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Sample records for electrochemical modified gold

  1. Electrochemical growth of two-dimensional gold nanostructures on a thin polypyrrole film modified ITO electrode.

    PubMed

    Li, Yin; Shi, Gaoquan

    2005-12-22

    Two-dimensional gold nanostructures have been fabricated by electrochemical deposition of gold nanoparticles onto indium tin oxide (ITO) glass substrate modified with thin polypyrrole film. By controlling the electrodeposition conditions, gold nanoparticles with dendritic rod, sheet, flower-like (consisting of staggered nanosheets), and pinecone-like structures were generated. The flower-like gold nanoparticles showed high catalytic activity on electrochemical reduction of oxygen, and its activity was measured to be approximately 25 times that of gold pinecones and 10(4) times that of gold nanosheets in terms of gold weight. The pinecone-like nanoparticles can form a compact film with nano-/microscale binary structure like a lotus leaf surface. After modification with n-dodecanethiol, the surface showed superhydrophobic properties with a water contact angle of 153.4 degrees and a tilt angle of 4.4 degrees (5 microL droplet).

  2. Electrochemical Determination of Food Preservative Nitrite with Gold Nanoparticles/p-Aminothiophenol-Modified Gold Electrode

    PubMed Central

    Üzer, Ayşem; Sağlam, Şener; Can, Ziya; Erçağ, Erol; Apak, Reşat

    2016-01-01

    Due to the negative impact of nitrate and nitrite on human health, their presence exceeding acceptable levels is not desired in foodstuffs. Thus, nitrite determination at low concentrations is a major challenge in electroanalytical chemistry, which can be achieved by fast, cheap, and safe electrochemical sensors. In this work, the working electrode (Au) was functionalized with p-aminothiophenol (p-ATP) and modified with gold nanoparticles (Au-NPs) to manufacture the final (Au/p-ATP-Aunano) electrode in a two-step procedure. In the first step, p-ATP was electropolymerized on the electrode surface to obtain a polyaminothiophenol (PATP) coating. In the second step, Au/p-ATP-Aunano working electrode was prepared by coating the surface with the use of HAuCl4 solution and cyclic voltammetry. Determination of aqueous nitrite samples was performed with the proposed electrode (Au/p-ATP-Aunano) using square wave voltammetry (SWV) in pH 4 buffer medium. Characteristic peak potential of nitrite samples was 0.76 V, and linear calibration curves of current intensity versus concentration was linear in the range of 0.5–50 mg·L−1 nitrite with a limit of detection (LOD) of 0.12 mg·L−1. Alternatively, nitrite in sausage samples could be colorimetrically determined with high sensitivity by means of p-ATP‒modified gold nanoparticles (AuNPs) and naphthylethylene diamine as coupling agents for azo-dye formation due to enhanced charge-transfer interactions with the AuNPs surface. The slopes of the calibration lines in pure NO2− solution and in sausage sample solution, to which different concentrations of NO2− standards were added, were not significantly different from each other, confirming the robustness and interference tolerance of the method. The proposed voltammetric sensing method was validated against the colorimetric nanosensing method in sausage samples. PMID:27490543

  3. Electrochemical Determination of Food Preservative Nitrite with Gold Nanoparticles/p-Aminothiophenol-Modified Gold Electrode.

    PubMed

    Üzer, Ayşem; Sağlam, Şener; Can, Ziya; Erçağ, Erol; Apak, Reşat

    2016-08-02

    Due to the negative impact of nitrate and nitrite on human health, their presence exceeding acceptable levels is not desired in foodstuffs. Thus, nitrite determination at low concentrations is a major challenge in electroanalytical chemistry, which can be achieved by fast, cheap, and safe electrochemical sensors. In this work, the working electrode (Au) was functionalized with p-aminothiophenol (p-ATP) and modified with gold nanoparticles (Au-NPs) to manufacture the final (Au/p-ATP-Aunano) electrode in a two-step procedure. In the first step, p-ATP was electropolymerized on the electrode surface to obtain a polyaminothiophenol (PATP) coating. In the second step, Au/p-ATP-Aunano working electrode was prepared by coating the surface with the use of HAuCl₄ solution and cyclic voltammetry. Determination of aqueous nitrite samples was performed with the proposed electrode (Au/p-ATP-Aunano) using square wave voltammetry (SWV) in pH 4 buffer medium. Characteristic peak potential of nitrite samples was 0.76 V, and linear calibration curves of current intensity versus concentration was linear in the range of 0.5-50 mg·L(-1) nitrite with a limit of detection (LOD) of 0.12 mg·L(-1). Alternatively, nitrite in sausage samples could be colorimetrically determined with high sensitivity by means of p-ATP‒modified gold nanoparticles (AuNPs) and naphthylethylene diamine as coupling agents for azo-dye formation due to enhanced charge-transfer interactions with the AuNPs surface. The slopes of the calibration lines in pure NO₂(-) solution and in sausage sample solution, to which different concentrations of NO₂(-) standards were added, were not significantly different from each other, confirming the robustness and interference tolerance of the method. The proposed voltammetric sensing method was validated against the colorimetric nanosensing method in sausage samples.

  4. Electrochemical Determination of Food Preservative Nitrite with Gold Nanoparticles/p-Aminothiophenol-Modified Gold Electrode.

    PubMed

    Üzer, Ayşem; Sağlam, Şener; Can, Ziya; Erçağ, Erol; Apak, Reşat

    2016-01-01

    Due to the negative impact of nitrate and nitrite on human health, their presence exceeding acceptable levels is not desired in foodstuffs. Thus, nitrite determination at low concentrations is a major challenge in electroanalytical chemistry, which can be achieved by fast, cheap, and safe electrochemical sensors. In this work, the working electrode (Au) was functionalized with p-aminothiophenol (p-ATP) and modified with gold nanoparticles (Au-NPs) to manufacture the final (Au/p-ATP-Aunano) electrode in a two-step procedure. In the first step, p-ATP was electropolymerized on the electrode surface to obtain a polyaminothiophenol (PATP) coating. In the second step, Au/p-ATP-Aunano working electrode was prepared by coating the surface with the use of HAuCl₄ solution and cyclic voltammetry. Determination of aqueous nitrite samples was performed with the proposed electrode (Au/p-ATP-Aunano) using square wave voltammetry (SWV) in pH 4 buffer medium. Characteristic peak potential of nitrite samples was 0.76 V, and linear calibration curves of current intensity versus concentration was linear in the range of 0.5-50 mg·L(-1) nitrite with a limit of detection (LOD) of 0.12 mg·L(-1). Alternatively, nitrite in sausage samples could be colorimetrically determined with high sensitivity by means of p-ATP‒modified gold nanoparticles (AuNPs) and naphthylethylene diamine as coupling agents for azo-dye formation due to enhanced charge-transfer interactions with the AuNPs surface. The slopes of the calibration lines in pure NO₂(-) solution and in sausage sample solution, to which different concentrations of NO₂(-) standards were added, were not significantly different from each other, confirming the robustness and interference tolerance of the method. The proposed voltammetric sensing method was validated against the colorimetric nanosensing method in sausage samples. PMID:27490543

  5. Fabrication of electrochemical DNA sensors on gold-modified recessed platinum nanoelectrodes.

    PubMed

    Salamifar, S Ehsan; Lai, Rebecca Y

    2014-03-18

    We report the use of gold-modified recessed platinum (Pt) nanoelectrodes in the fabrication of linear and stem-loop probe-based electrochemical DNA (E-DNA) sensors. Pt nanoelectrodes with a radius less than 10 nm were reproducibly fabricated using an optimized laser pulling technique. Prior to sensor fabrication, the nanoelectrode was electrochemically etched to create a recessed nanopore, followed by electrodeposition of gold into the nanopore using either cyclic voltammetry or constant potential amperometry. Both techniques enabled controlled deposition of gold into the nanopores, resulting in a nanostructured gold electrode with a well-defined surface area. In addition, we systematically determined the optimal experimental condition for DNA probe immobilization and target interrogation. The electron transfer rate constants of methylene blue, as determined using alternating current voltammetry, were found to be much higher than those obtained from E-DNA sensors fabricated on conventional macroscale electrodes. While this unique phenomenon requires further investigation, our results clearly show that these gold-modified nanoelectrodes can be used as substrates for this class of electrochemical biosensors.

  6. Electrochemical Properties of a Thiol Monolayers Coated Gold Electrode Modified with Osmium Gel Membrane as Enzyme Sensor

    NASA Astrophysics Data System (ADS)

    Yabutani, Tomoki; Okada, Nobuyuki; Maruyama, Kenichi; Motonaka, Junko

    The electrochemical behavior of an enzyme sensor for glucose using a gold electrode modified with thiol self-assembled membrane and osmium complex gel as an electron transferring mediator has further been investigated by electrochemical analysis. The gold electrode was initially coated with aminomethanethiol self assembling mono layer membrane(thiol-SAM) and then immobilized with glucose oxidase using poly(vinylpyridine-co-allylamine) (PVP-co-AA), gel coordinated with osmium bipyridine complexes (GOD/Os-PVP-co-AA gel). The cleaning condition of the surface of the Au electrode prior to coating thiol SAM was optimized for reduction of interference caused by concomitant compounds. It was found that interfering influence was most efficiently reduced in the case of use of the Au electrode immersed into nitric acid. The current ratio with a thiol coated gold electrode modified with Os-PVP-co-AA gel in glucose solution in the presence to absence of ascorbic acid, acetaminophen, and uric acid (ID+I/II) was 1.006, 1.014, and 1.018, respectively. The peak current response of glucose in the electrode modified with thiol SAM was dropped to 60 98% as compared with that without thiol SAM.

  7. Gold nanoparticles modified electrode via a mercapto-diazoaminobenzene monolayer and its development in DNA electrochemical biosensor.

    PubMed

    Li, Feng; Feng, Yan; Dong, Pingjun; Tang, Bo

    2010-05-15

    A novel protocol for the gold nanoparticles (AuNPs) modification on the electrode surface was proposed, which was based on the self-assembly of AuNPs on the mercapto-diazoaminobenzene monolayer modified electrode. The mercapto-diazoaminobenzene monolayer was obtained by covalent immobilization of 4-aminothiophenol (4-ATP) molecules onto another 4-ATP monolayer functionalized gold electrode by diazotization-coupling reaction. The DNA immobilization and hybridization on the AuNPs modified electrode was further investigated. The prepared AuNPs-ATP-diazo-ATP film demonstrated efficient electron transfer ability for the electroactive species toward the electrode surface due to a large conjugated structure of the mercapto-diazoaminobenzene monolayer. The recognition of fabricated electrochemical DNA biosensor toward complementary single-stranded DNA was determined by differential pulse voltammetry with the use of Co(phen)(3)3+ as an electrochemical indicator. A linear detection range for the complementary target DNA was obtained from 3.01 x 10(-10) to 1.32 x 10(-8) M with a detection limit of 9.10 x 10(-11) M. The fabricated biosensor also possessed good selectivity and could be regenerated easily. PMID:20207131

  8. Ultra-trace electrochemical impedance determination of bovine serum albumin by a two dimensional silica network citrate-capped gold nanoparticles modified gold electrode.

    PubMed

    Yari, Abdollah; Saeidikhah, Marzieh

    2015-11-01

    In this work, a gold electrode (GE) was modified by coating with two dimensional silica network/citrate capped gold nanoparticles-poly(diallyldimethylammonium chloride) (GE-TDSN-CGNP-PDDA) for ultra-sensitive determination of Bovine Serum Albumin (BSA). After covalently binding of a silica network (in two-dimensional form) on the surface of a gold electrode, via twice in situ hydrolysis of 3-mercaptopropyl-tri-ethoxysilane, citrate capped gold nanoparticles (CGNP) were chemically adsorbed on the silica cage. Subsequently, PDDA was bonded to CGNP via electrostatic interaction of positively charged polymer and negatively charged stabilizer of CGNP. Analytical properties of GE-TDSN-CGNP-PDDA were studied by Electrochemical Impedance Spectroscopy (EIS). The detection limit for measured BSA was found to be 8.4×10(-13) mol L(-1) and the measuring linear concentration range of the proposed sensor was 9.9×10(-12)-1.6×10(-10) mol L(-1) of BSA. In addition, GE-TDSN-CGNP-PDDA exhibited good stability with high selectivity and was applied for determination of BSA in some samples with satisfactory results.

  9. A Novel Electrochemical Genosensor Based on Banana and Nano-Gold Modified Electrode Using Tyrosinase Enzyme as Indicator.

    PubMed

    Asghary, Maryam; Raoof, Jahan-Bakhsh; Hamidi-Asl, Ezat; Ojani, Reza

    2015-05-01

    The electrochemical behavior of the tyrosinase enzyme at the surface of two electrodes, carbon paste electrode (CPE) and nano-gold modified carbon paste electrode (NGCPE), has been studied by cyclic voltammetry. Tyrosinase showed one oxidation peak (around +0.85 V) and one reduction peak at + 0.40 V versus Ag\\AgCl\\KCl (3 M). To calculate the values of a and k(s), the effect of potential scan rate on the electrochemical properties of tyrosinase was investigated. Cyclic voltammetry and UV-vis absorption techniques were used for the study of interaction between DNA and tyrosinase. The cyclic voltammogram of tyrosinase was obtained in the presence of different types of DNA bases for the study of tyrosinase-DNA binding. The results showed that the hydrogen binding and electrostatic interactions were important interaction mode. Moreover, a variation in tyrosinase signals intensity regarding the interaction to ssDNA and dsDNA was observed. The selectivity of the biosensor was studied using noncomplementary oligonucleotides. Finally, banana modified carbon paste electrode was also prepared to investigate the interaction of banana's tyrosinase with DNA. The limit of detection for DNA probe was calculated 0.33 pM by using the oxidation signal of accumulated tyrosinase in NGCPE. PMID:26504957

  10. IMPACT OF POLYCYCLIC AROMATIC HYDROCARBONS OF THE ELECTROCHEMICAL RESPONSES OF A FERRICYNIDE PROBE AT TEMPLATE-MODIFIED SELF ASSEMBLED MONOLAYERS ON GOLD ELECTRODES

    EPA Science Inventory

    The impact of pyrene on the electrochemical response of the ferricyanide probe using Self Assembled Monolayer (SAM)-modified gold electrodes was investigated using Cyclic Voltammetry (CV) and Square Wave Voltammetry (SWV). These results suggest the feasibility of using SAMs, par...

  11. Electrochemical sensor for nitroaromatic type energetic materials using gold nanoparticles/poly(o-phenylenediamine-aniline) film modified glassy carbon electrode.

    PubMed

    Sağlam, Şener; Üzer, Ayşem; Tekdemir, Yasemin; Erçağ, Erol; Apak, Reşat

    2015-07-01

    In this work, a novel electrochemical sensor was developed for the detection of nitroaromatic explosive materials, based on a gold nanoparticle-modified glassy carbon (GC) electrode coated with poly(o-phenylenediamine-aniline film) (GC/P(o-PDA-co-ANI)-Aunano electrode). Nitroaromatic compounds were detected through their π-acceptor/donor interactions with o-phenylenediamine-aniline functionalities on the modified electrode surface. The enhanced sensitivities were achieved through π-π and charge-transfer (CT) interactions between the electron-deficient nitroaromatic compounds and σ-/π-donor amine/aniline groups linked to gold nanoparticles (Au-NPs), providing increased binding and preconcentration onto the modified GC-electrodes. Selective determination of nitroaromatic type explosives in the presence of nitramines was enabled by o-PDA and reusability of the electrode achieved by Au-NPs. Calibration curves of current intensity versus concentration were linear in the range of 2.5-40mgL(-1) for 2,4,6-trinitrotoluene (TNT) with a detection limit (LOD) of 2.1mgL(-1), 2-40mgL(-1) for 2,4-dinitrotoluene (DNT) (LOD=1.28mgL(-1)), 5-100mgL(-1) for tetryl (LOD=3.8mgL(-1)) with the use of the GC/P(o-PDA-co-ANI)-Aunano electrode. For sensor measurements, coefficients of variation of intra- and inter-assay measurements were 0.6% and 1.2%, respectively (N=5), confirming the high reproducibility of the proposed assay. Deconvolution of current contributions of synthetic (TNT+DNT) mixtures at peak potentials of constituents was performed by multiple linear regression analysis to provide high sensitivity for the determination of each constituent. Determination options for all possible mixture combinations of nitroaromatic explosives are presented in this work. The proposed methods were successfully applied to the analysis of nitroaromatics in military explosives, namely comp B, octol, and tetrytol. Method validation was performed against GC-MS on real post-blast residual samples

  12. Electrochemical characterization and application of azurin-modified gold electrodes for detection of superoxide.

    PubMed

    Shleev, Sergey; Wetterö, Jonas; Magnusson, Karl-Eric; Ruzgas, Tautgirdas

    2006-08-15

    A novel biosensor for superoxide radical (O(2)(*-)) detection based on Pseudomonas aeruginosa azurin immobilized on gold electrode was designed. The rate constant of azurin reduction by O(2)(*-) was found to be 10(5)M(-1)s(-1) in solution and five times lower, i.e., 0.2 x 10(5)M(-1)s(-1), for azurin coupled to gold by 3,3'-dithiobis(sulfosuccinimidylpropionate) (DTSSP). The electron transfer rate between the protein and the electrode ranged from 2 to 6s(-1). The sensitivity of this biosensor to O(2)(*-) was 6.8 x 10(2)Am(-2)M(-1). The response to the interference substances, such as uric acid, H(2)O(2), and dimethylsulfoxide was negligible below 10 microM. The electrode was applied in three O(2)(*-) generating systems: (i) xanthine oxidase (XOD), (ii) potassium superoxide (KO(2)), and (iii) stimulated neutrophil granulocytes. The latter was compared with luminol-amplified chemiluminescence. The biosensor responded to O(2)(*-) in all three environments, and the signals were antagonized by superoxide dismutase.

  13. Fabrication of Highly Sensitive and Stable Hydroxylamine Electrochemical Sensor Based on Gold Nanoparticles and Metal-Metalloporphyrin Framework Modified Electrode.

    PubMed

    Wang, Yang; Wang, Lu; Chen, Huanhuan; Hu, Xiaoya; Ma, Shengqian

    2016-07-20

    This paper describes the immobilization of gold nanoparticles on metal-metalloporphyrin frameworks (AuNPs/MMPF-6(Fe)) through electrostatic adsorption. The composites were characterized by powder X-ray diffraction, zeta potential, transmission electron microscopy, electrochemical impedance spectroscopy, and voltammetric methods. MMPF-6(Fe) exhibited a pair of redox peaks of the Fe(III)TCPP/Fe(II)TCPP redox couple. The AuNPs/MMPF-6(Fe)-based electrochemical sensor demonstrates a distinctly higher electrocatalytic response to the oxidation of hydroxylamine due to the synergic effect of the gold metal nanoparticles and metal-metalloporphyrin matrix. The voltammetric current response exhibits two linear dynamic ranges, 0.01-1.0 and 1.0-20.0 μmol L(-1), and the detection limit was as low as 0.004 μmol L(-1) (S/N = 3). Moreover, the biosensor exhibits high reproducibility and stability in acid solution. Our work not only offers a simple way to achieve the direct electrochemical behavior of metalloporphyrin but also expands the potential applications of MOFs-based composites in bioanalysis.

  14. Fabrication of Highly Sensitive and Stable Hydroxylamine Electrochemical Sensor Based on Gold Nanoparticles and Metal-Metalloporphyrin Framework Modified Electrode.

    PubMed

    Wang, Yang; Wang, Lu; Chen, Huanhuan; Hu, Xiaoya; Ma, Shengqian

    2016-07-20

    This paper describes the immobilization of gold nanoparticles on metal-metalloporphyrin frameworks (AuNPs/MMPF-6(Fe)) through electrostatic adsorption. The composites were characterized by powder X-ray diffraction, zeta potential, transmission electron microscopy, electrochemical impedance spectroscopy, and voltammetric methods. MMPF-6(Fe) exhibited a pair of redox peaks of the Fe(III)TCPP/Fe(II)TCPP redox couple. The AuNPs/MMPF-6(Fe)-based electrochemical sensor demonstrates a distinctly higher electrocatalytic response to the oxidation of hydroxylamine due to the synergic effect of the gold metal nanoparticles and metal-metalloporphyrin matrix. The voltammetric current response exhibits two linear dynamic ranges, 0.01-1.0 and 1.0-20.0 μmol L(-1), and the detection limit was as low as 0.004 μmol L(-1) (S/N = 3). Moreover, the biosensor exhibits high reproducibility and stability in acid solution. Our work not only offers a simple way to achieve the direct electrochemical behavior of metalloporphyrin but also expands the potential applications of MOFs-based composites in bioanalysis. PMID:27351460

  15. Fabrication of an electrochemical sensor based on carbon nanotubes modified with gold nanoparticles for determination of valrubicin as a chemotherapy drug: valrubicin-DNA interaction.

    PubMed

    Hajian, R; Mehrayin, Z; Mohagheghian, M; Zafari, M; Hosseini, P; Shams, N

    2015-04-01

    In this study, an electrochemical sensor was fabricated based on gold nanoparticles/ ethylenediamine/ multi-wall carbon-nanotubes modified gold electrode (AuNPs/en/MWCNTs/AuE) for determination of valrubicin in biological samples. Valrubicin was effectively accumulated on the surface of AuNPs/en/MWCNTs/AuE and produced a pair of redox peaks at around 0.662 and 0.578V (vs. Ag/AgCl) in citrate buffer (pH4.0). The electrochemical parameters including pH, buffer, ionic strength, scan rate and size of AuNPs have been optimized. There was a good linear correlation between cathodic peak current and concentration of valrubicin in the range of 0.5 to 80.0μmolL(-1) with the detection limit of 0.018μmolL(-1) in citrate buffer (pH4.0) and 0.1molL(-1) KCl. Finally, the constructed sensor was successfully applied for determination of valrubicin in human urine and blood serum. In further studies, the different sequences of single stranded DNA probes have been immobilized on the surface of AuNPs decorated on MWCNTs to study the interaction of oligonucleotides with valrubicin.

  16. Direct electrochemical oxidation of S-captopril using gold electrodes modified with graphene-AuAg nanocomposites.

    PubMed

    Pogacean, Florina; Biris, Alexandru R; Coros, Maria; Lazar, Mihaela Diana; Watanabe, Fumiya; Kannarpady, Ganesh K; Al Said, Said A Farha; Biris, Alexandru S; Pruneanu, Stela

    2014-01-01

    In this paper, we present a novel approach for the electrochemical detection of S-captopril based on graphene AuAg nanostructures used to modify an Au electrode. Multi-layer graphene (Gr) sheets decorated with embedded bimetallic AuAg nanoparticles were successfully synthesized catalytically with methane as the carbon source. The two catalytic systems contained 1.0 wt% Ag and 1.0 wt% Au, while the second had a larger concentration of metals (1.5 wt% Ag and 1.5 wt% Au) and was used for the synthesis of the Gr-AuAg-1 and Gr-AuAg-1.5 multicomponent samples. High-resolution transmission electron microscopy analysis indicated the presence of graphene flakes that had regular shapes (square or rectangular) and dimensions in the tens to hundreds of nanometers. We found that the size of the embedded AuAg nanoparticles varied between 5 and 100 nm, with the majority being smaller than 20 nm. Advanced scanning transmission electron microscopy studies indicated a bimetallic characteristic of the metallic clusters. The resulting Gr-AuAg-1 and Gr-AuAg-1.5 samples were used to modify the surface of commonly used Au substrates and subsequently employed for the direct electrochemical oxidation of S-captopril. By comparing the differential pulse voltammograms recorded with the two modified electrodes at various concentrations of captopril, the peak current was determined to be well-defined, even at relatively low concentration (10(-5) M), for the Au/Gr-AuAg-1.5 electrode. In contrast, the signals recorded with the Au/Gr-AuAg-1 electrode were poorly defined within a 5×10(-6) to 5×10(-3) M concentration range, and many of them overlapped with the background. Such composite materials could find significant applications in nanotechnology, sensing, or nanomedicine.

  17. Direct electrochemical oxidation of S-captopril using gold electrodes modified with graphene-AuAg nanocomposites

    PubMed Central

    Pogacean, Florina; Biris, Alexandru R; Coros, Maria; Lazar, Mihaela Diana; Watanabe, Fumiya; Kannarpady, Ganesh K; Al Said, Said A Farha; Biris, Alexandru S; Pruneanu, Stela

    2014-01-01

    In this paper, we present a novel approach for the electrochemical detection of S-captopril based on graphene AuAg nanostructures used to modify an Au electrode. Multi-layer graphene (Gr) sheets decorated with embedded bimetallic AuAg nanoparticles were successfully synthesized catalytically with methane as the carbon source. The two catalytic systems contained 1.0 wt% Ag and 1.0 wt% Au, while the second had a larger concentration of metals (1.5 wt% Ag and 1.5 wt% Au) and was used for the synthesis of the Gr-AuAg-1 and Gr-AuAg-1.5 multicomponent samples. High-resolution transmission electron microscopy analysis indicated the presence of graphene flakes that had regular shapes (square or rectangular) and dimensions in the tens to hundreds of nanometers. We found that the size of the embedded AuAg nanoparticles varied between 5 and 100 nm, with the majority being smaller than 20 nm. Advanced scanning transmission electron microscopy studies indicated a bimetallic characteristic of the metallic clusters. The resulting Gr-AuAg-1 and Gr-AuAg-1.5 samples were used to modify the surface of commonly used Au substrates and subsequently employed for the direct electrochemical oxidation of S-captopril. By comparing the differential pulse voltammograms recorded with the two modified electrodes at various concentrations of captopril, the peak current was determined to be well-defined, even at relatively low concentration (10−5 M), for the Au/Gr-AuAg-1.5 electrode. In contrast, the signals recorded with the Au/Gr-AuAg-1 electrode were poorly defined within a 5×10−6 to 5×10−3 M concentration range, and many of them overlapped with the background. Such composite materials could find significant applications in nanotechnology, sensing, or nanomedicine. PMID:24596464

  18. Impedimetric investigation of gold nanoparticles - guanine modified electrode

    NASA Astrophysics Data System (ADS)

    Vulcu, A.; Pruneanu, S.; Berghian-Grosan, C.; Olenic, L.; Muresan, L. M.; Barbu-Tudoran, L.

    2013-11-01

    In this paper we report the preparation of a modified electrode with gold nanoparticles and guanine. The colloidal suspension of gold nanoparticles was obtained by Turkevich method and was next analyzed by UV-Vis spectroscopy and Transmission Electron Microscopy (TEM). The gold electrode was modified by self-assembling the gold nanoparticles with guanine, the organic molecule playing also the role of linker. The electrochemical characteristics of the bare and modified electrode were investigated by Electrochemical Impedance Spectroscopy (EIS). A theoretical model was developed based on an electrical equivalent circuit which contain solution resistance (Rs), charge transfer resistance (Rct), Warburg impedance (ZW) and double layer capacitance (Cdl).

  19. Electrochemical DNA biosensor based on a glassy carbon electrode modified with gold nanoparticles and graphene for sensitive determination of Klebsiella pneumoniae carbapenemase.

    PubMed

    Pan, Hong-zhi; Yu, Hong-wei; Wang, Na; Zhang, Ze; Wan, Guang-cai; Liu, Hao; Guan, Xue; Chang, Dong

    2015-11-20

    We describe the fabrication of a sensitive electrochemical DNA biosensor for determination of Klebsiella pneumoniae carbapenemase (KPC). The highly sensitive and selective electrochemical biosensor for DNA detection was constructed based on a glassy carbon electrode (GCE) modified with gold nanoparticles (Au-NPs) and graphene (Gr). Then Au-NPs/Gr/GCE was characterized by scanning electro microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The hybridization detection was measured by diffierential pulse voltammetry (DPV) using methylene blue (MB) as the hybridization indicator. The dynamic range of detection of the sensor for the target DNA sequences was from 1 × 10(-12) to 1 × 10(-7)mol/L, with a detection limit of 2 × 10(-13)mol/L. The DNA biosensor had excellent specificity for distinguishing complementary DNA sequence in the presence of non-complementary and mismatched DNA sequence. The results demonstrated that the Au-NPs/Gr nanocomposite was a promising substrate for the development of high-performance electrocatalysts for determination of KPC.

  20. A very low potential electrochemical detection of L-cysteine based on a glassy carbon electrode modified with multi-walled carbon nanotubes/gold nanorods.

    PubMed

    Silva, Francisco de Assis dos Santos; da Silva, Monique Gabriella Angelo; Lima, Phabyanno Rodrigues; Meneghetti, Mario Roberto; Kubota, Lauro Tatsuo; Goulart, Marilia Oliveira Fonseca

    2013-12-15

    A nanohybrid platform built with multi-walled carbon nanotubes and gold nanorods, prepared via a cationic surfactant-containing seed-mediated sequential growth process, in aqueous solution, on a glassy carbon substrate has been successfully developed to be used in the electrocatalytic oxidation of L-cysteine (Cys). The nanohybrid was characterized by transmission electron microscopy, Raman spectroscopy and electrochemical measurements. Cyclic voltammetry results had shown that the modified electrode allows the oxidation of Cys at a very low anodic potential (0.00 V vs. Ag/AgCl). The kinetic constant kcat for the catalytic oxidation of Cys was evaluated by chronoamperometry and provided a value of 5.6×10(4) L mol(-1) s(-1). The sensor presents a linear response range from 5.0 up to 200.0 µmol L(-1), detection limit of 8.25 nmol L(-1) and a sensitivity of 120 nA L µmol(-1).

