Extremely low-frequency phonon material and its temperature- and photo-induced switching effects

Atomic vibrations due to stretching or bending modes cause optical phonon modes in the solid phase. These optical phonon modes typically lie in the frequency range of 10² to 10⁴ cm⁻¹. How much can the frequency of optical phonon modes be lowered? Herein we show an extremely low-frequency optical phonon mode of 19 cm⁻¹ (0.58 THz) in a Rb-intercalated two-dimensional cyanide-bridged Co–W bimetal assembly. This ultralow frequency is attributed to a millefeuille-like structure where Rb ions are very softly sandwiched between the two-dimensional metal–organic framework, and the Rb ions slowly vibrate between the layers. Furthermore, we demonstrate temperature-induced and photo-induced switching of this low-frequency phonon mode. Such an external-stimulation-controllable sub-terahertz (sub-THz) phonon crystal, which has not been reported before, should be useful in devices and absorbers for high-speed wireless communications such as beyond 5G or THz communication systems.

Extremely low-frequency optical phonon mode in Rb-intercalated two-dimensional cyanide-bridged Co–W bimetal assembly and its temperature- and photo-induced switching effect.     

Sequential injection chemiluminescence immunoassay for anionic surfactants using magnetic microbeads immobilized with an antibody

A rapid and sensitive immunoassay for the determination of linear alkylbenzene sulfonates (LAS) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a neodymium magnet. Magnetic beads, to which an anti-LAS monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by means of a neodymium magnet and adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-LAS monoclonal antibody on the magnetic beads and the LAS sample and horseradish peroxidase (HRP)-labeled LAS, and was based on the subsequent chemiluminscence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The anti-LAS antibody was immobilized on the beads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the neodymium magnet, an LAS solution containing HRP-labeled LAS at constant concentration and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the flow cell by collecting the emitted light with a lens. A typical sigmoid calibration curve was obtained, when the logarithm of the concentration of LAS was plotted against the chemiluminescence intensity using various concentrations of standard LAS samples (0-500 ppb) under optimum conditions. The time required for analysis is less than 15 min.     

Improvement in Tensile Strength and Water Repellency of Paper after Treatment with Methyltrimethoxysilane Oligomer Using Titanium Butoxide as a Catalyst

The improvement in the tensile strength and water repellency of paper after treatment with a 2-propanol solution of a methyltrimethoxysilane (MTMS) oligomer was studied using filter paper. Titanium butoxide introduced in the solution as a catalyst effectively reacted with the MTMS oligomer, and a Si–O–Ti bond was generated inside the paper. The tensile strength of the paper was remarkably improved by this treatment of impregnation and polymerization of the MTMS oligomer. It was speculated that the reaction proceeded by consuming water that existed among the cellulose fibers by hydrogen bonding, because there was little difference in the tensile strength between the paper treated in air and the paper treated in a dry box. The methoxy groups in the MTMS oligomer demonstrated their good ability of making a three-dimensional network, and at the same time, the methyl groups in the oligomer showed their excellent water repellency. As a result, the treated paper had a good tensile strength even under wet conditions.     

Certification of methylmercury in cod fish tissue certified reference material by species-specific isotope dilution mass spectrometric analysis

A new cod fish tissue certified reference material, NMIJ CRM 7402-a, for methylmercury analysis was certified by the National Metrological Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Cod fish was collected from the sea close to Japan. The cod muscle was powdered by freeze-pulverization and was placed into 600 glass bottles (10 g each), which were sterilized with γ-ray irradiation. The certification was carried out using species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID–GC–ICPMS), where ²⁰²Hg-enriched methylmercury (MeHg) was used as the spike compound. In order to avoid any possible analytical biases caused by nonquantitative extraction, degradation and/or formation of MeHg in sample preparations, two different extraction methods (KOH/methanol and HCl/methanol extractions) were performed, and one of these extraction methods utilized two different derivatization methods (ethylation and phenylation). A double ID method was adopted to minimize the uncertainty arising from the analyses. In order to ensure not only the reliability of the analytical results but also traceability to SI units, the standard solution of MeHg used for the reverse-ID was prepared from high-purity MeHg chloride and was carefully assayed as follows: the total mercury was determined by ID–ICPMS following aqua regia digestion, and the ratio of Hg as MeHg to the total Hg content was estimated by GC–ICPMS. The certified value given for MeHg is 0.58 ± 0.02 mg kg⁻¹ as Hg. Figure NMIJ CRM 7402-a: cod fish tissue for MeHg analysis     

Single Crystal of a Prussian Blue Analog based on Rubidium Manganese Hexacyanoferrate

A dark brown single crystal of rubidium manganese hexacyanoferrate, Rb_0.61Mn[Fe(CN)₆]_0.87·1.7H₂O, was obtained by the slow diffusion method. X‐ray single crystal analysis showed that this compound crystallized in the cubic system of space group with cell constants of a = b = c = 10.5354(4) Å, Z = 4, and R₁ = 0.0449. The CN groups bridge octahedral FeC₆ and MnN_0.87O_0.13. Rb and non‐coordinated water (so‐called zeolitic water) exist in the interstitial sites of the cubic lattice.     

