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Abstract: A novel nanocomposites film of conducting polymers including single-walled carbon nanotubes (SWCNTs), polypyrrole (PPy) and gold nanoparticles (AuNPs) modified electrode has been applied in voltammetric sensors to detect epinephrine (EP) sensitively when ascorbic acids (AA) and uric acids (UA) exist. The nanocomposites film of conducting polymers which show an excellent electrocatalystic activity for the oxidation of EP and UA was characterized by scanning electron microscopy (SEM) and electrochemical methods. The catalytic peak currents obtained from differential pulse voltammetry (DPV) increased linearly with increasing EP concentrations in the range of 4.0×10−9–1.0×10−7 M with a detection limit of 2.0×10−9 M (S/N=3), respectively. The results showed that the nanocomposites of conducting polymers can selectively determine EP in the coexistence of a large amount of UA and AA. In addition, the sensor exhibited excellent sensitivity, selectivity and stability. The PPy/AuNPs/SWCNTs nanocomposites film can also be satisfactorily used for detecting EP in epinephrine hydrochloride injection when contain AA and UA, which also shows good recovery for determination of EP in some biological fluids. [Copyright &y& Elsevier]

Abstract: Substituent effects of iron porphyrin complexes on the structures and kinetic processes have been examined for the first time. Basing on the premise that iron porphyrin is functional analogous to heme, a series of iron porphyrin derivatives bearing different substituents at the meso positions of the corrole ring are investigated as to their electrochemistry, the relationships among the electron transfer (ET) processes, their structures, and orbital energies. The good coherence between the experiment and theory indicates that the ET rate can be accelerated when electron-donating substituents are introduced to the iron porphyrin ring. Finally, the implications of the results are discussed in the influence of stability of iron porphyrin complexes on the ability to carry molecular oxygen, which may suggest it possible to dominate the biological activity of heme by selecting the appropriate substituents to iron porphyrin ring. [Copyright &y& Elsevier]

Nano-γ-Al2O3 is dispersed onto the glass carbon electrode (GCE) by polishing. This nanostructured modified GCE exhibits a great enhancement to the redox responses of 3-nitrobenzaldehyde thiosemicarbazone (3-NBT). In comparison with bare GCE, 3-NBT gives a more sensitive voltammetric response because of the nanoparticle’s unique properties. The lowest detectable concentration (3σ) of 3-NBT is estimated to be 1.18 × 10-6M (accumulation for 4min). The linear relationship between peak current and concentration of 3-NBT holds in the range 1.0 × 10-5M to 1.0 × 10-4M (r = 0.9981). The electrochemical properties of 3-NBT on this modified electrode have been investigated with various electrochemical methods. The results indicate that the transference of one electron and one proton involves electrode radical reaction processes I and II, respectively. The coverage value (Γ) of 1.62 × 10-9molcm-2 was calculated and the electrochemical parameters, diffusion coefficient D (2.54 × 10-3cm2s-1, 2.03 × 10-3cm2s-1) and reaction rate constant ks (5.9573s-1, 7.15 × 10-2cms-1) were obtained for quasi-reversible system I and irreversible system II, respectively. [Copyright &y& Elsevier]

Abstract: The electrochemical behaviors of self-assembled substituted porphyrins (SH-terminated, abbreviated as H2TPPO(CH2) n SH, n =3, 12) on a gold electrode were investigated using the steady-state scanning electrochemical microscopy (SECM). The different electron-transfer (ET) kinetics, including the bimolecular ET between the porphyrin self-assembled monolayers (SAMs) and the redox mediator [K3Fe(CN)6], the tunneling ET between the underlying gold electrode and [K3Fe(CN)6], and pinholes or defects, were clearly distinguishable. The SECM strategy was developed to deal with the two types of porphyrin SAMs. First, a model using alkanethiols [(CH2) n SH, n =3, 12] as the functional template was proposed to change the conformation of porphyrin SAMs in a unit area of the electrode. Second, the porphyrin SAMs were directly prepared by inserting a metal (cobalt) into the center of the porphyrin ring. The results show the distinct effect of the presence of alkanethiols on the kinetics of the different-chain length porphyrins. In addition, the rate constants of the bimolecular ET significantly increased after the insertion of cobalt. The results are in agreement with the density functional theory (DFT). [Copyright &y& Elsevier]

Abstract: Capacitive detection of methyl-parathion (MP) was carried out on a polyquercetin (Qu)–polyresorcinol (Re)–gold nanoparticles (AuNPs) modified electrode using a molecular imprinting technique and electropolymerization method. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) measurements were used to monitor the process of electropolymerization. Uncovered surface areas were plugged with dodecanethiol to make the layer dense, and the insulating properties of the layer were studied in the presence of [Fe(CN)6]3−/[Fe(CN)6]4− redox couples and by the use of AC impedance measurements. The template molecules and the non-bound thiol were removed from the molecularly imprinted polymer film capacitance sensor surface with an acidic solution of ethanol. The sensor''s linear response range was between 7×10−8 molL−1 and 1×10−6 molL−1, with a detection limit of 3.4×10−10 molL−1. The presented research provides a fast, sensitive and real-time method for detecting organophosphate pesticides. In water and in organic samples, the modified electrode has good anti-interference capabilities and stability (distilled water, tap water, river water, and rain water samples all have good recovery). Moreover, the MIPC sensor can detect MP on fruit surfaces within 72h after spraying pesticides. [Copyright &y& Elsevier]

Abstract: The combination of biomolecules-functionalized multiwalled carbon nanotube (MWNTs) and ionic liquid (IL) yields nanostructured biointerfaces, formed a novel kind of structurally uniform and bioelectrocatalytic activity material. Rutin was chosen as a model biomolecules to investigate the composite system. The MWNTs–Rutin–IL composite film was characterized by different methods including thermogravimetric analysis (TGA), UV–vis spectra, electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscope (SECM). A pair of well-defined quasi reversible redox peaks of rutin was obtained at the MWNTs–Rutin–IL composite film modified glassy carbon electrode (GCE) by direct electron transfer between the rutin and the GCE electrode. Dramatically enhanced biocatalytic and electrocatalytic activity was exemplified at the MWNTs–Rutin–IL/GCE electrode by the oxidized of tryptophane. The oxidation peak currents of tryptophane in such modified electrode increased linearly with the concentrations of tryptophane in the range from 8×10−8 to 2×10−5 molL−1 with a detection limit of 3.0×10−8 molL−1. The unique composite material based on biomolecules-functionalized carbon nanotube and ionic liquid have wide potential applications in direct electrochemistry, biosensors, and biocatalysis. [Copyright &y& Elsevier]

Abstract: The rate constant of electron transfer reaction between ferrous ion in aqueous phase and decamethyferrocene located on the adjacent aqueous phase was measured by thin layer method, a simple protocol reported recently for studying electron transfer reaction at liquid/liquid interface. Despite this large increase in overall driving force, the rate constants decrease by less than an order of magnitude compared the two reaction systems of Fe3+–DMFe and Fe(CN)6 3−–DMFe. The results demonstrate that reorganization energy may be a dominating factor on the rate of electron transfer across the interface due to the effect of the size and symmetry of reactants in aqueous. In addition, the effect of thickness of the thin layers is investigated further. [Copyright &y& Elsevier]