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1.
A polynuclear electronically/ionically (redox) conducting mixed-valent inorganic material such as nickel(II) hexacyanoferrate(II,III), NiHCF, was considered for potential application as a redox mediator (charge relay) in dye-sensitized solar cell (DSSC). The NiHCF redox reactions were found fast and reversible not only when the system was studied as thin film exposed to an aqueous supporting electrolyte but also as bulk material (pasted powder) in solid state, i.e., in the absence of contact with external liquid electrolyte phase. Usefulness of NiHCF material was diagnosed using conventional electroanalytical approaches, solid-state voltammetric methodology, as well as the dynamic electrochemical impedance spectroscopy technique that permitted monitoring of impedance spectra under potentiodynamic conditions. The material was utilized in a mixed-valent state, i.e., as a mixture of K4NiII[FeII(CN)6] and K3NiII[FeIII(CN)6] in which iron(II) and iron(III) sites were at the 1:1 ratio. Under such conditions, dynamics of electron-hopping between mixed-valent iron sites was maximized. Our DSSC utilized cis–dithiocyanoatobis(4,4′-dicarboxylic acid-2,2′-bipyridine) ruthenium(II) dye (N3) adsorbed onto TiO2 semiconductor and NiHCF as redox mediator. Although performance of our DSSC was not optimized in terms of the NiHCF film thickness and morphology, as well as lower photocurrents in comparison to those characteristic of the iodine/iodide based DSSC were obtained, our system yielded readily fairly high open-circuit photovoltages on the level of 800 mV. An important issue was that the formal potential of NiHCF was more positive relative to the potential of the iodide/triiodide couple while being still more negative than that equivalent to the ground state of the N3 dye. Thus, NiHCF mediator was able to regenerate the dye. 相似文献
2.
Photoelectric parameters of a dye-sensitized solar cell (DSSC) based on nanocrystalline titania with an adsorbed commercial sensitizer Ruthenizer 505 and a redox system based on the [FeL 2] · 2Otf complex (where L = 4′-(4-bipyridyl)-2,2′:6′,2″- tert-pyridine and Otf ? =CF 3SO 3 ? ) as the mediator are studied. When illuminated with a power of 100 mW/cm2, the DSSC voltage with the mediator under study and the iodide/triiodide redox pair have close values of 470 and 480 mV, respectively. The current-voltage characteristics of the DSSC with the iron complex mediator are far lower than for the iodide/triiodide redox pair. Our data indicate the slower reduction kinetics of the oxidized sensitizer species for the iron complex. The reason for this may be associated with the shift of the redox potential toward positive values in going from the iodide/triiodide redox pair to the iron complex, and thereby a reduced driving force for the reduction of the oxidized sensitizer species. We also cannot rule out that the DSSC characteristics are affected by the reduction on the photoanode of the oxidized mediator species as a result of the high reversibility of the iron complex mediator redox system. 相似文献
3.
The electroless sol-gel technique was used for the construction of nickel hexacyanoferrat (NiHCF) modified carbon composite electrodes (CCEs).This involves two steps: formation of a carbon ceramic electrode fabricated by nickel powder and then immersing the electrode into a sodium- hexacyanoferate solution for the immobilization of NiHCF films. The cyclic voltammety of the resulting modified CCEs prepared under optimum conditions, shows a well defined surface redox couple due to the [Ni IIFe III/II(CN) 6] −2/−1 system. The effect of different alkali metal cations in supporting electrolyte on the behavior of the modified electrode were studied. The charge transfer coefficient ( α) and charge transfer rate constant ( ks) for modified films were calculated. Hydrazine and hydroxylamine have been chosen as a model to elucidate the electocatalytic ability and analytical parameters of NiHCF modified CCE prepared by one and two-step sol-gel techniques and these compounds determined amperometically at the surface of modified electrodes. The latter shows a good electocatalytic activity towards the oxidation of hydrazine and hydroxylamine in the pH range 3-8 in comparison with CCEs modified by homogeneous mixture of graphite powder, Ni(NO 3) 2 and Na 2[Fe(CN) 6], (one-step sol-gel technique). Furthermore, the catalytic rate constant, linear dynamic range, limit of detection, and sensitivity for hydrazine and hydroxylamine detections were evaluated and compared with CCEs prepared with one-step sol-gel method. The modified CCEs containing NiHCF shows good repeatability, short response time, t 90%<3 s, long term stability (3 months) and excellent catalytic activity. Furthermore, the method of preparation is rapid and simple and the modified electrodes are renewed by simple mechanical polishing and immersing in [Na 3Fe(CN] 6] solution. 相似文献
4.
