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We aimed to investigate the usefulness of near-infrared indocyanine green (ICG)-enhanced fluorescence guidance for infrapyloric LN dissection in laparoscopic distal gastrectomy. This study enrolled patients with early gastric cancer scheduled for laparoscopic distal gastrectomy. After intraoperative submucosal injection of ICG (0.1 mg/mL), LN dissection was conducted under near-infrared ICG fluorescence guidance. The operation time, bleeding events during infrapyloric LN dissection were analyzed. Cases were retrospectively 1:3 propensity-score matched to patients who underwent laparoscopic distal gastrectomy without ICG injection. The mean time from midline omentectomy to exposure of the right gastroepiploic vein was significantly shorter in the ICG group (n = 20) than in the non-ICG group (n = 60) (13.05 ± 5.77 vs 18.68 ± 7.92 min; p = 0.001), and the incidence of bleeding during infrapyloric LN dissection was lower in the ICG group (20% vs 68.3%, p

In this study, multilayered, organic-based light-emitting transistors (OLETs) were produced and characterized. The neutral cluster beam deposition method was applied to successively deposit organic semiconducting layers of pentacene, 4,5-di(9H-carbazol-9-yl)phthalonitrile (2CzPN) doped onto 1,3-bis(N-carbazolyl)benzene (mCP), and 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) as the hole-transport, emissive, and electron-transport layers, respectively. The effects of drain electrodes (Au or Li/Al) and TPBi on the device performance were examined under ambient conditions. The bilayered pentacene (bottom, 50 nm)/mCP:2CzPN (top, 50 nm) and trilayered pentacene (bottom, 50 nm)/mCP:2CzPN (middle, 50 nm)/TPBi (top, 10 nm) OLETs demonstrated both electrical switching functionality and control of electroluminescence (EL) in air. In particular, the EL intensity (IEL) was significantly enhanced in the asymmetric bilayered devices adopting a low work function Li/Al drain electrode owing to the lower electro...

Background Using indocyanine green (ICG) fluorescence imaging and tissue marking dyes (TMDs), perigastric lymphatic mapping and their pathological correlation were examined to see whether ICG staining covers all metastatic lymph nodes (LNs) in advanced gastric cancer (AGC). Methods Patients with AGC who underwent open distal or total gastrectomy were enrolled. ICG was serially injected intraoperatively into the subserosa along the greater and lesser curvatures. Stomach specimens were examined under a near-infrared camera. ICG-stained LNs were named, excised, and tattooed with different colored TMDs to retrace the exact location after pathological examinations. Results A total of 687 LNs and 69 LN stations were examined from 11 patients. The map of the perigastric lymphatic network showing the topography of ICG-stained and ICG-unstained LNs, including metastatic information, was successfully reconstructed. The average number of ICG-stained and ICG-unstained LNs were 23.6 ± 12.3 (37.8%) and 38.8 ± 17.1 (62.2%), respectively. LN metastases were present in 28 LN stations of 8 patients. Of 8 cases with LN metastases, 40% (11.1–75% per case) of metastatic LNs were stained by ICG. Of 28 metastatic LN stations, 21 (75.0%) were covered by ICG, and actual metastatic LNs were stained in 16 LN stations (57.1%). In 4/8 cases (50%), all metastatic LN stations showed ICG signals. Conclusions ICG fluorescence imaging and TMD are useful tools for visualizing the perigastric lymphatic network and retracing the exact location of ICG-stained LNs in AGC. However, ICG imaging is still not recommended for selective LN dissection in AGC because of the limited staining of perigastric LNs.

We designed and synthesized regio-regular alternating diketopyrrolopyrrole (DPP)-based D1–A–D2–A terpolymers (PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT) using a primary donor (D1) [3,3′-difluoro-2,2′-bithiophene (F2T2)] and a secondary donor (D2) [2,2′-bithiophene (T2), (E)-1,2-di(thiophen-2-yl)ethene (TVT), or dithieno[3,2-b:2′,3′-d]thiophene (DTT)]. A PDPP2DT-F2T2 D–A polymer was synthesized as well to compare optical, electronic, and photovoltaic properties. The absorption peaks of the terpolymers (PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT) were longer (λmax = 801–810 nm) than the peak of the PDPP2DT-F2T2 polymer (λmax = 799 nm), which is associated with the high-lying HOMO levels of the terpolymers (−5.08 to −5.13 eV) compared with the level of the PDPP2DT-F2T2 polymer (−5.38 eV). The photovoltaic properties of these DPP-based polymers were investigated under simulated AM 1.5G sunlight (100 mW cm−2) with a conventional structure (ITO/PEDOT:PSS/polymer:PC71BM/Al). The open-circuit voltages (Voc) of photovoltaic devices containing the terpolymers were slightly lower (0.68–0.70 V) than the Voc of the device containing the PDPP2DT-F2T2 polymer (0.79 V). The short-circuit current (Jsc) of the PDPPF2T2DPP-DTT device was significantly improved (14.14 mA cm−2) compared with that of the PDPP2DT-F2T2 device (8.29 mA cm−2). As a result, the power conversion efficiency (PCE) of the PDPPF2T2DPP-DTT device (6.35%) was increased by 33% compared with that of the simple D–A-type PDPP2DT-F2T2 device (4.78%). The highest Jsc and PCE values (the PDPPF2T2DPP-DTT device) were attributed to an optimal nanoscopically mixed morphology and strong interchain packing with a high face-on orientation in the blend film state. The study demonstrated that our strategy of using multiple donors in a regio-regular alternating fashion could fine-tune the optical, electronic, and morphological properties of D–A-type polymers, enhancing the performance of polymer solar cells.

