Electrochemical deposition of cadmium selenide films and their properties: a review

This review gives brief information of experimental conditions employed by different researchers for deposition of cadmium selenide (CdSe) thin films. For the films synthesized at room temperature, films should be annealed and etched to increase the solar cell efficiency. A photoelectrochemical study revealed that values of fill factor and efficiency of CdSe thin films deposited on fluorine-doped tin oxide-coated glass substrates exhibited maximum value compared to the film deposited on titanium and stainless steel substrates. This review will be helpful to researchers entering in field to understand basics about the electrodeposition of CdSe and its development towards next-generation photovoltaics.     

Hydrogen Production by Steam Reforming of Ethanol Over Mesoporous Ni–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZrO<Subscript>2</Subscript> Catalysts

This review paper reports the recent progress concerning the application of nickel–alumina–zirconia based catalysts to the ethanol steam reforming for hydrogen production. Several series of mesoporous nickel–alumina–zirconia based catalysts were prepared by an epoxide-initiated sol–gel method. The first series comprised Ni–Al₂O₃–ZrO₂ xerogel catalysts with diverse Zr/Al molar ratios. Chemical species maintained a well-dispersed state, while catalyst acidity decreased with increasing Zr/Al molar ratio. An optimal amount of Zr (Zr/Al molar ratio of 0.2) was required to achieve the highest hydrogen yield. In the second series, Ni–Al₂O₃–ZrO₂ xerogel catalysts with different Ni content were examined. Reducibility and nickel surface area of the catalysts could be modulated by changing nickel content. Ni–Al₂O₃–ZrO₂ catalyst with 15 wt% of nickel content showed the highest nickel surface area and the best catalytic performance. In the catalysts where copper was introduced as an additive (Cu–Ni–Al₂O₃–ZrO₂), it was found that nickel dispersion, nickel surface area, and ethanol adsorption capacity were enhanced at an appropriate amount of copper introduction, leading to a promising catalytic activity. Ni–Sr–Al₂O₃–ZrO₂ catalysts prepared by changing drying method were tested as well. Textural properties of Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst produced from supercritical drying were enhanced when compared to those of xerogel catalyst produced from conventional drying. Nickel dispersion and nickel surface area were higher on Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst, which led to higher hydrogen yield and catalyst stability over Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst.     

Refractive index measurement by spectrally resolved interferometry using a femtosecond pulse laser

We describe a measurement method of refractive indices by way of spectrally resolved interferometry using a femtosecond pulse laser. The method is dispersion insensitive and requires no prior precise knowledge of the geometrical thickness of the specimen. Not only the group but also the phase refractive index can be determined over the wide spectral range covered by the optical comb of the femtosecond pulse laser in use.     

Spectral-domain optical coherence reflectometric sensor for highly sensitive molecular detection

We describe what we believe to be a novel use of spectral-domain optical coherence reflectometry (SD-OCR) for highly sensitive molecular detection in real time. The SD-OCR sensor allows identification of a sensor surface of interest in an OCR depth scan and monitoring the phase alteration due to molecular interaction at that surface with subnanometer optical thickness sensitivity. We present subfemtomole detection sensitivity for etching of SiO(2) molecules and demonstrate its application as a biosensor by measuring biotin-streptavidin binding in a microfluidic device.     

High-resolution solid-state NMR studies of poly(vinyl phosphonic acid) proton-conducting polymer: molecular structure and proton dynamics

The structure and the local proton mobility of poly(vinyl phosphonic acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P-OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P-OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P-OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to phosphonic acid anhydride and charged anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from "normal" phosphonic acid and phosphonic acid anhydride. 31P double-quantum NMR experiments reveal that there is no phase segregation between normal and phosphonic acid anhydride and the condensation reaction occurs randomly throughout the system. The formation of acid anhydride leads to a decrease in proton conductivity through two mechanisms, (1) decrease in the number of charge carriers and (2) blockage of charge transport pathways through immobilization of charge carriers together with a hindered reorientation of the anhydride group. Our results provide strong evidence for these mechanisms by demonstrating that the conductivity is greatly influenced by the presence of phosphonic acid anhydride.     

