Effect of Gd3+ Doping on Sol-Gel Prepared Y2O3 Films as Gate Insulators for Oxide Thin Film Transistors.

The relationships between the microstructure and the dielectric properties of sol-gel prepared Y2O3 films with various Gd3+ doping were systematically investigated. Robust solution processed lanthanide films, (Y1-xGdx)2O3 (0 < x ≤ 0.5), are demonstrated as high-k gate insulators for low voltage-driven oxide thin film transistors and their optimized composition is presented. With the proper amount of Gd3+ doping, the corresponding thin film insulators exhibit low leakage current with increased dielectric constant. The resultant Zn-Sn-O/(Y, Gd)2O3 TFT exhibits enhanced performance, by a factor of 10.7 compared with TFTs using a SiO2 insulator, with a field-effect mobility of ~3.15 cm²V-1s-1 and an exceptionally low operating voltage <15 V.

Synthesis and Photophysical Properties of a Hyperbranched Trimethylsilyl Substituted Poly(phenylene vinylene) Derivative.

A novel trimethylsilyl substituted hyperbranched conjugated poly(phenylene vinylene) (Hyper-PBTMS-PPV) was synthesized through the Wittig polycondensation polymerization. Hyper-PBTMSPPV has good solubility in common organic solvents and showed good thermal stability up to 402 °C with less than 5 wt% weight loss. The photophysical properties of Hyper-PBTMS-PPV film are investigated and compared with trimethylsilyl-containing linear poly(1,4-phenylene vinylene) (Linear-PBTMS-PPV). An absorption maximum of Hyper-PBTMS-PPV film was determined at 335 nm which was far blue-shifted than that of Linear-PBTMS-PPV (380 nm). Hyper-PBTMS-PPV film showed blue photoluminescence (PL) peak at 449 nm. In addition, Hyper-PBTMS-PPV film exhibited almost no long wavelength emission peaks even the film was annealed at 120 °C for 30 min in air condition. High PL efficiency (Φfilm = 0.80) and no aggregate or excimer emission of Hyper-PBTMS-PPV film are due to the inhibition of intramolecular or intermolecular interaction by the introduction of the hyperbranched network into the trimethylsilyl-containing poly(phenylene vinylene) backbone.

Anti-obesity effect of Yangkyuksanwha-tang in high-fat diet-induced obese mice.

BACKGROUND: Yangkyuksanwha-tang (YST) is an herbal medicine based on Sasang constitutional medicine (SCM) and is widely used in Korean traditional medicine. The aim of the study was to evaluate the effect of YST on obesity in high-fat diet (HFD)-induced obese mice. METHODS: We induced obesity in C57bl/6 J mice using a HFD, and then orally administered 300 mg/kg YST for 6 weeks. We measured body weight, food efficiency, organ and fat weight, serum biochemical parameters, and obesity-related gene expression, and carried out histological analysis at the end of the experimental period. RESULTS: YST significantly reduced the absolute body weight and food efficiency ratio. The serum, aminotransferase, glucose, total cholesterol, triglyceride, and low-density lipoprotein-cholesterol levels were significantly lower in the YST-treated group than in the control group, whereas the high-density lipoprotein-cholesterol level in the YST-treated group was significantly higher. The YST-treated group also showed a significant reduction in regional fatty tissues and the absolute weight of various organs. We also observed a significantly reduced expression of AP2/FABP4, C/EBP-ß, leptin, and SREBP1c/ADD1 mRNA, and significantly increased expression of UCP-2 and adiponectin mRNA in adipose tissue in the YST-treated group. YST also decreased the lipid droplet size and lipid accumulation in the liver, as well as adipocyte size in epididymal adipose tissue. At the dose tested, YST was non-toxic to the liver and kidneys of the mice. CONCLUSION: The results imply that YST has anti-obesity effects in obesity-induced mice. Although the number of experimental animals was limited and the drug effects concern mice, rather than humans, which have different constitutions, the study has valuable implications with respect to the general effects of YST.

Synthesis and Blue Light Emitting Properties of Meta- and Para-Linked Hyperbranched Polymers Containing Oxadiazole Unit.

Two meta-and para-linked hyperbranched polymers containing oxadiazole unit (end-capped by carbazole unit) (E-Hyper-MOXPPV and E-Hyper POXPPV) were synthesized through the Wittig poly-condensation polymerization. Both polymers showed excellent solubility in common organic solvents and exhibited good thermal stability up to 350 °C. An absorption maximum of E-Hyper-MOXPPV film was determined at 298 nm which was far blue shifted than that of E-Hyper-POXPPV film (349 nm). Light emitting properties of E-Hyper-MOXPPV and E-Hyper-POXPPV in solution and net solid film are investigated and compared each other. E-Hyper-MOXPPV and E-Hyper-POXPPV films showed blue photoluminescence (PL) peaks at 451 nm and 478 nm, respectively. Both polymers exhibited almost no excimer or aggregate emission even the films were annealed at 80 °C for 1 hr in air condition. No aggregate and excimer emission are due to inhibition of intramolecular or intermolecular interaction by the introduction of hyperbranched network into the meta-and para-linked oxadiazole containing poly(phenylene vinylene) backbone.