BACKGROUND Successful graft regeneration is important in living-donor liver transplantation (LDLT) because partial liver grafts are used. Early allograft dysfunction (EAD) is an intermediate outcome that affects the long-term postoperative course in liver transplantation. The aim of the present study was to investigate liver graft regeneration under EAD development in LDLT. MATERIAL AND METHODS The data of 226 patients who underwent LDLT from September 2010 to July 2014 were retrospectively analyzed. The patients were classified into 2 groups: one with and one without EAD. Graft regeneration, functional recovery, and long-term patient survival were compared between the 2 groups. RESULTS The grafts grew more vigorously in the EAD group than in the non-EAD group, as evidenced by the larger absolute (ALV) and relative liver volumes (RLV) of the former on postoperative days (POD) 7 and 21. The median (interquartile range) RLVs of the non-EAD group versus the EAD group were as follows: 55.2 (47.9-65.8) vs. 53.7 (46.6-64.5)% preoperatively, p>0.05; 76.1 (66.9-85.7) vs. 86.7 (73.9-96.8)% on POD 7, p

For advanced high-performance lithium-ion batteries (LIBs), a novel anode material with a high capacity needs to be developed. In particular, molybdenum disulfide (MoS2) with a layered structure consisting of S-Mo-S formed by van der Waals force exhibits a high theoretical capacity (1280 mAh g−1). In this study, MoS2-TiN electrodes were fabricated using a radio frequency (RF) magnetron sputtering deposition method by which MoS2 and TiN sputtering targets could be individually controlled. As the RF power of the TiN target increased (20, 40, 60 W), the ratio of Ti in the electrodes increased and the ratio of Mo in the electrodes decreased. In particular, compared to pure MoS2, the MoS2-TiN with an optimum amount of TiN exhibited a high discharge capacity for 300 cycles and an improved high-rate cycling performance, i.e. an initial discharge capacity of 789.2 mAh g−1 with the maintained capacity of ∼700 mAh g−1 for 300 cycles. This demonstrates that TiN in the MoS2-TiN could reduce the volumetric variation caused by the conversion reaction of MoS2 and assist in the improvement of the electrodes.

Herein is presented a comparative performance analysis of heterojunction organic-based light-emitting field-effect transistors (OLEFETs) with symmetric (Au only) and asymmetric (Au and LiF/Al) electrode contacts. The devices had a top source–drain contact with long-channel geometry and were produced by sequentially depositing p-type pentacene and n-type N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) using a neutral cluster beam deposition apparatus. The spectroscopic, structural and morphological properties of the organic thin films were examined using photoluminescence (PL) spectroscopy, X-ray diffraction (XRD) method, laser scanning confocal and atomic force microscopy (LSCM, AFM). Based upon the growth of high-quality, well-packed crystalline thin films, the devices demonstrated ambipolar field-effect characteristics, stress-free operational stability, and light emission under ambient conditions. Various device parameters were derived from the fits of the observed characteristics. The hole mobilities were nearly equal irrespective of the electrode contacts, whereas the electron mobilities of the transistors with LiF/Al drain electrodes were higher due to the low injection barrier. For the OLEFETs with symmetric electrodes, electroluminescence (EL) occurred only in the vicinity of the hole-injecting electrode, whereas for the OLEFETs with asymmetric electrodes, the emission occurred in the vicinity of both hole- and electron-injecting electrodes. By tuning the carrier injection and transport through high- and low-work function metals, the hole-electron recombination sites could be controlled. The operating conduction and light emission mechanism are discussed with the aid of EL images obtained using a charge-coupled device (CCD) camera.

In this paper, organic light-emitting field effect transistors (OLEFETs) operating at low voltages |Vop| below 10 V were first produced and characterized. n-Dodecylphosphonic acid (PA-C12)-self-assembled monolayer (SAM)-passivated HfOx dielectrics prepared using sol-gel chemistry decreased the device-operating voltages. Crystalline organic active layers of pentacene and N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) acted as p-and n-type materials, respectively. 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran doped onto a tris(8-hydroxyquinoline) aluminum (Alq3:DCM) layer was used as a light-emitting medium to enhance the luminescence efficiency. Based on a tri-layered structure with balanced ambipolar transports and the combined high capacitance-low leakage current of the PA-C12-SAM-treated HfOx dielectrics, the OLEFETs demonstrated good device performance with light emission at |Vop

High carrier mobilities have recently been achieved in polymer field effect transistors (FETs). However, many of these polymer FET devices require the use of chlorinated solvents such as chloroform (CF), chlorobenzene (CB), and o-dichlorobenzene (DCB) during fabrication. The use of these solvents is highly restricted in industry because of health and environmental issues. Here, we report the synthesis of a low band gap (1.43 eV, 870 nm) semiconducting polymer (PDPP2DT-F2T2) having a planar geometry, which can be readily processable with nonchlorinated solvents such as toluene (TOL), o-xylene (XY), and 1,2,4-trimethylbenzene (TMB). We performed structural characterization of PDPP2DT-F2T2 films prepared from different solvents, and the electrical properties of the films were measured in the context of FETs. The devices exhibited an ambipolar behavior with hole dominant transport. Hole mobilities increased with increasing boiling point (bp) of the nonchlorinated solvents: 0.03, 0.05, and 0.10 cm2 V–1 s–1 for...

In this study, on the basis of p -type pentacene and n -type N,N ′ - dioctyl-perylene-3,4,9,10-tetracarboxylic acid diimide (PTCDI-C8) organic field-effect transistors (OFETs) and two-input complementary NAND logic gates in the top-contact device configuration were produced and characterized. The organic active layers were deposited on hydroxyl-free polymethylmethacrylate (PMMA)-modified indium tin oxide (ITO) glass gate substrates by the neutral cluster beam deposition (NCBD) method. The morphological and structural properties of the organic semiconducting active layers on the PMMA substrates were examined using atomic force microscopy, X-ray diffraction and contact-angle goniometry. Based on the growth of high-quality, well-packed crystalline films on the PMMA dielectric-modified ITO gate substrates, the p - and n -type transistors exhibited hole and electron mobilities of 0.247 and 7.23 × 10 −2 cm 2 /Vs, respectively, in the air without encapsulation. The trap density and activation energy were also derived from the transport characteristics for the temperature dependence of the mobilities in the temperature range 20 − 300 K for the first time. Because of the well balanced p - and n -type OFETs in the devices, the complementary metal-oxide semiconductor (CMOS) NAND logic circuits exhibited a high voltage gain and a large noise margin with slight hysteresis.

