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This paper reports the electrocatalytic properties of layer by layer (LbL) films formed by gold nanoparticles stabilized in propylpyridinium silsesquioxane polymer (AuNPs-SiPy + ) as polycation, and prussian blue nanoparticles (PB) as polyanion with synergistic effect in the H 2 O 2 reduction. Under optimized synthesis conditions by factorial design, the TEM images of gold nanoparticles showed spherical shape with diameter ranging from 2 to 35 nm. All modified electrodes with inorganic materials were explored by spectroscopy (UV-Vis and FTIR) and electrochemical techniques (Cyclic Voltammetry, Chronoamperometry and Electrochemical Impedance Spectroscopy). We demonstrated that the presence of gold nanoparticles greatly enhanced the electroactive properties of the multilayer films providing interesting electrochemical features and excellent sensitivity in the electrocatalytic reduction of hydrogen peroxide, compared to electrode containing only the silsesquioxane polymer as cationic polyelectrolyte. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical decoration of Au and Pd nanoparticles by Pd and Au atoms respectively is discussed in a statistical mechanical framework. It is found that depending on precursor nanoparticle size and shape, controlled decoration may be achieved in undersaturation or oversaturation conditions. Multilayer deposition is also considered, with the finding that this phenomenon is also size dependent. [Copyright &y& Elsevier]

Abstract: The poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene nanosheets (PDDA-G) were prepared and gold nano-particles (AuNPs) were assembled on the surface of PDDA-G film through electrostatic interaction to construct the biocompatible interface. The resulting AuNPs/PDDA-G nanocomposite film exhibited enhanced capability for hemoglobin (Hb) immobilization and realized its direct electrochemistry. The surface concentration (Γ*) of electroactive Hb on the surface of GCE was calculated to be 3.85×10−9 mol/cm2. Moreover, the AuNPs/PDDA-G based sensor showed prominent electrocatalytic activity for the detection of H2O2 with a wide linear range from 6μM to 1010μM and a low detection limit of 0.39μM at 3σ. Meanwhile, the apparent Michaelis–Menten constant (K m) was 0.51mM. This biosensor exhibited high sensitivity and fast responses, which may provide a novel way for fabrication of other graphene based sensors and broaden the application of graphene in biosensing. [Copyright &y& Elsevier]

Abstract: The transcription factor nuclear factor kappa B (NF-κB) is always a standard for inducible transcription factors, while nearly all NF-κB studies require the measurement of the level of activated NF-κB in cells. Herein we report a novel electrochemical approach for accurate detection of NF-κB with the help of triplex DNA and gold nanoparticles (AuNPs). Firstly, double-stranded DNA (dsDNA) molecules are self-assembled on the surface of a gold electrode. Then, AuNPs are functionalized with triplex-forming oligonucleotide (TFO). Since TFO may act with the dsDNA to form triplex DNA, the TFO functionalized on the AuNPs surfaces will bind with the dsDNA immobilized on the electrode surface, bringing large amounts of electrochemical compounds [Ru(NH3)6]3+ close to the electrode to generate an intense electrochemical signal. However, in the presence of NF-κB, the protein will capture and bind with the dsDNA to replace TFO–AuNPs, resulting in significant decrease of electrochemical signal of [Ru(NH3)6]3+. By using this “on-off” strategy, NF-κB has been quantified in the range from 0.4 to 12.0nM, with a detection limit of 0.13nM. This approach has also been successfully used to detect NF-κB in contaminated samples with high specificity. [Copyright &y& Elsevier]

Abstract: In this work, we report a new sonoelectrochemical pathway to prepare enriched and small Au nanoparticles (NPs) in aqueous solutions via aid of chitosan (Ch). First, Au substrate was cycled in a deoxygenated aqueous solution containing 0.1M NaCl and 1g/L Ch from −0.28 to +1.22V vs Ag/AgCl at 500mV/s for 500 scans. The durations at the cathodic and anodic vertices are 10 and 5s, respectively. Subsequently, a cathodic overpotential of 0.6V and an anodic overpotential of 0.2V from open circuit potential (OCP) were applied in turn under sonication to prepare enriched and small Au NPs. The ratio of reaction time during cathodic overpotential to that during anodic overpotential was investigated to be 0.5 for obtaining enriched and smaller Au NPs of 5nm in diameter in solution. The catalytic activity of the prepared Au NPs was examined by analyzing the decomposition of acetaldehyde in solution. Experimental results indicate that the decomposition of acetaldehyde based on the prepared Au NPs is significantly increased by ca. 240% of magnitude, as compared with that based on previously prepared Au NPs of 10nm at the same Au concentration. [Copyright &y& Elsevier]

Abstract: The usefulness of Keggin-type anions (PMo12O40 3−) as both reducing, capping and activating agents during synthesis of polyoxometallate-modified gold nanoparticles is demonstrated here. Fabrication of gold nanoparticles stabilized with monolayer-type films of inorganic polyoxometallates (e.g. phosphododecamolybdates), Au-PMo12, was achieved by treating an aqueous solution of gold precursor (HAuCl4) with a solution of the partially reduced heteropolyblue molybdate. The choice of temperature strongly affected morphology and size of the resulting Au nanoparticles. The presence of strongly adsorbed molybdate-agents on surfaces of gold nanoparticles was evident from the independent infrared (FTIR by reflectance) and voltammetric experiments. Interfacial polymolybdate anions on Au prevent the particle agglomeration and support formation of the stable colloidal Au-PMo12 solutions. They are colored due to existence of the plasmonic effect. The Au-PMo12 nanoparticles typically had 30–40nm diameters, and they were used as supports or carriers for dispersed catalytic platinum nanoparticles (of ca. 7–8nm diameters). Polyoxometallates (PMo12O40 3−) existing on gold surfaces could also interact with neighboring platinum centers thus acting as “linking” agents facilitating dispersion of Pt nanoparticles. Further, the phosphomolybdate adsorbates (on Au supports) are also likely to activate Pt sites (e.g. by providing reactive hydroxy groups) towards more efficient electrocatalytic oxidation of ethanol both under voltammetric and chronoamperometric conditions. [Copyright &y& Elsevier]

