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Hydroxyapatite (Hap) doped or embedded with silver has shown improved bactericidal properties, and its mechanical properties were greatly improved by doping or impregnating Hap with metals such as Magnesium or Zinc, or by impregnating Hap with metal oxides such as MgO, or ZnO. This work describes the preparation of Ag-ZnO-Hap nanocomposites with 4 different Ag-ZnO–Ca mole ratios. XRD, FTIR, SEM, and TEM analysis of all prepared materials identified Hap as the only crystalline phase present in all samples exhibiting a uniform rod-like morphology with particles in the 20–40 nm size range. Microwave Plasma-Atomic Emission Spectroscopy confirmed the presence of zinc and silver in all embedded Hap samples. The antibacterial activity was tested against two different strains; Escherichia coli (E. coli (MV10Nal), and Gram-negative Aggregatibacter actinomycetemcomitans (A.a). The mechanical testing consisted of evaluating breaking force, work of fracture, and brittleness/ductility of Hap and Ag/ZnO/Hap composites. Our study clearly shows that reinforcing Hap with silver and zinc oxide yields superior bactericidal and mechanical properties.

Hydrogen production through hydrolysis of sodium borohydride (NaBH4) by using metal catalysts is promising for fuel cell applications. Nickel (Ni) and its alloys are favorable due to their high catalytic activity, relatively low cost and availability. In present study, the effects of temperature, pH, reduction rate and reducing agent concentration, which significantly affect the catalyst performance, were investigated using the response surface methodology (RSM). A mathematical model was derived according to results which were obtained from four-level orthogonal Taguchi L16 (44) experimental design used for the optimization of multiple parameters in the process. From the RSM analyses, that compatible with the predicted experimental results, maximum hydrogen generation rate (HGR) 49.81 L min(-1) gcat(-1) was obtained temperature of 278.12 K, pH of 5.52, reducing agent concentration of 85.96 NaBH4.water(-1) and reduction rate of 6.82 mL min(-1). Analysis of variance reveals that both pH and rate of reduction have significant effect than the temperature on the HGR. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Microfluidization is a unique high-pressure homogenization technique combining various forces such as high-velocity impact, high-frequency vibration, instantaneous pressure drop, intense shear rate, and hydrodynamic cavitation. Even though it is mainly used on emulsion-based systems and known for its effects on particle size and surface area, it also significantly alters physicochemical and functional properties of macromolecules including hydration properties, solubility, viscosity, cation-exchange capacity, rheological properties, and bioavailability. Besides, the transformation of structure and conformation due to the combined effects of microfluidization modifies the material characteristics that can be a base for new innovative food formulations. Therefore, microfluidization is being commonly used in the food industry for various purposes including the formation of micro- and nano-sized emulsions, encapsulation of easily degradable bioactive compounds, and improvement in functional properties of proteins, polysaccharides, and dietary fibers. Although the extent of modification through microfluidization depends on processing conditions (e.g., pressure, number of passes, solvent), the nature of the material to be processed also changes the outcomes significantly. Therefore, it is important to understand the effects of microfluidization on each food component. Overall, this review paper provides an overview of microfluidization treatment, summarizes the applications on macromolecules with specific examples, and presents the existing problems.

Efficient hydrogen generation is a significant prerequisite of future hydrogen economy. Therefore, the development of efficient non-noble metal catalysts for hydrolysis reaction of sodium borohydride (NaBH4) under mild conditions has received extensive interest. Since the transition metal boride based materials are inexpensive and easy to prepare, it is feasible to use these catalysts in the construction of practical hydrogen generators. In this work, temperature, pH, reducing agent concentration, and reduction rate were selected as independent process parameters and their effects on dependent parameter, such as hydrogen generation rate, were investigated using response surface methodology (RSM). According to the obtained results of the RSM prediction, maximum hydrogen generation rate (53.69 L. min−1gcat-1) was obtained at temperature of 281.18 K, pH of 5.97, reducing agent concentration of 31.47 NaBH4/water and reduction rate of 7.16 ml min−1. Consequently, after validation studies it was observed that the RSM together with Taguchi methods are efficient experimental designs for parameter optimization.

