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We report the synthesis of nitrogen-doped graphene oxide, with 5.7-7.0 wt % nitrogen doping, from different sizes of precursor graphite and study its effect on the oxygen evolution reaction (OER) activity of IrO

The emergence of Plasmodium falciparum resistance raises an urgent need to find new antimalarial drugs. Here, we report the rational repurposing of the anti-hepatitis C virus drug, alisporivir, a nonimmunosuppressive analog of cyclosporin A, against artemisinin-resistant strains of P. falciparum. In silico docking studies and molecular dynamic simulation predicted strong interaction of alisporivir with PfCyclophilin 19B, confirmed through biophysical assays with a K(d) value of 354.3 nM. Alisporivir showed potent antimalarial activity against chloroquine-resistant (PfRKL-9 with resistance index [Ri] 2.14 ± 0.23) and artemisinin-resistant (PfKelch13(R539T) with Ri 1.15 ± 0.04) parasites. The Ri is defined as the ratio between the IC(50) values of the resistant line to that of the sensitive line. To further investigate the mechanism involved, we analyzed the expression level of PfCyclophilin 19B in artemisinin-resistant P. falciparum (PfKelch13(R539T)). Semiquantitative real-time transcript, Western blot, and immunofluorescence analyses confirmed the overexpression of PfCyclophilin 19B in PfKelch13(R539T). A 50% inhibitory concentration in the nanomolar range, together with the targeting of PfCyclophilin 19B, suggests that alisporivir can be used in combination with artemisinin. Since artemisinin resistance slows the clearance of ring-stage parasites, we performed a ring survival assay on artemisinin-resistant strain PfKelch13(R539T) and found significant decrease in parasite survival with alisporivir. Alisporivir was found to act synergistically with dihydroartemisinin and increase its efficacy. Furthermore, alisporivir exhibited antimalarial activity in vivo. Altogether, with the rational target-based Repurposing of alisporivir against malaria, our results support the hypothesis that targeting resistance mechanisms is a viable approach toward dealing with drug-resistant parasite.

Urban lakes in developing economies face tremendous anthropogenic pressure which tends to modify their role in the regional carbon cycle. This makes it imperative to quantify their carbon budget and identify the underlying factors and processes. Present study aims to understand the seasonal carbon dioxide (CO2) dynamics of an urban lake in a semi-arid subtropical region and identify major controls operating on it. Systematic sampling of Bhalswa lake waters was undertaken in winter and summer of 2017–2018. The hydrochemical data generated were used to determine partial pressure and evasion flux of CO2 using pH and total alkalinity couple. The lake waters show CO2 supersaturation with respect to atmospheric equilibrium and act as a source of CO2 to the atmosphere in both seasons. The average partial pressure of carbon dioxide (pCO2) and CO2 evasion flux observed is 1033.73 ± 229.07 µatm and 6.33 ± 2.23 mmol m−2 d−1, and 1034.99 ± 187.37 µatm and 11.65 ± 3.42 mmol m−2 d−1 during winter and summer, respectively. Neither pCO2 nor CO2 evasion flux shows any significant seasonal difference. For yearly dynamics, dissolved organic carbon, dissolved inorganic carbon and dissolved oxygen act as strong controls on lake water pCO2. While for individual seasons, pH and water temperature act as significant controls. Among various pollution sources, untreated sewage and dairy waste, seepage of polluted groundwater and atmospheric dust impact the lake's carbon dynamics. The present study will help better understand the role of freshwater wetlands of ever-expanding urban areas in the regional carbon cycle of developing economies.