  1. Electrochemical Oxidation of Cysteine at a Film Gold Modified Carbon Fiber Microelectrode Its Application in a Flow—Through Voltammetric Sensor

    PubMed Central

    Wang, Lai-Hao; Huang, Wen-Shiuan

    2012-01-01

    A flow-electrolytical cell containing a strand of micro Au modified carbon fiber electrodes (CFE) has been designedand characterized for use in a voltammatric detector for detecting cysteine using high-performance liquid chromatography. Cysteine is more efficiently electrochemical oxidized on a Au /CFE than a bare gold and carbon fiber electrode. The possible reaction mechanism of the oxidation process is described from the relations to scan rate, peak potentials and currents. For the pulse mode, and measurements with suitable experimental parameters, a linear concentration from 0.5 to 5.0 mg·L−1 was found. The limit of quantification for cysteine was below 60 ng·mL−1. PMID:22737024

  2. An electrochemical biosensor for fructosyl valine for glycosylated hemoglobin detection based on core-shell magnetic bionanoparticles modified gold electrode.

    PubMed

    Chawla, Sheetal; Pundir, Chandra Shekhar

    2011-04-15

    A high-performance amperometric fructosyl valine (FV) biosensor was developed, based on immobilization of fructosyl amino-acid oxidase (FAO) on core-shell magnetic bionanoparticles modified gold electrode. Chitosan was used to introduce amino groups onto the surface of core-shell magnetic bionanoparticles (MNPs). With FAO as an enzyme model, a new fructosyl valine biosensor was fabricated. The biosensor showed optimum response, when operated at 50 mVs(-1) in 0.1M potassium phosphate buffer, pH 7.5 and 35°C. The biosensor exhibited excellent sensitivity [the detection limit is down to 0.1mM for FV], fast response time (less than 4s), wide linear range (from 0 to 2mM). Analytical recovery of added FV was 95.00-98.50%. Within batch and between batch coefficients of variation were <2.58% and <5.63%, respectively. The enzyme electrode was used 250 times over 3 months, when stored at 4°C.

  3. Electrochemical Assay of Gold-Plating Solutions

    NASA Technical Reports Server (NTRS)

    Chiodo, R.

    1982-01-01

    Gold content of plating solution is assayed by simple method that required only ordinary electrochemical laboratory equipment and materials. Technique involves electrodeposition of gold from solution onto electrode, the weight gain of which is measured. Suitable fast assay methods are economically and practically necessary in electronics and decorative-plating industries. If gold content in plating bath is too low, poor plating may result, with consequent economic loss to user.

  4. Electrochemical control of creep in nanoporous gold

    SciTech Connect

    Ye, Xing-Long; Jin, Hai-Jun

    2013-11-11

    We have investigated the mechanical stability of nanoporous gold (npg) in an electrochemical environment, using in situ dilatometry and compression experiments. It is demonstrated that the gold nano-ligaments creep under the action of surface stress which leads to spontaneous volume contractions in macroscopic npg samples. The creep of npg, under or without external forces, can be controlled electrochemically. The creep rate increases with increasing potential in double-layer potential region, and deceases to almost zero when the gold surface is adsorbed with oxygen. Surprisingly, we also noticed a correlation between creep and surface diffusivity, which links the deformation of nanocrystals to mobility of surface atoms.

  5. A Renewable Electrochemical Magnetic Immunosensor Based on Gold Nanoparticle Labels

    SciTech Connect

    Liu, Guodong; Lin, Yuehe

    2005-05-24

    A particle-based renewable electrochemical magnetic immunosensor was developed by using magnetic beads and a gold nanoparticle label. Anti-IgG antibody-modified magnetic beads were attached to a renewable carbon paste transducer surface by magnets that were fixed inside the sensor. A gold nanoparticle label was capsulated to the surface of magnetic beads by sandwich immunoassay. Highly sensitive electrochemical stripping analysis offers a simple and fast method to quantify the capatured gold nanoparticle tracer and avoid the use of an enzyme label and substrate. The stripping signal of gold nanoparticle is related to the concentration of target IgG in the sample solution. A transmission electron microscopy image shows that the gold nanoparticles were successfully capsulated to the surface of magnetic beads through sandwich immunoreaction events. The parameters of immunoassay, including the loading of magnetic beads, the amount of gold nanoparticle conjugate, and the immunoreaction time, were optimized. The detection limit of 0.02 μg ml-1of IgG was obtained under optimum experimental conditions. Such particle-based electrochemical magnetic immunosensors could be readily used for simultaneous parallel detection of multiple proteins by using multiple inorganic metal nanoparticle tracers and are expected to open new opportunities for disease diagnostics and biosecurity.

  6. Impedimetric investigation of gold nanoparticles - guanine modified electrode

    SciTech Connect

    Vulcu, A.; Pruneanu, S.; Berghian-Grosan, C.; Olenic, L.; Muresan, L. M.; Barbu-Tudoran, L.

    2013-11-13

    In this paper we report the preparation of a modified electrode with gold nanoparticles and guanine. The colloidal suspension of gold nanoparticles was obtained by Turkevich method and was next analyzed by UV-Vis spectroscopy and Transmission Electron Microscopy (TEM). The gold electrode was modified by self-assembling the gold nanoparticles with guanine, the organic molecule playing also the role of linker. The electrochemical characteristics of the bare and modified electrode were investigated by Electrochemical Impedance Spectroscopy (EIS). A theoretical model was developed based on an electrical equivalent circuit which contain solution resistance (R{sub s}), charge transfer resistance (R{sub ct}), Warburg impedance (Z{sub W}) and double layer capacitance (C{sub dl})

  7. Electrochemical assembling of methionine-gold nanoparticles and catalysis on the surface of glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Song, Y. Z.; Wang, J. H.; Zhang, X. M.; Cao, W.; Ge, A.; Zhou, L.

    2014-12-01

    In this paper cyclic voltammetry was used for the synthesis of linear array spherical gold nanoparticles on the surface of glassy carbon electrode using methionine as a stable reagent. The methionine-gold nanoparticles on the surface of glassy electrode were obtained. The methionine-gold nanoparticles were characterized by cyclic voltammetry, scanning electron microscopy, energy dispersive spectrometry and powder X-ray diffraction. Electrochemical behavior of methionine at methionine-gold nanoparticle modified electrode was investigated. It was demonstrated that the methionine-gold nanoparticles can catalyze electrochemical transformations of methionine.

  8. Caffeine electrochemical sensor using imprinted film as recognition element based on polypyrrole, sol-gel, and gold nanoparticles hybrid nanocomposite modified pencil graphite electrode.

    PubMed

    Rezaei, Behzad; Khalili Boroujeni, Malihe; Ensafi, Ali A

    2014-10-15

    In the present study, a novel sensitive and selective nanocomposite imprinted electrochemical sensor for the indirect determination of caffeine has been prepared. The imprinted sensor was fabricated on the surface of pencil graphite electrode (PGE) via one-step electropolymerization of the imprinted polymer composed of conductive polymer, sol-gel, gold nanoparticles (AuNPs), and caffeine. Due to such combination like the thin film of molecularly imprinted polymer (MIP) with specific binding sites, the sensor responded quickly to caffeine. AuNPs were introduced for the enhancement of electrical response by facilitating charge transfer processes of [Fe(CN)6](3-)/[Fe(CN)6](4-) which was used as an electrochemical active probe. The fabrication process of the sensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Several important parameters controlling the performance of the sensor were investigated and optimized. The imprinted sensor has the advantages of high porous surface structure, inexpensive, disposable, excellent stability, good reproducibility and repeatability. The linear ranges of the MIP sensor were in the range from 2.0 to 50.0 and 50.0 to 1000.0 nmol L(-1), with the limit of detection (LOD) of 0.9 nmol L(-1) (S/N=3). Furthermore, the proposed method was successfully intended for the determination of caffeine in real samples (urine, plasma, tablet, green tea, energy and soda drink).

  9. A new immobilization procedure for development of an electrochemical immunosensor for parathyroid hormone detection based on gold electrodes modified with 6-mercaptohexanol and silane.

    PubMed

    Sayıklı Şimşek, Çiğdem; Nur Sonuç Karaboğa, Münteha; Sezgintürk, Mustafa Kemal

    2015-11-01

    Fabrication of a new electrochemical impedance-based biosensor for the analysis of parathyroid hormone (PTH), using self-assembled monolayers (SAMs) of mercaptohexanol and (3-Aminopropyl) triethoxysilane on gold electrodes, was investigated for the first time in the field. Anti-PTH was used as a biorecognition element. To monitor immobilization processes in the biosensor fabrication, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) techniques were successfully operated. CV and EIS techniques were also used in quantification of PTH. Energy-dispersive X-ray analysis (EDAX) was also applied to identify surface modifications. Fabrication and working parameters of the biosensor were optimized. Moreover, Kramers-Kronig transformations were performed for validation of obtained EIS data in all steps of biosensor fabrication. The linear PTH detection range of the presented biosensor was 10-50 pg/mL PTH. The chrono-impedance technique for real-time monitoring of PTH binding was also implemented. The biosensor has exhibited good repeatability (with a correlation) and reproducibility. Finally, artificial serum samples spiked with known concentrations of PTH were analyzed by the proposed biosensor. To demonstrate the feasibility of the biosensor in practical analysis, real human serum samples and the artificial serum samples were analyzed.

  10. Enzymatically catalytic deposition of gold nanoparticles by glucose oxidase-functionalized gold nanoprobe for ultrasensitive electrochemical immunoassay.

    PubMed

    Cheng, Hui; Lai, Guosong; Fu, Li; Zhang, Haili; Yu, Aimin

    2015-09-15

    A novel ultrasensitive immunoassay method was developed by combination of the enzymatically catalytic gold deposition with the prepared gold nanoprobe and the gold stripping analysis at an electrochemical chip based immunosensor. The immunosensor was constructed through covalently immobilizing capture antibody at a carbon nanotube (CNT) modified screen-printed carbon electrode. The gold nanoprobe was prepared by loading signal antibody and high-content glucose oxidase (GOD) on the nanocarrier of gold nanorod (Au NR). After sandwich immunoreaction, the GOD-Au NR nanoprobe could be quantitatively captured onto the immunosensor surface and then induce the deposition of gold nanoparticles (Au NPs) via the enzymatically catalytic reaction. Based on the electrochemical stripping analysis of the Au NR nanocarriers and the enzymatically produced Au NPs, sensitive electrochemical signal was obtained for the immunoassay. Both the GOD-induced deposition of Au NPs by the nanoprobe and the sensitive electrochemical stripping analysis on the CNTs based sensing surface greatly amplified the signal response, leading to the ultrahigh sensitivity of this method. Using carcinoembryonic antigen as a model analyte, excellent analytical performance including a wide linear range from 0.01 to 100 ng/mL and a detection limit down to 4.2 pg/mL was obtained. In addition, this immunosensor showed high specificity and satisfactory reproducibility, stability and reliability. The relatively positive detection potential excluded the conventional interference from dissolved oxygen. Thus this electrochemical chip based immunosensing method provided great potentials for practical applications.

  11. Chemically modified graphite for electrochemical cells

    DOEpatents

    Greinke, Ronald Alfred; Lewis, Irwin Charles

    1998-01-01

    This invention relates to chemically modified graphite particles: (a) that are useful in alkali metal-containing electrode of a electrochemical cell comprising: (i) the electrode, (ii) a non-aqueous electrolytic solution comprising an organic aprotic solvent which solvent tends to decompose when the electrochemical cell is in use, and an electrically conductive salt of an alkali metal, and (iii) a counterelectrode; and (b) that are chemically modified with fluorine, chlorine, iodine or phosphorus to reduce such decomposition. This invention also relates to electrodes comprising such chemically modified graphite and a binder and to electrochemical cells containing such electrodes.

  12. Chemically modified graphite for electrochemical cells

    DOEpatents

    Greinke, R.A.; Lewis, I.C.

    1998-05-26

    This invention relates to chemically modified graphite particles: (a) that are useful in alkali metal-containing electrode of a electrochemical cell comprising: (1) the electrode, (2) a non-aqueous electrolytic solution comprising an organic aprotic solvent which solvent tends to decompose when the electrochemical cell is in use, and an electrically conductive salt of an alkali metal, and (3) a counter electrode; and (b) that are chemically modified with fluorine, chlorine, iodine or phosphorus to reduce such decomposition. This invention also relates to electrodes comprising such chemically modified graphite and a binder and to electrochemical cells containing such electrodes. 3 figs.

  13. Electrochemical apparatus comprising modified disposable rectangular cuvette

    DOEpatents

    Dattelbaum, Andrew M; Gupta, Gautam; Morris, David E

    2013-09-10

    Electrochemical apparatus includes a disposable rectangular cuvette modified with at least one hole through a side and/or the bottom. Apparatus may include more than one cuvette, which in practice is a disposable rectangular glass or plastic cuvette modified by drilling the hole(s) through. The apparatus include two plates and some means of fastening one plate to the other. The apparatus may be interfaced with a fiber optic or microscope objective, and a spectrometer for spectroscopic studies. The apparatus are suitable for a variety of electrochemical experiments, including surface electrochemistry, bulk electrolysis, and flow cell experiments.

  14. Characterization of electrochemically modified polycrystalline platinum surfaces

    SciTech Connect

    Krebs, L.C.; Ishida, Takanobu.

    1991-12-01

    The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between {minus}0.24 and +1.25 V{sub SCE} while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-{rho}-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.

  15. Electrochemical accumulation of visible gold on pyrite and arsenopyrite surfaces

    NASA Astrophysics Data System (ADS)

    Möller, P.; Kersten, G.

    1994-09-01

    In galvanic cell arrangements gold is electrochemically deposited on semiconducting sulfide minerals (pyrite, arsenopyrite, chalcopyrite) from aerated as well as H2S-saturated, gold-bearing 1 M KCl solutions. Observed cell potential differences of about 0.4 0.6 V in setups with one sulfide in aerated (cathode) and the other in H2S-saturated (anode) solutions are comparable with known “self-potentials” of natural sulfide ore bodies. Gold preferentially accumulates on the cathode, i.e. under oxidizing conditions. Linked sulfides of variable composition in the same environment, either oxidizing or reducing, yield potential differences up to 20 mV. Such assemblages simulate conditions typically occurring at surfaces of chemically inhomogeneous single crystals (e.g. zonation). Depending on chemical composition, sulfide minerals show either n- or p-type conductivity. Visible gold is preferentially accumulated on individual domains of sulfide surfaces that act as cathodes, i.e. p-type conductors in n-p junctions. The experimental results are discussed in view of electrochemical accumulation of visible gold on sulfides in nature. Arsenic is the most important element in establishing p-type conductivity of pyrite and arsenopyrite. This feature may explain why As is such a powerful pathfinder in gold exploration.

  16. Label-free electrochemical monitoring of protein addressing through electroactivated "click" chemistry on gold electrodes.

    PubMed

    Meini, Nadir; Ripert, Micaël; Chaix, Carole; Farre, Carole; De Crozals, Gabriel; Kherrat, Rochdi; Jaffrezic-Renault, Nicole

    2014-05-01

    In this work, using electrochemical impedance spectroscopy (EIS), we have, for the first time, label-free monitored protein immobilization on a gold surface through a strategy of electroaddressing, compatible with the production of microarrays for multi-detection. This functionalization is achieved via the alkyne/azide cycloaddition, better known as the "click" reaction. The electroaddressing was applied to a polythiol hexynyl derivative previously grafted onto the gold surface. This compound consists of two dithiol phosphate groups and a hexynyl function and was synthesized through a supported synthesis approach, from a dithiol reagent, phosphoramidite (DTPA), and a hexynyl phosphoramidite. Next, an azide-PEG3-biotin derivative was grafted onto the modified gold surface by electro-chronocoulometry. The "click" reaction was controlled by electrochemical impedance spectroscopy, showing the change in impedance only when the electroaddressing was performed at -300 mV. No effect on the EIS signal was observed when a positive potential was applied, confirming the specificity of the electroactivation. Biotin-modified electrodes were used to fix streptavidin and the immobilization was monitored using EIS. Fluorescent streptavidin-functionalized silica nanoparticles were also specifically grafted onto the biotinylated gold surface in order to confirm the "click" reaction using fluorescence microscopy. The obtained streptavidin platform was used to detect the surface coverage by biotinylated human serum albumin (HSA). The lowest detectable concentration is 10 pg/mL, and surface saturation is obtained with concentrations higher than 100 ng/mL.

  17. Multiplex Electrochemical Immunoassay Using Gold Nanoparticle Probes and Immunochromatographic Strips

    SciTech Connect

    Mao, Xun; Baloda, Meenu; Gurung, Anant; Lin, Yuehe; Liu, Guodong

    2008-10-20

    We describe a multiplex electrochemical immunoassay based on the use of gold nanoparticle (Au-NP) probes and immunochromatographic strips (ISs). The approach takes advantage of the speed and low cost of the conventional IS tests and the high sensitivities of the nanoparticle-based electrochemical immunoassays. Rabbit IgG(R-IgG) and human IgM (H-IgM) were used as model targets for the demonstration of the proof of concept. The Au-NPs based sandwich immunoreactions were performed on the IS, and the captured gold nanoparticle labels on the test zones were determined by highly-sensitive stripping voltammetric measurement of the dissolved gold ions (III) with a carbon paste electrode. The detection limits are 1.0 and 1.5 ng/mL with the linear ranges of 2.5-250 ng/mL for quantitative detection of R-IgG and H-IgM, respectively. The total assay time is around 25 minutes. Such multiplex electrochemical immunoassay could be readily highly multiplexed to allow simultaneous parallel detection of numerous proteins and is expected to open new opportunities for protein diagnostics and biosecurity.

  18. A sensitive nanoporous gold-based electrochemical aptasensor for thrombin detection.

    PubMed

    Qiu, Huajun; Sun, Yanli; Huang, Xirong; Qu, Yinbo

    2010-08-01

    An attempt was made in the present paper to develop a nanoporous gold (NPG)-based electrochemical aptasensor for thrombin detection. The substrate electrode NPG was in situ fabricated by a facile one-step square wave potential pulse (SWPP) treatment. The treatment involved repeated gold oxidation-reduction and intensive H(2) bubbles evolution. After 100min treatment, the active surface area of Au increased greatly (34 times). The electrochemical aptasensor was fabricated using a layer-by-layer assembling strategy. A "sandwich" structure was formed via thrombin connecting the aptamer-modified NPG and the aptamer-modified Au nanoparticles (AuNPs). The AuNPs was modified with two kinds of single strand DNA (ssDNA). One was aptamer of thrombin, but the other was not, reducing the cross-reaction between thrombin and its aptamer on the same AuNP. The electrochemical signal produced by the [Ru(NH(3))(6)](3+) bound to ssDNA via electrostatic interaction was measured by chronocoulometry. Due to the amplification effects of both NPG and AuNPs, this novel NPG-based aptasensor could detect thrombin quantitatively in the range of 0.01-22nM with a detection limit as low as 30fM. The present aptasensor also exhibited excellent selectivity, stability and reusability.

  19. Sensitive electrochemical detection of Salmonella with chitosan-gold nanoparticles composite film.

    PubMed

    Xiang, Cuili; Li, Ran; Adhikari, Bimalendu; She, Zhe; Li, Yongxin; Kraatz, Heinz-Bernhard

    2015-08-01

    An ultrasensitive electrochemical immunosensor for detection of Salmonella has been developed based on using high density gold nanoparticles (GNPs) well dispersed in chitosan hydrogel and modified glassy carbon electrode. The composite film has been oxidized in NaCl solution and used as a platform for the immobilization of capture antibody (Ab1) for biorecognition. After incubation in Salmonella suspension and horseradish peroxidase (HRP) conjugated secondary antibody (Ab2) solution, a sandwich electrochemical immunosensor has been constructed. The electrochemical signal was obtained and improved by comparing the composite film with chitosan film. The result has shown that the constructed sensor provides a wide linear range from 10 to 10(5) CFU/mL with a low detection limit of 5 CFU/mL (at the ratio of signal to noise, S/N=3:1). Furthermore, the proposed immunosensor has demonstrated good selectivity and reproducibility, which indicates its potential in the clinical diagnosis of Salmonella contaminations. PMID:26048833

  20. "The Golden Method": Electrochemical Synthesis Is an Efficient Route to Gold Complexes.

    PubMed

    González-Barcia, Luis M; Romero, María J; González Noya, Ana M; Bermejo, Manuel R; Maneiro, Marcelino; Zaragoza, Guillermo; Pedrido, Rosa

    2016-08-15

    Gold compounds to be obtained by the direct electrochemical oxidation of a noble metal are reported. This achievement provides an alternative procedure to obtaining neutral gold compounds with potential medical or catalytic applications. PMID:27483164

  1. Shape control technology during electrochemical synthesis of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Xiu-yu; Cui, Cong-ying; Cheng, Ying-wen; Ma, Hou-yi; Liu, Duo

    2013-05-01

    Gold nanoparticles with different shapes and sizes were prepared by adding gold precursor (HAuCl4) to an electrolyzed aqueous solution of poly( N-vinylpyrrolidone) (PVP) and KNO3, which indicates the good reducing capacity of the PVP-containing solution after being treated by electrolysis. Using a catholyte and an anolyte as the reducing agents for HAuCl4, respectively, most gold nanoparticles were spherical particles in the former case but plate-like particles in the latter case. The change in the pH value of electrolytes caused by the electrolysis of water would be the origin of the differences in shape and morphology of gold nanoparticles. A hypothesis of the H+ or OH- catalyzed PVP degradation mechanism was proposed to interpret why the pH value played a key role in determining the shape or morphology of gold nanoparticles. These experiments open up a new method for effectively controlling the shape and morphology of metal nanoparticles by using electrochemical methods.

  2. Electrochemically Controlled Atom by Atom Deposition of Gold to Polyaniline

    SciTech Connect

    Jonke, Alex P.; Josowicz, Mira A.; Janata, Jiri; Engelhard, Mark H.

    2010-08-17

    Plyaniline (PANI) has been shown to be an effective matrix for hosting metal nanoclusters. In the case of gold, the tetrachloroaurate anion (AuCl₄) has a high affinity for the imine sites of polyaniline. Upon contract with PANI, AuCl₄ is spontaneously reduced to metallic gold, but the size of the formed Au clusters can not be precisely controlled. Herein, we report on electrochemical method of controlled deposition of one atom by one atom of gold per one imine site of PANI. By controlling the potential, we keep PANI in an oxidized state while exposing it to a solution of AuCl₄ to form a PANI*AuCl₄ complex. The AuCl₄ is reduced to atomic gold by sweeping the potential negative. That frees up the imine sites of PANI again and makes them accessible for the next Au deposition cycle. The repeated deposition of Au atoms follows a cyclic pathway. The amount of gold deposited using this method is consistent for each repeated cycle.

  3. Determination of groundwater mercury (II) content using a disposable gold modified screen printed carbon electrode.

    PubMed

    Somé, Issa Touridomon; Sakira, Abdoul Karim; Mertens, Dominique; Ronkart, Sebastien N; Kauffmann, Jean-Michel

    2016-05-15

    Mercury (II) measurements were performed thanks to a newly developed electrochemical method using a disposable gold modified screen printed carbon electrode. The method has a wide dynamic range (1-100 µg/L), a good accuracy and a limit of detection in compliance with WHO standards. The application of the method to several groundwater samples made it possible to identify, for the first time, mercury content higher than the recommended WHO standard value in a gold mining activity area in the northern part of Burkina Faso. The accuracy of the assay was checked by ICP/MS. PMID:26992529

  4. Reduced graphene oxide-yttria nanocomposite modified electrode for enhancing the sensitivity of electrochemical genosensor.

    PubMed

    Rasheed, P Abdul; Radhakrishnan, Thulasi; Shihabudeen, P K; Sandhyarani, N

    2016-09-15

    Reduced graphene oxide-yttria nanocomposite (rGO:Y) is applied as electrochemical genosensor platform for ultrahigh sensitive detection of breast cancer 1 (BRCA1) gene for the first time. The sensor is based on the sandwich assay in which gold nanoparticle cluster labeled reporter DNA hybridize to the target DNA. Glassy carbon electrode modified with rGO-yttria serves as the immobilization platform for capture probe DNA. The sensor exhibited a fine capability of sensing BRCA1 gene with linear range of 10attomolar (aM) to 1nanomolar (nM) and a detection limit of 5.95attomolar. The minimum distinguishable response concentration is down to the attomolar level with a high sensitivity and selectivity. We demonstrated that the use of rGO:Y modified electrode along with gold nanoparticle cluster (AuNPC) label leads to the highly sensitive electrochemical detection of BRCA1 gene. PMID:27153526

  5. Reduced graphene oxide-yttria nanocomposite modified electrode for enhancing the sensitivity of electrochemical genosensor.

    PubMed

    Rasheed, P Abdul; Radhakrishnan, Thulasi; Shihabudeen, P K; Sandhyarani, N

    2016-09-15

    Reduced graphene oxide-yttria nanocomposite (rGO:Y) is applied as electrochemical genosensor platform for ultrahigh sensitive detection of breast cancer 1 (BRCA1) gene for the first time. The sensor is based on the sandwich assay in which gold nanoparticle cluster labeled reporter DNA hybridize to the target DNA. Glassy carbon electrode modified with rGO-yttria serves as the immobilization platform for capture probe DNA. The sensor exhibited a fine capability of sensing BRCA1 gene with linear range of 10attomolar (aM) to 1nanomolar (nM) and a detection limit of 5.95attomolar. The minimum distinguishable response concentration is down to the attomolar level with a high sensitivity and selectivity. We demonstrated that the use of rGO:Y modified electrode along with gold nanoparticle cluster (AuNPC) label leads to the highly sensitive electrochemical detection of BRCA1 gene.

  6. Electrochemical DNA biosensor based on gold nanorods for detecting hepatitis B virus.

    PubMed

    Shakoori, Zahra; Salimian, Samaneh; Kharrazi, Sharmin; Adabi, Mahdi; Saber, Reza

    2015-01-01

    The purpose of this work was to fabricate an electrochemical DNA biosensor for detecting hepatitis B virus. Gold nanorods (GNRs), which are known for their conductivity, were used to increase surface area and consequently increase the immobilization of single-stranded DNA (ss-DNA) on the modified gold electrode. The GNRs were characterized via transmission electron microscopy. The morphology of the gold electrode before and after modification with GNRs was characterized by scanning electron microscopy. Atomic-force microscopy was used to evaluate the morphology of the GNR electrode surface before and after interaction with ss-DNA. Cyclic voltammetry was used to monitor DNA immobilization and hybridization, using [Co(phen)3](3+) as an electrochemical indicator. The target DNA sequences were quantified at a linear range from 1.0 × 10(-12) to 10.0 × 10(-6) mol L(-1), with a detection limit of 2.0 × 10(-12) mol L(-1) by 3σ. The biosensor had good specificity for distinguishing complementary DNA in the presence of non-complementary and mismatched DNA sequences. PMID:25399076

  7. Electrochemically deposited chitosan hydrogel for horseradish peroxidase immobilization through gold nanoparticles self-assembly.

    PubMed

    Luo, Xi-Liang; Xu, Jing-Juan; Zhang, Qing; Yang, Gong-Jun; Chen, Hong-Yuan

    2005-07-15

    A new strategy for immobilization of horseradish peroxidase (HRP) has been presented by self-assembling gold nanoparticles on chitosan hydrogel modified Au electrode. From a mildly acidic chitosan solution, a chitosan film is electrochemically deposited on Au electrode surface via a negative voltage bias. This process is accompanied by the hydrogen evolution reaction, and the released hydrogen gas made the deposited chitosan film with porous structure, which facilitates the assembly of gold nanoparticles and HRP. The resulting substrates were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The immobilized HRP displayed an excellent catalytic property to the reduction of H2O2 in the presence of methylene blue mediator. The resulting biosensor (HRP-modified electrode) showed a wide dynamic range of 8.0 microM-15 mM H2O2, and the linear ranges were 8.0 microM-0.12 mM and 0.50-12 mM, with a detection limit of 2.4 microM estimated at a signal-to-noise ratio of 3. Moreover, the biosensor remained about 85% of its original sensitivity after four weeks' storage.

  8. Laccase-modified gold nanorods for electrocatalytic reduction of oxygen.

    PubMed

    Di Bari, Chiara; Shleev, Sergey; De Lacey, Antonio L; Pita, Marcos

    2016-02-01

    cathodes. Nanostructuring was provided by gold nanorods (AuNRs), which were characterized and covalently attached to electrodes made of low-density graphite. The nanostructured electrode was the scaffold for covalent and oriented attachment of ThLc. The bioelectrocatalytic currents measured for oxygen reduction were as high as 0.5 mA/cm(2 and 0.7 mA/cm(2), which were recorded under direct and mediated electron transfer regimes, respectively. )The experimental data were fitted to mathematical models showing that when the O2 is bioelectroreduced at high rotation speed of the electrode the heterogeneous electron transfer step is the rate-liming stage. The electrochemical measurement hints a wider population of non-optimally wired laccases than previously reported for 5–8 nm size Au nanoparticle-modified electrode, which could be due to a larger size of the AuNRs when compared to the laccases as well as their different crystal facets. PMID:26523503

  9. Laccase-modified gold nanorods for electrocatalytic reduction of oxygen.

    PubMed

    Di Bari, Chiara; Shleev, Sergey; De Lacey, Antonio L; Pita, Marcos

    2016-02-01

    cathodes. Nanostructuring was provided by gold nanorods (AuNRs), which were characterized and covalently attached to electrodes made of low-density graphite. The nanostructured electrode was the scaffold for covalent and oriented attachment of ThLc. The bioelectrocatalytic currents measured for oxygen reduction were as high as 0.5 mA/cm(2 and 0.7 mA/cm(2), which were recorded under direct and mediated electron transfer regimes, respectively. )The experimental data were fitted to mathematical models showing that when the O2 is bioelectroreduced at high rotation speed of the electrode the heterogeneous electron transfer step is the rate-liming stage. The electrochemical measurement hints a wider population of non-optimally wired laccases than previously reported for 5–8 nm size Au nanoparticle-modified electrode, which could be due to a larger size of the AuNRs when compared to the laccases as well as their different crystal facets.

