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In this study, metallic copper (Cu) nanowires are synthesized by reducing thermally synthesized CuO nanowires under an indigenously developed hydrogen plasma system. The X-ray diffraction (XRD) results of the plasma-synthesized nanowires indicate the presence of metallic copper [(111) and (200)] and the field emission scanning electron microscopy (FESEM) further affirms the findings by presenting a stark difference in contrast of the nanowires before and after plasma treatment with diameters of 50 and 100 nm, respectively. The nanowires are studied for hydrogen evolution reaction in a neutral medium and they show excellent performance than the previously reported studies on bulk copper, with an overpotential of 210 mV at a current density of 10 mA/cm2 and an exchange current density of 60 exp-5 A/cm2 which is an order of magnitude larger than the reported values on bulk copper. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy indicates that the surface of the nanowires is highly rich in metallic copper resulting in better electrochemical performance of the metallic Cu nanowires in a neutral environment.

Here, we report a new post-synthesis modification strategy for functionalizing reduced graphene aerogels (rGAs) towards an exceptional CO2 separation performance. 1-N-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) was impregnated on a rGA, prepared by reducing GA at 700 degrees C, at various ionic liquid (IL) loadings of 5, 10, 30, and 50 wt%. The resulting composites were characterized in deep detail by X-ray photoelectron spectroscopy, X-ray diffraction, N-2 physical adsorption measurements, scanning electron microscopy, Fourier transform infrared and Raman spectroscopies, and thermogravimetric analysis. Results indicated the presence of interactions between the rGA surface and the anion of the IL, potentially improving the CO2 affinity. Volumetric gas adsorption measurements using these materials showed that the deposition of [BMIM][PF6] on rGA surface at an IL loading of 50 wt% boosts the CO2/CH4 selectivity by more than 20-times, exceeding an absolute value of 120, a remarkably higher CO2/CH4 selectivity compared to that of other functionalized materials under similar operating conditions. Tunability of both the IL structure and the surface characteristics of rGA offer a tremendous degree of flexibility for the rational design of these IL/rGA composites towards high performance in gas separation applications., Scientific and Technological Research Council of Turkey (TÜBİTAK); Koç University Seed Fund Program; HEC-Pakistan Scholarship; TARLA; METU Prof. Dr. Mustafa N. Parlar Education and Research Foundation's 2019 Research Incentive Award

Magnetorheological fluids (MRFs) are smart materials with a reversible and fast transition from a liquid to a semi-solid state when an external magnetic field is applied (magnetorheological effect). The sedimentation of micron-sized magnetic particles in commercial MRFs is a crucial problem limiting the long-term use in industrial applications. Here, we develop a new MRF based on commercial 140-CG LORD (R) with the addition of surface functional superparamagnetic iron oxide nanoparticles (SPIONs). These new bidisperse MRFs are comprised of either poly(acrylic acid) (PAA) coated SPIONs or lauric acid (LA) coated SPIONs and micron-sized fatty acid-coated magnetic particles of the commercial MRF. SPIONs have specific coatings to interact with the fatty acid coating of the micron-sized Fe-particles. Sedimentation behaviour and the magnetorheological properties of these bidisperse MRFs with 6-12 wt % SPION were examined. Bidisperse MRFs improved the stability and redispersibility of MRFs. Bidisperse MRFs with 12 wt% SPION-PAA showed similar or better magnetorheological behaviour than the commercial MRF despite lower content of the micron size Fe-particles. Hence, a combination of magnetizable nano and micron-sized particles and utilization of correct surface chemistry that allows their favourable interaction improves the stability of MRFs without sacrificing magnetic response but even by improving it. (C) 2020 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Even though metallic biomaterials have long been utilized as the key materials in biomedical applications due to their exceptional mechanical properties, corrosion and bacterial infection problems place a limit on their prolonged clinical applications. In order to overcome such problems, surface modification of the implants via exerting a durable and protective coating containing antibacterial agents is crucial. In this study, undoped and Ag-doped Ti1.5ZrTa0.5Nb0.5W0.5 refractory high-entropy alloy (RHEA) films with a thickness of 1.10 μm were deposited on Ti6Al4V alloys through RF magnetron sputtering technique. The influence of the deposited film and embedding Ag nanoparticles on microstructure, mechanical properties, and electrochemical behavior was investigated. The microstructural findings revealed an amorphous structure with cauliflower-like morphology for deposited films. Coated specimens showed a significant improvement in surface mechanical properties such as elastic modulus and hardness. Doping Ag nanoparticles in the deposited film increased the roughness and contact angle of the specimens due to the evolution of Ag nanoparticles. Furthermore, electrochemical investigations revealed that undoped and Ag-doped deposited films remarkably improved the corrosion resistance of uncoated substrate; after the films deposition process, the corrosion rate of the specimens decreased 2.3 to 2.8 orders of magnitude compared to the uncoated substrate. Also, embedding Ag nanoparticles notably increased the polarization resistance of deposited films.