Synthesis and Light Emitting Properties of Dithieno[3,2-b:2',3'-d]Thiophene (DTT) Containing Conjugated Polymers for Electroluminescene Devices and Polymer Solar Cells.

Dithieno[3,2-b:2',3'-d]thiophene (DTT) has emerged as an important building block in the synthesis of a wide variety of optoelectronic materials. Two new DTT containing conjugated polymers, poly(dithieno[3,2-b:2',3'-d]thiophenevinylene-alt-9,9-diethylhexyl-2,7-fluorenediyl vinylene) (FLU-DTT) and poly(dithieno[3,2-b:2',3'-d]thiophenevinylene-alt-2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene) (MEH-DTT), were designed and synthesized. The photoluminescence (PL) spectra of FLU-DTT and MEH-DTT in film exhibit maximum emission peaks at 538 and 602 nm, respectively. The MEH-DTT polymer film showed far more red-shifted maximum electroluminescene (EL) emission at 650 nm. The photovoltaic device was also fabricated using MEH-DTT and PC71BM as active layer and it showed power conversion efficiency (PCE) for the polymer solar cell (PSC) as 0.59% under AM 1.5 G (100 mW/cm2) conditions.

Synthesis and Characterization of Benzodithiophene-4,8-Dione-Based Copolymers for Polymer Solar Cells.

A novel series of benzodithiophene-4,8-dione (BDD)-based copolymers, poly[(4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indacenodithiophene-2,7-diyl)-alt-(1,3-bis(2-ethylhexyl)-5,7-di(thiophene2-yl)benzodithiophene-4,8-dione)] (P1) and poly[(5,5,11,11-tetrakis(4-hexylphenyl)dithieno[2,3-d: 2',3'-d']-s-indacenodithiophene-3,9-diyl)-alt-(1,3-bis(2-ethylhexyl)-5,7-di(thiophene-2-yl)benzodithiophene-4,8-dione)] (P2), which have the same acceptor moiety but different donor segments, have been designed and synthesized for use as donor materials in solution-processable polymer solar cells (PSCs). The optical and photovoltaic properties of the copolymers were investigated. The band gaps of the copolymers were in the range 1.91-1.92 eV. Under optimized conditions, the BDD-based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range 2.52-2.92% under AM 1.5 illumination (100 mW/cm2). Among the copolymers, P1, which contained an indacenodithiophene donor unit, showed a power conversion efficiency of 2.92% with a short circuit current of 7.30 mA/cm2, open circuit voltage of 0.92 V, and a fill factor of 0.43, under AM 1.5 illumination (100 mW/cm2).

Inhibitory effects of Taraxacum mongolicum with phreatic water on melanin synthesis.

BACKGROUND: Recently, people have begun showing heightened interest in skin whitening. Melanin is an important factor that determines skin color. The purpose of this study is to investigate the inhibitory effect of Taraxacum mongolicum (TAM) with phreatic water (PW) from Dogo Hot Springs on melanin synthesis. METHODS: We assessed the inhibitory effects of TAM on melanin synthesis in B16F10 mouse melanoma cells. The mRNA levels of tyrosinase related protein (TRP)-1, TRP-2, tyrosinase, MITF, ERK, and PKA protein were analyzed with reverse transcription polymerase chain reaction and Western blot analysis. We also assessed the inhibitory effects of TAM with PW on melanin synthesis in HRM-2 melanin-possessing hairless mice. After UVB irradiation, differences in melanin were analyzed with an image analysis software between the left dorsal skin (untreated part) and the right dorsal skin (treated part). The mRNA levels of TRP-1, TRP-2, and matrix metalloproteinase (MMP)-9 were analyzed with real-time quantitative polymerase chain reaction. The dorsal skins were analyzed with histological test by hematoxylin and eosin staining. RESULTS: TAM inhibited the TRP-1, TRP-2, tyrosinase, MITF mRNA gene expression, and PKA protein expression on the concentration-dependent B16F10 cell. Moreover, TAM increased the ERK mRNA gene expression in the B16F10 cell. After UVB irradiation, TAM with PW increased the differences in melanin between the left dorsal skin (untreated part) and the right dorsal skin (treated part) in HRM-2 mice. TAM with PW inhibited the TRP-1, TRP-2, and MMP-9 mRNA gene expression in HRM-2 mice. TAM with PW decreased the epidermal thickness, around the cell deformation, keratinization, and infiltration in HRM-2 mice. CONCLUSION: These results indicate that TAM with PW has the inhibitory effect of decreasing the melanin synthesis.

Enhanced performance on polymeric light-emitting diode with non-metallic ion in the water soluble non-conjugated polymer.

