Nature Of Electrolyte Research Articles

Corrosion behavior of pure titanium anodes in saline medium and their performance for humic acid removal by electrocoagulation.

The corrosion behavior of Ti electrodes and the dependence of their anodic dissolution with the experimental conditions, namely pH, current density (j) and supporting electrolyte nature, have been investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests have been performed. It has been found that pH has a relevant effect on the electrochemical dissolution of Ti. In chloride medium, metal dissolution was partially caused by pitting corrosion and the corrosion potential was shifted to more cathodic values. Conversely, in phosphate medium, corrosion was inhibited by the formation of a compact passive layer of titanium hydroxide/phosphate. Further, the mechanisms of sacrificial Ti anode dissolution during the electrocoagulation process are discussed. The influence of the supporting electrolyte, pH and j on the effectiveness of the electrocoagulation process for humic acid (HA) removal was assessed. Under optimized conditions, total decolorization was achieved in 60 min, eventually attaining 94% total organic carbon (TOC) removal.

A New Approach for Voltammetric Determination of Nefopam and its Metabolite

AbstractIn present paper we described a new simple voltammetric method of determination of nefopam alkaloid and its metabolite – N‐oxide. N‐oxide of nefopam is reduced at the dropping mercury electrode (DME) and silver solid amalgam electrodes (AgSAE), which can effectively replace mercury and chemically modified electrodes. The reduction consists of two one‐electron stages each accompanied with one proton transfer. N‐oxide of nefopam can be obtained from nefopam substance by oxidation with potassium peroxymonosulfate. It was studied the effect of various factors on N‐oxide quantitative yield (pH, oxidation duration, reagents concentration) as well as on the reduction of N‐oxide at DME and p‐AgSAE (pH, the nature of background electrolyte, potential and time of accumulation). It was showed that the reduction current linearly increased with increasing of concentration of analgesic. Limit of quantiation is 10−6 mol L−1 at DME and 10−7 mol L−1 at p‐AgSAE. The developed method was applied for the analysis of commercial drug solution for injection “Nefopam” with recovery of 96.7 %, as well as for the spiked human urine samples. Excellent repeatability with a relative standard deviation below 5 % was achieved.

Investigations of lithium ion conducting polymer blend electrolytes using biodegradable cornstarch and PVP

Solid polymer electrolytes used in energy storage devices based on Cornstarch and Poly (vinyl Pyrrolidone) blend incorporated with lithium acetate was prepared using the solution casting method. XRD results confirmed that the amorphous nature of the as-prepared polymer electrolyte was increased by addition of salt. 80 wt % Cornstarch/20 wt % PVP/60 wt % lithium acetate added polymer blend system attains better amorphous nature than others. At ambient temperature, 60 wt % of lithium acetate added system has better bulk conductivity of 3.52 × 10−5Scm−1 over the frequency range of 42 Hz to 1 MHz using AC impedance spectroscopy studies. The dielectric analysis is confirmed that the higher conducting sample was having high dielectric constant and low relaxation time for enhancing ions dynamic behaviour. The conduction mechanism of the higher conducting polymer electrolyte is explained by small polaron hopping and overlapping large polaron tunnelling conduction mechanism. From the argand plot, it is confirmed that higher conducting sample has low relaxation time.

Experimental and theoretical studies of Mn(II) and Co(II) metal complexes of a tridentate Schiff's base ligand and their biological activities

We have used the condensation method to synthesize 2‐acetyl‐5‐methylsemicarbazone ligand. Manganese(II) and Cobalt(II) complexes having formula [ML2]X2 were synthesized where M = Mn(II) and Co(II), L = ligand, X = Cl−, CH3COO−, NO3−, ½SO42−. The characterization data suggests the octahedral geometry for all the synthesized complexes. Tridentate nature of the 2‐acetyl‐5‐methylsemicarbazone ligand was revealed by IR studies. Molar conductance analysis suggested the electrolytic nature of the complexes. The theoretical study includes geometrical optimization, HOMO‐LUMO energy gap, energetic parameters and dipole moment. These results also confirmed the tridentate nature of the ligand and the octahedral geometry of complexes. The molecular electrostatic potential (MEP) study suggested the reactive sites for an electrophilic or nucleophilic attack in the ligand. We tested the synthesized compounds for their antifungal and antibacterial action via well diffusion method and found that parent ligand after the coordination with the metal ion showed more effective inhibition against bacteria and fungi.