Abstract A series of complexes of formula [(NC) 5Fe II—NC—Fe II(CN) 4L] n?, with L = H 2O, pyridine, isonicotinamide and 4-cyanopyridine were prepared in aqueous solution by substitution of the corresponding [Fe II(CN) 5L] n? ions into [Fe II(CN) 5H 2O] 3?. The mixed valent (II, III) and fully oxidized (III, III) complexes were also obtained. The (II, II) complexes were moderately stable toward dissociation into the mononuclear species, but the mixed-valent ions were properly characterized by UV-vis-NIR spectroscopy and electrochemistry. Distinctive intervalence (IV) bands were assigned in the NIR region, with the energy being dependent on the binding properties of L; the IV band energy also correlated with the redox potential at the [NC—Fe(CN) 4L] fragment. By application of the Hush model, a valence-trapped situation was found for the [(NC) 5Fe III—NC—Fe II(CN) 4L] n? ions. The class II behavior shows, however, a value of H ab, the electronic coupling factor, of ca. 1600cm ?1, indicating a moderate-to-strong communication between the metal centers. 相似文献
5.
Polycrystalline Co 0.75Ni 0.75[Fe(CN) 6]?·?XH 2O was prepared by coprecipitation. The coprecipitated powder was annealed in vacuum at 80°C, 100°C, and 130°C. Variation of microstructural and magnetic properties with different annealed temperatures was studied by Fourier-transform infrared, X-ray diffraction, and magnetization measurements. The differences in magnetic phase transition temperature, coercivity, remanence, and effective magnetization were studied in detail. The magnetic contribution mainly results from Fe III–CN–Co II/Ni II and Fe III–NC–Co II/Ni II because Fe II–CN–Co III/Ni II carries no net spin. After annealing at 130°C, the microstructures Fe III–CN–Co II/Ni II and Fe III–NC–Co II/Ni II convert to Fe II–CN–Co III/Ni II. Differences in magnetic properties may be attributed to heat-induced microstructural changes. 相似文献
6.
The use of a zinc substrate as an electrode and the modification of its surface by means of a thin film of platinum-doped nickel hexacyanoferrate (Pt-NiHCF) were developed. The modification conditions of the zinc surface including the electroless deposition of metallic nickel on the electrode surface from NiCl 2 solution, chemical derivatization of the deposited nickel to the NiHCF film in 0.5 M K 3[Fe(CN) 6] solution, and electrochemical penetration of metallic platinum into the modified film are described. The modified zinc electrodes prepared under optimum conditions show a well-defined redox couple due to the [Ni IIFe III/II(CN) 6] 1–/2–
system. The effects of pH, the alkali metal cation, and the anion of the supporting electrolyte on the electrochemical characteristics of the modified electrode were studied in detail. The diffusion coefficients of hydrated alkali metal cations in the film ( D), the transfer coefficient ( ), and the transfer rate constant for the electron ( ks) were calculated in the presence of some alkali metal cations. The electrocatalytic activity of the modified electrode for methanol oxidation was demonstrated. The stability of the modified electrode under various experimental conditions was investigated. 相似文献
7.
Subtle differences in metal–ligand bond lengths between a series of [M 4L 6] 4? tetrahedral cages, where M=Fe II, Co II, or Ni II, were observed to result in substantial differences in affinity for hydrophobic guests in water. Changing the metal ion from iron(II) to cobalt(II) or nickel(II) increases the size of the interior cavity of the cage and allows encapsulation of larger guest molecules. NMR spectroscopy was used to study the recognition properties of the iron(II) and cobalt(II) cages towards small hydrophobic guests in water, and single‐crystal X‐ray diffraction was used to study the solid‐state complexes of the iron(II) and nickel(II) cages. 相似文献
8.
