Synthesis, Characterization and Antimicrobial Properties of Oligomer and Monomer/Oligomer–Metal Complexes of 2-[(Pyridine-3-yl-methylene)amino]phenol

Oligo-2-[(pyridine-3-yl-methylene)amino]phenol (2-PMAP) is synthesized by the oxidative polycondensation (OP) in aqueous alkaline medium using air as oxidant. At optimum reaction conditions, the yield of products is 71%. The structures of the monomer and oligomer were confirmed by FT-IR, UV–Vis, ¹H-NMR, ¹³C-NMR and elemental analysis. Characterization was made by thermogravimetric analysis-differential thermal analysis (TGA-DTA), size exclusion chromatography (SEC) and solubility. The ¹H-NMR and ¹³C-NMR data show that polymerization proceeds by C–C and C–O coupling of the ortho and para positions (–OH group and oxyphenylene group) of 2-[(pyridine-3-yl-methylene)amino]phenol. The molecular weight distribution of the product was determined by SEC. The number-average molecular weight (M _n ), weight-average molecular weight (M _w ) and polydispersity index (PDI) of O-2-PMAP are 7150, 8000 g mol⁻¹ and 1.119 for air oxidant, respectively. Thermal analysis results of O-2-PMAP indicate stability against thermal decomposition. Thermal analyses of 2-PMAP, 2-PMAP-Cd, 2-PMAP-Co, 2-PMAP-Cu, 2-PMAP-Zn, O-2-PMAP, O-2-PMAP-Cd, O-2-PMAP-Co, O-2-PMAP-Cu and O-2-PMAP-Zn monomer/oligomer–metal complexes were investigated under a N₂ atmosphere between 15 and 1000 °C. Antibacterial and antifungal activity of the synthesized compounds was examined against selected bacteria and fungi.     

Electrosynthesis and properties of poly(3,4-ethylenedioxythiophene) films functionalized with titanocene dichloride complex

Synthesis of a titanocene dichloride derivative functionalized with 3,4-etylenedioxythiophene group, Tc1EDOT (Cl₂TiCpC₅H₄(CH₂) (3,4-ethylenedioxythiophene)) has been described. Redox behavior of the monomer in tetrahydrofuran (THF), dichloromethane (DCM) and acetonitrile (AN) at different scan rates has been discussed in terms of different ability of these solvents to coordination with the reduced titanocene (Tc) complex and the solvation of Cl⁻ anions. Electrooxidation of Tc1EDOT to get a conducting polymer film with immobilized titanocene dichloride centers and electrochemical properties of its polymer matrix in background acetonitrile solution have been compared with those of non-substituted PEDOT and PEDOT-methanol derivative (PEDOTMet), to elucidate the effect of substituents both on polymerization and redox potentials of the matrix. STM and AFM images of p(Tc1EDOT) films obtained with potentiodynamic and potentiostatic regimes are compared to illustrate that the films deposited at constant potential are better ordered and more compact than those obtained by cyclic voltammetry. A comparison of the cyclic voltammograms of p(Tc1EDOT) and poly(titanocene-propyl-pyrrole) (p(Tc3Py)) films in 0.1 TBAPF₆ in THF has shown that the electroactivity of the polymer matrix of p(Tc1EDOT) is extended to more negative potentials in comparison to that of p(Tc3Py). This results in the anodic shift of redox potential of Tc centers immobilized in p(Tc1EDOT) film with respect to that of the centers fixed in p(Tc3Py).     

Characterization and conversion determination of stable PEDOT latex nanoparticles synthesized by emulsion polymerization

In this research, poly(3,4-ethylenedioxythiophene) (PEDOT) latex nanoparticles with good colloidal stability were prepared by emulsion polymerization and the conversions of EDOT were determined. Two kinds of oxidants, Iron(III) p-toluenesulfonate Fe(OTs)₃ and hydrogen peroxide H₂O₂, were introduced to decrease the use of iron salt and therefore reduce the particle coagulation. The ferrous ions (Fe²⁺) produced during the polymerization would be re-oxidized back to the reactive ferric ions (Fe³⁺) with the help of H₂O₂. This cyclic oxidation-reduction process resulted in the sustained regeneration of Fe³⁺ ions and led to a higher conversion. A dark blue PEDOT latex with long-term dispersion stability was obtained when Fe(OTs)₃ and H₂O₂ were added in sequence. The results obtained from dynamic light scattering and TEM measurements showed that the sizes of nanoparticles were around 100 nm. To determine the conversion of EDOT, two methods (gravimetric analysis and UV-visible method) were used and compared. For the first time, the UV-visible method was established to quantitatively determine the conversion of EDOT monomer. From the measurement, the conversion of EDOT in this system was determined as 74-75%. The PEDOT film prepared by drying the latex solution had conductivity up to 6.3 S/cm.     

