We analyzed the complex dielectric and Raman spectra of hydrogen-bond liquids in the microwave to terahertz frequency range. As for water and methanol, the high-frequency component of the dielectric spectrum, i.e., the small deviation from the principal Debye relaxation, clearly corresponds to the Raman spectrum. This indicates that the cooperative relaxation, accompanied by huge polarization fluctuation, is virtually not Raman active, whereas the faster processes reflect common microscopic dynamics. For ethylene glycol, the shape of the Raman spectrum also resembles that of the high-frequency deviation of the dielectric spectrum, but, additionally, a weak manifestation of the cooperative relaxation arising from quadrupolar conformers is detected.

Platinum (Pt) is widely used as battery electrodes, catalysts for chemicals, and catalysts for exhaust gas decomposition in industries. Increasing need and very limited supply of rare Pt is a serious problem in the world. Here, we propose new synthetic way for reducing the use of Pt in a catalytic system by increasing the surface area and modifying the Pt surface structure. Several types of mesoporous Pt films with different pore sizes ranging from 5 to 30 nm are prepared by electrochemical plating in aqueous surfactant solutions. The mesopore walls are composed of connected Pt nanoparticles with around 3 nm in diameter. The Pt atomic crystallinity is coherently extending across over several Pt nanoparticles, showing a large number of atomic steps, which can accelerate methanol oxidation reaction. As a result of a high surface area and unique Pt surface, our mesoporous Pt film exhibits high potentiality as a superior electrocatalyst.

One-dimensional metallic nanostructures, particularly those composed of noble metals, have sparked great scientific interest for practical applications, owing to their uniquely anisotropic structure. [1] Recent advances in energy conversion materials have shown that 1D materials are particularly effective as electrocatalysts for the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) at low costs. [2] The facile synthesis of 1D Pt nanocatalysts (e.g., nanorods, [3] nanowires, [4] nanotubes, [5] and others [6] ) with noteworthy enhanced electrocatalytic activity and durability is becoming increasingly important.On the other hand, the formation of well-defined nano/ mesoporous structures [7] of metals affords electrocatalysts showing a superior performance because of their high porosity, large area per unit volume, and excellent activitystructure relationship. Therefore, the successful synthesis of 1D mesoporous Pt motifs can be expected to be a new direction in the fabrication of superior electrocatalysts. The traditional hard-templating method, which is widely used to synthesize mesoporous carbon materials, [8] metal oxides, [9] and metals, [10] cannot easily be used for the synthesis of 1D mesoporous metal motifs, because this method involves several steps: the formation of an original template followed by deposition of metals within the mesopores and subsequent removal of the template. Lyotropic liquid crystals (LLCs) made of highly concentrated surfactants have also been used as soft templates. [11] However, due to the high viscosity of the LLCs, it is not so easy to deposit selectively metals in the target area. The method using LLCs cannot be applied as a general electrochemical method for shape-controlled synthesis of mesoporous metals. As another way, the alloydealloying approach, in which a less noble metal is selectively dissolved from a bimetallic alloy, is an attractive and much used strategy to synthesize porous metals. [12] However, it is hard to control the sizes of the mesopores and to construct robust mesopore walls.Herein, we report a general "all-wet electrochemical approach" to synthesize novel self-supported 1D Pt nanorods (NRs) with a high density of mesopores (which are denoted as "mesoporous Pt nanorods, MPNRs") by using the assembly of micelles [13] in the confined space of a polycarbonate (PC) membrane. The MPNRs with various aspect ratios can be synthesized by simply controlling the electrodeposition times. The fabrication procedure of 1D MPNRs is schematically illustrated in Figure 1. A Pt thin film serving as conductive layer was deposited on one side of the PC membrane with a pore size of 50 nm (see Figure S1 in the Supporting Information). The electrolyte solution containing K 2 PtCl 4 and 1.0 wt % Brij 58 (C 16 H 33 (OCH 2 CH 2 ) 20 OH) was used to prepare 1D MPNRs at a constant potential of À0.2 V vs. Ag/ AgCl at room temperature. After the electrodeposition, the PC membranes were soaked in NaOH and ethanol solutions to dissolve the PC membranes and the surfa...