Study of the piezoionic effect and influence of electrolyte in conducting polymer based soft strain sensors

Electronic conducting polymers (ECP) have been widely studied in a tri-layer configuration as soft, bending actuators. These electroactive materials have also been reported to behave as mechanical strain sensors able to convert mechanical stimulation into electrical signals. This sensing behavior is attributed to the so-called piezoionic effect and is observed and reported in most ionic electroactive polymers (EAPs). However, ambiguities remain on the origin of this effect, being attributed either to stress gradient induced ion motion or to Donnan potentials arising at the ECP/electrolyte interface. In this work, the sensor mechanism of trilayer ECP actuators is studied and discussed as a function of different physical and chemical parameters thanks to the versatile synthesis of conducting interpenetrating polymer networks. Results demonstrate that the main mechanism relies on stress gradient, as in other ionic EAPs, instead of Donnan potential. Moreover, a deep investigation of the electrolyte nature and its concentration is performed. Mobile ions deduced from actuation experiments are correlated with the sign of voltage output during sensing experiments. An interesting inversion point is demonstrated at a concentration of 2.5 M of 1-ethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide in propylene carbonate where simultaneous charge compensation (no sensing) and volume compensation (no actuation) occur for mobile cations and anions, while electrochemical behavior remains unchanged.

MgFe2O4 nanoparticles synthesis and characterization: application to trace level mercury(II) measurement from waste water samples

The magnesium ferrite nanoparticles modified glassy carbon electrode has been fabricated and applied in the trace level quantification of Hg2+ by differential pulse stripping voltammetry technique. The MgFe2O4 particles were prepared by a simple nitrate-sucrose solution combustion synthetic route and characterized through XRD, FTIR, SEM, TEM, BET and XPS techniques. The MgFe2O4 modified glassy carbon electrode has been characterized voltammetrically using standard redox couple i.e. [Fe(CN)6]4/3− along with electrochemical impedance spectroscopy (EIS). The experimental parameters such as nature of electrolyte, deposition potential and deposition time were optimized. The fabricated sensor showed excellent signal intensity and stability towards Hg2+ measurement at trace level. The sensor showed linearity in the concentration range 2–120 ppb with very low detection limit of 0.037 ppb.

Improving Electrochemical Stability and Low‐Temperature Performance with Water/Acetonitrile Hybrid Electrolytes

AbstractAlthough the “water‐in‐salt” electrolyte has significantly expanded the electrochemical stability window of aqueous electrolytes from 1.23 to 3 V, its inevitable hydrogen evolution under 1.9 V versus Li+/Li prevents the practical use of many energy‐dense anodes. Meanwhile, its liquidus temperature at 17 °C restricts its application below ambient temperatures. An advanced hybrid electrolyte is proposed in this work by introducing acetonitrile (AN) as co‐solvent, which minimizes the presence of interfacial water at the negatively charged electrode surface, and generates a thin and uniform interphase consisting of an organic outer layer based on nitrile (CN) and sulfamide (R‐S‐N‐S) species and an inner layer rich in LiF. Such an interphase significantly suppresses water reduction and expands the electrochemical stability window to an unprecedented width of 4.5 V. Thanks to the low freezing point (−48 °C) and low viscosity of AN, the hybrid electrolyte is highly conductive in a wide temperature range, and enables a LiMn2O4/Li4Ti5O12 full cell at both ambient and sub‐ambient temperatures with excellent cycling stability and rate capability. Meanwhile, such a hybrid electrolyte also inherits the nonflammable nature of aqueous electrolyte. The well‐balanced merits of the developed electrolyte make it suitable for high energy density aqueous batteries.