We report a novel combination of organic sensitizer and redox mediator in the electrolyte for dye-sensitized solar cells (DSSCs):
a thiophene dye and nitroxide radicals. Nitroxide radicals and their oxidized counterparts of oxoammonium cations show robust
reversible redox reactions, thus supporting robust DSSC operations. Moreover, their redox potentials ( E
1/2) and thus open-circuit voltages ( V
OC) can be tuned further by attached functional groups. Optical and electrochemical characterization reveal that these new combinations
exhibit enhanced V
OC and power conversion efficiencies compared to the existing iodine mediator (I −/I 3−) due to the increased V
OC. Also, the selection of the sensitizer–redox mediator turns out to be critical in the overall cell performance. Indeed, the
typical ruthenium dye loses its light absorption capability when it is operated in conjunction with the nitroxide radicals. 相似文献
9.
The mixed-valent oxo-centered triiron(III, III, II) trifluoroacetate complex [Fe 2IIIFe IIO(O 2CCF 3) 6(H 2O) 3] was prepared by reacting anhydrous iron(III) chloride with boiling trifluoroacetic acid under nitrogen. The non-hygroscopic and readily available mixed-valent triiron trifluoroacetate complex was found to be an efficient catalyst for the regioselective rearrangement of epoxides. A number of carbonyl compounds formed via the rearrangement of epoxides could be obtained by a simple filtration of the reaction mixture through a short plug of silica gel. 相似文献
10.
The cyano‐bridged molecular square Ni(iprtacn)] 2[Fe(phen) 2(CN) 2] 2(PF 6) 4 · 6CH 3CN ( 1 ) (iprtacn = 1,4,7‐triisopropyl‐1,4,7‐triazacyclononane, phen = 1, 10‐phenanthroline) was prepared and its crystal structure, magnetic properties, and binding with DNA were characterized. The four metal ions Ni IIFe IINi IIFe II of the complex 1 are almost coplanar. Magnetic susceptibilities measured over the range of 2–300 K show weak antiferromagnetic interactions between the two nickel(II) ions; best fitting for the experimental data leads to J = –1.27 cm –1. UV/Vis and fluorescence spectra show that the complex is able to displace DNA‐bound EB and bind to DNA with strong interactions. 相似文献
11.
EMR studies of bis(benzene-dithiocarboxylato)copper(II) in the form of the pure solid sample, in solution as well as magnetically diluted in the host lattices of the corresponding complexes of Ni II, Zn II, Pd II, and Pt II are reported. Two different samples (violet and blue) have been obtained in the Ni II complex host lattice with EMR spectra indicating a superposition of several individual Cu II signals. The EMR spectrum of the violet sample is explained by a superposition of the individual signals of (thio-, perthio-carboxylate)Cu II and bis(perthiocarboxylate)Cu II while that for the blue Cu/Ni(dtb) 2 complex, as well as for Cu/Pd (dtb) 2 is explained by different positions of the Cu II species in the host lattices. The EMR spectrum typical for the magnetically diluted sample caused by self redox reaction has been recorded in the pure solid sample of copper(II) dithiocarboxylate complex. 相似文献
12.
