Experimental Evaluation of the Optical Properties of Porous Silica/Carbon Composite Particles

Light scattering by porous spheroidal silica and several silica/carbon composite particles having different carbon contents was systematically investigated using a laser particle counter coupled with a pulse height analyzer (LPC-PHA). A new and simple method for the measurements of the effective complex refractive index of silica/carbon composite particles using a conventional LPC-PHA system and a differential mobility analyzer was introduced and tested. Challenge particles, from pure silica to silica/carbon compounds having a gradually increasing porous structure, were prepared by spray-drying methods for use in testing of the inversion method. By representing the deviation of the real part of the refractive index of a porous silica particle versus the size on a topographical map, the inversion method for the determination of the real part of the refractive indices was found to have a satisfactory precision. Furthermore, the method can be applied to the measurement of the complex refractive index of silica/carbon composite particles by extending the best fitting method to complex refractive indices. The effective complex refractive index of silica/carbon composite particles as a function of their carbon content is reported. Both the real and imaginary parts of the complex refractive index were increased with increasing carbon content of the composite particles.     

Molecular dynamics studies on the structures of polymer electrolyte membranes and diffusion mechanism of protons and small molecules

We performed a series of molecular dynamics (MD) simulations on Nafion^® membranes containing various quantities of H₂O and CH₃OH. The simulations afforded diverse nanoscale phase-separated structures, such as clusters, channels, and cluster–channels. The calculated cluster–channel structure qualitatively agrees with the experimental results of X-ray diffraction studies. We also investigated the diffusion mechanisms for H₂O, protons, CH₃OH, H₂, and O₂ in these membranes. To reproduce the hopping transfer of protons, we employed a semi-classical MD approach using the empirical valence bond method. The estimated diffusion coefficients of H₂O and proton in the membranes significantly depended on the H₂O content, and these values showed qualitatively good agreement with the experimental results. The diffusion coefficient of proton in H₂O-rich membranes was much larger than that of H₂O, and the proton mainly formed H₅O₂⁺ complex. Furthermore, the simulation results indicate that the majority of CH₃OH permeates through the H₂O clusters, and the majority of H₂ and O₂ permeates through the hydrophobic region of the membrane.     

Changes in the drift and the settlement of the freshwater mussel Limnoperna fortunei along a headrace channel

The nuisance species Limnoperna fortunei is a freshwater mussel whose infestations have harmed water intake facilities, such as water supply systems. We investigated the changes in the drift and the settlement of L. fortunei along a headrace channel. The densities of the drift and the settlement both decreased dramatically with the downstream distance from the L. fortunei source (a reservoir). In comparison with larval densities in the reservoir, drift densities decreased by 10 to 25% at 0.5 km downstream from the reservoir, and were less than 2% at sites more than 4.8 km downstream. Although larval densities at midnight (0:00-2:00) were approximately 1.5 times higher than those at noon (12:00-14:00) in a shallow layer (3 m depth) of the reservoir, we found no diurnal variation of drift densities in the headrace channel. Settlement densities at the site nearest the intake gate were much higher than those of the other sites further downstream in the headrace channel. The L. fortunei adult population in the channel could reduce drift individuals by attracting the larva. The attraction probably induces the massive aggregation at the location of the channel immediately below the drift source, resulting in biofouling.     

Influence of Ga2O3 addition on transparent conductive oxide films of In2O3-ZnO

Influence of incorporation of Ga in amorphous In-Zn-O transparent conductive oxide films was investigated as a function of Zn/(Zn + In). For In-Zn-O films with no Ga₂O₃, the range of Zn/(Zn + In) ratio where the amorphous phase appears became narrow at a substrate temperature of 250 °C. With increasing Ga₂O₃ quantity, amorphous films were obtained even at a high substrate temperature of 250 °C in a wider range of Zn/(Zn + In) than that of In-Zn-O films with no Ga₂O₃. This means that the trend of crystallization at higher substrate temperature was disturbed with additional Ga incorporation. For the film deposited from ZnO:Ga (Ga₂O₃: 4.5-7.5 wt%) and In₂O₃ targets, we obtained a resistivity of 2.8 × 10⁻⁴ Ω cm, nearly the same value as that for an In-Zn-O film with no Ga₂O₃. The addition of more than 7.5 wt% Ga₂O₃ induced a widening of the optical band gap.     

Synthesis of 1,3-dicapryloyl-2-docosahexaenoylglycerol by a combination of nonselective and <Emphasis Type="Italic">sn</Emphasis>-1,3-selective lipase reactions

A two-step consecutive synthetic method for the production of symmetrical, structured lipids by a combination of nonselective and sn-1,3 regioselective ester exchange reactions was investigated. In the first step, TAG with unspecifically substituted DHA were obtained by reacting tricapryloylglycerol (CCC) with ethyl docosahexanoate (EtDHA) using the lipase QLM (from Alcaligenes sp.), followed by removing the ethyl ester and CCC by molecular distillation. In the second step, sn-1,3 regioselective ester exchange was achieved by reacting the resulting TAG with ethyl caprylate (EtC) using the immobilized lipase Novozyme 435 (Candida antarctica lipase), followed by distillation of the ethyl ester and CCC to give sn-1,3-dicapryloyl-sn-2-docosahexaenoylglycerol (CDC). The acylglycerol composition of CDC was analyzed by GLC, which showed that the content of dicapryloyl-docosahexaenoylglycerols (2CD) in the product was 76.4%, and that the ratio of CDC to sn-1,2-dicapryloyl-sn-3-docosahexaenoylglycerol contained in 2CD was 82.7∶17.3 (%). The distillates CCC, EtDHA, and EtC could be recycled repeatedly to produce CDC as the substrate for the consecutive ester exchange reaction. In addition, separation of CCC and EtDHA was unnecessary for reuse. The present method is considered to meet the requirements for industrial utilization, in which simplicity in scaleup, high yields, compact reaction system, and minimal formation of by-products are important factors.     