Homogeneous electron-transfer of chlorophyll and its derivative chlorophyllin at gold electrode

Introduction: Chlorophyll is a light harvesting pigment, which absorbs light in the visible spectrum of sunlight and promotes electron transfer, Chlorophyllin (CHL) is One of the most important derivative molecules of chlorophyll. Nowadays, chlorophyll pigment and its derivatives are utilised in organic photosynthetic solar cells for their desirable photovoltaic properties. Cyclic voltammetry (CV) is an essential technique. It is extensively used to study electroactive species to interpret the intermediates of reactions, supply information about the thermodynamics of oxidation-reduction reactions and elucidate the kinetics of electron transfer reactions. Materials and Methods: Prior to the electrochemical study, the working gold (Au) electrode surface was prepared by immersing it in the various concentrations of chlorophyllin for a period time. The electrolyte was degassed by using N2 for approximately 30 minutes inside a Faraday cage before any electrochemical experiment was performed. A three electrode system was used with, Ag/AgCl as a reference electrode, graphiteas a counter and the working electrode (Au). Results and Discussion: As a route to develop new chemical systems for artificial photosynthesis, this work reports the effectiveness of different parameters in transferring electrons between chlorophyllin (CHL) pigment and the working electrode surface (gold). These parameters such as the adsorption time, the electrolyte nature and concentration and chlorophyllin concentration are investigated. The use of chlorophyllin as a redox mediator is examined, with a gold electrode being employed. The importance of gold electrode surface preparation in determining the mechanism of redox is described, and the environment of adsorption process of the different concentrations of chlorophyllin on the surface of the gold electrode has been elucidated in this study. Conclusiones: The electrochemical method showed that the cyclic voltammetry responses of studied adsorption chlorophyllin pigment on the gold electrode were more efficient. In addition, the redox reaction was successful electrochemically in aqueous solution thanthe organic solution. It was suggested that electrons reduce to the chlorophyllin pigment by adding active species in the bulk solution homogeneous transfer. Finally, detections of chl on spinach leaves using various methods are reported.

In‐vitro DNA binding and antimicrobial studies of trivalent transition metal ion based macrocyclic complexes

AbstractIn the current research work diaminotoluene based tetra‐azamacrocyclic‐14 membered [N4] macrocylic complexes of nitrate, chloride and acetate trivalent transition metals salts of Cr(III) and Fe(III) have been synthesized by taking the route of template methodology. The synthesized complexes were fully characterized by spectroscopic and physico‐analytical techniques like IR, ESI‐MS, ESR, Powder XRD, TGA, UV‐visible, magnetic moment, molar conductance, in addition to the elemental analysis measurements. The monomeric and electrolytic nature of the complexes is elucidated by the help of ESI‐MS and molar conductance values that reveals about the 1:2 electrolytic behaviour. On the basis of above analytical techniques the complexes may be empirically formulated as [MLX]X2 in which L is macrocyclic ligand obtained from the [2+2] condensation reaction of 3,4‐diaminotoluene (DAT) and dibenzoylmethane (DBM). The thermal data provides an indication towards the absence of water molecular and various decomposition steps in the complexes. Further the compounds were screened for their antimicrobial potency against few strains of bacteria and fungus and fair results were found from the above studies. In addition to these DNA binding activity was also performed in order to elucidate the mode of binding the newly synthesised complexes.

Highly Selective Toward Four- or Two-Electrons ORR on Nitrogen Doped Carbon Nano Structures in Fuel Cells for Space Applications