Heterojunction-based organic light-emitting field-effect transistors (OLEFETs) with a top-contact, long-channel geometry were fabricated and comparatively characterized. The neutral cluster beam deposition (NCBD) method was used to successively deposit two layers of p-type pentacene and n-type tris(8-hydroxyquinoline)aluminum (Alq3). For doped OLEFETs, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) was used as a highly fluorescent dye dopant to enhance the light-emission efficiency and change the emission color. OLEFETs revealed fine device characteristics based on deposition of highly crystalline active layers. The combination of the highly fluorescent DCM doping and asymmetric electrode configuration (Au and Li:Al or LiF/Al) exhibited efficient energy transfer and enhanced electroluminescence (EL) emission. The operating light-emission mechanisms were discussed based on EL photos acquired using a charge-coupled device (CCD) camera.

Based on the p-type pentacene and n-type N,N′ -ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13), low-voltage organic field-effect transistors (OFETs) and inverters using hafnium (Hf)-based dielectrics were produced and characterized. All the pristine and cyclic olefin copolymer (COC)-passivated HfO x gate dielectrics were deposited by the solution-processed sol–gel chemistry, and organic thin films were deposited on the dielectrics by the neutral cluster beam deposition method. In comparison to the pristine HfO x -based OFETs, the COC-passivated transistors showed better device performance: higher hole and electron mobilities, reduced hysteresis, decreased trap densities, and particularly improved operational stability of n-type transistors. The inverters composed of the optimized p- and n-type OFETs with the asymmetric Au and LiF/Al electrodes using COC-passivated HfO x dielectrics exhibited high gains and good noise margins under ambient conditions.

Low-voltage organic field-effect transistors (OFETs) and complementary metal oxide semiconductor (CMOS) inverters based on pentacene and N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) were fabricated on HfTiOx gate dielectrics. Both pristine dielectrics and substrates passivated with self-assembled monolayers (SAMs) of n-dodecylphosphonic acid (PA-C12) were employed. The high capacitance and low leakage current of the HfTiOx-based dielectrics enabled the devices to operate at |V| < 3 V. Passivation with PA-C12 was highly effective in improving the device characteristics. In particular, an electron mobility of 0.72 cm2 V−1 s−1 was measured for the device fabricated with the passivated HfTiOx dielectric, which represents the best performance reported to date for perylene-based OFETs prepared with thin, high-k gate dielectrics. The CMOS inverters exhibited fast switching and high gain characteristics, which were attributed to good coupling between the optimized p- and n-type OFETs.

High-performance pentacene thin-film transistors operating at low voltages were fabricated using hafnium (Hf)-based blend gate dielectrics. Crosslinked HfOx/1,6-bis(trimethoxysilyl)hexane blend (CLHB) dielectric films were prepared by varying the ratio of HfOx and 1,6-bis(trimethoxysilyl)hexane (BTMH), and the resulting films were deposited by solution-processed sol–gel chemistry. p-Type pentacene was deposited on the dielectric films using the neutral cluster beam deposition method. The dielectric properties and morphologies of the films were systematically investigated with respect to the relationship between the compositions of blend dielectrics and device performance. In comparison to the pristine HfOx-based OFETs, as the BTMH molar ratio increased, the leakage current, capacitance, dielectric constant and trap density of the interface states decreased, leading to an increase in the CLHB-based transistor performance such as increased hole-carrier mobility and current on/off ratio and a decrease in subthreshold swing. The OFETs demonstrated similar device performance at high HfCl4 : BTMH molar ratios of 1 : 0.5 and 1 : 0.8. At the molar ratio of 1 : 0.5, the OFETs operating under −4 V had μh,avgeff = 1.6 cm2 V−1 s−1 and Ion/Ioff = 2 × 105 with the corresponding leakage current and capacitance of ∼2 × 10−7 A cm−2 at 2 MV cm−1 and ∼137 nF cm−2. The performance enhancement was found to be closely correlated with the blend dielectrics.

To achieve good interfacial compatibility between the membrane and electrode, structure modification of sulfonated poly(arylene ether sulfone) (SPAES) was successfully done for use as an electrode binder for polymer electrolyte membrane fuel cells. A new activation method for hydrocarbon membrane-electrode assembly (MEA) with a hydrocarbon binder was developed using a voltage cycle instead of applying a constant voltage, which is a standard activation method for MEA with a Nafion binder. To investigate the effect of the binder, two SPAES samples with different molecular weights were used for characterization, and the composition of the binder was also optimized.

Trihalomethanes (THMs) are chemicals regulated by Environmental Protection Agency's first drinking water regulation issued after the passage of the Safe Drinking Water Act. Among THMs, iodotrihalomethanes (I-THMs) are produced by treating water containing iodides ion with chlorine or ozone. I-THMs are more carcinogenic and biotoxic than chlorinated or brominated THMs. The purpose of this study was to analyze of I-THMs in drinking water using the liquid-liquid extraction (LLE) method with various extraction solvents. The calibration curves ranged from 0.01 to 20 ng/mL and the correlation coefficient showed a good linearity of 0.99 or more. The method detection limit ranged from 0.01 to 0.10 ng/mL. The accuracy of the LLE method ranged from 99.43 to 112.40%, and its precision ranged from 1.10 to 10.36%. Good recoveries (71.35-118.60%) were obtained for spiked drinking water samples, demonstrating that the LLE method is suitable for the analysis of drinking water samples. Dichloroiodomethane, bromochloroiodomethane, and dibromoiodomethane were identified in drinking water collected from 70 places of water purification plants in Korea. The samples were classified by disinfection systems, regions, seasons, and water sources. The concentration of I-THMs in pre-/postchlorination facilities owing to excess chlorine usage was higher than in ozonization/postchlorination facilities. Moreover, the concentrations of I-THMs were high in the coastal region, because of the large amount of halide ions from the sea. There was no seasonal difference; however, the concentration of I-THMs in pre-/postchlorination facilities increased in spring and summer. The concentration of I-THMs in water sources was high in samples from the Geum River and the Yeongsan and Sumjin River. The concentration and detection frequency of I-THMs in Han River and Nakdong River were high in the coastal region, because of numerous pre-/postchlorination facilities and the abundance of halide ions from the ocean.

