Remarkable Electrochemical Responses of Ferrocene/NaY Zeolite Composite modified Electrode Based on Hydrophobic Ionic Liquid

The ferrocene/NaY zeolite composites (Fc/NaY) are introduced on the surface of a glassy carbon electrode together with the hydrophobic ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆). The modified electrode thus constructed exhibits a pair of reversible redox peaks corresponding to ferrocene. Additionally the peak separation remains almost constant (58–75 mV) and the value of the ratio i_pa/i_pc is close to 1 for scan rates in the range from 10 to 1000 mV s^?1. The effects of the scan rate, aqueous supporting electrolytes, hydrophobic ionic liquid and the contents of ferrocene encapsulated by electrochemistry are investigated. The extrazeolite electron transfer process is discussed. Furthermore, the Fc/NaY/IL‐modified electrode shows good mediation towards oxidation of ascorbic acid, dopamine, hydroquinone, and catechol.     

Reaktionsverhalten verschiedener Carbodiimide mit Ferrocen‐1, 1'‐dicarbonsäure

Reaction Behaviour of Several Carbodiimides with 1, 1'‐Ferrocenedicarboxylic Acid 1, 1'‐bis‐(1, 3‐dicyclohexylureidocarbonyl)‐ferrocene ( 1 ), 1, 1'‐bis‐(1, 3‐diisopropylureidocarbonyl)‐ferrocene ( 2 ) and ferrocene‐1, 1'‐bis‐N‐p‐tolylcarboxamide ( 6 ) were synthesized by melting down 1, 1'‐ferrocenedicarboxylic acid ( 7 ) together with N, N'‐dicyclohexylcarbodiimide (DCC), N, N'‐diisopropylcarbodiimide (DIC) or N, N'‐di‐p‐tolylcarbodiimide ( 8 ), respectively, without application of any solvent in a short space of time. Substance 1 , 2 , 1, 1'‐bis‐(1‐ethyl‐3‐tert‐butylureidocarbonyl)‐ferrocene ( 3 ), 1‐(1‐tert‐butyl‐3‐ethylureidocarbonyl)‐1'‐(1‐ethyl‐3‐tert‐butylureidocarbonyl)‐ferrocene ( 4 ) and 1, 1'‐bis‐(1‐tert‐butyl‐3‐ethylureidocarbonyl)‐ferrocene ( 5 ) were obtained in good yield by reacting 7 DCC, DIC, or N‐tert‐butyl‐N'‐ethylcarbodiimide ( 9 ), respectively, with in ethyl acetate for weeks. Transannular 1, 1'‐ferrocenedicarboxylic anhydride was not detectable or isolable in these reactions. All new compounds were characterized by ¹H‐NMR, ¹³C‐NMR, IR, MS and elementar analysis. In the case of 1 a single crystal structure analysis was made.     

Determination of Sulfide by Hematoxylin Multiwalled Carbon Nanotubes Modified Carbon Paste Electrode

This study investigates a new approach for the amperometric determination of sulfide using a hematoxylin multiwalled carbon nanotubes modified carbon paste electrode (HM‐MWCNTs/CPE). The experimental results show that HM‐MWCNTs/CPE significantly enhances the electrocatalytic activity towards sulfide oxidation. Cyclic voltammetric studies show that the peak potential of sulfide shifted from +400 mV at unmodified CPE to +175 mV at HM‐MWCNTs/CPE. The currents obtained from amperometric measurements at optimum conditions were linearly correlated with the concentration of sulfide. The calibration curve was obtained for sulfide concentrations in the range of 0.5–150×10^?6 mol L^?1. The detection limit was found to be 0.2×10^?6 mol L^?1 for the amperometric method. The proposed method was successfully applied to a river water sample in Pardubice, Czech Republic.     