Human space travel requires several technological developments that support fuel generation and the energy-efficient preservation of closed systems in microgravity spaceship environments [1]. Fuel cells are promising candidates for clean energy conversion for terrestrial and space applications. The overpotential required for the Oxygen Reduction Reaction (ORR) and the degradation of the electrocatalysts are the main factors that diminish practical application of fuel cells [2]. ORR in aqueous solutions occurs mainly by two pathways: the direct four-electron reduction pathway from O2 to H2O, and the two-electron reduction pathway from O2 to hydrogen peroxide (H2O2). In fuel cell processes, the four-electron direct pathway is highly preferred. The two-electron reduction pathway is used in industry for H2O2 production [3]. Carbon nanostructures have been previously used as catalyst due to high stability and surface area, high electrical conductivity for providing electrical pathways, and mesoporous structure for the facile diffusion of reactants and by-products. Studies have revealed that carbon nanostructures and nitrogen doped carbon structures show catalytic activity in ORR [5,6]. A metal-free mesoporous nitrogen-doped carbon catalyst showed a high electrocatalytic activity, durability and selectivity toward peroxide by electrochemical converting of O2 in a non-corrosive neutral as well as in acidic reaction medium [7,8]. Accordingly, in order to evaluate the ORR electron transfer pathway on highly stable nitrogen doped carbon nanostructures, we developed an alternative post-synthesis nitrogen doping of Vulcan and CNOs. The doping process was developed by thermal treatment in atmospheric pressure, using dicyandiamide (DCDA) as nitrogen precursor. The operational parameter conditions of the thermal reactor were a reaction temperature 700 °C, 2 mL/min of total argon gas flow, and a composition of precursors 2:1 DCDA:Vulcan and DCDA:CNOs. Our research involves increase surface area of carbon pristine source and improve its electronic structure and understanding of the nitrogen intercalation process by possible pyrolytic–nucleophilic mechanism of N-C doping reaction. The structural properties of the NVulcan and NCNOs were investigated using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. NVulcan and NCNOs electrochemical characterization revealed higher performance than Vulcan and CNOs, respectively, due to N doping. Nitrogen doping in the Vulcan and CNOs enhances the electronic conductivity and specific capacitance. An analysis of the rotating disk electrode (RDE) technique data was done to evaluate the ORR kinetics, including n-values which are related to the mechanism of oxidation, at the NVulcan and NCNOs, using the Koutechy-Levich (K-L) equation. The pH Effect on Oxygen Reduction Reaction over N-doped carbon nanostructures in O2 saturated 0.2 M Na22SO4 was evaluated by a scan rate of 10 mV/s at different rotation rates: 300, 700 1100, 1500, and 1900 rpm. Our results could be evidence that the two-electrons and four-electrons transfer pathway selectivity, depend on the supporting electrolyte, i.e., pH value and nature of electrolyte, and increases to 0.2M Na2SO4 according to neutral (2.5 electrons) > acidic (1.4 electrons) > alkaline (3.4 electrons). Initial fuel cell tests, utilizing oxygen and RO water, showed that NVulcan and NCNOs can generate 0.30 and 0.08 w/w% peroxide concentration, respectively. The system output current was 0.20 amps for NVulcan and 0.30 amps for NCNOs. These results suggested that NVulcan performs an extremely high selectivity toward a two-electron pathway reduction process, whereas NCNOs catalyzes a four-electron route. Therefore, our approach would be promising to control of four- or two-electrons route kinetics of ORR in fuel cells for space technologies, by the supporting electrolyte, nanocarbon source and nitrogen doped nanocarbon configurations. NASA Strategic Plan. National Aeronautics and Space Administration, 2018, at: https://www.nasa.gov/sites/default/files/atoms/files/nasa_2018_strategic_plan.pdf.K. Nørskov, J. Rossmeisl, A. Logadottir and L. Lindqvist. Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. J. Phys. Chem. B, 108 (46), 17886–17892, 2004.Song, C,; Zhang, J.; Electrocatalytic oxygen reduction reaction in PEM fuel cell electrocatalysts and catalyst layers. Springer; 2008, 89-134.Hennrich, C. Chan, V. Moore, M. Rolandi, and M. O’Connell, “The element carbon,” in Carbon Nanotubes Properties and Applications, M. J. O’Connell, Ed., Taylor & Francis, Boca Raton, Fla, USA, 2006.Xing W, Qiao SZ, Ding RG, Li F, Lu GQ, Yan ZF. Superior electric double layer capacitors using ordered mesoporous carbons. Carbon, 44(2):216–24, 2006.Frédéric Haschéa, Mehtap Oezaslan, Peter Strasser, Tim-Patrick Fellinger. Electrocatalytic hydrogen peroxide formation on mesoporousnon-metal nitrogen-doped carbon catalyst. Journal of Energy Chemistry 25, 251-257, 2016.Ramaswamy , U. Tylus , Q. Jia , S. Mukerjee , J. Activity Descriptor Identification for Oxygen Reduction on Non-Precious Electrocatalysts: Linking Surface Science to Coordination Chemistry. J. Am. Chem. Soc. 135, 15443-15449, 2013.

