Sensitive electrochemical detection of bisphenol A with chitosan and urchinlike MnO2 microsphere modified carbon ionic liquid electrode

In this article, a carbon ionic liquid electrode (CILE) was fabricated by using ionic liquid N-hexylpyridinium hexafluorophosphate as the binder and the modifier. Then urchinlike MnO₂ microsphere and chitosan (CTS) was further casted on the CILE surface step-by-step to get a modified electrode that was denoted as CTS/MnO₂/CILE. Cyclic voltammetric studies indicated that bisphenol A (BPA) exhibited a well-defined oxidation peak at 0.486 V in 22.83 g L^?1 pH 8.0 Britton?Robinson buffer solution, which was attributed to the electro-oxidation of BPA on the modified electrode. The presence of urchinlike MnO₂ microsphere on the electrode surface could increase the oxidation peak current (I_pa) greatly, which may be due to the larger surface area that could adsorb more BPA on the electrode surface. Electrochemical parameters of BPA on the modified electrode were calculated with the electron transfer coefficient (α) as 0.66 and the apparent heterogeneous electron transfer rate constant (ks) as 0.50 s^?1. Under the optimal conditions, a linear relationship between the I_pa of BPA and its concentration was obtained in the range from 1.37 × 10^–1 mg L^?1 to 182.6 mg L^?1 with the detection limit as 7.31 × 10^–3 mg L^?1 (3σ). The CTS/MnO₂/CILE was applied to the detection of BPA content in different kinds of samples with satisfactory results.     

A Photoelectrochemical Solar Cell Consisting of a Cadmium Sulfide Photoanode and a Ruthenium–2,2′‐Bipyridine Redox Shuttle in a Non‐aqueous Electrolyte

A photoelectrochemical (PEC) cell consisting of an n‐type CdS single‐crystal electrode and a Pt counter electrode with the ruthenium–2,2′‐bipyridine complex [Ru(bpy)₃]^2+/3+ as the redox shuttle in a non‐aqueous electrolyte was studied to obtain a higher open‐circuit voltage (V_OC) than the onset voltage for water splitting. A V_OC of 1.48 V and a short‐circuit current (I_SC) of 3.88 mA cm^?2 were obtained under irradiation by a 300 W Xe lamp with 420–800 nm visible light. This relatively high voltage was presumably due to the difference between the Fermi level of photo‐irradiated n‐type CdS and the redox potential of the Ru complex at the Pt electrode. The smooth redox reaction of the Ru complex with one‐electron transfer was thought to have contributed to the high V_OC and I_SC. The obtained V_OC was more than the onset voltage of water electrolysis for hydrogen and oxygen generation, suggesting prospects for application in water electrolysis.     

Bifunctional Ion‐Selective Electrode Based on C60‐Cryptand 22 for Silver and Iodine Ions

Fullerence C60‐cryptand 22 was prepared and successfully applied as the electric carrier in the PVC electrode membrane of a bifunctional ion‐selective electrode for cations, e.g., Ag⁺ ions as well as anions, e.g., I^? ions. The bifunctional ion‐selective electrode based on C60‐cryptand 22 can be applied as a Silver (Ag⁺) ion selective electrode with an internal electrode solution of 10^?3 M AgNO₃ in water (pH = 6.3), or as an Iodide (I^?) ion selective electrode with an acidic internal electrode solution of 10^?4 M KI_(aq) (pH = 2) in which the cryptand 22 is protonated, and the C60‐cryptand 22 is changed to C60‐Cryptand22–H⁺ and becomes an anionic electro‐carrier to absorb the I^? ion. The Ag⁺ ion selective electrode based on C60‐cryptand 22 gave a linear response with a near‐Nernstian slope (59.5 mV decade^?1) within the concentration range 10^?1‐10^?3 M Ag⁺_(aq). The Ag⁺ ion electrode exhibited comparatively good selectivity for silver ions, over other transition‐metal ions, alkali and alkaline earth metal ions. The Ag⁺ ion selective electrode with good stability and reproducibility was successfully used for the titration of Ag⁺_(aq) with Cl^? ions. The Iodide (I^?) Ion selective electrode based on protonated C60–cryptand22‐H⁺ also showed a linear response with a nearly Nernstian slope (58.5 mV decade^?1) within 10^?1 ‐ 10^?3 M I^? _(aq) and exhibited good selectivity for I^? ions and had small selectivity coefficients (10^?2–10^?3) for most of other anions, e.g., F^? , OH^?, CH₃COO^?, SO₄^2?, CO₃^2?, CrO₄^2?, Cr₂O₇^2? and PO₄^3? ions.     

