Electroactive Organic Compounds Research Articles

Organoclay-modified electrodes: preparation, characterization and recent electroanalytical applications

Amperometric sensors dedicated to the determination of pollutants and other compounds of interest face daily a great challenge: the development of sensitive, reproducible and low-cost devices allowing fast analyses. This review deals with the beneficial role and application of organoclays exploited as sensing materials in various fields of electroanalysis, for the past 15 years (period 2000–2014). After a description of different preparation methods leading to clay minerals chemically modified by organic compounds, the common methods used for their characterization are exposed; then, their application as electrode modifiers is described, covering several approaches that were developed to enhance either the sensitivity or the selectivity of the indexed organoclay-based sensors. Finally, a brief description of voltammetric methods frequently used for electroanalytical purposes is given, followed by an update of recent and salient results achieved for the detection of inorganic and organic electroactive compounds or ions.

Review—Advanced Carbon-Supported Organic Electrode Materials for Lithium (Sodium)-Ion Batteries

Electroactive organic compounds represent one of the most promising electrode materials for the next generation of green and sustainable lithium (sodium) ion batteries (LIBs/SIBs). However, most organic electrode materials are plagued by high solubility in organic electrolytes and poor electrical conductivity, which have severely impeded their practical applications. Among various strategies to improve their electrochemical performance, introducing conductive carbon into organic materials to form composite electrodes offers the possibility to simultaneously solve the two problems. In this paper, we provide an overview of recent development in the design, synthesis, and application of advanced carbon-supported organic electrode materials for LIBs/SIBs. In such systems, organic component mainly contributes to the charge storage, while carbon matrix facilitates the electron transfer and suppresses the dissolution of the active materials. We mainly focus on representative composites with carbon matrix of fibers, nanotubes (CNTs), graphene, and porous structures. We especially highlight the employment of CNTs and graphene as conductive carbon substrates for organic electrode materials due to their high conductivity, huge surface area, and excellent flexibility. The elegant design of organic-carbon composite should promote the practical applications of organic electrode materials for LIBs/SIBs.

Binding energy and work function of organic electrode materials phenanthraquinone, pyromellitic dianhydride and their derivatives adsorbed on graphene.

Electroactive organic compounds are a novel group of green cathode materials for rechargeable metal-ion batteries. However, the organic battery life is short because the organic compounds can be dissolved by nonaqueous electrolytes. Here a comparative investigation of phenanthraquinone (PQ), pyromellitic dianhydride (PMDA) and their derivatives, i.e., benzo[1,2-b:4,3-b']difuran-4,5-dione (BDFD), benzo[1,2-b:4,3-b']dithiophene-4,5-quinone (BDTQ), 3,8-phenanthroline-5,6-dione (PAD), pyromellitic dithioanhydride (PMDT), pyromellitic diimide (PMDI) and 1,4,5,8-anthracenetetrone (ATO), adsorbed on graphene is performed using a density functional theory (DFT) with a van der Waals (vdW) dispersion-correction. The computed results show a strong physisorption with the binding energies between 1.10 and 1.56 eV. A sequence of the calculated binding energies from weak to strong is found to be BDFD < BDTQ < PMDA ≤ PMDI < PMDT < PQ < PAD < ATO. The formation of stable organic molecule-graphene nanocomposites can prevent the dissolution of the eight organic compounds in nonaqueous electrolyte and hence improve cycling performance of batteries. In addition, the work functions for the nanocomposites are found to be strongly affected by the work function of each organic compound. To understand the DFT results, a novel simple expression is proposed to predict the work function of the nanocomposites from the interfacial dipole and the work functions of the isolated graphene nanosheet and organic molecules. The predicted work functions for the nanocomposites from the new equation agree quite well with the values calculated from the vdW dispersion-corrected DFT.

Electroactive Organic Compounds as Anode-Active Materials for Solar Rechargeable Redox Flow Battery in Dual-Phase Electrolytes

In order to achieve solar energy conversion and storage, a solar rechargeable redox flow battery in dual-phase electrolytes is presented in this work. In the battery, LISICON film is employed as membrane to separate liquid anode/cathode-active species, and organic compounds in aqueous electrolyte and LiI in organic electrolyte are employed as anolyte and catholyte, respectively. In particular, it is demonstrated from the cyclic voltammetry that quinoxaline and its derivatives show good electrochemical activity with suitable redox potentials in aqueous electrolyte. Correspondingly, the as-fabricated battery presents good solar rechargeable capability, subsequent discharge capability, and cycle stability, and thus indicates the feasible solar energy conversion and storage. Therefore, the organic compounds can be used as potential electroactive alternatives in anolyte for applications of the solar rechargeable flow battery.

