Synthesis of Co0.5Mn0.1Ni0.4C2O4⋅n H2O Micropolyhedrons: Multimetal Synergy for High‐Performance Glucose Oxidation Catalysis

Owing to the synergy between metals, trimetal oxalate micropolyhedrons have been synthesized by means of a room‐temperature coprecipitation strategy. The effect of their nanoscale size on their electrochemical performance toward glucose oxidation was investigated. In particular, the Co_0.5Mn_0.1Ni_0.4C₂O₄?n H₂O micropolyhedrons illustrated prominent electrocatalytic activity for the glucose oxidation reaction. Additionally, the Co_0.5Mn_0.1Ni_0.4C₂O₄?n H₂O micropolyhedrons, when used as an electrode material, illustrated an excellent lower limit of detection (1.5 μm ), a wide detection concentration range (0.5–5065.5 μm ), and a high sensitivity (493.5 μA mm ^?1 cm^?2). Further analysis indicated that the effectively improved conductivity may have been due to the small size of the materials, and it was easier to form a flat film when Nafion was coated onto the glassy carbon electrode.     

Binderless Solution Processed Zn Doped Co3O4 Film on FTO for Rapid and Selective Non‐enzymatic Glucose Detection

A simple solution based deposition process has been used to fabricate Zn doped Co₃O₄ electrode as an electrocatalyst for non‐enzymatic oxidation of glucose. XRD, HRTEM, SEM, EELS, AFM, EIS was used to characterise the electrode. The addition of Zn as dopant on Co₃O₄ resulted in enhanced electrochemical performance of Zn:Co₃O₄ material compared to pristine Co₃O₄ due to increased charge transferability. The as prepared electrode showed fast response (<7 s) time, good sensitivity (193 μA mM⁻¹ cm⁻²) in the linear range of 5 μM–0.62 mM, good selectivity towards glucose at a relatively lower applied potential of +0.52 V in 0.1 M NaOH solution. A detection limit of ∼2 μM was measured for the Zn:Co₃O₄ electrode. The applied fabrication method resulted in good inter and intra electrode reproducibility as was shown by the lower relative standard deviation values (R.S.D). The electrode retained 70 % of initial current response after 30 days. Although the as prepared Zn:Co₃O₄ electrodes did not result in highest reported sensitivity, and lowest limit of detection; the ease of fabrication and scalability of production, good inter and intra electrode reproducibility makes it a potential candidate for commercial application as glucose sensor.     

Oxygen non-stoichiometry of Ln4Ni2.7Fe0.3O10−δ (Ln=La, Pr)

The oxygen deficiency of iron-substituted nickelates Ln₄Ni_2.7Fe_0.3O_10−δ (Ln=La, Pr) with the orthorhombic Ruddlesden-Popper structure was studied by thermogravimetric analysis and coulometric titration in the oxygen partial pressure range 6×10⁻⁵ to 0.7 atm at 973-1223 K. In air, the non-stoichiometry values vary in the relatively narrow ranges (2.4−4.2)×10⁻² for La- and (0.01−2.0)×10⁻² for Pr-containing compositions, increasing with temperature. Due to the smaller size of praseodymium cations, Pr₄Ni_2.7Fe_0.3O_10−δ exhibits a substantially lower thermodynamic stability in comparison with La₄Ni_2.7Fe_0.3O_10−δ and La₄Ni₃O_10−δ, although the oxygen content in Pr₄Ni_2.7Fe_0.3O_10−δ lattice is higher. The partial substitution of iron for nickel has no essential effect on the low-p(O₂) stability limit corresponding to the transition of Pr₄Ni₃O_10−δ into K₂NiF₄-type Pr₂NiO_4+δ. On the contrary, doping of La₄Ni₃O_10−δ with iron decreases the oxygen vacancy concentration and shifts the phase stability boundary towards lower oxygen chemical potentials, suggesting a stabilization of the transition metal-oxygen octahedra in lanthanum nickelate lattice. The Mössbauer spectroscopy showed that the predominant state of iron cations, statistically distributed between the nickel sites, is trivalent.     