Abstract: In this paper, a novel nitrite sensor was constructed based on electrodeposition of gold nanoparticles (AuNPs) on a copper calcined layered double hydroxide (Cu-CLDH) modified glassy carbon electrode. Electrochemical experiments showed that AuNPs/CLDH composite film exhibited excellent electrocatalytic oxidation activity with nitrite due to the synergistic effect of the Cu-CLDH with AuNPs. The fabricated sensor exhibited excellent performance for nitrite detection within a wide concentration interval of 1–191μM and with a detection limit of 0.5μM. The superior electrocatalytic response to nitrite was mainly attributed to the large surface area, minimized diffusion resistance, and enhanced electron transfer of the Cu-CLDH and AuNPs composition film. This platform offers a novel route for nitrite sensing with wide analytical applications and will supply the practical applications for a variety of simple, robust, and easy-to-manufacture analytical approaches in the future. [Copyright &y& Elsevier]

Abstract: The preparation of gold nanoparticles (Au-NPs) displaying specific shape, size and surface crystallographic domains has been investigated aiming to clarify the effect of the surface crystallographic orientation, of the synthesised nanoparticles, and surfactant influence on the electrochemical response of the ITO/Au-NPs modified electrodes. Polymorphic and nanorod-shaped Au-NPs have been obtained using distinct synthetic procedures in the presence of cetyltrimethylammonium bromide (CTAB), through seed-mediated growth methods, displaying distinct surface crystallographic domains confirmed by transmission electron microscopy, X-ray diffraction analysis and under potential deposition (UPD) of lead. The nanoparticles have been physically immobilised by casting on indium tin oxide (ITO) surfaces and the electrocatalytic activity of the Au-NPs evaluated using the ascorbic acid (AA) oxidation reaction, by cyclic voltammetry. The polymorphic and distinct surface crystallographic orientations of the Au-NPs were reflected in an irreproducible electrochemical response. Using gold nanorods comprising (111) and (110) facets and gold nanocubes consisting of faces displaying (100) surface domains, by contrasting the behaviour of CTAB-stabilised and clean particles, it has been possible to verify that the distinct voltammetric results are due to the exposure of specific crystallographic orientations owing to dissimilar interaction strength of CTAB with those facets. [Copyright &y& Elsevier]

Abstract: We have developed a polyaniline/carboxy-functionalized multiwalled carbon nanotube (PAn/MWCNTCOOH) nanocomposite by blending the emeraldine base form of polyaniline (PAn) and carboxy-functionalized multiwalled carbon nanotubes (MWCNT) in dried dimethyl sulfoxide (DMSO) at room temperature. The conductivity of the resulting PAn/MWCNTCOOH was 3.6×10−3 Scm−1, mainly as a result of the protonation of the PAn with the carboxyl group and the radical cations of the MWCNT fragments. Horseradish peroxidase (HRP) was immobilized within the PAn/MWCNTCOOH nanocomposite modified Au (PAn/MWCNTCOOH/Au) electrode to form HRP/PAn/MWCNTCOOH/Au for use as a hydrogen peroxide (H2O2) sensor. The adsorption between the negatively charged PAn/MWCNTCOOH nanocomposite and the positively charged HRP resulted in a very good sensitivity to H2O2 and an increased electrochemically catalytical current during cyclic voltammetry. The HRP/PAn/MWCNTCOOH/Au electrode exhibited a broad linear response range for H2O2 concentrations (86μM–10mM). This sensor exhibited good sensitivity (194.9μAmM−1 cm−2), a fast response time (2.9s), and good reproducibility and stability at an applied potential of −0.35V. The construction of the enzymatic sensor demonstrated the potential application of PAn/MWCNTCOOH nanocomposites for the detection of H2O2 with high performance and excellent stability. [Copyright &y& Elsevier]

Abstract: A new signal amplification strategy employing nanocomposites composed of gold nanoparticles (GNPs) with DNA and methylene blue (MB) as labels has been developed to construct a novel immunosensor for the highly sensitive bioanalysis of carcinoembryonic antigen (CEA). To fabricate the label, DNA was first linked to GNPs through the formation of an Au–S bond. Next, the resulting bioconjugates were sequentially bound with MB via the guanine (G) bases in DNA specifically and then with secondary CEA antibody (Ab2) via the crosslinking of glutaraldehyde (GA). The receptor–analyte complex is formed by the biorecognition of the as-obtained MB labeled Ab2 with the primary CEA antibody (Ab1) immobilized on the surface of a modified GNP/Chitosan (Chits) composite electrode. After the receptor–analyte complex has formed, square wave voltammetry (SWV) was employed to oxidize the labeled MB in order to detect the CEA. This immunosensor shows a linear response from 0.10 to 2.0pgmL−1 CEA with an improved detection limit of 0.05pgmL−1 as compared to the conventional immunoassay. In addition, this new protocol shows acceptable stability, reproducibility and good recovery (97.5–110.0%) for CEA in human serum with great potential for clinical applications. [Copyright &y& Elsevier]

Abstract: Two new rhenium(I) carbonyl complexes with cationic 2,2′-bipyridyl ligands were synthesized and characterized. The electrogenerated chemiluminescence (ECL) of the rhenium(I) carbonyl complexes was first investigated in aqueous solution using the co-reactant tri-n-propylamine (TPrA). The ECL behavior of the complexes was also studied in the presence of several surfactants. The oxidation of both TPrA and the rhenium(I) complexes was facilitated in the presence of Triton X-100, and the ECL intensity was enhanced 300-fold at a Au electrode. [Copyright &y& Elsevier]

Abstract: The electrochemical behavior of 1,4-dinitrobenzene (1,4-PNB) on the Au electrode was investigated by cyclic voltammetry (CV), in situ FT-IR spectroelectrochemistry, cyclic voltabsorptometry (CVA) and derivative cyclic voltabsorptometry (DCVA) techniques. In aprotic media, 1,4-dinitrobenzene is reversibly reduced in two-step one-electron transfer. A series of IR absorption bands at 1056, 1210, 1341, 1356, 1464 and 1549cm−1, tracing to PNB; PNB − and PNB2− are observed. In the presence of proton donors mixed media, with increasing concentrations of proton donors, hydrogen-bonding and protonation process are found successively. The values of combining proton donors with per PNB2− to form hydrogen-bonding are estimated by using electrochemical parameters. The result of forming aromatic nitroso compound is supported by tracing the change of IR absorption bands at 1149 and 1587cm−1 at high concentration of proton donors. Based on CVA and DCVA techniques, it is clearly distinguished that the mechanisms of electrochemical reduction of PNB are elaborated in different systems. [Copyright &y& Elsevier]

