Application of the Bismuth Film Electrode for Voltammetric Determination of Titanium Using Ti(IV)‐Oxalate‐Chlorate Catalytic System

The catalytic voltammetric protocol for the determination of titanium at a bismuth film electrode is presented. The method is based on the reduction of the Ti(IV)‐oxalate complex to Ti(III)‐oxalate in an acidic solution. It was proven that the addition of KClO₃ causes rapid oxidation of Ti(III)‐oxalate and, subsequently, an increase of the reduction peak current of Ti(IV) at the bismuth film electrode. Parameters that influence the Ti response, including the film preparation, solution pH, oxalate acid and chlorate concentrations, were optimized. The exploitation of the bismuth film electrode under the optimized conditions yielded a stable response for titanium, with high sensitivity (12.5 μA μM^?1), good precision (RSD=5.0%) and a low detection limit (1×10^?8 M).     

An Organic Sol‐Gel Film as Modifier to Construct Biosensor

A new amperometric biosensor for hydrogen peroxide (H₂O₂) was developed by adsorbing hemoglobin (Hb) on an organic sol‐gel film. The organic sol‐gel was prepared using resorcinol and formaldehyde as monomers. This sol‐gel film shows a biocompatible microenvironment for retaining the native activity of the adsorbed Hb. The direct electron transfer between Hb and electrode is achieved. Hb adsorbed on the film shows an enzyme‐like catalytic activity for the reduction of H₂O₂. The reduction peak currents are proportional linearly to the concentration of hydrogen peroxide in the range of 6×10^?8 to 3.6×10^?6 M, with a detection limit of 2.4×10^?8 M (S/N=3). This research enlarges the applications of organic sol‐gel materials in biosensor field.     

The Effect of Ionic Liquid Covalent Bonding to Sol‐Gel Processed Film on Ion Accumulation and Transfer

Accumulation of electroactive anions into a silicate film with covalently bonded room temperature ionic liquid film deposited on an indium tin oxide electrode was studied and compared with an electrode modified with an unconfined room temperature ionic liquid. A thin film containing imidazolium cationic groups was obtained by sol‐gel processing of the ionic liquid precursor 1‐methyl‐3‐(3‐trimethoxysilylpropyl)imidazolium bis(trifluoromethylsulfonyl)imide together with tetramethylorthosilicate on the electrode surface. Profilometry shows that the obtained film is not smooth and its approximate thickness is above 1 μm. It is to some extent permeable for a neutral redox probe – 1,1′‐ferrocene dimethanol. However, it acts as a sponge for electroactive ions like Fe(CN)₆^3?, Fe(CN)₆^4? and IrCl₆^3?. This effect can be traced by cyclic voltammetry down to a concentration equal to 10^?7 mol dm^?3. Some accumulation of the redox active ions also occurs at the electrode modified with the ionic liquid precursor, but the voltammetric signal is significantly smaller compare with the bare electrode. The electrochemical oxidation of the redox liquid t‐butyloferrocene deposited on silicate confined ionic liquid film is followed by the expulsion of the electrogenerated cation into an aqueous solution. On the other hand, the voltammetry obtained with the electrode modified with t‐butyloferrocene solution in the ionic liquid precursor exhibits anion sensitive voltammetry. This is explained by anion insertion into the unconfined ionic liquid deposit following t‐butylferricinium cation formation.     

Highly Sensitive and Selective Adsorptive Stripping Voltammetric Method Employing a Lead Film Screen‐printed Electrode for Determination of Cobalt as its Nioximate Complex

A carbon screen‐printed electrode modified in‐situ with lead film (PbF‐SPCE) was applied for the adsorptive stripping voltammetric determination of Co(II) in the form of a complex with 1,2‐cyclohexanedione dioxime. Lead film was electrochemically deposited in situ on SPCE from a 0.2 M ammonia buffer solution (pH 8.7) containing 5 ? 10^?5 M Pb(NO₃)₂ and 5 ? 10^?5 M nioxime. Due to the very low LOD (0.003 µgL^?1, i.e., 0.05 nmol L^?1 Co(II); t_acc=120s), the developed procedure could be rated among the most sensitive methods employing SPEs. The Ni(II) signal was significantly lower than the Co(II) one and the separation of Ni(II) and Co(II) peaks was even better at the PbF‐SPCE than at the hanging mercury drop electrode.     

