Fabrication and study of supercapacitor electrodes based on oxygen plasma functionalized carbon nanotube fibers

Dry-spun Carbon Nanotube(CNT) fibers were surface-modified by atmospheric pressure oxygen plasma functionalization using a well controlled and continuous process. The fibers were characterized by scanning electron microscopy(SEM), Raman spectroscopy, and X-ray Photoelectron Spectroscopy(XPS). It was found from the conducted electrochemical measurements that the functionalized fibers showed a 132.8%increase in specific capacitance compared to non-functionalized fibers. Dye-adsorption test and the obtained Randles-Sevcik plot demonstrated that the oxygen plasma functionalized fibers exhibited increased surface area. It was further established by Brunauer-Emmett-Teller(BET) measurements that the surface area of the CNT fibers was increased from 168.22 m~2/g to 208.01 m~2/g after plasma functionalization. The pore size distribution of the fibers was also altered by this processing. The improved electrochemical data was attributed to enhanced wettability, increased surface area, and the presence of oxygen functional groups, which promoted the capacitance of the fibers. Fiber supercapacitors were fabricated from the oxygen plasma functionalized CNT fiber electrodes using different electrolyte systems. The devices with functionalized electrodes exhibited excellent cyclic stability(93.2% after 4000 cycles), flexibility, bendability, and good energy densities. At 0.5 m A/cm~2, the EMIMBF4 device revealed a specific capacitance, which is 27% and 65% greater than the specific capacitances of devices using EMIMTFSI and H_2 SO_4 electrolytes,respectively. The practiced in this work plasma surface processing can be employed in other applications where fibers, yarns, ribbons, and sheets need to be chemically modified.     

Electrophoretic studies on the mixed nitrilotriacetate-penicillamine complexes of Pb2+ and UO 2 2+

A technique involving the use of paper electrophoresis is described for the study of binary and mixed-complex systems in solution. This technique is based on the movement of a spot of metal ion in an electric field with the complexants added in the background electrolyte at pH 8.5. The concentration of primary ligand (nitrilotriacetate) was kept constant, while that secondary ligand (penicillamine) was varied. A graph of log[penicillamine] versus mobility was used to obtain information on the mixed complexes and to calculate stability constants. The stability constants of mixed-ligand complexes lead(II)-nitrilotriacetate-penicillamine and uranyl(II)-nitrilotriacetate-penicillamine have been found to be 5.68 ± 0.09 and 6.56 ± 0.05 (logarithm stability constant values), respectively, at ionic strength 0.1 M and a temperature of 35°C. The text was submitted by the author in English.     

In situ synthesis and characterization of multiwalled carbon nanotube/Au nanoparticle composite materials

An effective and facile in situ reduction approach for the fabrication of carbon nanotube-supported Au nanoparticle (CNT/Au NP) composite nanomaterials is demonstrated in this article. Linear polyethyleneimine (PEI) is ingeniously used as both a functionalizing agent for the multiwalled carbon nanotubes (MWNTs) and a reducing agent for the formation of Au NPs. This method involves a simple mixing process followed by a mild heating process. This approach does not need the exhaustive surface oxidation process of CNTs. The coverage of Au NPs on CNTs is tunable by varying the experimental parameters, such as the initial molar ratio of PEI to HAuCl4, the relative concentration of PEI and HAuCl4 to MWNTs, and the temperature and duration of the heat treatment. More importantly, even the heterogeneous CNT/Au composite nanowires are obtainable through this method. TEM, XPS, and XRD are all used to characterize the CNT/Au composite materials. In addition, the optical and electrocatalytic properties are investigated.     

Temperature stable supercapacitors based on ionic liquid and mixed functionalized carbon nanomaterials

The ionic liquid 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (BDMIM-TFSI) showed a conductivity of 1.65?mS cm^?1 and an electrochemical stability window of 4.4?V at room temperature. Two types of electrodes based on carbon nanomaterials were prepared: (1) with alternating layers of two oppositely charged functionalized double-walled carbon nanotubes (DWCNTs) and (2) with the functionalized DWCNTs and graphene oxide nanoplatelets. The electrodes presented a porous morphology and a connected pathway between the carbon nanotubes and graphene oxide platelets. Electrochemical capacitors based on the carbon nanomaterials and BDMIM-TFSI were produced in a stacking configuration and were characterized at 25?°C, 60?°C, and 100?°C. The supercapacitors with electrodes based on the three alternating layers of two oppositely charged DWCNTs and graphene oxide presented higher values of capacitance, which were attributed to a morphology favorable to providing ionic access to the carbonaceous surface. Box-like voltammetric curves were used to calculate the capacitance in a 4-V potential window at 100?°C.     