  10. Fabrication a new modified electrochemical sensor based on Au-Pd bimetallic nanoparticle decorated graphene for citalopram determination.

    PubMed

    Daneshvar, Leili; Rounaghi, Gholam Hossein; Es'haghi, Zarrin; Chamsaz, Mahmoud; Tarahomi, Somayeh

    2016-12-01

    This paper proposes a simple approach for sensing of citalopram (CTL) using gold-palladium bimetallic nanoparticles (Au-PdNPs) decorated graphene modified gold electrode. Au-PdNPs were deposited at the surface of a graphene modified gold electrode with simple electrodeposition method. The morphology and the electrochemical properties of the modified electrode were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), energy dispersion spectroscopy (EDS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and square wave voltammetry (SWV). The novel sensor exhibited an excellent catalytic activity towards the oxidation of CTL. The oxidation peak current of CTL, was linear in the range of 0.5-50μM with a detection limit 0.049μM with respect to concentration of citalopram. The proposed sensor was successfully applied for determination of CTL tablet and human plasma samples with satisfactory results. PMID:27612758

  11. Fabrication a new modified electrochemical sensor based on Au-Pd bimetallic nanoparticle decorated graphene for citalopram determination.

    PubMed

    Daneshvar, Leili; Rounaghi, Gholam Hossein; Es'haghi, Zarrin; Chamsaz, Mahmoud; Tarahomi, Somayeh

    2016-12-01

    This paper proposes a simple approach for sensing of citalopram (CTL) using gold-palladium bimetallic nanoparticles (Au-PdNPs) decorated graphene modified gold electrode. Au-PdNPs were deposited at the surface of a graphene modified gold electrode with simple electrodeposition method. The morphology and the electrochemical properties of the modified electrode were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), energy dispersion spectroscopy (EDS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and square wave voltammetry (SWV). The novel sensor exhibited an excellent catalytic activity towards the oxidation of CTL. The oxidation peak current of CTL, was linear in the range of 0.5-50μM with a detection limit 0.049μM with respect to concentration of citalopram. The proposed sensor was successfully applied for determination of CTL tablet and human plasma samples with satisfactory results.

  12. Aptamer-based electrochemical approach to the detection of thrombin by modification of gold nanoparticles.

    PubMed

    Li, Lidong; Zhao, Hongtao; Chen, Zhengbo; Mu, Xiaojiao; Guo, Lin

    2010-09-01

    This paper presents a simple electrochemical approach for the detection of thrombin, using aptamer-modified electrodes. The use of gold nanoparticles results in significant signal enhancement for subsequent detection. 1,6-Hexanedithiol was used as the medium to link Au nanoparticles to a bare gold electrode. Anti-thrombin aptamers were immobilized on the gold nanoparticles' surfaces by self-assembly. The packing density of aptamers was determined by cyclic voltammetric (CV) studies of redox cations (e.g., [Ru(NH(3))(6)](3+)) which were electrostatically bound to the DNA phosphate backbones. The results indicate that the total amount of aptamer probes immobilized on the gold nanoparticle surface is sixfold higher than that on the bare electrode, leading to increased sensitivity of the aptasensor and a detection limit of 1 pmol L(-1). Based on the Langmuir model, the sensor signal displayed an almost perfect linear relationship over the range of 1 pmol L(-1) to 30 nmol L(-1). Moreover, the proposed aptasensor is highly selective and stable. In summary, this biosensor is simple, highly sensitive, and selective, which is beneficial to the ever-growing interest in fabricating portable bio-analytical devices with simple electrical readout procedures.

  13. DC-pulsed voltage electrochemical method based on duty cycle self-control for producing TERS gold tips

    NASA Astrophysics Data System (ADS)

    Vasilchenko, V. E.; Kharintsev, S. S.; Salakhov, M. Kh

    2013-12-01

    This paper presents a modified dc-pulsed low voltage electrochemical method in which a duty cycle is self tuned while etching. A higher yield of gold tips suitable for performing tip-enhanced Raman scattering (TERS) measurements is demonstrated. The improvement is caused by the self-control of the etching rate along the full surface of the tip. A capability of the gold tips to enhance a Raman signal is exemplified by TERS spectroscopy of single walled carbon nanotubes bundle, sulfur and vanadium oxide.

  14. Iodide sensing via electrochemical etching of ultrathin gold films

    NASA Astrophysics Data System (ADS)

    Dielacher, Bernd; Tiefenauer, Raphael F.; Junesch, Juliane; Vörös, János

    2015-01-01

    Iodide is an essential element for humans and animals and insufficient intake is still a major problem. Affordable and accurate methods are required to quantify iodide concentrations in biological and environmental fluids. A simple and low cost sensing device is presented which is based on iodide induced electrochemical etching of ultrathin gold films. The sensitivity of resistance measurements to film thickness changes is increased by using films with a thickness smaller than the electron mean free path. The underlying mechanism is demonstrated by simultaneous cyclic voltammetry experiments and resistance change measurements in a buffer solution. Iodide sensing is conducted in buffer solutions as well as in lake water with limits of detection in the range of 1 μM (127 μg L-1) and 2 μM (254 μg L-1), respectively. In addition, nanoholes embedded in the thin films are tested for suitability of optical iodide sensing based on localized surface plasmon resonance.

  15. Tuning the characteristics of electrochemically fabricated gold nanowires.

    PubMed

    Karim, S; Ensinger, W; Cornelius, T W; Khan, E U; Neumann, R

    2008-11-01

    We have developed different electrochemical procedures for the production of gold nanowires with variable and controllable crystallographic and morphological properties using etched ion track templates. The texture of the nanowires is tuned by the variation of the electrodeposition parameters. Potentiostatic plating at low overvoltage provides strongly (110) textured wires for diameters below 100 nm. With the increase in diameter above 100 nm, this texture decreases and the signal from ({111} planes becomes more pronounced. Under reverse pulse deposition conditions, (100) textured wires are generated. The growth mechanism is discussed in detail in terms of the surface energy minimum principle. In addition, wires are shaped in a reliable way from cylindrical to conical geometry by engineering the pore structure in the template. PMID:19198285

  16. [Electrochemical synthesis and spectroscopic characterization of gold nanoparticles].

    PubMed

    Shen, Li-Ming; Yao, Jian-Lin; Gu, Ren-Ao

    2005-12-01

    Two electrochemical methods were used to synthesize Au nanoparticles (AuNPs) with different shapes depending on the applied current. The dumbbell, spheroid and rod-like AuNPs were synthesized by increasing the current with a certain increment, while spheroid and dumbbell AuNPs were obtained by applying constant current. The AuNPs were characterized by TEM, UV-Vis spectrum and surface enhanced Raman spectra (SERS). One absorption band located at near-IR region was observed on the AuNPs, indicating the existence of gold nanorods with the aspect ratio of about 6. The SERS effect from the AuNPs surface was studied by using crystal violet as probe molecules, which adsorbed on AuNPs surface with flat orientation. Meanwhile, the forming mechanism of AuNPs involving crystallization and growth was deduced based on the TEM results. PMID:16544491

  17. Critical View on Electrochemical Impedance Spectroscopy Using the Ferri/Ferrocyanide Redox Couple at Gold Electrodes.

    PubMed

    Vogt, Stephan; Su, Qiang; Gutiérrez-Sánchez, Cristina; Nöll, Gilbert

    2016-04-19

    Electrochemical or faradaic impedance spectroscopy (EIS) using the ferri/ferrocyanide couple as a redox probe at gold working electrodes was evaluated with respect to its ability to monitor consecutive surface modification steps. As a model reaction, the reversible hybridization and dehybridization of DNA was studied. Thiol-modified single stranded DNA (ssDNA, 20 bases, capture probe) was chemisorbed to a gold electrode and treated with a solution of short thiols to release nonspecifically adsorbed DNA before hybridization with complementary ssDNA (20 bases, target) was carried out. Reversible dehybridization was achieved by intense rinsing with pure water. The experimental procedures were optimized by kinetic surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation (QCM-D) measurements to maximize the increase in reflectivity or decrease in frequency upon hybridization before hybridization/dehybridization was also monitored by EIS. In contrast to SPR and QCM-D, repeatable EIS measurements were not possible at first. Combined SPR/EIS and QCM-D/EIS measurements revealed that during EIS the gold surface is seriously damaged due to the presence of CN(-) ions, which are released from the ferri/ferrocyanide redox probe. Even at optimized experimental conditions, etching the gold electrodes could not be completely suppressed and the repeatability of the EIS measurements was limited. In three out of four experimental runs, only two hybridization/dehybridization steps could be monitored reversibly by EIS. Thereafter etching the gold electrode significantly contributed to the EIS spectra whereas the QCM-D response was still repeatable. Hence great care has to be taken when this technique is used to monitor surface modification at gold electrodes.

  18. Critical View on Electrochemical Impedance Spectroscopy Using the Ferri/Ferrocyanide Redox Couple at Gold Electrodes.

    PubMed

    Vogt, Stephan; Su, Qiang; Gutiérrez-Sánchez, Cristina; Nöll, Gilbert

    2016-04-19

    Electrochemical or faradaic impedance spectroscopy (EIS) using the ferri/ferrocyanide couple as a redox probe at gold working electrodes was evaluated with respect to its ability to monitor consecutive surface modification steps. As a model reaction, the reversible hybridization and dehybridization of DNA was studied. Thiol-modified single stranded DNA (ssDNA, 20 bases, capture probe) was chemisorbed to a gold electrode and treated with a solution of short thiols to release nonspecifically adsorbed DNA before hybridization with complementary ssDNA (20 bases, target) was carried out. Reversible dehybridization was achieved by intense rinsing with pure water. The experimental procedures were optimized by kinetic surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation (QCM-D) measurements to maximize the increase in reflectivity or decrease in frequency upon hybridization before hybridization/dehybridization was also monitored by EIS. In contrast to SPR and QCM-D, repeatable EIS measurements were not possible at first. Combined SPR/EIS and QCM-D/EIS measurements revealed that during EIS the gold surface is seriously damaged due to the presence of CN(-) ions, which are released from the ferri/ferrocyanide redox probe. Even at optimized experimental conditions, etching the gold electrodes could not be completely suppressed and the repeatability of the EIS measurements was limited. In three out of four experimental runs, only two hybridization/dehybridization steps could be monitored reversibly by EIS. Thereafter etching the gold electrode significantly contributed to the EIS spectra whereas the QCM-D response was still repeatable. Hence great care has to be taken when this technique is used to monitor surface modification at gold electrodes. PMID:26990929

  19. Enhancement of DNA immobilization and hybridization on gold electrode modified by nanogold aggregates.

    PubMed

    Liu, Shu-Feng; Li, Yong-Fang; Li, Jin-Ru; Jiang, Long

    2005-11-15

    Gold electrodes modified by nanogold aggregates (nanogold electrode) were obtained by the electrodeposition of gold nanoparticles onto planar gold electrode. The Electrochemical response of single-stranded DNA (ssDNA) probe immobilization and hybridization with target DNA was measured by cyclic voltammograms (CV) using methylene blue (MB) as an electroactive indicator. An improving method using long sequence target DNA, which greatly enhanced the response signal during hybridization, was studied. Nanogold electrodes could largely increase the immobilization amount of ssDNA probe. The hybridization amount of target DNA could be increased several times for the manifold nanogold electrodes. The detection limit of nanogold electrode for the complementary 16-mer oligonucleotide (target DNA1) and long sequence 55-mer oligonucleotide (target DNA2) could reach the concentration of 10(-9) mol/L and 10(-11) mol/L, respectively, which are far more sensitive than that of the planar electrode.

  20. Nanostructured rough gold electrodes as platforms to enhance the sensitivity of electrochemical genosensors.

    PubMed

    García-Mendiola, T; Gamero, M; Campuzano, S; Revenga-Parra, M; Alonso, C; Pedrero, M; Pariente, F; Pingarrón, J M; Lorenzo, E

    2013-07-25

    An electrochemical DNA genosensor constructed by using rough gold as electrode support is reported in this work. The electrode surface nanopatterning was accomplished by repetitive square-wave perturbing potential (RSWPP). A synthetic 25-mer DNA capture probe, modified at the 5' end with a hexaalkylthiol, able to hybridize with a specific sequence of lacZ gene from the Enterobacteriaceae bacterial family was assembled to the rough gold surface. A 25 bases synthetic sequence fully complementary to the thiolated DNA capture probe and a 326 bases fragment of lacZ containing a fully matched sequence with the capture probe, which was amplified by a specific asymmetric polymerase chain reaction (aPCR), were employed as target sequences. The hybridization event was electrochemically monitored by using two different indicators, hexaammineruthenium (III) chloride showing an electrostatic DNA binding mode, and pentaamineruthenium-[3-(2-phenanthren-9-yl-vinyl)-pyridine] (in brief RuL) which binds to double stranded DNA (dsDNA) following an intercalative mechanism. After optimization of the different variables involved in the hybridization and detection reactions, detection limits of 5.30 pg μL(-1) and 10 pg μL(-1) were obtained for the 25-mer synthetic target DNA and the aPCR amplicon, respectively. A RSD value of 6% was obtained for measurements carried out with 3 different genosensors prepared in the same manner. PMID:23845493

  1. Zepto-molar electrochemical detection of Brucella genome based on gold nanoribbons covered by gold nanoblooms

    PubMed Central

    Rahi, Amid; Sattarahmady, Naghmeh; Heli, Hossein

    2015-01-01

    Gold nanoribbons covered by gold nanoblooms were sonoelectrodeposited on a polycrystalline gold surface at −1800 mV (vs. AgCl) with the assistance of ultrasound and co-occurrence of the hydrogen evolution reaction. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and fabrication of a genosensor, and the process of immobilization and hybridization was detected by electrochemical methods, using methylene blue as a redox marker. The proposed method for detection of the complementary sequence, sequences with base-mismatched (one-, two- and three-base mismatches), and the sequence of non-complementary sequence was assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence with a calibration sensitivity of 0.40 μA dm3 mol−1, a linear concentration range of 10 zmol dm−3 to 10 pmol dm−3, and a detection limit of 1.71 zmol dm−3. PMID:26657828

  2. Zepto-molar electrochemical detection of Brucella genome based on gold nanoribbons covered by gold nanoblooms.

    PubMed

    Rahi, Amid; Sattarahmady, Naghmeh; Heli, Hossein

    2015-01-01

    Gold nanoribbons covered by gold nanoblooms were sonoelectrodeposited on a polycrystalline gold surface at -1800 mV (vs. AgCl) with the assistance of ultrasound and co-occurrence of the hydrogen evolution reaction. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and fabrication of a genosensor, and the process of immobilization and hybridization was detected by electrochemical methods, using methylene blue as a redox marker. The proposed method for detection of the complementary sequence, sequences with base-mismatched (one-, two- and three-base mismatches), and the sequence of non-complementary sequence was assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence with a calibration sensitivity of 0.40 μA dm(3) mol(-1), a linear concentration range of 10 zmol dm(-3) to 10 pmol dm(-3), and a detection limit of 1.71 zmol dm(-3). PMID:26657828

  3. Zepto-molar electrochemical detection of Brucella genome based on gold nanoribbons covered by gold nanoblooms

    NASA Astrophysics Data System (ADS)

    Rahi, Amid; Sattarahmady, Naghmeh; Heli, Hossein

    2015-12-01

    Gold nanoribbons covered by gold nanoblooms were sonoelectrodeposited on a polycrystalline gold surface at -1800 mV (vs. AgCl) with the assistance of ultrasound and co-occurrence of the hydrogen evolution reaction. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and fabrication of a genosensor, and the process of immobilization and hybridization was detected by electrochemical methods, using methylene blue as a redox marker. The proposed method for detection of the complementary sequence, sequences with base-mismatched (one-, two- and three-base mismatches), and the sequence of non-complementary sequence was assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence with a calibration sensitivity of 0.40 μA dm3 mol-1, a linear concentration range of 10 zmol dm-3 to 10 pmol dm-3, and a detection limit of 1.71 zmol dm-3.

  4. Zepto-molar electrochemical detection of Brucella genome based on gold nanoribbons covered by gold nanoblooms.

    PubMed

    Rahi, Amid; Sattarahmady, Naghmeh; Heli, Hossein

    2015-12-14

    Gold nanoribbons covered by gold nanoblooms were sonoelectrodeposited on a polycrystalline gold surface at -1800 mV (vs. AgCl) with the assistance of ultrasound and co-occurrence of the hydrogen evolution reaction. The nanostructure, as a transducer, was utilized to immobilize a Brucella-specific probe and fabrication of a genosensor, and the process of immobilization and hybridization was detected by electrochemical methods, using methylene blue as a redox marker. The proposed method for detection of the complementary sequence, sequences with base-mismatched (one-, two- and three-base mismatches), and the sequence of non-complementary sequence was assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence with a calibration sensitivity of 0.40 μA dm(3) mol(-1), a linear concentration range of 10 zmol dm(-3) to 10 pmol dm(-3), and a detection limit of 1.71 zmol dm(-3).

  5. Synthesis of sub-nanometer gold particles on modified silica.

    PubMed

    Beloqui Redondo, A; Ranocchiari, M; van Bokhoven, J A

    2016-02-21

    The deposition of gold on silica tends to give large particles when using conventional techniques. We report the preparation of 0.8 ± 0.2 nm particles on a modified SBA-15 support. The method involves the functionalization of silica with amine groups and deposition of gold at basic pH. These catalysts are highly active and selective in the dehydrogenation of formic acid. PMID:26754911

  6. Electrochemical immunosensor for detection of topoisomerase based on graphene-gold nanocomposites.

    PubMed

    Zhong, Guang-Xian; Wang, Peng; Fu, Fei-Huan; Weng, Shao-Huang; Chen, Wei; Li, Shao-Guang; Liu, Ai-Lin; Wu, Zhao-Yang; Zhu, Xia; Lin, Xin-Hua; Lin, Jian-Hua; Xia, Xing-Hua

    2014-07-01

    A facile electrochemical immunosensor based on graphene-three dimensional nanostructure gold nanocomposites (G-3D Au) using simple and rapid one-step electrochemical co-reduction technique was developed for sensitive detection of topoisomerase. The resultant G-3D Au nanocomposites were characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy, and then were used as a substrate for construction of the "sandwich-type" immunosensor. Amperometric current-time curve was employed to monitor the immunoreaction on the protein modified electrode. The proposed method could respond to topoisomerase with a linear calibration range from 0.5 ng mL(-1) to 50 ng mL(-1) with a detection limit of 10 pg mL(-1). This new biosensor exhibited a fast amperometric response, high sensitivity and selectivity, and was successfully used in determining the topoisomerase which was added in human serum with a relative standard deviation (n=5)<5%. The immunosensor served as a significant step toward the practical application of the immunosensor in clinical diagnosis and prognosis monitor.

  7. Batch fabrication of gold-gold nanogaps by E-beam lithography and electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Wu, Yexian; Hong, Wenjing; Akiyama, Terunobu; Gautsch, Sebastian; Kolivoska, Viliam; Wandlowski, Thomas; de Rooij, Nico F.

    2013-06-01

    We report on the successful development of a well-controlled two-step batch nano-fabrication process to achieve nanometer-size gaps at the wafer scale. The technique is based on an optimized electron-beam lithography process, which enables the fabrication of nanogaps in the range (15 ± 4) nm. Following this first step, the feedback-controlled electrochemical deposition of gold from an aqueous HAuCl4-based electrolyte is applied to further reduce the size of the gap down to about 0.3-1.0 nm. This protocol was successfully demonstrated by fabricating more than 385 nanogaps on a 4 inch wafer. The reproducible fabrication of nanogaps in the range between 0.3 and 1.0 nm opens up new perspectives for addressing the electrical and reactivity properties of single molecules and clusters in confined space under well-controlled conditions.

  8. Electrochemical aptasensor of cellular prion protein based on modified polypyrrole with redox dendrimers.

    PubMed

    Miodek, A; Castillo, G; Hianik, T; Korri-Youssoufi, H

    2014-06-15

    This work consists of the development of an electrochemical aptasensor based on polyprrole modified with redox dendrimers, able to detect human cellular prions PrP(C) with high sensitivity. The gold surface was modified by conductive polypyrrole film coupled to polyamidoamine dendrimers of fourth generation (PAMAM G4) and ferrocenyl group as redox marker. The aptamers were immobilized on the surface via biotin/streptavidin chemistry. Electrochemical signal was detected by ferrocenyl group incorporated between dendrimers and aptamers layers. We demonstrated that the interaction between aptamer and prion protein led to variation in electrochemical signal of the ferrocenyl group. The kinetics parameters (diffusion coefficient D and heterogeneous constant transfer ket) calculated from electrochemical signals demonstrate that the variation in redox signal results from the lower diffusion process of ions during redox reaction after prion interaction due to bulk effect of larger protein. The association of redox dendrimers with conducting polypyrrole leads to high sensitivity of PrP(C) determination with detection limit of 0.8 pM, which is three orders of magnitude lower, compared to flat ferrocene-functionalized polypyrrole. Detection of PrP(C) in spiked blood plasma has been achieved and demonstrated a recovery up to 90%. PMID:24480126

  9. Electrochemical aptasensor of cellular prion protein based on modified polypyrrole with redox dendrimers.

    PubMed

    Miodek, A; Castillo, G; Hianik, T; Korri-Youssoufi, H

    2014-06-15

    This work consists of the development of an electrochemical aptasensor based on polyprrole modified with redox dendrimers, able to detect human cellular prions PrP(C) with high sensitivity. The gold surface was modified by conductive polypyrrole film coupled to polyamidoamine dendrimers of fourth generation (PAMAM G4) and ferrocenyl group as redox marker. The aptamers were immobilized on the surface via biotin/streptavidin chemistry. Electrochemical signal was detected by ferrocenyl group incorporated between dendrimers and aptamers layers. We demonstrated that the interaction between aptamer and prion protein led to variation in electrochemical signal of the ferrocenyl group. The kinetics parameters (diffusion coefficient D and heterogeneous constant transfer ket) calculated from electrochemical signals demonstrate that the variation in redox signal results from the lower diffusion process of ions during redox reaction after prion interaction due to bulk effect of larger protein. The association of redox dendrimers with conducting polypyrrole leads to high sensitivity of PrP(C) determination with detection limit of 0.8 pM, which is three orders of magnitude lower, compared to flat ferrocene-functionalized polypyrrole. Detection of PrP(C) in spiked blood plasma has been achieved and demonstrated a recovery up to 90%.

  10. Glucose biosensors based on a gold nanodendrite modified screen-printed electrode

    NASA Astrophysics Data System (ADS)

    Liu, Hsi-Chien; Tsai, Chung-Che; Wang, Gou-Jen

    2013-05-01

    In this study, an enzymatic glucose biosensor based on a three-dimensional gold nanodendrite (GND) modified screen-printed electrode was developed. The GNDs were electrochemically synthesized on the working electrode component of a commercially available screen-printed electrode using a solution acquired by dissolving bulk gold in aqua regia as the precursor. The 3D GND electrode greatly enhanced the effective sensing area of the biosensor, which improved the sensitivity of glucose detection. Actual glucose detections demonstrated that the fabricated devices could perform at a sensitivity of 46.76 μA mM-1 cm-2 with a linear detection range from 28 μM-8.4 mM and detection limit of 7 μM. A fast response time (˜3 s) was also observed. Moreover, only a 20 μl glucose oxidase is required for detection owing to the incorporation of the commercially available screen-printed electrode.

  11. In situ monitoring of the Li-O2 electrochemical reaction on nanoporous gold using electrochemical AFM.

    PubMed

    Wen, Rui; Byon, Hye Ryung

    2014-03-11

    The lithium-oxygen (Li-O2) electrochemical reaction on nanoporous gold (NPG) is observed using in situ atomic force microscopy (AFM) imaging coupled with potentiostatic measurement. Dense Li2O2 nanoparticles form a film at 2.5 V, which is decomposed at 3.8-4.0 V in an ether-based electrolyte.

  12. In situ monitoring of the Li-O2 electrochemical reaction on nanoporous gold using electrochemical AFM.

    PubMed

    Wen, Rui; Byon, Hye Ryung

    2014-03-11

    The lithium-oxygen (Li-O2) electrochemical reaction on nanoporous gold (NPG) is observed using in situ atomic force microscopy (AFM) imaging coupled with potentiostatic measurement. Dense Li2O2 nanoparticles form a film at 2.5 V, which is decomposed at 3.8-4.0 V in an ether-based electrolyte. PMID:24469227

  13. A novel electrochemical aptasensor based on single-walled carbon nanotubes, gold electrode and complimentary strand of aptamer for ultrasensitive detection of cocaine.

    PubMed

    Taghdisi, Seyed Mohammad; Danesh, Noor Mohammad; Emrani, Ahmad Sarreshtehdar; Ramezani, Mohammad; Abnous, Khalil

    2015-11-15

    Cocaine is a strong central nervous system stimulant and one of the most commonly abused drugs. In this study, an electrochemical aptasensor was designed for sensitive and selective detection of cocaine, based on single-walled carbon nanotubes (SWNTs), gold electrode and complimentary strand of aptamer (CS). This electrochemical aptasensor inherits properties of SWNTs and gold such as large surface area and high electrochemical conductivity, as well as high affinity and selectivity of aptamer toward its target and the stronger interaction of SWNTs with single-stranded DNA (ssDNA) than double-stranded DNA (dsDNA). In the absence of cocaine, a little amount of SWNTs bind to Aptamer-CS-modified electrode, so that the electrochemical signal is weak. In the presence of cocaine, aptamer binds to cocaine, leaves the surface of electrode. So that, a large amount of SWNTs bind to CS-modified electrode, generating to a strong electrochemical signal. The designed electrochemical aptasensor showed good selectivity toward cocaine with a limit of detection (LOD) as low as 105 pM. Moreover, the fabricated electrochemical aptasensor was successfully applied to detect cocaine in serum with a LOD as low as 136 pM.

  14. A novel and highly sensitive acetyl-cholinesterase biosensor modified with hollow gold nanospheres.

    PubMed

    Sun, Xia; Zhai, Chen; Wang, Xiangyou

    2013-03-01

    In this work, a highly sensitive acetylcholinesterase (AChE) inhibition-based amperometric biosensor has been developed. Firstly, a glassy carbon electrode (GCE) was modified with chitosan (Chits). Then, hollow gold nanospheres (HGNs) were absorbed onto the surface of chitosan based on the strong affinity through electrostatic adsorption. After that, L-cysteine (L-cys) was assembled on HGNs through Au-S bond. The hollow gold nanospheres were prepared by using Co nanoparticles as sacrificial templates and characterized by scanning electron microscopy, transmission electron microscopy and ultraviolet spectra, respectively. Finally, AChE was immobilized with covalent binding via -COOH groups of L-cysteine onto the modified GCE. The AChE biosensor fabrication process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy methods with the use of ferricyanide as an electrochemical redox indicator. Under optimum conditions, the inhibition rates of pesticides were proportional to their concentrations in the range of 0.1-150 and 0.1-200 μg L(-1) for chlorpyrifos and carbofuran, respectively, the detection limits were 0.06 μg L(-1) for chlorpyrifos and 0.08 μg L(-1) for carbofuran. Moreover, the biosensor exhibited a good stability and reproducibility and was suitable for trace detection of pesticide residues in vegetables and fruits.

  15. Surface modified gold nanowires for mammalian cell transfection

    NASA Astrophysics Data System (ADS)

    Kuo, Chiung-Wen; Lai, Jun-Jung; Wei, Kung Hwa; Chen, Peilin

    2008-01-01

    Aminothiol modified gold nanowires have been used as vectors for the delivery of plasmid DNA into two different types of mammalian cells: 3T3 and HeLa. It was measured that positively charged gold nanowires with a diameter of 200 nm and a length around 5 µm were capable of carrying 1 pg of plasmid DNA per nanowire into cells. Compared with other transfection reagents, the gold nanowires exhibited the highest transfection efficiency while almost no cytotoxicity was observed. In addition, it has been shown that individual nanowires can be visualized with sub-micrometer resolution, which may allow the use of functionalized multi-segment nanowires as local probes for the investigation of the microenvironment inside cells.