Growth of aligned polypyrrole acicular nanorods and their application as Pt‐free semitransparent counter electrode in dye‐sensitized solar cell

Polypyrrole films on fluorine doped tin oxide (FTO)‐coated glass substrate were prepared in situ by placing FTO/glass substrates where pyrrole was polymerized by methyl orange‐ferric chloride complex. The atomic force microscopy image indicated growth of acicular nanorods of polypyrrole. These films exhibited catalytic activity towards I₃⁻/I⁻ redox couple and have been investigated for counter electrode application in dye‐sensitized solar cell (DSSC). The fabricated DSSC with N719 dye/TiO₂ as photoanode, and PPy/FTO as counter electrode shows ~1.7% efficiency.     

Surface modification of a reactive metal or alloy by polyaniline for electrooxidation of iodide

Generally, an inert metal such as platinum is used for studying electrooxidation reactions. As a non-platinum metal or alloy undergoes corrosion and oxidation, it is not useful for this purpose. In the present study, surface modification of non-platinum metals by coating electronically conducting polymers for electrooxidation reactions was investigated. Polyaniline (PANI) was electrochemically deposited on stainless steel (SS) substrate by potentiodynamic method. The oxidation of I⁻ was studied by cyclic voltammetry and amperometry experiments. The I⁻/I₂ reaction couple was found to be quasireversible on the PANI/SS electrode. The amperometry study, conducted under fast mass transport conditions, has provided linear relationship between current and concentration of I⁻. The data were analyzed and rate constant of the reaction was evaluated. Thus the oxidation of I⁻, which does not occur on bare SS electrode, was shown to occur through electron transfer mediated by polyaniline.     

Preparation and Electrochemical Behaviour of Silver Pentacyanonitrosylferrate Film Modified Glassy Carbon Electrode and Its Electrocatalytic Oxidation to L‐cysteine

A glassy carbon (GC) electrode modified with silver pentacyanonitrosylferrate (AgPCNF) film as a redox mediator was fabricated. Cyclic voltammetry was used to study the redox property of AgPCNF modified electrode. The modified electrode showed a well‐defined redox couple due to [Ag^IFe^III/II(CN)₅NO]^1‐/2‐system. The effects of scan rates, supporting electrolytes and solution pHs were studied on the electrochemical behavior of the modified electrode. The feasibility of using the AgPCNF modified electrode to measure L ‐cysteine was investigated. It showed an excellent electrocatalytic activity towards the oxidation of L ‐cysteine and the anodic currents were proportional to the L ‐cysteine concentration in the range of 0.1 μM to 20 μM, the linear regression equation is I_pa(μA) = ‐68.58 ‐ 5.78C_{L ‐cysteine} (μM), with a correlation coefficient 0.998 for N = 23. The detection limit was down to 3.5 × 10^‐8 M (three times the ratio of signal to noise).     

Selective Determination of Zn2+ Ion in Various Environmental,Biological and Medicinal Plant Samples Using a Novel Coated Graphite Electrode

Novel Zn²⁺ ion‐selective PVC based coated graphite electrodes were fabricated using the ionophores N‐((1H‐indol‐3‐yl)methylene)thiazol‐2‐amine (I₁), N‐((1H‐indol‐3‐yl)methyl)‐thiazol‐2‐amine (I₂) and 1‐((1H‐indol‐3‐yl)methylene)urea (I₃). Their potentiometric performance was examined in dependence of the addition of plasticizers and anion excluders and compared. It is found that the coated graphite electrode with the composition I₁:KTpClPB:o‐NPOE:PVC=9 : 1.5 : 51 : 38.5 is the best with respect to the wide working concentration range (4.2×10^?8–1.0×10^?1 mol L^?1), low detection limit (1.6×10^?8 mol L^?1) and wide pH range of 3.0–8.0. The proposed electrode was successfully applied to quantify Zn²⁺ in various environmental, biological and medicinal plant samples and used as indicator electrode.     