2D Semiconducting Metal–Organic Framework Thin Films for Organic Spin Valves

2D conductive metal–organic frameworks (2D c‐MOFs) feature promising applications as chemiresistive sensors, electrode materials, electrocatalysts, and electronic devices. However, exploration of the spin‐polarized transport in this emerging materials and development of the relevant spintronics have not yet been implemented. In this work, layer‐by‐layer assembly was applied to fabricate highly crystalline and oriented thin films of a 2D c‐MOF, Cu₃(HHTP)₂, (HHTP: 2,3,6,7,10,11‐hexahydroxytriphenylene), with tunable thicknesses on the La_0.67Sr_0.33MnO₃ (LSMO) ferromagnetic electrode. The magnetoresistance (MR) of the LSMO/Cu₃(HHTP)₂/Co organic spin valves (OSVs) reaches up to 25 % at 10 K. The MR can be retained with good film thickness adaptability varied from 30 to 100 nm and also at high temperatures (up to 200 K). This work demonstrates the first potential applications of 2D c‐MOFs in spintronics.     

Electrochemical Behavior of a Glassy Carbon Electrode Chemically Modified with Nickel Pentacyanonitrosylferrate in Presence of Sulfur Compounds

The glassy carbon electrode was modified with a nickel pentacyanonitrosylferrate film by electrodeposition of Ni and subsequent derivatization with NaPCNF. The film was characterized by XPS and electrochemical methods. Cyclic voltammetry of the NiPCNF onto the GC shows a redox couple (Fe^III/Fe^II) with E°′ of 538 mV (I_pa/I_pc around 1) and ΔE_p of 93 mV in 0.5 mol L^?1 KNO₃, with a diffusion‐controlled process. There was a decrease of anodic peak currents of the film in the presence of sulfide and 2‐propanethiol due to a precipitation reaction on the film surface by nucleophilic attack.     

Behaviors of H2TPP and CoTPPCl in Nafion® film and the catalytic activity for nitric oxide oxidation

The behavior of meso-tetraphenylporphyrin (H₂TPP) and its Co(III)-complex (CoTPPCl) in Nafion® film has been studied by cyclic voltammetry and visible spectroscopy. Buffer titration of H₄TPP²⁺ in the film showed only the dication–free-base equilibrium (H₄TPP²⁺H₂TPP + 2H⁺) and the apparent equilibrium constant, pK_3,4, was determined to be 4.12. Insertion of cobalt(III) into the H₂TPP core in the film has been realized at room temperature by immersion of H₂TPP-containing Nafion® film into CoCl₂ solution. The electrocatalytic activity of the resulting film toward NO oxidation at a glassy carbon (GC) electrode has been monitored in comparison with other Nafion® films doped with H₂TPP or free CoCl₂. A GC electrode coated with Nafion® film doped with CoTPPCl exhibited the highest catalytic activity, confirming the involvement of the Co site in a catalytic cycle of NO oxidation. In amperometric detection of NO in phosphate buffer solution at pH 7.4 this electrode demonstrated a linear response to the NO concentration increment. The detection limit at a signal-to-noise ratio of 3 was 1.2 nM.     

Synthesis,kinetics, and mechanism for adduct formation of tetraaza Schiff base cobalt(II) complexes with diorganotin(IV)dichlorides in dimethylformamide solvent

The kinetics and mechanism of the adduct formation of diorganotin(IV)dichlorides with Co(II) tetraaza Schiff base complexes, such as [Co(ampen)] {[N,N′‐ethylenebis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)]}, [Co(campen)] {[N,N′‐ethylenebis‐(5‐chloro‐o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)]}, and [Co(amaen)] {[N,N′‐ethylenebis‐(o‐amino‐α‐methylbenzylideneiminato)cobalt(II)]}, were studied spectrophotometrically. The kinetic parameters and the rate constant values show the following acceptor tendency trend for the diorganotin(IV)dichlorides: Ph₂SnCl₂> Me₂SnCl₂> Bu₂SnCl₂. Adducts have been separately synthesized and fully characterized by ¹¹⁹SnNMR, IR, UV–vis spectra, and elemental microanalysis (C,H,N) methods. The trend of the rate constants for the adduct formation of the cobalt complexes with a given tin acceptor decreases as follow: Co(amaen) > Co(ampen) > Co(campen). The linear plots of k_obs vs. the molar concentration of the diorganotin(IV)dichlorides, the high span of the second‐order rate constant k₂ values, and the large negative values of AS^≠ suggest an associative (A) mechanism for the acceptor–donor adduct formation. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 499–507, 2010     