Fabrication of Hierarchically Structured MOF‐Co3O4 on Well‐aligned CuO Nanowire with an Enhanced Electrocatalytic Property

Engineering appropriate shape and size of three‐dimensional inorganic nanostructures materials is of one the main critical problems in pursuing high‐performance electrode materials. Herein, we fabricate a metal‐organic framework derived cobalt oxide (Co₃O₄) are grown on copper oxide nanowire (CuO NWs) supported on the surface of 3D copper foam substrate. The highly aligned CuO NWs were prepared by using electrochemical anodization of copper foam in ambient temperature and followed by MOF Co₃O₄ was grown via a simple in situ solution deposition then consequent calcination process. The obtained binder‐free 3D CuO NWs@Co₃O₄ nanostructures were further characterized by using X‐ray diffraction, X‐ray photoelectron spectroscopy, field‐emission scanning electron microscopy, and transmission electron microscopy. Furthermore, electrochemical sensing of glucose was studied by using Cyclic Voltammetry, and chronoamperometry techniques. Interestingly, 3D CuO NWs@Co₃O₄ electrode exhibits excellent performance for the oxidation of glucose compared with individual entities. The proposed sensor shows wide linear ranges from 0.5 μM to 0.1 mM with the sensitivity of 6082 μA/μM and the lowest detection limit (LOD) of 0.23 μM was observed with the signal to noise ratio, (S/N) of 3. The superior catalytic oxidation of glucose mainly is endorsed by the excellent electrical conductivity and synergistic effect of the Co₃O₄ and CuO NWs.     

Selective Electrochemical Epinephrine Sensor Using Self‐Assembled Monomolecular Film of 1,8,15,22‐Tetraaminophthalocyanatonickel(II) on Gold Electrode

This article describes the highly sensitive and selective determination of epinephrine (EP) using self‐assembled monomolecular film (SAMF) of 1,8,15,22‐tetraamino‐phthalocyanatonickel(II) (4α‐Ni^IITAPc) on Au electrode. The 4α‐Ni^IITAPc SAMF modified electrode was prepared by spontaneous adsorption of 4α‐Ni^IITAPc from dimethylformamide solution. The modified electrode oxidizes EP at less over potential with enhanced current response in contrast to the bare Au electrode. The standard heterogeneous rate constant (k°) for the oxidation of EP at 4α‐Ni^IITAPc SAMF modified electrode was found to be 1.94×10^?2 cm s^?1 which was much higher than that at the bare Au electrode. Further, it was found that 4α‐Ni^IITAPc SAMF modified electrode separates the voltammetric signals of ascorbic acid (AA) and EP with a peak separation of 250 mV. Using amperometric method the lowest detection limit of 50 nM of EP was achieved at SAMF modified electrode. Simultaneous amperometric determination of AA and EP was also achieved at the SAMF modified electrode. Common physiological interferents such as uric acid, glucose, urea and NaCl do not interfere within the potential window of EP oxidation. The present 4α‐Ni^IITAPc SAMF modified electrode was also successfully applied to determine the concentration of EP in commercially available injection.     

Preparation of Co3O4/graphene Oxide Composites by a Depositing‐decompostion Method and its Application for Electrochemical Determination of Glucose

Co₃O₄/graphene oxide (GO) nanocomposites were successfully prepared by a depositing‐decomposition method. The as‐prepared samples were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Cyclic voltammetry (CV) was used to evaluate the electrochemical response of a glass carbon electrode (GCE) modified with Co₃O₄/GO nanocomposite towards glucose. Compared with the Co₃O₄/GCE, the Co₃O₄/GO/GCE exihibits higher electrocatalytic activity due to the synergistic effects of electrocatalytic ability of Co₃O₄ and large surface of GO. The Co₃O₄/GO/GCE was applied for glucose detection in alkaline solution. The linear current response range of glucose on Co₃O₄/GO/GCE covered the range from 9 × 10^?5 to 6.03 × 10^?3 M, with a detection limit of 5.2 × 10^?7 M (S/N = 3).     