Mesoporous graphene aerogel (GA) supported Pt nanoparticles with narrow size distribution were prepared via supercritical deposition (SCD) using supercritical CO 2 (scCO 2 ). Pt(cod)me 2 precursor was dissolved in scCO 2 and adsorbed onto GA at 35 °C and 10.7 MPa. The Pt precursor was converted to its metal form under atmospheric pressure at various temperatures. The effects of precursor conversion temperature (400, 600, and 800 °C) on the structural properties of the composites were investigated using Raman Spectroscopy, XRD, XPS, and TEM. The average particle size increased from 1.2 to 2.9 nm when the conversion temperature was increased from 400 to 800 °C. The electrocatalytic activity of the samples towards the Oxygen Reduction Reaction were evaluated using cyclic voltammetry (CV) and rotating disc electrode (RDE) measurements. SCD helped to preserve the textural properties of the GA after the Pt nanoparticle deposition, and thus Pt/GA converted at 600 °C exhibited an enhanced mass activity of 30.6 mA mg Pt −1 , outperforming the mass activities reported in the literature for Pt/GA electrocatalysts prepared using conventional routes.

Behçet's disease (BD) is characterized by recurrent oro-genital ulcers, mucocutaneous lesions, and serious organ involvement. We investigated the salivary microbiome in BD using high-throughput sequencing of the 16S rRNA V4 region. Stimulated saliva samples were collected from 31 BD patients and 15 healthy controls, and in 9 BD patients, a second saliva sample was collected following dental and periodontal treatment. Sequence analysis identified a total of 908 operational taxonomic units (OTUs) present across all samples. Patients had a microbial community structure that is significantly less diverse than healthy controls. The most overabundant species in BD was Haemophilus parainfluenzae, while the most depleted included Alloprevotella rava and species in the genus Leptotrichia. Periodontal treatment improved oral health indices in BD but had no short-term effect on bacterial community structure. Neither the BD-associated genetic risk locus within the HLA-B/MICA region nor being on immunosuppressive medications explained the differences between patients and controls.

Zn(NO3)2 concentration had been reported to be significantly influential on electrodeposition of ZnO structures. In this work, this issue is revisited using hydrothermal–electrochemical deposition (HED). Seedless, cathodic electrochemical deposition of ZnO films is carried out on ITO electrode at 130 °C in a closed glass reactor with varying Zn(NO3)2 concentration. Regardless of the concentration of Zn2+ precursor (0.001–0.1 M) in the deposition solution, vertically aligned 1-D ZnO nanorods are obtained as opposed to electrodepositions at lower temperatures (70–80 °C). We also report the effects of high bath temperature and pressure on the photoelectrochemical properties of the ZnO films. Manipulation of precursor concentration in the deposition solution allows adjustment of the aspect ratio of the nanorods and the degree of texturation along the c-axis; hence photoinduced current density. HED is shown to provide a single step synthesis route to prepare ZnO rods with desired aspect ratio specific for the desired application just by controlling the precursor concentration.

Electrochemical capacitors have attracted great interest because they can maintain high power density along with high energy density. In this study, manganese oxides were electrodeposited onto nickel mesh substrate under hydrothermal conditions to be used as electrodes for electrochemical capacitors. Obtained Mn 3 O 4 (hausmannite) phase was electrochemically oxidized to mixed-valent MnO 2 during potential cycling. MnO 2 electrodes showed excellent pseudocapacitative behaviour in cyclic voltammetry (CV) and charge-discharge (CD) measurements. Produced electrodes had specific capacitance of 518.8 F g −1 at 0.1 mA cm −2 . Also, the electrodes maintained their capacitative properties at high scan rates/current densities and after 10,000 cycles of CV measurement.