Graphene and heteroatom-doped graphene are potential candidates for high-performance energy storage applications, such as supercapacitors. Herein, we have studied the structure and defect generation in nitrogen-doped reduced graphene oxide (N-rGO), synthesized via pyrolysis of urea in a wide temperature range (600–900 °C). Nitrogen-doped defect densities were analyzed in detail by the deconvolution of the Raman spectrum, where we found the importance of additional I and D’’ peaks. I peak is found to be sensitive to the dopant, and D” peak is consistent with the crystallinity, which are further revealed by X-ray photoelectron spectroscopy and X-ray diffraction measurements. Synthesized N-rGO was then investigated for the supercapacitor electrode. N-rGO synthesized at 800 °C, having low crystallinity (crystallite size 3.44 nm), highest degree of reduction (C/O ratio = 23), high specific surface area (152.3 m2 g−1), and presence of both pseudocapacitive and electric double layer behavior, resulting in highest areal capacitance of 138.4 mF cm−2, lowest self-discharge rate, and exceptional capacity retention of 121.7% after 10,000 cycles of charge–discharge. The synthesized electrode material has also been tested for a symmetric supercapacitor cell showing high specific capacitance 66.8 F g−1 in 0.5 M H2SO4 electrolyte. This study is a first of its kind of structural evaluation and Raman characterization of N-rGO for application in supercapacitor cell.

Surface soil samples (n = 36) from different land use areas (rural, industrial, commercial and residential) of Gurugram were studied for physicochemical properties and trace metal (Cu, Cr, Co, Ni, Pb, and Zn) abundances to identify their sources and spatial distribution over the region. Based on the results obtained, the soils of Gurugram, in general, are sandy (75–85 wt%), alkaline, and unpolluted with moderate pollution at certain sites. The average pH lies near 7.5 in all the land uses. Electrical conductivity in residential (329 μS/cm) soils is almost thrice the value in rural (87 μS/cm) soils. The primary metal of concern is Zn, which is above the permissible limits, followed by Cu and Pb. Common alumino-silicate minerals observed in the soils are quartz, K-feldspar, muscovite and sodic plagioclases. Based on the calculated average geo-accumulation index (Igeo) values of samples, soils of Gurugram, in general, are uncontaminated and have values

Conduction mechanisms in solid polymer electrolytes of Li ion batteries have always been a concern due to their theoretical limitation in conductivity value. In an attempt to increase the ionic conductivity of solid state electrolytes, used in lithium ion secondary batteries (LiBs), we studied the synthesis and conductive properties of a low molecular weight cyclic organoboron crystalline electrolyte. This electrolyte was expected to show better electrochemical properties than solid polymer electrolytes. The electrolyte was doped with LiTFSI salt via two different methods viz. (1) facile grinding of the crystalline sample with lithium salt under a nitrogen atmosphere and (2) a conventional method of solvent dissolution and evaporation under vacuum. The electrochemical properties were studied under specific composition of Li salt. The presence of crystallinity in the electrolyte can be considered as an important factor behind the high ionic conductivity of an all solid electrolyte of this type. Charge–discharge properties of the cell using the electrolyte were investigated in anodic half-cell configuration.

