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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]

Abstract: Multilayers film of nanostructured gold nanoparticles (AuNPs) has been fabricated based on the layer-by-layer (LBL) technique using a self-assembled monolayer of 5,15-di-[p-(6-mercaptohexyl)-phenyl]-10,20-diphenylporphyrin (trans-PPS2). AuNPs act as physical cross-link points in the multilayers. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) are applied to study the formation of the organic–inorganic multilayers film and have determined the electrochemical parameters, i.e., the heterogeneous electron transfer rate constant (K et). The observed phenomena indicate that the electron transfer (ET) process is affected by material properties and the molecular structure of self-assembled monolayers (SAMs). Using the high sensitivity of ET of ferricyanide to the modification of the gold surface with multilayers film, we select this reaction as a probe to study the different modification stages at this modified electrode. ET is retarded on the trans-PPS2 alternative deposition of layers on the electrode surface and is accelerated on the AuNPs’ layers. SECM images are used to collect surface information in the course of the successive modification process. SECM images obtained from bare and different modification stages show very high resolution with different topographies. [Copyright &y& Elsevier]

• A hand-torn bread-like 3D porous structure anode was firstly proposed in MFCs. • A new mode of accelerating electronic transfer was explored. • PANI-PPy-Ag NWs/CF hydrogel anodes are hydrophilic and biocompatible. • It has high COD removal rate (96.69 %) and power density output (2196.61 mW/m3). • The two direct electron transfer pathways were achieved simultaneously. Microbial fuel cell (MFC) can generate electrons through microbial metabolism of organic matter in sewage. In this paper, carbon felt as base material, the conductive polymers polyaniline and polypyrrole combined with silver nanowires were doped in hydrogel, a super hydrophilicity, low electron transfer resistance, good biocompatibility hydrogel MFC anode (PANI-PPy-Ag NWs/CF) were prepared. It showed a hand-torn bread structure, this three-dimensional (3D) porous structure increased microbial attachment amount. The anode could reach a maximum voltage output of 0.66 V in only 5.5 h, and produce a maximum power density of 2196.61 mW/m3. Due to the doping of silver nanowire, a new electronic mode was explored, coulomb efficiency of 31.01 % and an ultra-high COD removal rate (96.69 %) was obtained. This study introduces a conductive composite hydrogel MFC anode, which provides a new idea for the material diversity, electrical production and sewage removal performance of MFC anode. [ABSTRACT FROM AUTHOR]

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]

In situ reduction of AgI to Ag nanoparticles (Ag NPs) supported on C-doped boron nitride (AgI/BN-C) was developed for CO 2 electroreduction to CO with a much enhanced faradaic efficiency (FE) of 99.5 % and a high current density of 56.3 mA cm−2. The enhanced performance is mainly attributed to the controllable construction of Ag0-Ag+ sites, which effectively provides a large number of active sites, enhances the adsorption strength of the intermediate and accelerates the reaction kinetics. [ABSTRACT FROM AUTHOR]

The porphyrin aggregate is recognized as an attractive candidate for developing artificial light-harvesting systems. Using 5, 10, 15, 20-tetrakis-(4-carboxyphenyl) porphyrin (TCPP), the porphyrin aggregates with different morphologies (sphere, rod and flake) are controllably prepared by the surfactant-assisted self-assembly reaction, and then synthesize the ternary bionic-system (e.g. porphyrin composites). These composites are characterized by scanning-electron microscopy (SEM), atomic force microscope (AFM) and spectroscopic technology. The combinatorial technique consisted of ultraviolet–visible spectroscopy and scanning electrochemical microscopy (UV–vis/SECM) is used to record SECM approach curves of porphyrin photocatalysis under visible light illumination at the specific zones, where morphology-dependent porphyrin composite is recognized to be distributed evenly on ITO surface. Heterogeneous photoelectron transfer rates ( k eff ) are given by simulating SECM approach curves. It is suggested that rod-like porphyrin aggregate composite has highest photocatalytic efficiency with the kinetics rate to be 8.624 × 10 −2  cm s −1 , the largest k eff of which is obtained at the excitation wavelength of 469 nm. These findings are also proved by photocatalytic decomposition test of pollutants (methyl orange). It is indicated that one-dimensional nanostructure is advantageous for separation of electrons and holes and directional transmission of photoelectron. [ABSTRACT FROM AUTHOR]