Donor property of cobalt(II) Schiff base complexes toward triphenyltin(IV)‐chloride: A kinetic study

In this study, some cobalt(II)tetraaza Schiff base complexes were used as donors in coordinating to triphenyltin(IV)chloride as acceptors; the kinetics and mechanism of the adduct formation were studied spectrophotometrically. Co(II)tetraaza Schiff base complexes used were [Co(amaen)][N,N′‐ethylene‐bis‐(o‐amino‐α‐methylbenzylideneiminato)cobalt(II)] ( 1 ), [Co(appn)] [N,N′‐1,2‐propylene‐bis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)] ( 2 ), [Co(ampen)] [N,N′‐ethylene‐bis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt‐(II)] ( 3 ), [Co(cappn)][N,N′‐1,2‐proylene‐bis‐(5‐chloro‐o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)] ( 4 ), and [Co(campen)] [N,N′‐ethylene‐bis‐(5‐chloro‐o‐amino‐α‐phenylbenzylid‐eneiminato)cobalt(II)] ( 5 ). The reactivity trend of the complexes in interaction with triphenyltin(IV)chloride was Co(amaen) > Co(appn) > Co(ampen) > Co(cappn) > Co(campen). The linear plots of k_obs versus the molar concentration of the triphenyltin(IV)chloride, a high span of the second‐order rate constant k₂ values, and large negative values of ΔS^≠ and low ΔH^≠ values suggest an associative (A) mechanism for the acceptor–donor adduct formation. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 635–640, 2012     

Novel Membrane Potentiometric Thiocyanate Sensor Based on Tribenzyltin(IV) Dithiocarbamate

A novel PVC membrane ion‐selective electrode based on tribenzyltin(IV) dithiocarbamate [Sn(IV)–TBDTB] as neutral carrier was developed for thiocyanate (SCN^?) determination. The electrode exhibits a near‐Nernstian response for SCN^? with a slope of 62.8±2.0 mV per decade over a wide concentration range 1.0×10^?1–2.0×10^?6 mol L^?1 and a detection limit of 1.0×10^?6 mol L^?1 in MES–NaOH buffer, pH 6.0, at 25 °C. The electrode prepared with 1.5 wt.% Sn(IV)–TBDTB, 32.5 wt.% PVC and 66.0 wt.% 2‐nitrophenyloctyl ether (o‐NPOE) shows optimal response characteristics. Anti‐Hofmeister selectivity sequence for a series of anions shown by the electrode was as follows: SCN^?>Sal^?>I^?>ClO >phCOO^?>CH₃COO^?>Br^?>Cl^?>NO >NO >Citrate>SO₄^2?. The useful pH range for the electrode was found to be 3–7 with a response time 30–40 s. The electrode has been used for direct determination of thiocyanate in wastewater with satisfactory results.     

Carbon Paste Electrode Plated with Lead Film. Voltammetric Characteristics and Application in Adsorptive Stripping Voltammetry

A lead film plated in situ at a carbon paste support was tested as a novel, potential electrode for adsorptive stripping voltammetric determination of cobalt traces in an ammonia buffer solution. To show the practical applicability of the new electrode, a catalytic adsorptive Co system in a supporting electrolyte containing 0.1 M ammonia buffer, 5×10^?4 M nioxime and 0.25 M nitrite was selected and investigated as a model solution. Pb and Co ions were simultaneously accumulated in situ on the electrode surface: Pb ions electrochemically at ?1.3 V) and then at ?0.75 V, at which potential the Co(II)‐nioximate complex was also pre‐concentrated via adsorption. Instrumental parameters, such as the time of nucleation and formation of Pb film deposits, the time of accumulation of the Co‐nioxime complex at the PbF/CPE, and the procedures of electrode regeneration, were optimized to obtain good reproducibility and sensitivity of the Co response. The optimized procedure yields favorable and highly stable stripping responses with good precision (RSD=3% for a 5×10^?8 M Co) and good linearity (up to 5×10^?7 M, coefficient of determination, R=0.996). The detection limit was 4×10^?10 M Co (0.023 μg L^?1) for an accumulation time of 120 s. The method enables the determination of Co in the presence of high excesses of Ni or Zn. The voltammetric data were correlated with the structural characterization by scanning electron microscopy (SEM) and X‐ray fluorescence spectroscopy (XRF).     