We have fabricated a polymer light-emitting diode (PLED) from the conventional blue-emitting polymer, polyfluorene (PFO), by constructing a multilayer structure with non-metal ion containing water soluble non-conjugated polymer, polyurethane with F- ion (PU:F-), on the top of the PFO. The device with PU:F- layer shows a maximum luminance of 5294 cd/m2 at an applied voltage of 10 V while the one without PU:F- layer shows only 4439 cd/m2 at the same applied voltage. We propose the improvement of device performance with PU:F- layer was due to not only an effective hole blocking at the polymer-polymer interface but also increase of electric field strength with anode after electro-stactic repulsion between electrons from the cathod and anions from the water soluble polymer layer. We will discuss the effect of multilayer polymer structure in PLED in terms of current/voltage characteristics, luminance, and quantum efficiency related with the applied bias.

Surface modification of a polyimide gate insulator with an yttrium oxide interlayer for aqueous-solution-processed ZnO thin-film transistors.

We report a simple approach to modify the surface of a polyimide gate insulator with an yttrium oxide interlayer for aqueous-solution-processed ZnO thin-film transistors. It is expected that the yttrium oxide interlayer will provide a surface that is more chemically compatible with the ZnO semiconductor than is bare polyimde. The field-effect mobility and the on/off current ratio of the ZnO TFT with the YOx/polyimide gate insulator were 0.456 cm(2)/V·s and 2.12 × 10(6), respectively, whereas the ZnO TFT with the polyimide gate insulator was inactive.

Surface modification of polyimide gate insulators for solution-processed 2,7-didecyl[1]benzothieno[3,2-b][1]benzothiophene (C10-BTBT) thin-film transistors.

The surface property of a polyimide gate insulator was successfully modified with an n-octadecyl side-chain. Alkyl chain-grafted poly(amic acid), the polyimide precursor, was synthesized using the diamine comonomer with an alkyl side-chain. By adding a base catalyst to the poly(amic acid) coating solution, the imidization temperature of the spin-coated film could be reduced to 200 °C. The 350 nm-thick polyimide film had a dielectric constant of 3.3 at 10 kHz and a leakage current density of less than 8.7 × 10(-10) A cm(-2), while biased from 0 to 100 V. To investigate the potential of the alkyl chain-grafted polyimide film as a gate insulator for solution-processed organic thin-film transistors (TFTs), we fabricated C(10)-BTBT TFTs. C(10)-BTBT was deposited on the alkyl chain-grafted polyimide gate insulator by spin-coating, forming a well-ordered crystal structure. The field-effect mobility and the on/off current ratio of the TFT device were measured to be 0.20-0.56 cm(2) V(-1) s(-1) and >10(5), respectively.

Modified polyvinyl alcohol layer with hydrophobic surface for the passivation of pentacene thin-film transistor.

We modified the surface of a polyvinyl alcohol (PVA) layer by self assembly monolayer technique using a fluorine substituted silane compound (1H,1H,2H,2H-perfluorooctyl-trichlorosilane: FTS) to protect a pentacene thin-film transistor (TFT) from O2 and H2O. Surface modified PVA showed very low surface energy with water contact angle of 106.2 degrees. Surface treatment of PVA layer on pentacene TFT device was done in toluene solvent and we did not observe any damage to the PVA layer or pentacene TFT devices during surface modification process. Pentacene TFT with surface modified PVA passivation layer exhibited very stable TFT operation with almost no field effect mobility drop or threshold voltage shift up to 400 hrs. The performance of unpassivated OTFTs exponentially degraded and almost failed in 290 hrs. We propose that modified PVA layer can be used as a good passivation layer for oxygen and water in OTFT.

Molecular weight effects in the third-harmonic generation spectroscopy of thin films of the conjugated polymer MEH-PPV.

Thin spin-cast films of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) were prepared from samples whose weight-average molecular weight (Mw) was varied in the range of 10-1600 kg/mol. We have characterized the films by means of transmission and reflection ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy to derive the linear optical constants, and third-harmonic generation spectroscopy with variable laser wavelengths to get the modulus and phase angles of the complex third-order nonlinear optical susceptibility chi(3). Increasing molecular weight yields films with significantly larger chi(3) values, absorption coefficients, and refractive indices. The chi(3) values of films from the largest and lowest Mw differ by a factor of 4, which is caused by chain orientation effects, local field effects, and changes of the effective conjugation length.

Soluble and easily crystallized anthracene derivatives: precursors of solution-processable semiconducting molecules.

New soluble anthracene derivatives containing thiophene and phenylenevinylene derivatives were synthesized via well-known synthetic routes. TIPS derivatives were added at the 9,10-positions of anthracene for the solubility and crystallinity. Both of the molecules were found to be promising for high charge mobility and stable organic semiconductors. The soluble anthracene core (TIPSAnt) is a potential precursor for the synthesis of novel semiconducting materials.