  16. Physical and electrochemical study of halide-modified activated carbons

    NASA Astrophysics Data System (ADS)

    Barpanda, Prabeer

    The current thesis aims to improve the electrochemical capacity of activated carbon electrodes, which enjoy prominent position in commercial electrochemical capacitors. Our approach was to develop electrochemical capacity by developing faradaic pseudocapacitance in carbon through a novel mechanochemical modification using iodine and bromine. Various commercial carbons were mechanochemically modified via solid-state iodation and vapour phase iodine-incorporation. The halidation-induced changes in the structure, composition, morphology, electrical and electrochemical properties of carbon materials were studied using different characterization techniques encompassing XRD, XRF, XPS, Raman spectroscopy, BET study, TEM, SAXS and electrochemical testing followed by an intensive battery of physical and electrochemical characterization. The introduction of iodine into carbon system led to the formation of polyiodide species that were preferentially reacted within the micropore voids within the carbon leading to the development of a faradaic reaction at 3.1V. In spite of the lower surface area of modified carbon, we observed manyfold increase in its electrochemical capacity. Parallel inception of non-faradaic development and faradaic pseudocapacitive reaction led to promising gravimetric, surface area normalized and volumetric capacity in iodated carbons. With promising electrochemical improvement post halidation process, the chemical halidation method was extended to different class of carbons and halides. Carbons ranging from amorphous (activated) carbons to crystalline carbons (graphites, fluorographites) were iodine-modified to gain further insight on the local graphite-iodine chemical interaction. In addition, the effect of pore size distribution on chemical iodation process was studied by using in-house fabricated microporous carbon. A comparative study of commercial mesoporous carbons and in-house fabricated microporous carbons showed higher iodine-uptake ability and

  17. Fabrication of graphene/gold-modified screen-printed electrode for detection of carcinoembryonic antigen.

    PubMed

    Chan, K F; Lim, H N; Shams, N; Jayabal, S; Pandikumar, A; Huang, N M

    2016-01-01

    Immunosensors based on gold nanoparticles and reduced graphene oxide (AuNPs/rGO)-modified screen-printed electrodes (SPEs) were successfully synthesized using an electrochemical deposition method. The modified SPEs were characterized using a field emission scanning electron microscope (FESEM) and Raman spectroscopy to analyze the morphology and composition of AuNPs and rGO. Both the FESEM and Raman spectroscopy revealed that the AuNPs were successfully anchored on the thin film of rGO deposited on the surface of the SPEs. Characterization with a ferri-ferrocyanide couple [Fe(CN)6(3-/4-)] showed that the electron transfer kinetic between the analyte and electrode was enhanced after the modification with the AuNPs/rGO composite on the electrode surface, in addition to increasing the effective surface area of the electrode. The modified SPE was immobilized with a sandwich type immunosensor to mimic the ELISA (enzyme-linked immunosorbent assay) immunoassay. The modified SPE that was fortified with the sandwich type immunosensor exhibited double electrochemical responses in the detection of carcinoembryonic antigen (CEA), with linear ranges of 0.5-50 ng/mL and 250-2000 ng/mL and limits of detection of 0.28 ng/mL and 181.5 ng/mL, respectively. PMID:26478358

  18. Electrogenerated chemiluminesence method for the determination of riboflavin at an ionic liquid modified gold electrode

    NASA Astrophysics Data System (ADS)

    Qi, Honglan; Cao, Zongze; Hou, Lina

    2011-01-01

    A highly sensitive electrogenerated chemiluminesence (ECL) method for the determination of riboflavin was developed based on the enhancement of ECL intensity of lucigenin at room temperature ionic liquids (RTILs) modified gold electrode. RTILs modified gold electrode exhibited excellent electrochemical and ECL property to lucigenin system and the ECL intensity of lucigenin was greatly enhanced by riboflavin. The characterization of the RTILs modified electrode and the attractive performance of the sensitive ECL method for the determination of riboflavin were investigated. Under the optimized conditions, the ECL intensity was directly proportional to the concentration of riboflavin in the range from 5.0 × 10 -10 g/mL to 1.0 × 10 -8 g/mL with the detection limit of 1 × 10 -10 g/mL. The method has been applied to the determination of riboflavin in the pharmaceutical preparations with satisfactory recovery from 96% to 101%. This work demonstrates that the incorporation of ECL method with RTILs modified electrode is a promising strategy for the determination of organic compounds with high sensitivity and good reproducibility.

  19. Simultaneous determination of hydroquinone and catechol at gold nanoparticles mesoporous silica modified carbon paste electrode.

    PubMed

    Tashkhourian, J; Daneshi, M; Nami-Ana, F; Behbahani, M; Bagheri, A

    2016-11-15

    A new electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode (AuNPs-MPS) was developed for simultaneous determination of hydroquinone and catechol. Morphology and structure of the AuNPs-MPS were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical behavior of hydroquinone and catechol were investigated using square wave voltammetry and the results indicate that the electrochemical responses are improved significantly at the modified electrode. The observed oxidative peaks separation of about 120mV made possible the simultaneous determination of hydroquinone and catechol in their binary-mixture. Under the optimized condition, a linear dynamic range of 10.0μM-1.0mM range for hydroquinone with the detection limit of 1.2μM and from 30.0μM-1.0mM for catechol with the detection limit of 1.1μM were obtained. The applicability of the method was demonstrated by the recovery studies of hydroquinone and catechol in spiked tap water samples. PMID:27420383

  20. An intimately bonded titanate nanotube-polyaniline-gold nanoparticle ternary composite as a scaffold for electrochemical enzyme biosensors.

    PubMed

    Liu, Xiaoqiang; Zhu, Jie; Huo, Xiaohe; Yan, Rui; Wong, Danny K Y

    2016-03-10

    In this work, titanate nanotubes (TNTs), polyaniline (PANI) and gold nanoparticles (GNPs) were assembled to form a ternary composite, which was then applied on an electrode as a scaffold of an electrochemical enzyme biosensor. The scaffold was constructed by oxidatively polymerising aniline to produce an emeraldine salt of PANI on TNTs, followed by gold nanoparticle deposition. A novel aspect of this scaffold lies in the use of the emeraldine salt of PANI as a molecular wire between TNTs and GNPs. Using horseradish peroxidase (HRP) as a model enzyme, voltammetric results demonstrated that direct electron transfer of HRP was achieved at both TNT-PANI and TNT-PANI-GNP-modified electrodes. More significantly, the catalytic reduction current of H2O2 by HRP was ∼75% enhanced at the TNT-PANI-GNP-modified electrode, compared to that at the TNT-PANI-modified electrode. The heterogeneous electron transfer rate constant of HRP was found to be ∼3 times larger at the TNT-PANI-GNP-modified electrode than that at the TNT-PANI-modified electrode. Based on chronoamperometric detection of H2O2, a linear range from 1 to 1200 μM, a sensitivity of 22.7 μA mM(-1) and a detection limit of 0.13 μM were obtained at the TNT-PANI-GNP-modified electrode. The performance of the biosensor can be ascribed to the superior synergistic properties of the ternary composite.

  1. Nanoporous-Gold-Based Hybrid Cantilevered Actuator Dealloyed and Driven by A Modified Rotary Triboelectric Nanogenerator

    PubMed Central

    Li, Xuequan; Liu, Mengmeng; Huang, Baisheng; Liu, Hong; Hu, Weiguo; Shao, Li-Hua; Wang, Zhong Lin

    2016-01-01

    We firstly designed an electrochemical system for dealloying to synthesize nanoporous gold (NPG) and also driving the novel NPG based actuator by utilizing a modified rotary triboelectric nanogenerator (TENG). Compared to the previous reported TENG whose outputs decline due to temperature rising resulting from electrodes friction, the modified TENG with a cooling system has stable output current and voltage increased by 14% and 20%, respectively. The novel cantilevered hybrid actuator characterised by light-weight (ca. 3 mg) and small volume (ca. 30 mm × 2 mm × 10 μm) is driven by a microcontroller modulated TENG with the displacement of 2.2 mm, which is about 106 times larger than that of traditional cantilever using planar surfaces. The energy conversion efficiencies defined as the energy consumed during dealloying and actuation compared with the output of TENG are 47% and 56.7%, respectively. PMID:27063987

  2. Electrical Impedance Analysis of Mammalian Cells Cultured on Polypyrrole-modified Gold Microlectrodes

    NASA Astrophysics Data System (ADS)

    Chen, Guo; Keese, Charles R.; Giaever, Ivar

    2003-03-01

    In the present study we describe an electrical impedance analysis of BSC cells cultured on gold electrodes (250 im in diameter) that were modified with polypyrrole/heparin composites using electrochemical deposition. Atomic force microscope images show that the composite layer has a porous bulk structure and a very rough surface topology. An electrical technique, referred to as ECIS, was used to measure the impedance of both the cell-covered and the cell-free microelectrodes at frequencies from 25 Hz to 60000 Hz. The electrical characteristics of the system can be modeled with 3 parameters, the intercellular resistance (R_b), the cellular membrane (C_m) and the cell-substrate separation (α). When cells are cultured on the polypyrrole-modified microelectrodes, the contribution to the total resistance from α is decreased, which opens a way to eliminate the contribution arising from α so that Rb and Cm can be directly measured.

  3. Comparative study of label-free electrochemical immunoassay on various gold nanostructures

    NASA Astrophysics Data System (ADS)

    Rafique, S.; Gao, C.; Li, C. M.; Bhatti, A. S.

    2013-10-01

    Electrochemical methods such as amperometry and impedance spectroscopy provide the feasibility of label-free immunoassay. However, the performance of electrochemical interfaces varies with the shape of gold nanostructures. In the present work three types of gold nanostructures including pyramid, spherical, and rod-like nanostructures were electrochemically synthesized on the gold electrode and were further transformed into immunosensor by covalent binding of antibodies. As a model protein, a cancer biomarker, Carcinoembryonic Antigen (CEA) was detected using amperometric and impedimetric techniques on three nanostructured electrodes, which enabled to evaluate and compare the immunoassay's performance. It was found that all three immunosensors showed improved linear electrochemical response to the concentration of CEA compared to bare Au electrode. Among all the spherical gold nanostructure based immunosensors displayed superior performance. Under optimal condition, the immunosensors exhibited a limit of detection of 4.1 pg ml-1 over a concentration range of five orders of magnitude. This paper emphasizes that fine control over the geometry of nanostructures is essentially important for high-performance electrochemical immunoassay.

  4. Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold

    NASA Technical Reports Server (NTRS)

    Porter, Marc D. (Inventor); Weisshaar, Duane E. (Inventor)

    1998-01-01

    An electrochemical method for forming a partial monomolecular layer of a predetermined extent of coverage of a thiolate of the formula, XRS--, therein R can be a linear or branched chain hydrocarbon or an aromatic or the like and X can be any compatible end group, e.g., OH, COOH, CH.sub.3 or the like, upon a substrate such as gold, which involves applying in an electrochemical system a constant voltage preselected to yield the desired predetermined extent of coverage.

  5. Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold

    DOEpatents

    Porter, Marc D.; Weisshaar, Duane E.

    1998-10-27

    An electrochemical method for forming a partial monomolecular layer of a predetermined extent of coverage of a thiolate of the formula, XRS--, therein R can be a linear or branched chain hydrocarbon or an aromatic or the like and X can be any compatible end group, e.g., OH, COOH, CH.sub.3 or the like, upon a substrate such as gold, which involves applying in an electrochemical system a constant voltage preselected to yield the desired predetermined extent of coverage.

  6. Recent progress in electrochemical oxidation of saccharides at gold and copper electrodes in alkaline solutions.

    PubMed

    Torto, Nelson

    2009-09-01

    This article reviews the progress made in the past 10 years, on electrochemical oxidation of saccharides in alkaline media for gold and copper electrodes. The mechanism and processes associated with the electrochemical oxidation of saccharides at native and surface coated electrodes continues to be of great interest. Despite the effort and various mechanisms proposed, still the need for an electrochemically active material that understands the complexity associated with saccharides continues to increase as their detection poses a challenge for bioanalytical chemistry and liquid chromatography.

  7. Fabrication Of Atomic-scale Gold Junctions By Electrochemical Plating Technique Using A Common Medical Disinfectant

    NASA Astrophysics Data System (ADS)

    Umeno, Akinori; Hirakawa, Kazuhiko

    2005-06-01

    Iodine tincture, a medical liquid familiar as a disinfectant, was introduced as an etching/deposition electrolyte for the fabrication of nanometer-separated gold electrodes. In the gold dissolved iodine tincture, the gold electrodes were grown or eroded slowly in atomic scale, enough to form quantum point contacts. The resistance evolution during the electrochemical deposition showed plateaus at integer multiples of the resistance quantum, (2e2/h)-1, at the room temperature. The iodine tincture is a commercially available common material, which makes the fabrication process to be the simple and cost effective. Moreover, in contrast to the conventional electrochemical approaches, this method is free from highly toxic cyanide compounds or extraordinary strong acid. We expect this method to be a useful interface between single-molecular-scale structures and macroscopic opto-electronic devices.

  8. Fabrication of atomic-scale gold junctions by electrochemical plating using a common medical liquid

    NASA Astrophysics Data System (ADS)

    Umeno, A.; Hirakawa, K.

    2005-04-01

    Fabrication of nanometer-separated gold junctions has been performed using "iodine tincture," a medical liquid known as a disinfectant, as an etching/deposition electrolyte. In the gold-dissolved iodine tincture, gold electrodes were grown or eroded slowly enough to form quantum point contacts in an atomic scale. The resistance evolution during the electrochemical deposition showed plateaus at integer multiples of the resistance quantum, (2e2/h)-1, at room temperature (e: the elementary charge, h: the Planck constant). Iodine tincture is a commercially available common material, which makes the fabrication process to be simple and cost effective. Moreover, in contrast to the conventional electrochemical approaches, this method is free from highly toxic cyanide compounds or extraordinarily strong acids.

  9. Site-selective immobilization of gold nanoparticles on graphene sheets and its electrochemical properties

    NASA Astrophysics Data System (ADS)

    Lee, Jea Uk; Lee, Wonoh; Yoon, Sang Su; Kim, Jungwook; Byun, Joon Hyung

    2014-10-01

    The site-selective attachment of metal nanoparticles (NPs) on graphene surface is highly desirable for various applications such as electrochemical sensors and catalysts. Here, we present a simple and effective synthetic approach for the site-selective immobilization of gold NPs (AuNPs) on either basal planes or edges of graphene sheets. The basic principle of this approach is to use cyteamine linker with reactive amine and thiol functional groups at each end, where the amine groups at one end covalently bind to functional groups presented on edges and/or basal planes of chemically synthesized graphene sheets, and the thiol groups at the other end assemble onto pre-synthesized AuNPs through thiol-Au interaction. Due to the difference in the spatial distribution of functional groups presented on graphene oxide (GO) and reduced graphene oxide (rGO) sheets, most of AuNPs are homogeneously immobilized on the basal planes of the cysteamine-functionalized graphene oxide (GO-SH) sheets, whereas AuNPs are selectively attached at the edge parts of the cysteamine-functionalized reduced graphene oxide (rGO-SH) sheets. Raman signals of GO-SH/Au hybrid films with the high content of AuNPs in the hybrids are clearly increased owing to the formation of the charge-transfer complex between AuNPs and GO-SH sheets, exhibiting surface-enhanced Raman scattering (SERS) activity. Furthermore, rGO-SH/Au hybrids enhance the electrochemical activity of modified glassy carbon electrodes owing to the synergetic effects of electrical conduction by the restored aromatic structure of rGO sheets and percolated network of AuNPs along the graphene edges

  10. Comparison of electrochemical immunosensors based on gold nano materials and immunoblot techniques for detection of histidine-tagged proteins in culture medium.

    PubMed

    Wasowicz, Michał; Viswanathan, Subramanian; Dvornyk, Anzhela; Grzelak, Krystyna; Kłudkiewicz, Barbara; Radecka, Hanna

    2008-10-15

    In this work, the direct electrochemical determination of poly-histidine tagged proteins using immunosensor based on anti-His (C-term) antibody immobilized on gold electrodes modified with 1,6-hexanedithiol, gold colloid particles or gold nanorods is described. The recombinant histidine-tagged silk proteinase inhibitor protein (rSPI2-His(6)) expressed in Pichia system selected as antigen for this immonosensor. An electrochemical impedance spectroscopy was used as label free detection technique for immune conjugation. The gold nanorods modified electrode layer showed better analytical response than gold nano particles. The linear calibration range was observed between 10 pg/ml and 1 ng/ml with limit of detection 5 pg/ml (S/N=3). Up to four successive assay cycles with retentive sensitivity were achieved for the immunosensors regenerated with 0.2M glycine-HCl buffer, pH 2.8. The performance of this immnosensor were compared with immuoblotting techniques. PMID:18486465

  11. Gold Binding by Native and Chemically Modified Hops Biomasses

    DOE PAGES

    López, M. Laura; Gardea-Torresdey, J. L.; Peralta-Videa, J. R.; de la Rosa, G.; Armendáriz, V.; Herrera, I.; Troiani, H.; Henning, J.

    2005-01-01

    Heavy metals from mining, smelting operations and other industrial processing facilities pollute wastewaters worldwide. Extraction of metals from industrial effluents has been widely studied due to the economic advantages and the relative ease of technical implementation. Consequently, the search for new and improved methodologies for the recovery of gold has increased. In this particular research, the use of cone hops biomass ( Humulus lupulus ) was investigated as a new option for gold recovery. The results showed that the gold binding to native hops biomass was pH dependent from pH 2 to pH 6, with a maximum percentage bindingmore » at pH 3. Time dependency studies demonstrated that Au(III) binding to native and modified cone hops biomasses was found to be time independent at pH 2 while at pH 5, it was time dependent. Capacity experiments demonstrated that at pH 2, esterified hops biomass bound 33.4 mg Au/g of biomass, while native and hydrolyzed hops biomasses bound 28.2 and 12.0 mg Au/g of biomass, respectively. However, at pH 5 the binding capacities were 38.9, 37.8 and 11.4 mg of Au per gram of native, esterified and hydrolyzed hops biomasses, respectively.« less

  12. Electrochemical DNA biosensors based on thin gold films sputtered on capacitive nanoporous niobium oxide.

    PubMed

    Rho, Sangchul; Jahng, Deokjin; Lim, Jae Hoon; Choi, Jinsub; Chang, Jeong Ho; Lee, Sang Cheon; Kim, Kyung Ja

    2008-01-18

    Electrochemical DNA biosensors based on a thin gold film sputtered on anodic porous niobium oxide (Au@Nb(2)O(5)) are studied in detail here. We found that the novel DNA biosensor based on Au@Nb(2)O(5) is superior to those based on the bulk gold electrode or niobium oxide electrode. For example, the novel method does not require any time-consuming cleaning step in order to obtain reproducible results. The adhesion of gold films on the substrate is very stable during electrochemical biosensing, when the thin gold films are deposited on anodically prepared nanoporous niobium oxide. In particular, the novel biosensor shows enhanced biosensing performance with a 2.4 times higher resolution and a three times higher sensitivity. The signal enhancement is in part attributed to capacitive interface between gold films and nanoporous niobium oxide, where charges are accumulated during the anodic and cathodic scanning, and is in part ascribed to the structural stability of DNA immobilized at the sputtered gold films. The method allows for the detection of single-base mismatch DNA as well as for the discrimination of mismatch positions.

  13. Gold nanoparticles modified carbon paste electrode for differential pulse voltammetric determination of eugenol.

    PubMed

    Afzali, Daryoush; Zarei, Somaye; Fathirad, Fariba; Mostafavi, Ali

    2014-10-01

    In the present study, a carbon paste electrode chemically modified with gold nanoparticles was used as a sensitive electrochemical sensor for determination of eugenol. The differential pulse voltammetric method was employed to study the behavior of eugenol on this modified electrode. The effect of variables such as percent of gold nanoparticles, pH of solution, accumulation potential and time on voltammogram peak current were optimized. The proposed electrode showed good oxidation response for eugenol in 0.1 mol L(-1) phosphate buffer solution (pH8) and the peak potential was about +285 mV (vs. Ag/AgCl). The peak current increased linearly with the eugenol concentration in the range of 5-250 μmol L(-1). The detection limit was found to be 2.0 μmol L(-1) and the relative standard deviation was 1.2% (n=7). The effect of interferences on the eugenol peak current was studied. The method has been applied to the determination of eugenol in different real samples, spiked recoveries were in the range of 96%-99%.

  14. Ultrasensitive Electrochemical Biosensor for HIV Gene Detection Based on Graphene Stabilized Gold Nanoclusters with Exonuclease Amplification.

    PubMed

    Wang, Yijia; Bai, Xiaoning; Wen, Wei; Zhang, Xiuhua; Wang, Shengfu

    2015-08-26

    Because human immunodeficiency virus (HIV) has been one of the most terrible viruses in recent decades, early diagnosis of the HIV gene is of great importance for all scientists around the world. In our work, we developed a novel electrochemical biosensor based on one-step ultrasonic synthesized graphene stabilized gold nanocluster (GR/AuNC) modified glassy carbon electrode (GCE) with an exonuclease III (Exo III)-assisted target recycling amplification strategy for the detection of HIV DNA. It is the first time that GR/AuNCs have been used as biosensor platform and aptamer with cytosine-rich base set as capture probe to construct the biosensor. With the combination of cytosine-rich capture probe, good conductivity and high surfaces of GR/AuNCs, and Exo III-assisted target recycling amplification, we realized high sensitivity and good selectivity detection of target HIV DNA with a detection limit of 30 aM (S/N = 3). Furthermore, the proposed biosensor has a promising potential application for target detection in human serum analysis.

  15. Surface-modified gold nanorods for specific cell targeting

    NASA Astrophysics Data System (ADS)

    Wang, Chan-Ung; Arai, Yoshie; Kim, Insun; Jang, Wonhee; Lee, Seonghyun; Hafner, Jason H.; Jeoung, Eunhee; Jung, Deokho; Kwon, Youngeun

    2012-05-01

    Gold nanoparticles (GNPs) have unique properties that make them highly attractive materials for developing functional reagents for various biomedical applications including photothermal therapy, targeted drug delivery, and molecular imaging. For in vivo applications, GNPs need to be prepared with very little or negligible cytotoxicitiy. Most GNPs are, however, prepared using growth-directing surfactants such as cetyl trimethylammonium bromide (CTAB), which are known to have considerable cytotoxicity. In this paper, we describe an approach to remove CTAB to a non-toxic concentration. We optimized the conditions for surface modification with methoxypolyethylene glycol thiol (mPEG), which replaced CTAB and formed a protective layer on the surface of gold nanorods (GNRs). The cytotoxicities of pristine and surface-modified GNRs were measured in primary human umbilical vein endothelial cells and human cell lines derived from hepatic carcinoma cells, embryonic kidney cells, and thyroid papillary carcinoma cells. Cytotoxicity assays revealed that treating cells with GNRs did not significantly affect cell viability except for thyroid papillary carcinoma cells. Thyroid cancer cells were more susceptible to residual CTAB, so CTAB had to be further removed by dialysis in order to use GNRs for thyroid cell targeting. PEGylated GNRs are further modified to present monoclonal antibodies that recognize a specific surface marker, Na-I symporter, for thyroid cells. Antibody-conjugated GNRs specifically targeted human thyroid cells in vitro.

  16. Interpenetrating polyaniline-gold electrodes for SERS and electrochemical measurements

    NASA Astrophysics Data System (ADS)

    West, R. M.; Semancik, S.

    2016-11-01

    Facile fabrication of nanostructured electrode arrays is critical for development of bimodal SERS and electrochemical biosensors. In this paper, the variation of applied potential at a polyaniline-coated Pt electrode is used to selectivity deposit Au on the polyaniline amine sites or on the underlying Pt electrode. By alternating the applied potential, the Au is grown simultaneously from the top and the bottom of the polyaniline film, leading to an interpenetrated, nanostructured polymer-metal composite extending from the Pt electrode to the electrolyte solution. The resulting films have unique pH-dependent electrochemical properties, e.g. they retain electrochemical activity in both acidic and neutral solutions, and they also include SERS-active nanostructures. By varying the concentration of chloroaurate used during deposition, Au nanoparticles, nanodendrites, or nanosheets can be selectively grown. For the films deposited under optimal conditions, using 5 mmol/L chloroaurate, the SERS enhancement factor for Rhodamine 6G was found to be as high as 1.1 × 106 with spot-to-spot and electrode-to-electrode relative standard deviations as low as 8% and 12%, respectively. The advantages of the reported PANI-Au composite electrodes lie in their facile fabrication, enabling the targeted deposition of tunable nanostructures on sensing arrays, and their ability to produce orthogonal optical and electrochemical analytical results.

  17. Electrochemical annealing of nanoporous gold by application of cyclic potential sweeps.

    PubMed

    Sharma, Abeera; Bhattarai, Jay K; Alla, Allan J; Demchenko, Alexei V; Stine, Keith J

    2015-02-27

    An electrochemical method for annealing the pore sizes of nanoporous gold (NPG) is reported. The pore sizes of NPG can be increased by electrochemical cycling with the upper potential limit being just at the onset of gold oxide formation. This study has been performed in electrolyte solutions including potassium chloride, sodium nitrate and sodium perchlorate. Scanning electron microscopy images have been used for ligament and pore size analysis. We examine the modifications of NPG due to annealing using electrochemical impedance spectroscopy, and cyclic voltammetry and offer a comparison of the surface coverage using the gold oxide stripping method as well as the method in which electrochemically accessible surface area is determined by using a diffusing redox probe. The effect of additives adsorbed on the NPG surface when subjected to annealing in different electrolytes as well as the subsequent structural changes in NPG are also reported. The effect of the annealing process on the application of NPG as a substrate for glucose electro-oxidation is briefly examined. PMID:25649027

  18. Electrochemical annealing of nanoporous gold by application of cyclic potential sweeps

    NASA Astrophysics Data System (ADS)

    Sharma, Abeera; Bhattarai, Jay K.; Alla, Allan J.; Demchenko, Alexei V.; Stine, Keith J.

    2015-02-01

    An electrochemical method for annealing the pore sizes of nanoporous gold (NPG) is reported. The pore sizes of NPG can be increased by electrochemical cycling with the upper potential limit being just at the onset of gold oxide formation. This study has been performed in electrolyte solutions including potassium chloride, sodium nitrate and sodium perchlorate. Scanning electron microscopy images have been used for ligament and pore size analysis. We examine the modifications of NPG due to annealing using electrochemical impedance spectroscopy, and cyclic voltammetry and offer a comparison of the surface coverage using the gold oxide stripping method as well as the method in which electrochemically accessible surface area is determined by using a diffusing redox probe. The effect of additives adsorbed on the NPG surface when subjected to annealing in different electrolytes as well as the subsequent structural changes in NPG are also reported. The effect of the annealing process on the application of NPG as a substrate for glucose electro-oxidation is briefly examined.

  19. A novel graphene nanodots inlaid porous gold electrode for electrochemically controlled drug release.

    PubMed

    Wang, Jianmei; Yang, Peng; Cao, Mengmei; Kong, Na; Yang, Wenrong; Sun, Shu; Meng, You; Liu, Jingquan

    2016-01-15

    A uniform graphene nanodots inlaid porous gold electrode was prepared via ion beam sputtering deposition (IBSD) and mild corrosion chemistry. HRTEM, SEM, AFM and XPS analyses revealed the successful fabrication of graphene nanodots inlaid porous gold electrode. The as-prepared porous electrode was used as π-orbital-rich drug loading platform to fabricate an electrochemically controlled drug release system with high performance. π-orbital-rich drugs with amino mioety, like doxorubicin (DOX) and tetracycline (TC), were loaded into the graphene nanodots inlaid porous gold electrode via non-covalent π-π stacking interaction. The amino groups in DOX and TC can be easily protonated at acidic medium to become positively-charged NH3(+), which allow these drug molecules to be desorbed from the porous electrode surface via electrostatic repulsion when positive potential is applied at the electrode. The drug loading and release experiment indicated that this graphene nanodots inlaid porous gold electrode can be used to conveniently and efficiently control the drug release electrochemically. Not only did our work provide a benign method to electrochemically controlled drug release via electrostatic repulsion process, it also enlighten the promising practical applications of micro electrode as a drug carrier for precisely and efficiently controlled drug release via embedding in the body.

  20. Electrochemical Detection of p-Aminophenol by Flexible Devices Based on Multi-Wall Carbon Nanotubes Dispersed in Electrochemically Modified Nafion

    PubMed Central

    Scandurra, Graziella; Antonella, Arena; Ciofi, Carmine; Saitta, Gaetano; Lanza, Maurizio

    2014-01-01

    A conducting composite prepared by dispersing multi-walled carbon nanotubes (MWCNTs) into a host matrix consisting of Nafion, electrochemically doped with copper, has been prepared, characterized and used to modify one of the gold electrodes of simply designed electrochemical cells having copier grade transparency sheets as substrates. Electrical measurements performed in deionized water show that the Au/Nafion/Au-MWCNTs–Nafion:Cu cells can be successfully used in order to detect the presence of p-aminophenol (PAP) in water, without the need for any supporting electrolyte. The intensity of the redox peaks arising when PAP is added to deionized water is found to be linearly related to the analyte in the range from 0.2 to 1.6 μM, with a detection limit of 90 nM and a sensitivity of 7 μA·(μM−1)·cm−2. PMID:24854357

  1. Electrochemical Detection of Hydrazine Using Poly(dopamine)-Modified Electrodes

    PubMed Central

    Lee, Ji Young; Nguyen, Truc Ly; Park, Jun Hui; Kim, Byung-Kwon

    2016-01-01

    We have developed a simple and selective method for the electrochemical detection of hydrazine (HZ) using poly(dopamine) (pDA)-modified indium tin oxide (ITO) electrodes. Modification with pDA was easily achieved by submerging the ITO electrode in a DA solution for 30 min. The electrocatalytic oxidation of HZ on the pDA-modified ITO electrode was measured by cyclic voltammetry. In buffer solution, the concentration range for linear HZ detection was 100 µM–10 mM, and the detection limit was 1 µM. The proposed method was finally used to determine HZ in tap water to simulate the analysis of real samples. This method showed good recovery (94%–115%) and was not affected by the other species present in the tap water samples. PMID:27164108

  2. Electrochemical performance of Si anode modified with carbonized gelatin binder

    NASA Astrophysics Data System (ADS)

    Jiang, Ying; Mu, Daobin; Chen, Shi; Wu, Borong; Cheng, Kailin; Li, Luyu; Wu, Feng

    2016-09-01

    Gelatin is alternatively adopted as the binder to modify Si anode coupling with its carbonization treatment. The binder can provide good bonding and uniform dispersion of the particles besides its environmental benignancy. Importantly, the carbonized binder containing nitrogen will be advantageous to the electrical conductivity of the electrode. In addition, some spaces are formed in the electrode due to the decomposition and shrinkage of the gelatin binder during heat-treatment, which may facilitate electrolyte penetration and accommodate volume change during cycling. All these merits make contribution to the good electrochemical performance of the modified Si electrode. It exhibits a reversible capacity of 990.3 mA h g-1 after 70 cycles at a current density of 100 mA g-1 and 904 mA h g-1 after 100 cycles at 400 mA g-1.