Fabrication of New Magnetic Nanoparticles (Fe3O4) Grafted Multiwall Carbon Nanotubes and Heterocyclic Compound Modified Electrode for Electrochemical Sensor

Magnetic Fe₃O₄ nanoparticles functionalized multiwalled carbon nanotubes (nano‐Fe₃O₄ MWNTs) were prepared for electrochemical sensors. 2‐amino‐5‐mercapto‐1,3,4‐thiadiazole was used as a connecter to form a network that connected nano‐Fe₃O₄ MWNTs to the Au electrode surface. Modified process of the electrode was studied with SEM, TEM and cyclic voltammetry. Cyclic voltammetry and amperometric i‐t curve were used to investigate characteristics of the obtained electrode. The sensor has been successfully used on the direct detection of catechol and showed excellent performances. The linear regression equation was I_pa(μA)=0.07763+0.16739 C (μmol/L); R=0.9993 and the detection limit was 5.38×10^?8 mol/L. The modified electrode showed good reproducibility and stability.     

The influence of the composition of CsCl-LiCl-YCl<Subscript>3</Subscript> melts on their acid properties at 973 K

The acid properties of CsCl-xLiCl and CsCl-LiCl + xYCl₃ melts were studied at 973 K by the potentiometric method with the use of a Pt(O₂)|ZrO₂(Y₂O₃) oxygen electrode. The acidity of these melts increased as x grew. The oxobasicity index values (pI _L) were estimated, they were 3.84 for 2CsCl-LiCl and 5.55 for 0.875(2CsCl + LiCl) + 0.125YCl₃ melts. The acid properties of mixed “alkali metal halide-rare-earth metal halide” melts were close to each other, and the presence of Li⁺ cations in such melts did not influence their pI _L values because of the leveling of their acid properties.     

TCO-free dye solar cells based on Ti back contact electrode by facile printing method

The back contact dye solar cells (BCDSCs), in which the TCO(Transparent Conductive oxide) is omitted, have a potential for use of intact low-cost general substrates such as glass, metal foil and papers. Herein, we introduce a facile manufacturing method of a Ti back contact electrode (Ti BCE) for the BCDSCs. We found that the polylinkers such as poly(butyl titanate) have a strong binding property to make Ti particles connect one with another. A porous Ti film, which consists of Ti particles of ≤ 10? size connected by a small amount of polylinkers, has an excellent low sheet resistance of 10 Ω sq^-1 for an efficient electron collection for DSCs. This Ti BCE can be prepared by using a facile printing method under normal ambient conditions. Conjugating the new back contact electrode technology with the traditional monolithic structure using the carbon counter electrode, we fabricated TCO-less DSCs. These four-layer structurered DSCs consist of a dye-adsorbed nanocrystalline TiO₂ film on a glass substrate, a porous Ti back contact layer, a ZrO₂ spacer layer and a carbon counter electrode in a layered structure. Under AM 1.5 G and 100 mWcm^?2 simulated sunlight illumination, the four-layer structurered DSCs with N719 dyes and I^-/I₃^-redox electrolytes achieved PCEs up to 5.21 %.     

Enhanced photoelectrochemical properties of visible light-responsive TiO2 photoanode for separate-type Pt-free photofuel cells by Rh3+ addition

Visible light-responsive TiO₂ (Vis-TiO₂) electrode has been applied for the Pt-free separate-type photofuel cell (SPFC) where two different electrolytes containing various biomass derivatives and a I₃ ^?/I^? redox solution were employed for the anode and cathode sides, respectively. This new SPFC exhibits good photoelectrochemical performance under simulated solar-light irradiation. It was found that the Rh³⁺ loading on Vis-TiO₂ electrode enhanced the photoelectrochemical performance of the SPFC through the increase in the visible light absorption as well as the increase in the electron conductivity of Vis-TiO₂ electrode.     

Poly(o-phenylenediamine)/MWNTs composite film as a hole conductor in solid-state dye-sensitized solar cells

All solid-state dye-sensitized solar cells were fabricated using in situ electrochemically polymerized poly(o-phenylenediamine)/MWNTs (PoPD/MWNTs) as a hole transport materiel. The electrochemical behaviors of PoPD/MWNTs indicated that the electron exchange efficiency improves obviously of PoPD after the addition of carbon nanotubes. The PoPD/MWNTs composite film was deposited on the dye anchored porous TiO₂ electrode and I–V characterization was performed under simulated AM 1.5 illumination. Fabricated devices for the PoPD/MWNT composites prepared in 0.1 g/L MWNTs showed a photoresponse with an open-circuit voltage V_OC of 479 mV and a short-circuit current density (I_SC) of 0.572 mA/cm² with the overall conversion efficiency of 0.13%, higher than those of the cell with only PoPD (i.e., I_SC = 0.275 mA/cm², V_OC = 462 mV, FF = 0.35, η = 0.04%). It is obvious that the introduction of MWNTs to PoPD composites could improve the cell performance.     

