Ion-selective electrodes in potentiometric titrations; a new method for processing and evaluating titration data.

A new method to convert the potential of an ion-selective electrode to concentration or activity in potentiometric titration is proposed. The advantage of this method is that the electrode standard potential and the slope of the calibration curve do not have to be known. Instead two activities on the titration curve have to be estimated e.

Electro-catalytic oxidation of hemicelluloses at the Au electrode.

The recently reported electro-catalytic reaction mechanism for the oxidation of cellulose is proposed to work also for the electro-oxidation of other polysaccharides (e.g. hemicelluloses).

Electrocatalytic oxidation of cellulose at a gold electrode.

The electrochemical properties of cellulose dissolved in NaOH solution at a Au surface were investigated by cyclic voltammetry, FTIR spectroscopy, the electrochemical quartz crystal microbalance technique, and electrochemical impedance spectroscopy. The reaction products were characterized by SEM, TEM, and FTIR and NMR spectroscopy. The results imply that cellulose is irreversibly oxidized.

Solid-contact ion-selective electrodes with highly selective thioamide derivatives of p-tert-butylcalix[4]arene for the determination of lead(II) in environmental samples.

Thioamide derivatives of p-tert-butylcalix[4]arene were used as ionophores in the development of solid-contact ion-selective electrodes based on conducting polymer poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT/PSS) which was synthesized by electrodeposition on the glassy carbon electrodes. The typical ion-selective membranes with optionally two different plasticizers [bis(2-ethylhexyl)sebacate (DOS) and 2-nitrophenyl octyl ether (NPOE)] were investigated. The potentiometric selectivity coefficients were determined by separate solution method (SSM) for Pb(2+) over Cu(2+), Cd(2+), Ca(2+), Na(+), and K(+).

Measuring the concentration of carboxylic acid groups in torrefied spruce wood.

Torrefaction is moderate thermal treatment (∼200-300°C) to improve the energy density, handling and storage properties of biomass fuels. In biomass, carboxylic sites are partially responsible for its hygroscopic. These sites are degraded to varying extents during torrefaction.

Studying electronic transport in polyazulene-ionic liquid systems using infrared vibrational spectroscopy.

This paper presents an in situ spectroelectrochemical characterization of polyazulene (PAz) and PAz-C(60) composite films using Fourier Transform Infrared Attenuated Total Reflection (FTIR-ATR) spectroscopy. In situ FTIR-ATR spectra were recorded simultaneously as the films were charged and discharged electrochemically. The aim was to clarify how the use of ILs and the addition of C(60) affected the electronic transport and structural changes occurring in PAz during electrochemical charging.

Electrochemical determination of NADH and ethanol based on ionic liquid-functionalized graphene.

It is firstly reported that low-potential NADH detection and biosensing for ethanol are achieved at an ionic liquid-functionalized graphene (IL-graphene) modified electrode. A substantial decrease (440 mV) in the overvoltage of the NADH oxidation was observed using IL-graphene/chitosan coating, with oxidation starting at ca. 0 V (vs.

Graphene/AuNPs/chitosan nanocomposites film for glucose biosensing.

A novel glucose biosensor based on immobilization of glucose oxidase in thin films of chitosan containing nanocomposites of graphene and gold nanoparticles (AuNPs) at a gold electrode was developed. The resulting graphene/AuNPs/chitosan composites film exhibited good electrocatalytical activity toward H(2)O(2) and O(2). The wide linear response to H(2)O(2) ranging from 0.

One-step synthesis of graphene/SnO2 nanocomposites and its application in electrochemical supercapacitors.

A one-step method was developed to fabricate conductive graphene/SnO2 (GS) nanocomposites in acidic solution. Graphite oxides were reduced by SnCl2 to graphene sheets in the presence of HCl and urea. The reducing process was accompanied by generation of SnO2 nanoparticles.

Water-soluble graphene covalently functionalized by biocompatible poly-L-lysine.

Graphene sheets functionalized covalently with biocompatible poly-l-lysine (PLL) were first synthesized in an alkaline solution. PLL-functionalized graphene is water-soluble and biocompatible, which makes it a novel material promising for biological applications. Graphene sheets played an important role as connectors to assemble these active amino groups of poly-l-lysine, which provided a very biocompatible environment for further functionalization, such as attaching bioactive molecules.

Direct electrochemistry of glucose oxidase and biosensing for glucose based on carbon nanotubes@SnO(2)-Au composite.

Multiwalled carbon nanotubes@SnO(2)-Au (MWCNTs@SnO(2)-Au) composite was synthesized by a chemical route. The structure and composition of the MWCNTs@SnO(2)-Au composite were confirmed by means of transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Due to the good electrocatalytic property of MWCNTs@SnO(2)-Au composite, a glucose biosensor was constructed by absorbing glucose oxidase (GOD) on the hybrid material.

Direct electrochemistry of glucose oxidase and biosensing for glucose based on graphene.

We first reported that polyvinylpyrrolidone-protected graphene was dispersed well in water and had good electrochemical reduction toward O(2) and H(2)O(2). With glucose oxidase (GOD) as an enzyme model, we constructed a novel polyvinylpyrrolidone-protected graphene/polyethylenimine-functionalized ionic liquid/GOD electrochemical biosensor, which achieved the direct electron transfer of GOD, maintained its bioactivity and showed potential application for the fabrication of novel glucose biosensors with linear glucose response up to 14 mM.