We have determined the complex dielectric spectra of ethanol/water mixtures at 25 °C for the nine molar fractions of ethanol, X EA = 0.04, 0.08, 0.11, 0.18, 0.3, 0.5, 0.7, 0.9, and 1.0, in the frequency range 0.1 ≤ ν/GHz ≤ 89 using TDR in 0.1 ≤ ν/GHz ≤ 25 and waveguide interferometers in 13 ≤ ν/GHz ≤ 89. At 0.3 ≤ X EA ≤ 1.0, a three-step relaxation model turns out to be most appropriate. Besides a Cole−Cole relaxation for the dominating low-frequency process (j = 1), assigned to the cooperative dynamics of the H-bond system, which exhibits a pronounced increase of its relaxation time, τ 1, when going from X EA = 0 to 1, two additional Debye terms (j = 2 and 3) with the relaxation times of τ2 ≈ 10 ps and τ3 ≈ 1−2 ps are required to reproduce the high-frequency part of the spectrum. In view of the well-established relaxation mechanisms of pure liquids, these high-frequency processes can be validly assigned to the motion of singly H-bonded ethanol monomers at the ends of the chain structure (j = 2) and the flipping motion of free OH (j = 3), respectively. The unusual increase of the amplitude Δε2 with decreasing X EA in ∼0.5 ≤ X EA ≤ 1.0 suggests insertion of water molecules into the zigzag structure of winding H-bonded ethanol chains resulting in a reduction of the average chain length and an increase of the number of end-standing ethanol molecules that can contribute to the τ2-mode. At X EA < 0.3, τ 1 rapidly approaches τ 2 and Δε2 → 0, so that the intermediate ethanol monomer process (j = 2) becomes inseparable while the fast switching process with τ3 ≈ 1 ps can always be resolved. The analysis of the effective dipolar correlation factor, g eff, revealed that the parallel arrangement of dipole vectors of ethanol molecules is fairly disturbed by the presence of a small amount of water. Water has a strong perturbation effect on the ethanol hydrogen-bonding chain structure in the ethanol-rich region of 0.3 ≤ X EA ≤ 1.0.

Dielectric relaxation measurements on the methanol-water mixtures for the entire concentration range were carried out using time domain reflectometry in the frequency range from 500 MHz to 25 GHz at 20, 25, and 30°C. The excess partial molar activation free energy, enthalpy, and entropy for methanol, ⌬G MA E , ⌬H MA E , and ⌬S MA E , and those for water, ⌬G W E , ⌬H W E , and ⌬S W E , were calculated from accurately measured concentration and temperature dependence of the dielectric relaxation time of the mixtures. The behavior of the excess partial molar quantities in the regions below and above X ͑molar fraction of methanol͒ ϳ0.3 are quite different from each other. In a water-rich region, ⌬H MA E and ⌬S MA E exhibit two maxima at Xϳ0.045 and Xϳ0.12, which is clearly attributed to structural enhancement of the hydrogen bond network of water, the so-called hydrophobic hydration. Appearance of two maxima in ⌬H MA E and ⌬S MA E implies that water molecules surround methanol molecules in qualitatively different manners around the two points. In the concentrated region of Xу0.3, the values of ⌬H MA E and ⌬S MA E become nearly zero, which means that methanol molecules in the mixtures find themselves in not a very different environment from that in pure methanol, associated and forming chainlike clusters. Water molecules seem to exothermically attach to the hydrophilic site of methanol.