Synthesis and characterisation of water soluble ferrocenes: Molecular tuning of redox potentials

A range of novel water-soluble alkylated ferrocene sulfonate compounds are reported. Mono- and di-sulfonation on a series of alkyl ferrocenes produced 1,1′-dimethyl ferrocene sulfonate, 1,1′-dimethyl ferrocene disulfonate, 1,1′-diethyl ferrocene sulfonate, 1,1′-diethyl ferrocene disulfonate, t-butyl ferrocene sulfonate, t-butyl ferrocene disulfonate, ethyl ferrocene sulfonate, ethyl ferrocene disulfonate, n-butyl ferrocene sulfonate and n-butyl ferrocene disulfonate. All compounds were characterized by NMR spectroscopy, UV/Vis spectroscopy and electrochemical analysis. ¹H and ¹³C NMR studies have revealed the formation of several isomers with sulfonation occurring on positions α and β to the alkyl substituent or on the unsubstituted cyclopentadienyl ring. Variation of the alkyl group allowed the isomeric pattern to be tuned such that the final products followed either electronic or steric control. Cyclic voltammetry of the resulting products showed that the redox potential of the iron centre can be easily manipulated by changing the substituents on the cyclopentadienyl rings. This result has significant implications in the future development of homogenous redox mediators for sensing applications.     

Electrocatalytic Oxidation of Formaldehyde on Copper Oxide Nano-crystalline Modified Glassy Carbon Electrode

This research found a cheap and efficient catalyst for electrooxidation of formaldehyde (HCHO). A CuO nano‐crystalline modified glassy carbon electrode (GCE) was fabricated and had an excellent electrocatalytic activity towards the oxidation of HCHO. Both the effect of potential scan rate and the effect of HCHO concentration on the electrocatalytic oxidation performance of the electrode were investigated. The amperometric current response of the electrode was proportional to HCHO concentration in the range of 1.0 µmol·L^?1–10.0 mmol·L^?1 with a detection limit (s/n=3) of 0.25 µmol·L^?1. The electrode was stable, showing the CuO nano‐crystlline is promising for applications in fuel cells and electrochemical sensors.     

Imine Gels Based on Ferrocene and Porphyrin and Their Electrocatalytic Property

A series of porphyrin‐based imine gels have been synthesized via dynamic covalent gelation between 5,10,15,20‐tetra(4‐aminophenyl)‐21H,23H‐porphyrin (H₂TAPP) derivatives and various aldehyde compounds. The porphyrin‐ferrocene imine gels based on MTAPP (M=H₂, Ni²⁺, Co²⁺, Pd²⁺ and Zn²⁺) and ferrocene‐1,1′‐dicarbaldehyde (NA) display efficient HER, OER and ORR activities in alkaline media. Among the gels, CoTAPP‐NA shows an HER current density of 10 mA cm^?2 at low overpotential of 470 mV and small Tafel slope of 110 mV decade^?1 in alkaline media. CoTAPP‐NA also exhibits OER catalytic activity with low overpotential (416 mV for 10 mA cm^?2). CoTAPP‐NA shows ability in overall water splitting in alkaline media. In addition, CoTAPP‐NA exhibits onset potential (E_p) of 0.95 V and half‐wave potential (E_1/2) of 0.84 V in 1.0 mol L^?1 KOH solution for oxygen reduction. Moreover, the gel catalyst shows good stability.     

The Kinetics of Ferrocene Volatilisation from an Ionic Liquid

The volatilisation of ferrocene (Fc), dissolved in the ionic liquid N‐butyl‐N‐methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C₄mpyrr][NTf₂], to the gas phase has been indirectly monitored by cyclic voltammetry and chronoamperometry. Simulation of the observed trends in concentration with time using a simple model allowed quantification of the process. Volatilisation of dissolved Fc under flowing wet and dry dinitrogen gas (N₂) was found to be kinetically limited with a rate constant in the region of 2×10^?7 cm s^?1. The activation energy of diffusion for Fc was found to be 28.2±0.7 kJ mol^?1, while the activation energy of volatilisation of Fc from [C₄mpyrr][NTf₂] to dry N₂ was found to be 85±2 kJ mol^?1.     