Influence of anionic additive on Hg(2+) interference on Ag(+)-ISEs based on [2.2.2]p,p,p-cyclophane as neutral carrier.

The influence of the anionic additive on the Hg(2+) interference on Ag(+)-ion-selective electrodes (Ag(+)-ISEs) based on [2.2.2]p,p,p-cyclophane as pi-coordinating neutral carrier was studied by potentiometric measurements.

Small-volume radial flow cell for all-solid-state ion-selective electrodes.

A flow cell with a radial distribution of four all-solid-state ion selective electrodes (ISEs), or alternatively three ISEs and one reference electrode, was designed and optimized for mass production. The radial distribution of the electrodes reduces the cell volume and is expected to minimize cross-contamination between different electrodes. Two different cell prototypes were developed and tested for all-solid-state K(+)-ISEs based on a solvent polymeric ion-selective membrane (ISM) and a conducting polymer, poly(3,4-ethylenedioxythiophene), as solid internal contact.

Solid-contact ion-selective electrodes for aromatic cations based on pi-coordinating soft carriers.

Ion-selective electrodes (ISEs) based on pi-coordinating carriers were prepared and investigated as potentiometric sensors for aromatic cations, using N-methylpyridinium as a model aromatic cation. Derivatives of tetraphenylborate were studied as charged carriers in plasticized poly(vinyl chloride) membranes. Furthermore, neutral compounds containing pi-coordinating anthryl groups were studied as neutral carriers.

The nature of the charge carriers in polyazulene as studied by in situ electron spin resonance-UV-visible-near-infrared spectroscopy.

In situ spectroelectrochemistry is of high importance for the characterization of doping reactions in pi-conjugated polymers. In this paper we present the results of simultaneous ESR and UV-vis-NIR measurements performed in situ during electrochemical p- and n-doping of polyazulene (PAz). In previous studies on p-doping of PAz the assignment of the optical absorption bands to specific charge carriers have been somewhat controversial, therefore the aim of this study is to clarify the nature of the doping-induced charge carriers and their corresponding optical absorption bands by in situ ESR-UV-vis-NIR spectroelectrochemistry.

In situ resonance Raman spectroscopy of polyazulene on aluminum.

Polyazulene (PAz) has been electrochemically deposited on different electrode substrates. The films were characterized with Raman and UV-vis spectroscopy. The spectroelectrochemical studies were performed in situ during p- and n-doping (electrochemical oxidation and reduction, respectively).

Memory effect in an ionic liquid matrix containing single-walled carbon nanotubes and polystyrene.

We report the use of an ionic liquid (IL) gel matrix containing a blend of single-walled carbon nanotubes (SWNTs) and polystyrene (PS) as a memory device. SWNTs and PS beads were mixed in a room-temperature IL, 1-butyl-3-methyl-hexafluorophosphate ([BMIM][PF(6)]). The composite gel was sandwiched between a bottom ITO glass and a top aluminium electrode.

Applications of ionic liquids in electrochemical sensors.

Ionic liquids (ILs) are molten salts with the melting point close to or below room temperature. They are composed of two asymmetrical ions of opposite charges that only loosely fit together (usually bulky organic cations and smaller anions). The good solvating properties, high conductivity, non-volatility, low toxicity, large electrochemical window (i.

Potassium-selective electrodes with stable and geometrically well-defined internal solid contact based on nanoparticles of polyaniline and plasticized poly(vinyl chloride).

Solid contact potassium-selective electrodes with the internal ion-to-electron transduction layer composed of plasticized poly(vinyl chloride) (PVC) and 2-20% (m/m) of polyaniline (PANI) nanoparticles, with the mean particle size of 8 nm, have been studied in this paper. UV-vis measurements in pH buffer solutions between pH 0 and 12 show that the electrically conducting emeraldine salt (ES) form of PANI has exceptionally good pH stability. Membranes of PANI nanoparticles were mainly in the ES form even at pH 12, in contrast to electrochemically prepared PANI(Cl) films, which are converted completely to the nonconducting form already at pH 6.

Pi-dimer of an aniline dimer: an ESR-UV-vis spectroelectrochemical study.

It is shown for the first time that the most important intermediate formed during aniline polymerization, the p-aminodiphenylamine, forms a pi-dimer under oxidation at room temperature in acidified organic solvents that are used in electropolymerization. N-Phenylquinonediimine, which is generally assumed to be formed under oxidation, is only formed in basic solutions and in ionic liquids. Most of the mechanistic studies reported so far take the formation of N-phenylquinonediimine under consideration, although it is not consistent with the UV-vis spectra measured during oxidation of p-aminodiphenylamine.

Application of raman spectroscopy and sequential injection analysis for pH measurements with water dispersion of polyaniline nanoparticles.

A novel method for pH measurements between pH 7.5 and 10.4 is reported in this paper.

Potentiometric measurements in sequential injection analysis lab-on-valve (SIA-LOV) flow-system.

Advantages of using sequential injection analysis lab-on-valve (SIA-LOV) in potentiometric measurements are studied with Ca(2+) sensitive solid-contact ion-selective electrodes (SC-ISE) and pH electrode based on polyaniline (PANI). Experiments show that Ca(2+)-SC-ISE requires a stopped flow mode to be used in order to get longer equilibration time. On the other hand, PANI based pH electrode gives better results under flow conditions.