Abstract: The paper reported an ultrasensitive electrochemical biosensor for glucose which was based on CdTe-CdS core–shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle. Since efficient electron transfer between glucose oxidase and the electrode was achieved, the biosensor showed high sensitivity (5762.8nAnM−1 cm−2), low detection limit (S/N=3) (3×10−12 M), fast response time (0.045s), wide calibration range (from 1×10−11 M to 1×10−8 M) and good long-term stability (26weeks). The apparent Michaelis–Menten constant of the glucose oxidase on the medium, 5.24×10−6 mM, indicates excellent bioelectrocatalytic activity of the immobilized enzyme towards glucose oxidation. Moreover, the effects of omitting graphene-gold nanocomposite, CdTe-CdS core–shell quantum dot and gold nanoparticle were also investigated. The result showed sensitivity of the biosensor is 7.67-fold better if graphene-gold nanocomposite, CdTe-CdS core–shell quantum dot and gold nanoparticle are used. This could be ascribed to improvement of the conductivity between graphene nanosheets due to introduction of gold nanoparticles, ultrafast charge transfer from CdTe-CdS core–shell quantum dot to graphene nanosheets and gold nanoparticle due to unique electrochemical properties of the CdTe-CdS core–shell quantum dot and good biocompatibility of gold nanoparticle for glucose oxidase. The biosensor is of best sensitivity in all glucose biosensors based on graphene nanomaterials up to now and has been satisfactorily applied to determination of the glucose in human saliva samples. [Copyright &y& Elsevier]

Abstract: Holographic lithography in combination with electrochemical deposition provides a novel and readily controlled method for preparing dendritic three-dimensional silver nanostructure with a large surface area. The scanning electron microscope and the synchrotron radiation X-ray three-dimensional imaging technique are used to characterize the as-prepared silver nanomaterial and demonstrate that the obtained silver has a three-dimensional dendritic morphology. The observed typical widths between the neighbor branches of the dendritic silver nanostructure are 30–50nm. The configuration of the silver nanostructure is greatly related to the width of gold wires which are fabricated using holographic lithography and serve as substrate of the silver nanostructure. The three-dimensional silver architecture is formed only when silver is electrochemically deposited on 400-nm-width gold. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotubes (MWCNT)/polyelectrolyte (PE) hybrid thin films were fabricated by alternatively depositing negatively charged MWCNT and positively charged (diallyldimethylammonium chloride) (PDDA) via layer-by-layer (LbL) assembly technique. The stepwise growth of the multilayer films of MWCNT and PDDA was characterized by UV–vis spectroscopy. Scanning electron microscopy (SEM) images indicated that the MWCNT were uniformly embedded in the film to form a network and the coverage density of MWCNT increased with layer number. Au nanoparticles (NPs) could be further adsorbed onto the film to form PE/MWCNT/Au NPs composite films. The electron transfer behaviour of multilayer films with different compositions were studied by cyclic voltammetry using [Fe(CN)6]3−/4− as an electrochemical probe. The results indicated that the incorporation of MWCNT and Au NPs not only greatly improved the electronic conductivity of pure polyelectrolyte films, but also provided excellent electrocatalytic activity towards the oxidation of nitric oxide (NO). [Copyright &y& Elsevier]

Abstract: We report the fabrication of stable Au nanoparticle/polyoxometallate modified glassy carbon electrodes using layer-by-layer (LbL) assembly. These hybrid films were formed by the sequential deposition of poly(diallyldimethylammonium) chloride (PDDA) stabilized Au-nanoparticles (NPs) and transition metal substituted POMs, and were employed as electrocatalysts for the oxygen reduction reaction (ORR). The LbL approach allows the film thickness, metal NP and POM to be varied systematically in order to optimize catalyst performance. Rotating electrode measurements were used to study ORR kinetics at a series of GC/{M-POM/Au-NP} n (M=Ru, Co, W) electrodes. POM co-catalysts containing more labile M–O bonds were found to be better ORR co-catalysts than POMs containing more stable M–O bonds. [Copyright &y& Elsevier]

Abstract: In this paper, the gold nanorods (GNRs)/multiwalled carbon nanotubes (CNT) composite film-modified glassy carbon (GC) electrode was fabricated simply by the electrostatic interaction between the positively charged GNRs and the negatively charged CNT. And the GNRs/CNT/GC electrode was used for the selective and sensitive determination of dopamine (DA) in the presence of ascorbic acid (AA). It was found that the GNRs/CNT/GC electrode had higher catalytic activity towards the oxidation of DA and ascorbic acid (AA) comparing with the bare GC and CNT/GC electrodes. It may be due to the synergic effect of GNRs and CNT, because the surface area of the GNRs/CNT/GC electrode increased, the edge plan sites presented on the CNT surface can improve the electron transfer between the modified electrode and DA, and the rod-shaped gold may be served as the mediator for the oxidation of dopamine and provided the electrocatalytic ability. Moreover, the voltammetric peaks of AA and DA were separated enough at the GNRs/CNT/GC electrode, which was sufficiently enough for the selective determination of DA. Thus, the selective determination of DA was carried out with low detection limit (0.8nM, S/N=3). Also it was obtained that the proposed method was feasible to detect the concentration of DA in human blood serum. Therefore, it can be concluded that the GNRs/CNT modified electrode may be advantageous for the DA determination. [Copyright &y& Elsevier]

Abstract: The phosphate adsorption characteristics and its effect on oxygen reduction reaction (ORR) were examined for various carbon-supported catalysts (Pt/C, Pt3Co/C, PtCo/C, and Aucore–Ptshell/C). Using cyclic voltammetry (CV) and the addition of phosphoric acid, the degree of phosphate adsorption for each catalyst was evaluated based on the intensity of the phosphate adsorption peaks (0.25–0.3V and 0.5–0.65V) and on the decrease in the platinum oxidation current (0.9V). In the N2O reduction technique, the surface structures were analyzed using N2O as an electrochemical probe, which showed that as the Co content increased, (i) steps or defects were introduced by surface reconstruction, (ii) the phosphate adsorbed more strongly compared to Pt/C with a preference for the terrace sites, and (iii) the potential of zero total charge (PZTC) shifted to negative potentials. In the case of the Aucore–Ptshell/C, the phosphate adsorption was found to be weaker than other catalysts, including Pt/C catalyst. The relative ORR activity with PA addition, normalized by that with no phosphate adsorption, was significantly smaller for Co containing alloy catalysts (PtCo/C: 18.2%) and larger for Aucore–Ptshell (30.2%) compared with the Pt/C catalyst (27.8%), confirming the phosphate adsorption characteristics of each catalyst, as measured by CV and N2O reduction analysis. [Copyright &y& Elsevier]