Chemical Speciation of Antimony(III and V) in Water by Adsorptive Cathodic Stripping Voltammetry Using the 4‐(2‐Thiazolylazo) – Resorcinol

A simple adsorptive cathodic stripping voltammetry method has been developed for antimony (III and V) speciation using 4‐(2‐thiazolylazo) – resorcinol (TAR). The methodology involves controlled preconcentration at pH 5, during which antimony(III) – TAR complex is adsorbed onto a hanging mercury drop electrode followed by measuring the cathodic peak current (I_p,c) at ?0.39 V versus Ag/AgCl electrode. The plot of I_p,c versus antimony(III) concentration was linear in the range 1.35×10^?9–9.53×10^?8 mol L^?1.The LOD and LOQ for Sb(III) were found 4.06×10^?10 and 1.35×10^?9 mol L^?1, respectively. Antimony(V) species after reduction to antimony(III) with Na₂SO₃ were also determined. Analysis of antimony in environment water samples was applied satisfactorily.     

Speciation of phytate ion in aqueous solution. Cadmium(II) interactions in aqueous NaCl at different ionic strengths

Interactions between myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate) (phytic acid) and cadmium(II) were studied by using potentiometry (at 25 °C with the ISE-H⁺ glass electrode) in different metal to ligand (Phy) ratios (1:1≤Cd²⁺:Phy≤4:1) in NaCl_aq at different ionic strengths (0.1≤I/mol L⁻¹≤1). Nine Cd_iH_jPhy^{(12−2i−j)−} species are formed with i=1 and 2 and 4≤j≤7; and trinuclear Cd₃H₄Phy²⁻. Dependence of complex formation constants on ionic strength was modeled by using Specific ion Interaction Theory (SIT) equations. Phytate and cadmium speciation are also dependent on the metal to ligand ratio. Stability of Cd_iH_jPhy^{(12−2i−j)−} species was modeled as a function of both the ligand protonation step (j) and the number of metal cations bound to phytate (i), and relationships found were used for the prediction of species other than those experimentally determined (mainly di- and tri-protonated complexes), allowing the possibility of modeling Phy and Cd(II) behavior in natural waters and biological fluids. A critical evaluation of phytate sequestering ability toward cadmium(II) has been made under several experimental conditions, and the determination of an empirical parameter has been proposed for an objective “quantification” of this ability. A thorough analysis of literature data on phytate–cadmium(II) complexes has been performed. Previous contributions to this series: [1–8]     

Transition‐Metal π‐Ligation of a Tetrahalodiborane

The reaction of tetraiododiborane (B₂I₄) with trans‐[Pt(BI₂)I(PCy₃)₂] gives rise to the diplatinum(II) complex [{(Cy₃P)(I₂B)Pt}₂(μ₂:η³:η³‐B₂I₄)], which is supported by a bridging diboranyl dianion ligand [B₂I₄]^2?. This complex is the first transition‐metal complex of a diboranyl dianion, as well as the first example of intact coordination of a B₂X₄ (X=halide) unit of any type to a metal center.     

A Systematic Investigation of Coinage Metal Carbonyl Complexes Stabilized by Fluorinated Alkoxy Aluminates

The reaction of Cu^I, Ag^I, and Au^I salts with carbon monoxide in the presence of weakly coordinating anions led to known and structurally unknown non‐classical coinage metal carbonyl complexes [M(CO)_n][A] (A=fluorinated alkoxy aluminates). The coinage metal carbonyl complexes [Cu(CO)_n(CH₂Cl₂)_m]⁺[A]^? (n=1, 3; m=4?n), [Au₂(CO)₂Cl]⁺[A]^?, [(OC)_nM(A)] (M=Cu: n=2; Ag: n=1, 2) as well as [(OC)₃Cu???ClAl(OR^F)₃] and [(OC)Au???ClAl(OR^F)₃] were analyzed with X‐ray diffraction and partially IR and Raman spectroscopy. In addition to these structures, crystallographic and spectroscopic evidence for the existence of the tetracarbonyl complex [Cu(CO)₄]⁺[Al(OR^F)₄]^? (R^F=C(CF₃)₃) is presented; its formation was analyzed with the help of theoretical investigations and Born–Fajans–Haber cycles. We discuss the limits of structure determinations by routine X‐ray diffraction methods with respect to the C? O bond lengths and apply the experimental CO stretching frequencies for the prediction of bond lengths within the carbonyl ligand based on a correlation with calculated data. Moreover, we provide a simple explanation for the reported, partly confusing and scattered CO stretching frequencies of [Cu^I(CO)_n] units.     