Phthalates are used in industry products, household items, and medical tools as plasticizers. Human exposure to phthalates has raised concern about its toxicity. In the present study, optimization was conducted for the simultaneous analysis of eight kinds of phthalate metabolites using gas chromatography-mass spectrometry (GC-MS): MEP, MiBP, MnBP, MBzP, MiNP, MEHP, MEOHP, and MEHHP. In order to minimize the matrix effect and to do quantitative analysis, isotope dilution and LLE-GC-MS methods were performed. Urine samples were enzymatically hydrolyzed, extracted with a mixture of n-hexane and ethyl ether (8:2; v:v), and subsequently derivatized with trimethylsilylation. All eight kinds of analytes showed clear resolution and high reproducibility in GC-MS results. The method detection limit ranged from 0.05 ng/mL to 0.2 ng/mL. Calibration curves were found to be linear from 0.2 to 100 ng/mL with -(2)>0.992. The relative standard deviation of the intraday precision using water and urine ranged from 2.1% to 16.3%. The analysis was performed with urine samples that were collected from adults residing in the Republic of Korea. The analyzed concentration results were compared according to gender and region. As a result, DEHP metabolites showed the highest detected concentration (75.92 μg/g creatinine, 100%), and MiNP, a metabolite of DiNP, showed the lowest detected concentration (0.42 μg/g creatinine, 22.5%). On average, female urine (200.76 μg/g creatinine) had a higher detected concentration of ∑8 phthalate metabolites than male urine. Samples from rural regions (211.96 μg/g creatinine) had higher levels than samples from urban regions.

Recently, a cobalt complex based electrolyte such as [Co(bpy) 3 ] 2+/3+ was suggested to replace the conventional I 3 − /I − system because of its potential to provide high open circuit potential and power conversion efficiency in dye-sensitized solar cells (DSSCs). Here, a cobalt sulfide thin film was synthesized by electrochemical deposition and used for a counter electrode. A DSSC with the cobalt sulfide counter electrode exhibits J sc = 7.228 mA/cm 2 , which is 13% higher than that with Pt ( J sc = 6.443 mA/cm 2 ), thereby achieving an enhanced power conversion efficiency. Electrochemical impedance spectroscopy measurements indicate that the reduced Warburg diffusion impedance and faster adsorption of [Co(bpy) 3 ] 3+ facilitate the reduction of the cobalt complex.

고분자 전해질 연료전지(Polymer Electrolyte Membrane Fuel Cell, PEMFC) 상용화를 위해 해결해야 할 과제 중의 하나인 가격 저감을 이루기 위한 방법으로 백금 촉매를 대신할 비귀금속 (non-precious metal) 촉매 제조에 관한 연구를 수행하였다. 비귀금속 촉매의 합성은 산소환원반 응(oxygen reduction reaction, ORR)의 활성점으로 알려져 있는 코발트-질소(Co-N) 결합을 형 성하기 위해 질소를 포함하는 폴리아닐린(PANI)과 코발트염(Co precursor), 그리고 카본 블랙 (C)을 일정한 비율대로 혼합한 후 특별한 열처리 과정 없이 단순한 화학적 환원법에 제조되었다. 제조된 Co-PANI-C 복합 촉매의 구조 분석을 위해 X-선 회절분석(X-ray diffraction, XRD)과 열중량분석(thermogravimetric analysis, TGA)을 실시하였고, ORR에 대한 활성을 평가하기 위 해 rotating disk electrode(RDE) 및 rotating ring disk electrode(RRDE) 측정을 수행하였다. 그 결과 Co-PANI-C 복합 촉매는 ORR반응에 대한 개시 전압은 백금 촉매보다 60 mV 밖에 낮지 않은 값을 보였지만, 반응에 의해 발생되는 환원 전류는 여전히 백금 촉매보다 낮은 값을 보였다. 이 밖에도 전극 회전 속도에 따른 ORR 특성 변화, 전압 사이클 회수에 따른 내구성 변화, 연료전지 적용 시 성능 변화에 대해 논의할 것이다.Abstract : In order to overcome the cost issue for commercialization of polymer electrolyte mem-brane fuel cell (PEMFC), this research was conducted for replacing platinum cathode catalyst with non-precious metal catalyst. The non-precious metal catalyst (Co-PANI-C) was synthesized by the simple reduction method with polyaniline (PANI), carbon black, and cobalt precursor without any heat treatment. Characterization of new Co-PANI-C composite catalysts was done by the mea-surement of X-ray diffraction (XRD) and thermogravimetric analysis (TGA) for structure analysis and performed by rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) for elec-trochemical analysis. As a result, Co-PANI-C catalyst showed 60 mV lower on-set potential for oxygen reduction reaction (ORR) than Pt/C catalyst, but the overall reduction current of Co-PANI-C catalysts by ORR was still smaller than that of Pt/C. In addition, the ORR behavior of Co-PANI-C catalysts depending on the rotation speed of electrode and the stability of Co-PANI-C catalyst under potential cycling and the performance of fuel cell conditions are also discussed.Keywords : Non-precious metal catalyst, Polyaniline, Cobalt, Oxygen reduction reaction.