NADH Electrocatalytic Oxidation on Gold Nanoparticle‐Modified PVC/TTF‐TCNQ Composite Electrode. Application as Amperometric Sensor

We herein report on the electrocatalytic activity towards the oxidation of NADH of a PVC/TTF‐TCNQ composite electrode modified with gold nanoparticles. This electrocatalytic property allows proposing this system as a new alternative for amperometric determination of NADH, without need to add another mediator. The sensor shows a linear response to NADH over a concentration range from 5.0×10^?6 M up to 5.0×10^?4 M, with a sensitivity of 11.22±0.5 mA M^?1 and a detection limit (S/N=3) of 4.0×10^?6 M for measurements in batch and similar data in FIA.     

Immobilization and Bioelectrochemistry of Hemoglobin Based on Carrageenan and Room Temperature Ionic Liquid Composite Film

A novel biopolymer/room‐temperature ionic liquid composite film based on carrageenan, room temperature ionic liquid (IL) [1‐butyl‐3‐methylimidazolium tetra?uoroborate ([BMIM]BF₄)] was explored for immobilization of hemoglobin (Hb) and construction of biosensor. Direct electrochemistry and electrocatalytic behaviors of Hb entrapped in the IL‐carrageenan composite ?lm on the surface of glassy carbon electrode (GCE) were investigated. UV‐vis spectroscopy demonstrated that Hb in the IL‐carrageenan composite ?lm could retain its native secondary structure. A pair of well‐de?ned redox peaks of Hb was obtained at the Hb‐IL‐carrageenan composite ?lm modi?ed electrode through direct electron transfer between the protein and the underlying electrode. The heterogeneous electron transfer rate constant (k_s) was 2.02 s^?1, indicating great facilitation of the electron transfer between Hb and IL‐carrageenan composite film modi?ed electrode. The modi?ed electrode showed excellent electrocatalytic activity toward reduction of hydrogen peroxide with a linear range of 5.0×10^?6 to 1.5×10^?4 mol/L and the detection limit was 2.12×10^?7 mol/L (S/N=3). The apparent Michaelis‐Menten constant K_M^app for hydrogen peroxide was estimated to be 0.02 mmol/L, indicating that the biosensor possessed high af?nity to hydrogen peroxide. In addition, the proposed biosensor showed good reproducibility and stability.     

Electrocatalytic Oxidation of Dopamine by Ferrocene in Lipid Film Cast on a Glassy Carbon Electrode

ＩｎｔｒｏｄｕｃｔｉｏｎＤＡｉｓｏｎｅｏｆｅｓｓｅｎｔｉａｌｐａｒｔｉｃｉｐａｎｔｓｉｎｔｈｅｎｅｕｒｏ ｔｒａｎｓｍｉｓｓｉｏｎｐｒｏｃｅｓｓｉｎｍａｍｍａｌｉａｎｃｅｎｔｒａｌｎｅｒｖｏｕｓｓｙｓ ｔｅｍ .ＡｌｏｓｓｏｆＤＡ ｃｏｎｔａｉｎｉｎｇｎｅｕｒｏｎｓｍａｙｒｅｓｕｌｔｉｎｓｏｍｅｓｅｒｉｏｕｓｄｉｓｅａｓｅｓｕｃｈａｓＰａｒｋｉｎｓｏｎｉｓｍ .1Ｓｉｎｃｅｉｔｓｄｉｓｃｏｖ ｅｒｙｉｎｔｈｅ 195 0ｓ ,ＤＡｈａｓｂｅｅｎｏｆｉｎｔｅｒｅｓｔｔｏｎｅｕｒｏｓｃｉｅｎ ｔｉｓｔｓａｎｄｃｈｅｍ…     

Synthesis,Spectra Characterization,Electrochemical Behavior of Silyl Derivatives of Ferrocene

Ferrocenyl‐substituted silanes via the reaction between mono and dilithio‐ferrocene with trimethyl, trietheyl, vinyldimethyl or t‐butyldimethyl chlorosilanes is prepared. The electrochemical behaviors of these compounds were investigated by cyclic voltammetry. This work describes the electrochemical and electrocatalytic properties of carbon ceramic electrode (CCE) modified with ferrocene composites as a new electrocatalyst material.     