Fabrication of Covalently Attached Multilayer Film Electrode Containing Iron Porphyrin and Its Electrocatalysis Toward Sulfite

Construction of a highly stable covalently attached multilayer film electrode containing iron porphyrin was achieved by UV irradiation of ionic self‐assembled multilayer films of diazo‐resins (DAR) and anionic Fe(III)tetrakis(p‐sulfonatophenyl)porphyrin (FeTSPP). The multilayer films had been characterized by UV, IR spectra and cyclic valtammetry. The electrocatalytic transformation of sulfite to SO₄^2? by the multilayer film electrode containing FeTSPP was investigated. In 0.1 M NH₄OH? NH₄Cl buffer solution (pH 8.74) and 0.1 M borate buffer solution (pH 9.18) the electrocatalytic oxidation of sulfite through the multilayer film electrode can be performed. However, in acetate buffer solution (pH 4.0) the electrocatalytic reduction of sulfite by the multilayer film electrode had also good activity. The modified electrode also exhibited a fast response and good stability.     

Catalytic Adsorptive Stripping Chronopotentiometry of Co(II)‐DMG‐Bromate System at an In Situ Plated Lead Film Electrode

A novel catalytic adsorptive stripping chronopotentiometric (CC‐CAdSCP) procedure for the determination of Co(II) traces was developed using a lead film electrode (PbFE). The PbFE was generated in situ on a glassy carbon support from a 0.1 M ammonia buffer containing 1×10^?5 M Pb(II), 6.5×10^?5 M DMG and the target metals. An addition of 0.2 M NaBrO₃ to the solution yielded an 11‐fold catalytic enhancement of chronopotentiometric response of the Co(II)‐DMG complex. The CC‐CAdSCP curves were well‐developed, sharp and reproducible (RSD 5.0 % for 5×10^?9 M Co(II)). The limit of detection for Co(II) for 210 s of accumulation time was 4×10^?10 M (0.024 µg L^?1). In addition, the elaborated method allowed the simultaneous quantification of Co(II) and Ni(II) simultaneously.     

Cobalt(II) Complexes with N‐Thioacylamidophosphates and 2,2′‐Bipyridyl and 1,10‐Phenathroline. Crystal Structures,Solution 1H NMR Spectral and Magnetic Properties