Pyridine-2-carboxaldehyde as ligand: synthesis and derivatization of carbonyl complexes

Thermally induced carbonyl substitutions on [M(CO)5X] (M=Mn, X=Cl, Br; M=Re, X=Br) or room temperature displacement of acetonitrile from [Mo(eta3-methallyl)Cl(CO)2(NCMe)2] produce stable crystalline complexes containing pyridine-2-carboxaldehyde (pyca) as chelate kappa2(N,O) ligands (). These react with ethylglycine to afford iminopyridine complexes containing an amino ester pendant arm in high-yield. Treatment with silver salts produce halide abstraction affording neutral complexes containing coordinated perchlorate or triflate which can be replaced by triphenyl phosphine to give cationic complexes . As confirmed by spectroscopy and X-ray crystallography the pyca ligand remains bonded as chelate kappa2(N,O) throughout these processes.     

In situ synthesis,crystal structures,and luminescence of two new tetrazole complexes

The synthesis, crystal structures, and luminescent properties of two new complexes containing tetrazolyl ligands are described. Refluxing a mixture of fipronil (fipronil = (±)-5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-carbonitrile), sodium azide, and CuCl₂ in ethanol and water gives complex 1, [M(L)₂](H₂O)₂] ? 2H₂O (HL = (±)-5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-tetrazole, M = Cu). Hydrothermal reaction of fipronil, sodium azide, and Cd(ClO₄)₂ in the presence of water and ethanol (Demko–Sharpless tetrazole synthesis) yields 2, [M(L)₂](H₂O)₂] ? 2H₂O (M = Cd). The metals in both complexes are six coordinate from two water molecules, two nitrogens from different tetrazolyl groups, and two nitrogens from pyrazolyl groups. Photoluminescence studies reveal that 2 exhibits strong blue fluorescent emission at λ _max = 451 nm in solid state at room temperature.     

2:2 Fe(III):ligand and "adamantane core" 4:2 Fe(III):ligand (hydr)oxo complexes of an acyclic ditopic ligand

A bis-hydroxo-bridged diiron(III) complex and a bis-mu-oxo-bis-mu-hydroxo-bridged tetrairon(III) complex are isolated from the reaction of 2,6-bis((N,N'-bis-(2-picolyl)amino)methyl)-4-tert-butylphenol (Hbpbp) with iron perchlorate in acidic and neutral solutions respectively. The X-ray structure of the dinuclear complex [{(Hbpbp)Fe([mu-OH)}(2)](ClO(4))(4).2C(3)H(6)O (1.2C3H6O) shows that only one of the metal-binding cavities of each ligand is occupied by an iron(III) atom and two [Fe(Hbpbp)]3+ units are linked together by two hydroxo bridging groups to form a [Fe(III)-(mu-OH)](2) rhomb structure with Fe...Fe = 3.109(1)A. The non-coordinated tertiary amine of Hbpbp is protonated. Magnetic susceptibility measurements show a well-behaved weak antiferromagnetic coupling between the two Fe(III) atoms, J= -8 cm(-1). The tetranuclear complex [(bpbp)(2)Fe(4)(mu-O)(2)(mu-OH)(2)](ClO(4))(4)(2) was isolated as two different solvates .4CH(3)OH and .6H(2)O with markedly different crystal morphologies at pH ca. 6. Complex .4CH(3)OH forms red cubic crystals and .6H(2)O forms green crystalline platelets. The Fe(4)O(6) core of shows an adamantane-like structure: The six bridging oxygen atoms are provided by the two phenolato groups of the two bpbp(-) ligands, two bridging oxo groups and two bridging hydroxo groups. The hydroxo and oxo ligands could be distinguished on the basis of Fe-O bond lengths of the two different octahedral iron sites: Fe-mu-OH, 1.953(5), 2.013(5)A and Fe-mu-O, 1.803(5), 1.802(5)A. The difference in ligand environment is too small for allowing Mossbauer spectroscopy to distinguish between the two crystallographically independent Fe sites. The best fit to the magnetic susceptibility of .4CH(3)OH was achieved by using three coupling constants J(Fe-OPh-Fe)= 2.6 cm(-1), J(Fe-OH-Fe)=-0.9 cm(-1), J(Fe-O-Fe)=-101 cm(-1) and iron(III) single ion ZFS (|D|= 0.15 cm(-1)).     

Synthesis of mixed chloroformate and sulfatoformate complexes of Mo 2 4+

Conclusions Methods are developed for synthesizing previously unknown mixed chloroformate and sulfate-formate binucleate complexes of Mo(II) in which the presence of a metal-metal bond is confirmed by the presence of Mo-Mo lines in the Raman spectrum.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 496–498, March, 1981.     