Novel Sn Doped Co3O4 Thin Film for Nonenzymatic Glucose Bio‐Sensor and Fuel Cell

A facile chemical solution deposition via two‐step spin coating technique was used to fabricate nano‐particulate novel Sn doped Co₃O₄ thin film for glucose sensor and fuel cell applications. Substitution of Sn into Co₃O₄ host lattice lead to a remarkable increase in the electrocatalytic activity of the Co₃O₄ electrode material. Film thickness played a significant role in enhancing the charge transferability of the electrode as was observed from electrochemical impedance spectroscopy (EIS). The best sensor exhibited two wide linear response ranges (2 μM up to ∼0.5 mM and 0.6 mM up to ∼5.5 mM respectively) with sensitivities of 921 and 265 μA cm⁻² mM⁻¹ respectively and low limit of detection of 100 nM (S/N=3). The sensor was very selective towards glucose in the presence of various interference and showed long term stability. Moreover, the developed thin film modified electrode could generate one electron current in nonenzymatic fuel cell setup at room temperature.     

Flow Injection Analysis of Sulfide Using a Cinder/Tetracyano Nikelate Modified Screen‐Printed Electrode

Flow injection analysis (FIA) of sulfide is presented using a screen‐printed carbon electrode modified with a cinder/tetracyano nickelate hybrid (designated as cinder/NiTcSPE). Hybridization of NiTc was achieved in iron‐enriched industrial waste cinder material through the bimetallic formation of Fe^III[Ni^II(CN)₄]. The electrocatalytic oxidation of sulfide is mediated by the higher oxidation state of Ni in this hybrid‐bimetallic complex. The system shows a detection limit (S/N=3) of 0.06 μM and a linear working range up to 1 mM in pH 10, 0.1 M KCl solution. Taking into account the relatively low volatility of the analyte in alkaline conditions, the system is ideally suited for the accurate detection of sulfide. The response of the electrode to sulfide is highly reproducible, thereby offering the potential development of a disposable amperometric sensor for sulfide. Selective detection of sulfide in cigarette smoke is presented in this study as an example of a real sample application.     

Hole‐Boosted Cu(Cr,M)O2 Nanocrystals for All‐Inorganic CsPbBr3 Perovskite Solar Cells

The all‐inorganic CsPbBr₃ perovskite solar cell (PSC) is a promising solution to balance the high efficiency and poor stability of state‐of‐the‐art organic–inorganic PSCs. Setting inorganic hole‐transporting layers at the perovskite/electrode interface decreases charge carrier recombination without sacrificing superiority in air. Now, M‐substituted, p‐type inorganic Cu(Cr,M)O₂ (M=Ba²⁺, Ca²⁺, or Ni²⁺) nanocrystals with enhanced hole‐transporting characteristics by increasing interstitial oxygen effectively extract holes from perovskite. The all‐inorganic CsPbBr₃ PSC with a device structure of FTO/c‐TiO₂/m‐TiO₂/CsPbBr₃/Cu(Cr,M)O₂/carbon achieves an efficiency up to 10.18 % and it increases to 10.79 % by doping Sm³⁺ ions into perovskite halide, which is much higher than 7.39 % for the hole‐free device. The unencapsulated Cu(Cr,Ba)O₂‐based PSC presents a remarkable stability in air in either 80 % humidity over 60 days or 80 °C conditions over 40 days or light illumination for 7 days.     

