Photoinduced hydrophilicity of titanium dioxide thin films prepared by cathodic electrodeposition

Crystal structure and microstructural properties of titanium dioxide thin films prepared by cathodic electrodeposition on indium-tin-oxide coated glass substrates from aqueous peroxo-titanium complex solutions have been investigated as a function of sintering temperature (25-500 °C) for the first time. We have noticed pronounced photoinduced hydrophilicity for such thin films on exposure to ultraviolet (UV) light illumination. It was observed that all the films, irrespective of their crystalline nature (amorphous and crystalline), display transformation from hydrophobic to super-hydrophilic behavior upon UV illumination. This observation can be correlated with typical nanoporous morphology of electrodeposited TiO₂ films.     

Room‐Temperature Synthesis of Porous Nanoparticulate TiO2 Films for Flexible Dye‐Sensitized Solar Cells

A novel room‐temperature method for the preparation of porous TiO₂ films with high performance in dye‐sensitized solar cells (DSSCs) has been developed. In this method a small amount of Ti^IV tetraisopropoxide (TTIP) is added to an ethanolic paste of TiO₂ nanoparticles, where it hydrolyzes in situ and connects the TiO₂ particles to form a homogenous and mechanically stable film of up to 10 μm thickness without crack formation. Residual organics originating from the TTIP were removed by UV–ozone treatment of the films, leading to a remarkable improvement of the cell efficiency. Intensity‐modulated photocurrent/voltage spectroscopy (IMPS/IMVS) showed that the main effect of the UV–ozone treatment is to suppress the recombination of photogenerated electrons, thereby extending their lifetime. The efficiency was further increased by preheating the TiO₂ nanoparticles before the paste preparation to remove contaminants originating from the preparation process of the particles. Solar‐to‐electric energy conversion efficiencies of 4.00 and 3.27 % have been achieved for cells with conductive glass and plastic film substrates, respectively, under illumination with AM 1.5 (100 mW cm^–2) simulated sunlight.     

The effect of casting solvent on the sorption and diffusion of water vapor in poly(γ-methyl L-glutamate)

Water vapor permeability of poly(γ-methyl L -glutamate) (PMLG) membranes prepared by using dichloroethane, trifluoroacetic acid, and formic acid as solvents was studied. The membranes prepared by casting dichloroethane and trifluoroacetic acid solutions of the polymer, designated as PMLG–DCE and PMLG–TFA, respectivley, had α-helical structures according to infrared absorption spectra, while the membranes prepared by allowing the PMLG–TFA membranes to swell in formic acid, designated as PMLG–FA, had mainly a β-sheet structure. The amounts of water sorbed by PMLG–DCE, PMLG–TFA, and PMLG–FA increased in that order. The isotherms of PMLG–TFA and PMLG–FA were sigmoidal-shaped isotherms, and the heat of sorption for PMLG–TFA and PMLG–FA was larger than that for PMLG–DCE, which suggested the presence of the sorption sites. The diffusion coefficients of water for PMLG–DCE increased and then decreased with increasing concentration. On the other hand, the diffusion coefficients for PMLG–TFA and PMLG–FA increased with concentration. The activation energies of diffusion for PMLG–DCE, PMLG–TFA, and PMLG–FA increased in that order. These results were discussed in connection with the molecular conformations of poly(γ-methyl L -glutamate) in the membranes. From these results, it is assumed that the molecular chains in the PMLG–TFA membranes are mainly in α-helical and partly random-coil conformations.     

π‐Conjugated Oligothiophene‐Based Polycatenar Liquid Crystals: Self‐Organization and Photoconductive,Luminescent, and Redox Properties

A series of liquid‐crystalline (LC) π‐ ‐conjugated oligothiophenes bearing three or two alkoxy chains at their extremities has been designed and synthesized. These polycatenar oligothiophenes form various LC nanostructures including smectic, columnar, and micellar cubic phases. These properties depend on the number and length of the terminal alkoxy chains. The hole mobilities for the oligothiophenes have been measured. The layered smectic and columnar structures are capable of transporting holes, leading to mobilities of up to 0.01 cm² V^?1 s^?1. The columnar LC assemblies have also been explored to produce linearly polarized light‐emission. Fine red polarized fluorescence is observed from a uniaxially aligned film of the oligothiophenes. The redox properties of the oligothiophenes both in solutions and in films have been examined. The oligothiophenes exhibit electrochromism upon applying an oxidative potential. The present design strategy is useful for fabricating a variety of functional electro‐active molecular assemblies.     

Effects of processing and cooking on the levels of pesticide residues in wheat samples

The effects of processing and cooking on the levels of pesticide residues in wheat samples were investigated for 13 pesticides in pre-harvest (Pre, 9 pesticides) and post-harvest (Post, 6 pesticides) samples. In the milling process, the transfer ratios (%, total pesticide residue amount in product/that in wheat grain) of wheat bran were greater than 70% and 80% for pre-harvest and post-harvest samples, respectively. The transfer ratios of flour ranged from 1.7% to 23% (Pre) and 4.0% to 11% (Post). There was no significant difference in transfer ratio among the pesticides investigated. The processing factors (Pf, the concentration (mg/kg) of pesticide in product/that in the wheat grain) of flour ranged from 0.030 to 0.40 (Pre) and 0.069 to 0.18 (Post). The values in pre-harvest samples were higher than those in post-harvest samples. Investigation of changes of pesticide residues during processing and/or cooking is useful not only to establish MRLs, but also to recognize actual levels of pesticide residues in food.     