Structure and magnetic properties of N‐diisopropoxyphosphorylthiobenzamide PhC(S)‐N(H)‐P(O)(OiPr)₂ ( HL^I ) and N‐diisopropoxyphosphoryl‐N′‐phenylthiocarbamide PhN(H)‐C(S)‐N(H)‐P(O)(OiPr)₂ ( HL^II ) complexes with the Co^II cation of formulas [Co{PhC(S)‐N‐P(O)(OiPr)₂}₂] ( 1 ), [Co{PhN(H)‐C(S)‐N‐P(O)(OiPr)₂}₂] ( 2 ), [Co{PhC(S)‐N(H)‐P(O)(OiPr)₂}₂{PhC(S)‐N‐P(O)(OiPr)₂}₂] ( 1a ) and [Co{PhC(S)‐N‐P(O)(OiPr)₂}₂}(2,2′‐bipy)] ( 3 ), [Co{PhC(S)‐N‐P(O)(OiPr)₂}₂(1,10‐phen)] ( 4 ), [Co{PhN(H)‐C(S)‐N‐P(O)(OiPr)₂}₂(2,2′‐bipy)] ( 5 ), [Co{PhN(H)‐C(S)‐N‐P(O)(OiPr)₂}₂(1,10‐phen)] ( 6 ) were investigated. Paramagnetic shifts in the ¹H NMR spectrum were observed for high‐spin Co^II complexes with HL^I,II , incorporating the S‐C‐N‐P‐O chelate moiety and two aromatic chelate ligands. Investigation of the thermal dependence of the magnetic susceptibility has shown that the extended materials 1‐2 and 6 show ferromagnetic exchange between distorted tetrahedral ( 1 , 2 ) or octahedral ( 1a , 6 ) metal atoms whereas 3 and 5 show antiferromagnetic properties. Compound 4 behaves as a spin‐canted ferromagnet, an antiferromagnetic ordering taking place below a critical temperature, T_c = 115 K. Complexes 1 and 1a were investigated by single crystal X‐ray diffraction. The cobalt(II) atom in complex 1 resides a distorted tetrahedral O₂S₂ environment formed by the C=S sulfur atoms and the P=O oxygen atoms of two deprotonated ligands. Complex 1a has a tetragonal‐bipyramidal structure, Co(O^ax)₂(O^eq)₂(S^eq)₂, and two neutral ligand molecules are coordinated in the axial positions through the oxygen atoms of the P=O groups. The base of the bipyramid is formed by two anionic ligands in the typical 1,5‐O,S coordination mode. The ligands are in a trans configuration.     

纳米结构Ce掺杂PbO2膜电极的电化学沉积和性质

The effect of Ce(Ⅲ) on the morphology and structure of deposited film of lead dioxide was studied by cyclic voltammetry (CV), X-ray diffractometry (XRD) and scanning tunneling microscopy (STM). The results indicated that the Ce-doped PbO2 film consisted of a mixture of α- and β-phase of PbO2. Ce doping changed the size of PbO2 crystal grains and made the crystallite size on the electrode surface in the nanometer range. Owing to the formation of nanometer-structured grains, the specific surface areas and activity sites of the electrode surface were increased, hence the catalytic activity of Ce-doped PbO2 electrode was evidently higher than that of undoped PbO2 electrode.     

A Highly Selective Amperometric Hydrogen Peroxide Sensor Based on Silicomolybdate‐Doped‐Glutaraldehyde‐Cross‐Linked Poly‐L‐Lysine Film Modified Glassy Carbon Electrode

Silicomolybdate‐doped‐glutaraldehyde‐cross‐linked poly‐L ‐lysine (PLL‐GA‐SiMo) film modified glassy carbon electrode was prepared by means of electrostatically trapping the silicomolybdate anion in the cationic film. The PLL‐GA‐SiMo film was stable and the charge transport through the film was fast. The modified electrode shows excellent electrocatalytic activity towards hydrogen peroxide reduction with significant reduction of overpotential, however, not responded to potential interferrents such as dopamine, ascorbic acid and uric acid. This unique feature of PLL‐GA‐SiMo modified electrode allowed for the development of a highly selective method for the determination of H₂O₂ in the presence of interferents.     

Synthesis, crystal structures and magnetic properties of M(II)Cu(II) chains (M = Mn and Co) with sterically hindered alkyl-substituted phenyloxamate bridging ligands