Anodic deposition of hydrous ruthenium oxide for supercapaciors: Effects of the AcO concentration, plating temperature, and oxide loading

Effects of the sodium acetate (NaCH₃COO, denoted as NaAcO) concentration, plating temperature, and oxide loading on the pseudocapacitive characteristics of hydrous ruthenium oxide (denoted as RuO₂·xH₂O) films anodically plated from aqueous RuCl₃·xH₂O media were systematically investigated in this work. The electrochemical behavior of RuO₂·xH₂O with annealing in air at 200 °C for 2 h is approximately independent of the NaAcO concentration and plating temperature although a negative shift in the onset and peak potentials of deposition with rising the plating temperature is found. The morphologies and adhesion of RuO₂·xH₂O deposits strongly depend on the deposition rate which is obviously influenced by varying the above two deposition variables. The specific capacitance of RuO₂·xH₂O is monotonously decreased from 760 to 505 F g⁻¹ when the oxide loading is gradually increased from 0.34 to 1.0 mg cm⁻², due to the longer pathways of both electrons and protons during the redox transitions. The XRD and Raman spectroscopic analyses reveal the extremely localized crystalline nature of as-deposited RuO₂·xH₂O. All RuO₂·xH₂O deposits show the ideal pseudocapacitive characteristics, definitely illustrating the merits of RuO₂·xH₂O prepared by anodic deposition without considering the advantages of its simplicity, one-step, reliability, low cost, and versatility for electrode preparation.     

The solubility of selenate-AFt (3CaO·Al2O3·3CaSeO4·37.5H2O) and selenate-AFm (3CaO·Al2O3·CaSeO4·xH2O)

The Se(VI)-analogues of ettringite and monosulfate, selenate-AFt (3CaO·Al₂O₃·3CaSeO₄·37.5H₂O), and selenate-AFm (3CaO·Al₂O₃·CaSeO₄·xH₂O) were synthesised and characterised by bulk chemical analysis and X-ray diffraction. Their solubility products were determined from a series of batch and resuspension experiments conducted at 25 °C. For selenate-AFt suspensions, the pH varied between 11.37 and 11.61, and a solubility product, log K_so=61.29±0.60 (I=0 M), was determined for the reaction 3CaO·Al₂O₃·3CaSeO₄·37.5H₂O+12 H⁺⇔6Ca²⁺+2Al³⁺+3SeO₄²⁻+43.5H₂O. Selenate-AFm synthesis resulted in the uptake of Na, which was leached during equilibration and resuspension. For the pH range of 11.75 to 11.90, a solubility product, log K_so=73.40±0.22 (I=0 M), was determined for the reaction 3CaO·Al₂O₃·CaSeO₄·xH₂O+12 H⁺⇔4Ca²⁺+2Al³⁺+SeO₄²⁻+(x+6)H₂O. Thermodynamic modelling suggested that both selenate-AFt and selenate-AFm are stable in the cementitious matrix; and that in a cement limited in sulfate, selenate concentration may be limited by selenate-AFm to below the millimolar range above pH 12.     

Thermal Behavior of M +B5O6(OH)4 · 2H2O (M + = K, Rb, Cs) and Polymorphic Transformations of CsB5O8

Phase transformations (dehydration, amorphization, crystallization, polymorphic transitions) and thermal expansion of M ⁺B₅O₆(OH)₄ · 2H₂O (M ⁺ = K, Rb, Cs) compounds and the polymorphic transformations of the CsB₅O₈ compound are investigated using the methods of glass crystallization, thermal X-ray diffraction, and differential thermal analysis (DTA). It is shown that the dehydration of RbB₅O₆(OH)₄ · 2H₂O and CsB₅O₆(OH)₄ · 2H₂O, like KB₅O₆(OH)₄ · 2H₂O, proceeds in two stages. After the first stage of the dehydration (with a loss of three water molecules), all three compounds transform into the amorphous state. At the second stage, the fourth water molecule leaves the amorphous phase. At temperatures above the glass transition point, anhydrous pentaborates MB₅O₈ (M = K, Rb, Cs) crystallize and subsequently undergo polymorphic transformations.     