Air-stable, ambipolar heterojunction-based organic light-emitting field-effect transistors (OLEFETs) with a top-contact, multidigitated, long-channel geometry were produced, and the current–voltage–light emission (I–V–L) characteristics were systematically examined. Two active layers of p-type pentacene and n-type N,N′-ditridecylperylene-3,4,9,10-tetra carboxylic diimide (P13) as well as a protecting layer of 2,5-bis(4-biphenyl) thiophene (BP1T) were successively deposited using the neutral cluster beam deposition method. On the basis of the growth of high-quality, well-packed crystalline thin films, the OLEFETs demonstrated good field-effect characteristics, well-balanced ambipolarity, operational stability, and electroluminescence (EL) under ambient conditions. The operating conduction and EL mechanisms responsible for the observed recombination zone are discussed with the aid of light-emission images obtained using a charge-coupled device.

Organic field-effect transistors (OFETs) and complementary inverters were produced on the basis of n -type N , N ′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) using the neutral cluster beam deposition (NCBD) method. Significant improvements in surface morphology and crystallinity were observed after the surface modification of SiO 2 gate dielectric layers with hydroxyl-free polymer insulators such as polymethylmethacrylate (PMMA) and cyclic olefin copolymer (COC), and thermal post-treatment. Electric characteristics and operational stability of PTCDI-C8-based OFETs were also clearly enhanced after the surface modification, and in particular, the thermally post-treated OFETs with COC-modified SiO 2 gate dielectrics exhibited a high room-temperature mobility of 0.68 cm 2 /V s. Two structural types (generic vs . encapsulated) of inverters in top-contact configuration were fabricated by integration of the p -type pentacene and n -type PTCDI-C8 OFETs using COC-modified SiO 2 gate dielectrics. Due to the increased electron mobilities and good coupling between p - and n -type OFETs, hysteresis-free, fast-switching inverters were realized with high gains of ∼20 in the first and third quadrants of voltage transfer characteristics under ambient conditions. The device characteristics of the encapsulated inverters monitored as a function of the time were well maintained with slight degradation.

Poly(amic acid)s were successfully synthesized from 1,4-bis(4-aminophenoxy)benzene (1,4-APB) or 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) with pyromellitic dianhydride (PMDA), 3,3'-4,4'benzopenonetetracarboxylic dianhydride (BPDA) and p-phenylenediamine (p-PDA) and then they were effectively converted into polyimide films by thermal imidization. The chemical structure and thermo-mechanical properties of polyimide films were examined using Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analyzer (TGA), thermo-mechanical analyzer, dynamic mechanical analyzer (DMA) and universal tensile machine (UTM). The moisture absorption, thermal and mechanical properties of polyimide films decreased with increasing the amount of 1,4-APB and HFBAPP. The polyimide films using HFBAPP showed lower properties than that of 1,4-APB at the same ratio, but it displayed better thermal properties and lower moisture absorption at the similar coefficient of thermal expansion (CTE) with a copper. On the basis of our finding, it is concluded that 4component polyimide films could be utilized for base films for flexible copper clad laminates (FCCL) of flexible printed circuit boards.

In the present study, we report a simple and reproducible method to improve the sensing performance of a graphene gas sensor using ozone treatment and demonstrate it with nitrogen dioxide (NO2) gas. The ozone-treated graphene (OTG) sensor demonstrated remarkable enhancement of the sensing performances such as percentage response, detection limit and response time. The percentage response of the OTG sensor was twofold higher than that of a pristine graphene sensor when it was exposed to 200 ppm concentration of NO2 at room temperature. It is noteworthy that significant improvement was achieved in the response time by a factor of 8. Extremely low parts-per-billion (ppb) concentrations were clearly detectable, while the pristine graphene sensor could not detect NO2 molecules below 10 ppm concentration. The detection limit of the OTG sensor was estimated to be 1.3 ppb based on the signal to noise ratio, which is the cutting-edge resolution. The present ozone treatment may provide an effective way to improve the performance of the graphene-based sensor, given its simple process, practical usability and cost effectiveness.

A series of sulfonated poly(arylene ether sulfone) with photocrosslinkable moieties is successfully synthesized by direct copolymerization of 3,3′-disulfonated 4,4′-difluorodiphenyl sulfone (SDFDPS) and 4,4′-difluorodiphenyl sulfone (DFDPS) with 4,4′-biphenol (BP) and 1,3-bis-(4-hydroxyphenyl) propenone (BHPP). The content of crosslinkable moieties in the polymer repeat unit is controlled from 0 to 10 mol% by changing the monomer feed ratio of BHPP to BP. The polymer membranes can be crosslinked by irradiating UV with a wavelength of 365 nm. From FT-IR analysis, it can be identified that UV crosslinking mainly occurs due to the combination reaction of radicals that occurs in conjunction with the breaking of the carbon–carbon double bonds (–CH = CH-) of the chalcone moieties in the backbone. Consequently, a new bond is created to form cyclobutane. The crosslinked membranes show less water uptake, a lower level of methanol permeability, and good thermal and mechanical properties compared to pristine (non-crosslinked) membranes while maintaining a reasonable level of proton conductivity. Finally, the fuel cell performance of the crosslinked membranes is comparable to that of the Nafion 115 membrane, demonstrating that these membranes are promising candidates for use as polymer electrolyte membranes in DMFCs.

Novel sulfonated poly(arylene ether sulfone) copolymers containing intermolecular ionic cross-linkable moieties, 5,5′-bis[2,4-(hydroxyphenyl) benzimidazole] (BHPB), are synthesized by direct polymerization for application in polymer electrolyte membranes in DMFCs. The synthesized copolymers are controlled by various monomer compositions to confirm the effects of ionic cross-linking from sulfone–amine groups and degree of sulfonation on the polymer electrolyte membrane. The mechanical and thermal properties are enhanced in the ionic cross-linked membranes compared to the non-ionic cross-linked membrane. The water uptake and methanol permeability descend with decreasing degree of sulfonation and increasing content of BHPB. Similarly, regarding proton conductivity and ion exchange capacity (IEC), the low sulfonated membrane with high content of BHPB displays low values. This is attributed to the formation of ionic bonding by the sulfonic acid and amine groups. The novel polymer in this study shows very promising performance in direct methanol fuel cells which is comparable to that using Nafion 115.

