Flexible Graphite/PPG Hybrid Composite-Based Resistive Sensor for Sensing Organic Compounds.

Our objective in this study was to investigate a sensor for volatile organic compounds based on a graphite (G)/polypropylene glycol (PPG) hybrid composite (HC) for sensing hybrid elements. The G/PPG HC sensor films for organic-matter detection were successfully fabricated on polyethylene terephthalate (PET) film with a simple blade-coating method. The sensing paste based on G/PPG (1:2) HC showed good dispersibility and stability. In addition, G/PPG HC sensor films with organic compounds showed different thickness changes as a function of the G/PPG ratio because of the swelling effect of the polymer. The observed differences in resistance of the G/PPG HC films corresponded to those of common organic compounds, suggesting that the disconnection of graphite caused by the swollen PPG matrix caused explosive resistance change. Moreover, we evaluated the sensitivity of typical hydrocarbon materials, such as benzene and toluene, in the sensor film as well as petroleum materials without moisture-induced malfunctions. This study could provoke knowledge about superior sensing with cost-effective and easily scalable materials using polymer/graphite composite-based sensors to improve the sensitivity, selectivity, and stability of chemical sensor applications.

Innovatively Continuous Mass Production Couette-taylor Flow: Pure Inorganic Green-Emitting Cs4PbBr6 Perovskite Microcrystal for display technology.

We report for the first time the mass production of Cs4PbBr6 perovskite microcrystal with a Couette-Taylor flow reactor in order to enhance the efficiency of the synthesis reaction. We obtained a pure Cs4PbBr6 perovskite solid within 3 hrs that then realized a high photoluminescence quantum yield (PLQY) of 46%. Furthermore, the Cs4PbBr6 perovskite microcrystal is applied with red emitting K2SiF6 phosphor on a blue-emitting InGaN chip, achieving a high-performance luminescence characteristics of 9.79 lm/W, external quantum efficiency (EQE) of 2.9%, and correlated color temperature (CCT) of 2976 K; therefore, this perovskite is expected to be a promising candidate material for applications in optoelectronic devices.

High-efficiency exfoliation of large-area mono-layer graphene oxide with controlled dimension.

In this work, we introduce a novel and facile method of exfoliating large-area, single-layer graphene oxide using a shearing stress. The shearing stress reactor consists of two concentric cylinders, where the inner cylinder rotates at controlled speed while the outer cylinder is kept stationary. We found that the formation of Taylor vortex flow with shearing stress can effectively exfoliate the graphite oxide, resulting in large-area single- or few-layer graphene oxide (GO) platelets with high yields (>90%) within 60 min of reaction time. Moreover, the lateral size of exfoliated GO sheets was readily tunable by simply controlling the rotational speed of the reactor and reaction time. Our approach for high-efficiency exfoliation of GO with controlled dimension may find its utility in numerous industrial applications including energy storage, conducting composite, electronic device, and supporting frameworks of catalyst.

Efficient removal of arsenic by strategically designed and layer-by-layer assembled PS@+rGO@GO@Fe3O4 composites.

The PS@+rGO@GO@Fe3O4 (PG-Fe3O4) hybrid composites for Arsenic removal were successfully fabricated and well dispersed using layer-by-layer assembly and a hydrothermal method. The PG-Fe3O4 hybrid composites were composed of uniformly coated Fe3O4 nanoparticles on graphene oxide layers with water flow space between 3D structures providing many contact area and adsorption sites for Arsenic adsorption. The PG-Fe3O4 hybrid composite has large surface adsorption sites and exhibits high adsorption capacities of 104 mg/g for As (III) and 68 mg/g for As (V) at 25 °C and pH 7 comparison with pure Fe3O4 and P-Fe3O4 samples.

Ge nanopillar solar cells epitaxially grown by metalorganic chemical vapor deposition.