Electrochemical Sensing and Biosensing Platform Based on Chemically Reduced Graphene Oxide

In this paper, the characterization and application of a chemically reduced graphene oxide modified glassy carbon (CR-GO/GC) electrode, a novel electrode system, for the preparation of electrochemical sensing and biosensing platform are proposed. Different kinds of important inorganic and organic electroactive compounds (i.e., probe molecule (potassium ferricyanide), free bases of DNA (guanine (G), adenine (A), thymine (T), and cytosine (C)), oxidase/dehydrogenase-related molecules (hydrogen peroxide (H2O2)/beta-nicotinamide adenine dinucleotide (NADH)), neurotransmitters (dopamine (DA)), and other biological molecules (ascorbic acid (AA), uric acid (UA), and acetaminophen (APAP)) were employed to study their electrochemical responses at the CR-GO/GC electrode, which shows more favorable electron transfer kinetics than graphite modified glassy carbon (graphite/GC) and glassy carbon (GC) electrodes. The greatly enhanced electrochemical reactivity of the four free bases of DNA at the CR-GO/GC electrode compared with that at graphite/GC and GC electrodes makes the CR-GO/GC electrode a better choice for the electrochemical biosensing of four DNA bases in both the single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) at physiological pH without a prehydrolysis step. This allows us to detect a single-nucleotide polymorphism (SNP) site for short oligomers with a particular sequence at the CR-GO/GC electrode without any hybridization or labeling processes in this work, suggesting the potential applications of CR-GO in the label-free electrochemical detection of DNA hybridization or DNA damage for further research. Based on the greatly enhanced electrochemical reactivity of H2O2 and NADH at the CR-GO/GC electrode, CR-GO/GC electrode-based bioelectrodes (in connection with glucose oxidase (GOD) and alcohol dehydrogenase (ADH)) show a better analytical performance for the detection of glucose and ethanol compared with graphite/GC- or GC-based bioelectrodes. By comparing the electrochemical performance of CR-GO with that of the conventional graphite and GC, we reveal that CR-GO with the nature of a single sheet showing favorable electrochemical activity should be a kind of more robust and advanced carbon electrode material which may hold great promise for electrochemical sensors and biosensors design.

Electrochemical Sensing Platform Based on the Highly Ordered Mesoporous Carbon−Fullerene System

In this paper, we report a novel all-carbon two-dimensionally ordered nanocomposite electrode system on the basis of the consideration of host-guest chemistry, which utilizes synergistic interactions between a nanostructured matrix of ordered mesoporous carbon (OMC) and an excellent electron acceptor of nanosized fullerene (C 60) to facilitate heterogeneous electron-transfer processes. The integration of OMC-C 60 by covalent interaction, especially its electrochemical applications for electrocatalysis, has not been explored thus far. Such integration may even appear to be counterintuitive because OMC and C 60 provide opposite electrochemical benefits in terms of facilitating heterogeneous electron-transfer processes. Nevertheless, the present work demonstrates the integration of OMC and C 60 can provide a remarkable synergistic augmentation of the current. To illuminate the concept, eight kinds of inorganic and organic electroactive compounds were employed to study the electrochemical response at an OMC-C 60 modified glassy carbon (OMC-C 60/GC) electrode for the first time, which shows more favorable electron-transfer kinetics than OMC/GC, carbon nanotube modified GC, C 60/GC, and GC electrodes. Such electrocatalytic behavior at OMC-C 60/GC electrode could be attributed to the unique physicochemical properties of OMC and C 60, especially the unusual host-guest synergy of OMC-C 60, which induced a substantial decrease in the overvoltage for NADH oxidation compared with GC electrode. The ability of OMC-C 60 to promote electron transfer not only suggests a new platform for the development of dehydrogenase-based bioelectrochemical devices but also indicates a potential of OMC-C 60 to be of a wide range of sensing applications because the electrocatalysis of different electroactive compounds at the OMC-C 60/GC electrode in this work should be a good model for constructing a novel and promising electrochemical sensing platform for further electrochemical detection of other biomolecules.