(Invited) Garnet-Based Advanced Solid-State Batteries

I will start by giving an overview of active research activities in my research group located at University of Maryland Energy Research Center, including wood materials toward sustainability, 3000K high temperature materials and processing (Science2018), wood nanotechnologies ( Nature 2018), beyond-Li ion batteries (solid state, Na-ion). Then I will focus on our recent development on garnet -based solid-state Li-metal batteries including interface engineering to improve the wetting between Li metal anode and Garnet solid-state electrolyte (Nature Materials 2016; Science Advances 2017); Garnet based 3D Li ion conductive framework (bilayer, trilayer) toward high energy density Li-S batteries (EES 2017); Garnet nanofiber based flexible, hybrid electrolyte with a high Li ion conductivity (PNAS 2016), and In-situ neutron depth profiling technique in understanding Li-garnet and CNT-garnet interfaces (JACS 2016).

Synthesis, Spectroscopic Studies, and Biological Activity of Some New N2O2 Tetradentate Schiff Base Metal Complexes

The new tetradentate Schiff base N,N′-ethylene bis[1-ethyl-6-fluoro-4-imine-7-(piperazine-1-yl)-quinoline-3-carboxylic acid] (Nor-en) has been synthesized. Its chelated complexes with Co(II), Ni(II), Cu(II), Zn(II), Y(III), Zr(IV), La(III), and U(VI) are characterized using molar conductivity, magnetic moment, FT-IR, UV-Vis, 1H NMR, and mass spectra, and thermal analysis. It is determined that the complexes have monomeric structures and exist in the octahedral configuration. The molar conductance values indicate the electrolytic nature of the complexes. According to the spectroscopic data, the complexes share the same coordination environment around the metal ions, consisting of N2O2 and one or two water molecules. The thermodynamic parameters (activation energy, E*, entropy, ΔS*, enthalpy, ΔH*, and Gibbs free energy, ΔG*) are calculated using Coats-Redfern and Horowitz-Metzger methods. The carried out tests indicate the compounds’ high antibacterial activity against Staphylococcus aureus, Bacillus cereus, and Salmonella typhi. Anticancer activity of the ligand and its metal complexes is evaluated against HepG-2 cells (human Hepatocellular carcinoma) and determined to be very low.

Multiscale Roughness Characterization of Electropolished 316L ALM Steel By Power Spectral Density Post-Treatment

Electrolytic polishing (EP) is a well-known technology which may replace mechanical polishing in finishing treatment of complex geometry substrates produced by additive manufacturing (AM). This consists in an anodic dissolution process, allowing a mirror finish to be obtained by uniform roughness reduction on metallic parts immediately after the machining step. This is achieved by controlling electrolyte nature and operating parameters such as dissolution potentials, process duration and temperature [1]. Nevertheless, in the specific case of additive manufacturing, where high level of roughness can be observed, it is important to discriminate the microscopic and macroscopic scales of etching. The roughness value can be measured at different scales by several technics (mechanical sensor, optical profiler, AFM…), but the results (Ra, Sa…) are dependent on the spatial resolution of the device and on the measurement procedure like cut-off application. A way to overcome this problem consists in making these parameters independent of the roughness scale by integrating the fractal dimension of topographic records [2]. In this study, 316L stainless steel samples obtained by additive manufacturing were electropolished and compared to raw and mechanically polished samples. The characterization of the surface roughness was carried out by optical profilometry, and the 2-D data were analyzed to plot Power Spectral Density as a function of spatial frequency (PSD) [3]. Then, the curves obtained are fitted by the Weierstrass-Mandelbrot function to determinate the fractal dimension, which allows quantification of the surface irregularity level [4]. Acknowledgments : the authors would like to thank the IRT-M2P program AFTER ALM for its financial support. [1] C. Rotty, A. Mandroyan, M.-L. Doche, and J. Y. Hihn, Surf. Coat. Technol., 307 Part A, 125–135 (2016) [2] Majumdar, A., Tien, C.L.: Fractal characterization and simulation of rough surfaces. Wear 136(2), 313–327 (1990) [3] Prashant Pendyala, M. S. Bobji, Giridhar Madras. Evolution of Surface Roughness During Electropolishing, (2014). Springer Science Editions [4] S. Panda, A. Panzade, M. Sarangi, S.K.R. Chowdhury, Journal of Tribology, 139 031402-1/9 (2017) Figure 1

Effect of the Nature of Background Electrolyte on the Thermodynamic Characteristics of the Acid–Base Reactions of L-Asparagine in Aqueous Solutions

The enthalpies of interaction between L-asparagine with HNO3 and НCl in aqueous solutions with different pH values at a temperature of 298.15 K and ionic strengths of 0.5–1.5 are measured calorimetrically using different background electrolytes. The enthalpies of the stepwise dissociation of L-asparagine are determined. The effect the nature of the background electrolyte has on the thermodynamic characteristics of L‑asparagine dissociation is examined.

