Electrical properties and memory effect in the field effect transistor based on organic ferroelectric insulator and pentacene

We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator and molecular conductor, and investigated the electrical properties and memory effects on the PEN-FET. We have observed a drastic change in the drain current at around the coercive electric fieldE _c of the organic ferroelectric insulator in not only a FET (PEN-FET) based on a pentacene (PEN) film but also a FET (IPEN-FET) based on an iodine doped PEN film. The magnitude of the change of the drain current for the IPEN-FET is 200 times larger than that for the PEN-FET. It is expected from these results that the PEN-FET (especially the IPEN-FET) is an improvement in such devices, since it operates at a low gate electric field accompanied by the appearance of the spontaneous polarization in the organic ferroelectric insulator. In addition, we have found that the drain current for the PEN-FET does not return to the initial drain current ofE _G =0 V/cm for more than one week, even if the gate electric field is changed to 0 V/cm from 500 V/cm(>E _c ). From these results, it is suggested that the PEN-FET becomes a memory device.     

Fischer-Tropsch synthesis over cobalt catalysts supported on modified SiO2 with mesoporous silica

SiO₂ was modified by hexagonal mesoporous silica to form a mixture with meso-/macroporous sizes and used as support of Co catalysts for Fischer-Tropsch synthesis in a slurry phase. A synergistic effect on the activity of Co catalyst was found. The catalytic properties are related to the state of surface Co and the character of support.     

Chemo-enzymatic synthesis of 2′,3′-dideoxy-3′-fluoro-β-d-guanosine via 2,3-dideoxy-3-fluoro-α-d-ribose 1-phosphate

2,3-Dideoxy-3-fluoro-α-d-ribose 1-phosphate 2 was stereoselectively synthesized and converted to 2′,3′-dideoxy-3-fluoro-β-d-guanosine 1 by enzymatic reaction using purine nucleoside phosphorylase. This chemo-enzymatic strategy was first applied to the synthesis of 1.     

Preparation of enol ethers by carbonyl olefination utilizing an alkoxymethyl chloride-titanocene(II) system

Aldehydes, ketones, esters and lactones are transformed into enol ethers or 1,2-dialkoxy-1-alkenes by treatment with organotitanium species prepared from alkoxymethyl chlorides and a titanocene(II) complex.     

Photophysical and (photo)electrochemical properties of a coumarin dye

A new coumarin dye, cyano-{5,5-dimethyl-3-[2-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)vinyl]cyclohex-2-enylidene}-acetic acid (NKX-2753), was prepared and characterized with respect to photophysical and electrochemical properties. It was employed as a dye sensitizer in dye-sensitized solar cells and showed efficient photon-to-electron conversion properties. The photocurrent action spectrum exhibited a broad feature with a maximum incident photon-to-electron conversion efficiency (IPCE) of 84% at 540 nm, which is comparable to that for the famous red dye RuL2(NCS)2 (known as N3), where L stands for 2,2'-bipyridyl-4,4'-dicarboxylic acid. The sandwich-type solar cell with NKX-2753, under illumination of full sun (AM1.5, 100 mW cm(-2)), produced 16.1 mA cm(-2) of short-circuit photocurrent, 0.60 V of open-circuit photovoltage, and 0.69 of fill factor, corresponding to 6.7% of overall energy conversion efficiency using 0.1 M LiI, 0.05 M I2, 0.1 M guanidinium thiocyanate, and 0.6 M 1,2-dimethyl-3-n-propyl-imidazolium iodide in dry acetonitrile as redox electrolyte. In comparison with its analogue NKX-2586 (Langmuir 2004, 20, 4205), NKX-2753 with an extra side ring on the alkene chain produced much higher IPCE values at the same conditions. The side ring acted as a spacer to efficiently prevent dye aggregation when adsorbed on the TiO2 surface, resulting in significant improvements of short-circuit photocurrent, open-circuit photovoltage, and fill factor compared with NKX-2586 that aggregated on the TiO2 surface.     

Reversed-phase liquid chromatographic retention and membrane activity relationships of local anesthetics

The chromatographic retention and membrane activity relationships of local anesthetics were studied to address the possible mechanisms for structure specificity and inflammation-associated decrease of their effects. Five representative drugs (3 mM for each) were reacted with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine liposomes in 25 mM potassium phosphate buffer (pH 5.9-7.9, containing 100 mM NaCl and 0.1 mM EDTA) for 10 min at 37 degrees C and the membrane fluidity changes were analyzed by measuring fluorescence polarization with 1,6-diphenyl-1,3,5-hexatriene. Their capacity factors were determined on octadecyl-, octyl- and phenyl-bonded silica columns with a mobile phase consisting of 25 mM potassium phosphate buffer (pH 5.9-7.9, containing 100 mM NaCl and 0.1 mM EDTA)-methanol (30:70, v/v) at a flow rate of 1.0 ml/min and at a column temperature of 37 degrees C and diode-array detection. Mepivacaine, prilocaine, lidocaine, ropivacaine and bupivacaine fluidized membranes in increasing order of intensity, which agreed with their clinical potency. The relative degree of membrane fluidization correlated with that of retention on an octadecyl stationary phase more significantly than the other phases. Both membrane-fluidizing effects and capacity factors decreased by lowering the reaction and mobile phase pH, being consistent with the hypothesis that anesthetic potency is reduced in inflammation because of tissue acidity. Reversed-phase liquid chromatography appears to be useful for estimating the structure-specific and pH-dependent membrane-fluidizing effects of local anesthetics.     

On-line purification for the determination of catecholamines by liquid chromatography

An on-line purification method for catecholamines was studied using a flow system equipped with an alumina microcolumn. The procedure involves catecholamine adsorption, column washing and catecholamine elution steps. The system is designed not to decompose catecholamines under alkaline conditions in the adsorption step. Flow-rates and times for different solutions delivered in each step (alkaline buffer for adsorption, water for washing and an acidic solution for elution), column length and sample volume to be loaded were systematically investigated by liquid chromatography. Under optimum conditions, norepinephrine, epinephrine, dopamine and 3,4- dihydroxybenzylamine (internal standard) can be purified with recoveries of ? 90% within 11 min with manual operation. This method was efficiently applied to urine samples and the results indicate the possibility that catecholamines in biological samples are automatically purified.     

Facile cell patterning on an albumin-coated surface

Fabrication of micropatterned surfaces to organize and control cell adhesion and proliferation is an indispensable technique for cell-based technologies. Although several successful strategies for creating cellular micropatterns on substrates have been demonstrated, a complex multistep process and requirements for special and expensive equipment or materials limit their prevalence as a general experimental tool. To circumvent these problems, we describe here a novel facile fabrication method for a micropatterned surface for cell patterning by utilizing the UV-induced conversion of the cell adhesive property of albumin, which is the most abundant protein in blood plasma. An albumin-coated surface was prepared by cross-linking albumin with ethylene glycol diglycidyl ether and subsequent casting of the cross-linked albumin solution on the cell culture dish. While cells did not attach to the albumin surface prepared in this way, UV exposure renders the surface cell-adhesive. Thus, surface micropatterning was achieved simply by exposing the albumin-coated surface to UV light through a mask with the desired pattern. Mouse fibroblast L929 cells were inoculated on the patterned albumin substrates, and cells attached and spread in a highly selective manner according to the UV-irradiated pattern. Although detailed investigation of the molecular-level mechanism concerning the change in cell adhesiveness of the albumin-coated surface is required, the present results would give a novel facile method for the fabrication of cell micropatterned surfaces.