Abstract: Au/MWCNTs catalysts were synthesised by chemical reduction and tested as anode electrodes in a glucose microfluidic fuel cell as a function of time at different temperatures. Physicochemical characterisation of Au/MWCNTs showed an average particle size of approximately 4nm with high dispersion among the MWCNTs support. The use of MWNTCs as support provides chemical stability and good performance for microfluidic fuel cells. The maximum power density reached with Au/MWCNTs was 0.28mWcm−2. Chronoamperometric testing (4h) at three operating temperatures (15, 25 and 35°C) demonstrated that the use of Au/MWCNTs as anode electrodes showed better stability compared with that of Au/C. [Copyright &y& Elsevier]

Abstract: Three-way data obtained from different pulse heights of differential pulse voltammetry (DPV) was analyzed using multivariate curve resolution by alternating least squares (MCR-ALS) algorithm. Differential pulse voltammograms of tryptophan were recorded at a gold nanoparticles decorated multiwalled carbon nanotube modified glassy carbon electrode (GCE/MWCNTs-nanoAu). The determination of tryptophan was performed even in the presence of unexpected electroactive interference(s). Both the simulated and experimental data were non-bilinear. Therefore a potential shift algorithm was used to correct the observed shift in the data. After correction, the data was augmented and MCR-ALS was applied to the augmented data. A relative error of prediction of less than 8% for the determination of the simulated analyte of interest and tryptophan in synthetic samples indicated that the methodology employing voltammetry and second-order calibration could be applied to complex analytical systems. [Copyright &y& Elsevier]

Abstract: Our studies are focused on the stability of the unreconstructed Au(100) surface against potential-induced reconstruction in a solution containing products of tyramine (T) electro-oxidation. It is demonstrated by cyclic voltammetry and capacity measurements that in the presence of T, which reduces the stability of the reconstructed Au(100) surface, the potential-induced surface reconstruction is a fast process on condition that a preceding positive going scan is performed to potentials from the double layer region. Further extension of this scans to the potential region where the oxidation of T takes place, causes a considerable slow down of the potential-induced reconstruction. Kinetics of the potential-induced reconstruction in a solution containing products of T electro-oxidation is investigated. Inhibition of this process is explained by a strong adsorption of species produced during T oxidation on the gold surface. [Copyright &y& Elsevier]

Abstract: In this report, we use stripe-patterned substrates and TEM grids as working electrodes to demonstrate that electrochemically evolved hydrogen bubbles can serve as templates and reducing agents for electroless deposition of Au from a Na3Au(SO3)2 electrolyte to form hollow particles. This new hollow nanoparticle formation mechanism, which is termed as bubble template synthesis, has the potential to become a general route to the fabrication of various metallic hollow nanoparticles. We have also found that the addition of Ni2+ ions in the electrolyte has an effect on the particle formation process. Electrodeposited metallic Ni enhances the hydrogen evolution and therefore the hollow particle formation. It also leads to an improved size distribution of the hollow particles. [Copyright &y& Elsevier]

Abstract: The electrochemical oxidation of aqueous Cr(III) was examined using cyclic voltammetry with a polycrystalline Au electrode in KOH solutions of varying pH and Cr(III) concentration. The mechanism and kinetics for the oxidation of Cr(III) is a quasi-reversible diffusion-controlled reaction and is largely dependent on the solution pH. The reaction mechanism is initiated by an irreversible electrochemical electron transfer to form Cr(IV) which is the rate-determining step (RDS). Following the RDS, subsequent oxidation of Cr to its hexavalent state occurs by the disproportionation of Cr(IV) at low KOH concentrations and electron transfer at high KOH concentrations due to the involvement of OH− in the disproportionation reaction. As the solution pH increases, the Cr(III) oxidation peak potential shifts negatively owing to the involvement of OH− in the RDS. The competitive adsorption of OH− and CrO2 − on the electrode surface also plays an important role in the oxidation behavior. [Copyright &y& Elsevier]

Abstract: The electrochemical characteristics of polycrystalline Au in LiClO4 electrolyte solutions containing 3-mercaptopropionic acid (MPA) or meso-2,3-dimercaptosuccinic acid (DMSA) were studied with linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) over a wide range of positive potentials vs. Ag/AgCl. The EIS data exhibited linear capacitive behaviour at 0.0V with either MPA or DMSA added directly to the electrolyte suggesting the formation of an adsorbed layer of the alkylthiol on the electrode surface. Above this potential, a single well-defined impedance loop appeared for electrolyte solutions containing DMSA or MPA, an observation indicative of a charge transfer reaction that could be related to several processes including oxidative desorption, oxidation of the alkylthiol, or Au oxidation/dissolution. To test for Au dissolution, the electrode was held at 0.8V vs. Ag/AgCl for 12h in electrolytes containing MPA or DMSA followed by surface analysis with Atomic Force Microscopy and solution analysis with Atomic Absorption Spectroscopy. When the electrolyte contained MPA, the extended potential holding procedure resulted in significant roughening of the electrode with no detectable quantities of Au in the electrolyte. X-ray photoelectron spectroscopy (XPS) analysis of the Au surface revealed an additional species in the Au 4f7/2 spectrum indicating the presence of an insoluble electrochemically generated Au(I)–MPA species. When the electrolyte contained DMSA, the Au electrode appeared smoother, 56.6±9.6ppb of Au was detected in the electrolyte and the XPS analysis displayed a single species in the Au 4f7/2 spectrum indicative of metallic Au after the potential holding procedure. Both observations with MPA and DMSA support the charge transfer resistance to be at least partially related to the corrosion of Au, but also suggest that an electrochemically generated Au–DMSA species is soluble and of potential industrial relevance. [Copyright &y& Elsevier]

Abstract: In an attempt to provide an insight into detection of specific viruses in biological samples, we report on quantitation of influenza A virus (IAV) in samples containing large amounts of extraneous bovine serum albumin (BSA), foetal bovine serum (FBS) and hepatitis B virus (HBV) vaccine. Detection was carried out using electrochemical impedance spectroscopy (EIS) with an antibody-neutravidin-thiol architecture immobilized on the surface of an Au electrode. A linear response of the EIS signal was observed for IAV concentrations ranging from 0 to almost 64ng/mL. However, saturation of the EIS response was recorded for greater concentrations and only a 6% increase in signal occurred when the IAV concentration increased to 128ng/mL. The limit of detection, determined at 8ng/mL, remained relatively unaffected by the environment composed of 50ng/mL of HBV and 12.5% of FBS. [Copyright &y& Elsevier]