The surfaces of the polyimide films Kapton-E and Upilex-S are modified by ethylenediamine treatment to improve its adhesion to a subsequently deposited copper layer. The changes in the chemical composition, morphology, and adhesion properties of the modified polyimide surface are characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and the 90o peel test. An ethylenediamine polyimide treatment induces amino group formation from the broken imide group. The peel strength of Kapton-E and Upilex-S with a copper layer increases from 0.3 to 0.65 kgf/cm and 0.25 to 0.46 kgf/cm, respectively. The results show that ethylenediamine treatment is a good modification method to greatly increase the adhesion performance of polyimide films to a copper layer. Open image in new window

The synthesis, electrochemical analysis, and hydrogen-air fuel cell testing results for a new type of Se/Ru catalyst called Se/Ru(aq) were described in Part 1. In this second report, we present methanol tolerance studies and direct methanol fuel cell testing for the same catalyst. A “methanol-tolerant” catalyst does not oxidize methanol, nor becomes depolarized by its presence, which is a desirable property for DMFC cathodes used with methanol-permeable membranes or in mixed-reactant designs. In perchloric acid electrolyte, the Se/Ru(aq) catalyst was found to be highly tolerant to 1.0 M methanol. More importantly, in fuel-cell testing as a DMFC cathode, Se/Ru(aq) was shown to be highly tolerant to methanol crossing through the membrane (from the anode side) up to a feed concentration of 17 M. The results were compared to those obtained using unmodified Ru black and Pt black at the DMFC cathode, in order to gain insight into the catalyst function and to compare the performance to relevant benchmarks. Compared to Pt cathodes, the performance of Se/Ru(aq) is significantly better at high methanol concentrations (e.g., 17 M), suggesting their use either in DMFCs with high methanol feed concentrations or in mixed-reactant fuel cells.

A modified Nafion binder using a different dispersion solvent, dimethylacetamide (DMAc), was applied to an electrode for a unitized regenerative fuel cell (URFC). The properties of the new Nafion binder, such as dissolution rate, proton conductivity, water uptake, and I–V curves, were characterized in the study. The new Nafion binder showed less brittleness, leading to good structural integrity in the electrode and improvement of stability in the URFC performance. SEM images showed that the interfacial adhesion between the membrane and the electrode was improved by using the new Nafion binder. Therefore, the new Nafion binder was suggested as a promising candidate for a binding material in the electrode of the URFC.

We designed and realized ideal organic complementary metal oxide semiconductor (CMOS) inverters through integration of unipolar p- and n-type organic field-effect transistors (OFETs) produced by the neutral cluster beam deposition (NCBD) method. The two high-performance, top-contact OFETs with multidigitated, long channel-width geometry were based upon hole-transporting pentacene and electron-transporting N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) deposited on poly(methyl methacrylate) (PMMA) modified SiO2 substrates. Due to the well-balanced, high hole and electron mobilities of 0.38 and 0.19 cm2/(V s), low trap densities, and good coupling between p- and n-type OFETs, the hysteresis-free organic CMOS inverters demonstrated sharp inversions and high gains of ∼15 in the first and third quadrants of the voltage transfer curves, and long-term operational stability under ambient conditions.

A new, sulfonated poly(arylene ether sulfone) ionomer with partially fluorinated groups (F-SPAES) was synthesized by the direct polymerization of 1,6-bis(4-fluororphenyl)-perfluorohexane (FPPFH) and 6F-bisphenol A (6F-BPA) with 3,3′-disulfonated 4,4′-difluorodiphenyl sulfone (SDFDPS). The effect of fluorination on the membrane properties and membrane-electrode assembly (MEA) performance for DMFC applications were investigated comprehensively and compared with the pristine SPAES sample. Deliberate control of the hydrophobicity as well as the degree of sulfonation in the F-SPAES membranes allows the effective suppression of water uptake and methanol permeability, while barely affecting the proton conductivity and IEC value. Such an improvement in the membrane properties contributes to the superior single cell performance of the F-SPAES compared to pristine SPAES and Nafion®.

Herein is presented systematic analysis of air-stable, ambipolar heterojunction-based organic light-emitting field-effect transistors (OLEFETs). Top-contact OLEFETs with multidigitated, long channel-width geometry were produced by the successive deposition of electron-transporting N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) and hole-transporting tetracene layers, using the neutral cluster beam deposition (NCBD) method. The morphological, structural, and photoluminescence properties of the untreated and thermally post-treated P13/tetracene active layers were examined by atomic force microscopy, X-ray diffraction, and laser scanning confocal microscopy. From the comparative analysis of the NCBD thin films, the neutral cluster beams led to the preparation of smooth, uniform bilayer films consisting of well-packed grain crystallites. The OLEFETs demonstrated good field-effect characteristics, stress-free operational stability, and electroluminescence under ambient conditions. The operating ...

We present our first application of the neutral cluster beam deposition (NCBD) method to fabricate bilayer heterojunction-based organic light-emitting field-effect transistors (OLEFETs) by superimposing two layers of α,ω-dihexylsexithiophene (DH6T) and N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) successively. Based upon well-balanced ambipolarity (hole and electron field-effect mobilities of 2.22 × 10−2 and 2.78 × 10−2 cm2/Vs), the air-stable OLEFETs have demonstrated good field-effect characteristics, stress-free operational stability and electroluminescence under ambient condition.