Viscoelasticity of corn zein is associated with the formation of β-sheet secondary structures; however, studies of the fundamentals of this conformational change are limited due to zein insolubility and poor analytical resolution. Here, changes in soluble zein conformation were evaluated as the protein self-assembles in increasingly hydrophilic solvents to the concentration just before aggregation and precipitation. Circular dichroism spectra of zein showed that α-helix structures decrease in favor of random coil and β-sheets with increases in water content in an ethanol-water system, similar to observations of zein when it becomes viscoelastic in dough systems. This was further supported by changes in Thioflavin T fluorescence emission spectra and intrinsic viscosity measurements. Two widely recognized molecular models for α-zein (hairpin and superhelical conformations) were tested at 75 and 45% ethanol concentration using molecular dynamics simulation for agreement with experimental results. Increase in solvent hydrophilicity increased β-sheets and reduced distance between backbone anomeric carbons only for hairpin model, suggesting it to be the more valid of the two. These findings emphasize the importance of transformation to β-sheets during zein self-assembly and provide further insight into the mechanisms by which the protein is functionalized into viscoelastic systems.

Olive mill wastewater (OMW) is produced in large quantities in the production of olive oil with the three-phase method. This waste, which is not biodegradable and characterized by a heavy organic load containing toxic components (such as phenols), is usually given to aqueous receptors or soil, either directly (untreated) or treated inadequately. Biologically active phenolic compounds that inhibit biodegradation of this waste are toxic at high concentrations, especially for microorganisms, but have positive effects with strong antioxidant properties on human health when properly isolated and properly concentrated. Hydroxytyrosol (HT) is one of the most interesting and abundant compounds among the biophenols present in OMW. According to this study, a newly synthesized nanomaterial, graphene oxide (GO), has been utilized for the separation of HT and total biophenolic substance from OMW. Graphene oxide from graphite oxidation was synthesized using a modified Hummer’s method. In order to understand how GO behaves during thermal degradation, thermogravimetric/differential scanning calorimetry analyses were performed. Two-parameter and three-parameter equilibrium isotherm models and kinetic models have been used to determine the mechanism of kinetic sorption and adsorption type. Thermodynamic data indicate that the adsorption process is exothermic, applicable and spontaneous.

With the discovery of graphene, the necessary synthesis studies have been carried out for the use of graphene oxide (GO) as an adsorbent to remove toxic materials. In this study, GO nanopowder was ...

In this study, a novel nanomaterial, graphene oxide (GO), which has never been used as an adsorbent in the separation of hydroxytyrosol (HT), has been utilized. GO nanosheets were synthesized by graphite oxidation naturally, which is known as modified Hummer's method. Then, the material obtained was characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) methods. Adsorption of HT from aqueous media onto synthesized GO was found to be >85% under optimum conditions (with 0.01 mg GO in 10 mL of solution at 150 rpm for 1440 min, where pH is 9). On the other hand, equilibrium (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Redlich-Peterson) and kinetic (pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion) models have been applied for analysis and representation of data. Thermodynamic findings point out that the related adsorption system is exothermic, applicable and spontaneous. © 2019 117M848 The authors thank The Scientific & Technological Research Council of Turkey (TÜBİTAK) for financial support for this research project (Grant number: 117M848 ).

A series of thin Pt-Co films with different metal ratios were deposited by using the sequential cosputtering directly on a commercial hydrophobic carbon paper substrate at room temperature and in ultra-high vacuum (UHV) conditions. Their electrocatalytic properties toward the oxygen reduction reaction were investigated in 0.5 M $H_2 SO_4$ solution by means of cyclic voltammetry (CV) and linear sweep voltammetry (LSV) on rotating disc electrode (RDE). The results showed that Pt particles, deposited by dc-magnetron gun, surround the large Co-clusters deposited by rf-magnetron gun. In addition, the increase of Co content led to an increase in the electrochemical active surface area $(EASA) from 23.75 m_2 /gPt to 47.54 m_2 /gPt for pure Pt and Pt:Co (1:3),$ respectively, which corresponded the improvement of the utilization of Pt by a factor of 1.91. This improvement indicated that the sequential magnetron cosputtering was one of the essential technique to deposit homogeneous metal clusters with desirable size on the gas diffusion layer by adjustment plasma parameters.

