Search

Transition metal selenides (TMS) have excellent research prospects and significant attention in supercapacitors (SCs) owing to their high electrical conductivity, superior electrochemical activity and excellent structural stability. However, the commercial utilization of TMS remains challenge due to their elaborate synthesis. Present study designed a hierarchical cobalt selenide (CoSe2) nanowire array on Ni-foam to serve as a positive electrode for asymmetric SCs (ASCs). The nanowires-like morphology of CoSe2 was highly advantageous for SCs, as it offered enhanced electrical conductivity, plenty of surface sites, and short ion diffusion. The as-obtained, CoSe2 nanowire electrode demonstrated outstanding electrochemical features, with an areal capacity of 1.08 mAh cm−2 at 3 mA cm−2, high-rate performance (69.5 % at 50 mA cm−2), as well as outstanding stability after 10,000 cycles. The iron titanium nitride@nitrogen-doped graphene (Fe-TiN@NG) was prepared as a negative electrode to construct the ASCs cell. The obtained ASCs cell illustrated an energy density of 91.8 W h kg−1 at a power density of 281.4 W kg−1 and capacity retention of 94.6% over 10,000 cycles. The overall results provide a more efficient strategy to develop redox-ambitious active materials with a high capacity for advanced energy-storage systems.

Microbial fuel cell (MFC) is a promising technology for simultaneous wastewater treatment and energy harvesting. The properties of the anode material play a critical role in the performance of the MFC. In this study, graphene oxide was prepared by a modified hummer's method. A thin layer of graphene oxide was incorporated on the carbon brush using an electrophoretic technique. The deoxygenated graphene oxide formed on the surface of the carbon brush (RGO-CB) was investigated as a bio-anode in MFC operated with real wastewater. The performance of the MFC using the RGO-CB was compared with that using plain carbon brush anode (PCB). Results showed that electrophoretic deposition of graphene oxide on the surface of carbon brush significantly enhanced the performance of the MFC, where the power density increased more than 10 times (from 33 mWm−2 to 381 mWm−2). Although the COD removal was nearly similar for the two MFCs, i.e., with PCB and RGO-CB; the columbic efficiency significantly increased in the case of RGO-CB anode. The improved performance in the case of the modified electrode was related to the role of the graphene in improving the electron transfer from the microorganism to the anode surface, as confirmed from the electrochemical impedance spectroscopy measurements.

In this work, Cu2O nanoparticles were successfully prepared onto the surface of two-dimensional graphitic carbon nitride (g-C3N4) by using a simple solution chemistry approach. An environment-friendly reducing agent, glucose, was used for the synthesis of Cu2O NPs onto the surface of g-C3N4 without using any surfactant or additives. The surface composition, crystalline structure, morphology, as well as other properties have been investigated using XPS, XRD, SEM, FTIR, FESEM, EDS, etc. The electrochemical measurements of the prepared materials demonstrated that Cu2O exhibited a weak oxidation activity towards urea, while g-C3N4 has no activity towards urea oxidation. The Cu2O supported on the surface of g-C3N4 (Cu2O-g-C3N4) demonstrated a significant activity towards urea oxidation that reached two times that of the unsupported one. The significant increase in the performance was related to the synergetic effect between the Cu2O and g-C3N4 support. The prepared composite materials demonstrated high stability towards urea oxidation as confirmed from the stable current discharge for around 3 h without any noticeable degradation performance.

A g-C3N4/VC composite material comprising of graphitic carbon nitride (g-C3N4) and Vulcan carbon (VC) with different ratios, i.e., 2:1, 1:1, and 1:2 were prepared through hydrothermal method without using any additives. These composite materials were further utilized as a support for Ni(OH)2 nanoparticles. These materials formed new type of Ni/(g-C3N4/VC) composite materials. The SEM images show the sheet-like structure of the graphitic carbon nitride. Although Ni nanoparticles' electrochemical activity over the surface for graphitic carbon nitride was slightly more compared to Ni supported on the Vulcan carbon, the Ni supported on the different composite supports demonstrated an outstanding activity compared with that over the single supports. Among the different composite ratios of the graphitic carbon nitride to the Vulcan carbon, the one with high Vulcan carbon, i.e., 2:1, exhibited the best performance that is nine-times the current density in comparison to that of Ni over Vulcan carbon at 0.5 V using 2 M urea in 1 M potassium hydroxide. The stability for the prepared Ni over the composite support was high, where the degradation in the current density for more than 2 hours was negligible.

In this work, standalone cobalt dendrites are prepared then doped with graphene flakes by a simple electroplating technique. Microstructural examination using SEM with EDX, as well as Raman spectroscopy measurements, verified the successful formation of graphene. The prepared material exhibit a favorably high electrochemical methanol oxidation activity with an onset oxidation potential of 0.07 V vs. Ag/AgCl, which is significantly lower than that of the Ni (0.35 V vs. Ag/AgCl). The doping process causes a decrease in the ohmic resistance of the material from 3.2 Ohm cm−2 to 2 Ohm cm−2, which consequently resulted in a significant increase in the current density from 35 mA cm−2 to 62 mA cm−2 using 1 M methanol at 0.5 V vs. Ag/AgCl. After two hours of current discharge at 0.5 V vs. Ag/AgCl, the catalyst doped with graphene showed a current density of 62 mA cm−2. This is an eight-times higher than that obtained in the case of the Ni nano-powder. An electrode prepared by depositing the catalyst on the surface of a highly conductive porous Ni foam was successfully used as the anode of a passive air cathode direct methanol fuel cell, demonstrating an open circuit voltage of 0.75 V using 0.25 M methanol in 1 M KOH.