Hydrothermal synthesis and electrochemical capacitance of RuO2·xH2O loaded on benzenesulfonic functionalized MWCNTs

Amorphous RuO₂·xH₂O was well coated on the benzenesulfonic functionalized multi-wall carbon nanotubes (f-MWCNTs) successfully via hydrothermal method. The decorated benzenesulfonic groups served as a bifunctional role both for solubilizing and dispersing MWCNTs into aqueous solution and for tethering Ru³⁺ precursor to facilitate the following uniform chemical deposition of RuO₂·xH₂O. The electrochemical performance of RuO₂/f-MWCNTs and utilization of RuO₂·xH₂O were evidenced by cyclic voltammetry and galvanostatic charge/discharge tests. The specific capacitance of 1143 Fg⁻¹ for RuO₂·xH₂O was obtained from RuO₂/f-MWCNTs with 32 wt.% RuO₂·xH₂O, which was much higher than that of just 798 Fg⁻¹ for the RuO₂/p-MWCNTs. Even though the RuO₂·xH₂O loading increases to 45 wt.%, the utilization of RuO₂·xH₂O still possesses as high as 844.4 Fg⁻¹, indicating a good energy capacity in the case of high loading.     

Corrosion Mitigation of Mild Steel by New Rare Earth Cinnamate Compounds

Corrosion rate measurements based on weight loss (i.e., mild steel immersed for seven days in 0.01 M NaCl) and linear polarization resistance (LPR) techniques have shown that even low concentrations (200 ppm) of cerium and lanthanum cinnamates are able to significantly inhibit corrosion. Of all the compounds investigated in this work Ce(4-methoxycinnamate)₃· 2 H₂O and La(4-methoxycinnamate)₃· 2 H₂O compounds exhibited the greatest inhibition and, in comparison with the component inhibitors, a synergy was clearly observed. The mechanism of corrosion inhibition was investigated using cyclic potentiodynamic polarization (CPP) measurements. The results suggest that La(4-nitrocinnamate)₃· 2 H₂O and Ce(4-methoxycinnamate)₃· 2 H₂O behave as mixed inhibitors and improve the resistance of steel against localized attack.     

A novel (3,4,8)-connected 3D topology framework based on [Gd2(bpdc)3(H2O)3] second building units

A new 3D coordination polymer {[Gd₂(bpdc)₃(H₂O)₃]·H₂O}_n(1) has been isolated from the reaction of 2,2′-bipyridine-4,4′-dicarboxylic acid (H₂bpdc) and Gd(III) salts under hydrothermal conditions. Single-crystal X-ray diffraction study shows that compound 1 is constructed from Gd₂-based second building units (SBUs) [Gd₂(bpdc)₃(H₂O)₃] and displays a 3D (3,4,8)-connected net with (4²·6)(3²·4²·5²)(3²·4⁵·5⁴·6¹¹·7⁶) topology. A thermogravimetric analysis of 1 shows a high thermal stability. The magnetic behavior of 1 reveals a weak antiferromagnetic interaction between Gd(III) ions.     

Study of Fe/Fe ratio in thin films of carbonate or sulphate green rusts obtained by potentiostatic electrosynthesis

Thin films of carbonate or sulphate green rusts were synthesised from potentiostatic oxidation of solutions containing ferrous species and bicarbonate or sulphate ions at slightly alkaline pHs and ambient temperature. The thin films were characterised by means of electrochemical quartz crystal microbalance, scanning electron microscopy, X-ray diffraction and infrared reflection-absorption spectroscopy. The composition of carbonate or sulphate green rusts was studied through chemical titration, inductively coupled plasma-optical emission spectroscopy (ICP-OES) and gravimetry and is as follows:

[Fe^II_(2R)Fe^III₂(OH)_{(4R−2R′+6)}(H₂O)_(2R′−2)]^2R′+·[R′CO₃,(2R-{3 or 4}R′ + 2)·H₂O]^2R′− and [Fe^II_(2R)Fe^III₂(OH)_{(4R−2R″+6)}(H₂O)_(2R″−2)]^2R″+·[R″SO₄,(4R − 4R′ + 4)·H₂O]^2R″−     

Effects of substrates on the capacitive performance of RuOx·nH2O and activated carbon-RuOx electrodes for supercapacitors

The electrochemical energy storage and delivery on the electrodes composed of hydrous ruthenium oxide (RuO_x·nH₂O) or activated carbon-hydrous ruthenium oxide (AC-RuO_x) composites are found to strongly depend on the substrate employed. The contact resistance at the active material-graphite interface is much lower than that at the active material-stainless steel (SS) mesh interface. Thin films of gold plus RuO_x·nH₂O deposited on SS meshes (RuO_x/Au/SS) are found to greatly improve the poor contact between SS meshes and electrode materials. The maximum specific capacitance (C_S,RuOx) of RuO_x·nH₂O, 1580 F g⁻¹ (measured at 1 mV s⁻¹), very close to the theoretic value, was obtained from an AC-RuO_x/RuO_x/Au/SS electrode with 10 wt.% sol-gel-derived RuO_x·nH₂O annealed in air at 200 °C for 2 h. The highly electrochemical reversibility, high-power characteristics, good stability, and improved frequency response of this AC-RuO_x/RuO_x/Au/SS electrode demonstrate its promising application potential in supercapacitors. The ultrahigh specific capacitance of RuO_x·nH₂O probably results from the uniform size distribution of RuO_x·nH₂O nanoparticles, ranged from 1.5 to 3 nm which is clearly observed from the high-resolution transmission electron microscopy (HRTEM).     

Textural and pseudocapacitive characteristics of sol-gel derived RuO2·xH2O: Hydrothermal annealing vs. annealing in air

Hydrous ruthenium dioxide (RuO₂·xH₂O) prepared in a modified sol-gel process was subjected to annealing in air and water at various temperatures for supercapacitor applications. The textural and pseudocapacitive characteristics of RuO₂·xH₂O annealed in air and water were systematically compared to show the benefits of annealing in water (denoted as hydrothermal annealing). An important concept that hydrothermal annealing effectively restricts condensation of hydroxyl groups within nanoparticles, inhibits crystal growth, and maintains high water content of RuO₂·xH₂O is demonstrated in this work. The unique textural characteristics of hydrothermally annealed RuO₂·xH₂O are attributable to the high-pressured, water-enriched surroundings which restrain coalescence of RuO₂·xH₂O nanocrystallites. The crystalline, hydrous nature of hydrothermally annealed RuO₂·xH₂O favors the utilization of active species in addition to a merit of minor dependence of specific capacitance on the scan rate of CV for pseudocapacitors. As a result, RuO₂·xH₂O with hydrothermal annealing at 225 °C for 24 h exhibits 16 wt.% water, an average particle size of about 7 nm, and specific capacitance of ca. 390 F g⁻¹.     

Electrochemical characteristics and structural changes of molybdenum trioxide hydrates as cathode materials for lithium batteries

Several characteristics of MoO₃·2H₂O and MoO₃·H₂O, such as thermal behaviour and conductivity and the electrochemical behaviour and structural changes associated with discharge and charge have been investigated. The suitability of these substances as new cathode materials for non-aqueous lithium batteries has been assessed. MoO₃·H₂O, having only one coordinated water molecule, showed a discharge capacity of about 400 Ah kg^–1 of acid weight and a discharge potential around 2.5 V vs Li/Li⁺. This capacity was much higher than the 280 Ah kg^–1 of anhydrous MoO₃.MoO₃·H₂O showed good charge-discharge cyclic behaviour at a capacity below l e^–/Mo while keeping the original layered lattice on cycling. In addition, the crystal system of MoO₃·H₂O was found to be changed from a monoclinic system to orthorhombic with lattice parameters ofa=0.5285 nm,b=1.0824 nm,c=0.5237 nm on discharge to 0.5 e^–/Mo.This paper was originally presented at the Fall 1987 Meeting of the Electrochemical Society, Inc. held at Honolulu, Hawaii (Proceedings of the Symposium on Primary and Secondary Ambient Temperature Batteries, PV88-6, p. 484–493 (1987).     