Preparation of Nickel Powders by Spray Pyrolysis of Nickel Formate

The preparation of nickel powders by the ultrasonic spray pyrolysis of Ni(HCOO)₂ was studied. Phase-pure nickel powder was obtained at as low as 350°C. HCOOH was a reducing source for nickel formation. Moreover, metallic nickel was obtained at a residence time as short as 0.1 s at 600°C. A broad range of particle morphologies, which included agglomerated nanoparticles, nonagglomerated submicrometer particles, hollow particles, and spherical dense particles, were obtained from Ni(HCOO)₂ pyrolysis and were shown to depend on the precursor solution and the operating condition.     

Effect of solvent evaporation rate on surface composition in fluoro‐copolymer/acrylate‐copolymer blend films

The relationship between the surface composition and the rate of solvent evaporation (R) in blend films of poly(vinylidene fluoride‐co‐hexafluoroacetone) (P(VDF‐HFA)) and poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate) (P(2EHA‐AA‐VAc)) has been investigated. P(VDF‐HFA), a low‐surface tension component, was concentrated on the surface when R was relatively high. In contrast, when R was relatively low, P(2EHA‐AA‐VAc), a low‐density component, was concentrated on the surface. Therefore, it is speculated that the factors dominating surface enrichment in polymer blends were changed from surface tension differences to density differences between the components when R was decreased. In addition, the affinity between components and substrate strongly affects the dominant factors determining the surface composition. © 2001 Society of Chemical Industry     

Synthesis and applications of silicone oil–soluble fluoroalkyl end‐capped cooligomers

Fluoroalkyl end‐capped cooligomers containing polydimethylsiloxane and polyoxyethylene segments were prepared under very mild conditions by the cooligomerizations of fluoroalkanoyl peroxides with methacrylate monomers containing the corresponding segments and comonomers such as dimethylacrylamide and acryloylmorpholine. These obtained fluorinated cooligomers exhibited amphipathic characteristics and became soluble in water and common organic solvents. In particular interest, fluoroalkyl end‐capped cooligomers containing polyoxyethylene units were soluble not only in poly(methylphenylsiloxane) (silicone oil) but also in water, including common organic solvents except for hexane. Additionally, these fluorinated cooligomers were able to reduce the surface tension of water and m‐xylene quite effectively, to around 15 and 20 mN/m levels, respectively. In these fluorinated cooligomers, fluoroalkyl end‐capped acryloylmorpholine cooligomers containing polyoxyethylene segments were applicable as a novel emulsifying agent against water and silicone oil. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1467–1476, 2005     

Interference-based electrochemical biosensor for the measurement of the concentration and isomer ratio of urocanic acid

Urocanic acid (UCA) is known to be synthesized as the trans isomer (trans-UCA) in the skin, and trans-UCA is transformed by UV light to the cis isomer (cis-UCA), which may be involved in photoimmunosuppression. An electrochemical method has been developed for the measurement of the concentration and isomer ratio of UCA. A heme peptide-modified electrode (HP electrode) reduces hydrogen peroxide at +150 mV vs Ag/AgCl, and the reduction current is inhibited by UCA. Since cis-UCA is a stronger inhibitor than trans-UCA, irradiation of a sample solution with UV light increases the percent inhibition. The concentration and isomer ratio of UCA in the sample solution can be estimated from the values of percent inhibition before and after the UV irradiation.     

Strong metal-support interactions (SMSIs) between Pt and Ti3+ on Pt/TiOx nanoparticles for enhanced degradation of organic pollutant

In this work, Pt nanoparticles were deposited onto the surface of Magnéli phase titanium suboxide (TiO_x) nanoparticles using a microwave-assisted deposition method. The effect of different concentrations of Pt nanoparticles was investigated to evaluate the strong metal-support interactions (SMSIs) between Pt and TiO_x based on their performance for the degradation of organic pollutant molecules. The adsorption and catalytic performance of the as-synthesized Pt/TiO_x nanoparticles were evaluated with respect to the degradation of rhodamine B (RhB) molecules without any external energy source. The Pt/TiO_x nanoparticles with Pt loading at 10 wt% (10%Pt/TiO_x) exhibited a remarkable performance. The XPS, CV, and FTIR analyses confirmed the presence of RhB degradation reactions under dark condition. This remarkable performance of the Pt/TiO_x nanoparticles was attributed to the SMSIs between Pt and Ti³⁺ atoms, which improves their performance compared with Pt/TiO₂ nanoparticles, and high density of active sites due to their nanometer size, which results in better performance compared with that of Pt/TiO_x submicron particles.