The aim of this study was to test the effects of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) creme, or MI Paste™ (MIP), on nicotine-induced Streptococcus mutans biofilm. The experiment utilized S. mutans biofilm assays with varying concentrations of nicotine and MIP aqueous concentrate levels. First hand exposure to nicotine has been demonstrated to significantly increase S. mutans biofilm formation, while the active component, CPP-ACP, in MIP has been shown to reduce S. mutans biofilm formation. A 24-h culture of S. mutans UA159 in microtiter plates were treated with varying nicotine concentrations (0–32 mg/ml) in Tryptic Soy Broth supplemented with 1% sucrose (TSBS) with or without MIP aqueous concentrate. A spectrophotometer was used to determine total growth absorbance and planktonic growth. The microtiter plate wells were washed, fixed, and stained with crystal violet dye and the absorbance measured to determine biofilm formation. The presence of MIP aqueous concentrate inhibits nicotine-induced S. mutans biofilm formation at different concentrations of nicotine (0–32 mg/ml). The results demonstrated nicotine-induced S. mutans biofilm formation is decreased in the presence of MIP. This provides further evidence about the cariostatic properties of CPP-ACP, the active soluble ingredient in the MIP, and reconfirms the harmful effects of nicotine. Smokers may gain dual benefits from the use of MIP, as a remineralization agent and as a cariostatic agent, by inhibiting nicotine-induced S. mutans biofilm formation.

A simple electrodeposition technique has been used to synthesize Co nanoparticles with a 3D leaf-like morphology at room temperature. The prepared Co material has a layered sheet structure of a few nanometers thickness. The surface area of the Co leaf-like structure is three times higher than that of the Co nanoparticles. The prepared nanoparticles exhibit high activity towards ethanol oxidation in alkaline media with an onset potential of 0 V vs Ag/AgCl, which is one of the lowest reported potentials for a non-precious catalyst. The current density is observed to increase with increasing ethanol concentration from 0.1 M to 2 M, after which it plateaus. Mixing the Co catalyst with Vulcan carbon (20 wt%) resulted in a 50% increase in current discharge at different ethanol concentrations due to the improvement in mass and charge transfer rates as confirmed by EIS measurements. Also, Co deposited in situ on the surface of nickel foam (NF) exhibited a high activity towards ethanol oxidation as a standalone electrode that is 10 times that of bare NF.

Particulate matter (PM) specimens from a traffic site were sampled on Teflon filters using a low volume sampler. The sampling campaign ran over a one-year period with sampling frequency of twice a week for both PM2.5 and PM10. X-ray diffraction (XRD) methods, which are not commonly used in PM analysis, have been utilized successfully to identify crystalline phases present, including secondary pollutants. XRD data confirmed results obtained by X-ray fluorescence, positive matrix factorization modeling, and scanning electron microscopy. PM2.5 consisted mainly of secondary sulfates, like Mascagnite [(NH4)2SO4], Koktaite [(NH4)2Ca(SO4)2·H2O], and Gypsum [CaSO4·2H2O]. For PM10, it was found that the major phases are mostly originating from natural sources, such as dust storms and sea salts, in addition to secondary compounds, such as sodium nitrate. The main phases identified were Calcite, Quartz, Gypsum, Halite, and Palygorskite.

In the present study, an erosion analysis of an industrial pump’s casing and impeller blades has been performed computationally. Effects of various critical parameters, i.e., the concentration and size of solid particles, exit pressure head, and cavitation on the erosion rate density of the casing and blade have been investigated. Commercial codes CFX, ICEM-CFD, and ANSYS Turbogrid are employed to solve the model, mesh generation for the casing, and mesh generation of the impeller, respectively. The Eulerian-Eulerian method is employed to model the pump domain’s flow to solve the two phases (water and solid particles) and the interaction between the phases. Published experimental data was utilized to validate the employed computational model. Later, a parametric study was conducted to evaluate the effects of the parameters mentioned above on the erosion characteristics of the pump’s casing and impeller’s blade. The results show that the concentration of the solid particles significantly affects the pump’s erosion characteristics, followed by the particle size and distribution of the particle size. On the other hand, the exit pressure head and cavitation do not affect the erosion rates considerably but significantly influence the regions of high erosion rate densities.

Due to the rapid increase in their efficiencies, third generation photovoltaics rose to prominence in recent years, and became serious competitors to conventional silicon based and thin film solar cells. This work investigates various techniques to grow and/or deposit copper oxide (CuO) on a copper substrate for utilization as a counter electrode in dye sensitized solar cell (DSSC) applications. Copper has many attractive thermal, electrical and mechanical properties and is widely used in solar thermal applications, but its use is limited in solar photovoltaic cells. The experimental results reported herein have proven the success of growing an intrinsic copper oxide layer on a pure copper substrate. Among the methods, the chemical ageing process followed by heat treatment has resulted in a homogenous and adherent oxide layer that attenuated the electronic conductivity and chemical reactivity of pure, bare copper electrodes. These electrodes are incorporated into solar cells that are constructed and tested against a platinum reference cell. The cells showed comparable short circuit current to their platinum counterparts, with efficiencies of 0.2% compared with 0.5% for platinum under the same conditions. The copper counter electrode with the CuO deposition exhibited good promise, especially when comparing figures of merit (power generated/price) as a cheap and effective alternative to platinum in third generation solar cell applications.

The quest for high performance supercapacitors from the energy-power point of view is commonly addressed from the constituting electrode materials and/or the electrolyte. Carbon-based double-layer capacitors are known for their high power density, whereas pseudocapacitors which use transition metal oxides/nitrides/sulfides or conductive polymers are known for their high energy density. In this work we show that one can modulate the energy storage capability of supercapacitors by mixing at preset ratios two types of carbon materials having two different energy storage capabilities. The time-domain and frequency-domain electrochemical characterization of five symmetric devices, in which electrodes made of carbon nanofibers (CNF) are mixed with cobalt-modified CNF (Co-CNF) at different mass proportions, show that as the Co-CNF content is increased, the effective capacitance, and hence the restored energy, is increased without affecting the power performance of the device. This opens up new opportunities for the modular design of supercapacitor electrodes using a small set of electric double-layer capacitive materials.

A series of BiOF/BiOI heterojunction composites photocatalysts has been prepared via a simple coprecipitation method and characterized by using UV–vis (UV–vis) diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller for determination of the specific surface area and porosity (BET), high resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The enhanced photocatalytic activity for removal of the pharmaceutical compound Diclofenac Potassium commercially available as Voltfast sachets under visible light irradiation was demonstrated by comparing heterojunction prepared composites photocatalysts with that of pure BiOF and BiOI photocatalysts prepared under the same conditions. Based on the experimental conditions, the highest activity was achieved for the composite contains 40% BiOF and 60% BiOI showing comparable activities to that of pure BiOI. To the best of our knowledge, this study is the first to report the preparation of BiOF/BiOI composites photocatalysts and their use in the photocatalytic removal of Diclofenac Potassium from aqueous solution.

