275 research outputs found

    Reduced Graphene Oxide-Modified Tin Oxide Thin Films for Energy and Environmental Applications

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    Metal halide perovskite solar cells (PSCs) have attracted tremendous attention because of their rapid development. To enhance the power conversion efficiency (PCE) of PSCs, significant research efforts have focused on the optimization of electron transport layer (ETL). SnO2 has been extensively used as ETL due to its excellent electron transport properties. The optimization of the fabrication of SnO2 and passivation of the structural defects are essential to the improved performance of ETL. This thesis aims to (i) investigate the fabrication of pristine SnO2 thin film and characterize its material properties and (ii) develop a novel fabrication of reduced graphene oxide (RGO) modified SnO2 thin film as ETL and characterize its material properties. The first part was achieved by investigating the effects of UV-ozone treatment on fabrication of SnO2 thin films as well as the effects of precursor concentration and heating temperature on the resultant properties of the SnO2 thin films. The results showed that UV-ozone pretreatment is essential for depositing a continuous SnO2 thin film. A high precursor concentration resulted in low roughness and high n-type defects in SnO2 thin film, which would decrease the electrical conductivity while a high temperature of heat treatment resulted in increased crystallinity and a decrease in oxygen vacancies and residual Cl. The second part was achieved by investigating the effects of (i) preparation time of the RGO-SnO2 precursor and (ii) the concentration of RGO on the properties of RGO-SnO2 thin films. The RGO-SnO2 thin film was successfully fabricated by spin coating a precursor solution of SnCl2 in ethanol (95%) mixed with graphene oxide (GO) followed by heating at low temperatures. By conducting RGO modification, RGO-SnO2 thin films with high crystallinity and low oxygen vacancy contents were achieved resulting in a high electrical conductivity. The study showed that 3 h of preparation time for the precursor and addition amounts of 2.62 wt% RGO would result in the best properties of the RGO-SnO2 thin films. This ETL has a surface roughness Ra of <20 nm, good band alignment with perovskite materials (CBM <3.9 eV), and electrical conductivity of 30 x 10-5 S/m, which can enable its use in high-performance PSCs

    Focussed Review of Utilization of Graphene-Based Materials in Electron Transport Layer in Halide Perovskite Solar Cells: Materials-Based Issues

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    The present work applies a focal point of materials-related issues to review the major case studies of electron transport layers (ETLs) of metal halide perovskite solar cells (PSCs) that contain graphene-based materials (GBMs), including graphene (GR), graphene oxide (GO), reduced graphene oxide (RGO), and graphene quantum dots (GQDs). The coverage includes the principal components of ETLs, which are compact and mesoporous TiO2, SnO2, ZnO and the fullerene derivative PCBM. Basic considerations of solar cell design are provided and the effects of the different ETL materials on the power conversion efficiency (PCE) have been surveyed. The strategy of adding GBMs is based on a range of phenomenological outcomes, including enhanced electron transport, enhanced current density-voltage (J-V) characteristics and parameters, potential for band gap (Eg) tuning, and enhanced device stability (chemical and environmental). These characteristics are made complicated by the variable effects of GBM size, amount, morphology, and distribution on the nanostructure, the resultant performance, and the associated effects on the potential for charge recombination. A further complication is the uncertain nature of the interfaces between the ETL and perovskite as well as between phases within the ETL

    Graphite-Mediated Microwave-Exfoliated Graphene Fluoride as Supercapacitor Electrodes

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    International audienceA graphite-mediated microwave-based strategy was used for solid-state exfoliation of graphite fluoride in a few seconds, followed by a simple yet efficient separation to obtain exfoliated materials based on the density difference between graphite and graphene fluoride in solvent. The microwave-exfoliated graphene fluoride was a few layers thick and electrically conductive. The electrochemical testing of pouch-cell supercapacitors assembled by using the exfoliated graphene fluoride electrodes and a novel microemulsion-based electrolyte showed reasonable performance with typical electrical double-layer capacitance behavior and good rate capability (gravimetric specific capacitance: 3.2 F g−1 at 500 mA g−1 and 3.1 F g−1 at 5000 mA g−1). The BET specific surface areas of the as-exfoliated graphene fluoride are ~60–80 m2 g−1, which could be increased by activation using this simple yet versatile microwave-based method for further improvements on the electrochemical performance