Recent studies show that carbonaceous materials have gained interest because of their superior features over the alternative adsorbents. Therefore, it is of great value to synthesize novel carbonaceous adsorbents. In the present study, graphene oxide nanopowders (GON) were synthesized through a modified Hummer’s method. The material has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) methods. Naproxen has been selected as the model pharmaceutical to investigate the adsorption performance of GON. The highest adsorption removal was found to be 65.28% under the optimum conditions (0.03 g of GON for the adsorption of 10 mg/L naproxen solution at 100 rpm mixing the speed of shaking bath). The relevant adsorption system was an exothermic, spontaneous, and chemisorption process depending on the kinetic (pseudo-first order, pseudo-second order, intraparticular, and Elovich models), equilibrium (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Harkin-Jura, and Halsey isotherm equations), and thermodynamic parameters.

There are two main obstacles preventing the commercialization of polymer electrolyte fuel cells (PEMFCs) such as low durability of support material and high cost of metal catalyst. It is necessary to use support materials to increase the distribution of the catalysts and to be accumulated more in the active area. Despite widespread usage of carbon as support material, carbon suffers from oxidation under fuel cell working conditions. In the past several years, researchers have given many efforts to develop new support materials, which have high surface area, and are electrically conducting and chemically stable. Among all support materials, graphene, thanks to two-dimensional graphite form, has unique physical and electrical properties; because of these superior features, graphene can be an ideal support material for nanoparticles. In this study, we updated the Hummers' method by addition of certain amount of potassium dichromate in addition to potassium permanganate as oxidant agent. After that, graphene oxide was uniformly coated with conductive polyaniline (PANI) polymers by the liquid-liquid interface polymerization method. Finally, PANI/GO composite was pyrolyzed at certain temperature and time to reduce graphene oxide to few layers of graphene. Electrochemical active surface area (EASA) of commercially obtained Pt/VulcanXC-72 was calculated as 29.5m(2)/gPt, while EASA of Pt/RGO catalysts was 63.7m(2)/gPt.

In this study, graphene oxide (GO) nanosheets were evaluated for the recovery of biophenols from an agricultural biomass, olive leaf. Modified Hummer's method was used to synthesize GO by natural oxidation of graphite. The adsorbent was characterized by several novel analysis methods such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). On the other hand, optimization of the adsorption process was applied utilizing multivariate statistic technique such as Response Surface Methodology (RSM) in order to consider any possible interaction between variables with less number of experiments as well as to model a response affected by several variables. The outcome of the present study indicates that the optimum conditions for the adsorption of were 4.57/10 of pH together with 24.62/30 °C of temperature and 3 mg of GO to achieve the maximum yields of each dependent variable such as total biophenol content (TBC) and the most prevalent compound, oleuropein (OC). The verification of the calculated models was held by several error function analysis. © 2017 Elsevier B.V.

Nanocomposites stand out as promising materials in many fields due to their properties such as strength, hardness, thermal stability, and lightness. Introducing self-healing ability to polymer nanocomposites provides new guidelines for strong, sustainable, and durable materials. Microcapsule-based self-healing materials work independently of an external stimulus such as pH, heat, light and solvent. In this paper, we developed autonomously self-healing UV-cured polyurethane graphene oxide nanocomposite coatings by means of efficient and useful copper-catalyzed azide-alkyne (CuAAC) click chemistry. Low molecular weight tetra-arm azide was successfully capsulated within poly(vinyl formal) capsules. Alkyne functional graphene-oxide reinforced nanocomposites containing azide microcapsules were prepared through photo-polymerization. The self-healing ability and anti-corrosion properties of the nanocomposites were studied after the damage occurred. The self-healing experiments show that the microcapsules provided a self-healing efficiency of around 70% after 24 h. Chemical, morphologic, mechanical, and thermal properties of the films were investigated. Furthermore, the electrochemical analysis of films showed that the microcapsule containing films has a higher polarization resistance and a lower corrosion current.