Direct urea fuel cell (DUFC) is an attractive and inexpensive method for the simultaneous wastewater treatment (urine and urea-contaminated water) and electricity generation. Many efforts have been made to increase the catalytic activity of Ni-based DUFC anodic catalyst toward urea oxidation, which is considered to be the best non-precious catalyst in alkaline media so far. Alloying Ni with other metals and/or non-metals, and increasing its surface area demonstrated a power of up to 26.9 mW cm−2 at room temperature, which is comparable to that obtained in direct alcoholic fuel cells using high loading of precious catalyst. However, this is still viewed as low-performance. This review presents a comprehensive picture of the mechanism of urea oxidation on Ni-based catalysts, the poisoning effect of catalysts and its possible remedies, as well as the different approaches in preparing highly active catalysts. We also analyze the performance and associated issues of DUFC using newly applied strategies to increase its open-circuit voltage and power output via alternative oxidants and re-designed chemical conditions in the cell.

Oxygen-free copper of >99.95% purity was processed by equal-channel angular pressing at room temperature (RT) for up to 24 passes and then pulled to failure at RT using strain rates from 10−4 to 10−2 s−1. The results show that the microstrain increases with strain at the lower numbers of passes but decreases between 16 and 24 passes. Similar trends were found also for the dislocation density, the Vickers microhardness and the values of the measured yield stresses in tensile testing. X-ray diffraction measurements showed a minor increase in the crystallite size at the high strain imposed by processing through 24 passes. These results demonstrate the occurrence of dynamic recovery at the highest strain. In tensile testing at a strain rate of 10−3 s−1 the results gave a yield stress of ~391 MPa and an elongation to failure of 52% which is consistent with an earlier report using Cu of much higher purity but not consistent with an earlier report using Cu of the same purity.

The harmful effect of carbon pollution leads to depletion of the ozone layer, which is one of the main challenges confronting the world. Although progress is made in developing different carbon dioxide (CO2) capturing methods, these methods are still expensive and face several technical challenges. Fuel cells (FCs) are efficient energy converting devices that produce energy via an electrochemical process. Recently varying kinds of fuel cells are considered as an effective method for CO2 capturing and/or conversion. Among the different types of fuel cells, solid oxide fuel cells (SOFCs), molten carbonate fuel cells (MCFCs), and microbial fuel cells (MFCs) demonstrated promising results in this regard. High-temperature fuel cells such as SOFCs and MCFCs are effectively used for CO2 capturing through their electrolyte and have shown promising results in combination with power plants or industrial effluents. An algae-based microbial fuel cell is an electrochemical device used to capture and convert carbon dioxide through the photosynthesis process using algae strains to organic matters and simultaneously power generation. This review present a brief background about carbon capture and storage techniques and the technological advancement related to carbon dioxide captured by different fuel cells, including molten carbonate fuel cells, solid oxide fuel cells, and algae-based fuel cells.

Microbial fuel cell (MFC) is an emerging method for extracting energy from wastewater. The power generated from such systems is low due to the sluggish electron transfer from the inside of the biocatalyst to the anode surface. One strategy for enhancing the electron transfer rate is anode modification. In this study, iron nanostructure was synthesized on a carbon cloth (CC) via a simple electroplating technique, and later investigated as a bio-anode in an MFC operated with real wastewater. The performance of an MFC with a nano-layer of iron was compared to that using bare CC. The results demonstrated that the open-circuit voltage increased from 600 mV in the case of bare CC to 800 mV in the case of the iron modified CC, showing a 33% increase in OCV. This increase in OCV can be credited to the decrease in the anode potential from 0.16 V vs. Ag/AgCl in the case of bare CC, to &minus, 0.01 V vs. Ag/AgCl in the case of the modified CC. The power output in the case of the modified electrode was 80 mW/m2&mdash, two times that of the MFC using the bare CC. Furthermore, the steady-state current in the case of the iron modified carbon cloth was two times that of the bare CC electrode. The improved performance was correlated to the enhanced electron transfer between the microorganisms and the iron-plated surface, along with the increase of the anode surface- as confirmed from the electrochemical impedance spectroscopy and the surface morphology, respectively.

Oxygen-free copper was processed by equal-channel angular pressing (ECAP) at room temperature for 1, 4 and 8 passes and then the ECAP specimens were further deformed by dynamic testing at 298 K using a strain rate of 10 s−1. Experiments were conducted to investigate the influence of the initial microstructures induced by ECAP on the subsequent grain refinement and mechanical properties after dynamic testing. The results show the strength of copper increased with increasing numbers of ECAP passes and a significant additional grain refinement was produced in the ECAP specimens through the dynamic testing. Thus, the initial grain sizes after ECAP for 1, 4 and 8 passes were ~16, ~4.4 and ~2.9 μm, respectively, and these values were reduced to ~400, ~330 and ~300 nm by dynamic testing, The grains were refined by conventional dislocation processes in the 1-pass specimen but there was evidence for dynamic recrystallization in the specimen processed by 8 passes.

Exploration of novel strategies for fabricating SERS substrates attracted enormous research potential as achieving high sensitivity, reproducibility along with cost effectiveness is really challenging. Herein, we have fabricated hierarchical silver nanoprism/graphene oxide/silicon nanowire (Ag/GO/SiNWs) arrays as surface-enhanced Raman scattering (SERS) sensors for the effective detection of atrazine. Homogenous and vertically aligned SiNWs have been successfully synthesized using silver assisted chemical etching. Further, Ag/GO/SiNWs arrays were assembled by subsequent spin-coating of GO followed by drop-casting deposition of Ag nanoprisms. Micro-structural properties of as-fabricated nano-arrays have been well examined by scanning electron and atomic force microscopic techniques. Nanowire bunches have been decorated by GO layers; which further facilitates homogenous deposition of Ag nanoprisms. Using rhodamin 6G as probe molecule, high SERS activity and excellent reproducibility of as-fabricated substrates have been demonstrated. High efficiency of 3.2 × 108 and was obtained for the fabricated sensors; attributed to the synergetic charge transfer between GO and Ag nanoprisms on high surface area Si nanowires. Charge transfer mechanism that leading to enhanced surface plasmon resonance effect of the as-fabricated array was established as well. Further, these low cost Ag/GO/SiNWs sensors exhibited ultrasensitive detection of pollutants such as methylene blue and atrazine residues down to picomolar levels; these can serve as potential chemical sensors for rapid monitoring of environmental pollutants in trace levels.