  3. Synergic effect of multi-walled carbon nanotubes and gold nanoparticles towards immunosensing of ricin with carbon nanotube-gold nanoparticles-chitosan modified screen printed electrode.

    PubMed

    Suresh, Srinivasan; Gupta, Manish; Kumar, Gupta Ajay; Rao, Vepa Kameswara; Kumar, Om; Ghosal, Partha

    2012-09-01

    An amperometric immunosensor for the specific detection of Ricinus communis is reported. Screen printed electrodes (SPEs) were modified with gold nanoparticles (GNPs) loaded multiwalled carbon nanotubes (MWCNTs)-chitosan (Ch) film. The ratio of MWCNT and GNP was optimised to get best electrochemically active electrode. Sandwich immunoassay format was used for the immunosensing of ricin. The revealing antibodies tagged with the enzyme alkaline phosphatase (ALP) converts the substrate 1-naphthyl phosphate into 1-naphthol that was determined with the amperometric technique. The amperometric current obtained was correlated with the concentration of ricin. The prepared GNP-MWCNT-Ch-SPE showed high stability due to the Ch film, short response time with good reproducibility and increased shelf life of the electrodes immobilised with antibodies. The electrochemical activity of the electrode improved because of optimization of composition of CNTs and gold nanoparticles. Under the optimal conditions, the modified electrode showed a wide linear response to the concentration of ricin in the range of 2.5-25 ng mL(-1) with a limit of detection of 2.1 ng mL(-1) and with a relative standard deviation of 5.1% and storage life of 32 days.

  4. Electrochemical immunosensor based on nanoporpus gold loading thionine for carcinoembryonic antigen.

    PubMed

    Sun, Xiaobin; Ma, Zhanfang

    2013-05-30

    Nanoporous gold (NPG) has recently received considerable attention in analytical electrochemistry because of its good conductivity and large specific surface area. A facile layer-by-layer assembly technique fabricated NPG was used to construct an electrochemical immunosensor for carcinoembryonic antigen (CEA). NPG was fabricated on glassy carbon (GC) electrode by alternatively assembling gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) using 1,4-benzenedimethanethiol as a cross-linker, and then AgNPs were dissolved with HNO3. The thionine was absorbed into the NPG and then gold nanostructure was electrodeposited on the surface through the electrochemical reduction of gold chloride tetrahydrate (HAuCl4). The anti-CEA was directly adsorbed on gold nanostructure fixed on the GC electrode. The linear range of the immunosensor was from 10 pg mL(-1) to 100 ng mL(-1) with a detection limit of 3 pg mL(-1) (S/N=3). The proposed immunosensor has high sensitivity, wide linear range, low detection limit, and good selectivity. The present method could be widely applied to construct other immunosensors.

  5. Electrochemical Tailoring of Fibrous Polyaniline and Electroless Decoration with Gold and Platinum Nanoparticles.

    PubMed

    Abdelhamid, Muhammad E; Snook, Graeme A; O'Mullane, Anthony P

    2016-09-01

    Presented in this work is a facile and quick electrochemical method for controlling the morphology of thick polyaniline (PANi) films, without the use of templates. By stepping the polymerization potential from high voltages to a lower (or series of lower) voltage(s), we successfully controlled the morphology of the polymer, and fibrous structures, unique to each potential step, were achieved. In addition, the resultant film was tested electrochemically for its viability as an electrode material for flexible batteries and supercapacitors. Furthermore, the PANi film was decorated with gold and platinum nanoparticles via an electroless deposition process for possible electrocatalytic applications, whereby the oxidation of hydrazine at the composite was investigated. PMID:27531044

  6. Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold

    DOEpatents

    Porter, Marc D.; Weisshaar, Duane E.

    1997-06-03

    An electrochemical method for forming a partial monomolecular layer of a predetermined extent of coverage of a thiolate of the formula, XRS.sup.-, wherein R can be a linear or branched chain hydrocarbon or an aromatic or the like and X can be any compatible end group, e.g., OH, COOH, CH.sub.3 or the like, upon a substrate such as gold, which involves applying in an electrochemical system a constant voltage preselected to yield the desired predetermined extent of coverage.

  7. Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold

    DOEpatents

    Porter, M.D.; Weisshaar, D.E.

    1998-10-27

    An electrochemical method is described for forming a partial monomolecular layer of a predetermined extent of coverage of a thiolate of the formula, XRS-, therein R can be a linear or branched chain hydrocarbon or an aromatic or the like and X can be any compatible end group, e.g., OH, COOH, CH{sub 3} or the like, upon a substrate such as gold, which involves applying in an electrochemical system a constant voltage preselected to yield the desired predetermined extent of coverage. 13 figs.

  8. A novel electrochemical sensor surface for the detection of hydrogen peroxide using cyclic bisureas/gold nanoparticle composite.

    PubMed

    Mathew, Manjusha; Sandhyarani, N

    2011-10-15

    A novel electrochemical sensor surface with enhanced sensitivity for the detection of hydrogen peroxide has been developed based on the layer-by-layer assembly of mercapto propionic acid (MPA), cystine-based polymethylene-bridged cyclic bisureas (CBU)/gold nanoparticle (AuNP) and horseradish peroxidase (HRP) on gold electrode. Possibility of a large number of hydrogen bonds, allowed by the chemical and sterical structure of the CBU ensures the proper immobilization of the enzyme in favorable orientation and retention of enzymatic activity. Efficient electron tunneling property of AuNP together with its electrocatalytic activity leads to higher sensitivity in the detection of H(2)O(2). In cyclic voltammetry measurements a cathodic current due to direct electron transfer of HRP is observed which, indicates excellent electrocatalytic activity of the sensor surface. The biosensor surface modified with gold nanoparticle and CBU showed a lower detection limit of 50 nM for hydrogen peroxide. Chronoamperometry is performed at -0.3 V and Michaelis-Menten constant K(M)(app) value is estimated to be 4.5 μM. The newly developed sensor surface showed very high stability, reproducibility and high sensitivity.

  9. Gold nanoparticle modified capacitive sensor platform for multiple marker detection.

    PubMed

    Altintas, Zeynep; Kallempudi, Sreenivasa Saravan; Gurbuz, Yasar

    2014-01-01

    The detection and quantification of cancer biomarkers in human blood is crucial to diagnose patients in the early stage of a disease. The recent advances in biosensor technology can improve detection by reducing the application time and cost without an invasive approach. In this study, a highly sensitive, novel nanoparticle-modified capacitive sensor was developed for the detection of cancer markers. The current work mainly focused on developing a surface modification protocol for achieving higher sensitivity using Au-NPs. An interdigitated electrode (IDE) transducer was modified using gold nanoparticles (Au-NPs) for signal enhancement, the platform was initially optimized with a small size IL-6 protein and the methodology was then applied for multiple marker detection with the aim of precise disease diagnostics. Carcinoembryonic antigen (CEA) and epidermal growth factor receptor (hEGFR) could be successfully detected in the concentration range of 20-1000 pg mL(-1) while cancer antigen 15-3 (CA15-3) was detected in the range of 10-200 U mL(-1). These results show an increase of sensitivity by five-fold with respect to those not modified, demonstrating a highly sensitive and specific capacitive immunoassay that has a great potential for the use of early diagnosis of cancer disease. PMID:24274298

  10. eMethylsorb: electrochemical quantification of DNA methylation at CpG resolution using DNA-gold affinity interactions.

    PubMed

    Sina, Abu Ali Ibn; Howell, Sidney; Carrascosa, Laura G; Rauf, Sakandar; Shiddiky, Muhammad J A; Trau, Matt

    2014-11-01

    We report a simple electrochemical method referred to as "eMethylsorb" for the detection of DNA methylation. The method relies on the base dependent affinity interaction of DNA with gold. The methylation status of DNA is quantified by monitoring the electrochemical current as a function of the relative adsorption level of bisulphite treated DNA samples onto a bare gold electrode. This method can successfully distinguish methylated and unmethylated epigenotypes at single CpG resolution.

  11. Sensitive electrochemical immunosensor based on three-dimensional nanostructure gold electrode.

    PubMed

    Zhong, Guangxian; Lan, Ruilong; Zhang, Wenxin; Fu, Feihuan; Sun, Yiming; Peng, Huaping; Chen, Tianbin; Cai, Yishan; Liu, Ailin; Lin, Jianhua; Lin, Xinhua

    2015-01-01

    A sensitive electrochemical immunosensor was developed for detection of alpha-fetoprotein (AFP) based on a three-dimensional nanostructure gold electrode using a facile, rapid, "green" square-wave oxidation-reduction cycle technique. The resulting three-dimensional gold nanocomposites were characterized by scanning electron microscopy and cyclic voltammetry. A "sandwich-type" detection strategy using an electrochemical immunosensor was employed. Under optimal conditions, a good linear relationship between the current response signal and the AFP concentrations was observed in the range of 10-50 ng/mL with a detection limit of 3 pg/mL. This new immunosensor showed a fast amperometric response and high sensitivity and selectivity. It was successfully used to determine AFP in a human serum sample with a relative standard deviation of <5% (n=5). The proposed immunosensor represents a significant step toward practical application in clinical diagnosis and monitoring of prognosis.

  12. Sensitive electrochemical immunosensor based on three-dimensional nanostructure gold electrode

    PubMed Central

    Zhong, Guangxian; Lan, Ruilong; Zhang, Wenxin; Fu, Feihuan; Sun, Yiming; Peng, Huaping; Chen, Tianbin; Cai, Yishan; Liu, Ailin; Lin, Jianhua; Lin, Xinhua

    2015-01-01

    A sensitive electrochemical immunosensor was developed for detection of alpha-fetoprotein (AFP) based on a three-dimensional nanostructure gold electrode using a facile, rapid, “green” square-wave oxidation-reduction cycle technique. The resulting three-dimensional gold nanocomposites were characterized by scanning electron microscopy and cyclic voltammetry. A “sandwich-type” detection strategy using an electrochemical immunosensor was employed. Under optimal conditions, a good linear relationship between the current response signal and the AFP concentrations was observed in the range of 10–50 ng/mL with a detection limit of 3 pg/mL. This new immunosensor showed a fast amperometric response and high sensitivity and selectivity. It was successfully used to determine AFP in a human serum sample with a relative standard deviation of <5% (n=5). The proposed immunosensor represents a significant step toward practical application in clinical diagnosis and monitoring of prognosis. PMID:25834434

  13. Enhanced performance of dye-sensitized solar cells using gold nanoparticles modified fluorine tin oxide electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Dingwen; Wang, Milton; Brolo, Alexandre G.; Shen, Jie; Li, Xiaodong; Huang, Sumei

    2013-01-01

    We have investigated plasmon-assisted energy conversion in dye-sensitized solar cells (DSCs) applying gold nanoparticles (NPs) modified fluorine tin oxide (FTO) electrodes. A series of Au NPs with different sizes (15-80 nm) were synthesized and immobilized onto FTO glass slides. Photoanodes were prepared on these Au modified FTO substrates using P25 TiO2 powders and by the screen-printing method. The size effects of Au NPs on the photovoltaic performance of the formed DSCs were investigated systematically. Structural and photoelectrochemical properties of the formed photoanodes were examined by field emission scanning electron microscopy and electrochemical impedance spectroscopy. It was found that the energy conversion efficiency of the DSC was highly dependent on the Au particle size. When the particle size was not greater than 60 nm, the DSC based on the Au NP-FTO composite electrode showed a higher short-circuit current density and better photovoltaic (PV) performance than the cell based on the bare FTO. The best cell was achieved using 25 nm sized Au NPs modified FTO. It exhibited a conversion efficiency of 6.69%, which was 15% higher than that of DSCs without Au NPs. The related PV performance enhancement mechanisms, photoelectrochemical processes and surface-plasmon resonances in DSCs with Au nanostructures are analysed and discussed.

  14. Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction.

    PubMed

    Garain, Samiran; Barman, Koushik; Sinha, Tridib Kumar; Jasimuddin, Sk; Haeberle, Jörg; Henkel, Karsten; Schmeisser, Dieter; Mandal, Dipankar

    2016-08-24

    Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce(III)(DMF) (HSO4)3] complex was synthesized and characterized by UV-vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d → 4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [Ce(III)(DMF) (HSO4)3] complex. A stacking electrode was designed where self-assembled l-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The resulting electrode, i.e., [Ce(III)(DMF) (HSO4)3]-l-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈ 0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light. PMID:27490440

  15. Fabrication of aerogel capsule, bromine-doped capsule, and modified gold cone in modified target for the Fast Ignition Realization Experiment (FIREX) Project

    NASA Astrophysics Data System (ADS)

    Nagai, Keiji; Yang, H.; Norimatsu, T.; Azechi, H.; Belkada, F.; Fujimoto, Y.; Fujimura, T.; Fujioka, K.; Fujioka, S.; Homma, H.; Ito, F.; Iwamoto, A.; Jitsuno, T.; Kaneyasu, Y.; Nakai, M.; Nemoto, N.; Saika, H.; Shimoyama, T.; Suzuki, Y.; Yamanaka, K.; Mima, K.

    2009-09-01

    The development of target fabrication for the Fast Ignition Realization EXperiment (FIREX) Project is described in this paper. For the first stage of the FIREX Project (FIREX-I), the previously designed target has been modified by using a bromine-doped ablator and coating the inner gold cone with a low-density material. A high-quality bromine-doped capsule without vacuoles was fabricated from bromine-doped deuterated polystyrene. The gold surface was coated with a low-density material by electrochemical plating. For the cryogenic fuel target, a brand new type of aerogel material, phloroglucinol/formaldehyde (PF), was investigated and encapsulated to meet the specifications of 500 µm diameter and 20 µm thickness, with 30 nm nanopores. Polystyrene-based low-density materials were investigated and the relationship between the crosslinker content and the nanopore structure was observed.

  16. Highly selective dopamine electrochemical sensor based on electrochemically pretreated graphite and nafion composite modified screen printed carbon electrode.

    PubMed

    Ku, Shuhao; Palanisamy, Selvakumar; Chen, Shen-Ming

    2013-12-01

    Herein, we report a highly selective dopamine electrochemical sensor based on electrochemically pretreated graphite/nafion composite modified screen printed carbon (SPC) electrode. Electrochemically activated graphite/nafion composite was prepared by using a simple electrochemical method. Scanning electron microscope (SEM) used to characterize the surface morphology of the fabricated composite electrode. The SEM result clearly indicates that the graphitic basal planes were totally disturbed and leads to the formation of graphite nanosheets. The composite modified electrode showed an enhanced electrocatalytic activity toward the oxidation of DA when compared with either electrochemical pretreated graphite or nafion SPC electrodes. The fabricated composite electrode exhibits a good electrocatalytic oxidation toward DA in the linear response range from 0.5 to 70 μM with the detection limit of 0.023 μM. The proposed sensor also exhibits very good selectivity and stability, with the appreciable sensitivity. In addition, the proposed sensor showed satisfactory recovery results toward the commercial pharmaceutical DA samples.

  17. Electrochemical functionalization of gold and silicon surfaces by a maleimide group as a biosensor for immunological application.

    PubMed

    Zhang, Xin; Tretjakov, Aleksei; Hovestaedt, Marc; Sun, Guoguang; Syritski, Vitali; Reut, Jekaterina; Volkmer, Rudolf; Hinrichs, Karsten; Rappich, Joerg

    2013-03-01

    In the present study we investigated the preparation of biofunctionalized surfaces using the direct electrochemical grafting of maleimidophenyl molecules with subsequent covalent immobilization of specific peptide to detect target antibody, thereby extending the application of the biosensing systems towards immunodiagnostics. Para-maleimidophenyl (p-MP) functional groups were electrochemically grafted on gold and silicon surfaces from solutions of the corresponding diazonium salt. A specially synthesized peptide modified with cysteine (Cys-peptide) was then immobilized on the p-MP grafted substrates by cross-linking between the maleimide groups and the sulfhydryl group of the cysteine residues. Accordingly, the Cys-peptide worked as an antigen that was able to bind specifically the target antibody (anti-GST antibody), while it was non-sensitive to a negative contrast antibody (i.e. anti-Flag β). The immobilization of both specific and non-specific antibodies on the Cys-peptide-modified surfaces was monitored by infrared spectroscopic ellipsometry, a quartz crystal microbalance integrated in flow injection analysis system and potentiometric response. The results obtained clearly demonstrated that the direct modification of a surface with maleimidophenyl provides a very simple and reliable way of preparing biofunctionalized surfaces suitable for the construction of immunological biosensors.

  18. RECOGNITION OF PYRENE USING MOLECULARLY-IMPRINTED ELECTROCHEMICALLY-DEPOSITED POLY (2-MERCAPTOBENZIMIDAZOLE) OR POLY(RESORCINOL) ON GOLD ELECTRODES

    EPA Science Inventory

    The feasibility of using thiol chemistry to form molecularly imprinted polymer-coated gold electrodes to measure pyrene is reported. For the first approach, poly(2-mercaptoimidazole) (2-MBI) was electrochemically deposited on gold electrodes in the presence or absence of the tem...

  19. An electrochemical DNA biosensor based on gold nanorods decorated graphene oxide sheets for sensing platform.

    PubMed

    Han, Xiaowei; Fang, Xian; Shi, Anqi; Wang, Jiao; Zhang, Yuzhong

    2013-12-15

    A simple electrochemical sensor for sensitive and selective DNA detection was constructed based on gold nanorods (Au NRs) decorated graphene oxide (GO) sheets. The high-quality Au NRs-GO nanocomposite was synthesized via the electrostatic self-assembly technique, which is considered a potential sensing platform. Differential pulse voltammetry was used to monitor the DNA hybridization event using methylene blue as an electrochemical indicator. Under optimal conditions, the peak currents of methylene blue were linear with the logarithm of the concentrations of complementary DNA from 1.0 × 10(-9) to 1.0 × 10(-14)M with a detection limit of 3.5 × 10(-15)M (signal/noise=3). Moreover, the prepared electrochemical sensor can effectively distinguish complementary DNA sequences in the presence of a large amount of single-base mismatched DNA (1000:1), indicating that the biosensor has high selectivity.

  20. Electrochemical impediometric detection of anti-HIV drug taking gold nanorods as a sensing interface.

    PubMed

    Narang, Jagriti; Malhotra, Nitesh; Singh, Gajendra; Pundir, C S

    2015-04-15

    In present work, gold nanorods were used for amplification of electrochemical sensing of anti-HIV replication drug i.e. deferiprone. Gold nanorods (nano Au) deposited onto pencil graphite electrode (PGE) has been utilized for covalent immobilization of horse radish peroxidase (HRP), via glutaraldehyde (Glu), for deferiprone detection using impedimetric technique. Gold nanorods (nano Au) prepared were characterized by TEM and XRD. The resulting nano Au sensor exhibited a good response to deferiprone with a wide linear range (0.005-1000µM) and a low detection limit 0.005µM. The biosensor also showed a short response time (within 15s). In addition, the biosensor exhibited high reproducibility, good storage stability and anti-interference ability. The applicability of the nano Au sensor is to determine deferiprone level in spiked urine and serum samples. PMID:25437372

  1. Electrochemical measurements on a droplet using gold microelectrodes

    NASA Astrophysics Data System (ADS)

    Jenabi, Amin; Souri, Asma; Rastkhadiv, Ali

    2016-03-01

    Facile methods of ion recognition are important for the fabrication of electronic tongue systems. In this work, we demonstrate performing pulsed conductometry on microliter electrolyte droplets dropped on gold microelectrodes vapor deposited on soda lime glass slides. A droplet is dropped between two microelectrodes when a voltage waveform from a preprogramed power supply is applied on them. The temporal variation of the electric current passing through the droplet is recorded, digitized and stored. The obtained data are compared with the database formed out of the previous experiences for the classification of the sample electrolytes. It is shown that the shape of the voltage waveform is the important parameter of the process. We devised a method for the optimization of the voltage waveform profile for obtaining the maximum of discriminating information from the recorded current variations.

  2. Sensitive Electrochemical Detection of Enzymatically-generated Thiocholine at Carbon Nanotube Modified Glassy Carbon Electrode

    SciTech Connect

    Liu, Guodong; Riechers, Shawn L.; Mellen, Maria C.; Lin, Yuehe

    2005-11-01

    A carbon nanotube modified glassy-carbon (CNT/GC) electrode was used for enhancing the sensitivity of electrochemical measurements of enzymatically-generated thiocholine. Cyclic voltammetric and amperometric characteristics of thiocholine at CNT/GC, glassy carbon, carbon paste, and gold electrodes were compared. The CNT layer leads to a greatly improved anodic detection of enzymatically generated thiocholine product including lower oxidation overpotential (0.15 V) and higher sensitivity because of its electrocatalytic activity, fast electron transfer and large surface area. The sensor performance was optimized with respect to the operating conditions. Under the optimal batch conditions, a detection limit of 5 ?10 -6 mol/L was obtained with good precision (RSD = 5.2%, n=10). Furthermore, the attractive response of thiocholine on a CNT/GC electrode has allowed it to be used for constant-potential flow injection analysis. The detection limit was greatly improved to 0.3 ?10-6 mol/L. The high sensitivity electrochemical detection of enzymatically generated thiocholine with a CNT sensing platform holds great promise to prepare an acetylcholinesterase biosensor for monitoring organophosphate pesticides and nerve agents.

  3. Human sulfite oxidase electrochemistry on gold nanoparticles modified electrode.

    PubMed

    Frasca, Stefano; Rojas, Oscar; Salewski, Johannes; Neumann, Bettina; Stiba, Konstanze; Weidinger, Inez M; Tiersch, Brigitte; Leimkühler, Silke; Koetz, Joachim; Wollenberger, Ulla

    2012-10-01

    The present study reports a facile approach for sulfite biosensing, based on enhanced direct electron transfer of a human sulfite oxidase (hSO) immobilized on a gold nanoparticles modified electrode. The spherical core shell AuNPs were prepared via a new method by reduction of HAuCl(4) with branched poly(ethyleneimine) in an ionic liquids resulting particles with a diameter less than 10nm. These nanoparticles were covalently attached to a mercaptoundecanoic acid modified Au-electrode where then hSO was adsorbed and an enhanced interfacial electron transfer and electrocatalysis was achieved. UV/Vis and resonance Raman spectroscopy, in combination with direct protein voltammetry, are employed for the characterization of the system and reveal no perturbation of the structural integrity of the redox protein. The proposed biosensor exhibited a quick steady-state current response, within 2 s, a linear detection range between 0.5 and 5.4 μM with a high sensitivity (1.85 nA μM(-1)). The investigated system provides remarkable advantages in the possibility to work at low applied potential and at very high ionic strength. Therefore these properties could make the proposed system useful in the development of bioelectronic devices and its application in real samples.

  4. Ensembles of nanoelectrodes modified with gold nanoparticles: characterization and application to DNA-hybridization detection.

    PubMed

    Silvestrini, Morena; Ugo, Paolo

    2013-01-01

    A new method to increase the active area (A(act)) of nanoelectrode ensembles (NEEs) is described. To this aim, gold nanoparticles (AuNPs) are immobilized onto the surface of NEEs using cysteamine as a cross-linker able to bind the AuNPs to the heads of the nanoelectrodes to obtain the so-called AuNPs-NEEs. The analysis of the cyclic voltammograms recorded in pure supporting electrolyte showed that the presence of the nanoparticles reflects in an, approximately, ten-times increase in the electrochemically active area of the ensemble. The measurement of the amount of electroactive polyoxometalates, which can be adsorbed on the gold surface of NEEs vs. AuNPs-NEEs, confirmed a significant increase of active area for the latter. These evidences indicate that there is a good electronic connection between the AuNPs and the underlying nanoelectrodes. The possibility to exploit AuNPs-NEEs for biosensing application was tested for the case of DNA-hybridization detection. After immobilization on the gold surface of AuNPs-NEEs of a thiolated single-stranded DNA, the hybridization with complementary sequences labeled with glucose oxidase (GOx) was performed. The detection of the hybridization was achieved by adding to the electrolyte solution the GOx substrate (i.e., glucose) and a suitable redox mediator, namely the (ferrocenylmethyl) trimethylammonium (FA(+)) cation; when the hybridization occurs, an electrocatalytic increase of the oxidation current of FA(+) is recorded. Comparison of electrocatalytic current recorded at DNA modified NEEs and AuNPs-NEEs indicate, for the latter, a significant increase in sensitivity in the detection of the DNA-hybridization event.

  5. Application of a gold electrode, modified by a self-assembled monolayer of 2-mercaptodecylhydroquinone, to the electroanalysis of hemoglobin.

    PubMed

    Zhang, Jingdong; Seo, Kyoungja; Jeon, Il Cheol

    2003-02-01

    A gold electrode modified by a self-assembled monolayer of 2-mercaptodecylhydroquinone (H(2)Q(CH(2))(10)SH) was applied to investigate the electrochemical response of hemoglobin in aerated buffer solutions. Compared with a bare gold electrode, the monolayer of H(2)Q(CH(2))(10)SH could suppress the reduction wave of dissolved oxygen in the buffer while effectively promoting the rate of electron transfer between hemoglobin and the electrode. Thus, a convenient way for electroanalysis of hemoglobin in air was achieved at the H(2)Q(CH(2))(10)SH/Au electrode. A linear relationship existed between peak current and concentration of hemoglobin in the range 1 x 10(-7)-1 x 10(-6) mol L(-1).

  6. Preparation of electrode-immobilized, redox-modified oligonucleotides for electrochemical DNA and aptamer-based sensing.

    PubMed

    Xiao, Yi; Lai, Rebecca Y; Plaxco, Kevin W

    2007-01-01

    Recent years have seen the development of a number of reagentless, electrochemical sensors based on the target-induced folding or unfolding of electrode-bound oligonucleotides, with examples reported to date, including sensors for the detection of specific nucleic acids, proteins, small molecules and inorganic ions. These devices, which are often termed electrochemical DNA (E-DNA) and E-AB (electrochemical, aptamer-based) sensors, are comprised of an oligonucleotide probe modified with a redox reporter (in this protocol methylene blue) at one terminus and attached to a gold electrode via a thiol-gold bond at the other. Binding of an analyte to the oligonucleotide probe changes its structure and dynamics, which, in turn, influences the efficiency of electron transfer to the interrogating electrode. This class of sensors perform well even when challenged directly with blood serum, soil and other complex, multicomponent sample matrices. This protocol describes the fabrication of E-DNA and E-AB sensors. The protocol can be completed in 12 h.

  7. Amperometric immunosensor based on a protein A/deposited gold nanocrystals modified electrode for carbofuran detection.

    PubMed

    Sun, Xia; Zhu, Ying; Wang, Xiangyou

    2011-01-01

    In this paper, an amperometric immunosensor modified with protein A/deposited gold nanocrystals (DpAu) was developed for the ultrasensitive detection of carbofuran residues. First, DpAu were electrodeposited onto the Au electrode surface to absorb protein A (PA) and improve the electrode conductivity. Then PA was dropped onto the surface of DpAu film, used for binding antibody Fc fragments. Next, anti-carbofuran monoclonal antibody was immobilized on the PA modified electrode. Finally, bovine serum albumin (BSA) was employed to block the possible remaining active sites avoiding any nonspecific adsorption. The fabrication procedure of the immunosensor was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. With the excellent electroconductivity of DpAu and the PA's oriented immobilization of antibodies, a highly efficient immuno-reaction and detection sensitivity could be achieved. The influences of the electrodeposition time of DpAu, pH of the detection solution and incubation time on the current response of the fabricated immunosensor were investigated. Under optimized conditions, the current response was proportional to the concentration of carbofuran which ranged from 1 to 100 ng/mL and 100 ng/mL to 100 μg/mL. The detection limit was 0.1924 ng/mL. The proposed carbofuran immnuosensor exhibited high specificity, reproducibility, stability and regeneration performance, which may open a new door for ultrasensitive detection of carbofuran residues in vegetables and fruits.