Hydrothermal synthesis of binary Ru-Ti oxides with excellent performances for supercapacitors

Hydrous, crystalline, binary (Ru-Ti)O₂·nH₂O with compositions equal to the ratios of metallic ions in the precursor solutions are successfully synthesized by a mild hydrothermal process. The maximum utilization of RuO₂·nH₂O (ca. 793 F/g) occurs at the composition of 60 M% TiO₂·nH₂O although phase separation is clearly found for this TiO₂-enriched binary oxides. The nano-structured architecture with a high BET surface area (ca. 253 m²/g) of the hydrothermal-derived (Ru-Ti)O₂·nH₂O with annealing at 200 °C favors the physical adsorption of water and maintains a high water content which is novel and never found before. Due to this novel nanostructure, the annealed (Ru-Ti)O₂·nH₂O synthesized by means of the hydrothermal process exhibits excellent performances (i.e., high utilization of RuO₂, high power property, and long cycle life) for supercapacitors.     

Electrochemical capacitance of nanoporous hydrous RuO2 templated by anionic surfactant

The nanoporous RuO₂·3.38H₂O was synthesized with a surfactant template using sodium dodecyl sulfate. The surface area of the material amounted to 220 m² g⁻¹ while the maximum specific capacitance obtained was 870 Fg⁻¹ at a scan rate of 10 mV s⁻¹. The specific capacitance of nanoporous RuO₂·3.38H₂O electrode exhibits enhancement, compared with other porous RuO₂ materials synthesized by different methods. The nanoporous RuO₂·3.38H₂O is a very promising material for high performance capacitance.     

Single crystal nanobelts of V3O7·H2O: A lithium intercalation host with a large capacity

In this study, single crystal V₃O₇·H₂O nanobelts were successfully synthesized using a simple hydrothermal route, in which templates or catalysts were absent. The synthesized V₃O₇·H₂O nanobelts are highly crystalline and have lengths up to several tens of micrometers. The width and thickness of the nanobelts are found to be about 30-50 and 30 nm, respectively. A lithium battery using V₃O₇·H₂O nanobelts as the positive electrode exhibits a high initial discharge capacity of 409 mAh g⁻¹, corresponding to the formation of Li_xV₃O₇·H₂O (x = 4.32). Such a high degree of electrochemical performance is attributed to the intrinsic properties of the single-crystalline V₃O₇·H₂O nanobelts.     

Carbonate and sulphate green rusts—Mechanisms of oxidation and reduction

The oxidation and reduction of carbonate, GR(CO₃), and sulphate, GR(SO₄), green rusts (GR) have been studied through electrochemical techniques, electrochemical quartz crystal microbalance (EQCM), FTIR, XRD and SEM. The used samples were made of thin films electrodeposited on gold substrate. The results from the present work, from our previous studies and from literature were compiled in order to establish a general scheme for the formation and transformation pathways involving carbonate or sulphate green rusts. Depending on experimental conditions, two routes of redox transformations occur. The first one corresponds to reaction via solution and leads to the formation of ferric products such as goethite or lepidocrocite (oxidation) or to the release of Fe^II ions into the solution (reduction) with soluble Fe^II-Fe^III complexes acting as intermediate species. The second way is solid-state reaction that involve conversion of lattice Fe²⁺ into Fe³⁺ and deprotonation of OH groups in octahedra sheets (solid-state oxidation) or conversion of lattice Fe³⁺ into Fe²⁺ and protonation of OH groups (solid-state reduction). The solid-state oxidation implies the complete transformation of GR(CO₃) or GR(SO₄) to ferric oxyhydroxycarbonate exGRc-Fe(III) or ferric oxyhydroxysulphate exGRs-Fe(III), for which the following formulas can be proposed, Fe^III₆(OH)_(12−2y)(O)_(2+y)(H₂O)_(y)(CO₃) or Fe^III₆(OH)_(12−2z)(O)_(2+z)(H₂O)_(6+z)(SO₄) with 0 ≤ y or z ≤ 2. The solid-state reduction gives ferrous hydroxycarbonate exGRc-Fe(II) or ferrous hydroxysulphate exGRs-Fe(II), which may have the following chemical formulas, [Fe^II₆(OH)₁₀(H₂O)₂]·[CO₃, 2H₂O] or [Fe^II₆(OH)₁₀(H₂O)₂]·[SO₄, 8H₂O].     