Abstract: A novel electrochemical immunosensor based on gold–hydroxyapatite nanocomposite–chitosan film has been developed for the detection of prostate-specific antigen. The large surface area of the gold–hydroxyapatite nanocomposite and the porous morphology of chitosan allowed high antibody loading without the loss of bioactivity. The stepwise modification of the electrode was characterized with cyclic voltammetry. Different parameters, including the pH of a supporting electrolyte, the size of the gold nanoparticles, and the antibody concentration were optimized. Under the optimal conditions, the electrochemical immunosensor reliably detected prostate-specific antigen at concentrations from 3.5 to 30ng/mL with a detection threshold of 2.6ng/mL. The prepared biosensor was used to assay prostate-specific antigen in human serum samples, and the results were in good agreement with those obtained by enzyme-linked immunosorbent assays. The reported immunosensor exhibits rapid detection, good reproducibility, high sensitivity, specificity, and stable performance. The proposed strategy can be extended for the development of other biosensors. [Copyright &y& Elsevier]

Abstract: A simple and sensitive DNA impedance sensor was prepared for the detection of chronic lymphocytic leukemia. The DNA electrochemical biosensor is worked based on the electrochemical impedance spectroscopic (EIS) detection of the sequence-specific DNA related to chronic lymphocytic leukemia. The ssDNA probe was immobilized on the surface of the gold nanoparticles. Compared to the bare gold electrode, the gold nanoparticles-modified electrode could improve the density of the probe DNA attachment and hence the sensitivity of the DNA sensor greatly. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy were performed in a solution containing 1.0mmolL−1 K3[Fe(CN)6]/K4[Fe(CN)6] and 50mmolL−1 phosphate buffer saline pH 6.87 plus 50mmolL−1 KCl. In the CV studied, the potential was cycled from 0.0 to +0.65V with a scan rate of 50mVs−1. Using EIS, the difference of the electron transfer resistance (ΔR et) was linear with the logarithm of the complementary oligonucleotides sequence concentrations in the range of 7.0×10−12–2.0×10−7 molL−1, with a detection limit of 1.0×10−12 molL−1. In addition, the DNA sensor showed a good reproducibility and stability during repeated regeneration and hybridization cycles. [Copyright &y& Elsevier]

Abstract: A K6P2MoW17O62-based film decorated by gold nanoparticles was prepared by layer-by-layer self-assembly method. It was fabricated on quartz, silicon and ITO substrates in a progressive and uniform manner monitored by UV–vis spectroscopy, and characterized by atomic force microscopy (AFM), cyclic voltammograms (CVs) and electrochemical impedance spectra (EIS). A set of experimental results revealed that the incorporation of Au nanoparticles into K6P2MoW17O62-based film enhanced the conductivity of the film, leading to several or more than tenfold increase in electrocatalytic efficiency of this film for reduction of H2O2, IO3 −, NO2 − compared to the no use of Au nanoparticles. It also has been found that presence of Au nanoparticles endowed the film electrocatlytic activity towards oxidation of ascorbic acid and the photo-luminescence property arising from inter electron transitions between occupied 5d bands to 6sp conduction bands of AuNPs. [Copyright &y& Elsevier]

Abstract: In this study, a hybrid nanocomposite consisting of a conducting polymer and gold nanoparticles (AuNPs) is fabricated onto a screen-printed carbon electrode (SPCE). A thin layer of poly(3,4-ethylenedioxythiophene) (PEDOT) is coated electrochemically on a bare SPCE; then, the nano-sized AuNPs are embedded by electrochemical deposition. The resultant SPCE/PEDOT/AuNPs-modified electrode is characterized by electrochemical methods, field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The SPCE/PEDOT/AuNPs-modified electrode possesses great catalytic activity for the oxidation of cysteine in various pH buffer solutions (pH 2.0–8.0). The selectivity of the method is demonstrated by the separation of the oxidation peaks at up to 240mV for cysteine and glutathione in pH 6.0 buffer solutions. The effects of the oxidizable interferences are also investigated. Flow-injection amperometry is performed for 0.5–200μM of cysteine in pH 4.0 buffer solutions, and a linear calibration plot with a slope of 0.115μA/μM is obtained. The detection limit (S/N =3) is 0.05μM. Additionally, the proposed methods obtain satisfactory results in the detection of cysteine-containing medicine samples. [Copyright &y& Elsevier]

Abstract: Au nanoparticle (AuNP) multilayer films were fabricated by combining interfacial assembly and layer-by-layer assembly. The key point is that the procedure does not require assistance of organic linker molecules, thus providing a suitable platform for the modification of biological molecules. Direct electron transfer can easily take place between a glassy carbon electrode and horseradish peroxidase (HRP) molecules adsorbed on AuNP films. The current density of direct electron transfer was closely related to the layer number, m, and reached a maximum value for m =4. The optimized HRP/AuNP multilayer film had a relatively rapid response and satisfactory selectivity for H2O2 detection. The linear range and the detection limit were 9.8×10−6 to 6×10−3 mol/L and ∼4.9×10−6 mol/L (S/N =3), respectively. [Copyright &y& Elsevier]

Abstract: Electrochemical (EC) quantification of 11-Mercaptoundecylferrocene (thiolated-ferrocene substrate, Fc-SH) onto gold nanoparticles (AuNPs) was carried out through cyclic voltammetric (CV) investigations in different base electrolyte aqueous media on glassy carbon (GC) electrode. The electrochemical data including peak current, peak potential values revealed the Fc-SH–AuNPs redox system to be adsorption controlled in terms of self assembled monolayers (SAMs). The electrochemically generated SAMs were found quite stable as these maintained the redox activity upto 3 months after repeated CV scans at 298K. The overall output of this research can be utilized in two ways: application of electroactivity and stability of these SAMs in detection of biologically important molecules and also towards the development of EC biosensors. [Copyright &y& Elsevier]

Abstract: We wish to report a simple and new strategy for the fabrication of gold nanoparticles-conducting polymer film on glassy carbon (GC) and indium tin oxide (ITO) surfaces using 5-amino-2-mercapto-1,3,4-thiadiazole capped gold nanoparticles (AMT-AuNPs) in 0.01M H2SO4 by electropolymerization. The presence of amine groups on the surface of the AuNPs was responsible for the deposition of the AMT-AuNPs film on the electrode surface. The atomic force microscopy (AFM) studies reveal that the fabricated p-AMT-AuNPs film showed homogeneously distributed AuNPs with a spherical shape of ∼8nm diameter. The XPS spectrum shows the binding energies at 83.8 and 87.5eV in the Au 4f region corresponding to 4f7/2 and 4f5/2, respectively. The position and difference between these two peaks (3.7eV) exactly match the value reported for Au0. The N1s XPS showed three binding energies at 396.7, 399.6 and 403.3eV, corresponding to the 13;NH– and –N+H–, respectively, confirming that the electropolymerization proceeded through the oxidation of –NH2 groups present on the periphery of the AMT-AuNPs. The application of the present p-AMT-AuNPs modified electrode was demonstrated by studying the electro reduction of oxygen at pH 7.2. The p-AMT-AuNPs film enhanced the oxygen reduction current more than three times than that of p-AMT film prepared under identical conditions. [Copyright &y& Elsevier]