A series of neutral oxamato‐bridged heterobimetallic chains of general formula [MCu(L^x)₂(S)₂] ? p S ? q H₂O [p=0–1, q=0–2.5; L¹=N‐2,6‐dimethylphenyloxamate, S=DMF with M=Mn ( 1 a ) and Co ( 1 b ); L²=N‐2,6‐diethylphenyloxamate, S=DMF with M=Mn ( 2 a ) and Co ( 2 b ) or S=DMSO with M=Mn ( 2 c ) and Co ( 2 d ); L³=N‐2,6‐diisopropylphenyloxamate, S=DMF with M=Mn ( 3 a ) and Co ( 3 b ) or S=DMSO with M=Mn ( 3 c ) and Co ( 3 d )] were prepared by treating the corresponding anionic oxamatocopper(II) complexes [Cu(L^x)₂]^2? (x=1–3) with M²⁺ cations (M=Mn and Co) in DMF or DMSO as the solvent. The single‐crystal X‐ray structures of 2 a and 3 a reveal the occurrence of well‐isolated, zigzag, oxamato‐bridged manganese(II)–copper(II) chains. The intrachain Cu ??? Mn distances across the oxamato bridge are 5.3761(7) and 5.4002(17) Å for 2 a and 3 a , respectively, whereas the shortest interchain Mn ??? Mn distances are 9.4475(16) and 8.1649(14) Å for 2 a and 3 a , respectively. All of these M^IICu^II chains (M=Mn and Co) exhibit 1D ferrimagnetic behaviour with moderately strong intrachain antiferromagnetic coupling between the square‐planar Cu^II and octahedral high‐spin M^II ions across the oxamato bridge [?J=31.4–35.2 and 33.4–44.8 cm^?1, respectively; H =∑_i?J S _M,i( S _Cu,i+ S _Cu,i?1)]. Only the Co^IICu^II chains show slow magnetic relaxation effects characteristic of single‐chain magnets (SCMs). Analysis of the magnetic relaxation dynamics of 3 d shows a thermally activated mechanism (Arrhenius law dependence) with values of the pre‐exponential factor (τ₀=2.6×10^?9 s) and activation energy (E_a=7.7 cm^?1) that are typical of SCMs. In contrast, two relaxation regimes are observed for 2 d in different temperature regions (τ₀=3.2×10^?10 s and E_a=24.7 cm^?1 for T<4.5 K and τ₀=3.2×10^?14 s and E_a=37.5 cm^?1 for T>4.5 K).     

Cobalt(II) Schiff Base/Large Mesoporous Carbon Composite Film Modified Electrode as Electrochemical Biosensor for Hydrogen Peroxide and Glucose

A simple method was developed to prepare a cobalt(II) Schiff base (Co(salen))/large mesoporous carbon (LMC) composite film. The structure and electrocatalytic performance of the Co(salen)/LMC film were investigated by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The Co(salen)/LMC film exhibits high electrocatalytic activity toward H₂O₂, such as low detection limit (8.5×10^?7 M) and wide linear concentration range (2.0×10^?6–8.9×10^?3 M). Furthermore, glucose oxidase (GOD) was self‐assembled on the surface of the Co(salen)/LMC film modified electrode. Determination of glucose in human blood serum with satisfying result was investigated by the resulting biosensor.     

A Selective Voltammetric Method for Uric Acid Detection at a Glassy Carbon Electrode Modified with Electrodeposited Film Containing DNA and Pt‐Fe(III) Nanocomposites

A novel biosensor by electrochemical codeposited Pt‐Fe(III) nanocomposites and DNA film was constructed and applied to the detection of uric acid (UA) in the presence of high concentration of ascorbic acid (AA). Based on its strong catalytic activity toward the oxidation of UA and AA, the modified electrode resolved the overlapping voltammetric response of UA and AA into two well‐defined peaks with a large anodic peak difference (ΔE_pa) of about 380mV. The catalytic peak current obtained from differential pulse voltammetry (DPV) was linearly dependent on the UA concentration from 3.8×10^?6 to 1.6×10^?4 M (r=0.9967) with coexistence of 5.0×10^?4 M AA. The detection limit was 1.8×10^?6 M (S/N=3) and the presence of 20 times higher concentration of AA did not interfere with the determination. The modified electrode shows good sensitivity, selectivity and stability.     

Growth of poly(3,4‐ethylenedioxythiophene) films prepared by base‐inhibited vapor phase polymerization

Transparent [90% transmittance at 550 nm at a sheet resistance (R_s) of 279 Ω sq^?1] poly(3,4‐ethylenedioxythiophene) (PEDOT) films with electrical conductivities up to 1354 S cm^?1 are prepared using base‐inhibited vapor phase polymerization at atmospheric pressure. The influence of reaction conditions, such as temperature and growth time, on the film formation is investigated. A simple and convenient two‐electrode method is used for the in situ measurement of resistance, enabling to investigate the growth mechanism of polymer films and the influence of different parameters (relative humidity and the amount of oxidant) on the film growth. Low humidity exerts a detrimental effect on film growth and conductivity. In situ R_s measurements suggest that a large structural change occurs upon washing the PEDOT‐oxidant film. © 2014 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2014 , 52, 561–571