Effects of processing and cooking on the levels of pesticide residues in rice samples

The effects of processing and cooking on the levels of pesticide residues in rice samples were investigated for 11 pesticides in pre-harvest (9 pesticides) and post-harvest (4 pesticides) samples. In the polishing process, the transfer ratio (%, total pesticide residue amount in product/that in brown rice) of rice bran ranged from 40% to 106%, and the transfer ratio of polished rice ranged from 9% to 65% in pre-harvest samples. These values varied from pesticide to pesticide. The processing factor (the concentration (mg/kg) of pesticide in product/that in the brown rice) of polished rice ranged from 0.11 to 0.73. The loss of pesticides during processing and/or cooking did not correlate to any single physical or chemical property. Investigation of changes of pesticide residues during processing and/or cooking is useful not only to establish MRLs, but also to recognize actual levels of pesticide residues in food.     

Suppressive effect of poly-gamma-glutamate on SOS response of Salmonella typhimurium induced by chemical mutagens

We studied the suppressive effect of poly-gamma-glutamate (PGA) on the SOS response of Salmonella typhimurium induced by several direct [furylframide, AF-2; N-methyl-N'-nitro-N-nitrosoguanidine, MNNG; and 4-nitroquinoline 1-oxide, 4NQO] and indirect [3-amino-1-methyl-5H-pyrido-(4,3-b) indole, Trp-P-2; 2-amino-3-methylimidazo (4,5-f) quinoline, IQ; and 2-amino-3,8-dimethylimidazo (4,5-f) quinoxaline, MeIQx] mutagens. PGA preparations with average molecular masses of 50, 2000, 4000, 6000, and 8000 kDa from Bacillus subtilis (chungkookjang) were used. When we used PGA Na salt with a molecular mass of 4000 kDa, the suppression rate increased with increasing PGA concentration; 3% PGA showed 80-90% suppression irrespective of the type of chemical mutagen. PGA preparations with molecular masses of 50 kDa and more than 6000 kDa were less effective. Glutamate and acidic polymers such as carboxymethylcellulose and xanthan gum showed lower suppressive effects than PGA. PGA proved to have high antimutagenic activity.     

High-efficiency secretory production of peroxidase C1a using vesicular transport engineering in transgenic tobacco

Horseradish peroxidase isozyme C1a (HRP C1a) is widely used as a reporter enzyme in a variety of detection procedures such as enzyme-linked immunosorbent assay (ELISA) and western blotting. We previously isolated the gene encoding HRP C1a and showed that HRP C1a is at first translated as a preproprotein containing propeptides at its N- and C-termini (N-terminal secretion signal peptide and C-terminal propeptide; CTPP). The signal peptide (sp) is necessary for endoplasmic reticulum (ER) translocation and the CTPP acts as a vacuolar sorting determinant. Furthermore, HRP C1a was secreted into the culture medium from cells expressing the HRP C1a gene without the CTPP region. We optimized the secretory production system of HRP C1a in tobacco plants. To determine a suitable signal peptide for high-efficient secretion of proteins, three types of sp derived from HRP C1a (C1Psp), beta-D-glucan exohydrolase (GEsp) and 38 kDa peroxidase (38Psp) were compared. GE and 38P are secretory proteins highly accumulated in the culture medium of BY2 cells. The secretion efficiency was increased by 34% and 53% when GEsp and 38Psp was used, respectively. Next, we used a translational enhancer, the 5'-untranslated region of Nicotiana tabacum alcohol dehydrogenase gene (NtADH 5'-UTR). The production of HRP C1a was increased by placing NtADH 5'UTR in front of the ORF in BY2 cells. These results indicate that the localization and expression level of recombinant proteins can be controlled by the use of propeptides and 5'UTR, respectively. Finally, high-efficiency secretory production of the HRP C1a was also achieved in transgenic tobacco.     

Reaction of thiol to diene polymer in the presence of various catalysts

The addition reaction of benzylmercaptan to diene polymer (natural rubber, and cis-1,4-polyisoprene) by various optically active catalysts such as d-camphorsulphonic acid, d-percamphoric acid, and active-amylalcoholate (sodium and barium) were carried out in benzene or anisole at room temperature to 100°C. The optically active adduct polymer was only obtained from the reaction of benzylmercaptan to natural rubber and cis-1,4-polyisoprene by active-amylalcoholate (barium), but was not obtained by the other catalysts. The [α]²⁵ value of optically active adduct polymer was ?0·1°C～?0·6°C (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation. The reaction of benzylmercaptan to cis-1,4-polybutadiene, various styrene-butadiene copolymers, and alternating butadiene-acrylonitrile copolymer were carried out, but the optically active adduct polymers were not obtained by these catalysts.