Abstract: A novel electrochemical sensing interface, electrodeposition of gold–platinum alloy nanoparticles (Au–PtNPs) on carbon nanotubes, was proposed and used to fabricate a label-free amperometric immunosensor. On the one hand, the multiwalled carbon nanotubes (MWCNTs) could increase active area of the electrode and enhance the electron transfer ability between the electrode and redox probe; on the other hand, the Au–PtNPs not only could be used to assemble biomolecules with bioactivity kept well, but also could further facilitate the shuttle of electrons. In the meanwhile, horseradish peroxidase (HRP) instead of bovine serum albumin (BSA) was employed to block the possible remaining active sites and avoid the nonspecific adsorption. With the synergetic catalysis effect of Au–PtNPs and HRP towards the reduction of hydrogen peroxide (H2O2), the signal could be amplified and the sensitivity could be enhanced. Using alpha-fetoprotein (AFP) as model analyte, the fabricated immunosensor exhibited two wide linear ranges in the concentration ranges of 0.5–20ngmL−1 and 20–200ngmL−1 with a detection limit of 0.17ngmL−1 at a signal-to-noise of 3. Moreover, the immunosensor exhibited good selectivity, stability and reproducibility. The developed protocol could be easily extended to other protein detection and provided a promising potential in clinical diagnosis application. [Copyright &y& Elsevier]

Abstract: Quantum dots (QD) immobilised on electrodes show a light-triggered current depending on the applied potential. In this study it is investigated whether multiple layers of QD can be formed on electrodes and used for an enhanced photocurrent generation. Therefore multilayers of QD and the redox protein cytochrome c (cyt c) are constructed verified by quartz crystal microbalance (QCM) measurements. The voltammetric investigation of these multilayer assemblies shows no enhancement of the redox signal from cyt c in contrast to multilayers of cyt c and polyelectrolytes or gold nanoparticles. But photocurrent measurements reveal a slight enhancement of the signal which is depending on the number of deposited QD layers. In a second step QD multilayers with a positively charged polyelectrolyte are built up verified by QCM. Chronoamperometric investigations reveal an increase of the photocurrent which is proportional to the number of deposited layers. This indicates an efficient electron transfer between the QD layers. At an electrode with 5 bilayers (QD and polyallylamine) the light-induced current is increased about 5 times compared to a monolayer. [Copyright &y& Elsevier]

Abstract: A sensitive electrochemical method for the detection of avian influenza virus (AIV) H5N1 gene sequence using a DNA aptamer immobilized onto a hybrid nanomaterial-modified electrode was developed. To enhance the selectivity and sensitivity, the modified electrode was assembled with multi-wall carbon nanotubes (MWNT), polypyrrole nanowires (PPNWs) and gold nanoparticles (GNPs). This electrode offered a porous structure with a large effective surface area, highly electrocatalytic activities and electronic conductivity. Therefore, the amount of DNA aptamer immobilized onto the electrode was increased while the accessibility of the detection target was maintained. The biosensor is based on the hybridization and preferred orientation of a DNA aptamer immobilized onto a modified electrode surface with its target (H5N1 specific sequence) present in solution. It is selective for the H5N1 specific sequence, and the signal of the indicator was approximately linear to log(concentration) of the H5N1 specific sequence from 5.0×10−12 to 1.0×10−9 M (R =0.9863) with a detection limit of 4.3×10−13 M. These studies showed that the new hybrid nanomaterial (MWNT/PPNWs/GNPs) and the DNA aptamer could be used to fabricate an electrochemical biosensor for gene sequence detection. Furthermore, this design strategy is expected to have extensive applications in other biosensors. [Copyright &y& Elsevier]

Abstract: A new ionic liquid–polymer electrolyte was successfully tested in the planar amperometric solid-state sensor sensitive towards nitrogen dioxide. The electrolyte consists of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6) and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) in the ratio 57:43mol.% and exhibits ionic conductivity 1.6×10−4 Scm−1 at 20°C, high electrochemical stability (over 4V on gold or glassy carbon) and thermal stability (over 230°C). The analyte, gaseous nitrogen dioxide in air, was determined using the electrochemical reduction at −900mV vs. Pt/air on gold minigrid indicating electrode with Pt/air as a reference electrode. The sensor response is linear in the NO2 concentration range 0.3–1.1ppm and is reproducible and long-term stable. [Copyright &y& Elsevier]

Abstract: Highly ordered Pt and Pd decorated Au nanowire arrays, Pt/Au NWA and Pd/Au NWA, are prepared by anodized aluminum oxide (AAO) template based electrodeposition combined with chemical reduction. The effect of shell material on the ethanol oxidation currents is studied. The maximum current densities are several times higher on the modified electrodes than on the unmodified Pt (Pd) NWA. The most highly active electrode shows almost 4-fold increase in the ethanol peak current. Pt/Au and Pd/Au NWA electrodes show a similar dependence of the ethanol oxidation current density on the Pd or Pt deposition time, which most likely, reflects the optimal upper layer thickness. The synergistic effect between substrate and deposit materials seems to be the most important factor explaining such unusually high activity. [Copyright &y& Elsevier]

Abstract: A highly sensitive immunosensor based on immobilization of specific monoclonal antibodies onto gold nanoparticles (GNPs) attached to a modified gold electrode was developed for the determination of the presence of doxorubicin. Colloidal GNPs were coated on a gold electrode using the thiol groups of 1,6-hexanedithiol (HDT) as a cross-linker. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed for characterization of the various layers that were coated onto the electrode. The relative charge transfer resistance of the antibody-modified gold electrode changed linearly with the concentration of doxorubicin. The limit of detection (3sb/m) was 0.83pgmL−1, and a linear range was obtained from 1.0 to 160.0pgmL−1 of doxorubicin. The affinity of doxorubicin for the immobilized antibody was determined to be 1.74×1011 M−1. The sensitivity and specificity of the immunosensor was validated using doxorubicin-spiked human serum samples, and the results show that the immunosensor is a useful tool for screening picogram amounts of doxorubicin in the clinical laboratory. [Copyright &y& Elsevier]