The use of the [Fe III(AA)(CN) 4] ? complex anion as metalloligand towards the preformed [Cu II(valpn)Ln III] 3+ or [Ni II(valpn)Ln III] 3+ heterometallic complex cations (AA=2,2′‐bipyridine (bipy) and 1,10‐phenathroline (phen); H 2valpn=1,3‐propanediyl‐bis(2‐iminomethylene‐6‐methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu II(valpn)Ln III(H 2O) 3(μ‐NC) 2Fe III(phen)(CN) 2 {(μ‐NC)Fe III(phen)(CN) 3}]NO 3 ? 7 H 2O} n (Ln=Gd ( 1 ), Tb ( 2 ), and Dy ( 3 )) and the trinuclear complex [Cu II(valpn)La III(OH 2) 3(O 2NO)(μ‐NC)Fe III(phen)(CN) 3] ? NO 3 ? H 2O ? CH 3CN ( 4 ) were obtained with the [Cu II(valpn)Ln III] 3+ assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni II(valpn)Ln III(ONO 2) 2(H 2O)(μ‐NC) 3Fe III(bipy)(CN)] ? 2 H 2O ? 2 CH 3CN} n (Ln=Gd ( 5 ), Tb ( 6 ), and Dy ( 7 )) resulted with the related [Ni II(valpn)Ln III] 3+ precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu II(valpn)La III(OH 2) 3(O 2NO)(μ‐NC)Fe III(phen)(CN) 3] +, nitrate counterions, and non‐coordinate water and acetonitrile molecules. The heteroleptic {Fe III(bipy)(CN) 4} moiety in 5 – 7 acts as a tris‐monodentate ligand towards three {Ni II(valpn)Ln III} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu II?Ln III ( 1 – 3 ) and Ni II?Ln III ( 5 – 7 ) units, as well as through the single cyanide bridge between the Fe III and either Ni II ( 5 – 7 ) or Cu II ( 4 ) account for the overall ferromagnetic behavior observed in 1 – 7 . DFT‐type calculations were performed to substantiate the magnetic interactions in 1 , 4 , and 5 . Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out‐of‐phase ac signals below 4.0 K in the lack of a dc field, the values of the pre‐exponential factor ( τo) and energy barrier ( Ea) through the Arrhenius equation being 2.0×10 ?12 s and 29.1 cm ?1, respectively. In the case of 7 , the ferromagnetic interactions through the double phenoxo (Ni II–Dy III) and single cyanide (Fe III–Ni II) pathways are masked by the depopulation of the Stark levels of the Dy III ion, this feature most likely accounting for the continuous decrease of χM T upon cooling observed for this last compound. 相似文献
13.
Thin layer technique was applied to the indirect anodic oxidation of histamine, catalyzed by NiSO 4. Coulometric determination of the electron number demonstrates that histamine complexes Ni (II) and resulting adducts can be electrochemically oxidized in a single‐electron reaction, to lead Ni (III)‐histamine. The system Ni (III)/Ni (II) acts as ‘redox mediator’ for histamine oxidation. The equilibrium constant of the Ni (II)‐histamine complex formation was 10 6 , value showing the strong affinity between species. High content of histamine (>0.1 M), detected in fresh fish (previously exposed to the sun) extracts, showing potentialities for future design of a sensor for direct measurement in fish. 相似文献
14.
Gaussian analysis of the electronic spectra of 25 bis(dimethylglyoximato)iron(II) complexes containing axial N-heterocyclic ligands are discussed and comparisons made with the spectra of the corresponding [Fe(CN) 5L] 3– complexes. The energies of the metal-to-axial and metal-to-equatorial ligand charge-transfer transitions exhibit opposite trends, correlating with the electronic properties of the axial ligands, and with the redox potentials of the Fe II/Fe III couple. 相似文献
15.
Two zinc(II) and nickel(II) based coordination polymers, {[Zn(bibp)(MoO 4)](H 2O) 2} n ( 1 ) [bibp = 4,4′‐bis(imidazol‐1‐yl)‐biphenyl] and [Ni 2(CN) 4(phen) 2] n ( 2 ) (phen = 1,10‐phenanthroline), were synthesized and structurally characterized under solvothermal conditions. Compound 1 can be viewed as the connection of the 1D W‐type chain [Zn( trans‐bibp)] with the MoO 42– anion to form a uninodal 4‐connected net, whereas 2 features one‐dimensional Ni II cyanide chains decorated either with linear Ni(CN) 4 side chains or with 1,10‐phenanthroline ligands bound directly to the Ni II sites of the parent chain. In addition, in vitro anticancer activities of compounds 1 and 2 on four human breast cancer cells (MDA‐MB‐231, MDA‐MB‐468, SK‐BR‐3, and MCF7) was further determined. 相似文献
16.
In recent years dye‐sensitized solar cells (DSSCs) have emerged as one of the alternatives for the global energy crisis. DSSCs have achieved a certified efficiency of >11% by using the I ?/I 3? redox couple. In order to commercialize the technology almost all components of the device have to be improved. Among the various components of DSSCs, the redox couple that regenerates the oxidized sensitizer plays a crucial role in achieving high efficiency and durability of the cell. However, the I ?/I 3? redox couple has certain limitations such as the absorption of triiodide up to 430 nm and the volatile nature of iodine, which also corrodes the silver‐based current collectors. These limitations are obstructing the commercialization of this technology. For this reason, one has to identify alternative redox couples. In this regard, the Co(II/III) redox couple is found to be the best alternative to the existing I ?/I 3? redox couple. Recently, DSSC test cell efficiency has risen up to 13% by using the cobalt redox couple. This review emphasizes the recent development of Co(II/III) redox couples for DSSC applications. 相似文献
17.