Electrochemical properties of porous nickel (Ni) foam, electrodeposited zinc (Zn) on Ni foam (Ni–Zn) and electrodeposited reduced graphene oxide (rGO) on Ni–Zn foam electrodes (Ni–Zn-rGO) in 6 M KOH electrolyte were investigated. Cyclic voltammetry (CV) and galvanostatic charge–discharge cycling (GCD) techniques were used to carry out the redox interactions, and cycling capacitive properties of the electrodes in KOH solution. Platinum (Pt) and gold (Au) foil were used as a counter electrode and the current collector in the electrochemical measurements, respectively. The specific capacitances of the electrodes were found from the GCD measurements as 155, 722 and 1820 F/g for Ni, Ni–Zn and Ni–Zn/rGO electrodes at the current density of 1 A/g, respectively. Scanning electron microscope (SEM) images of the three electrodes were also taken into account to associate all the electrochemical measurements. These results clearly show that specific capacitance values highly increased after the deposition of Zn and rGO to Ni electrode.

WOS: 000423584300006, Phenol is considered to be a priority pollutant due to its toxicity and carcinogenic effect. Thus, innovative and effective methods have been developed to remove undesired phenol from wastewater. Membrane processes are one of the innovative and effective methods used for the removal of phenol from wastewater. In this study, we investigate the effect of carbon and graphene oxide (GO) coating on phenol removal efficiencies of microfiltration, ultrafiltration, and nanofiltration membranes. Obtained results show the removal efficiencies of all membranes increase with rising pressure. Among all membranes, the carbon-coated nanofiltration membrane (NF90) showed the highest performance with a removal efficiency of 99% under a pressure of 6 bars. The physico-chemical properties of the coated and uncoated membranes were investigated by using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction and contact angle techniques (WCA).

Performance of cathode materials in microbial fuel cell (MFC) from dairy wastewater has been investigated in laboratory tests. Both cyclic voltammogram experiments and MFC tests showed that Pt-Ni cathode much better than pure Pt cathode. MFC with platinum cathode had the maximum power density of 0.180 Wm(-2) while MFC with Pt: Ni (1:1) cathode produced the maximum power density of 0.637 Wm(-2), even if the mass mixing ratio of Pt is lower in the alloy were used. The highest chemical oxygen demand (COD) removal efficiency was around 82-86% in both systems. The cyclic voltammogram (CV) analyses show that Pt: Ni (1:1) offers higher specific surface area than Pt alone does. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) results showed that entire Pt: Ni (1:1) alloys can reduce the oxygen easily than pure platinum, even though less precious metal amount. The main outcome of this study is that Pt-Ni, may serve as a alternative catalyst in MFC applications. (C) 2015 Elsevier Ltd. All rights reserved.

A series of thin Pt films were deposited by dc magnetron sputtering directly on a commercial hydrophobic carbon paper substrate having a thin microporous Vulcan-XC72 layer or upon a thin Ti sublayer sputtered on the top of the microporous carbon film. The electrocatalytic properties of the sputtered Pt films toward the oxygen reduction reaction were investigated in 0.5 M H2SO4 solution and in a hydrogen PEM fuel cell. The catalyst with ultralow Pt loading of 22 mu g cm(-2) deposited on a 33 angstrom thick Ti sublayer is robust, mechanically stable, possesses highly developed surface area and improved catalytic efficiency. Its performance as a MEA cathode in a single hydrogen PEM fuel cell (577 mA cm(-2) at 0.4 V cell voltages and a maximum power of 0.954W) proved to be much superior compared to that of MEA with the same cathode Pt loading but without Ti sublayer (173 mA cm(-2) at 0.4 V, 0.231W, respectively). (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.