Organometallic Probe for the Electronics of Base‐Stabilized Group 11 Metal Cations

A number of trimetalloborides have been synthesized through the reactions of base‐stabilized coinage metal chlorides with a dimanganaborylene lithium salt in the hope of using this organometallic platform to compare and evaluate the electronics of these popular coinage metal fragments. The adducts of Cu^I, Ag^I, and Au^I ions, stabilized by tricyclohexylphosphine (PCy₃), N‐1,3‐bis(4‐methylphenyl)imidazol‐2‐ylidene (ITol), or 1‐(2,6‐diisopropylphenyl)‐3,3,5,5‐tetramethylpyrrolidin‐2‐ylidene (CAAC), with [{Cp(CO)₂Mn}₂B]^? were studied spectroscopically, structurally, and computationally. The geometries of the adducts fall into two classes, one symmetric and one asymmetric, each relying on the combined characteristics of both the metal and ligand. The energetic factors proposed as the causes of the structural differences were investigated by ETS‐NOCV (extended transition state‐natural orbitals for chemical valence) analysis, which showed the final geometry to be controlled by the competition between the tendency of the coinage metal to adopt a higher or lower coordination number and the willingness of the cationic fragment to participate in back‐bonding interactions.     

Bis[N,N′‐(2‐chlorobenzylidene)ethylenediamine‐κ2N,N′]copper(I) dichloridocuprate(I) acetonitrile solvate

The 1:1 adduct of N,N′‐bis(2‐chlorobenzylidene)ethylenediamine (cb₂en) with copper(I) chloride proves to be an ionic compound with Cu^I‐centred cations and anions, [Cu(C₁₆H₁₄Cl₂N₂)₂][CuCl₂]·CH₃CN. In the cation, the Cu^I atom has a flattened tetrahedral coordination geometry, with a small bite angle for the chelating ligands, which form a double‐helical arrangement around the metal centre. The anion is almost linear, as expected. The packing of the cations involves intermolecular π–π interactions, which lead to columns of translationally related cations along the shortest unit‐cell axis, with anions and solvent molecules in channels between them.     

Electroanalytical Studies of Chromone Based Ionophores for the Selective Determination of Arsenite Ion

Two chemosensors 4H‐1‐benzopyran‐3‐carboxaldehyde, 4‐oxo‐, 3‐(2‐phenylhydrazone), [I₁] and 4H‐1‐benzopyran‐3‐carboxaldehyde, 4‐oxo‐, 3‐[2‐(2,4‐dinitrophenyl)hydrazone], [I₂] with hydrazone‐NH group as binding site have been shown excellent selectivity for arsenite ion. It is confirmed by the UV‐vis titration that I₂ is more selective than I₁. The performance of the coated graphite electrode (CGE) was found to be better than polymeric membrane electrode (PME) in terms of linear range of 4.89×10^?7–1.0×10^?1 mol L^?1, low detection limit of 8.31×10^?8 mol L^?1 and short response time. The proposed sensors were also used to determine the arsenite ion in different water samples.     

The effects of polymer gel electrolyte composition on performance of quasi-solid-state dye-sensitized solar cells

Polymer gel electrolytes based on poly(acrylic acid)-poly(ethylene glycol) (PAA–PEG) hybrid have been prepared and applied to developed quasi-solid-state dye-sensitized solar cells (DSCs). PAA–PEG hybrid was synthesized by polymerization reaction. Quasi-solid-state DSCs were fabricated with synthesized PAA–PEG electrolyte. The effects of alkali iodides LiI, KI, and I₂ concentrations on liquid electrolyte absorbency and ionic conductivity of PAA–PEG were investigated. The evolution of the solar cell parameters with polymer gel electrolyte compositions was revealed. DSCs based on PAA–PEG with optimized KI/I₂ concentrations showed better performances than those with optimized LiI/I₂ concentrations. The electrochemical impedance spectroscopy technique was employed to examine the electron lifetime in the TiO₂ electrode and quantify charge transfer resistances at the TiO₂/dye/electrolyte interface and the counter electrode in the solar cells based on the PAA–PEG hybrid gels. A maximum conversion efficiency of 4.96% was obtained for DSCs using KI based quasi-solid electrolyte under 100 mW cm⁻². Our work suggests that KI can be the promising alkali metal iodide for improving the performance of PAA–PEG hybrid gel DSCs.