We report the synthesis of aryldiazonium tetrachloroaurate(III) salts [X-4-C6H4N≡N]AuCl4 (X = F, Cl, Br, I, CN, NO2) and their mild reduction to covalently functionalized nanoparticles. The synthesis of the salts was carried out by the oxidation of anilines, dissolved in HCl, using sodium nitrite followed by the exchange of the counter anion with [AuCl4]- in water. In another procedure, the anilines were protonated with H[AuCl4] in acetonitrile followed by one-electron oxidation using nitrosonium salt [NO]X (X = BF4−, PF6−). Raman and ATR-FTIR spectroscopy displayed the diazonium νN≡N and Raman showed the tetrachloroaurate νAu-Cl stretching frequencies. X-ray crystal structure of [NO2-4-C6H4N≡N]AuCl4 salt showed N≡N bond distance typical of a triple bond. Gold-aryl nanoparticles were constructed by the mild chemical reduction of the diazonium gold(III) salts using 9-borabicyclo[3.3.1]nonane (9-BBN). Nanoparticles hydrodynamic diameter, elemental composition, dynamics information, and stability data were determined. Transmission electron microscopy (TEM) measurements showed limited aggregation due to the small suppressing organic shell. However, dynamic light scattering (DLS) measurements showed considerable aggregation in acetonitrile. X-ray photoelectron spectrometry (XPS) showed the gold core in zero oxidation state and manifested the gold-organic shell connectivity. The –N=N-aryl interfacial formation on the gold surface can be ruled out since the N1s peak assigned to the diazonium moiety showed no sign in the XPS nitrogen area in addition to its absence in the ATR-FTIR spectra. Raman spectroscopy measurements showed a peak assigned to gold-carbon bonding supported by density functional calculations (DFT) on Au20-C6H4-CN model.

There is a tremendous interest in the fabrication of novel hemocompatible nanoparticles for applications in theranostics. In this context, bovine serum albumin (BSA) conjugates with the water-soluble and super robust gold-aryl nanoparticles truncated with carboxylic functionals were synthesized. The gold-aryl nanoparticles were fabricated by the mild reduction of the diazonium gold(III) salt [HOOC-4-C6H4N≡N]AuCl4. The gold core size and the presence of BSA sheath encapsulating Au−COOH nanoparticles were concluded from transmission electron microscopy (TEM). Clear spectral changes supported by quantitative X-ray photoelectron spectrometry (XPS) surface analysis are visible: the C1s/Au4d intensity ratio increased sharply and the gold features were very well attenuated after BSA attachment, which brings more nitrogen essentially due to NH-C = O peptide links. The conjugation of BSA with Au−COOH nanoparticles resulted in the isoelectric point (pI) change from 4.7 to a range of 4.1-5.0. The robustness of the bioconjugates can be concluded based on the high ζ-potential values and the resistance to drastic pH conditions. The high encapsulation efficiency percentage (EE%) calculated using Bradford protein assay was in a range of 90.0–94.6% under physiological pH values. Taken together, overall studies imply the presence of interaction between the Au−COOH nanoparticles and BSA. In this study we investigated the interaction of gold nanoparticles and their BSA conjugates with human red blood cells (RBCs), which might cause cell deformity and hemolysis. To elaborate on the uniqueness of the bioconjugates, they showed negligible hemolysis or morphology deformation to cells membrane visualized using light and phase contrast microscopes. Quantitative measurements of hemoglobin leached out of the cell membrane using UV–vis showed negligible hemolysis. The high physiological stability of the conjugates fosters their applications in intravenous drug delivery supported by the long blood circulation half-life.

In this experiment, the visible light reactive photosensitizer (PS) derived from chlorophyllin sodium copper salt has been synthesized via a simple synthetic route. The enhanced photocatalytic activity for the decomposition of the pharmaceutical compound Diclofenac Potassium available as Voltfast sachets under visible light irradiation was demonstrated by comparing the photocatalytic decomposition of Diclofenac Potassium in the presence and absence of the new synthesized visible light photosensitizer under the same photocatalytic conditions. Based on the experimental results, higher activity was achieved for the sample composed of the new synthesized visible light photosensitizer. The photosensitized sample using the new derivative of chlorophyllin sodium copper salt exhibited approximately 21 times higher rate when compared with that of Chlorophyllin sodium copper salt sample. This photocatalytic activity can be attributed to the enhanced visible light harvesting of the new derivative of Chlorophyllin sodium copper salt.

This work presents the simple synthesis and simultaneous deposition of graphene nanoplatelets onto pure copper substrates for use as capacitive deionization electrodes. Copper is cheap and abundant material that can easily be fabricated into electrodes but suffers from high reactivity in solution with unpredictable consequences. The deposition of turbostratic graphene layer using the proposed high energy centrifugal milling technique introduces a chemically inert, but electrically conductive surface layer that extends the operational lifetime of the copper working electrode many folds compared to the bare pure copper one. In the trials presented here the operation of the pure copper electrode degraded almost instantly as the electrochemical cell was activated, compared to a smooth 60-minute operation of its graphene-coated counterpart. The graphene electrode was successful in reducing the solution conductance by more than 12% for the test period, which renews the interest in copper as an effective counter electrode for capacitive deionization applications. The quality of graphene deposition is verified via Raman spectroscopy, while the characterization of the copper chloride is done via X-ray Diffraction. The deionization process resulted in the production of Cu2Cl(OH)3 deposits on the copper electrode, which is mentioned as a viable method of producing it, although it is an unexpected result of this work.