Dielectric relaxation measurements on the ethanol–water mixture for the entire concentration range in very small increments were carried out using TDR in the frequency range from 300 MHz to 25 GHz at 20 °C, 22.5 °C, and 25 °C. The activation enthalpy ΔH and entropy ΔS for the mixtures were separated from the activation free energy ΔG, and hence the excess partial molar activation free energy, enthalpy, and entropy for ethanol, ΔGEAE, ΔHEAE, and ΔSEAE, and those for water, ΔGWE, ΔHWE, and ΔSWE were calculated. The concentration dependence of these partial molar quantities shows the existence of two regions bound at X (molar fraction of ethanol) ∼0.18. In the water-rich region of X&lt;0.1, ΔHEAE and ΔSEAE take large positive values, exhibiting two sharp maxima at X=0.04 and X=0.08, which is clearly attributed to structural enhancement of the hydrogen bond network of water by ethanol, the so-called hydrophobic hydration. From a standpoint of dynamics, mixing schemes of ethanol and water around the two points X=0.04 and X=0.08 seem to be qualitatively different. On the other hand, in the region of X&gt;0.18, the values of ΔHEAE and ΔSEAE take nearly zero. This means that ethanol molecules in the mixtures are in almost the same environment as those are in pure ethanol, forming chainlike clusters surrounded or exothermically attached to by water molecules.

Dielectric relaxation measurements on water solutions of ethylene glycol 200 and 400, (degree of polymerization N=4 and 9) in entire concentration region were carried out using a time domain reflectometry at 25 °C in the frequency range from 300 MHz to 20 GHz. For all the samples, only one dielectric loss peak was observed in this frequency range. Plots of the relaxation strength and logarithm of the relaxation time calculated from apparent peak frequency of dielectric loss curves against monomer unit molar fraction of ethylene glycol X give straight lines in the region of 0&lt;X&lt;0.35 for N=4, and 0&lt;X&lt;0.37 for N=9. Shapes of dispersion and absorption curves exhibit critical change at the concentration X≈0.35 for N=4 and X≈0.37 for N=9, corresponding to the ratio of one ether oxygen and 1.7 water. Analysis of these phenomena indicates that hydration complex of one ether oxygen and 1.7 water is formed, and the 1:1.7 complex behaves as one kind of component corresponding to 2.7(=1+1.7) waterlike molecules in the solution. It is suggested that ether oxygen can be inserted into water structure by replacing water oxygen. This hydration mechanism makes water structure stable. Ethylene glycol dissolves in water without much perturbation to water structure.

Different from conventional nonionic poly(oxyethylene) surfactants, poly(oxyethylene) cholesteryl ethers, ChEO n , possess a bulky and nonflexible hydrophobic part and form a variety of self-organized structures in water. We investigated the phase behavior and the micellar structures in the water/ChEO15 and water/ChEO10 systems by means of visual observation, rheometry, small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), dielectric relaxation spectroscopy (DRS), and densimetry. We found that in the water/ChEO15 system, aqueous micellar (Wm), discontinuous micellar cubic (I1) with Fd3m space group, hexagonal (H1), rectangular ribbon (R1), and lamellar (Lα) phases are formed, whereas Wm, unknown, R1, defected lamellar ( ), and Lα phases are produced in the water/ChEO10 system at ambient temperatures. Compared with a conventional aqueous nonionic surfactant system, the intermediate R1 phase region is incredibly wide. As for the water/ChEO15 system, with increasing water content, the packing parameter, P, in the R1 region is gradually decreased, finally converging to 1/2 at W s ∼ 0.58, indicative of the formation of the H1 phase. The R1 phase acts as a “distorted” hexagonal phase in the system. However, in the water/ChEO10 system, upon reduction of W S, P shows a steplike increase and the maximum value ∼0.67 at W S ∼ 0.7, just corresponding to the threshold of discontinuous and bicontinuous structures. After that, P is decreased with decreasing W S and unknown phase that cannot be indexed to any known space group for liquid crystalline phases emerges at W S ∼ 0.5. The GIFT analysis of the SAXS data for the Wm solution indicates that spherical micelles are present in the water/ChEO15 system in an ambient temperature range, but ChEO10 forms a short-rod micelle in water. With increasing temperature, rodlike micelles appear to be grown and a viscoelastic micellar phase is formed in water/ChEO10 system. The hydration number for each oxyethylene unit is evaluated as ∼4 by DRS, which gives a consistent explanation for the concentration dependence of the apparent hydrodynamic radius in the Wm phase obtained by DLS. Hydrated water molecules should be regarded as a constituent of the micelles. The majority of these features of novel phase behavior in the water/ChEO n systems are based on a nonflexible and bulky hydrophobic part of ChEO n .