Formation of triblock copolymers via a tandem enhanced spin capturing—nitroxide‐mediated polymerization reaction sequence

The preparation of ABA‐type block copolymers via tandem enhanced spin capturing polymerization (ESCP) and nitroxide‐mediated polymerization (NMP) processes is explored in‐depth. Midchain alkoxyamine functional polystyrenes (M_n = 6200, 12,500 and 19,900 g mol^?1) were chain extended with styrene as well as tert‐butyl acrylate at elevated temperature NMP conditions (T = 110 °C) generating a tandem ESCP‐NMP sequence. Although the chain extensions and thus the block copolymer formation processes function well (yielding in the case of the chain extension with styrene number average molecular weights of up to 20,800 g mol^?1 (PDI = 1.22) when the 6200 g mol^?1 precursor is used and up to 67,500 g mol^?1 (PDI = 1.36) when the 19,900 g mol^?1 precursor is used and 21,600 g mol^?1 (PDI = 1.17) as well as 37,100 g mol^?1 (PDI = 1.21) for the tert‐butyl acrylate chain extensions for the 6200 and 12,500 g mol^?1 precursors, respectively), it is also evident that the efficiency of the block copolymer formation process decreases with an increasing chain length of the ESCP precursor macromolecules (i.e., for the 19,900 g mol^?1 ESCP precursor no efficient chain extension with tert‐butyl acrylate can be observed). For the polystyrene‐block‐tert‐butyl acrylate‐block‐polystyrene polymers, the molecular weights were determined via triple detection SEC using light scattering and small‐angle X‐ray scattering. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Supramolecular Assembly of β‐Cyclodextrin‐Capped Gold Nanoparticles on Ferrocene‐Functionalized ITO Surface for Enhanced Voltammetric Analysis of Ascorbic Acid

A supramolecular recognition functionalized electrode (βCD‐nanoAu/Fc‐ITO) which exhibits redox‐activity was prepared through supramolecular assembly of β‐cyclodextrin (βCD) capped gold nanoparticles (βCD‐nanoAu) on the ITO previously coated with a monolayer of ferrocene residues (Fc‐ITO). The immobilization of βCD‐nanoAu on Fc‐ITO was confirmed by atomic force microscopy (AFM), and the supramolecular nature of the immobilization approach was also confirmed by cyclic voltammetry. On the other hand, the electrocatalytic activity of βCD‐nanoAu/Fc‐ITO electrode was also studied. The electrocatalytic activity toward ascorbic acid (AA) was enhanced compared with that at the Fc‐ITO electrode, and a linear relationship existed between the anodic peak and the concentration of AA in the range of 5.3×10^?5 to 3.0×10^?3 M with a detection limit (S/N=3) of 4.1×10^?6 M.     

Direct Electron Transfer of Glucose Oxidase and Glucose Biosensor Based on Nano-structural Attapulgite Clay Matrix

The direct electrochemistry of glucose oxidase (GOD) was achieved based on the immobilization of GOD on a natural nano‐structural attapulgite (ATP) clay film modified glassy carbon (GC) electrode. The immobilized GOD displayed a pair of well‐defined quasi‐reversible redox peaks with a formal potential (E^0′) of ?457.5 mV (vs. SCE) in 0.1 mol·L^?1 pH 7.0 phosphate buffer solution. The peak current was linearly dependent on the scan rate, indicating that the direct electrochemistry of GOD in that case was a surface‐controlled process. The immobilized glucose oxidase could retain bioactivity and catalyze the oxidation of glucose in the presence of ferrocene monocarboxylic acid (FMCA) as a mediator with the apparent Michaelis‐Menten constant K^app_m of 1.16 mmol·L^?1. The electrocatalytic response showed a linear dependence on the glucose concentration ranging widely from 5.0×10^?6 to 6.0×10^?4 mol·L^?1 (with correlation coefficient of 0.9960). This work demonstrated that the nano‐structural attapulgite clay was a good candidate material for the direct electrochemistry of the redox‐active enzyme and the construction of the related enzyme biosensors. The proposed biosensors were applied to determine the glucose in blood and urine samples with satisfactory results.     