Carbon-based nanofluids are viewed as promising thermal fluids for heat transfer applications. However, other properties, such as electrical conductivity and electrochemical behavior, are usually overlooked and rarely investigated despite their importance for the overall performance characterization of a given application. In this study, we synthesized PAN-based carbon nanofibers (CNF) by electrospinning, and characterized them using electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Thermoelectrical and electrochemical measurements were carried out on nanofluids. We found that, although CNF nanofluids exhibit good thermal and electrical properties with a negligible corrosive effect, the suspensions tend to sediment within a few days. However, acid treatment of CNF (F-CNF), which resulted in the shortening of the fibers and the appearance of surface-oxygenated species, made F-CNF-based nanofluids exhibit superior stability in water that extended for more than 90 days, with consistent and superior thermal and electrical properties.

One of the main challenges facing the development of urea fuel cells is the low catalytic activity of the anode. Ni decorated carbon nano-fiber is a promising anode catalyst in urea fuel cells. In this study, we have investigated the effect of Cd doping of Ni decorated carbon nano-fiber on catalytic activity for urea oxidation. The catalyst was prepared by heat treatment of electrospun nano-fibers containing different percentages of Ni and Cd acetates in poly(vinyl alcohol) under an inert atmosphere at 850 °C. The initial percentages of the Cd acetate to Ni acetate in the polymer solution was set at 5, 10, 30, 50 and 70 wt.%. The introduction of Cd significantly improved the electro-catalytic activity for urea oxidation. The sample that was prepared with initial 50 wt.% Cd acetate showed the best activity for urea oxidation activity using different urea concentrations, 0.33 M–3 M. The introduction of Cd improved both the quality and the number of active sites for the urea oxidation as seen from the shift of the anodic peak potential and anodic peak current density, respectively.

Metal chalcogenides have received significant attention as electro-catalysts in different applications, due to their superior electrical conductivity and good thermal and mechanical stabilities. In this work, the optimum monocrystalline Ni-P and Ni-C, C (Se, S, O) nanosheet (NS), prepared on nickel foam as standalone anodes for urea fuel cells was introduced. The activity was investigated ex-situ and in-situ the cell. The results demonstrated that the non-oxide metal forms, i.e., Ni–P, Ni–S, and Ni–Se, have superior oxidation activity than the Ni layered double hydroxide (Ni-LDH) and Ni–O. In addition, Ni–Se showed the most superior urea oxidation activity among all prepared catalysts. Although the onset potential of all the samples was around 0.35 V vs Ag/AgCl, a steady current of 195 mAcm−2 was recorded after 120 min using Ni–Se, which is two times higher than that of Ni–S, five times higher than Ni–O, and ten times higher than Ni-LDH. The superior activity of the Ni–Se was related to its unique crystalline structure and the high porous morphology. The performance of Ni–Se electrode under actual direct urea fuel cell (DUFC) operation using a nonprecious a Prussian blue cathode revealed 33 mWcm−2 power, which is, one of the highest power outputs in DUFCs equipped with Ni-based anodes at room temperature, as far as the authors know.

Mesoporous Co dendrites prepared by electroplating have a surface area of 145 m2g−1, which is three times that of Co nanoparticles. The Co dendrites demonstrate superior urea oxidation activity compared to Ni or Co nanoparticles prepared using chemical reduction. The onset potential with Co dendrites is around 0 V “vs. Ag/AgCl” using 2 M urea, that is remarkably lower than 0.35 V “vs. Ag/AgCl” for Ni catalyst at optimum urea concentration of 0.5 M. The current produced in case of the Co dendrites using 2 M urea at 0.5 V “vs. Ag/AgCl” was six times that obtained using Ni. The in-situ measurements using Co dendrites on the Ni foam as anode and Prussian blue as cathode catalyst demonstrated a 21 mWcm−2 at 20 °C. These are the first reported results for a complete Ni-free nonprecious anode and cathode catalysts under real fuel cell operation with high performance comparable to those obtained using precious catalyst under same conditions.

Oxygen-free copper of 99.95Â wt.% purity was severely deformed at room temperature by two modes of severe plastic deformation, equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). ECAP was performed using 4, 16 and 24 passes, and HPT was performed using 1/2, 1 and 10 turns. The results show that while recovery occurs during both ECAP and HPT processing, copper shows a faster recovery rate with HPT processing than ECAP. The occurrence of recovery was observed at an equivalent strain exceeding â¼12 that led to an enhancement in the uniform plastic deformation. The influence of recovery behaviour on the mechanical properties was investigated using X-ray diffraction, microhardness and tensile testing. Keywords: Ductility, Equal-channel angular pressing, High-pressure torsion, Recovery, Strain rate sensitivity, Work hardening

We used a multistage PIXE inertial impactor with nine different aerodynamic diameter ranges (between 16 and 0.06 μm) to sample indoor particulate matter (PM). X-ray fluorescence (XRF) measurements performed at cutoff diameters (CoDs) of 0.25, 0.5, 1, 2, 4, and 8 μm were used to identify elements in various size fractions. Anthropogenic sources were the dominant sources for fine and ultrafine particle sizes. The XRF results show that natural sources also contribute to the fine and ultrafine fractions of pollutants. Scanning electron microscopy and energy-dispersive system analysis were performed on membranes having PM CoDs of 4, 2, 1, 0.5, and 0.25 μm. Elemental mappings show the membranes with PM of CoDs 0.25 and 0.5 μm having S as a dominant element, confirming the results obtained with XRF. Strong correlation among maps of S, N, and O show that ammonium sulfate is the major constituent at these size fractions. Other elements such as Si, Ca, Fe, Al, and Mg show up in smaller amounts at these size fractions but increase for membranes with larger particles. For size fractions larger than 0.5 μm, there is a good correlation between the elemental maps of these elements and oxygen, indicating that these elements exist mostly in oxide forms. The absence of clear N signals and the correlation between the Ca and S maps indicate that S in these size fractions is not due to ammonium sulfate. The presence of Mg, K, Cl, and Na at these CoDs shows that these elements are due to salts originating from sea breeze.