Radial junction solar cells with vertically aligned wire arrays have been widely studied to improve the power conversion efficiency. In this work, we report the first Ge nanopillar solar cell. Nanopillar arrays are selectively patterned on p-type Ge (100) substrates using nanosphere lithography and deep reactive ion etching processes. Nanoscale radial and planar junctions are realized by an n-type Ge emitter layer which is epitaxially grown by MOCVD using isobutylgermane. In situ epitaxial surface passivation is employed using an InGaP layer to avoid high surface recombination rates and Fermi level pinning. High quality n-ohmic contact is realized by protecting the top contact area during the nanopillar patterning. The short circuit current density and the power conversion efficiency of the Ge nanopillar solar cell are demonstrated to be improved up to 18 and 30%, respectively, compared to those of the Ge solar cell with a planar surface.

Influence of Growth Temperature on the Characteristics of Single-Junction p­i­n InGaP Solar Cells.

Single-junction p­i­n InGaP solar cells are grown at various temperatures from 620 to 700 °C by low pressure metalorganic chemical vapor deposition on GaAs (001) substrates. The short circuit current density of the p­i­n InGaP solar cells increases by up to 38.8% when the growth temperature is reduced from 700 to 620 °C, while the open circuit voltage and fill factor show relatively small changes. The external quantum efficiency, especially, in the wavelength regime below 500 nm, is improved for the p­i­n InGaP solar cells grown at lower temperatures. The improvement might be attributed to the reduced absorption loss of the photons in the n-InGaP emitter region. The highest conversion efficiency of 11.01% is attributed from the p­i­n InGaP solar cell grown at 640 °C. Electron mobility and concentration of undoped InGaP layers are investigated as a function of the growth temperature and correlated with the p­i­n InGaP solar cell performance.

Toward Green Synthesis of Graphene Oxide Using Recycled Sulfuric Acid via Couette-Taylor Flow.

Developing eco-friendly and cost-effective processes for the synthesis of graphene oxide (GO) is essential for its widespread industrial applications. In this work, we propose a green synthesis technique for GO production using recycled sulfuric acid and filter-processed oxidized natural graphite obtained from a Couette-Taylor flow reactor. The viscosity of reactant mixtures processed from Couette-Taylor flow was considerably lower (∼200 cP at 25 °C) than that of those from Hummers' method, which enabled the simple filtration process. The filtered sulfuric acid can be recycled and reused for the repetitive GO synthesis with negligible differences in the as-synthesized GO qualities. This removal of sulfuric acid has great potential in lowering the overall GO production cost as the amount of water required during the fabrication process, which takes a great portion of the total production cost, can be dramatically reduced after such acid filtration. The proposed eco-friendly GO fabrication process is expected to promote the commercial application of graphene materials into industry shortly.

Two-Step Growth of Epitaxial InP Layers by Metal Organic Chemical Vapor Deposition.

In this study, we report experimental results on the epitaxial growth of InP layer on GaAs (001) substrate by using MOCVD. We have systematically controlled nucleation steps in order to obtain InP epitaxial layers with high crystallinity quality. The controlling parameters were flow ratio of V/IIIsources and thicknesses of nucleation layer for nucleation steps. We successfully improved the surface roughness and crystallinity of IIP epitaxial layers on GaAs substrates.

Comparative evaluation of magnetite-graphene oxide and magnetite-reduced graphene oxide composite for As(III) and As(V) removal.

Arsenic removal using Fe3O4-graphene oxide composite (M-GO) and Fe3O4-reduced graphene oxide composite (M-rGO) was investigated. The M-GO was more effective to adsorb both As(III) and As(V) than M-rGO, because the more functional groups existing on the M-GO could lead to synthesize more Fe3O4 with M-GO. As(III) was more favorable to be adsorbed than As(V) onto both M-GO and M-rGO. According to the effect of pH on arsenic removal, the electrostatic interaction between the positively charged surface of Fe3O4-graphene based adsorbents and anionic As(V) species was a major factor to adsorb As(V). The adsorption mechanism of As(III), on the other hand, was strongly affected by a surface complexation, rather than electrostatic interactions. Consequently, in terms of the process energy consumption, energy saving could be achieved via omitting the reduction process to fabricate M-rGO from M-GO and the pre-oxidation process to convert As(III) to As(V).