Environmental issues of global warming and depletion of fossil fuels have become significant topics in recent years. Effective utilization of renewable energies such as solar and wind energy is a critical issue to overcome the environmental problems. A large amount of effort has been invested in researches for conversion and storage of surplus energies. One of the prospective candidates is production of hydrogen via water electrolysis in polymer electrolyte water electrolyzer. However, catalytic activity, durability, and cost of water electrolysis systems are inadequate for practical application due to low kinetics and high over-potential of electrode reactions, especially, oxygen evolution reaction (OER) on the anode [1,2]. As OER catalyst, iridium oxide (IrO2) particles have been employed because of its high activity and durability. However, high cost and low abundance of iridium require reduction of iridium loading amount on the catalyst. Recently, we have succeeded to synthesize novel IrO2 nanoparticle with large surface area of IrO2 catalyst, which are supported on carbon nanotubes [3] and heteroatom-doped graphene [4], to improve OER activity. For further improvement of OER activity, we also develop alloy catalyst of IrO2 with other metals, such as ruthenium oxide (RuO2) to enhance the specific activity of the catalyst for OER. In this study, we have synthesized novel alloy nanoparticle catalysts, IrRuOx, supported on the heteroatom (N or B) doped reduced graphene oxide (rGO), IrRuOx/N-rGO and IrRuOx/B-rGO, and evaluated its catalytic activity as active catalysts for OER. The IrRuOx/N-rGO and IrRuOx/B-rGO catalyst were synthesized by hydrothermal method. Briefly, nitrogen- or boron-doped reduced graphene oxide (N-rGO, B-rGO) were prepared by thermal treatment of mixture of urea or boric anhydride and graphene oxide (GO), which was prepared by modified Hummers’ method, at 800 and 1000˚C, respectively, for 60 min. Then, required amounts of metal complexes, H2IrCl6 and RuCl3, and N-rGO, or B-rGO were dispersed in ethanol/water mixture and heated at 80˚C for 6 h. Finally, the mixture was heated at 150˚C in hydrothermal autoclave for 4 h to form IrRuOx nanoparticles. The synthesized catalysts were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and electrochemical methods. The OER activity of the catalysts was examined in 0.5 M H2SO4 solution by linear sweep voltammetry (LSV) using a rotating disk electrode (RDE) system. A TEM image of the IrRuOx/N- rGO catalyst is shown in Figure 1. The IrRuOx nanoparticles were dispersed uniformly on the surface of N-rGO substrate. An average size of the nanoparticles was ca. 1.7 nm. The loading amount of the IrRuOx catalyst is estimated to be approximately 20.1 wt% by EDX measurements. In the case of IrRuOx/B- rGO, average particle size was also ca. 1.7 nm, and the loading amount of the catalyst is 11.7 wt%. In addition, the EDX analysis reveals that the ratio of Ir to Ru of the IrRuOx nanoparticles is proportional to the molecular ratio of starting material compounds, H2IrCl6 to RuCl3. We confirmed the composition of the catalysts by XPS, as shown in Figure 2, and the results consisted with EDX measurement. Furthermore, the XPS results reveal that binding energy of Ir 4f peak on both catalysts was shifted to 0.1 eV lower energy state than that on the catalyst without alloying. The shift of the binding energy of Ir 4f peak reflects the modification of the electronic state of Ir, which affects adsorption energy of O and the catalytic activity for OER. Figure 3 shows mass activity of the prepared catalysts for OER estimated from LSV in 0.5 M H2SO4 solution. Electrochemical measurement reveals that the mass activity of the IrRuOx catalyst is higher than that on the catalyst without alloying. In addition, the catalyst supported on B-rGO has higher activity than the catalyst on non-doped or N-doped GO supports. High activity of the IrRuOx / B-rGO catalyst indicates that alloying IrO2 with RuO2 and heteroatom doping on the support materials improve the catalytic activity for OER. In summary, we successfully prepared the alloy catalysts of IrO2 and RuO2 supported on N-rGO and B-rGO substrate, and the catalysts can be promising candidates as anodes for water electrolysis. References [1] M. Carmo, D. L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy 38 (2013) 4901. [2] J. Cheng, H. Zhang, H. Ma, H. Zhong, Y. Zou, Electrochim. Acta 55 (2010) 1855. [3] R. Badam, M. Hara, H.-H. Huang, M. Yoshimura, Int. J. Hydrogen. Energy, 43 (2018) 18095. [4] M. Hara, R. Badam, G. J. Wang, H.-H. Huang, M. Yoshimura, ECS Trans., 85 (2018) 27. Figure 1

The present study had been conducted to study the shelf life of grapes with coatings of Aloe Vera suspended in water with concentrations of 0, 10, 20 and 30 per cent Aloe veraand was stored in poly packaging and open plates under different temperatures of 0⁰C and 30⁰C in refrigerator and incubator. The data was compared with the original shelf life of grapes to determine the efficiency of the Aloe Vera coating. Aloe Vera based coatings provided good gloss and 20 per cent coating concentration gave the best visual and physicochemical results. It was found that 20 per cent coating concentration of Aloe Vera is the most effective and appropriate for the extension of shelf life of grapes.It was also found that the use of low temperature storage in combination with edible coating and packaging extends marketability by reducing moisture loss.In short, the shelf life of grapes can be increased by using Aloe Vera gel coating and the spoilage due to fungal infection of grapes can be reduced.