    A Novel Selenium Polysaccharide Alleviates the Manganese (Mn)-Induced Toxicity in Hep G2 Cells and <i>Caenorhabditis elegans</i>

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    Manganese (Mn) is now known to have a variety of toxicities, particularly when exposed to it in the workplace. However, there are still ineffective methods for reducing Mn’s hazardous effects. In this study, a new selenium polysaccharide (Se-PCS) was developed from the shell of Camellia oleifera to reduce Mn toxicity in vitro and in vivo. The results revealed that Se-PCS may boost cell survival in Hep G2 cells exposed to Mn and activate antioxidant enzyme activity, lowering ROS and cell apoptosis. Furthermore, after being treated with Se-PCS, Caenorhabditis elegans survived longer under Mn stress. daf-16, a tolerant critical gene, was turned on. Moreover, the antioxidant system was enhanced as the increase in strong antioxidant enzyme activity and high expression of the sod-3, ctl-2, and gst-1 genes. A variety of mutations were also used to confirm that Se-PCS downregulated the insulin signaling pathway. These findings showed that Se-PCS protected Hep G2 cells and C. elegans via the insulin/IGF-1 signaling pathway and that it could be developed into a promising medication to treat Mn toxicity

    Berberine inhibits the expression of hypoxia induction factor-1alpha and increases the radiosensitivity of prostate cancer

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    ABSTRACT: BACKGROUND: The radiation resistance of prostate cancer remains the primary obstacle to improve patient survival. This study aimed to investigate the effects of berberine, a commonly used natural product, on the radiosensitivity of prostate cancer. METHODS: Prostate cancer cell line LNCaP and DU-145 were subjected to hypoxia and/or ionizing radiation (IR), in the presence or absence of berberine treatment. Cell growth and colony formation, and apoptosis were evaluated. Moreover, LNCaP cells were xenografted into nude mice and subjected to IR and/or berberine treatment. The expression of HIF-1α and VEGF in prostate cancer cells and xenografts was detected by Western blot analysis. RESULTS: Berberine increased radiosensitivity of prostate cancer cells and xenografts in a dose dependent manner, and this was correlated with the inhibition of HIF-1α and VEGF expression. CONCLUSIONS: Berberine may inhibit the expression of HIF-1α and VEGF and thus confer radiosensitivity on prostatic cancer cells. Berberine has potential application as an adjuvant in radiotherapy of prostatic cancer. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1519827543125021

    Red and Processed Meat Intake Is Associated with Higher Gastric Cancer Risk: A Meta-Analysis of Epidemiological Observational Studies

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    <div><p>Background</p><p>Red and processed meat was concluded as a limited-suggestive risk factor of gastric cancer by the World Cancer Research Fund. However, recent epidemiological studies have yielded inconclusive results.</p><p>Methods</p><p>We searched Medline, EMBASE, and the Cochrane Library from their inception to April 2013 for both cohort and case-control studies which assessed the association between red and/or processed meat intake and gastric cancer risk. Study-specific relative risk estimates were polled by random-effect or fixed-effect models.</p><p>Results</p><p>Twelve cohort and thirty case-control studies were included in the meta-analysis. Significant associations were found between both red (RR: 1.45, 95% CI: 1.22–1.73) and processed (RR: 1.45, 95% CI: 1.26–1.65) meat intake and gastric cancer risk generally. Positive findings were also existed in the items of beef (RR: 1.28, 95% CI: 1.04–1.57), bacon (RR: 1.37, 95% CI: 1.17–1.61), ham (RR: 1.44, 95% CI: 1.00–2.06), and sausage (RR: 1.33, 95% CI: 1.16–1.52). When conducted by study design, the association was significant in case-control studies (RR: 1.63, 95% CI: 1.33–1.99) but not in cohort studies (RR: 1.02, 95% CI: 0.90–1.17) for red meat. Increased relative risks were seen in high-quality, adenocarcinoma, cardia and European-population studies for red meat. And most subgroup analysis confirmed the significant association between processed meat intake and gastric cancer risk.</p><p>Conclusions</p><p>Our findings indicate that consumption of red and/or processed meat contributes to increased gastric cancer risk. However, further investigation is needed to confirm the association, especially for red meat.</p></div