A Gallium Oxide-Graphene Oxide Hybrid Composite for Enhanced Photocatalytic Reaction.

Hybrid composites (HCs) made up of gallium oxide (GaO) and graphene oxide (GO) were investigated with the intent of enhancing a photocatalytic reaction under ultraviolet (UV) radiation. The material properties of both GaO and GO were preserved, even after the formation of the HCs. The incorporation of the GO into the GaO significantly enhanced the photocatalytic reaction, as indicated by the amount of methylene blue (MB) degradation. The improvements in the reaction were discussed in terms of increased surface area and the retarded recombination of generated charged carriers.

Selective photochemical synthesis of Ag nanoparticles on position-controlled ZnO nanorods for the enhancement of yellow-green light emission.

A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to preferentially form Ag NPs on ZnO nanorods. The ratio of visible emission to ultraviolet (UV) emission for the Ag NP-decorated ZnO nanorod arrays, synthesized for 30 min, is 20.5 times that for the ZnO nanorod arrays without Ag NPs. The enhancement of the visible emission is believed to associate with the surface plasmon (SP) effect of Ag NPs. The Ag NP-decorated ZnO nanorod arrays show significant SP-induced enhancement of yellow-green light emission, which could be useful in optoelectronic applications. The technique developed here requires low processing temperatures (120 °C and lower) and no high-vacuum deposition tools, suitable for applications such as flexible electronics.

Anatomical confirmation of computed tomography-based diagnosis of the atherosclerosis discovered in 17th century Korean mummy.

In the present study on a newly discovered 17th century Korean mummy, computed tomography (CT) revealed multiple aortic calcifications within the aortic wall that were indicative of ancient atherosclerosis. The CT-based findings were confirmed by our subsequent post-factum dissection, which exhibited possible signs of the disease including ulcerated plaques, ruptured hemorrhages, and intimal thickening where the necrotic core was covered by the fibrous cap. These findings are strong indicators that the mummy suffered from aortic atherosclerosis during her lifetime. The present study is a good example of how CT images of vascular calcifications can be a useful diagnostic tool in forming at least preliminary diagnoses of ancient atherosclerosis.

Electrochemically synthesized broadband antireflective and hydrophobic GaOOH nanopillars for III-V InGaP/GaAs/Ge triple-junction solar cell applications.

We report the efficiency enhancement of III-V InGaP/GaAs/ Ge triple-junction (TJ) solar cells using a novel structure, i.e., vertically-oriented gallium oxide hydroxide (GaOOH) nanopillars (NPs), as an antireflection coating. The optical reflectance properties of rhombus-shaped GaOOH NPs, which were synthesized by a simple, low-cost, and large-scalable electrochemical deposition method, were investigated, together with a theoretical analysis using the rigorous coupled-wave analysis method. For the GaOOH NPs, the solar weighted reflectance of ~8.5% was obtained over a wide wavelength range of 300-1800 nm and their surfaces exhibited a high water contact angle of ~130° (i.e., hydrophobicity). To simply demonstrate the feasibility of device applications, the GaOOH NPs were incorporated into a test-grown InGaP/GaAs/Ge TJ solar cell structure. For the InGaP/GaAs/Ge TJ solar cell with broadband antireflective GaOOH NPs, the conversion efficiency (η) of ~16.47% was obtained, indicating an increased efficiency by 3.47% compared to the bare solar cell (i.e., η~13%).

Electrochemically synthesized broadband antireflective and hydrophobic GaOOH nanopillars for III-V InGaP/GaAs/Ge triple-junction solar cell applications.