Study of vanadium(IV) species and corresponding electrochemical performance in concentrated sulfuric acid media

The vanadium(IV) ion is found to form the [VO(SO₄)(H₂O)₄]·H₂O complex, as well as the dimer, [VO(H₂O)₃]₂(μ-SO₄)₂, in concentrated H₂SO₄ media. Their formation mechanisms were investigated by UV–Visible spectroscopy (UV–Vis), Raman spectroscopy, X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). UV–Vis spectroscopy study showed that [VO(SO₄)(H₂O)₄]·H₂O concentration in H₂SO₄ solution was proportional to concentrations of VO²⁺ and SO₄²⁻. The increased deviation from the near centrosymmetry of the octahedral complexes is due to the replacement of an equatorial water oxygen in [VO(H₂O)₅]SO₄ by a sulfate oxygen in [VO(SO₄)(H₂O)₄]·H₂O. The dimer shows symmetrical structure, which correlates very well with non-activity in UV–Vis spectroscopic analysis. Structural information on both vanadium(IV) species can be confirmed by Raman and XRD measurements of crystals from the supersaturated solution of VOSO₄ in 1 M, 6 M and 12 M sulfuric acid. A solution of vanadium(IV) (0.05 M) in 12 M H₂SO₄, in which the vanadium(IV) species is [VO(H₂O)₃]₂(μ-SO₄)₂, exhibits a reversible redox behavior near 1.14 V (vs. SCE) on the carbon paper electrode.     

The Copper (II) Complexes of Phenyl-2 Pyridyl Ketone and the Triple Complexes Obtained by Adding Ethylenediamine

Copper salts of low pH (1.8–2.5) combine with phenyl-2-pyridyl ketone to form a ketone complex [(Py–CO–C₆H₅)₂Cu]²⁺. An electrically uncharged complex is obtained at pH > 9 [(Py–C(OH)(C₆H₅)O^?)₂Cu]⁰, liberating two protons from two molecules of the ligand. The stability constant of this complex is β = 16.05. By mixing the copper salts (except the halide) containing this ligand with ethylenediamine, a charged triple complex is obtained at pH < 7 [Py–C(OH)(C₆H₅) O–Cu–NH₂C₂H₄NH₃⁺]²⁺. At pH > 9.5, an uncharged triple complex is obtained: {[(Py–C(OH)(C₆H₅)O^?)₂Cu}₂ · NH₂C₂H₄NH₂}⁰. The copper halide salts produce only an uncharged triple complex; the halide ions are coordinated with the copper atoms. All of these complexes in their solid state, are bi- or polynuclear. As a result, they are magnetically subnormal.     

Graphene nanosheets-tungsten oxides composite for supercapacitor electrode

Graphene nanosheets-tungsten oxides (tungsten oxide/tungsten oxide hydrate mixture) (GNS-W) composite was successfully synthesized using a facile approach. WO₃/WO₃·H₂O mixtures were deposited on the graphene nanosheets (GNS) to form the GNS-W composite. The GNS-W composite was characterized by X-ray diffraction (XRD), Raman spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The as-prepared GNS-W composite was directly fabricated into a supercapacitor electrode for potential energy storage application, and electrochemically tested by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The GNS-W composite electrode exhibits a better electrochemical performance than that of the WO₃/WO₃·H₂O mixtures electrode. A high specific capacitance of about 143.6 F g⁻¹ at a current density of 0.1 A g⁻¹ for the GNS-W composite delivers significant improvement than that for the WO₃/WO₃·H₂O mixtures and GNS electrodes. The impedance studies also suggest that the GNS-W composite electrode shows the lower resistance and high conductivity due to the good interaction between the graphene nanosheets and the WO₃/WO₃·H₂O mixtures. The good electrochemical performance for the GNS-W composite may be attributed to the interaction between the WO₃/WO₃·H₂O mixtures and the edges of graphene nanosheets, which increases the ion diffusion rate as well as the conductivity.