to form tellurium halide glass.     

Metal(II)–ligand molar ratio dependence of enantioseparation of tartaric acid by ligand exchange CE with Cu(II) and Ni(II)–D‐quinic acid systems

Enantioseparation of tartaric acid by ligand exchange CE with a Cu(II)–D ‐quinic acid system was studied. Racemic tartaric acid was enantioseparated by ligand exchange CE using BGEs containing relatively low Cu(II)–D ‐quinic acid molar ratios ranging from 1:1 to 1:3 and high molar ratios ranging from 1:8 to 1:12 but was not enantioseparated using BGEs with medium molar ratios ranging from 1:4 to 1:6. While the migration order of D ‐tartaric acid was prior to L ‐tartaric acid at the lower Cu(II)–D ‐quinic acid molar ratios, the enantiomer migration order was reversed at the higher molar ratios. These results were compared with those for Ni(II)–D ‐quinic acid system. The molar ratio dependence of enantiomer migration order can be attributed to a change in the coordination structure of Cu(II) ion with D ‐quinic acid.