  8. Real-Time Plasmonic Monitoring of Single Gold Amalgam Nanoalloy Electrochemical Formation and Stripping.

    PubMed

    Wang, Jun-Gang; Fossey, John S; Li, Meng; Xie, Tao; Long, Yi-Tao

    2016-03-01

    Direct electrodeposition of mercury onto gold nanorods on an ITO substrate, without reducing agents, is reported. The growth of single gold amalgam nanoalloy particles and subsequent stripping was monitored in real-time monitoring by plasmonic effects and single-nanoparticle dark-field spectroelectrochemistry techniques. Time-dependent scattering spectral information conferred insight into the growth and stripping mechanism of a single nanoalloy particle. Four critical stages were observed: First, rapid deposition of Hg atoms onto Au nanorods; second, slow diffusion of Hg atoms into Au nanorods; third, prompt stripping of Hg atoms from Au nanorods; fourth, moderate diffusion from the inner core of Au nanorods. Under high Hg(2+) concentrations, homogeneous spherical gold amalgam nanoalloys were obtained. These results demonstrate that the morphology and composition of individual gold amalgam nanoalloys can be precisely regulated electrochemically. Moreover, gold amalgam nanoalloys with intriguing optical properties, such as modulated plasmonic lifetimes and quality factor Q, could be obtained. This may offer opportunities to extend applications in photovoltaic energy conversion and chemical sensing. PMID:26942394

  9. Fractal gold modified electrode for ultrasensitive thrombin detection

    NASA Astrophysics Data System (ADS)

    Xu, Li-Ping; Wang, Shuqi; Dong, Haifeng; Liu, Guodong; Wen, Yongqiang; Wang, Shutao; Zhang, Xueji

    2012-05-01

    We report a label-free and ultrasensitive aptasensor based on a fractal gold modified (FracAu) electrode for thrombin detection with a femtomolar detection limit. The FracAu electrode was prepared by electrodeposition of hydrogen tetrachloroaurate (HAuCl4) onto a bare indium tin oxide (ITO) electrode surface. After this process the electrode was characterized by SEM. A thiol-modified aptamer against thrombin was immobilized on the FracAu electrode through a self-assembling process. Upon thrombin binding, the interfacial electron transfer of the FracAu electrode was perturbed by the formation of an aptamer-thrombin complex. The concentration of thrombin in the sample solution was determined by measuring the change in the oxidation peak current of hydroxymethyl ferrocene (C11H12FeO) with differential pulse voltammetry (DPV). The current response (reduced peak current) had a linear relationship with the logarithm of thrombin concentrations in the range of 10-15 to 10-10 M with a detection limit of 5.7 fM. Furthermore, the as-prepared FracAu electrode exhibited high selectivity. The application of FracAu electrodes may be extended to prepare other types of biosensors, such as immunosensors, enzyme biosensors and DNA biosensors. These results show that FracAu electrodes have great promise for clinical diagnosis of disease-related biomarkers.We report a label-free and ultrasensitive aptasensor based on a fractal gold modified (FracAu) electrode for thrombin detection with a femtomolar detection limit. The FracAu electrode was prepared by electrodeposition of hydrogen tetrachloroaurate (HAuCl4) onto a bare indium tin oxide (ITO) electrode surface. After this process the electrode was characterized by SEM. A thiol-modified aptamer against thrombin was immobilized on the FracAu electrode through a self-assembling process. Upon thrombin binding, the interfacial electron transfer of the FracAu electrode was perturbed by the formation of an aptamer-thrombin complex. The

  10. Copper recovery and gold enrichment from waste printed circuit boards by mediated electrochemical oxidation.

    PubMed

    Fogarasi, Szabolcs; Imre-Lucaci, Florica; Imre-Lucaci, Arpád; Ilea, Petru

    2014-05-30

    The present study aims to develop an eco-friendly chemical-electrochemical process for the simultaneous recovery of copper and separation of a gold rich residue from waste printed circuit boards (WPCBs). The process was carried out by employing two different types of reactors coupled in series: a leaching reactor with a perforated rotating drum, for the dissolution of base metals and a divided electrochemical reactor for the regeneration of the leaching solution with the parallel electrowinning of copper. The process performances were evaluated on the basis of the dissolution efficiency, current efficiency and specific energy consumptions. Finally a process scale up was realized taking into consideration the optimal values of the operating parameters. The laboratory scale leaching plant allowed the recovery of a high purity copper deposit (99.04wt.%) at a current efficiency of 63.84% and specific energy consumption of 1.75kWh/kg cooper. The gold concentration in the remained solid residue was 25 times higher than the gold concentration in the initial WPCB samples. PMID:24747374

  11. Copper recovery and gold enrichment from waste printed circuit boards by mediated electrochemical oxidation.

    PubMed

    Fogarasi, Szabolcs; Imre-Lucaci, Florica; Imre-Lucaci, Arpád; Ilea, Petru

    2014-05-30

    The present study aims to develop an eco-friendly chemical-electrochemical process for the simultaneous recovery of copper and separation of a gold rich residue from waste printed circuit boards (WPCBs). The process was carried out by employing two different types of reactors coupled in series: a leaching reactor with a perforated rotating drum, for the dissolution of base metals and a divided electrochemical reactor for the regeneration of the leaching solution with the parallel electrowinning of copper. The process performances were evaluated on the basis of the dissolution efficiency, current efficiency and specific energy consumptions. Finally a process scale up was realized taking into consideration the optimal values of the operating parameters. The laboratory scale leaching plant allowed the recovery of a high purity copper deposit (99.04wt.%) at a current efficiency of 63.84% and specific energy consumption of 1.75kWh/kg cooper. The gold concentration in the remained solid residue was 25 times higher than the gold concentration in the initial WPCB samples.

  12. Highly sensitive electrochemical lead ion sensor harnessing peptide probe molecules on porous gold electrodes.

    PubMed

    Su, Wenqiong; Cho, Misuk; Nam, Jae-Do; Choe, Woo-Seok; Lee, Youngkwan

    2013-10-15

    Lead ion is one of the most hazardous and ubiquitous heavy metal pollutants and poses an increasing threat to the environment and human health. This necessitates rapid and selective detection and/or removal of lead ions from various soil and water resources. Recently, we identified several Pb²⁺ binding peptides via phage display technique coupled with chromatographic biopanning (Nian et al., 2010) where a heptapeptide (TNTLSNN) capable of recognizing Pb²⁺ with high affinity and specificity evolved. In the present study, an electrochemical sensor harnessing this Pb²⁺ affinity peptide as a probe on a porous gold electrode was developed. The three dimensional porous gold electrode was obtained from electrochemical deposition using the dynamic hydrogen bubble template method. A thin layer of poly(thiophene acetic acid) (PTAA) was coated on the porous gold surface. The Pb²⁺ recognizing peptide was immobilized via amide linkage on the PTAA. The developed biosensor was demonstrated to be fast, selective and reproducible in Pb²⁺ etection, exhibiting Pb²⁺-specific peak current values around -0.15 V in a broad concentration range (1-1×10⁷ nM) in 10 min despite the repeated use after regeneration.

  13. Highly sensitive electrochemical lead ion sensor harnessing peptide probe molecules on porous gold electrodes.

    PubMed

    Su, Wenqiong; Cho, Misuk; Nam, Jae-Do; Choe, Woo-Seok; Lee, Youngkwan

    2013-10-15

    Lead ion is one of the most hazardous and ubiquitous heavy metal pollutants and poses an increasing threat to the environment and human health. This necessitates rapid and selective detection and/or removal of lead ions from various soil and water resources. Recently, we identified several Pb²⁺ binding peptides via phage display technique coupled with chromatographic biopanning (Nian et al., 2010) where a heptapeptide (TNTLSNN) capable of recognizing Pb²⁺ with high affinity and specificity evolved. In the present study, an electrochemical sensor harnessing this Pb²⁺ affinity peptide as a probe on a porous gold electrode was developed. The three dimensional porous gold electrode was obtained from electrochemical deposition using the dynamic hydrogen bubble template method. A thin layer of poly(thiophene acetic acid) (PTAA) was coated on the porous gold surface. The Pb²⁺ recognizing peptide was immobilized via amide linkage on the PTAA. The developed biosensor was demonstrated to be fast, selective and reproducible in Pb²⁺ etection, exhibiting Pb²⁺-specific peak current values around -0.15 V in a broad concentration range (1-1×10⁷ nM) in 10 min despite the repeated use after regeneration. PMID:23707872

  14. Photoluminescence decay rate of silicon nanoparticles modified with gold nanoislands

    NASA Astrophysics Data System (ADS)

    Dan'ko, Viktor; Michailovska, Katerina; Indutnyi, Ivan; Shepeliavyi, Petro

    2014-04-01

    We investigated plasmon-assisted enhancement of emission from silicon nanoparticles (ncs-Si) embedded into porous SiO x matrix in the 500- to 820-nm wavelength range. In the presence in the near-surface region of gold nanoisland film, ncs-Si exhibited up to twofold luminescence enhancement at emission frequencies that correspond to the plasmon resonance frequency of Au nanoparticles. Enhancement of the photoluminescence (PL) intensity was attributed to coupling with the localized surface plasmons (LSPs) excited in Au nanoparticles and to increase in the radiative decay rate of ncs-Si . It has been shown that spontaneous emission decay rate of ncs-Si modified by thin Au film over the wide emission spectral range was accelerated. The emission decay rate distribution was determined by fitting the experimental decay curves to the stretched exponential model. The observed increase of the PL decay rate distribution width for the Au-coated nc-Si-SiO x sample in comparison with the uncoated one was explained by fluctuations in the surface-plasmon excitation rate .

  15. Biogenic Preparation of Gold Nanostructures Reduced from Piper longum Leaf Broth and Their Electrochemical Studies.

    PubMed

    Mallikarjuna, K; Narasimha, G; John Sushma, N; Dillip, G R; Subba Reddy, B V; Sreedhar, B; Deva Prasad Raju, B

    2015-02-01

    Exploitation of green chemical procedures for the synthesis of metal nanoparticles by biological process has received great attention in the field of nanotechnology. To demonstrate a biogenic method that involves the reduction of aqueous gold ions by the extract of Piper longum leaves leading to the formation of different morphological gold nanoparticles (AuNPs). The formation of gold nano-structures has been characterized by UV-Vis absorption spectroscopy. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns indicates the AuNPs are highly crystalline nature with the face-centered cubic (111), (200), (220) and (311) facets, respectively. The AuNPs have different sizes and morphologies that are identified by TEM studies. The involvement of water soluble bio-molecules such as carboxylic acids, flavonoids, proteins and terpenoids were identified by Fourier transform infrared (FT-IR) and Raman spectrum. The responsible mechanism of improving acidic nature and the process of encapsulation of gold nanoparticles by Piper longum extract was discussed. Additionally, we have demonstrated the modified carbon paste electrode using gold nanoparticles by means of cyclic voltammetry in a solution of 1 M KCI and 1 mM [Fe(CN)6]3-/4-. The analysis of cyclic voltammetry shows electronic transmission rate between modified Au-CPE and Bare-CPE electrode increased. PMID:26353644

  16. Gold nanoparticles embedded in organic/inorganic hybrid matrix: electrical and electrochemical behavior (withdrawal notice)

    NASA Astrophysics Data System (ADS)

    Moreira, Sandra D. F. C.; Silva, J. P. B.; Silva, Carlos J. R.; Capan, I.; Gomes, M. J. M.; Costa, Manuel F. M.

    2013-05-01

    Gold nanoparticles (AuNPs) with different diameters, from 3 to 32 nm, were immobilized in amine-alcohol-silicate matrix by mixing a preformed nanoparticle colloid with the precursors of amine-alcohol-silicate (AAs) prior to the solgel transition. These nanocomposites show high optical quality and optical features dictated by the size of the nanoparticle dopants but also present a high degree of flexibility which can largely enhance the range of practical applications. The current-voltage, impedance and capacitance-voltage characteristics of these materials have been measured. The electrochemical and impedimetric results reveal that AuNPs with different sizes give different signals, thus providing useful information that allows the employment of AuNPs in electrochemical biosensors. Capacitance- voltage measurements showed that these composites embedded AuNPs exhibited a large hysteresis window of 2.4V which indicates the possibility of charge storage in the Au nanoparticles embedded AAs hybrids.

  17. Electrochemical preparation and characterization of polypyrrole/stainless steel electrodes decorated with gold nanoparticles.

    PubMed

    Gutiérrez Pineda, Eduart; Alcaide, Francisco; Rodríguez Presa, María J; Bolzán, Agustín E; Gervasi, Claudio A

    2015-02-01

    The electrosynthesis and characterization of polypyrrole(PPy)/stainless steel electrodes decorated with gold nanoparticles and the performance of the composite electrode for sensing applications is described. PPy films were grown in potassium perchlorate and sodium salicylate solutions under comparable electropolymerization conditions. Polymer films prepared in the presence of perchlorate ions exhibited worm-like structures, whereas columnar structures were obtained in salicylate-containing solutions. Voltammetric response of PPy films prepared in salicylate solutions was more reversible. PPy films were decorated with gold nanoparticles obtained by a double step potentiostatic electrodeposition routine that allowed fine control of deposit characteristics. Analysis of deposits was performed by means of SEM and confocal Raman spectroscopy. The electrocatalytic activity of the Au/PPy electrodes was assessed for the electro-oxidation of hydrazine and hydroxylamine. Results showed a successful optimization of the route of synthesis that rendered nanocomposite electrode materials with promising applications in electrochemical sensing.

  18. Electrochemical biosensor for Mycobacterium tuberculosis DNA detection based on gold nanotubes array electrode platform.

    PubMed

    Torati, Sri Ramulu; Reddy, Venu; Yoon, Seok Soo; Kim, CheolGi

    2016-04-15

    The template assisted electrochemical deposition technique was used for the synthesis of gold nanotubes array (AuNTsA). The morphological structure of the synthesized AuNTsA was observed by scanning electron microscopy and found that the individual nanotubes are around 1.5 μm in length with a diameter of 200 nm. Nanotubes are vertically aligned to the Au thick film, which is formed during the synthesis process of nanotubes. The electrochemical performance of the AuNTsA was compared with the bare Au electrode and found that AuNTsA has better electron transfer surface than bare Au electrode which is due to the high surface area. Hence, the AuNTsA was used as an electrode for the fabrication of DNA hybridization biosensor for detection of Mycobacterium Tuberculosis DNA. The DNA hybridization biosensor constructed by AuNTsA electrode was characterized by cyclic voltammetry technique with Fe(CN)6(3-/4-) as an electrochemical redox indicator. The selectivity of the fabricated biosensor was illustrated by hybridization with complementary DNA and non-complementary DNA with probe DNA immobilized AuNTsA electrode using methylene blue as a hybridization indicator. The developed electrochemical DNA biosensor shows good linear range of complementary DNA concentration from 0.01 ng/μL to 100 ng/μL with high detection limit.

  19. Liquid crystal and gold nanoparticles applied to electrochemical immunosensor for cardiac biomarker.

    PubMed

    Zapp, Eduardo; Westphal, Eduard; Gallardo, Hugo; de Souza, Bernardo; Cruz Vieira, Iolanda

    2014-09-15

    A label-free electrochemical immunosensor based on the ionic liquid crystal (E)-1-decyl-4-[(4-decyloxyphenyl)diazenyl]pyridinium bromide (Br-Py) coated on a glassy carbon electrode (GCE) for the quantitative detection of myoglobin (Mb), a cardiac marker for acute myocardial infarction, is reported herein for the first time. The monoclonal anti-myoglobin antibody (ab-Mb) was covalently immobilized using glyoxal on a film of polyethyleneimine-coated gold nanoparticles (AuNP-PEI). The proposed method for Mb detection is based on voltammetric suppression of the Br-Py signal when the immunosensor was incubated with Mb antigen. The electrochemical performance of the Mb immunosensor was studied by electrochemical impedance spectroscopy, and cyclic and square-wave voltammetry. Under the optimal conditions, the proposed immunosensor shows a good linear relationship between the electrochemical inhibition response and the concentration of Mb over the range of 9.96-72.8 ng mL(-1) with a detection limit of 6.29 ng mL(-1). The results obtained indicate that the proposed immunosensor provides good sensitivity and simple operation for detecting acute myocardial infarction with Mb as a biomarker. PMID:24721423

  20. Direct application of gold nanoparticles to one-pot electrochemical biosensors.

    PubMed

    Chen, Guifang; Tong, Hui; Gao, Tao; Chen, Yangyang; Li, Genxi

    2014-11-01

    Gold nanoparticles (AuNPs) have been widely employed for the fabrication of electrochemical biosensors. In most cases, AuNPs are immobilized on the surface of an electrode, so they are difficult to be regenerated, making the use of the biosensor unfriendly. In this work, by adopting AuNPs directly as the electrolytes, we have developed a novel AuNPs-based electrochemical detection system. In brief, AuNPs-catalyzed oxidation of glucose is combined with a HRP-catalyzed reaction as well as an electrocatalytic reaction to compose cascade reactions in the electrolyte. Thus, the intensity of the electrocatalytic signals has quantitative relation with the concentration of glucose, and favors the sensitive detection of glucose. Furthermore, because the catalysis of AuNPs may be blocked under the interaction with single-stranded DNA and unblocked in the presence of a complementary sequence, detection of DNA and even single-nucleotide polymorphism can thereby been achieved. This one-pot detection system can be operated and regenerated very easily, since all the components are integrated in the electrolytes of AuNPs, and the unmodified electrode can be reused after being rinsed. This concept by integrating the advantages of sensitive electrochemical detection with the easy-to-operate nanocolloidal system may also promote the development of other kinds of electrochemical biosensors.

  1. Oligonucleotide-modified screen-printed gold electrodes for enzyme-amplified sensing of nucleic acids.

    PubMed

    Carpini, Guido; Lucarelli, Fausto; Marrazza, Giovanna; Mascini, Marco

    2004-09-15

    An electrochemical genosensor for the detection of specific sequences of DNA has been developed using disposable screen-printed gold electrodes. Screen-printed gold electrodes were firstly modified with a mixed monolayer of a 25-mer thiol-tethered DNA probe and a spacer thiol, 6-mercapto-1-hexanol (MCH). The DNA probe sequence was internal to the sequence of the 35S promoter, which sequence is inserted in the genome of GMOs regulating the transgene expression. An enzyme-amplified detection scheme, based on the coupling of a streptavidin-alkaline phosphatase conjugate and biotinylated target sequences was then applied. The enzyme catalysed the hydrolysis of the electroinactive alpha-naphthyl phosphate to alpha-naphthol; this product is electroactive and has been detected by means of differential pulse voltammetry. The assay was, firstly, characterised using synthetic oligonucleotides. Relevant parameters, such as the probe concentration and the immobilisation time, the use of the MCH and different enzymatic conjugates, were investigated and optimised. The genosensor response was found to be linearly related to the target concentration between 0 and 25 nmol/L; the detection limit was 0.25 nmol/L. The analytical procedure was then applied for the detection of the 35S promoter sequence, which was amplified from the pBI121 plasmid by polymerase chain reaction (PCR). Hybridisation conditions (i.e., hybridisation buffer and hybridisation time) were further optimised. The selectivity of the assay was confirmed using biotinylated non-complementary amplicons and PCR blanks. The results showed that the genosensor enabled sensitive (detection limit: 1 nmol/L) and specific detection of GMO-related sequences, thus providing a useful tool for the screening analysis of bioengineered food samples.

  2. Electrochemical biosensor for protein kinase A activity assay based on gold nanoparticles-carbon nanospheres, phos-tag-biotin and β-galactosidase.

    PubMed

    Zhou, Yunlei; Yin, Huanshun; Li, Xue; Li, Zhi; Ai, Shiyun; Lin, Hai

    2016-12-15

    A sensitive and selective electrochemical biosensor was fabricated for protein kinase A (PKA) activity assay. Multiple signal amplification techniques were employed including the nanocomposite of gold nanoparticles and carbon nanospheres (Au@C), the biocomposite of SiO2 and streptavidin (SiO2-SA), the composite of AuNPs and biotinylated β-galactosidase (AuNPs-B-Gal) and in situ enzymatic generation of electrochemical activity molecule of p-aminophenol. After peptides were assembled on Au@C modified electrode surface, they were phosphorylated by PKA in the presence of ATP. Then, biotinylated Phos-tag was modified on electrode surface through the specific interaction between Phos-tag and phosphate group. Finally, SiO2-SA and AuNPs-B-Gal were captured through the specific interaction between biotin and streptavidin. Because the electrochemical response of p-aminophenol was directly related to PKA concentration, an innovative electrochemical assay could be realized for PKA detection. The detection limit was 0.014unit/mL. The developed method showed high detection sensitivity and selectivity. In addition, the fabricated biosensor can be also applied to detect PKA in human normal gastricepithelial cell line and human gastric carcinoma cell line with satisfactory results.

  3. Flow injection catalase activity measurement based on gold nanoparticles/carbon nanotubes modified glassy carbon electrode.

    PubMed

    El Nashar, Rasha Mohamed

    2012-07-15

    Amperometric flow injection method of hydrogen peroxide analysis was developed based on catalase enzyme (CAT) immobilization on a glassy carbon electrode (GC) modified with electrochemically deposited gold nanoparticles on a multiwalled carbon nanotubes/chitosan film. The resulting biosensor was applied to detect hydrogen peroxide with a linear response range 1.0×10(-7)-2.5×10(-3)M with a correlation coefficient 0.998 and response time less than 10s. The optimum conditions of film deposition such as potential applied, deposition time and pH were tested and the flow injection conditions were optimized to be: flow rate of 3ml/min, sample volume 75μl and saline phosphate buffer of pH 6.89. Catalase enzyme activity was successfully determined in liver homogenate samples of rats, raised under controlled dietary plan, using a flow injection analysis system involving the developed biosensor simultaneously with spectrophotometric detection, which is the common method of enzymatic assay.

  4. Corrosion resistance of Ti modified by chitosan-gold nanoparticles for orthopedic implantation.

    PubMed

    Farghali, R A; Fekry, A M; Ahmed, Rasha A; Elhakim, H K A

    2015-08-01

    Highly uniform bionanocomposite film composed of chitosan (CS) and gold nanoparticles (AuNPs) was synthesized successfully by electrodeposition method. The influence of AuNPs/CS bionanocomposite film on corrosion resistance of Ti was investigated. Surface morphology and compositional properties of the bionanocomposite were analyzed by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). Moreover, cyclic voltammetry (CV), open-circuit potential measurements (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (Rp) were used to examine the corrosion behavior in Hanks' solution. In comparison with Ti, Nyquist and Bode plots displayed higher impedance values and phase angles for AuNPs/CS biocomposite denoting a more protective passive film on Ti with inhibition efficiency (IE%) of 98%. An electric equivalent circuit with three time constants was modeled for the bionanocomposite. In addition, the antibacterial effect revealed the high efficiencies of the bionanocomposite film for inhibiting bacterial growth. The combination of the high biocompatibility of chitosan and strong adsorption ability of AuNPs make AuNPs/CS bionanocomposite promising candidate for modifying biomaterial surfaces for medical implantation applications.

  5. Droplet-based glucosamine sensor using gold nanoparticles and polyaniline-modified electrode.

    PubMed

    Suea-Ngam, Akkapol; Rattanarat, Poomrat; Wongravee, Kanet; Chailapakul, Orawon; Srisa-Art, Monpichar

    2016-09-01

    A droplet-based electrochemical sensor for direct measurement of D-glucosamine was developed using carbon paste electrodes (CPEs) modified with gold nanoparticles (AuNPs) and polyaniline (PANI). Central composition design (CCD) was employed as a powerful method for optimization of parameters for electrode fabrication. The optimized amounts of AuNPs and PANI obtained from the response surface were determined as 300 and 3000mgL(-1), respectively. Coupled with a droplet microfluidic system, the analysis of glucosamine was performed in a high-throughput manner with a sample throughput of at least 60 samples h(-1). In addition, the adsorption of the analyte on the electrode surface was prevented due to compartmentalization in droplets. Linearity of the proposed system was found to be in the range of 0.5-5mM with a sensitivity of 7.42×10(-3)Amol(-1)Lcm(-2) and limits of detection and quantitation of 0.45 and 1.45mM, respectively. High intraday and interday (evaluated among 3 days) precisions for the detection of 50 droplets containing glucosamine were obtained with relative standard deviation less than 3%. The system was successfully used to determine the amounts of glucosamine in supplementary products with error percentage and relative standard deviation less than 3%. In addition, the amounts of glucosamine measured using the developed sensor were in good agreement with those obtained from a CE method. These indicate high accuracy and precision of the proposed system. PMID:27343587

  6. Flow injection catalase activity measurement based on gold nanoparticles/carbon nanotubes modified glassy carbon electrode.

    PubMed

    El Nashar, Rasha Mohamed

    2012-07-15

    Amperometric flow injection method of hydrogen peroxide analysis was developed based on catalase enzyme (CAT) immobilization on a glassy carbon electrode (GC) modified with electrochemically deposited gold nanoparticles on a multiwalled carbon nanotubes/chitosan film. The resulting biosensor was applied to detect hydrogen peroxide with a linear response range 1.0×10(-7)-2.5×10(-3)M with a correlation coefficient 0.998 and response time less than 10s. The optimum conditions of film deposition such as potential applied, deposition time and pH were tested and the flow injection conditions were optimized to be: flow rate of 3ml/min, sample volume 75μl and saline phosphate buffer of pH 6.89. Catalase enzyme activity was successfully determined in liver homogenate samples of rats, raised under controlled dietary plan, using a flow injection analysis system involving the developed biosensor simultaneously with spectrophotometric detection, which is the common method of enzymatic assay. PMID:22817944

  7. Kinetic Parameter Extraction of Square Wave Voltammograms from DNA-Modified Gold Electrodes

    NASA Astrophysics Data System (ADS)

    McWilliams, Marc; Wohlgamuth, Chris; Slinker, Jason

    2012-10-01

    The field of surface bound electrochemistry is important in a variety of applications specifically sensing. A fundamental understanding of the processes involved could help to improve detection limits, optimize rates of detection and direct changes in device design. Accurate extraction of electrochemical kinetic parameters such as the rate constant k and charge transfer coefficient α from cyclic voltammograms can be challenging when confronted with large background currents and relatively weak signals. The commonly used technique of Laviron analysis is both time consuming and somewhat subjective. Square wave voltammetry (SWV) is therefore an ideal alternative method given that it maximizes signal while minimizing capacitive effects. In this experiment kinetic parameters of DNA-modified gold electrodes are obtained from SWV curves through background subtraction followed by nonlinear least squares fitting using a first order quasi-reversible surface process model. The fitting is accomplished using the Nelder-Mead simplex algorithm with standard parameters and a convergence condition of less than 0.0001%. General agreement with experimental data is shown with varying levels of confidence. Difficulties specific to this experiment are discussed as well as the possible benefits of utilizing the Bayesian statistical approach of nested sampling when confronted with multiple peaks of interest and the background source is well defined.

  8. Study of the scale formation mechanism on gold modified with an alkanethiol monolayer.

    PubMed

    Clément, Maxime; St-Jean, Émilie; Bouchard, Nicolas-Alexandre; Ménard, Hugues

    2013-02-01

    Scaling is a problem in many industrial processes. To control and minimize it, it is important to understand the dynamics of the scale formation. In this paper, the scale formation was examined on two kinds of gold surfaces. One was a pure metallic gold surface, and the other was a gold surface modified with an alkanethiol self-assembled monolayer. A series of surface characterization experiments were performed to ensure a good understanding of the gold-thiol bond stability in a caustic solution.

  9. Sensitive Adsorptive Voltammetric Method for Determination of Bisphenol A by Gold Nanoparticle/Polyvinylpyrrolidone-Modified Pencil Graphite Electrode

    PubMed Central

    Yaman, Yesim Tugce; Abaci, Serdar

    2016-01-01

    A novel electrochemical sensor gold nanoparticle (AuNP)/polyvinylpyrrolidone (PVP) modified pencil graphite electrode (PGE) was developed for the ultrasensitive determination of Bisphenol A (BPA). The gold nanoparticles were electrodeposited by constant potential electrolysis and PVP was attached by passive adsorption onto the electrode surface. The electrode surfaces were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The parameters that affected the experimental conditions were researched and optimized. The AuNP/PVP/PGE sensor provided high sensitivity and selectivity for BPA recognition by using square wave adsorptive stripping voltammetry (SWAdSV). Under optimized conditions, the detection limit was found to be 1.0 nM. This new sensor system offered the advantages of simple fabrication which aided the expeditious replication, low cost, fast response, high sensitivity and low background current for BPA. This new sensor system was successfully tested for the detection of the amount of BPA in bottled drinking water with high reliability. PMID:27231912

  10. Sensitive Adsorptive Voltammetric Method for Determination of Bisphenol A by Gold Nanoparticle/Polyvinylpyrrolidone-Modified Pencil Graphite Electrode.