The characteristics of highly ordered mesoporous carbons as electrode material for electrochemical sensing as compared with carbon nanotubes

In this paper, the unique properties of highly ordered mesoporous carbons modified glassy carbon electrode (OMCs/GE) are illustrated from comparison with carbon nanotubes modified glassy carbon electrode (CNTs/GE) for the electrochemical sensing applications. Electrochemical behaviors of eight kinds of inorganic and organic electroactive compounds were studied at OMCs/GE, which shows more favorable electron transfer kinetics than that at CNTs/GE. Especially, OMCs/GE exhibits remarkably strong and stable electrocatalytic response toward NADH compared with CNTs/GE. The ability of OMCs to promote electron transfer not only provides a new platform for the development of dehydrogenase-based bioelectrochemical devices, but also indicates a potential of OMCs in a wide range of sensing applications. OMCs prepared are the novel carbon electrode materials, exhibiting more favorable electrochemical reactivity than CNTs for the wide electrochemical sensing applications without pretreatments, while purification or end-opening processing was usually required in case of CNTs.

Voltammetric behavior of ethopropazine and the influence of sodium dodecylsulfate on its accumulation on gold electrodes

Surfactants are sometimes used to improve the accumulation of some electroactive organic compounds, but anionic surfactants have seldom been utilized for such a purpose yet. In this paper, the influence of the anionic surfactant sodium dodecylsulfate (SDS) on the accumulation of ethopropazine (EPZ) at a polycrystalline gold electrode has been studied. EPZ exhibits an anodic peak at about 0.67 V (vs. SCE) and a shoulder in pH 3.5 citric acid–biphthalate buffer solution. In the absence of SDS, the peak is small and ill defined, but it becomes high and well shaped when SDS is added. This results from the adsorption of EPZ in the SDS membrane, which forms spontaneously on the gold electrode surface. For both cases EPZ shows the same electrode reaction mechanism, which is similar to that of promethazine (PMZ). The influence of other factors, such as pH value, variety and concentration of buffers, other surfactants, accumulation potential and time etc has been discussed. It was found that only the anionic surfactants had an enhancement effect on the EPZ accumulation. Also, the solution should be acidic or neutral so as to maintain the interaction due to its electrostatic nature. The optimum SDS concentration for EPZ accumulation is about 0.1 mM regardless of whether or not an accumulation potential is adopted. When all the experiment conditions are optimized, the peak current of the anodic peak changes linearly with the concentration of EPZ over the range 0.4–4 μM, and is thus of analytical significance.

Carbon nanotube-modified glassy carbon electrode for adsorptive stripping voltammetric detection of ultratrace levels of 2,4,6-trinitrotoluene

Glassy carbon electrodes modified with multi-wall carbon nanotubes (MWCNT) have been shown extremely useful for highly sensitive adsorptive stripping voltammetric measurements of the 2,4,6-trinitrotoluene (TNT) explosive down to the sub-μg/l level. Operational parameters have been optimized and the stripping voltammetric performance has been studied using linear sweep scans. The adsorptive stripping response is highly linear over the 100–1000 μg/l TNT range examined (2 min deposition), with a detection limit of 0.6 μg/l (10 min deposition) and good precision (RSD=3.6%, n=16). These findings open the door for a widespread use of CNT-modified electrodes in adsorptive stripping voltammetry (AdSV) of important compounds that do not exhibit surface-active properties at conventional electrodes and for using stripping voltammetry for investigating the interactions of electroactive organic compounds with CNT.

Interactions of low-energy electrons with organic electroactive compounds

The electron energy loss spectra, the dependence of elastic and inelastic scattering on projectile electron energy, excitation functions and fluorescence spectra under scattering of monoenergetic electrons with tunable energies from 0 to 50 eV at an angle of 90°, for electroactive compounds – N, N ′-diphenyl- N, N ′-bis(3-methyl-phenyl)-1,1 ′-biphenyl-4,4 ′-diamine (TPD) and tris(8-hydroxyquinolinato)aluminum (Alq 3) – in the gas phase and in thin solid amorphous film are presented. The energy dependence of elastic and inelastic scattering cross-sections for Alq 3 is essentially different from Born-approximation data. The behaviour of both solid and gas phase EELS is similar. The nature of electron movement in both phases is the same.