In this work we studied metal chalcogenide sensitization of ZnO by electrochemical deposition which provides a fine electric contact between metal sulfide and the oxide. Deposition conditions to prepare the CdS/ZnO and Ag 2 S/ZnO films with optimized photoelectrochemical (PEC) properties are investigated. Effect of deposition technique, time, Mn-doping and post-annealing on photoresponse of the fabricated films are discussed. A short circuit current density of 1.42 mA/cm 2 and an open circuit potential of −1.39 V (overall power conversion efficiency of 0.81%) have been achieved for the annealed Mn-doped CdS/ZnO electrode which is prepared by potensiostatic deposition. Potensiostatic deposition yields Ag 2 S in Acanthite form which is accompanied by ZnO degradation and the photoelectrode exhibits considerably enhanced and widened light absorption but lower overall power-conversion efficiency.

We present a simple, single step process to produce hierarchical ZnO architectures which involves introduction of Cd(CH3COO)2 and electrochemical deposition under hydrothermal conditions. Effect of Cd(CH3COO)2 concentration on the morphology of ZnO films were examined. A variety of hierarchial structures were obtained including micrometer-long micro-channels, 1D twinned structures, 2D ZnO crosses and star flower-like structures by modifying [Cd(CH3COO)2/Zn(II)] ratio. Besides surface morphology, the growth mechanism giving rise to the particular structures, crystal structure, phase purity, and chemical binding characteristics of the deposits were examined.

In the current study, influence of sodium dodecyl sulfate (SDS) on the crystallization of Zn–Al layered double hydroxide (LDH) was investigated. Depending on the SDS concentration coral-like and for the first time ring-like morphologies were obtained in a urea-hydrolysis method. It was revealed that the surfactant level in the starting solution plays an important role in the morphology. Concentration of surfactant equal to or above the anion exchange capacity of the LDH is influential in creating different morphologies. Another important parameter was the critical micelle concentration (CMC) of the surfactant. Surfactant concentrations well above CMC value resulted in ring-like structures. The crystallization mechanism was discussed.

In this study, we have demonstrated the synthesis and delamination of a rarely studied NiGa layered double hydroxide (LDH) system. Hydrothermal treatment under agitation conditions at 200 °C for 4 h resulted in the formation of highly crystalline NiGa LDHs in a shorter time than those synthesized without agitation. The LDH was delaminated into the individual nanosheets in formamide. The most significant finding in this study is the electrochemical behavior of interlayer ferricyanide anions intercalated with the layer-by-layer (LBL) assembly method. The morphology of LBL film with one layer is also monitored with atomic force microscopy. The cyclic voltammogram is similar to potassium metal hexacyanoferrate systems with its unique two-peak wave. Raman spectrum of the film revealed that the metal center of the interlayer cyano complex is in interaction with the Ni 2+ of the host layer. It was concluded that the two-peak cyclic voltammogram of the film is a result of two different forms of the hexacyanoferrate in the interlayer.

We have developed a new process for the synthesis of a layered niobium sulfide that involves heating K{sub 4}Nb{sub 6}O{sub 17}.3H{sub 2}O with a H{sub 2}S/N{sub 2} gas mixture. It was confirmed that heating the starting layered oxide at 750 deg. C for 10 h under the gas flow yielded a highly crystalline, single-phase K{sub 0.34}(H{sub 2}O){sub 0.7}NbS{sub 2}. The layered sulfide slabs had a large plate-like shape. Potassium ions in the interlayer of K{sub 0.34}(H{sub 2}O){sub 0.7}NbS{sub 2} could be exchanged with protons by stirring in 2 M H{sub 2}SO{sub 4}. It was found that the proton in the proton-exchanged form can be easily exchanged with other cations. The proton-exchanged form was exfoliated into NbS{sub 2} nanosheets by ultrasonication in water. According to the atomic force microscopy (AFM) images, NbS{sub 2} nanosheets had a thickness of around 4 A, which roughly corresponded to the thickness of a single NbS{sub 2} host layer. NbS{sub 2} nanosheets could be restacked with the intercalation of Eu{sup 3+} or tetrabutylammonium ions by an electrostatic self-assembly deposition (ESD) technique. - Graphical abstract: Potassium-intercalated layered niobium sulfide has been synthesized by heating a corresponding layered niobate in a H{sub 2}S/N{sub 2} mixture gas. Proton-exchanged layeredmore » niobium sulfide has been exfoliated into NbS{sub 2} mono-nanosheet. The NbS{sub 2} mono-nanosheet was restacked with cationic species by an electrostatic self-assembly deposition.« less