Abstract: An electrochemical sensor based on gold nanoparticles (GNPs)/multiwalled carbon nanotubes (MWCNTs)/poly (1,5-naphthalenediamine) films modified glassy carbon electrode (GCE) was fabricated. The effectiveness of the sensor was confirmed by sensitive detection of cellobiose dehydrogenase (CDH) gene which was extracted from Phanerochaete chrysosporium using polymerase chain reaction (PCR). The monomer of 1,5-naphthalenediamine was electropolymerized on the GCE surface with abundant free amino groups which enhanced the stability of MWCNTs modified electrode. Congo red (CR)-functionalized MWCNTs possess excellent conductivity as well as high solubility in water which enabled to form the uniform and stable network nanostructures easily and created a large number of binding sites for electrodeposition of GNPs. The continuous GNPs together with MWCNTs greatly increased the surface area, conductivity and electrocatalytic activity. This electrode structure significantly improved the sensitivity of sensor and enhanced the DNA immobilization and hybridization. The thiol modified capture probes were immobilized onto the composite films-modified GCE by a direct formation of thiol–Au bond and horseradish peroxidase–streptavidin (HRP–SA) conjugates were labeled to the biotinylated detection probes through biotin–streptavidin bond. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to investigate the film assembly and DNA hybridization processes. The amperometric current response to HRP-catalyzed reaction was linearly related to the common logarithm of the target nucleic acid concentration in the range of 1.0×10−15–1.0×10−10 M, with the detection limit of 1.2×10−16 M. In addition, the electrochemical biosensor exhibited high sensitivity, selectivity, stability and reproducibility. [Copyright &y& Elsevier]

Abstract: Gold electrodes were functionalized with an electropolymerized matrix of Au nanoparticles modified with 2-mercaptoethanesulfonic acid, 3-mercaptophenyl boronic acid and p-aminothiophenol. The resulting nanostructured electroconductive matrix was used as support for the oriented immobilization of horseradish peroxidase to construct a reagentless amperometric biosensor for H2O2. The electrode, poised at 0.0mV, exhibited a rapid response within 8s and a linear calibration range from 5μM to 1.1mM H2O2. The sensitivity of the biosensor was determined as 498μA/Mcm2, and its detection limit was 1.5μM H2O2 at a signal-to-noise ratio of 3. The electrode retained 95% and 72% of its initial activity after 21 and 40 days of storage at 4°C. [Copyright &y& Elsevier]

Abstract: A nano-structured Ni (II)/ACDA (2-amino-1-cyclopentene-1-dithiocarboxylic acid) film was electrodeposited on a gold nanoparticle–cysteine–gold electrode. The formation of Ni (II)/ACDA film and electrocatalytic oxidation of tryptophan on the surface of the modified electrode were investigated with cyclic voltammetric and chronoamperometric techniques. The hydrodynamic amperometry at rotating modified electrode was used for determination of tryptophan in the range of 0.085–43.0μmoll−1. The detection limit was found to be 23nmoll−1. The rate constant, transfer coefficient for the catalytic reaction and the diffusion coefficient of tryptophan in the solution were found to be 9.1×102 M−1 S−1, 0.52 and 1.09×10−5 cm2 s−1 respectively. It is worth noting that the as formed matrix in our work possesses a 3D porous network structure with a large effective surface area and high catalytic activity and behaves like microelectrode ensembles. The modified electrode indicated reproducible behavior and a high level stability during the experiments, making it particularly suitable for the analytical purposes. [Copyright &y& Elsevier]

Abstract: Taking advantage of the spontaneous deposition of noble metals on polymers containing sulphur, the inclusion of gold and platinum in poly(3-methylthiophene) and poly(3,4-ehylenedioxythiophene) (PEDOTh) layers, achieved by immersion of the polymer into the metal nanoparticles suspension, is reported in the present work. Platinum and gold nanoparticles (NPs), with diameters between 3 and 17nm, have been prepared from colloidal methods (citrate or borohydride reduction in the presence of citrate capping agent) and characterized by transmission electron microscopy, ultraviolet–visible spectrophotometry and X-ray diffraction (XRD). The electropolymerization was carried out under potentiostatic and potentiodynamic conditions, imparting distinct morphologies, as revealed by atomic force microscopy. After polymer films immersion in the colloidal solutions, evidence of the NPs confinement and distribution was provided by XRD analysis and scanning electron microscopy. For thin layers, the quantity of attached metal NPs could be estimated from quartz crystal microbalance data collected throughout the films immersion.The influence of the polymer type and morphology, NPs nature, size and incorporated amount on the electrocatalytic activity of the so-prepared modified electrodes towards the hydrazine oxidation, in phosphate buffer solution, has been investigated by cyclic voltammetry. The results clearly show the superior properties of potentiodynamically prepared PEDOTh films attaching very small (3nm) freshly prepared Pt-NPs. [Copyright &y& Elsevier]

Abstract: Substitution of a metal center of phosphomolybdate, PMo12O40 3− (PMo12), or its tungsten analogue with dirhodium(II) and subsequent stabilization of gold nanoparticles, AuNPs, with Rh2PMo11 are demonstrated. The AuNP-Rh2PMo11 mediates oxidations but adsorbs too weakly for direct modification of electrode materials. Stability in quiescent solution was achieved by modifying glassy carbon (GC) with 3-aminopropyltriethoxysilane (APTES) and then electrostatically assembling AuNP-Rh2PMo11. At GC|APTES|AuNP-Rh2PMo11, cyclic voltammetry showed the expected set of three reversible peak-pairs for PMo11 in the range −0.2 to 0.6 vs. (Ag/AgCl)/V and the reversible RhII,III couple at 1.0 vs. (Ag/AgCl)/V. The presence of AuNPs increased the current for the reduction of bromate by a factor of 2.5 relative to that at GC|Rh2PMo11, and the electrocatalytic oxidation of methionine displayed characteristics of synergism between the AuNP and RhII. To stabilize AuNP-Rh2PMo11 on a surface in a flow system, GC was modified by electrochemically assisted deposition of a sol–gel with templated 10-nm pores prior to immobilizing the catalyst in the pores. The resulting electrode permitted determination of bromate by flow-injection amperometry with a detection limit of 4.0×10−8 moldm−3. [Copyright &y& Elsevier]

Abstract: Different Au/Pt bimetallic systems have been synthesised by following the approach suggested by Brust. The nanoparticles have been anchored to glassy carbon surface through a place-exchange reaction involving dithiol molecules. The resulting modified electrode consists of heterogeneous nanostructured Au and Pt patchwork. The different nanoparticles systems developed have been employed for the electroxidation of methanol and carbon monoxide in alkaline aqueous media. The results show that the electrocatalytic activity of the bimetallic systems is enhanced with respect to the single monometallic NP systems. [Copyright &y& Elsevier]