Redox Non‐Innocence of Nitrosobenzene at Nickel

Nitrosobenzene (PhNO) serves as a stable analogue of nitroxyl (HNO), a biologically relevant, redox‐active nitric oxide derivative. Capture of nitrosobenzene at the electron‐deficient β‐diketiminato nickel(I) complex [ⁱPr₂NN_F6]Ni results in reduction of the PhNO ligand to a (PhNO)^./? species coordinated to a square planar Ni^II center in [ⁱPr₂NN_F6]Ni(η²‐ONPh). Ligand centered reduction leads to the (PhNO)^2? moiety bound to Ni^II supported by XAS studies. Systematic investigation of structure–reactivity patterns of (PhNO)^./? and (PhNO)^2? ligands reveals parallels with superoxo (O₂)^./? and peroxo (O₂)^2? ligands, respectively, and forecasts reactivity patterns of the more transient HNO ligand.     

Synthesis of Ferrocene Based Naphthoquinones and its Application as Novel Non‐enzymatic Hydrogen Peroxide

At present, a highly sensitive hydrogen peroxide (H₂O₂) sensor is fabricated by ferrocene based naphthaquinone derivatives as 2,3‐Diferrocenyl‐1,4‐naphthoquinone and 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone. These ferrocene based naphthaquinone derivatives are characterized by H‐NMR and C‐NMR. The electrochemical properties of these ferrocene based naphthaquinone are investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) on modified glassy carbon electrode (GCE). The modified electrode with ferrocene based naphthaquinone derivatives exhibits an improved voltammetric response to the H₂O₂ redox reaction. 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone show excellent non‐enzymatic sensing ability towards H₂O₂ response with a detection limitation of 2.7 μmol/L a wide detection range from 10 μM to 400 μM in H₂O₂ detection. The sensor also exhibits short response time (1 s) and good sensitivity of 71.4 μA mM^?1 cm^?2 and stability. Furthermore, the DPV method exhibited very high sensitivity (18999 μA mM^?1 cm^?2) and low detection limit (0.66 μM) compared to the CA method. Ferrocene based naphthaquinone derivative based sensors have a lower cost and high stability. Thus, this novel non‐enzyme sensor has potential application in H₂O₂ detection.     

Complexes of 2-furaldehyde 4-phenyl semicarbazone

The synthesis of Co^II, Ni^II, Cu^II and Cd^II complexes of 2-furfural 4-phenyl semicarbazone (FPSC) with stoichiometric formulae: [M(FPSC)₂X₂] (M = Co, Ni or Cu; X = Cl or Br), [CuCl₂(FPSC)] and [(CdCl₂)₂(FPSC)] has been obtained for the first time. The complexes were characterized by elemental analysis, molar conductivity, magnetic measurements, i.r., far i.r. and electronic spectra. FPSC is deduced to act as a bidentate ligand in the Co^II, Ni^II and Cu^II complexes and as a tetradentate one in [(CdCl₂)₂(FPSC)].     

Urchin‐like Ag Nanowires as Non‐enzymatic Hydrogen Peroxide Sensor

Urchin‐like Ag nanowires were prepared by reacting AgNO₃(aq) with Cu metal in the presence of cetyltrimethylammonium chloride and HNO₃(aq) on a screen printed carbon electrode at room temperature. The diameters of the nanowires were about 100 nm, while the lengths were up to 10 μm. Cyclic voltammetric experiments using the Ag nanowires as the working electrode showed electrocatalytic H₂O₂ reduction. The electrode exhibited a high sensitivity of 4705 μA mM^‐1 mg^‐1 cm^‐2 from 50 μM to 10.35 mM and a measurable detection limit of 10 μM in amperometric detection. This is the first report on Ag NWs for non‐enzymatic H₂O₂ sensing.     