Bipolar electrochemistry is used as an economical, single-step, and scalable process for the oxidation of a wireless graphite substrate, and the subsequent electrophoretic deposition of graphene oxide thin film on a second wireless substrate. An all-solid-state symmetric double-layer capacitor (EDLC) using binderless reduced graphene oxide electrodes exhibited outstanding reversibility and capacitance retention over 18000 cycles, as well as superior capacitive behavior at far-from-dc frequencies (for example 45 and 47 μ F cm-2 ), effective capacitances at 75 and 189 Hz, respectively (computed using a series resonance network with ideal inductors), compared to 55 μ F cm-2 at close-to-dc (computed from cyclic voltammetry at 10 mV s-1 ). This makes the device well-suited for ac filtering applications. A one-hour thermal treatment of the electrodes at 900 °C under vacuum increased the capacitance 13-fold (719 μ F cm-2 ) at close-to-dc, which decreased to 185 and 150 μ F cm-2 as the frequency was increased to 37 and 106 Hz, respectively These properties make this device suitable for both reasonable dc energy storage and higher frequency applications.

Graphene is a 2-D carbon material showing considerable prominence in a wide range of optoelectronics, energy storage, thermal and mechanical applications. However, due to its unique features which are typically associated with difficulty in handling (ultra-thin thickness and hydrophobic surface, to name a few), synthesis and subsequent deposition processes are thus critical to the material properties of the prepared graphene films. While existing synthesis approaches such as chemical vapor deposition and epitaxial growth can grow graphene with high degree of order, the costly high temperature and/or high vacuum process prohibit the widespread usage, and the subsequent graphene transfer from the growth substrates for deposition proves to be challenging. Herein, a low-cost one-step synthesis and deposition approach for preparing few-layer graphene (FLG) on flexible copper substrates based on dry ball-free milling of graphite powder is proposed. Different from previous reports, copper substrates are inserted into the milling crucible, thus accomplishing simultaneous synthesis and deposition of FLG and eliminating further deposition step. Furthermore, while all previously reported high energy milling processes involve using balls of various sizes, we adopt a ball-free milling process relying only on centrifugal forces, which significantly reduces the surface damage of the deposition substrates. Sample characterization indicates that the process yields FLG deposited uniformly across all tested specimens. Consequently, this work takes graphene synthesis and deposition a step closer to full automation with simple and low-cost process.

Nanoparticle (NP) synthesis by biological systems is more cost-effective, safe, and environmentally friendly when compared to currently used chemical and physical methods. Although many studies have utilized different plant extracts to synthesize NPs, few studies have incorporated living plants. In this study, silver nanoparticles (AgNPs) were synthesized exogenously by Tephrosia apollinea living plant system under the combined stresses of silver nitrate and different levels of drought stress simulated by Polyethylene glycol (PEG) (0, &minus, 0.1, &minus, 0.2, and &minus, 0.4 MPa for three and six days). Biomass, cell death, and H2O2 content were evaluated to determine the toxicological effect of the treatments on the plant. More severe effects were detected in day 6 plants compared to day 3 plants, and at higher drought levels. UV-visible spectrum, energy dispersive X-ray spectroscopy, X-ray diffraction, scanning electron microscope, and Fourier transform infrared spectroscopy were used to detect and characterize the T. apollinea synthesized NPs. The shapes of the NPs were spherical and cubic with different phytochemicals being the possible capping agents. Broth microdilution was used to determine the antimicrobial activity of the NPs against Escherichia coli and Staphylococcus aureus. In this case, antimicrobial activity increased at higher PEG concentrations. Bactericidal effects were observed against E. coli, while only bacteriostatic effects were detected against S. aureus.

A novel g-C3N4/VC composite was prepared by adopting simple hydrothermal treatment without using any additives from bulk g-C3N4 and Vulcan XC-72R (VC) in different ratios. Further, the resulting composite materials were used as a support for the synthesis of Cu2O NPs. The use of g-C3N4/VC not only acts as a support for the Cu2O NPs but also it forms a new type of novel composite materials, i.e., Cu2O-g-C3N4/VC. Various ratios (1:1, 1:2 and 2:1) of g-C3N4 and VC were used for the synthesis of three different types of the composite materials such as Cu2O-g-C3N4/VC(1:1), Cu2O-g-C3N4/VC(1:2), and Cu2O-g-C3N4/VC(2:1). The structures, surface properties, elemental compositions, and morphologies of synthesized materials were analyzed by various instrument methods such as FTIR, XRD, FESEM, Raman, EDS, BET, etc. Then the electrochemical activity of those resulting Cu2O-g-C3N4/VC composite materials were examined towards urea oxidation. The catalytic activity of Cu2O-g-C3N4/VC composite materials were found to be influenced by the variation of the g-C3N4 to VC ratio. The Cu2O-g-C3N4/VC(1:2) composite presented a higher current density (25.3 mAcm−2) as compared to that of Cu2O-g-C3N4/VC(1:1) (21.2 mAcm−2) and Cu2O-g-C3N4/VC(2:1) (13.5 mAcm−2) at 0.6 V using 2 M urea. The observed higher catalytic activity of this Cu2O-g-C3N4/VC (1:2) composite material compared to Cu2O-g-C3N4/VC (1:1) and Cu2O-g-C3N4/VC (2:1) is due to its higher surface area arising from different morphology compared to that of others. The Chronoamperometric measurements of the composite materials demonstrated their high stability upto 2 h without any degradation in the current density.

A biocompatible graphitic carbon nitride (g-C3N4) was prepared on the surface of carbon brush fiber (CB) via a facile one-step preparation method. The prepared g-C3N4 formed a composite with the carbon brush’s fibers (g-C3N4@CB), as shown from the XRD analysis. The g-C3N4@CB was used as an anode in a yeast-based microbial fuel cell (MFC), and demonstrated an outstanding performance compared to plain CB. An anode potential of −0.27 V “vs. Ag/AgCl” and an open-circuit voltage of 0.77 V was obtained in the case of the composite electrode, compared to −0.1 V vs. Ag/AgCl and 0.62 V, respectively, in the case of the CB. The cell using the composite electrode demonstrated a maximum power of 772 mWm−2, which is twelve times that obtained using the CB. The outstanding performance of the composite electrode can be credited to the biocompatibility of the composite anode and its roughness, which improved the yeast biofilm formation and decreased the ohmic resistance. This is the first report involving the application of g-C3N4 in a yeast-based MFC, and it demonstrated promising results which can be used for other types of MFCs.