Effect of electrolyte nature in mass transport of a neutral solute in a microtube with porous wall

AbstractElectroosmotic flow in a microchannel is an active area in microfluidics. Microchannels with porous wall are advantageous due to selective separation and enhanced mass transport. An economic and innovative method to fabricate hollow microtubes and their application in electrokinetics are illustrated. Effects of asymmetric electrolyte on mass transport of a neutral macrosolute in the microtube with porous wall are investigated. The combined velocity profile including both pressure‐driven and electroosmotic flow is modeled for different electrolytes. It is found from the study that the addition of higher valency asymmetric electrolyte (3:1) increases transport of neutral solutes across the porous wall compared to its symmetric counterpart (1:1). The developed model was validated with the experimental results, using a cartridge having hollow microtubes with porous wall. This study would be helpful to select an appropriate electrolyte, improving the design, and performance prediction of microfluidic devices.

Preparation and physicochemical study of jute and glass composites of epoxy resin of (2E, 6E)-bis(4-hydroxybenzylidene)cyclohexanone

Jute and glass composites of epoxy resin of (2E, 6E)-bis(4-hydroxybenzylidene)cyclohexanone (EBHBC) were prepared by compressing molding technique using three different hardeners at 150/120 °C for 3 h under 20 MPa pressure. J-EBHBC-DDM, J-EBHBC-DDS, J-EBHBC-THPA, G-EBHBC-DDS and G-EBHBC-THPA possess 9.8, 19.0, 15.8, 42.9 and 46.7 MPa tensile strength; 93.6, 24.9, 95.0, 97.9 and 184.2 MPa flexural strength; 5.6, 2.9, 3.0, 20.2 and 7.7 kV/mm electric strength; and 4.24 × 109, 2.91 × 1010, 1.35 × 109, 2.78 × 1011 and 2.23 × 1011 Ω cm volume resistivity. The nature and structure of the hardeners have affected mechanical and electrical properties of the jute and glass composites. Water absorption behavior of composites is tested in pure water and 10% each of aqueous HCl, H2SO4, HNO3, NaOH, KOH, NaCl solutions at 35 °C as well as in boiling water. Nature of electrolytes has affected water absorption and diffusivity of solvated water in the composites. Both types of the composites showed excellent hydrolytic stability, high water absorption tendency and longer equilibrium time. Water absorption behavior in the composites was found quite different in different environments indicating different diffusivity in different environments. The composites may be useful for low load bearing housing, electrical and marine applications.

Faradaic and/or capacitive: Which contribution for electrochromism in NiO thin films cycled in various electrolytes?

This study compares the electrochromic performance of NiO thin films deposited by RF magnetron sputtering cycled in lithium, sodium and small cations free based electrolytes, namely 1:9 LiTFSI in EMITFSI, 1:9 NaTFSI in EMITFSI and EMITFSI respectively. Regardless of the electrolyte nature, NiO thin films show similar electrochromic properties associated with an optical switch from colorless to brownish upon oxidation correlated to a modulation of transmittance close to 40 % associated with a good electrochemical stability. Interestingly, depending on the electrolyte nature, the EC behavior is correlated with various CV shapes raising the question of the mechanism involved. In particular, the reversible coloration mechanism cannot be only described by a single insertion/extraction of lithium ions, as observed for tungsten oxide in lithium media. The rectangular shape of the CV curves of NiO thin films in neat electrolyte and the behavior of NiO with various scan rates suggest that the EC properties result from a combination of both faradaic and capacitive contributions, with redox reactions largely occurring at the surface. Integration of NiO thin films in a full device is illustrated in double sided PANI/white electrolyte-EMITFSI/NiO EC devices showing simultaneous progressive color changes from blue to green and white to brown, on PANI and NiO sides, respectively.