Novel metal complexes containing a chiral trinitrogen isoindoline-based pincer ligand: in situ synthesis and structural characterization

The first synthesis and characterization of metal coordinated complexes containing in situ prepared chiral trinitrogen 1,3-bis(4,5-dihydrooxazol-2-ylimino)isoindoline-based pincer ligands are reported. Two zinc complexes, isolated as Zn(L)(2), where L = 1,3-bis(4,5-dihydro-4-(R)-phenyloxazol-2-ylimino)isoindoline ((R,R)-5) or 1,3-bis(4,5-dihydro-4-(S)-iso-propyloxazol-2-ylimino)isoindoline ((S,S)-6), respectively, are reported. Complexes Zn((R,R)-5)(2) and Zn((S,S)-6)(2) were prepared in situ through the condensation of phthalonitrile with enantiopure 2-amino-4-(R)-phenyloxazoline ((R)-3) or 2-amino-4-(S)-iso-propyloxazoline ((S)-4) in the presence of ZnCl(2) at 80 °C in dry toluene over 3-4 days. The characterizations of Zn((R,R)-5)(2) and Zn((S,S)-6)(2) in both the solid (X-ray crystallography) and solution (multinuclear NMR spectroscopy) states are reported.     

Formation of stable iron/cobalt NHC complexes via unexpected ring opening and in situ generation of a tridentate ligand

The reactions of FeCl(2) and CoCl(2) with a bistriazolium salt yields the NHC complexes [Fe(III)()(2)]I·H(2)O, [Fe(III)()(2)]PF(6)·CH(3)CN and [Co(III)()(2)]I·0.5CH(3)CN, through an unusual ring opening of one of the triazoyl rings, which leads to the formation of C,N,O tridentate ligands or . Furthermore, a Fe(ii) species [Fe(II)()(2)]·CH(2)Cl(2) was also obtained.     

Pyrolysis gaschromatography of the mixed ligand complexes of molybdenum- and tungsten-dinitrosyls

The pyrolytic behavior of the cis-dinitrosyl complexes with the general formulas [M(NO)₂Cl₂L₂], [M(NO)₂Cl₂L′], and [M(NO)₂L₂′] where M is Mo or W, L is monodentate and L′ bidentate ligands were investigated by means of the TG, DSC, and pyrolysis gaschromatography (PGC) analyses. Upon pyrolysis, these dinitrosyls have been found to yield a gaseous product composed of N₂, N₂P and NO; the mixed ligands L and L′ which are good π-electron acceptor and readily oxidized, favor the occurrence of the redox reaction of the nitrosyl ligands. The formation of N₂ and N₂O are discussed by taking into account a thermally induced, intramolecular interaction between the nitrosyl and the adjacent ligand L or L′ initiating the redox reaction.     

Ruthenium(II) [3 + 2 + 1] mixed ligand complexes: substituent effect on photolability, photooxidation of bases, photocytotoxicity and photonuclease activity

Mixed ligand complexes of ruthenium(II), [Ru(itpy)(bpy)Cl]ClO(4)1, [Ru(itpy)(phen)Cl]ClO(4)2, [Ru(bitpy)(bpy)Cl]ClO(4)3 and [Ru(bitpy)(phen)Cl]ClO(4)4 have been synthesized and characterized. Complex 3 has also been characterized crystallographically. These complexes exhibit photolability of the Ru-Cl bond. Upon irradiation at 440 nm in the presence of nucleosides and nucleotides the complexes exchange chloride for the nucleoside or nucleotide. The photolability of the Ru-Cl bond depends on the nature of the substituent in the tridentate tpy ligand. Photolysis of the complexes in the presence of a nucleoside or nucleotide also produces 8-oxoguanine due to the oxidation of guanine by the excited states of the complexes. These four complexes exhibit photonuclease properties and bring about the cleavage of plasmid DNA when irradiated at 440 nm. These complexes have been found to be toxic towards NIH 3T3 cells under photolytic conditions.     

Bond strengths and reproportionation constants of mixed ligand complexes of lanthanones

111 mixed ligand complexes of lanthanones with nitrilotriacetic acid (NTA) and 2-hydroxy-2,4,6-cycloheptatrien-1-one (tropolone:TR) have been studied potentiometrically in 50% (v/v) aq. dioxane medium at 0.1M-NaClO₄ at 30±1°C. For these systems, complexation of primary ligand (NTA) with lanthanones is complete before complexation withTR takes place. The formation constants have been calculated by a weighted least squares method. The results show thatNTA andTR are incompatible ligands towards lanthanones and hence the mixed ligand complexes formed have lower stability than either of the parent complexes.

---

Komplexbildungskonstanten von Lanthaniden mit gemischten Liganden

Zusammenfassung Es wurden 111-Komplexe von Lanthaniden [Ln(III)] mit Nitrilotriessigsäure (NTA) und 2-Hydroxy-2,4,6-cycloheptatrien-1-on (Tropolon;TR) als gemischte Liganden potentiometrisch in 50% (v/v) wäßr. Dioxan bei 0,1M-NaClO₄ und 30±1°C untersucht. Die Komplexbildungskonstanten wurden mittels einer gewichteten Fehlerquadrat-Methode berechnet. Es zeigte sich, daßNTA undTR inkompatible Liganden gegenüberLn(III) sind und die gemischten Komplexe somit eine geringere Stabilität als die jeweiligen einfachen Komplexe haben.