Electrochemically Prepared Three‐dimensional Porous Nitrogen‐doped Graphene Modified Electrode for Non‐enzymatic Detection of Hydrogen Peroxide

A facile and green electrochemical method for the fabrication of three‐dimensional porous nitrogen‐doped graphene (3DNG) modified electrode was reported. This method embraces two consecutive steps: First, 3D graphene/polypyrrole (ERGO/PPy) composite was prepared by electrochemical co‐deposition of graphene and polypyrrole on a gold foil. Subsequently, the ERGO/PPy composite modified gold electrode was annealed at high temperature. Thus 3DNG modified electrode was obtained. Scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to characterize the structure and morphology of the electrode. The electrode exhibits excellent electroanalytical performance for the reduction of hydrogen peroxide (H₂O₂). By linear sweep voltammetric measurement, the cathodic peak current was linearly proportional to H₂O₂ concentration in the range from 0.6 μM to 2.1 mM with a sensitivity of 1.0 μA μM⁻¹ cm⁻². The detection limit was ascertained to be 0.3 μM. The anti‐interference ability, reproducibility and stability of the electrode were carried out and the electrode was applied to the detection of H₂O₂ in serum sample with recoveries from 98.4 % to 103.2 %.     

On the nature of the chemical bond in heterobimetallic palladium(II) complexes with divalent 3<Emphasis Type="Italic">d</Emphasis> metals

The complex Pd(μ-OOCMe)₄Cu(OH₂) · 2Pd₃(μ-OOCMe)₆ was synthesized and characterized by X-ray crystallography. In the heterometallic moiety of this complex, the Pd^II and Cu^II atoms are at an extraordinary short distance (2.521(3) Å). DFT quantum-chemical calculations of the geometric and electronic structure of a series of heterobinuclear paddlewheel complexes Pd^IIM^II(μ-OOCMe)₄L (M = Zn^II, Ni^II, Cu^II, Co^II, Fe^II; L = OH₂ and NCH) and their formate analogues Pd^IIM^II(μ-OOCH)₄L (M = Zn^II, Ni^II, Fe^II) showed that the extraordinary short Pd?M distance in all these complexes is caused only by the tightening effect of carboxylate bridges rather than by the metal-metal bond. The direct Pd-M interaction becomes possible only after removal of electrons from the antibonding orbitals and formation of oxidized complexes of the [Pd^III(μ-OOCMe)₄Ni^III]²⁺ type.     

Syntheses,Structures, and Bioactivities Evaluation of some Transition Metal Complexes with 4,4'-Diacetylcurcumin

Stoichiometric reactions of 4,4'-diacetylcurcumin ( HL ) with series of transition metal ions, namely Fe³⁺, Co²⁺, Ni²⁺ and Zn²⁺, in methanol result in the corresponding homoleptic metal complexes. All the obtained complexes were characterized by elemental analysis, high resolution mass spectrometry, IR spectroscopy, magnetic moment and single-crystal X-ray diffraction. Structural analyses are unprecedentedly performed for the Fe^III, Co^II, and Ni^II complexes and reveal octahedral mononuclear complexes with the compositions [Fe(L)₃] and [M(L)₂(MeOH)₂] (M = Co²⁺, Ni²⁺, Zn²⁺) for trivalent and divalent metal ions, respectively. In all complexes, the deprotonated ligands serve as monoanionic and bidentate ligands with (O,O)-chelating β-diketonate moieties. The free ligand HL exhibits considerable antiproliferative effects for the human MCF-7 breast and HepG2 liver cancer cells with IC₅₀ values of 20.91 ± 2.16 μg · mL^–1 and 12.85 ± 1.85 μg · mL^–1, respectively. The Co^II and Zn^II complexes with IC₅₀ values in the range of 14.53–20.80 μg · mL^–1 for MCF-7 breast and 8.48–10.68 μg · mL^–1 for HepG2 liver cancer cells show stronger antiproliferative effects than HL, the Fe^III and Ni^II complexes cause weaker reductions of the growth of the two tested cancer cell lines.     