Electrochemical Interrogation and Sensor Applications of Nanostructured Polypyrroles

The polymerization of pyrrole in β‐naphthalene sulfonic acid (NSA) gave nanotubules, nanomicelles or nanosheets of polypyrrole (PPy) depending on the amount of NSA in the polymer and the temperature of the reaction. Scanning electron microscopy (SEM) measurements showed that the diameters of the nanostructured polypyrrole‐β‐naphthalene sulfonic acid (PPyNSA) composites were 150–3000 nm for the tubules, 100–150 nm for the micelles and 20 nm for the sheets. A red shift in the UV‐vis absorption spectra of PPy was observed for PPyNSA which indicates the involvement of bulky β‐naphthalene sulfonate ion in the polymerization process. The UV‐vis also showed the existence of polaron and bi‐polaron in the polymer which may be responsible for the improved solubility of PPyNSA compared to PPy. All the characteristic IR bands of polypyrrole were observed in the FTIR spectra of PPyNSA, with slight variation in the absolute values. However, the absence of N? H stretching at 3400 cm^?1 and 1450 cm^?1 usually associated with neutral polypyrrole confirms that the polymer is not in the aromatic state but in the excited polaron and bipolaron defect state. Electrochemical analysis of PPyNSA reveals two redox couples: a/a′ – partly oxidized polypyrrole‐naphthalene sulfonate radical cation/neutral polypyrrole naphthalene sulfonate; b/b′ – fully oxidized naphthalene sulfonate radical cation/partly reduced polypyrrole‐naphthalene sulfonate radical anion. The corresponding formal potentials measured at 5 mV/s, E°′_{(5 mV/s)}, are 181 mV and 291 mV, respectively. Amperometric phenol sensor constructed with PPyNSA on a glassy carbon electrode (GCE) gave a sensitivity of 3.1 mA M^?1 and a dynamic linear range of 0.65–139.5 μM. The data for the determination of phenol on the GCE/PPyNSA electrode was consistent with the electrocatalytic Michaelis‐Menten model, giving an apparent Michaelis‐Menten constant (K_M′) value of 160 μM.     

Electroanalysis of Benazepril Hydrochloride Antihypertensive Drug Using an Ionic Liquid Crystal Modified Carbon Paste Electrode

Electroanalysis of benazepril HCl was successful using a carbon paste electrode modified with an ionic liquid crystal ( 1‐butyl‐1‐methylpiperidinium hexafluorophosphate) in presence of sodium dodecyl sulfate. The electrode performance was compared to ionic liquids (1‐n‐hexyl‐3‐methyl imidazolium tetrafluoroborate and 1‐butyl‐4‐methyl pyridinium tetrafluoroborate). Electrochemical determination of benazepril HCl was in the linear dynamic range of 8.89×10^?7 to 1.77×10^?5 mol L^?1 (correlation coefficient 0.999) and LOD 7.17×10^?9 mol L^?1. benazepril HCl was determined using this sensor in presence of urine metabolites such as uric acid, ascorbic acid. Binary mixtures of dopamine/benazepril and amlodipine/benazepril were also determined successfully.     