Thermal expansivity for sI and sII clathrate hydrates

Knowledge of thermal expansivity can aid in the understanding of both microscopic and macroscopic behavior of clathrate hydrates. Diffraction studies have shown that hydrate volume changes significantly (as much as 1.5% over 50 K) as a function of temperature. It has been demonstrated previously via statistical mechanics that a minor change in hydrate volume (e.g., a 1.5% change in volume or 0.5% change in lattice parameter) can lead to a major change in the predicted hydrate formation pressure (e.g., >15% at >100 MPa for methane). Because of this sensitivity, hydrate thermal expansivity measurements, for both Structures I and II with various guests, are needed help quantify volume distortions in hydrate lattices to ensure accurate hydrate phase equilibria predictions. In addition to macroscopic phase equilibria, the thermal expansion of different hydrates can give information about the interactions between the guest molecules and the host lattice. In this work, the hydrate lattice parameters for four Structure I (C2H6, CO2, 47% C2H6 + 53% CO2, and 85% CH4 + 15% CO2) and seven Structure II (C3H8, 60% CH4 + 40% C3H8, 30% C2H6 + 70% C3H8, 18% CO2 + 82% C3H8, 87.6% CH4 + 12.4% i-C4H10, 95% CH4 + 5% C5H10O, and a natural gas mixture) systems were measured as a function of temperature. The lattice parameter measurements were combined with existing literature values. Both sI and sII hydrates, with a few exceptions, had a common thermal expansivity, independent of hydrate guest. Many guest-dependent correlations for linear thermal expansivity have been proposed. However, we present two guest-independent, structure-dependent correlations for sI and sII lattices, which have been developed to express the normalized hydrate lattice parameters (and therefore volume) as a function of temperature.     

NMR study of methane + ethane structure I hydrate decomposition

The thermally activated decomposition of methane + ethane structure I hydrate was studied with use of 13C magic-angle spinning (MAS) NMR as a function of composition and temperature. The observed higher decomposition rate of large sI cages initially filled with ethane gas can be described in terms of a model where a distribution of sI unit cells exists such that a particular unit cell contains zero, one, or two methane molecules in the unit cell; this distribution of unit cells is combined to form the observed equilibrium composition. In this model, unit cells with zero methane molecules are the least stable and decompose more rapidly than those populated with one or two methane molecules leading to the observed overall faster decomposition rate of the large cages containing ethane molecules.     

Photoreactive immobilization of 11-(2,4-dinitro-5-fluorobenzene)undecenamide on a hydrogenated silicon (100) surface for protein immobilizations

Several nucleophiles such as proteins or poly(ethyleneimine) could be easily conjugated with a 11-(2,4-dinitro-5-fluorobenzene)undecenamide (DFUA) monolayer photochemically prepared on a silicon (100) surface.     

Protective effects of fustin, a flavonoid from Rhus verniciflua Stokes, on 6-hydroxydopamine-induced neuronal cell death

6-Hydroxydopamine (6-OHDA) is a neurotoxin and is commonly used to generate experimental models of Parkinson's disease (PD). In this study, we investigated the signaling molecules involved in the 6-OHDA-induced cell death using a neuronal catecholaminergic cell line (SK-N-SH cells), and the protective effect of fustin, a flavonoid from Rhus verniciflua Stokes, on 6-OHDA-induced neuronal death. 6-OHDA significantly increased levels of reactive oxygen species (ROS), intracellular Ca(2+) ([Ca(2+)](i)), and p38 phosphorylation. In addition, this ROS increase by 6-OHDA was reduced by pretreatment with N-acetylcysteine (NAC), a free radical scavenger, but not by bis-(o-aminophenoxy)-ethane-N,N,N,N-tetraacetic acid (BAPTA), a Ca(2+) chelator. However, the [Ca(2+)](i) increase induced by 6-OHDA was suppressed by NAC. Moreover, pretreatment with NAC or BAPTA significantly prevented the 6-OHDA-induced increases in p38 phosphorylation, Bax/Bcl-2 ratio, and caspase-3 activity. Although 6-OHDA-increased phosphorylation of p38 was prevented by NAC or BAPTA, inhibition of p38 by SB203580 did not suppress ROS, Bax/Bcl-2 ratio, or caspase-3 activity increases, and only partially prevented 6-OHDA-induced cell death, thus demonstrating that p38 activation is a component of a signaling pathway leading to the initiation of 6-OHDA-induced cell death, which acts in parallel with an ROS-Ca(2+)-Bcl-2-caspase-3 pathway. Moreover, fustin not only suppressed 6-OHDA-induced cell death in a concentration-dependent manner but also blocked 6-OHDA-induced increases in ROS, [Ca(2+)](i), Bax/Bcl-2 ratio, caspase-3 activity, and p38 phosphorylation. These results suggest that fustin exerts neuroprotection against 6-OHDA-induced cell death.