We report the efficiency enhancement of III-V InGaP/GaAs/ Ge triple-junction (TJ) solar cells using a novel structure, i.e., vertically-oriented gallium oxide hydroxide (GaOOH) nanopillars (NPs), as an antireflection coating. The optical reflectance properties of rhombus-shaped GaOOH NPs, which were synthesized by a simple, low-cost, and large-scalable electrochemical deposition method, were investigated, together with a theoretical analysis using the rigorous coupled-wave analysis method. For the GaOOH NPs, the solar weighted reflectance of ~8.5% was obtained over a wide wavelength range of 300-1800 nm and their surfaces exhibited a high water contact angle of ~130° (i.e., hydrophobicity). To simply demonstrate the feasibility of device applications, the GaOOH NPs were incorporated into a test-grown InGaP/GaAs/Ge TJ solar cell structure. For the InGaP/GaAs/Ge TJ solar cell with broadband antireflective GaOOH NPs, the conversion efficiency (η) of ~16.47% was obtained, indicating an increased efficiency by 3.47% compared to the bare solar cell (i.e., η~13%).

Single-material zinc sulfide bi-layer antireflection coatings for GaAs solar cells.

We demonstrated the efficiency improvement of GaAs single-junction (SJ) solar cells with the single-material zinc sulfide (ZnS) bi-layer based on the porous/dense film structure, which was fabricated by the glancing angle deposition (GLAD) method, as an antireflection (AR) coating layer. The porous ZnS film with a low refractive index was formed at a high incident vapor flux angle of 80° in the GLAD. Each optimum thickness of ZnS bi-layer was determined by achieving the lowest solar weighted reflectance (SWR) using a rigorous coupled-wave analysis method in the wavelength region of 350-900 nm, extracting the thicknesses of 20 and 50 nm for dense and porous films, respectively. The ZnS bi-layer with a low SWR of ~5.8% considerably increased the short circuit current density (J(sc)) of the GaAs SJ solar cell to 25.57 mA/cm(2), which leads to a larger conversion efficiency (η) of 20.61% compared to the conventional one without AR layer (i.e., SWR~31%, J(sc) = 18.81 mA/cm(2), and η = 14.82%). Furthermore, after the encapsulation, its J(sc) and η values were slightly increased to 25.67 mA/cm(2) and 20.71%, respectively. For the fabricated solar cells, angle-dependent reflectance properties and external quantum efficiency were also studied.

Fabrication of a pure TiO2 thin film using a self-polymeric titania nano-sol and its properties.

A pure TiO2 thin film without adding any organic binder was fabricated by using a self-polymeric titania nano-sol (14 mass%), which was prepared by the acid peptization method. The particle size distribution in the 14 mass% TiO2 sol, in which almost of particles had a size below 10.2 nm and the crystal phase confirmed by X-ray diffraction analysis was anatase. The diluted nano-sol had a capability to form a thin film at a low temperature (100-400 degrees C) on the slide glass by dipping method. The average thickness of a coating film was measured to be about 0.25-0.30 microm. A coated film had a high refractive index over 1.88 at least irrespective of the heat-treatment even at room temperature drying and showed a super-hydrophilicity (< 5 degrees) after 20 minutes under Ultra Violet light irradiation, and it sustained in the darkness during a long period over 7 days depending on the heat-treatment conditions. Atomic Force Microscopic observation shows that the morphology of a heat-treated film had a relationship with the long-term hydrophilicity in the darkness.

Pattern of lymph node metastasis correlates with tumor location in bladder cancer.