    PubMed

    Yaman, Yesim Tugce; Abaci, Serdar

    2016-01-01

    A novel electrochemical sensor gold nanoparticle (AuNP)/polyvinylpyrrolidone (PVP) modified pencil graphite electrode (PGE) was developed for the ultrasensitive determination of Bisphenol A (BPA). The gold nanoparticles were electrodeposited by constant potential electrolysis and PVP was attached by passive adsorption onto the electrode surface. The electrode surfaces were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The parameters that affected the experimental conditions were researched and optimized. The AuNP/PVP/PGE sensor provided high sensitivity and selectivity for BPA recognition by using square wave adsorptive stripping voltammetry (SWAdSV). Under optimized conditions, the detection limit was found to be 1.0 nM. This new sensor system offered the advantages of simple fabrication which aided the expeditious replication, low cost, fast response, high sensitivity and low background current for BPA. This new sensor system was successfully tested for the detection of the amount of BPA in bottled drinking water with high reliability. PMID:27231912

  11. Preparation of gold tips suitable for tip-enhanced Raman spectroscopy and light emission by electrochemical etching

    NASA Astrophysics Data System (ADS)

    Ren, Bin; Picardi, Gennaro; Pettinger, Bruno

    2004-04-01

    We describe a method of preparing gold scanning tunneling microscopy (STM) tips by direct current electrochemical etching in concentrated HCl and ethanol solution. Gold tips with tip apex radius lower than 30 nm can be reproducibly prepared by this method. The influence of the solution composition, etching voltage on the surface structure, and sharpness has been investigated. These tips can be efficiently used for STM imaging, tip-enhanced Raman spectroscopy, and light emission investigations on the same sample.

  12. Electrochemical investigations of 3-(3-thienyl) acrylic acid protected nanoclusters and planar gold surfaces.

    PubMed

    Nirmal, R G; Kavitha, A L; Berchmans, Sheela; Yegnaraman, V

    2007-06-01

    Formation of self assembled monolayers on gold surface by thiols and disulphides is a well known phenomenon and extensive research work has been carried out in this area with envisaged applications in the area of sensors, molecular electronics, lithography, device fabrication using bottom-up approach, etc. Recently, it has been established that thiophene molecules can self assemble on gold surface due to Au-S interactions. 3-(3-thienyl) acrylic acid, a bifunctional ligand is used in this work to form self-assembled monolayers on planar gold surfaces (two dimensional assemblies) and to prepare monolayer protected gold nano clusters (three-dimensional assemblies). The electron transfer blocking properties of the two-dimensional monolayers were evaluated by using standard redox probes like ferrocyanide anions and Ruthenium hexamine cations. The functionalisation of the two-dimensional and three-dimensional assemblies has been carried out with ferrocene carboxylic acid and the functionalised monolayers were characterized by Cyclic voltammetry. The formation of thienyl acrylic acid protected nanoclusters has been verified by TEM and surface plasmon resonance absorption. It has been observed that when thiophene based ligands are used as stabilizers for the formation of metal nanoparticles, they tend to aggregate as a result of pi-pi interactions between adjacent thiophene ligands. In this case it is found that aggregation is prevented. The substituent at the thiophene ring hinders pi-pi interactions. The quantised nature of electrochemical charging of these nanoparticles has been demonstrated by differential pulse voltammetry (DPV), which exhibit peak like features (coulomb's staircase). This work also explores the possibility of using 3-(3-thienyl) acrylic acid as building blocks or spacers on planar and colloidal gold surfaces for potential applications in the field of sensors and devices.

  13. Nanoporous gold supported cobalt oxide microelectrodes as high-performance electrochemical biosensors.

    PubMed

    Lang, Xing-You; Fu, Hong-Ying; Hou, Chao; Han, Gao-Feng; Yang, Ping; Liu, Yong-Bing; Jiang, Qing

    2013-01-01

    Tremendous demands for electrochemical biosensors with high sensitivity and reliability, fast response and excellent selectivity have stimulated intensive research on developing versatile materials with ultrahigh electrocatalytic activity. Here we report flexible and self-supported microelectrodes with a seamless solid/nanoporous gold/cobalt oxide hybrid structure for electrochemical nonenzymatic glucose biosensors. As a result of synergistic electrocatalytic activity of the gold skeleton and cobalt oxide nanoparticles towards glucose oxidation, amperometric glucose biosensors based on the hybrid microelectrodes exhibit multi-linear detection ranges with ultrahigh sensitivities at a low potential of 0.26 V (versus Ag/AgCl). The sensitivity up to 12.5 mA mM⁻¹ cm⁻² with a short response time of less than 1 s gives rise to ultralow detection limit of 5 nM. The outstanding performance originates from a novel nanoarchitecture in which the cobalt oxide nanoparticles are incorporated into pore channels of the seamless solid/nanoporous Au microwires, providing excellent electronic/ionic conductivity and mass transport for the enhanced electrocatalysis.

  14. Selective detection of endotoxin using an impedance aptasensor with electrochemically deposited gold nanoparticles.

    PubMed

    Su, Wenqiong; Kim, Sung-Eun; Cho, MiSuk; Nam, Jae-Do; Choe, Woo-Seok; Lee, Youngkwan

    2013-01-01

    Using a single-stranded DNA (ssDNA) aptamer exhibiting high binding affinity (Kd = 12 nM) to endotoxin as a probe, an impedance sensor where aptamer-conjugated gold nanoparticles (AuNPs) were electrochemically deposited on a gold electrode was fabricated and its performance in regard to endotoxin detection assessed. AuNPs have been employed widely as biosensors because of their unique physical and chemical properties. In order to maximize the performance of the impedance aptasensor on endotoxin detection, some critical factors affecting aptamer conjugation to AuNPs and target recognition ability (i.e. concentrations of aptamer coupled with AuNPs, pH, ion strength and cation effect at the time of aptamer-endotoxin interaction) were optimized. Electrochemical impendence spectroscopy, cyclic voltametry, atomic force microscope, scanning electron microscope and quartz crystal microbalance were employed to characterize all the modification/detection procedures during the sensor fabrication. The developed aptasensor showed a broad linear dynamic detection range (0.01-10.24 ng/ml) with a very low detection limit for endotoxin (0.005 ng/ml), despite the presence of several biomolecules (e.g. plasmid DNA, RNA, serum albumin, Glc and sucrose) known to interfere with other endotoxin assays. The demonstrated aptasensor required a detection time of only 10 min, providing a simple and fast analytical method to specifically detect endotoxin from complex biological liqors.

  15. Selective detection of endotoxin using an impedance aptasensor with electrochemically deposited gold nanoparticles.

    PubMed

    Su, Wenqiong; Kim, Sung-Eun; Cho, MiSuk; Nam, Jae-Do; Choe, Woo-Seok; Lee, Youngkwan

    2013-01-01

    Using a single-stranded DNA (ssDNA) aptamer exhibiting high binding affinity (Kd = 12 nM) to endotoxin as a probe, an impedance sensor where aptamer-conjugated gold nanoparticles (AuNPs) were electrochemically deposited on a gold electrode was fabricated and its performance in regard to endotoxin detection assessed. AuNPs have been employed widely as biosensors because of their unique physical and chemical properties. In order to maximize the performance of the impedance aptasensor on endotoxin detection, some critical factors affecting aptamer conjugation to AuNPs and target recognition ability (i.e. concentrations of aptamer coupled with AuNPs, pH, ion strength and cation effect at the time of aptamer-endotoxin interaction) were optimized. Electrochemical impendence spectroscopy, cyclic voltametry, atomic force microscope, scanning electron microscope and quartz crystal microbalance were employed to characterize all the modification/detection procedures during the sensor fabrication. The developed aptasensor showed a broad linear dynamic detection range (0.01-10.24 ng/ml) with a very low detection limit for endotoxin (0.005 ng/ml), despite the presence of several biomolecules (e.g. plasmid DNA, RNA, serum albumin, Glc and sucrose) known to interfere with other endotoxin assays. The demonstrated aptasensor required a detection time of only 10 min, providing a simple and fast analytical method to specifically detect endotoxin from complex biological liqors. PMID:23165992

  16. Electrochemical studies of capping agent adsorption provide insight into the formation of anisotropic gold nanocrystals.

    PubMed

    Danger, Brook R; Fan, Donna; Vivek, J P; Burgess, Ian J

    2012-12-21

    The ability of the 4-dimethylaminopyridine (DMAP) to stabilize and control the formation of anisotropic gold nanocrystals produced via the borohydride reduction of gold(III) salts is reported here. Electrochemical measurements of DMAP electrosorption on different low-index single crystal and polycrystalline electrodes is provided and shows a propensity for DMAP to preferentially adsorb on {100} facets. Measuring the electrochemical potential during nanocrystal formation shows that experimental conditions can easily be manipulated so that the growth of nanoseeds occurs at potentials that support preferential DMAP adsorption on {100} surfaces giving rise to highly anisotropic nanocrystals (nanorods, bipyramids, and nanopods). Nanopods with nearly 50 nm arm lengths are shown to form and produce a surface plasmon mode that extends well into the near IR (λ(max) ≈ 1350 nm). Evidence is provided of the slow, partial reduction of tetrachloroaurate to a DMAP stabilized Au(I) species. Shape control is achieved simply by varying the length of time, τ, that DMAP is allowed to partially reduce the Au(III) ions prior to the addition of the strong reducing agent, NaBH(4). Thus the role of DMAP in producing anisotropic particle shapes is shown to be multifunctional. A mechanism accounting for the dependence of particle shape on τ is provided. PMID:23186041

  17. Rapid detection and quantification of free hemoglobin and haptoglobin by nanogold modified electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Yu-Ning; Li, Hsing-Yuan; Chu, Hsueh-Liang; Cheng, Tsia-Mu; Tseng, Shin-Hua; Chang, Chia-Ching

    2013-03-01

    Free Hemoglobin (Hb) is a metabolic substance that damage tissue and vessel. It is released from destructed red blood cell and causes infection or inflammatory of human body. In blood plasma, haptoglobin (Hp) binds free Hb with high affinity and prevents the damage which is caused by cell free Hb. Hp has three phenotypes, that are Hp1-1, Hp 2-1, and Hp 2-2. Different phenotypes of Hp has been different affinities to Hb. It is known that electrochemical impedance spectroscopy (EIS) provide more information for detecting the small amount bio-molecules, include protein and DNA. In this study, we have developed a simple, fast, reliable and sensitive platform to quantify concentration of free Hb and Hp. In this platform, detection probe has been modified with nano gold and the surface charge transfer resistance of Hb and Hp binding could be detected and quantified within 18 min. This is a whole new platform to quantify free Hb in the serum of human to our knowledge.

  18. A simple assay to amplify the electrochemical signal by the aptamer based biosensor modified with CdS hollow nanospheres.

    PubMed

    Li, Yanfen; Bao, Jianchun; Han, Min; Dai, Zhihui; Wang, Huaisheng

    2011-04-15

    A simple method to amplify the electrochemical signal by an aptamer with 22 bases modified with CdS hollow nanospheres (CdSHNs) was described. Using the thrombin as a model, the interaction between the aptamer and CdSHNs was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and circular dichroism spectroscopy. CdSHNs promoted the electron transfer between the gold electrode and K(3)[Fe(CN)(6)] and facilitated the conformation conversion of the aptamer from hairpin to G-quadruplex after the aptamer interacted with thrombin. Under optimal conditions, the modified electrode could be used for the determination of thrombin from 0 to 33 μg mL(-1) and the sensitivity was 1.34 μA mL μg(-1)cm(-2), while the linear range of the modified electrode without the immobilization of CdSHNs was from 2.75 to 27.5 μg mL(-1) and the sensitivity was 0.062 μA mL μg(-1)cm(-2). This constructed biosensor also had a good stability, specificity, reproducibility and accuracy which could provide a promising platform for fabrication of aptamer based biosensors.

  19. Direct electrochemical detection of kanamycin based on peroxidase-like activity of gold nanoparticles.

    PubMed

    Wang, Chunshuai; Liu, Chang; Luo, Jibao; Tian, Yaping; Zhou, Nandi

    2016-09-14

    An enzyme-free, ultrasensitive electrochemical detection of kanamycin residue was achieved based on mimetic peroxidase activity of gold nanoparticles (AuNPs) and target-induced replacement of the aptamer. AuNPs which were synthesized using tyrosine as a reducing and capping agent, exhibited mimetic peroxidase activity. In the presence of kanamycin-specific aptamer, however, the single-stranded DNA (ssDNA) adsorbed on the surface of AuNPs via the interaction between the bases of ssDNA and AuNPs, and therefore blocked the catalytic site of AuNPs, and inhibited their peroxidase activity. While in the presence of target kanamycin, it bound with the adsorbed aptamer on AuNPs with high affinity, exposed the surface of AuNPs and recovered the peroxidase activity. Then AuNPs catalyzed the reaction between H2O2 and reduced thionine to produce oxidized thionine. The latter exhibited a distinct reduction peak on gold electrode in differential pulse voltammetry (DPV), and could be utilized to quantify the concentration of kanamycin. Under the optimized conditions, the proposed electrochemical assay showed an extremely high sensitivity towards kanamycin, with a linear relationship between the peak current and the concentration of kanamycin in the range of 0.1-60 nM, and a detection limit of 0.06 nM. Moreover, the established approach was successfully applied in the detection of kanamycin in honey samples. Therefore, the proposed electrochemical assay has great potential in the fields of food quality control and environmental monitoring. PMID:27566341

  20. Molecularly imprinted polymer decorated nanoporous gold for highly selective and sensitive electrochemical sensors

    PubMed Central

    Li, Yingchun; Liu, Yuan; Liu, Jie; Liu, Jiang; Tang, Hui; Cao, Cong; Zhao, Dongsheng; Ding, Yi

    2015-01-01

    Electrochemical nanosensors based on nanoporous gold leaf (NPGL) and molecularly imprinted polymer (MIP) are developed for pharmaceutical analysis by using metronidazole (MNZ) as a model analyte. NPGL, serving as the loading platform for MIP immobilization, possesses large accessible surface area with superb electric conductivity, while electrochemically synthesized MIP thin layer affords selectivity for specific recognition of MNZ molecules. For MNZ determination, the hybrid electrode shows two dynamic linear range of 5 × 10−11 to 1 × 10−9 mol L−1 and 1 × 10−9 to 1.4 × 10−6 mol L−1 with a remarkably low detection limit of 1.8 × 10−11 mol L−1 (S/N = 3). In addition, the sensor exhibits high binding affinity and selectivity towards MNZ with excellent reproducibility and stability. Finally, the reliability of MIP-NPGL for MNZ detection is proved in real fish tissue samples, demonstrating the potential for the proposed electrochemical sensors in monitoring drug and biological samples. PMID:25572290

  1. Electrochemical preparation of silver and gold nanoparticles: Characterization by confocal and surface enhanced Raman microscopy

    NASA Astrophysics Data System (ADS)

    Plieth, W.; Dietz, H.; Anders, A.; Sandmann, G.; Meixner, A.; Weber, M.; Kneppe, H.

    2005-12-01

    Localized silver and gold nanoparticles, electrochemically prepared by means of the double-pulse technique, were investigated with respect to their optical and spectroscopic properties by scanning confocal microscopy combined with surface enhanced Raman spectroscopy (SERS) and subsequent comparison with the local image of scanning electron microscopy (SEM). Analogous to the silver cluster preparation technique, controlled electrodeposition of gold nanoparticles was demonstrated, varying size from 10 to 500 nm and particle density. The maximum SERS enhancement factors found in the measurements were: (i) 10 10 for silver particles and (ii) 10 8 for gold particles. The optical and spectroscopic data of the local nanoparticle structures investigated showed that SERS is a local phenomenon, because (i) only few particles are Raman active particles, (ii) strongest enhancements in SERS are obtained from particle agglomerates, (iii) typically the Raman radiation is emitted from irregular structures like the necks between two or more particles agglomerated. In the investigated range from 10 to 500 nm no significant influence of the particle size was observed.

  2. Electrochemical oxygen reduction behavior of selectively deposited platinum atoms on gold nanoparticles.

    PubMed

    Sarkar, A; Kerr, J B; Cairns, E J

    2013-07-22

    Carbon-supported Pt@Au "core-shell" nanoparticles with varying surface concentration of platinum atoms have been synthesized using a novel redox-mediated synthesis approach. The synthesis technique allows for a selective deposition of platinum atoms on the surface of prefabricated gold nanoparticles. Energy dispersive spectroscopic analyses in a scanning electron microscope reveal that the platinum to gold atomic ratios are close to the nominal values, validating the synthesis scheme. X-ray diffraction data indicate an un-alloyed structure. The platinum to gold surface atomic ratio determined from cyclic voltammetry and copper under-potential deposition experiments reveal good agreement with the calculated values at low platinum concentration. However, there is an increase in non-uniformity in the deposition process upon increasing the platinum concentration. Koutecky-Levich analysis of the samples indicates a transition of the total number of electrons transferred (n) in the electrochemical oxygen reduction reaction from two to four electrons upon increasing the surface concentration of platinum atoms. Furthermore, the data indicate that isolated platinum atoms can reduce molecular oxygen but via a two-electron route. Moreover, successful four-electron reduction of molecular oxygen requires clusters of platinum atoms.

  3. Investigation of Hemoglobin/Gold Nanoparticle Heterolayer on Micro-Gap for Electrochemical Biosensor Application

    PubMed Central

    Lee, Taek; Kim, Tae-Hyung; Yoon, Jinho; Chung, Yong-Ho; Lee, Ji Young; Choi, Jeong-Woo

    2016-01-01

    In the present study, we fabricated a hemoglobin/gold nanoparticle (Hb/GNP) heterolayer immobilized on the Au micro-gap to confirm H2O2 detection with a signal-enhancement effect. The hemoglobin which contained the heme group catalyzed the reduction of H2O2. To facilitate the electron transfer between hemoglobin and Au micro-gap electrode, a gold nanoparticle was introduced. The Au micro-gap electrode that has gap size of 5 µm was fabricated by conventional photolithographic technique to locate working and counter electrodes oppositely in a single chip for the signal sensitivity and reliability. The hemoglobin was self-assembled onto the Au surface via chemical linker 6-mercaptohexanoic acid (6-MHA). Then, the gold nanoparticles were adsorbed onto hemoglobin/6-MHA heterolayers by the layer-by-layer (LbL) method. The fabrication of the Hb/GNP heterolayer was confirmed by atomic force microscopy (AFM) and surface-enhanced Raman spectroscopy (SERS). The redox property and H2O2 detection of Hb/GNP on the micro-gap electrode was investigated by a cyclic voltammetry (CV) experiment. Taken together, the present results show that the electrochemical signal-enhancement effect of a hemoglobin/nanoparticle heterolayer was well confirmed on the micro-scale electrode for biosensor applications. PMID:27171089

  4. Square Wave Voltammetry of TNT at Gold Electrodes Modified with Self-Assembled Monolayers Containing Aromatic Structures

    PubMed Central

    Trammell, Scott A.; Zabetakis, Dan; Moore, Martin; Verbarg, Jasenka; Stenger, David A.

    2014-01-01

    Square wave voltammetry for the reduction of 2,4,6-trinitrotoluene (TNT) was measured in 100 mM potassium phosphate buffer (pH 8) at gold electrodes modified with self-assembled monolayers (SAMs) containing either an alkane thiol or aromatic ring thiol structures. At 15 Hz, the electrochemical sensitivity (µA/ppm) was similar for all SAMs tested. However, at 60 Hz, the SAMs containing aromatic structures had a greater sensitivity than the alkane thiol SAM. In fact, the alkane thiol SAM had a decrease in sensitivity at the higher frequency. When comparing the electrochemical response between simulations and experimental data, a general trend was observed in which most of the SAMs had similar heterogeneous rate constants within experimental error for the reduction of TNT. This most likely describes a rate limiting step for the reduction of TNT. However, in the case of the alkane SAM at higher frequency, the decrease in sensitivity suggests that the rate limiting step in this case may be electron tunneling through the SAM. Our results show that SAMs containing aromatic rings increased the sensitivity for the reduction of TNT when higher frequencies were employed and at the same time suppressed the electrochemical reduction of dissolved oxygen. PMID:25549081

  5. Electrocatalytic oxidation of phytohormone salicylic acid at copper nanoparticles-modified gold electrode and its detection in oilseed rape infected with fungal pathogen Sclerotinia sclerotiorum.

    PubMed

    Wang, Zhan; Wei, Fang; Liu, Sheng-Yi; Xu, Qiao; Huang, Jun-Yan; Dong, Xu-Yan; Yu, Jiu-Hong; Yang, Qin; Zhao, Yuan-Di; Chen, Hong

    2010-01-15

    Salicylic acid (SA) is a biological substance that acts as a phytohormone and plays an important role in signal transduction in plants. It is important to accurately and sensitively detect SA levels. A gold electrode modified with copper nanoparticles was used to assay the electrocatalytic oxidation of salicylic acid. It was found that the electrochemical behavior of salicylic acid was greatly improved at copper nanoparticles, indicating that anodic oxidation could be catalyzed at copper nanoparticles. And the pH had remarkable effect on the electrochemical process, a very well-defined oxidation peak appeared at pH 13.3 (0.2M NaOH). The kinetics parameters of this process were calculated and the heterogeneous electron transfer rate constant (k) was determined to be 1.34x10(-3)cms(-1), and (1-alpha)n(alpha) was 1.22. The gold electrode modified with copper nanoparticles could detect SA at a higher sensitivity than common electrodes. The electrode was used to detect the SA levels in oilseed rape infected with the fungal pathogen Sclerotinia sclerotiorum. The results showed that the SA concentration reached a maximum during the 10th-25th hours after infection. This result was very similar to that determined by HPLC, indicating that the gold electrodes modified with copper nanoparticles could be used as salicylic acid sensors.

  6. Assessment of modified gold surfaced titanium implants on skeletal fixation.

    PubMed

    Zainali, Kasra; Danscher, Gorm; Jakobsen, Thomas; Baas, Jorgen; Møller, Per; Bechtold, Joan E; Soballe, Kjeld

    2013-01-01

    Noncemented implants are the primary choice for younger patients undergoing total hip replacements. However, the major concern in this group of patients regarding revision is the concern from wear particles, periimplant inflammation, and subsequently aseptic implant loosening. Macrophages have been shown to liberate gold ions through the process termed dissolucytosis. Furthermore, gold ions are known to act in an anti-inflammatory manner by inhibiting cellular NF-κB-DNA binding. The present study investigated whether partial coating of titanium implants could augment early osseointegration and increase mechanical fixation. Cylindrical porous coated Ti-6Al-4V implants partially coated with metallic gold were inserted in the proximal region of the humerus in ten canines and control implants without gold were inserted in contralateral humerus. Observation time was 4 weeks. Biomechanical push out tests and stereological histomorphometrical analyses showed no statistically significant differences in the two groups. The unchanged parameters are considered an improvement of the coating properties, as a previous complete gold-coated implant showed inferior mechanical fixation and reduced osseointegration compared to control titanium implants in a similar model. Since sufficient early mechanical fixation is achieved with this new coating, it is reasonable to investigate the implant further in long-term studies. PMID:22847873

  7. Modified gold weights for reanimation of the upper lid in facial nerve paralysis.

    PubMed

    Cies, W A

    1993-01-01

    A modified gold weight has been developed for use in paretic upper eyelids following seventh nerve damage. The modified weight is implanted in the pretarsal space. The weight was developed to enhance lid blinking, minimize extrusion, provide better cosmesis, and to provide a good upper lid blinking mechanism.

  8. Determination of trace amounts of ochratoxin A in different food samples based on gold nanoparticles modified carbon paste electrode.

    PubMed

    Afzali, Daryoush; Fathirad, Fariba; Ghaseminezhad, Sima

    2016-01-01

    In the present study, a carbon paste electrode chemically modified with gold nanoparticles was used as a sensitive electrochemical sensor for determination of ochratoxin A. The differential pulse voltammetric method was employed to study the behavior of ochratoxin A on this modified electrode. The effect of variables such as percent of gold nanoparticles, pH of sample solution, accumulation potential and time on voltammogram peak current were optimized. The proposed electrode showed good oxidation response for ochratoxin A in 0.1 mol L(-1) PBS (pH 7.2) and the peak potential was about +0.8 V (vs. Ag/AgCl). The peak current increased linearly with the ochratoxin A concentration in the range of 0.5-100 nM. The detection limit was found to be 0.2 nM and the relative standard deviation was 6.2 % (n = 7). The method has been applied to the determination of ochratoxin A in cereal derived products such as breakfast cereals, cereal-based baby foods and beer samples.

  9. Gold nanoparticle-embedded porous graphene thin films fabricated via layer-by-layer self-assembly and subsequent thermal annealing for electrochemical sensing.

    PubMed

    Xi, Qian; Chen, Xu; Evans, David G; Yang, Wensheng

    2012-06-26

    A uniform three-dimensional (3D) gold nanoparticle (AuNP)-embedded porous graphene (AuEPG) thin film has been fabricated by electrostatic layer-by-layer assembly of AuNPs and graphene nanosheets functionalized with bovine serum albumin and subsequent thermal annealing in air at 340 °C for 2 h. Scanning electron microscopy (SEM) investigations for the AuEPG film indicate that an AuNP was embedded in every pore of the porous graphene film, something that was difficult to achieve with previously reported methods. The mechanism of formation of the AuEPG film was initially explored. Application of the AuEPG film in electrochemical sensing was further demonstrated by use of H(2)O(2) as a model analyte. The AuEPG film-modified electrode showed improved electrochemical performance in H(2)O(2) detection compared with nonporous graphene-AuNP composite film-modified electrodes, which is mainly attributed to the porous structure of the AuEPG film. This work opens up a new and facile way for direct preparation of metal or metal oxide nanoparticle-embedded porous graphene composite films, which will enable exciting opportunities in highly sensitive electrochemical sensors and other advanced applications based on graphene-metal composites.

  10. Functionalized gold nanoparticles/reduced graphene oxide nanocomposites for ultrasensitive electrochemical sensing of mercury ions based on thymine-mercury-thymine structure.

    PubMed

    Wang, Nan; Lin, Meng; Dai, Hongxiu; Ma, Houyi

    2016-05-15

    A sensitive, selective and reusable electrochemical biosensor for the determination of mercury ions (Hg(2+)) has been developed based on thymine (T) modified gold nanoparticles/reduced graphene oxide (AuNPs/rGO) nanocomposites. Graphene oxide (GO) was electrochemically reduced on a glassy carbon substrate. Subsequently, AuNPs were deposited onto the surface of rGO by cyclic voltammetry. For functionalization of the electrode, the carboxylic group of the thymine-1-acetic acid was covalently coupled with the amine group of the cysteamine which self-assembled onto AuNPs. The structural features of the T bases functionalized AuNPs/rGO electrode were confirmed by attenuated total reflection infrared (ATR-IR) spectroscopy and scanning electron microscopy (SEM) spectroscopy. Each step of the modification process was characterized by cyclic voltammetry (CV) and electrochemical impedence spectroscopy (EIS). The T bases modified AuNPs/rGO electrode was applied to detect various trace metal ions by differential pulse voltammetry (DPV). The proposed biosensor was found to be highly sensitive to Hg(2+) in the range of 10 ng/L-1.0 µg/L. The biosensor afforded excellent selectivity for Hg(2+) against other heavy metal ions such as Zn(2+), Cd(2+), Pb(2+), Cu(2+), Ni(2+), and Co(2+). Furthermore, the developed sensor exhibited a high reusability through a simple washing. In addition, the prepared biosensor was successfully applied to assay Hg(2+) in real environmental samples.

  11. Electrochemical Preparation and Characterization of a Gold Nanoparticles Graphite Electrode: Application to Myricetin Antioxidant Analysis.

    PubMed

    Ng, Khan Loon; Lee, See Mun; Khor, Sook Mei; Tan, Guan Huat

    2015-01-01

    Graphite material is abundantly available from recyclable sources. It possesses a good electrical conductance property, which makes it an attractive material as a working electrode. However, due to a high activation overpotential it has limited applications as compared to other solid metal electrodes. In this present work, we obtained a graphite rod from a used battery, and carried out electrochemical improvements by electro-deposition with gold nanoparticles (AuNPs). The heterogeneous electron transfer rate and electron transfer resistance of the fabricated electrode were improved. The electrode overpotential has shown improvement by 50 mV, and the effective surface area has increased by 2 fold. To determine the practicability of the AuNPs/graphite electrode, we used the electrode in the analysis of myricetin. A square-wave voltammetry was used in the analysis, and the detection response increased by 2.5 fold, which suggested an improvement in the electrode sensitivity.

  12. Electrochemical synthesis of mesoporous gold films toward mesospace-stimulated optical properties.

    PubMed

    Li, Cuiling; Dag, Ömer; Dao, Thang Duy; Nagao, Tadaaki; Sakamoto, Yasuhiro; Kimura, Tatsuo; Terasaki, Osamu; Yamauchi, Yusuke

    2015-01-01

    Mesoporous gold (Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles.

  13. Electrochemical synthesis of mesoporous gold films toward mesospace-stimulated optical properties

    PubMed Central

    Li, Cuiling; Dag, Ömer; Dao, Thang Duy; Nagao, Tadaaki; Sakamoto, Yasuhiro; Kimura, Tatsuo; Terasaki, Osamu; Yamauchi, Yusuke

    2015-01-01

    Mesoporous gold (Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles. PMID:25799072

  14. Biogenic synthesis of multidimensional gold nanoparticles assisted by Streptomyces hygroscopicus and its electrochemical and antibacterial properties.

    PubMed

    Sadhasivam, Sathya; Shanmugam, Parthasarathi; Veerapandian, Murugan; Subbiah, Ramesh; Yun, Kyusik

    2012-04-01

    The fabrication of reliable, green chemistry processes for nanomaterial synthesis is an important aspect of nanotechnology. The biosynthesis of single-pot room-temperature reduction of aqueous chloroaurate ions by Streptomyces hygroscopicus cells has been reported to facilitate the development of an industrially viable greener methodology for the synthesis of technologically important gold nanoparticles (AuNPs). Multidimensional AuNPs are generated via the manipulation of key growth parameters, including solution pH and reaction time. The synthesized nanostructures are characterized by UV/Vis and energy dispersive X-ray analysis studies. Particle morphology is characterized by HRTEM, FE-SEM and BioAFM. Additionally, we have demonstrated the electrochemical and antibacterial properties of AuNPs via cyclic voltammetry analysis and a minimal inhibitory concentration assay. Owing to the drawbacks of chemical synthesis, a biological synthesis method has been developed to generate biocompatible, inexpensive and eco-friendly size-controlled nanoparticles.