Sum peaks, escape peaks, and diffraction peaks are considered artificial or spurious peaks in energy dispersive X-ray spectrometry. Experimental examples are given, which showed that escape and diffraction peaks can add up to become sum peaks. These artificial peaks are not weak, and great care must be taken to differentiate them from peaks due to impurity or trace elements. The relationship between the intensity of a sum peak and the original peaks is illustrated using computer simulation as well as probability theory. Copyright © 2016 John Wiley & Sons, Ltd.

Workers in gasoline stations may experience health symptoms due to inhalation to benzene, toluene, ethyl benzene, and xylene (BTEX) species in their work environment. Air samplers installed in gasoline stations indicate exposure concentration during the workday as high as 225–723 μg benzene/m3, in excess of the NIOSH exposure limits of 135 μg benzene/m3 (adjusted for the actual exposure time of workers in this study). According to a deterministic health assessment, there was an elevated cancer risk for workers due to exposure to benzene (4.2 × 10−4 to 1.4 × 10−3) and ethyl benzene (1.1 × 10−4 and 3.5 × 10−4), which were greater than the acceptable limit of 1 × 10−6. Stochastic exposure assessment with a Monte Carlo simulation revealed serious carcinogenic risks to all workers in the gasoline station, regardless of whether they were operating the gasoline pumps or doing other tasks, such as collecting money. In response to a health questionnaire, the dominant symptoms reported by gasoline station workers were headache (50%), depression (40%), fatigue (25%), and throat irritation (20%). We recommend better ventilation systems to remove BTEX species from the environment, either by installing fans or building gasoline stations in locations with good natural air exchange.

This case study is of drilling extended reach 6" lateral (more than 7,000 ft) in thin multi -layered carbonate gas reservoirs with a novel approach of tapping the multiple target reservoir units in dual points starting from top reservoir unit to the base unit and placing the well back to top reservoir unit in steps. The well trajectory was planned with Top-Bottom-Top (TBT) approach, starting from top to bottom layers and steering back to the top layer in stair-step trajectory. The MWD-LWD BHA was selected to continuously monitor the porosity to avoid exiting from porous subunits – owing to the thinness of sweet spot in reservoir subunits with the range of 4 to 5 ft. only. Azimuthal Resistivity tool with LWD triple combo was used while geosteering the well to assess and map the subunit boundary as there is good resistivity contrast between porous subunits and bounding stylolite. LWD Pressure Formation Tester was used to record the current reservoir pressure in the target reservoir for the purpose of optimization of the mud weight to avoid the risk of differential sticking due to higher overbalance. The differential sticking was experienced in the previous wells due to higher mud weight and overbalance. Hence, mud weight optimization helped to drill more than 7000 ft of 6" horizontal section with a complex stair-step well trajectory design. The first 5,000 ft of horizontal section have been drilled successfully using distance to boundary Azimuthal resistivity tool in addition to density-neutron tool. While in the remaining of 2,000 ft horizontal length of drain hole, the radioactive source tool was replaced with source less BHA of azimuthal resistivity and sonic tools. The reason for replacing source tool with sourceless tool is the risk of string stuck up with radioactive source in the BHA. This may be caused by complex stair-step well trajectory, reservoir pressure uncertainty and any down hole complication. The target reservoir identified for this approach has low average permeability of less than 1 mD with limited sweep area. The target is thin stacked reservoir subunits of thickness ranging from 4 to 8ft. The Subunits porosity range is 3 to 17% and are distinctly bounded by thin non-porous stylolite. The risk of drilling with complex well trajectory was handled by constant maintenance of dogleg severity (DLS) less than 2deg/100ft. Each subunit was targeted with very gentle inclination and inter-bedded stylolites were cut with higher inclination to achieve more than 90% of reservoir contact. The project has resulted in reservoir characterization in selective areas with selective drain. Being laterally heterogeneous, the Top-bottom-top approach provides the scope of selective drain in the reservoir along the well path. A higher production performance is expected from this approach as each subunit was targeted according to their reservoir properties. This case study proves to be novel especially in tight reservoirs with limited drainage area, where cost have been optimized by reducing the number of wells to be drilled by tapping the reservoirs in dual drainage points with a single well.

With the increased use of metal nanoparticles (NPs), their access to the food chain has become a main concern to scientists and holds controversial social implications. This research particularly sheds light on copper nanoparticles (CuNP), as they have been commonly used in several industries nowadays. In this study, we investigated the phytotoxicity of CuNP on cucumber (Cucumis sativus) plants grown hydroponically. Atomic Absorption Spectroscopy (AAS), X-Ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM) analysis confirmed that C. sativus treated with CuNP accumulated CuNP in the plant tissues, with higher levels in roots, with amounts that were concentration dependent. Furthermore, genotoxicity was assessed using Random amplified polymorphic DNA (RAPD) technique, and our results showed that CuNP caused genomic alterations in C. sativus. Phenotypical, physiological, and biochemical changes were assessed by determining the CuNP treated plant's total biomass, chlorophyll, H2O2 and MDA contents, and electrolyte leakage percentage. The results revealed notable adverse phenotypical changes along with decreased biomass and decreased levels of the photosynthetic pigments (Chlorophyll a and b) in a concentration-dependent manner. Moreover, CuNP induced damage to the root plasma membrane as determined by the increased electrolyte leakage. A significant increase in H2O2 and MDA contents were detected in C. sativus CuNP treated plants. Additionally, copper-zinc superoxide dismutase (Cu-Zn SOD) gene expression was induced under CuNP treatment. Overall, our results demonstrated that CuNP of 10-30 nm size were toxic to C. sativus plants. This finding will encourage the safe production and disposal NPs. Thus, reducing nano-metallic bioaccumulation into our food chain through crop plants; that possesses a threat to the ecological system.