The effect of Pseudomonas fluorescens strains varying in psoverdine production on the soil redox status

The ability of a pyoverdine producing Pseudomonas fluorescens strain C7R12 to act as an effector of soil redox status was determined using as control an isogenic mutant which does not produce pyoverdine (strain PL1). During the period of observation (68 h), the redox potential of the soil inoculated with strain C7R12 was higher than that of the soil inoculated with the mutant PLI. The soil pH at 68 h decreased in the following order: control soil >inoculated soil with strain PL1> inoculated soil with strain C7R12 (p < 0.05). The redox capacity of soil-EDTA extracts was measured after 68 h with differential pulse polarography. The quantity of electroactive compounds within the potentials range studied (+300 to -900 mV) differed among treatments. The soil inoculated with strain C7R12 exhibited a lower concentration of electroactive compounds in lower potentials (+30 mV to -330 mV), and a higher concentration in higher potentials (around +170 mV) than the soil inoculated with mutant strain PL1. This explains the difference observed in redox potential values between inoculated soils. In the noninoculated soil, the redox potential was higher, and the redox capacity lower (within the potentials range studied) than in the inoculated soils. Taking into account that the soil extract used excludes the presence of inorganic ions in the soil solution, we conclude that the effect of strain C7R12 on the soil redox status would involve more complex mechanisms than the sequestering of iron by the pyoverdine, probably associated with the presence of organic electroactive compounds.

Electrochemically generated chemiluminescence of tris(2,2′-bipyridine)ruthenium(ii), tris(1,10-phenathroline)ruthenium(ii) and tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(ii) complexes

The electrochemically generated chemiluminescence (ECL) of the title complexes with four series of electroactive organic compounds Q in 0.1 M (C2H5)4NPF6 acetonitrile solutions has been studied using a triple-potential-step technique. The yields of the formation of the excited *RuL32+ ion produced by the electron transfer reaction of RuL3+ with aromatic amine or 2,3,7,8-tetramehoxythianthrene radical cations and by the reaction of RuL33+ with quinone or nitroaromatic radical anions as well as with N-methylpyridinium radicals have been determined. A reaction scheme describing generation of the excited *RuL32+ has been comparatively discussed with that for the quenching reactions with conclusion that spin conversion between two spin forms 3[RuL33+/+⋯Q−/+] and 1[RuL33+/+⋯Q−/+] of an activated complex play a crucial role in both electron transfer processes.

Free energy dependence on tris(2,2′-bipyridine)ruthenium(II) electrochemiluminescence efficiency

The electrogenerated chemiluminescence (ECL) of Ru(bypy) 3 2+ with four series of electroactive organic compounds in 0.1 M (C 2H 5) 4NPF 6 acetonitrile solutions has been studied using a triple-potential-step technique. The yields of the formation of the excited ∗ Ru(bypy) 3 2+ ion produced by the electron-transfer reaction of Ru(bypy) 3 + with aromatic amine or 2,3,7,8-tetramehoxythianthrene radical cations and by the reaction of Ru(bypy) 3 3+ with quinone or nitroaromatic radical anions and N-methylpyridinium radicals have been determined. The obtained yields for the excited ∗ Ru(bypy) 3 2+ ion formation have been compared with the predicted ones according to the oxidative or reductive ∗ Ru(bypy) 3 2+ quenching data.

Screen-printed voltammetric sensor for TNT

Screen-printed carbon electrodes have been developed as disposable voltammetric sensors for 2,4,6-trinitrotoluene (TNT). Thick-film electrodes based on various conventional and modified inks have been compared for this task. The operation is based on placing the selected thick-film carbon sensor in the non-deaerated/quiescent sample and using a fast (<1 s) and sensitive square-wave voltammetric scan. Different experimental variables have been optimized to yield a detection limit of 200 ppb TNT and a wide linear range. The high selectivity, demonstrated in assays of various untreated environmental samples, is attributed to the facts that the reducible nitro group is rare in nature and that most electroactive organic compounds require higher potentials. The new single-use sensor strips should facilitate the on-site environmental screening of TNT.

SPE composite microdisk electrodes used in organic electrosynthesis

An SPE composite microdisk electrode is made by pressing a microdisk electrode on a piece of SPE membrane. It has a small ohmic drop and shows good reproducibility and some well-developed cyclic voltammograms and steady-state polarization curves are obtained. The electrochemical behavior of nitrobenzene and ferrocene at different microelectrode¦SPE membrane interfaces is investigated. It is found that electroactive compounds in the vicinity of the interface diffuse from the bulk solution to the electrode surface through the SPE membrane. This technique is suitable for investigating the electrochemical behavior of gases at the metal¦SPE interface or organic electroactive compounds poorly soluble in aqueous solution without addition of supporting electrolyte.