A novel approach for effectively dispersing SiO2 nanoparticles in a sulfonated poly(arylene ether sulfone) ionomer (SPAES) matrix has been demonstrated. It is based on the application of wet-type milling process. Compared to a conventional mixing process such as sonication, wet-type milling allowed noticeable improvements in SiO2 nanoparticle dispersion, owing to the intensive impact of collisions between milling beads and nanoparticles. In terms of nanoparticle dispersion, the influence of wet-type milling on the direct methanol fuel cells (DMFC) membrane performance such as proton conductivity, methanol permeability, and selectivity was examined and compared with sonication process. This study underlines that nanoparticle dispersion in the composite membranes is crucial in determining DMFC membrane performance and can be substantially improved by employing a novel mixing process, i.e. wet-type milling. Keywords: Nanoparticle dispersion, Wet-type milling, SPAES/SiO2 composite membranes, DMFC membrane performance

Tetracene-based organic thin-film transistors (OTFTs) were prepared using a neutral cluster beam deposition (NCBD) method. The effect of surface modification with an amphiphilic surfactant, octadecyltrichlorosilane (OTS), on the formation of thin films and the geometric influence of channel length and width on the transistor characteristics were systematically examined. The estimated trap density and temperature-dependence of the field-effect mobility in the range of 10–300 K demonstrated that surfactant pretreatment decreased the total trap density and activation energy for hole-transport by reducing structural disorder in the active layer. In particular, the room-temperature hole mobilities of 0.162 and 0.252 cm 2 /Vs for untreated and OTS-pretreated devices were among the best to date for polycrystalline tetracene-based transistors using SiO 2 gate dielectric layers without any thermal post-treatment.

Pentacene-based transistors produced by a novel neutral cluster beam deposition method were characterized, and the effects of the surface pretreatments were examined. Atomic force microscopy and X-ray diffraction showed that the cluster beams were quite efficient in growing high-quality, crystalline thin films on SiO 2 substrates at room-temperature without any thermal post-treatment, and that an amphiphilic surfactant, octadecyltrichlorosilane (OTS), enhances the packing density and crystallinity significantly. The observed field-effect mobilities ( μ eff ) were among the best reported thus far: 0.47 and 1.25 cm 2 /Vs for the OTS-untreated and -pretreated devices, respectively. The device performance was found to be consistent with the estimated trap density and activation energy, which were derived from the transport characteristics for the temperature dependence of μ eff in the range of 10−300 K.

Platinum-modified Au nanoparticles on a carbon support were prepared using carbon-supported Au nanoparticles as a substrate and a successive reduction process. These nanoparticles were applied as an electrocatalyst for formic acid electro-oxidation. The uniform Pt-modified Au nanoparticles (

This work studies formic acid crossover in a direct formic acid fuel cell under different operating conditions. Comparison with methanol crossover in a direct methanol fuel cell is included. The effects of cell conditioning, temperature, fuel concentration, and Nafion® thickness on the rate of formic acid crossover are examined. The effects of temperature, concentration, and membrane thickness are qualitatively similar to those with methanol, but overall crossover rates are much lower. Under the same operating conditions, it is found that formic acid has a crossover flux rate that is approximately one-sixth that of methanol. Measurement of the CO2 membrane permeation flux is performed to determine its contribution to a bias that it might cause in the quantification of crossover.

The geometric effect of graphite nanofibers (GNFs) as a support for PtRu electrocatalysts on the oxidation of methanol for direct methanol fuel cells (DMFCs) was studied using X-ray diffraction, field emission transmission electron microscopy (FETEM) and electrochemical measurements. A high loading of 60 wt% PtRu catalyst, which is readily applicable to DMFCs, was well dispersed on GNFs. Further, the shape of the supported metal particles was affected by interactions with the GNFs. Electrochemical analysis indicated that GNF-supported PtRu catalysts resulted in an increased catalytic activity of about 100% over that of Vulcan XC-72 supported catalysts. FETEM data indicate that the enhanced activities result from a geometric modification of the catalyst particles by specific interactions between the GNFs and the supported PtRu nanoparticles.

The influence of annealing of membrane electrode assembly (MEA) of a direct methanol fuel cell (DMFC) on the cell performance was investigated. The annealing was conducted at various temperatures of 110, 130, 150 and 200 °C. Annealing at 130 °C could produce highest proton conductivity of the recast Nafion binder and electrochemical active surface area of the electrode, leading to the highest cell performance.

We sought to evaluate lysophosphatidic acid (LPA) signaling improvement in lung development by assessing the expression of autotaxin and LPA receptor 1 and 3 (LPAR1 and LPAR3) in the neonatal rat lung during normal perinatal development and in response to hyperoxia. In the developmental study, rats were sacrificed on days 17, 19, and 21 of gestation; on postnatal days 1, 4, and 7; and at adulthood (postnatal 9 weeks). In the hyperoxia study, 42 postnatal 4-day-old rat pups were divided into seven groups and exposed to either 85% O2 for 24, 72, or 120 h or room air for 0, 24, 72, or 120 h. The rats were then euthanized after 0, 24, 72, and 120 h of exposure. Immunofluorescence demonstrated that autotaxin, LPAR1, and LPAR3 proteins were broadly colocalized in airway epithelial cells, but mainly distributed in vascular endothelial and mesenchymal cells during the first postnatal week. The expression of autotaxin, LPAR1, and LPAR3 were increased during late gestation and then decreased after birth. Autotaxin expression and enzymatic activity were significantly increased at 72 and 120 h after exposure to hyperoxia. LPAR1 and LPAR3 expression was also increased after 120 h of hyperoxic exposure. These findings suggest that LPA-associated molecules were upregulated at birth and induced by hyperoxia in the developing rat lung. Therefore, the LPA pathway may be involved in normal lung development, including vascular development, as well as wound-healing processes of injured neonatal lung tissue, which is at risk of neonatal hyperoxic acute lung injury.

The use of a PtAu catalyst as an anode catalyst for the oxidation of formic acid in direct formic acid fuel cells is described. Catalytic activities of PtAu and PtRu anodes were studied using a linear sweep voltammetry technique in a single cell configuration. PtAu showed a lower on-set potential and a larger current density than that of PtRu in formic acid oxidation. In addition, the maximum power densities at 30 °C for PtAu and PtRu were 94 and 74 mW cm−2, respectively. In order to evaluate long-term durability, the single cells were operated for hundreds of hours with a 6 M aqueous formic acid solution at 60 °C under 100 mA cm−2. The difference in performance between PtAu and PtRu after 500 h reached ca. 90 mV in direct formic acid fuel cells.