As efficient electron transfer mediator, various nanomaterials with smart performance have been explored in non-enzymatic sensor fabrication. We herein present an electron transfer mediator actuated electrochemical non-enzymatic sensor to assay nitrite, enabled by electrochemical reduced graphene oxide (ERGO) and 1-(2-pyridylazo)-2-naphthol (PAN). The composites of PAN-ERGO coating on electrode surface were successfully fabricated through a facile and green cyclic voltammetry technique. With the aid of ERGO nanosheets on the electrode surface, the electron transfer mediator of PAN nanostructures was easily immobilized and hybridized with ERGO, resulting in a remarkably synergistic effect between ERGO sensing substrate and the electrodeposited PAN coating for target electron transfer. The results demonstrated that the electrocatalytic current increased linearly with the nitrite concentration in the range of 7.49–1752.6 μM and 1752.6–3500 μM, with a good detection limit of 0.67 μM and 1.44 μM (signal-to-noise ratio, S/N = 3), respectively. The present work provide some new insights for the smart design of high efficiency electrocatalytic materials that based on the composites of electrochemical reduced graphene oxide and other substances. [ABSTRACT FROM AUTHOR]

A novel of eco-friendly molecularly imprinted electrochemical luminescence biosensor was designed, based on nanomaterials, CdSeTe/ZnS core-shell QDs and molecularly imprinted polymer composites modified glass carbon electrode. Combining the superior selectivity of molecularly imprinted polymer and the high sensitivity of electrochemical luminescence would achieve the trace determination of dopamine. And the cavities in molecularly imprinted polymer after eluting were applied as the substrate to capture target molecular dopamine. The electron transform channel for the redox reaction of CdSeTe/ZnS QDs and co-reaction K 2 S 2 O 8 was blocked with the increase of dopamine concentration, resulting in the cathodic ECL intensity decreased correspondingly. Therefore, the dopamine was detected in the concentration range from 1 × 10 −14 mol/L to 2.5 × 10 −12 mol/L, with the low detection limit of 3.3 × 10 −15 mol/L. The MIP-ECL biosensor showed easy preparation, low lost, lower detection limit, good selectivity and stability, and could be used for the detection of dopamine in the human serum successfully. [ABSTRACT FROM AUTHOR]

Many methods have been proposed for graphene production with good dispersion both in the drying state and in common solvents. In this work, a facile and convenient approach to synthesis of electrochemical reduction graphene oxide (ERGO) and nickel oxide nanoparticles composite through cyclic voltammetry is reported. The proposed method is fast, and green, no toxic solvents are used and therefore will not result in contamination of the as-prepared composites. The products have been successfully characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and Photoelectron spectroscopy, and electrochemical technology. The results show that well dispersed composites with layered nanostructures consisting of alternating layers of metal oxide nanoparticles and ERGO sheets can be achieved by the proposed strategy. A thin layer model is used to illustrate the effects of diffusion within the layered nanostructures. The obtained composites modified electrode exhibits superior catalytic performance for the target molecule of 2, 4, 6-trinitrophenol (TNP). [ABSTRACT FROM AUTHOR]

This paper focused on study of the interfacial consecutive electron transfer (ET) kinetics and the redox behaviors of three 5,10,15,20-zinc-tetraarylporphyrins (ZnTArPs) with a systematic variation of meso-π-extension at a 2 n (0 ≤ n ≤ 2) pattern, where 2 n was the number of benzene ring in an aryl group. The two-step redox potentials of 5,10,15,20-zinc-tetraphenylporphyrin (ZnTPP) were more negative than that of 5,10,15,20-zinc-tetranaphthylporphyrin (ZnTNP) and 5,10,15,20-zinc-tetrapyrenylporphyrin (ZnTPyP), suggesting that ZnTPP was the most active reactant among three ZnTArPs. It was found that the consecutive two-step ET rate was insensitive to the change of the overall driving force in a wide potential region for ZnTArP-Fe(CN) 6 4− reaction systems. The solvation effect on consecutive ET rate constant is discussed in detail. The molecular structures of ZnTArP, [Zn(TArP )] + and [Zn(TArP )] 2+ were optimized by using density functional theory. The calculation results showed that ZnTPyP cation was the most active species among tree ZnTArP cations at a fixed valence state. [ABSTRACT FROM AUTHOR]