Electrochemical reduction mechanism of NbF5 and NbCl5 in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate

The electrochemical reduction mechanism of niobium was studied in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([BMP][OTf]) containing niobium halides (NbCl5 and NbF5). The influence of the electrolyte composition, temperature, and nature of the substrate were systematically investigated. In situ electrochemical techniques, such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical quartz crystal microbalance (EQCM) and rotating ring disc electrode (RRDE), were used, besides the ex situ characterization techniques scanning electron microscopy (SEM) and vibrational spectroscopy. The number of transferred electrons was estimated from the half width of the cathodic peaks in the DPV measurements. Furthermore, the product of the diffusion coefficient and the number of transferred electrons at the power of 3/2 were evaluated from RRDE measurements to be approx. 3 × 10−10 m2/s. Thicker and better adherent niobium-based deposits were obtained from NbCl5 in [BMP][OTf] than from NbF5 in [BMP][OTf]. EQCM measurements combined with DPV indicated the potential region where niobium-based deposits could be obtained as well as their stoichiometry.Vibrational spectroscopy reveals that NbF5 and NbCl5 interact differently with [BMP][OTf]. The spectra show that in the case of NbF5 – [BMP][OTf] only niobium(V) anionic species [NbF6A]2- and [NbF5A]- (where A = [OTf]-) are formed, while in NbCl5 – [BMP][OTf] both niobium(V) and niobium(IV) anionic species are present. At low NbCl5 concentrations, [NbCl4A2]2- and [NbCl4A2]- are obtained, while at high NbCl5 concentration, [NbCl5A]2- and [NbCl5A]- are found. The electrochemical niobium reduction mechanism depends on temperature and on the anionic species that are involved in the reduction process. In the case of NbCl5 – [BMP][OTf], at high cathodic potentials the formation of subvalent Nb-clusters (possibly Nb6Cl14) was observed.

Structural, spectroscopic, molecular docking, thermal and DFT studies on metal complexes of bidentate orthoquinone ligand

4‐Triphenylmethyl‐1,2‐benzoquinone (TPMBQ) reacted with some metal ions and the structure of the new compounds had been identified. The metal to ligand ratio was 1:2 which was revealed by elemental analysis. The complexes were found to have octahedral geometry and their thermal stability was studied using thermogravimetric analysis technique. The molar conductance measurements revealed the electrolytic nature of the synthesized chelates. The IR spectra concluded the bidentate nature of the TPMBQ ligand while the 1H NMR revealed the presence of water molecules. The XRD spectra of Mn (II) and Fe (III) complexes concluded their crystalline structure while Co (II) and Cu (II) chelates refer to amorphous structures. The geometries of the TPMBQ ligand were optimized using Gaussian 09 W; density functional theory B3LYP method. (DFT)/basis set 6–311++G (d, p). HOMO and LUMO energy values for chelates, chemical hardness and electro‐negativity had been calculated. The ligand and its metal complexes had been examined against different kinds of bacteria such as Proteus vulgaris, Escherichia coli, Staphylococcus aurous and Bacillus subtitles to examine their antimicrobial activity. Molecular docking using Auto Dock tools were utilized.

Carbon Nanofibers Provide a Cationic Rectifier Material: Specific Electrolyte Effects, Bipolar Reactivity, and Prospect for Desalination

AbstractWe demonstrate that ionic current rectification effects are observed with a film of negatively charged carbon nanofibers (CNFs) deposited as a film or mat onto a 10 μm diameter microhole in poly‐ethylene‐terephthalate (PET). CNFs are synthesized by using a chemical vapor deposition (CVD) method, followed by oxidation with hydrogen peroxide to introduce carboxyl moieties (providing negative surface charges). CNFs are characterized with transmission electron microscopy, scanning electron microscopy, elemental analysis, and zeta potential measurements. When drop‐dried asymmetrically onto a 10 μm diameter cylindrical channel on a 6 μm thick PET substrate and placed as a membrane between two electrolyte compartments, ionic current rectification is observed. Effects of pH, ionic strength, and nature of electrolyte are investigated. Bipolar reactivity of iodide is demonstrated. Potential for future applications in water purification are discussed.