Abstract: A composite material was prepared from graphene and palladium nanoparticles (PdNP) by layer-by-layer deposition on gold electrodes. The material was characterized by absorption spectroscopy, scanning electron microscopy, Raman spectroscopy and surface plasmon resonance. Cyclic voltammetry demonstrated the presence of electrocatalytic centers in the palladium decorated graphene. This material can serve as a sensor material for hydrogen at levels from 0.5 to 1% in synthetic air. Pure graphene is poorly sensitive to hydrogen, but incorporation of PdNPs increases its sensitivity by more than an order of magnitude. The effects of hydrogen, nitrogen dioxide and humidity were studied. Sensor regeneration is accelerated in humid air. The sensitivity of the nanocomposite depends on the number of bilayers of graphene–PdNPs. [Copyright &y& Elsevier]

Abstract: The layer-by-layer adsorption technique was used to prepare polyaniline (PANI)–gold nanoparticles (AuNP) multilayered structures with different AuNP/PANI ratios. By means of microgravimetric measurements it was found that the amount of the adsorbed species depends on the duration of the AuNP adsorption step. At fixed adsorption step durations the amount of both (PANI and AuNP) materials increases linearly with the number of adsorption steps. Two types of PANI–AuNP multilayered nanocomposites with different AuNP/PANI ratio were studied as electrocatalytic materials for dopamine and uric acid oxidation. The sensitivity of PANI–AuNP for dopamine oxidation was found to depend on type of the nanocomposite whereas for uric acid oxidation the sensitivity remained unaffected by the type of the nanocomposite structure. This result is discussed in terms of the different limitations for both oxidation reactions. By means of differential pulse voltammetry experiments linear concentration dependences of the anodic peak currents were observed for both dopamine and uric acid in the concentration ranges 7–148μmoldm−3 and 29–720μmoldm−3, respectively. In the presence of both analytes no interference effects were detected. [Copyright &y& Elsevier]

Abstract: Composite materials consisting of poly(3,4-ethylenedioxythiophene) including Au nanoparticles, encapsulated by citrate anions, have been firmly deposited on an electrode surface through a simple method, taking advantage of the interaction between Au metal and thiophene polymeric backbone. A series of similar electrode coatings, also including different amounts of nanoparticles inside, has been characterised in terms of thickness and surface morphology, through different microscopic techniques. The electrocatalytic properties have been studied with respect to the oxidation of glucose in alkaline media, which is prevented from occurring on the pure organic material. [Copyright &y& Elsevier]

Abstract: In the present study, gold/surfactant core/shell colloidal nanoparticles with a controlled morphology and chemical composition have been obtained via the so-called sacrificial anode technique, carried out in galvanostatic mode. As synthesized Au-NPs had an average core diameter comprised between 4 and 8nm, as a function of the electrochemical process experimental conditions. The UV–Vis characterization of gold nanocolloids showed clear spectroscopic size effects, affecting both the position and width of the nanoparticle surface plasmon resonance peak. The nanomaterial surface spectroscopic characterization showed the presence of two chemical states, namely nanostructured Au(0) (its abundance being higher than 90%) and Au(I). Au-NPs were then deposited on the top of a capacitive field effect sensor and subjected to a mild thermal annealing aiming at removing the excess of stabilizing surfactant molecules. Au-NP sensors were tested towards some gases found in automotive gas exhausts. The sensing device showed the largest response towards NO x , and much smaller – if any – responses towards interferent species such as NH3, H2, CO, and hydrocarbons. [Copyright &y& Elsevier]

Abstract: A novel platform, which hemoglobin (Hb) was immobilized on core–shell structurally Fe3O4/Au nanoparticles (simplified as Fe3O4@Au NPs) modified glassy carbon electrode (GCE), has been developed for fabricating the third biosensors. Fe3O4@Au NPs, characterized using transmission electron microscope (TEM), scanning electron microscope (SEM) and energy dispersive spectra (EDS), were coated onto GCE mediated by chitosan so as to provide larger surface area for anchoring Hb. The thermodynamics, dynamics and catalysis properties of Hb immobilized on Fe3O4@Au NPs were discussed by UV–visible spectrum (UV–vis), electrochemical impedance spectroscopy (EIS), electrochemical quartz crystal microbalance technique (EQCM) and cyclic voltammetry (CV). The electrochemical parameters of Hb on Fe3O4@Au NPs modified GCE were further carefully calculated with the results of the effective working area as 3.61cm2, the surface coverage concentration (Γ) as 1.07×10−12 molcm−2, the electron-transfer rate constant (K s ) as 1.03s−1, the number of electron transferred (n) as 1.20 and the standard entropy of the immobilized Hb (ΔS 0′) as calculated to be −104.1Jmol−1 K−1. The electrocatalytic behaviors of the immobilized Hb on Fe3O4@Au NPs were applied for the determination of hydrogen peroxide (H2O2), oxygen (O2) and trichloroacetic acid (TCA). The possible functions of Fe3O4 core and Au shell as a novel platform for achieving Hb direct electrochemistry were discussed, respectively. [Copyright &y& Elsevier]

Abstract: Two layers of cationic iron(III) meso-tetrakis (N-methylpyridinum-4-yl)porphyrin (FeTMPyP) and anionic gold nanoparticles (GNPs) were alternately assembled on a poly(diallyldimethylammonium chloride)-wrapped carbon nanotube (PDDA-CNT)-modified electrode via electrostatic interactions. The porphyrin-functionalized gold nanoparticles were characterized by scanning electron microscopy and UV–vis absorption spectrometry. The (FeTMPyP–GNP)2/PDDA-CNT modified electrode showed two stable and well-defined peaks at −0.112V and −0.154V, which were attributed to the GNP-accelerated redox process of Fe(III)TMPyP/Fe(II)TMPyP. The modified electrode possessed excellent electrocatalytic behavior for the reduction of peroxyacetic acid (PAA). The resulting biosensor exhibited a fast amperometric response to PAA (∼3s), with a wide linear range from 2.5×10−6 M to 1.05×10−3 M and a detection limit of 0.5μM at a signal-to-noise ratio of 3. More importantly, H2O2 did not interfere with the detection. Thus, this biosensor enabled highly sensitive detection of PAA without removing H2O2 and showed a promising potential in practical applications. [Copyright &y& Elsevier]