A two-step cathodic electrochemiluminescence (ECL) of meso-tetra(4-carboxyphenyl) porphyrin (TCPP) in aqueous solution has been reported for the first time. ECL generates upon sweeping from -0.2 V to -1.5 V using potassium peroxydisulfate (K 2 S 2 O 8 ) as a reductive–oxidative coreactant. Two cathodic ECL peaks are found simultaneously. One appears at -0.8 V which is corresponding to the reduction of TCPP, another is at -1.1 V that is attributed to the reduction of K 2 S 2 O 8 . ECL efficiency ( φ ecl ) is 0.22 for TCPP using Ru(bpy) 3 2+ /S 2 O 8 2− as the standard ( φ ecl = 1). Under the optimum conditions, ECL intensity has a linear relationship with the concentration of TCPP in the range of 2.0 × 10 −7 to 1.0 × 10 −5 mol L −1 with the detection limit of 1.7 × 10 −8 mol L −1 . The practical application to determination pheophorbide which is obtained from fresh spinach leaves has been accomplished. The results demonstrate the facility and effectivity of our method for quantitative analysis of porphyrin. At the same time of building this method, the possible ECL mechanism is discussed in detail. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel cholesterol biosensor was constructed based on ChOx-IL-capped-AuNPs/GCE. [•] IL-capped-AuNPs was synthesized using two-phase synthesis and employed as a conducting matrix to immobilize ChOx. [•] Direct electrochemistry of ChOx on the electrode was obtained. [•] The ChOx-IL-capped-AuNPs/GCE exhibit remarkable performance for cholesterol detection. [ABSTRACT FROM AUTHOR]

Abstract: An efficient sensing platform based on functionalized reduced graphene oxide (rGO) for the detection of nitro aromatic compounds was developed in this work. Firstly, rGO was functionalized with 1,3,6,8-pyrene tetra sulfonic acid sodium salt (PyTS) through π–π interaction among molecules, which could not only improve the solubility and dispersibility of the rGO in aqueous solution but also provide more binding sites for nanoparticles. Secondly, palladium nanoparticles (Pd NPs) were uniformly decorated on the functionalized rGO nanosheets with the help of sulfonic acid group. The obtained nanocomposite (marked as Pd NPs-PyTS/rGO) was then characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), X-Ray Diffraction (XRD) and Electrochemical Impedance Spectroscopy (EIS). Finally, the electrochemical sensor was built up by casting Pd NPs-PyTS/rGO on the surface of glassy carbon electrode (GCE) and electrochemical properties of the nitro aromatic compounds have been studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The results showed that Pd NPs-PyTS/rGO modified electrode possessed higher electrocatalytic activity and sensitivity for nitrobenzene (NB). The detection limit was as low as 0.62ppb. This may be attributed to the combination of the large surface area of rGO and effective electrocatalytic property of Pd NPs. Experimental results showed that Pd NPs-PyTS/rGO modified the electrode was a fast, simple and controllable method for electrochemical sensor. [Copyright &y& Elsevier]

Highlights: [•] A novel nonenzymatic H2O2 sensor was constructed on AgNPs/MWCNTs-IL modified GCE. [•] Ionic liquid functionalized carbon nanotube was used as matrices for deposition of AgNPs effectively. [•] AgNPs were uniformly and less agglomerate formed on the MWCNTs-IL film. [•] AgNPs/MWCNTs-IL/GCE displayed good electrocatalytic activity to the reduction of H2O2 and applied to real samples. [•] The electrocatalytic mechanism of the constructed sensor was proposed. [ABSTRACT FROM AUTHOR]

Abstract: A novel cholesterol biosensor was fabricated on hydrophobic ionic liquid (IL)/aqueous solution interface. The hydrophobic IL thin film played a signal amplification role because it not only enriched the cholesterol from the aqueous solution, but also immobilized matrix for cholesterol oxidase (ChOx). Prussian blue (PB) as advanced sensing materials was used as effective low-potential electron transfer mediation toward hydrogen peroxide (H2O2). The fabricated IL-ChOx/PB/Glassy carbon electrode (GCE) was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV), respectively. And it exhibited a linear response to cholesterol in the range of 0.01–0.40mM with a detection limit of 4.4μM. In addition, the kinetics behavior of cholesterol at IL-Chox/PB/GCE electrode was examined, and the electrocatalytic mechanism was proposed as shown in first scheme. ChOx immobilized in hydrophobic IL thin film was used as the first electrocatalyst for the cholesterol into H2O2, and the PB film onto the GCE was used as the second electrocatalyst for the 2e− reduction of the produced H2O2 into H2O. [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]