The hydrothermal synthesis of magnesium–gallium layered double hydroxides (Mg/Ga LDHs) was studied under static and agitated conditions. Not only well-crystallized and large-sized Mg/Ga LDHs having hexagonal morphology were obtained but also the reaction time was comparatively decreased from 24 to 2 h by means of agitation during hydrothermal synthesis. In static conditions, mainly GaOOH and magnesite phases were formed. The elemental analysis results show that the final Mg/Ga ratio is significantly different from the initial ratio. The reason was attributed to the difference in the hydrolytic behavior of Mg2+ and Ga3+. Furthermore, the anion exchange studies with glycine, dodecyl sulfate, ferrocyanide and ferricyanide were performed to investigate the intercalation behavior of the anions into Mg/Ga LDHs. In addition, delamination of Mg/Ga LDHs was performed in formamide for the glycine exchanged forms. Large size of nanosheets thus obtained can be utilized in the fabrication of functional thin films.

Electrochemical reaction of Ag + in the interlayer of various layered oxides was investigated in this study. Intercalation of Ag + into the interlayer of layered oxides was carried out with layer-by-layer self assembly (LBL) method. Film deposition with LBL method was monitored by UV–vis spectra. Ag + intercalated layered oxide films showed very unique characteristics when compared to other similar Ag + exchanged zeolite and clay electrodes. First of all, the peaks are very sharp and clear, which shows that the redox reaction in the interlayer is fast. In addition, there is an energy gap between the onset potentials of redox reactions, which is different from the behavior of other electrodes. The formation of the energy gap was assigned to the energy barrier in the host layer. Furthermore, pH and scan rate controlled experiments showed that the reaction has diffusion controlled mechanism and diffusion of H + or K + into interlayer is believed to be contributing to the redox reaction indirectly. The slope of I p versus ν 1/2 curves shows that redox reaction is reversible. The unique electrochemical behavior of the Ag + intercalated layered oxide thin films may lead into the design of new nanocells using the potential energy difference between two different redox couple.

Electrostatic self-assembly deposition (ESD) results in the intercalation of Ru(bpy) 3 2+ or methylene blue (MB) into the niobate layered oxide right after the cations come into contact with [Nb 6 O 17 ] 4− nanosheets. Monolayers can be obtained by the exfoliation of proton exchanged K 4 Nb 6 O 17 (KNbO) in an aqueous tetrabutylammonium (TBA) solution as revealed by the atomic force microscopy micrographs. UV-vis spectra show that intercalated films are able to absorb in the visible light range. Heat-treatment of Ru(bpy) 3 2+ resulted in the red-shift in the absorption spectra, which was assigned to the enhancement in the interaction between the complex molecules and [Nb 6 O 17 ] 4− host layer. Intercalated niobate layered oxides are able to produce photocurrent as a result of the electron transfer from the excited guest molecule to the host layer under visible light illumination. Ru(bpy) 3 2+ intercalated niobate layered oxide shows photocatalytic activity under visible light illumination to produce H 2 from water–methanol solution.

Photoelectrochemical measurements of TiO2, NaTaO3, and Cr or Sb doped TiO2 and SrTiO3 photocatalysts were carried out in H2 and O2 saturated electrolytes in order to evaluate the reverse reactions during water photolysis. The poor activity of TiO2 as a result of reverse photoreactions of O2 reduction and H2 oxidation was revealed with the respective high cathodic and anodic photocurrents. The rise in the photocurrents at NaTaO3 after La doping was in harmony with the doping-induced increase in the photocatalytic activity. NiO loading suppresses the O2 photoreverse reactions, which declines photocatalytic activity, and/or promotes the photo-oxidation of water, because the O2 photo-reduction current was scarcely observed near the flatband potential. Photocurrents of O2 reduction and H2 oxidation were observed under visible light for the Cr and Sb doped SrTiO3 and TiO2, respectively. These phenomena are in harmony with the previous reports on the photocatalysts examined with sacrificial reagents.