Recently, environmental issues such as global warming and depletion of fossil fuels have become important topic, and progress toward sustainable societies with renewable energies such as solar and wind energy is a critical issue to overcome the social problems. Conversion of surplus energies to hydrogen via water electrolysis has attracted attention as energy storage method to utilize renewable energies effectively. However, activity, durability, and cost of catalysts are insufficient for practical application in water electrolysis systems due to high over-potential and low kinetics of electrode reactions, especially, oxygen evolution reaction (OER) on the anode [1-2] for polymer electrolyte water electrolyzer (PEWE). Iridium oxide (IrO2) particles have been used as anode catalysts, because of its high activity and durability for OER. However, decreasing iridium loading amount is required to reduce catalyst cost. In a previous study, we have successfully synthesized novel IrO2 nanoparticle catalyst supported on carbon nanotubes with large surface area of IrO2 catalyst to improved OER activity [3]. For further improvement of OER activity, increasing the specific activity of the catalyst for OER is required. One of the approaches to improve catalytic activity is formation of alloy of iridium with other metals with high activity, such as ruthenium. In the present study, we have synthesized novel alloy nanoparticle catalysts, IrRuOx, supported on the reduced graphene oxide (rGO), as active catalysts for OER. The IrRuOx / rGO catalyst was characterized and evaluated in catalytic activity for OER in sulfuric acid solution. The IrRuOx / rGO catalyst was synthesized by hydrothermal method. Briefly, required amount of metal complexes, H2IrCl6 and RuCl3, and graphene oxide (GO) prepared by modified Hummers’ method were dispersed in ethanol/water mixture and the mixture was heated at 80˚C for 6 h. Then, the mixture was heated at 150˚C in hydrothermal autoclave for 4 h to form IrRuOx nanoparticles. The IrRuOx / rGO catalysts were characterized by transmission electron microscopy (TEM), energy dispersed X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical methods. The OER activity of the IrRuOx / rGO was examined in 0.5 M H2SO4 solution by linear sweep voltammetry (LSV) using a rotating disk electrode (RDE) system. A TEM image of the Ir0.7Ru0.3Ox / rGO catalyst is shown in Figure 1. The Ir0.7Ru0.3Ox nanoparticles with wide particle size distribution were dispersed on the surface of rGO substrate. An average size of the nanoparticles was 1.9 ± 0.8 nm. The loading amount of the Ir0.7Ru0.3Ox catalyst is estimated to be approximately 23.9 wt% by EDX measurements. In addition, the EDX analysis reveals that the ratio of Ir to Ru of the IrRuOx nanoparticles is proportional to the ratio of starting materials, H2IrCl6 and RuCl3. The XRD patterns of the IrRuOx / rGO catalysts with different Ir/Ru ratio are shown in Figure 2. The XRD data shows the (200) peak of IrRuOx is shifted to small angle and became broader with increasing Ir ratio of the catalysts. Furthermore, the XPS results of the IrRuOx / rGO catalysts showed binding energy of Ir 4f peak was shifted to a lower energy state with increasing the ratio of Ru. The XRD and XPS data suggest that nanoparticles of the catalyst form alloy of RuO2 and IrO2. In addition, the shift of the binding energy of Ir 4f peak reflects the modification of the electronic state of Ir, which affects the catalytic activity for OER, by alloy formation with Ru atom. Figure 3 shows linear sweep voltammogram of the IrRuOx / rGO catalyst obtained in 0.5 M H2SO4 solution. Electrochemical measurement reveals activity of the IrRuOx / rGO catalyst for OER is higher than that of the IrO2 / rGO catalyst, especially, onset potential of the reaction is 68 mV lower than that on the IrO2 / rGO catalyst. High activity of the IrRuOx / rGO catalyst indicates that alloying IrO2 with RuO2 improves the catalytic activity for OER. In summary, we successfully prepared the alloy catalysts of IrO2 and RuO2 supported on rGO substrate, and the IrRuOx / rGO catalysts can be a promising candidate as anode for water electrolysis. Acknowledgements This work was supported by JSPS KAKENHI Grant number 17K05969. References [1] M. Carmo, D. L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy 38 (2013) 4901. [2] J. Cheng, H. Zhang, H. Ma, H. Zhong, Y. Zou, Electrochim. Acta 55 (2010) 1855. [3] R. Badam, M. Hara, H.-H. Huang, M. Yoshimura, Int. J. Hydrogen. Energy, 43 (2018) 18095. Figure 1

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