Electrochemical Activation of Graphite Nanosheets Decorated with Palladium Nanoparticles for High Performance Amperometric Hydrazine Sensor

Herein, we have demonstrated a preparation of palladium nanoparticles on electroactivated graphite nanosheets modified screen printed carbon electrode (PdNPs‐EGNS/SPCE) by a simple electrochemical method. The well‐prepared electrocatalyst was potentially applied to the high performance electrocatalytic oxidation of hydrazine in neutral medium. The PdNPs‐EGNS novel composite was characterized by scanning electron microscope (SEM) and the average diameter and thickness of PdNPs and EGNS were found to be ～38 nm and 85 nm, respectively. The high performance electrocatalytic determination of hydrazine was performed by the amperometric i‐t method. The fabricated sensor displayed irreversible electrocatalytic oxidation of hydrazine with diffusion‐controlled electrode process. The oxidation of hydrazine at PdNPs‐EGNS/SPCE showed wider linear range 0.05–1415 µM and high sensitivity 4.382 µA µM^?1 cm^?2. The as‐prepared electrocatalyst achieved quick response towards hydrazine with a lower detection limit 4 nM.     

Electroanalytical Studies on Cobalt(II) Ion‐Selective Sensor of Polymeric Membrane Electrode and Coated Graphite Electrode Based on N2O2 Salen Ligands

Poly(vinyl chloride)‐based membranes of salen ligands, 2‐((E)‐((1R,2S)‐2‐((E)‐5‐tert‐butyl‐2‐hydroxybenzylideneamino)cyclohexylimino)methyl)‐4‐tert‐butyl phenol (S₁) and 2‐((E)‐((1R,2S)‐2‐((E)‐3,5‐di‐tert‐butyl‐2‐hydroxybenzylideneamino)cyclohexylimino)methyl)‐4,6‐di‐tert‐butylphenol (S₂) were fabricated and explored as cobalt(II) selective electrodes. The performance of the polymeric membrane electrode (PME) and coated graphite electrode (CGE) were compared and it was observed that CGE showed a wide working concentration range of 1.1×10^?8 to 1.0×10^?1 mol L^?1 with a limit of detection of 7.0×10^?9 mol L^?1 exhibiting the Nernstian slope 29.6 mV/decade of activity in the pH range 3.0–9.0. It was used for the determination of cobalt(II) ions in water, soil, beer, pharmaceutical samples and medicinal plants and would be used as an indicator electrode in potentiometric titration with EDTA.     

A mechanism of photo-oxidative destruction for polythylene polymers in the presence of ferrocene derivative additives

The effect of ferrocene additive concentrations on the stability of polythylene polymers under atmospheric ageing and ultraviolet irradiation is reported. At concentrations under ca 5 × 10^?3 mol kg^?1 polymer the ferrocene compound is shown to diminish polymer resistance to light, whereas above this concentration such a compound stabilizes the polymeric matrix. Another purpose of the work is to look into the photo-oxidative destruction of polyethylene doped with ferrocene compound by using an EPR technique. A mechanism of photo-oxidative destruction of polyethylene polymers in the presence of ferrocene compounds is proposed.     

Periphery-substituted [4+6] salicylbisimine cage compounds with exceptionally high surface areas: influence of the molecular structure on nitrogen sorption properties

The synthesis of various periphery‐substituted shape‐persistent cage compounds by twelve‐fold condensation reactions of four triptycene triamines and six salicyldialdehydes is described, where the substituents systematically vary in bulkiness. The resulting cage compounds were studied as permanent porous material by nitrogen sorption measurements. When the material is amorphous, the steric demand of the cages exterior does not strongly influence the gas uptake, resulting in BET surface areas of approximately 700 m² g^?1 for all cage compounds 3 c – e , independently of the substituents bulkiness. In the crystalline state, materials of the same compounds show a strong interconnection between steric demand of the peripheral substituent and the resulting BET surface area. With increasing bulkiness, the overall BET surface area decreases, for example 1291 m² g^?1 (for cage compound 3 c with methyl substituents), 309 m² g^?1 (for cage compound 3 d with 2‐(2‐ethyl‐pentyl) substituents) and 22 m² g^?1 (for cage compound 3 e with trityl substituents). Furthermore, we found that two different crystalline polymorphs of the cage compound 3 a (with tert‐butyl substituents) differ also in nitrogen sorption, resulting in a BET surface area of 1377 m²g^?1, when synthesized from THF and 2071 m²g^?1, when recrystallized from DMSO.