Computerized flow constant-current stripping analysis for some electroactive organic compounds: Application to the determination of erythromycin in urine

The possibility of determining various electroactive organic compounds, e.g., erythromycin and riboflavin, by adsorptive preconcentration at constant potential on a mercury-coated carbon-fibre electrode in a flow system prior to stripping with a reductive constant current, is demonstrated. The advantages of measuring the electrode potential vs. time instead of current vs. electrode potential during stripping, the possibility of operating with non-deoxygenated solutions, the increased linear calibration range is in the multiple scanning mode, and the possibility of using the technique for detection in liquid chromatography, are discussed. An analytical procedure for the determination of erythromycin at the 10 −6 M level in urine after extraction with diethyl ether is described.

Effect of long-distance electron transfer on chemiluminescence efficiencies

The electrogenerated chemiluminescence (ecl) of Mo/sub 6/Cl/sub 14//sup 2 -/ with three series of structurally and electronically related electroactive organic compounds in acetonitrile has been investigated. The yields for the formation of the electronically excited Mo/sub 6/Cl/sub 14//sup -/ ion produced by the electron-transfer reaction of Mo/sub 6/Cl/sub 14//sup 3 -/ with aromatic amine radical cations (A+) and by the reaction of Mo/sub 6/Cl/sub 14//sup -/ with nitroaromatic radical anions (D/sup -/) and pyridinium radicals (D) have been measured over a wide potential range by simply varying the reduction potential of the electroactive organic reagent. The dependence of the formation yield of Mo/sub 6/Cl/sub 14//sup 2 -/*, phi/sub es/, on the driving force of the annihilation reaction is similar for the three series, phi/sub es/ is immeasurable (< 10/sup -6/) for reactions with free energies positive of a threshold value. Over a narrow free energy range just negative of threshold, phi/sub es/ rapidly increases. And with increasing exergonicity of the electron-transfer reaction, phi/sub es/ asymptotically approaches a limiting value less than unity (phi/sub es//sup lim/(Mo/sub 6/Cl/sub 14//sup -//D/sup -/) = 0.013 +/- 0.001; phi/sub es//sup lim/(Mo/sub 6/Cl/sub 14//sup -//D) = 0.079 +/- 0.008; phi/sub es//sup lim/(Mo/sub 6/Cl/sub 14//sup 3 -//A/supmore » +/) = 0.132 +/- 0.006). Analysis of these excited-state production yields by Marcus theory suggests that unit efficiencies for excited-state production are circumvented by long-distance electron transfer.« less

Simultaneous determination of concentration, diffusion coefficient and number of electrons for electroactive species by combining suitable electroanalytical measurements

The electroanalytical method described for the simultaneous determination of concentration, the number of electrons involved in the redox process and diffusion coefficient is based on evaluation of the ratios between the currents recorded for the analyte and for an easily standardized reference species dissolved in the same medium. Three different electroanalytical techniques are used in which the currents exhibit, for two techniques at least, different dependences on both the diffusion coefficient and electron number. The approach is applicable to diffusion-controlled processes, regardless of the degree of reversibility involved. Reliability tests with electroactive organic compounds dissolved in dimethyl sulphoxide show that both accuracy and precision are within 10% depending on the chosen combination of techniques.

Adsorptive stripping voltammetry of electroactive organic compounds

Adsorptive stripping voltammetry at a hanging mercury drop electrode is described for various polarographically active compounds. Diazepam, nitrazepam, papaverine and aromatic nitro compounds can be determined at concentrations of 1 × 10 −9–1 × 10 −6 M with errors of 5–7%. The effects of changing accumulation potentials and times are considered. Interference by other surface-active agents may be removed by prior molecular exclusion chromatography.

Computerized potentiometric stripping analysis for the determination of cadmium, lead, copper and zinc in biological materials

Two different types of tinned mussels and a bovine liver reference sample have been analyzed for Zn, Cd, Pb and Cu by means of computerized potentiometric stripping analysis and atomic absorption spectrometry. The samples were digested by two different procedures, one employing nitric acid only and the other employing nitric and perchloric acids. It is shown that computerized stripping analysis can be used in samples containing high concentrations of electroactive organic nitro compounds, without sample deoxygenation.