Complexing processes in M II- N-diisopropoxythiophosphorylthiobenzamide binary systems (M = Co, Ni, Cu) in metal(II) hexacyanoferrate(II) gelatin-immobilized matrices upon contact with aqueous–alkaline (pH = 12.0 ± 0.1) solutions of organic compounds have been studied. It has been shown that, in Co II and Cu II, the initial act of complexing involves destruction of the Co II and Cu II hexacyanoferrates(II) by OH – ions, leading to formation of the corresponding hydroxides which react with the ligand indicated. In the both systems, successive addition of two ligand molecules per M(OH) 2 fragment occurs and [MB(OH)(OH 2)] and [MB 2] coordination compounds are formed (B –-a singly deprotonated ligand form). In the Ni II- N-diisopropoxythiophosphorylthiobenzamide system, the formation of three complexes, (Ni 2BOH) 2[Fe(CN) 6], [NiB(OH)(OH 2)] and [NiB 2] occurs. 相似文献
18.
The local symmetry and local magnetic properties of 6 nm‐sized, bimetallic, cyanide‐bridged CsNiCr(CN) 6 coordination nanoparticles 1 and 8 nm‐sized, trimetallic, CsNiCr(CN) 6@CsCoCr(CN) 6 core–shell nanoparticles 2 were studied by X‐ray absorption spectroscopy (XAS) and X‐ray magnetic circular dichroism (XMCD). The measurements were performed at the Ni II, Co II, and Cr III L 2,3 edges. This study revealed the presence of distorted Ni II sites located on the particle surface of 1 that account for the uniaxial magnetic anisotropy observed by SQUID measurements. For the core–shell particles, a combination of the exchange anisotropy between the core and the shell and the pronounced anisotropy of the Co II ions is the origin of the large increase in coercive field from 120 to 890 Oe on going from 1 to 2 . In addition, XMCD allows the relative orientation of the magnetic moments throughout the core–shell particles to be determined. While for the bimetallic particles of 1 , alignment of the magnetic moments of Cr III ions with those of Ni II ions leads to uniform magnetization, in the core–shell particles 2 the magnetic moments of the isotropic Cr III follow those of Co II ions in the shell and those of Ni II ions in the core, and this leads to nonuniform magnetization in the whole nanoobject, mainly due to the large difference in local anisotropy between the Co II ions belonging to the surface and the Ni II ions in the core. 相似文献
19.
Complexing processes in the Ni II- TTA-methanal ( A) and Ni II- TTA-propanone ( B) triple systems ( TTA–5-methyl-4-amino-3-thiooxo-1, 2, 4-triazapentene-1) in ethanol solution and nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix have been studied. In the Ni II- TTA- methanal system, formation of Ni II oligomeric coordination compounds in which metal chelate cycles are connected by–H 2C–O–CH 2–structural groups, takes place. In the Ni II- TTA-propanone triple system, formation of only Ni II complexes with TTA takes place. No complexing process in the triple systems in nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix was found. 相似文献
20.
Novel complexing processes in the Fe II-8-mercaptoquinoline, Fe II-5-chloro-8-mercaptoquinoline and Fe II-5-bromo-8-mercaptoquinoline systems, not used previously in coordination chemistry, namely complexing as an iron(III)hexacyanoferrate(II) gelatin-immobilized matrix (GIM) in contact with an aqueous solution of the corresponding ligand, have been observed and analysed. Incorporation of these ligands into the inner coordination sphere is preceded by the decomposition of the immobilized compound KFe[Fe(CN) 6] to form hydroxides or oxohydroxides of Fe II and Fe III under the action of OH - ions. It has been shown that Fe IIFeIII redox process and the formation of FeB 3 chelates (B - is a singly deprotonated form of the corresponding ligand) take place during complexing under such conditions. 相似文献
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