Spin-probe ESR study on the entrapment of organic solutes by the nanochannel of MCM-41 in benzene

An ESR study has been made on the adsorption of three types of aminoxyl radicals with different substituent groups in the nanochannel of MCM-41 in benzene. In the suspensions of MCM-41, all the aminoxyl radicals, usually called as spin probes, show the ESR spectra composed of two signals: the main broader one from the spin probes trapped in the nanochannel, and a sharp minor signal from those in the bulk. The spin probes adsorbed in the nanochannel retain considerable mobility especially at higher temperatures over 300 K. When fumed silica, having a surface structure similar to that of MCM-41, is employed, on the other hand, the relatively hydrophobic spin probe mainly remains in the bulk, but the hydrophilic one is mostly adsorbed and immobilized rigidly. From these results, the adsorption by the MCM-41 nanochannel in benzene is characterized by medium selectivity and considerable motional allowance to the adsorbate molecule. The mobility of the spin probe in the MCM-41 nanochannel increases and the adsorption efficiency decreases by either of the following changes made to the system: (a) increasing the channel diameter, (b) increasing the hydrophobicity of the spin probe, (c) adding a small amount of 2-propanol in the solution, (d) methylation of the surface OH groups of the nanochannel, and (e) elevating the system temperature. A model of this special type of adsorption has been proposed on the basis of the thermodynamic parameters and the ESR spectra for the modified systems including those with different solvents.     

Observation of ferroelectricity in paramagnetic copper octacyanomolybdate

We report the observation of ferroelectricity in a copper octacyanomolybdate-based paramagnet, Cu(2)[Mo(CN)(8)].8H(2)O (Cu(II), S = (1)/(2); Mo(IV), S = 0). This compound has a freezing point for the fixation of hydrogen bonding at 150 K. Around this temperature, an enhancement in the ferroelectricity and an increase in the dielectric constant are observed. The ferroelectricity of this system is classified into amorphous ferroelectrics; i.e., the electric poling effect induces an electric polarization. The electric polarization is maintained by the structural local disorder of hydrogen bonding and the three-dimensional CN network. In this ferroelectricity, the crystal structure is a polar group of C(infinityv) after application of an electric field.     

In situ forced hydrolysis-assisted fabrication and photo-induced electrical property in sensor of ZnO nanoarrays

ZnO nanowhiskers are successfully fabricated on an anhydrous zinc acetate coated substrate by its in situ forced hydrolysis at the initial stage without pre-existing ZnO seeds or catalyst. HR-TEM clarified the formation mechanism that in situ forced hydrolysis of an anhydrous zinc acetate layer to ZnO nanocrystals at the initial stage promoted growth of ZnO nanowhiskers by heterogeneous nucleation and growth. ZnO nanowhiskers films show high transmittance over 80% in the visible range and bandgap energy of 3.29 eV. Porous semiconductor ZnO films show good photo-induced electrical properties after various concentrations of DNA molecules labeled with photoactive dye molecules were adsorbed. In situ forced hydrolysis-assisted technique at low temperature can be useful for the fabrication of optoelectronic devices with low cost and without using expensive catalyst.     

Constructing highly conducting metal-metal bonded solids by electrocrystallization of [Pt(II)2(RCS2)4] (RCS2(-) = dithiocarboxylato, R = methyl or ethyl)

Partially oxidized one-dimensional (1D) Pt-Pt chain compounds [Pt2(MeCS2)4]4ClO4.5PhCN (1) and [Pt2(EtCS2)4]5(ClO4)2 (2) were synthesized by electrocrystallization of diplatinum(II,II) complexes from different solvents. 1 and 2 consist of 1D Pt-Pt chains of stacked Pt-Pt dimers with short interdimer S...S contacts. Depending on the number of ClO4- per dimer and their positions, 1 forms a regular stack of Pt-Pt dimers, whereas 2 forms pentamer of dimers in the 1D chain. 1 exhibits high electrical conductivity (4.2-8.0 S cm-1) at 300 K and metallic behavior above 125 K. 2 is a semiconductor. 1 exhibits almost temperature independent magnetic susceptibility (ca. 1.1 x 10-4 emu mol-1) which is attributed to Pauli paramagnetism, whereas the spin degree of freedom in 2 has been lost. Although the basic structures are closely related, they exhibited different solid-state properties that depend on the valence state of the platinum atoms and the periodicity within the 1D chain.     

Synthesis and antiviral activities of N-mono- and/or N,N'-di-carbamoyl and acyl derivatives of symmetrical diamines

N-carbamoyl and N-acyl diamine derivatives were synthesized from symmetrical diamines by their addition to iso(thio)cyanates, cleavage reaction of acid anhydride, or N-acylation by acyl chloride. (1R,2R)-1,2-Diaminocyclohexane [(1R,2R)-1], meso-1,2-diaminocyclohexane (meso-1), (1R,2R)-1,2-diphenylethylenediamine [(1R,2R)-3], or meso-1,2-diphenylethylenediamine (meso-3) were used as the starting symmetrical diamines. The target compounds synthesized herein were evaluated for antiviral activity with herpes simplex virus type 1 (HSV-1). A few derivatives of 1,2-diaminocyclohexane [(1R,2R)-7aa and cis-7b] with adamantyl group(s) showed significant antiviral activity (EC(50)=16.0, 27.0 microg/ml).