     

Synthesis and structures of two ruthenium dibenzoylmethane triphenylphosphine mixed ligand complexes

The reaction of dibenzoylmethane (HDBM) with [RuCl₂(PPh₃)₃] in benzene in the presence of a supporting base (Et₃N) under reflux gives two different complexes, the side product as a green-yellow Ru(III) compound of composition [Ru^IIICl₂(DBM)(PPh₃)₂] (2) and the main product as a red Ru(II) complex of composition [Ru^II(DBM)₂(PPh₃)₂] (3). The products were studied by spectroscopic methods, cyclic voltammetry and X-ray single crystal diffraction. The molecular structure of 2 shows a distorted octahedral environment around the Ru atom with two phosphine ligands in trans positions. The octahedral complex 3 shows a cis arrangement of two phosphine ligands.     

Formation of Fe2+-phenanthroline complexes in the volume of hydrogel

The interaction of weakly crosslinked gels of poly(methacrylic acid) and a nonionic gel based on N-vinylcaprolactam and N-vinylimidazole with Fe²⁺ ions in aqueous solutions has been studied. A comparative study of the conformational state and of the absorption ability of the gels for their interaction with iron and ferroin ions has been performed. It has been shown that Fe²⁺ ions are efficiently absorbed by both poly(methacrylic acid) gels and the gels based on N-vinylcaprolactam and N-vinylimidazole. In this case, the poly(methacrylic acid) gels undergo contraction, while nonionic gels derived from N-vinylcaprolactam and N-vinylimidazole experience swelling. During the interaction of gels containing immobilized Fe²⁺ ions with phenanthroline, the efficient absorption of the complexon and the formation of Fe²⁺-phenanthroline complexes in the gel volume take place, thus inducing the contraction of gels. The interaction of poly(methacrylic acid) gels with ferroin is accompanied by the absorption of the complex, the formation of the tertiary complexes, and the collapse of the gel. The efficiency of formation of tertiary complexes in the gel volume is independent of their preparation procedure.     

In situ infrared spectroscopic investigations on the electrochemical properties of prussian blue-polyaniline-modified electrodes with various anionic Fe(II) complexes working as a mediator for the electroreduction of CO2

Various Fe(II) complexes have been incorporated into Prussian blue (PB)|polyaniline (PAn)-modified electrodes, and their spectroelectrochemical properties been investigated using in situ and ex situ FTIR methods. It is shown that large anionic complexes once incorporated in the PAn matrix are not dedoped during the potential cycling and the charge balance is maintained by dedoping or incorporating electrolyte cations. This electrode system was applied to the electrocatalytic reduction of CO₂ in aqueous solution, and the reduction products were identified by taking in situ FTIR spectra during the anodic stripping. At potentials higher than 0 V, the IR bands associated with the loss of carboxylic acid at 1362 cm⁻¹ and the gain of CO₂ at 2343 cm⁻¹ were simultaneously observed, indicating that the CO₂ was derived from the reoxidation of carboxylic acid. It is therefore confirmed that CO₂ can be reduced to organic species including carboxylic acid on the PB|PAn-modified electrode with anionic Fe(II) complexes in aqueous solution, with an indication that the existence of the anionic metal complex is essential to such mediated reduction of CO₂.     

Design and synthesis of a novel protected mixed ligand siderophore

A novel siderophore analog (4) has been designed to facilitate iron transport-mediated drug delivery and drug release. This mixed ligand siderophore analog includes three bidentate ligands intended to octahedrally coordinate iron (III). The ligands include a 2,3-dihydroxy benzoic acid moiety, N⁵-acetyl-N⁵-hydroxy-l-ornithine, and a β-N-hydroxy-α,β-diaminopropionic acid derivative. The total synthesis of 15, a form of 4 that is suitably protected, yet contains a free carboxylic acid for subsequent drug conjugation, is described.     

In situ compression and X-ray computed tomography of flow battery electrodes

Redox flow batteries offer a potential solution to an increase in renewable energy generation on the grid by offering long-term, large-scale storage and regulation of power. However, they are currently underutilised due to cost and performance issues, many of which are linked to the microstructure of the porous carbon electrodes used. Here, for the first time, we offer a detailed study of the in situ effects of compression on a commercially available carbon felt electrode. Visualisation of electrode structure using X-ray computed tomography shows the non-linear way that these materials compress and various metrics are used to elucidate the changes in porosity, pore size distribution and tortuosity factor under compressions from 0%-90%.