Synthesis and characterization of new synthetic oxygen carriers. A kinetic study of the reaction of the binuclear iron(III)–copper(II) complex with H<Subscript>2</Subscript>O<Subscript>2</Subscript>

New oxygen carriers have been synthesized by the interaction of the Cu^II/Ni^II derivative of the bis(5-nitroindazolyl)methane complex with 14-membered 1,8-dihydro-1,3,6,8,10,13-hexaazacyclotetradecane (M-mac), where M=Fe^III, Ni^II, Co^II, to yield binuclear complexes. These complexes have been characterized by physico-chemical methods: elemental analysis, i.r., ¹H-n.m.r., ¹³C-n.m.r., 2D cosy n.m.r., e.p.r., u.v.–vis. spectroscopy and cyclic voltammetry. A representative binuclear Fe^III–Cu^II complex was chosen to interact with H₂O₂ to elucidate the mechanistic pathway of oxygen binding in solution spectrophotometrically, and also by cyclic voltammetry. Hydrogen peroxide exhibits two mechanisms for binding, either (i) homolysis or (ii) heterolytic cleavage. The mode of H₂O₂ binding can be hazardous in (i) due to the threat of oxidative damage to the cellular structure, proteins and metabolites, or eco-friendly as in (ii) which produces innocuous products such as water and dioxygen. This study aims to combat the problems associated with H₂O₂ binding in nature by producing a parallel study on model compounds.     

Direct Electrochemistry and Electrocatalysis of Hemoglobin Immobilized in a Polymeric Ionic Liquid Film

A polymer film based on polymeric ionic liquid, which was poly(1‐vinyl‐3‐butylimidazolium chloride) (poly(ViBuIm⁺Cl^?)for short), was firstly used as matrix to immobilize hemoglobin (Hb). FTIR and UV‐vis spectra demonstrated that the native structure of Hb was well preserved after entrapped into the polymer film. The Hb immobilized in the poly(ViBuIm⁺Cl^?) film showed a fast direct electron transfer for the Hb‐Fe^III/Fe^II redox couple. Based on the direct electron transfer of the immobilized Hb, polyvinyl alcohol (PVA)/Hb/poly(ViBuIm⁺Cl^?)/GC electrode displayed good sensitivity and wide linear range for the detection of H₂O₂. The linear range of the PVA/Hb/poly(ViBuIm⁺Cl^?)/GC electrode to H₂O₂ is from 3.5 to 224 μM with a limit of detection of 1.17 μM. Such an avenue, which integrated polymeric ionic liquid and redox protein via a simple method, may provide a novel and efficient platform for the fabrication of biosensors, biofuel cells and other bioelectrochemical devices.     

Derivatives of the 21-tungsto-9-antimonate heteropolyanion. Part 2. Addition of transition metal cations

Ammonium salts of five new heteropolytungstates, [NaSb₉W₂₁O₈₆M₃]^12,9− (M=Mn^II, Fe^III, Co^II, Ni^II, Cu^II) have been prepared and characterized by elemental analysis, visible and i.r. spectroscopy, magnetic susceptibility measurements, and cyclic voltammetry. Evidence for ligand substitution at the M cation centres is presented, and possible binding sites for M on the polyanion surface are discussed.     

Perovskite SrCo0.9Nb0.1O3−δ as an Anion‐Intercalated Electrode Material for Supercapacitors with Ultrahigh Volumetric Energy Density

We have synthesized and characterized perovskite‐type SrCo_0.9Nb_0.1O_3−δ (SCN) as a novel anion‐intercalated electrode material for supercapacitors in an aqueous KOH electrolyte, demonstrating a very high volumetric capacitance of about 2034.6 F cm⁻³ (and gravimetric capacitance of ca. 773.6 F g⁻¹) at a current density of 0.5 A g⁻¹ while maintaining excellent cycling stability with a capacity retention of 95.7 % after 3000 cycles. When coupled with an activated carbon (AC) electrode, the SCN/AC asymmetric supercapacitor delivered a specific energy density as high as 37.6 Wh kg⁻¹ with robust long‐term stability.