In order to enhance the compatibility between the electrode and the membrane and also to reduce the methanol cross-over from the anode to the cathode in direct methanol fuel cells, a Nafion membrane coated with a poly(vinylidene fluoride) copolymer/Nafion blend has been prepared and characterized. The coated Nafion results in a reduction in methanol cross-over and an enhancement in cell performance due to its improved compatibility with the electrodes.

Nanocomposites of PtRu nanoparticles and polyaniline (an electronically conducting polymer) were synthesized by the borohydride reduction method in an aqueous solution for the anode electrode in direct methanol fuel cells (DMFCs). Due to the high electronic conductivity of polyaniline, the methanol oxidation current for polyaniline supported PtRu nanocomposites was similar to that of carbon supported PtRu catalysts. In addition, Pd-impregnated nanocomposite Nafion membranes were suggested to enhance DMFC performance by blocking or reducing methanol crossover and their characteristics were affected by the impregnation time of Pd-nanoparticles.

To enhance the compatibility between electrode and membrane and also reduce methanol crossover from anode to cathode in direct methanol fuel cells, a Nafion membrane coated with a PVdF copolymer/Nafion blend has been prepared and characterized. This coated Nafion shows reduced methanol crossover and an enhancement in cell performance due to its improved compatibility with the electrode compared to that of native Nafion.

We have fabricated and characterized heterojunction electroluminescent devices with the structure of ITO-coated glass/tetracene/(DCM-doped)Alq 3 /Li:Al. The organic thin films of tetracene, Alq 3 , and dye dopant DCM were deposited by applying the cluster beam deposition (CBD) methods. X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements show that the flat and smooth thin tetracene films are close to a highly ordered, single crystal. Photoluminescence (PL), electroluminescence (EL) and device characteristics such as current density-voltage ( J − V ), EL intensity-voltage ( L − V ), and external quantum efficiency-current ( EQE-I ) were examined for undoped and DCM-doped devices.

For direct methanol fuel cell, blends of vinylidene fluoride-hexafluoropropylene copolymer (P(VdF-co-HFP)) and Nafion were prepared the different equivalent weight of Nafion. The investigations of the blend morphology were performed by means of permeability test, uptake measurement, differential-scanning calorimetry (DSC), and scanning electron microscopy. In the blend membranes, many pores were created as the content of Nafion in blend increased. Then, the methanol uptake was sharply increased. But the methanol permeability was not sharply increased because the methanol permeation through blend membranes is diffusion-controlled process. The methanol permeability of N10 (low equivalent weight) series was similar to that of N11 series (high equivalent weight). The proton conductivity of N10 series was around one and a half times higher than that of N11 series. The cell performance of the blend was much enhanced when the equivalent weight of Nafion was 1000.

Ordered uniform porous carbon frameworks were synthesized against removable colloidal silica crystalline templates by carbonization of phenol and formaldehyde as a carbon precursor in the presence of sulfuric acid. These highly ordered uniform porous carbons when used as a catalyst support, resulted in much improved catalytic activity for methanol oxidation in fuel cell probably due to their three-dimensionally interconnected uniform pore structures and high surface areas.

For direct methanol fuel cell, the proton conducting membrane based on semi-interpenetrating polymer networks (IPNs) of Nafion and crosslinked poly(AMPS) was prepared and characterized. The modification of Nafion with crosslinked poly(AMPS) such as hydrocarbon polymer changed the state of water in membranes. Without a significant increase of the membrane resistance, the semi-IPNs demonstrated a reduction of the methanol permeability, comparing to the native Nafion. And the maximum power density of AMPS60 increased as much as 22.2% compared with Nafion.

The enhanced catalytic activity of PtRuRhNi was examined in relation to the oxidation of methanol in a direct methanol fuel cell. As evidenced by transmission electron microscopy and X-ray diffraction analysis, the synthesized PtRuRhNi appeared to be a well-synthesized Pt-based alloy nanoparticle. The catalytic activity of PtRuRhNi alloy electrocatalyst was superior to that of PtRu, from the standpoint of its high oxidation current, power density, and better stability in the electrochemical half- and single-cell measurements. Through X-ray absorption near edge structure and X-ray photoelectron spectroscopy, it was found that Pt and Ru in the PtRuRhNi are present in electronic and chemical states that are favorable to methanol electrooxidation. The dominant existence of Pt and Ru metallic states on the catalyst was essential for its high surface activity with respect to methanol electrooxidation. However, the catalytic enhancement of PtRuRhNi due to the chemical states of Rh/Ni was considered and examined.

The gas-phase radical-radical reaction dynamics of O(3P) + C3H5 --H(2S) + C3H4O was studied at an average collision energy of 6.4 kcal/mol in a crossed beam configuration. The ground-state atomic oxygen [O(3P)] and allyl radicals (C3H5) were generated by the photolysis of NO2 and the supersonic flash pyrolysis of allyl iodide, respectively. Nascent hydrogen atom products were probed by the vacuum-ultraviolet-laser induced fluorescence spectroscopy in the Lyman-alpha region centered at 121.6 nm. With the aid of the CBS-QB3 level of ab initio theory, it has been found that the barrierless addition of O(3P) to C3H5 forms the energy-rich addition complexes on the lowest doublet potential energy surface, which are predicted to undergo a subsequent direct decomposition step leading to the reaction products H + C3H4O. The major counterpart C3H4O of the probed hydrogen atom is calculated to be acrolein after taking into account the factors of barrier height, reaction enthalpy, and the number of intermediates involved along the reaction pathway. The nascent H-atom Doppler profile analysis shows that the average center-of-mass translational energy of the H + C3H4O products and the fraction of the total available energy released as the translational energy were determined to be 3.83 kcal/mol and 0.054, respectively. On the basis of comparison with statistical calculations, the reaction proceeds through the formation of short-lived addition complexes rather than statistical, long-lived intermediates, and the polyatomic acrolein product is significantly internally excited at the moment of the decomposition.