PURPOSE: Resection of a large number of lymph nodes (LNs) increases survival in patients with LN-positive disease; however, morbidity also increases. Here, we investigated the correlation between tumor location and LN metastasis in bladder cancer. MATERIALS AND METHODS: Thirty-six patients with pathological N1 or higher bladder cancer, who underwent radical cystectomy with extended lymphadenectomy, were reviewed retrospectively. The tumor location was classified as right, left, front, posterior, or whole bladder. The LN metastasis pattern was classified as right, left, or bilateral. The correlation between tumor location and LN metastasis was determined by chi-square test. Survival rates were compared by Kaplan-Meier analysis. RESULTS: The numbers of patients with a tumor on the right (group 1), left (group 2), posterior (group 3), or whole (group 4) bladder were 16 (44.4%), 16 (44.4%), 2 (5.6%), and 2 (5.6%), respectively. In group 1, 14 patients (87.5%) had right-sided ipsilateral LNs, and 2 patients (12.5%) had left-sided contralateral LNs. In group 2, 4 patients (25%) had right-sided contralateral LNs, and 12 patients (75%) had left-sided ipsilateral LNs. In group 3, both patients (100%) had right-sided posterior LNs. In group 4, both patients (100%) had positive LNs on both sides. Tumor location and LN metastasis were significantly correlated (p<0.05). Moreover, the survival rate was significantly higher in patients with no LN metastasis than in patients with ipsilateral or contralateral LN-positive bladder cancer. CONCLUSIONS: The location of the bladder tumor and direction of metastatic spread were significantly correlated. Mandatory bilateral lymphadenectomy during radical cystectomy should be questioned.

Large-scale graphene micropatterns via self-assembly-mediated process for flexible device application.

We report on a method for the large-scale production of graphene micropatterns by a self-assembly mediated process. The evaporation-induced self-assembly technique was engineered to produce highly ordered graphene patterns on flexible substrates in a simplified and scalable manner. The crossed stripe graphene patterns have been produced over a large area with regions consisting of single- and two-layer graphene. Based on these graphene patterns, flexible graphene-based field effect transistors have been fabricated with an ion-gel gate dielectric, which operates at low voltages of < 2 V with a hole and electron mobility of 214 and 106 cm(2)/V·s, respectively. The self-assembly approach described here may pave the way for the nonlithographic production of graphene patterns, which is scalable to large areas and compatible with roll-to-roll system.

J-tip guide wire entrapment within the heart during central venous catheterization.

A 55-year-old female was hospitalized for melena. The patient was suspected of having uremia symptoms. Use of a tunneled cuffed hemodialysis catheter of the right internal jugular vein was planned. At one point, the wire could not be extracted or advanced. In addition, whenever the guide wire was manipulated, ventricular premature rhythms developed. Fluoroscopy revealed knotting of the guide wire in the right ventricle. A 7 French guiding catheter was inserted along the guide wire, which loosened the knotting of the guide wire. The present case shows that entrapment within the heart can develop due to use of a J-tip guide wire. If a guide wire cannot be removed despite several attempts with gentle pressure, this event should be ruled out by fluoroscopy and chest X-ray. Using of straight or curved guide wire and real-time surveillance using fluoroscopy or electrocardiography may be important to prevent this complication.

Impact of a retrotrigonal layer backup stitch on post-prostatectomy incontinence.

PURPOSE: To evaluate the impact of a retrotrigonal layer backup stitch (RTBS) during robot-assisted laparoscopic radical prostatectomy (RALP) on post-prostatectomy incontinence. MATERIALS AND METHODS: We compared the difference in continence recovery between 94 patients (group 1, as historical controls) and 57 patients (group 2). The only technical difference between our two groups was the incorporation of the retrotrigonal layer into the posterior aspect of the vesicourethral anastomosis (group 1: without RTBS; group 2: with RTBS). Postoperative continence recovery was defined as the use of no absorbent pads. RESULTS: In group 1, the continence rate at 3, 6, and 12 months postoperatively was 40.4%, 70.2%, and 90.4%, respectively;in group 2, the continence rate was 42.1%, 70.1%, and 89.7%, respectively. The median (95% confidence interval) time to continence recovery was four months (range, 1 to 12 months) in group 1 and four months (range, 1 to 9 months) in group 2. Kaplan-Meier curves showed no significant difference in the recovery of continence between the two groups (log rank test, p=0.629). CONCLUSIONS: A RTBS does not appear to improve urinary incontinence after RALP. Further anatomical study and prospective randomized studies will be needed to confirm this.