Airborne particulate matter (PM) pollutants were sampled from an urban background site in Sharjah, United Arab Emirates. The fine fraction (PM2.5) (particulates with aerodynamic diameters of less than 2.5 μm) was collected on 47-mm Teflon filters and analyzed using a combined set of non-destructive techniques in order to provide better understanding of the sources of pollutants and their interaction during transport in the atmosphere. These techniques included gravimetric analysis, equivalent black carbon (EBC), X-ray fluorescence, scanning electron microscopy, and X-ray diffraction. Generally, the PM2.5 concentrations are within the limits set by the World Health Organization (WHO) and the United States (US) Environmental Protection Agency. The EBC content is in the range of 10–12% of the total PM concentration (2–4 µg m−3), while S (as ammonium sulfate), Ca (as calcite, gypsum, and calcium carbonate), Si (as quartz), Fe, and Al were the major sources of PM pollution. EBC, ammonium sulfate, Zn, V, and Mn originate from anthropogenic sources such as fossil fuel burning, traffic, and industrial emissions. Natural elements such as Ca, Fe, Al, Si, and Ti are due to natural sources such as crustal materials (enhanced during dust episodes) and sea salts. The average contribution of natural sources in the total PM2.5 mass concentration over the sampling period is about 40%, and the contribution of the secondary inorganic compounds is about 27% (mainly ammonium sulfate in our case). The remaining 22% is assumed to be secondary organic compounds.

This paper reports on the thermal oxidation of electrodeposited copper microstructures from a 0.2 M H2SO4 + 0.4 M CuSO4 aqueous solution on a copper substrate for selective solar thermal absorbers applications. A study of the morphological properties and crystalline structure of the deposited/annealed layer through SEM-EDS and powder XRD revealed the formation of self-assembled cubic Cu2O microstructures. The copper oxide layer was optically examined by virtue of a spectrometer in the spectral Vis–NIR range. The surface roughness induced by the existence of the globular microstructure has been seen to enhance the absorptance of the material. Around two to three-fold enhancement of optical surface absorption is achieved in the wavelength range of 400–1000 nm versus an air-grown copper oxide.

Summary Thanks to their high power density and degree of reversibility, supercapacitors are electrochemical devices that narrow the gap between secondary batteries and traditional dielectric capacitors in the traditional Ragone plot. However, their use is still hindered by their capability to achieve higher energy density. In this work, we present a one-pot synthesis procedure of composite graphitic carbon flake-supported NiO for electrochemical energy storage application. We used cathodic contact glow discharge electrolysis by applying 120 Vdc terminal voltage between a thin Pt wire, slightly submerged in an aqueous solution of NiSO4(H2O)6 + Na2SO4, and a large surface area carbon graphite anode. Strong active species generated within the micro-plasma volume locally reduce the nickel precursors to form NiO materials, while at the anodically polarized graphite rod, the forces holding the graphene layers together are weakened by ion/solvent intercalation producing micrometer-sized graphitic carbon flakes. The morphological characterization is carried out by electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, and micro-Raman spectroscopy. Cyclic voltammetry, constant-current charge/discharge, and electrochemical impedance spectroscopy in 5 mol l−1 KOH solution are carried out to evaluate the electrochemical energy storage performance of the material. We show that carbon flake-supported NiO exhibits the dual combination of electric double-layer capacitance with faradic behavior, giving 495 F g−1 specific capacitance at 2 A g−1 current density. Copyright © 2015 John Wiley & Sons, Ltd.

Cupric oxide is an inexpensive material with electrochemical behavior that can be used for energy storage applications. Here, we prepare CuO materials by a simple bipolar electrochemical process in deionized water, where a high voltage is applied between two stainless steel feeding electrodes symmetrically surrounding an electrically floating copper plate. CuO is mainly formed in the locally alkaline region facing the anodic pole of the copper plate, where electro-dissolved Cu2+ undergo successive reactions of complexation–dehydration with OH− ions. The morphology, composition, and phase structure of as-prepared materials were characterized by scanning electron microscopy, powder X-ray diffraction, micro-Raman spectroscopy, and Vis-near-IR spectroscopy. We have found that CuO materials are self-assembled in three-dimensional dendritic structures that can grow up to millimeters in size. The electrochemical characterization in 1 mol L−1 KOH by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy shows a capacitive behavior of CuO structures, with an average capacitance value reaching 202 F g−1 at 10 A g−1, giving an energy density of 7.0 W h kg−1 for a power density of 2.5 kW kg−1. At 20 A g−1 current density, the materials exhibit 90% capacitance retention over 2000 charge/discharge cycles with a coulombic efficiency exceeding 95%.

Exosomes released from cancer cells support metastasis and growth of recipient cells and increase their resistance to chemotherapy. Therapeutic targeting of exosomes is a promising area in cancer research. Our aim is to test the effect of the mast cell stabilizer ketotifen on exosomes release from cancer cells and how this can modify their response to doxorubicin. Exosomes release from three cancer cell lines (MCF7, HeLa and BT549) was assessed by scan electron microscope and exosomes quantification kit. Doxorubicin export within exosomes was monitored flurometrically and cellular sensitivity to doxorubicin ± ketotifen was measured by sulphorhodamine-B and colony formation assays. The three cell lines release different amounts of exosomes with the highest quantity released from BT549 followed by MCF7 and then HeLa. Ketotifen (10 µmol L-1) reduced exosomes release in all three cell lines with different efficiency (HeLa>MCF7>BT549). Doxorubicin export via exosomes was highest in BT549, lower in HeLa and lowest in MCF7 cells. Pretreatment with ketotifen sensitized the cells to doxorubicin (HeLa>MCF7>BT549) with a sensitization factor of 27, 8 and 1.25 respectively. Increased sensitivity of cells to doxorubicin by ketotifen was proportional to its effect on exosomes release. Our data is the first report of ketotifen modulating exosomes release from cancer cells and opens the avenue for exosomes-targeting cancer therapy. The differential effects of ketotifen on doxorubicin exosomal export in the cell lines studied, suggests an opportunity of pharmacological enhancement of doxorubicin anti-tumor activity in some but not all cancer types.

In this paper, we report on the time-dependent development of cupric oxide films by chemical modification of copper substrates submerged horizontally in a room temperature 75 mmol/L ammonia solution at pH 11, over a period of nine days. Morphological and structural characterization of the oxide-substrate tandems were carried out by SEM–EDX and XRD, while the relative directional spectral absorptivity and reflectivity were determined by Vis–NIR spectrometry. The ageing process, controlling both the color and morphological structure of the predominately amorphous-CuO/Cu, has positively contributed to the enhancement of spectral absorptivity, while band gap values evolve from 1.29 to 1.39 eV for exposure times from 36 to 168 h.