  15. Electrochemical impedance spectroscopy and laser photoselectivity with gold nanoparticles for food applications

    NASA Astrophysics Data System (ADS)

    Chee, Grace

    With consistently higher and stricter standards for food quality and safety, it is becoming increasingly necessary to be able to quickly and easily determine certain properties of products in order to keep up with and maintain these standards. This master’s thesis is presented in three chapters. First, an overview of the theoretical background, current applications, and new technologies related to taking physiochemical property measurements of food, and various treatment methods used for food safety purposes. In the second chapter, electrochemical impedance spectroscopy (EIS) is used to find the dielectric (DE) constants and other physiochemical properties of potatoes in order to make quick adjustments to improve the microwave processing technique used for potato chipping. Finally, the third chapter introduces the use of a carbon dioxide laser system in conjunction with a two-ZnSe lens beam expander and functionalized gold nanoparticles to specifically target and kill E. coli in food samples.

  16. Synthesis and Functionalization of Gold Nanoparticles Using Chemically Modified ssDNA

    NASA Astrophysics Data System (ADS)

    Calabrese, P. G.

    In the first part of this thesis, methods for functionalizing spherical gold nanoparticles with nucleic acid binding ligands (aptamers) that target the VEGF receptor complex were developed. In order to provide a multiplexed labeling strategy for imaging the VEGF receptor complex in electron microscopy, gold nanoparticles of distinct sizes were conjugated to modified ssDNA aptamers that target the VEGF-A cytokine, the VEGFR-2 RTK receptor and a membrane associated co-receptor, Nrp-1. The modified ssDNA gold nanoparticle conjugates were applied to a human lung carcinoma cell line (A549) which has been shown to express each of these proteins and used as a model system for VEGF signaling. Binding constants for the modified aptamers were also determined using a fluorescence polarization anisotropy assay to determine KD and KOFF for the aptamers with their respective proteins. In the latter part of this thesis, a modied ssDNA SELEX protocol was also developed in order to evolve imidazole modied ssDNA sequences that assemble gold nanoparticles from Au3+ precursor ions in aqueous solution. Active sequences bound to nanoparticles were partitioned from inactive sequences based on density via ultracentrifugation through a discontinuous sucrose gradient. Colloidal gold solutions produced by the evolved pool had a distinct absorbance spectra and produced nanoparticles with a narrower distribution of sizes compared to colloidal gold solutions produced by the starting randomized pool of imidazole modified ssDNA. Sequencing data from the evolved pool shows that conserved 5 and 6 nt motifs were shared amongst many of the isolates, which indicates that these motifs could serve as chelation sites for gold atoms or help stabilize colloidal gold solutions in a base specific manner.

  17. A highly oriented hybrid microarray modified electrode fabricated by a template-free method for ultrasensitive electrochemical DNA recognition.

    PubMed

    Shi, Lei; Chu, Zhenyu; Dong, Xueliang; Jin, Wanqin; Dempsey, Eithne

    2013-11-01

    Highly oriented growth of a hybrid microarray was realized by a facile template-free method on gold substrates for the first time. The proposed formation mechanism involves an interfacial structure-directing force arising from self-assembled monolayers (SAMs) between gold substrates and hybrid crystals. Different SAMs and variable surface coverage of the assembled molecules play a critical role in the interfacial directing forces and influence the morphologies of hybrid films. A highly oriented hybrid microarray was formed on the highly aligned and vertical SAMs of 1,4-benzenedithiol molecules with rigid backbones, which afforded an intense structure-directing power for the oriented growth of hybrid crystals. Additionally, the density of the microarray could be adjusted by controlling the surface coverage of assembled molecules. Based on the hybrid microarray modified electrode with a large specific area (ca. 10 times its geometrical area), a label-free electrochemical DNA biosensor was constructed for the detection of an oligonucleotide fragment of the avian flu virus H5N1. The DNA biosensor displayed a significantly low detection limit of 5 pM (S/N = 3), a wide linear response from 10 pM to 10 nM, as well as excellent selectivity, good regeneration and high stability. We expect that the proposed template-free method can provide a new reference for the fabrication of a highly oriented hybrid array and the as-prepared microarray modified electrode will be a promising paradigm in constructing highly sensitive and selective biosensors.

  18. Application of electrochemical impedance spectroscopy for monitoring allergen-antibody reactions using gold nanoparticle-based biomolecular immobilization method.

    PubMed

    Huang, Haizhen; Liu, Zhigang; Yang, Xiurong

    2006-09-15

    Gold nanoparticles were used to enhance the immobilization amount and retain the immunoactivity of recombinant dust mite allergen Der f2 immobilized on a glassy carbon electrode (GCE). The interaction between allergen and antibody was studied by electrochemical impedance spectroscopy (EIS). Self-assembled Au colloid layer (ø=16nm) deposited on (3-mercaptopropyl)trimethoxysilane (MPTS)-modified GCE offered a basis to control the immobilization of allergen Der f2. The impedance measurements were based on the charge transfer kinetics of the [Fe(CN)(6)](3-/4-) redox pair, compared with bare GCE, the immobilization of allergen Der f2 and the allergen-antibody interaction that occurred on the electrode surface altered the interfacial electron transfer resistance and thereby slowed down the charge transfer kinetics by reducing the active area of the electrode or by preventing the redox species in electrolyte solution from approaching the electrode. The interactions of allergen with various concentrations of monoclonal antibody were also monitored through the change of impedance response. The results showed that the electron transfer resistance increased with increasing concentrations of monoclonal antibody. PMID:16836968

  19. Multiplexed Electrochemical Immunoassay of Phosphorylated Proteins Based on Enzyme-Functionalized Gold Nanorod Labels and Electric Field-Driven Acceleration

    SciTech Connect

    Du, Dan; Wang, Jun; Lu, Donglai; Dohnalkova, Alice; Lin, Yuehe

    2011-09-09

    A multiplexed electrochemical immunoassay integrating enzyme amplification and electric field-driven strategy was developed for fast and sensitive quantification of phosphorylated p53 at Ser392 (phospho-p53 392), Ser15 (phospho-p53 15), Ser46 (phospho-p53 46) and total p53 simultaneously. The disposable sensor array has four spatially separated working electrodes and each of them is modified with different capture antibody, which enables simultaneous immunoassay to be conducted without cross-talk between adjacent electrodes. The enhanced sensitivity was achieved by multi-enzymes amplification strategy using gold nanorods (AuNRs) as nanocarrier for co-immobilization of horseradish peroxidase (HRP) and detection antibody (Ab2) at high ratio of HRP/Ab2, which produced an amplified electrocatalytic response by the reduction of HRP oxidized thionine in the presence of hydrogen peroxide. The immunoreaction processes were accelerated by applying +0.4 V for 3 min and then -0.2 V for 1.5 min, thus the whole sandwich immunoreactions could be completed in less than 5 min. The disposable immunosensor array shows excellent promise for clinical screening of phosphorylated proteins and convenient point-of-care diagnostics.

  20. Ultrasensitive multiplexed immunoassay with electrochemical stripping analysis of silver nanoparticles catalytically deposited by gold nanoparticles and enzymatic reaction.

    PubMed

    Lai, Guosong; Yan, Feng; Wu, Jie; Leng, Chuan; Ju, Huangxian

    2011-04-01

    A novel ultrasensitive multiplexed immunoassay method was developed by combining alkaline phosphatase (ALP)-labeled antibody functionalized gold nanoparticles (ALP-Ab/Au NPs) and enzyme-Au NP catalyzed deposition of silver nanoparticles at a disposable immunosensor array. The immunosensor array was prepared by covalently immobilizing capture antibodies on chitosan modified screen-printed carbon electrodes. After sandwich-type immunoreactions, the ALP-Ab/Au NPs were captured on an immunosensor surface to catalyze the hydrolysis of 3-indoxyl phosphate, which produced an indoxyl intermediate to reduce Ag(+). The silver deposition process was catalyzed by both ALP and Au NPs, which amplified the detection signal. The deposited silver was then measured by anodic stripping analysis in KCl solution. Using human and mouse IgG as model analytes, this multiplexed immunoassay method showed wide linear ranges over 4 orders of magnitude with the detection limits down to 4.8 and 6.1 pg/mL, respectively. Acceptable assay results for practical samples could be obtained. The newly designed strategy avoided cross talk and the need of deoxygenation for the electrochemical immunoassay and, thus, provided a promising potential in clinical applications.

  1. DNA polymorphism sensitive impedimetric detection on gold-nanoislands modified electrodes.

    PubMed

    Bonanni, Alessandra; Pividori, Maria Isabel; del Valle, Manel

    2015-05-01

    Nanocomposite materials are being increasingly used in biosensing applications as they can significantly improve biosensor performance. Here we report the use of a novel impedimetric genosensor based on gold nanoparticles graphite-epoxy nanocomposite (nanoAu-GEC) for the detection of triple base mutation deletion in a cystic-fibrosis (CF) related human DNA sequence. The developed platform consists of chemisorbing gold nano-islands surrounded by rigid, non-chemisorbing, and conducting graphite-epoxy composite. The ratio of the gold nanoparticles in the composite was carefully optimized by electrochemical and microscopy studies. Such platform allows the very fast and stable thiol immobilization of DNA probes on the gold islands, thus minimizing the steric and electrostatic repulsion among the DNA probes and improving the detection of DNA polymorphism down to 2.25fmol by using electrochemical impedance spectroscopy. These findings are very important in order to develop new and renewable platforms to be used in point-of-care devices for the detection of biomolecules.

  2. Oxide modified air electrode surface for high temperature electrochemical cells

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1992-01-01

    An electrochemical cell is made having a porous cermet electrode (16) and a porous lanthanum manganite electrode (14), with solid oxide electrolyte (15) between them, where the lanthanum manganite surface next to the electrolyte contains a thin discontinuous layer of high surface area cerium oxide and/or praseodymium oxide, preferably as discrete particles (30) in contact with the air electrode and electrolyte.

  3. Peptide-modified gold nanoparticles for improved cancer therapeutics

    NASA Astrophysics Data System (ADS)

    Yang, Celina; Prooijen, Monique V.; Chithrani, Devika B.

    2014-03-01

    The field of nanotechnology is currently undergoing explosive development on many fronts. The technology is expected to generate innovations and play a critical role in cancer therapeutics. Among other nanoparticle (NP) systems, there has been tremendous progress made in the use of spherical gold NPs (GNPs) in cancer therapeutics. In treating cancer, radiation therapy and chemotherapy remain the most widely used treatment options. These nanostructures further provide strategies for improving loading, targeting, and controlling the release of drugs to minimize the side effects of highly toxic anticancer drugs used in chemotherapy. Our recent results show enhancement of cell death during radiation therapy when GNPs are targeted to nucleus. In addition, we have seen enhanced therapeutic effects when GNPs are used as anticancer drug carriers. Hence, gold nanostructures provide a versatile platform to integrate many therapeutic options leading to effective combinational therapy in the fight against cancer. A multifunctional platform based on gold nanostructures with targeting ligands, therapeutic molecules, and imaging contrast agents will hold the possibility of promising directions in cancer research.

  4. Using femtosecond lasers to modify sizes of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    da Silva Cordeiro, Thiago; Almeida de Matos, Ricardo; Silva, Flávia Rodrigues de Oliveira; Vieira, Nilson D.; Courrol, Lilia C.; Samad, Ricardo E.

    2016-04-01

    Metallic nanoparticles are important on several scientific, medical and industrial areas. The control of nanoparticles characteristics has fundamental importance to increase the efficiency on the processes and applications in which they are employed. The metallic nanoparticles present specific surface plasmon resonances (SPR). These resonances are related with the collective oscillations of the electrons presents on the metallic nanoparticle. The SPR is determined by the potential defined by the nanoparticle size and geometry. There are several methods of producing gold nanoparticles, including the use of toxic chemical polymers. We already reported the use of natural polymers, as for example, the agar-agar, to produce metallic nanoparticles under xenon lamp irradiation. This technique is characterized as a "green" synthesis because the natural polymers are inoffensive to the environment. We report a technique to produce metallic nanoparticles and change its geometrical and dimensional characteristics using a femtosecond laser. The 1 ml initial solution was irradiate using a laser beam with 380 mW, 1 kHz and 40 nm of bandwidth centered at 800 nm. The setup uses an Acousto-optic modulator, Dazzler, to change the pulses spectral profiles by introduction of several orders of phase, resulting in different temporal energy distributions. The use of Dazzler has the objective of change the gold nanoparticles average size by the changing of temporal energy distributions of the laser pulses incident in the sample. After the laser irradiation, the gold nanoparticles average diameter were less than 15 nm.

  5. Electroanalysis of dopamine at a gold electrode modified with N-acetylcysteine self-assembled monolayer.

    PubMed

    Liu, Ting; Li, Meixian; Li, Qianyuan

    2004-07-01

    Voltammetric behavior of dopamine (DA) on a gold electrode modified with the self-assembled monolayer (SAM) of N-acetylcysteine has been investigated, and one pair of well-defined redox peaks of dopamine is obtained at the SAM modified gold electrode. The oxidation peak current increases linearly with the concentration of dopamine in the range of 1.0x10 (-6)to 2.0x10 (-4)moll(-1). The detection limit is 8.0x10(-7)moll(-1). This method will be applicable to the determination of dopamine in injection of dopamine hydrochloride, and the good recovery of dopamine is obtained. Furthermore, The SAM modified gold electrode can resolve well the voltammetric responses of dopamine and ascorbic acid (AA), so it can also be applied to the determination of dopamine in the presence of ascorbic acid.

  6. Efficient fluorescence quenching in electrochemically exfoliated graphene decorated with gold nanoparticles.

    PubMed

    Hurtado-Morales, M; Ortiz, M; Acuña, C; Nerl, H C; Nicolosi, V; Hernández, Y

    2016-07-01

    High surface area graphene sheets were obtained by electrochemical exfoliation of graphite in an acid medium under constant potential conditions. Filtration and centrifugation processes played an important role in order to obtain stable dispersions in water. Scanning electron microscopy and transmission electron microscopy imaging revealed highly exfoliated crystalline samples of ∼5 μm. Raman, Fourier transform infrared and x-ray photoelectron spectroscopy further confirmed the high quality of the exfoliated material. The electrochemically exfoliated graphene (EEG) was decorated with gold nanoparticles (AuNPs) using sodium cholate as a buffer layer. This approach allowed for a non-covalent functionalization without altering the desirable electronic properties of the EEG. The AuNP-EEG samples were characterized with various techniques including absorbance and fluorescence spectroscopy. These samples displayed a fluorescence signal using an excitation wavelength of 290 nm. The calculated quantum yield (Φ) for these samples was 40.04%, a high efficiency compared to previous studies using solution processable graphene.

  7. Efficient fluorescence quenching in electrochemically exfoliated graphene decorated with gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Hurtado-Morales, M.; Ortiz, M.; Acuña, C.; Nerl, H. C.; Nicolosi, V.; Hernández, Y.

    2016-07-01

    High surface area graphene sheets were obtained by electrochemical exfoliation of graphite in an acid medium under constant potential conditions. Filtration and centrifugation processes played an important role in order to obtain stable dispersions in water. Scanning electron microscopy and transmission electron microscopy imaging revealed highly exfoliated crystalline samples of ∼5 μm. Raman, Fourier transform infrared and x-ray photoelectron spectroscopy further confirmed the high quality of the exfoliated material. The electrochemically exfoliated graphene (EEG) was decorated with gold nanoparticles (AuNPs) using sodium cholate as a buffer layer. This approach allowed for a non-covalent functionalization without altering the desirable electronic properties of the EEG. The AuNP-EEG samples were characterized with various techniques including absorbance and fluorescence spectroscopy. These samples displayed a fluorescence signal using an excitation wavelength of 290 nm. The calculated quantum yield (Φ) for these samples was 40.04%, a high efficiency compared to previous studies using solution processable graphene.

  8. Electrochemical genosensor assay using lyophilized gold nanoparticles/latex microsphere label for detection of Vibrio cholerae.

    PubMed

    Liew, Pei Sheng; Lertanantawong, Benchaporn; Lee, Su Yin; Manickam, Ravichandran; Lee, Yook Heng; Surareungchai, Werasak

    2015-07-01

    Vibrio cholerae is a Gram-negative bacterium that causes cholera, a diarrheal disease. Cholera is widespread in poor, under-developed or disaster-hit countries that have poor water sanitation. Hence, a rapid detection method for V. cholerae in the field under these resource-limited settings is required. In this paper, we describe the development of an electrochemical genosensor assay using lyophilized gold nanoparticles/latex microsphere (AuNPs-PSA) reporter label. The reporter label mixture was prepared by lyophilization of AuNPs-PSA-avidin conjugate with different types of stabilizers. The best stabilizer was 5% sorbitol, which was able to preserve the dried conjugate for up to 30 days. Three methods of DNA hybridization were compared and the one-step sandwich hybridization method was chosen as it was fastest and highly specific. The performance of the assay using the lyophilized reagents was comparable to the wet form for detection of 1aM to 1fM of linear target DNA. The assay was highly specific for V. cholerae, with a detection limit of 1fM of PCR products. The ability of the sensor is to detect LAMP products as low as 50ngµl(-1). The novel lyophilized AuNPs-PSA-avidin reporter label with electrochemical genosensor detection could facilitate the rapid on-site detection of V. cholerae.

  9. New insight into the electrochemical desorption of alkanethiol SAMs on gold.

    PubMed

    Pensa, Evangelina; Vericat, Carolina; Grumelli, Doris; Salvarezza, Roberto C; Park, Sung Hyun; Longo, Gabriel S; Szleifer, Igal; Méndez De Leo, Lucila P

    2012-09-21

    A combination of Polarization Modulation Infrared Reflection Absorption Spectroscopy (PMIRRAS) under electrochemical control, Electrochemical Scanning Tunneling Microscopy (ECSTM) and Molecular Dynamics (MD) simulations has been used to shed light on the reductive desorption process of dodecanethiol (C12) and octadecanethiol (C18) SAMs on gold in aqueous electrolytes. Experimental PMIRRAS, ECSTM and MD simulations data for C12 desorption are consistent with formation of randomly distributed micellar aggregates stabilized by Na(+) ions, coexisting with a lying-down phase of molecules. The analysis of pit and Au island coverage before and after desorption is consistent with the thiolate-Au adatoms models. On the other hand, PMIRRAS and MD data for C18 indicate that the desorbed alkanethiolates adopt a Na(+) ion-stabilized bilayer of interdigitated alkanethiolates, with no evidence of lying down molecules. MD simulations also show that both the degree of order and tilt angle of the desorbed alkanethiolates change with the surface charge on the metal, going from bilayers to micelles. These results demonstrate the complexity of the alkanethiol desorption in the presence of water and the fact that chain length and counterions play a key role in a complex structure.

  10. Electrochemical endotoxin sensors based on TLR4/MD-2 complexes immobilized on gold electrodes.

    PubMed

    Yeo, Tae Yun; Choi, Ji Suk; Lee, Byung Kook; Kim, Beob Soo; Yoon, Hwa In; Lee, Hyeong Yun; Cho, Yong Woo

    2011-10-15

    Even low concentrations of endotoxins can be life-threatening. As such, continuous effort has been directed toward the development of sensitive and specific endotoxin detection systems. In this paper, we report the design and fabrication of a new electrochemical endotoxin sensor based on a human recombinant toll-like receptor 4 (rhTLR4) and myeloid differentiation-2 (MD-2) complex. The rhTLR4/MD-2 complex, which specifically binds to endotoxin, was immobilized on gold electrodes through a self-assembled monolayer (SAM) technique involving the use of dithiobis(succinimidyl undecanoate) (DSU). The surface topography of the electrodes at each fabrication stage was characterized with a nanosurface profiler and atomic force microscope (AFM). The electrochemical signals generated from interactions between the rhTLR4/MD-2 complex and the endotoxin were characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). A linear relationship between the peak current and endotoxin concentration was obtained in the range of 0.0005 to 5 EU/mL with a correlation coefficient (R(2)) of 0.978. The estimated limit of detection (LOD) was fairly low, 0.0002 EU/mL. The rhTLR4/MD-2 based sensors exhibited no current responses to dipalmitoylphosphatidylcholine (DPPC) bearing two lipid chains, which is structurally similar to endotoxin, indicating the high specificity of the sensors to endotoxin. PMID:21816600

  11. Aptamer-based electrochemical biosensor for detection of adenosine triphosphate using a nanoporous gold platform.

    PubMed

    Kashefi-Kheyrabadi, Leila; Mehrgardi, Masoud A

    2013-12-01

    In spite of the promising applications of aptamers in the bioassays, the development of aptamer-based electrochemical biosensors with the improved limit of detection has remained a great challenge. A strategy for the amplification of signal, based on application of nanostructures as platforms for the construction of an electrochemical adenosine triphosphate (ATP) aptasensor, is introduced in the present manuscript. A sandwich assay is designed by immobilizing a fragment of aptamer on a nanoporous gold electrode (NPGE) and its association to second fragment in the presence of ATP. Consequently, 3, 4-diaminobenzoic acid (DABA), as a molecular reporter, is covalently attached to the amine-label of the second fragment, and the direct oxidation signal of DABA is followed as the analytical signal. The sensor can detect the concentrations of ATP as low as submicromolar scales. Furthermore, 3.2% decrease in signal is observed by keeping the aptasensor at 4 °C for a week in buffer solution, implying a desirable stability. Moreover, analog nucleotides, including GTP, UTP and CTP, do not show serious interferences and this sensor easily detects its target in deproteinized human blood plasma.

  12. Silver deposition directed by self-assembled gold nanorods for amplified electrochemical immunoassay.

    PubMed

    Zhang, Hongfang; Ning, Danlei; Ma, Lina; Zheng, Jianbin

    2016-01-01

    A novel electrochemical immunoassay was developed based on the signal amplification strategy of silver deposition directed by gold nanorods (AuNRs), which was in-situ assembled on the sandwich immunocomplex. The superstructure formed by the self-assembly of AuNRs provided abundant active sites for the nucleation of silver nanoparticles. In this pathway, the stripping current of silver was greatly enhanced. Using human immunoglobulin G (HIgG) as a model analyte, the ultrasensitive immunoassay showed a wide linear range of six orders of magnitude from 0.1 fg mL(-1) to 100 pg mL(-1), with the low detection limit down to 0.08 fg mL(-1). The practicality of this electrochemical immunoassay for detection of HIgG in serum was validated with the average recovery of 93.9%. In addition, this enzyme-free immunoassay also has the advantages of acceptable reproducibility and specificity, and thus this immunosensing protocol can be extended to the detection of other low-abundant protein biomarkers.

  13. Gold-nanoparticle based electrochemical DNA sensor for the detection of fish pathogen Aphanomyces invadans.

    PubMed

    Kuan, Guan Chin; Sheng, Liew Pei; Rijiravanich, Patsamon; Marimuthu, Kasi; Ravichandran, Manickam; Yin, Lee Su; Lertanantawong, Benchaporn; Surareungchai, Werasak

    2013-12-15

    Epizootic ulcerative syndrome (EUS) is a devastating fish disease caused by the fungus, Aphanomyces invadans. Rapid diagnosis of EUS is needed to control and treat this highly invasive disease. The current diagnostic methods for EUS are labor intensive. We have developed a highly sensitive and specific electrochemical genosensor towards the 18S rRNA and internal transcribed spacer regions of A. invadans. Multiple layers of latex were synthesized with the help of polyelectrolytes, and labeled with gold nanoparticles to enhance sensitivity. The gold-latex spheres were functionalized with specific DNA probes. We describe here the novel application of this improved platform for detection of PCR product from real sample of A. invadans using a premix sandwich hybridization assay. The premix assay was easier, more specific and gave higher sensitivity of one log unit when compared to the conventional method of step-by-step hybridization. The limit of detection was 0.5 fM (4.99 zmol) of linear target DNA and 1 fM (10 amol) of PCR product. The binding positions of the probes to the PCR amplicons were optimized for efficient hybridization. Probes that hybridized close to the 5' or 3' terminus of the PCR amplicons gave the highest signal due to minimal steric hindrance for hybridization. The genosensor is highly suitable as a surveillance and diagnostic tool for EUS in the aquaculture industry.

  14. An electrochemical study of hydrogen uptake and elimination by bare and gold-plated waspaloy

    NASA Technical Reports Server (NTRS)

    Danford, M. D.; Deramus, G. E., Jr.; Lowery, J. R.

    1984-01-01

    Two electrochemical methods for the determination of hydrogen concentrations in metals are discussed and evaluated. The take-up of hydrogen at a pressure of 5000 psi by Waspaloy metal was determined experimentally at 24 C. It was found that the metal becomes saturated with hydrogen after an exposure time of about 1 hr. For samples charged with hydrogen at high pressure, most of the hydrogen is contained in the interstitial solid solution of the metal. For electrolytically charged samples, most of the hydrogen is contained as surface and subsurface hydrides. Hydrogen elimination rates were determined for these two cases, with the rate for electrolytically charged samples being greater by over a factor of two. Theoretical effects of high temperature and pressure on hydrogen take-up and elimination by bare and gold plated Waspaloy metal was considered. The breakthrough point for hydrogen at 5000 psi, determined experimentally, lies between a gold thickness of 0.0127 mm (0.0005 in.) and 0.0254 mm (0.001 in.) at 24 C. Electropolishing was found to greatly reduce the uptake of hydrogen at high pressure by Waspaloy metal at 24 C. Possible implications of the results obtained, as they apply to the turbine disk of the space shuttle main engine, are discussed.

  15. One pot synthesis of poly(5-hydroxyl-1,4-naphthoquinone) stabilized gold nanoparticles using the monomer as the reducing agent for nonenzymatic electrochemical detection of glucose.

    PubMed

    Cooray, M C Dilusha; Liu, Yuping; Langford, Steven J; Bond, Alan M; Zhang, Jie

    2015-01-26

    Monodispersed and highly stable gold nanoparticles with a diameter between 8 and 9 nm were synthesized in a weakly alkaline medium by chemical reduction of AuCl4(-) using 5-hydroxyl-1,4-naphthoquinone, and stabilized by the simultaneously formed poly(hydroxyl-1,4-naphthoquinone). The electrochemical properties of the resultant poly(hydroxyl-1,4-naphthoquinone) stabilized gold nanoparticles (AuNQ NPs) and its electrocatalytic activity for glucose oxidation in alkaline media were then investigated using a range of techniques, including dc cyclic, rotating disk electrode and Fourier transformed large amplitude ac voltammetry. The results demonstrate that these AuNQ NP modified electrodes exhibit excellent catalytic activity toward glucose oxidation in the potential region where the premonolayer oxidation process occurs. The overall catalytic glucose oxidation process was found to be mass transport controlled under the experimental conditions employed, allowing measurements to be conducted with a high reproducibility. The AuNQ NP modified electrodes showed a high sensitivity of 183 μA mM(-1) cm(-2) with a wide linear dynamic range of 0.5-50 mM and a detection limit of 61 μM. However, despite its excellent tolerance toward ascorbic acid, significant interference from uric acid was found with this AuNQ NP modified electrode.

  16. Hampering of the Stability of Gold Electrodes by Ferri-/Ferrocyanide Redox Couple Electrolytes during Electrochemical Impedance Spectroscopy.

    PubMed

    Lazar, Jaroslav; Schnelting, Christoph; Slavcheva, Evelina; Schnakenberg, Uwe

    2016-01-01

    In the past decades, numerous measurements have applied electrochemical impedance spectroscopy (EIS) in an electrode-electrolyte system consisting of gold electrodes and the redox couple potassium ferrocyanide/potassium ferricyanide (HCF). Yet these measurements are often hampered by false positive and negative results. Electrochemical impedance signals often display a nonlinear drift in electrolyte systems containing the HCF redox couple, which can mask the accuracy of the analysis. Thus, this Article aims to elucidate the stability and reliability of this particular electrode-electrolyte system. Here, different gold electrode cleaning treatments were compared with respect to adsorption and roughness of the surface of gold electrodes. They show substantial nonlinear long-term drifts of the charge-transfer resistance RD. In particular, the use of HCF-containing electrolytes causes adsorption and corrosion on the gold electrode surface, resulting in a nonlinear impedance behavior that depends on the incubation period as well as on electrolyte composition. Consequently, it is strongly recommended not to use HCF containing electrolytes in combination with gold electrodes.

  17. Parametric study on electrochemical deposition of copper nanoparticles on an ultrathin polypyrrole film deposited on a gold film electrode.

    PubMed

    Zhou, X J; Harmer, A J; Heinig, N F; Leung, K T

    2004-06-01

    Monoshaped and monosized copper nanostructured particles have been prepared by potentiostatic electrochemical deposition on an ultrathin polypyrrole (PPY) film, electrochemically grown on a Si(100) substrate sputter-coated with a thin gold film or gold-film electrode (GFE). The crystal size and the number density of the copper nanocrystals have been examined by varying several deposition parameters, including the thickness of the gold film, the PPY film thickness, the applied potential, and the Cu2+ and the electrolyte concentrations for copper deposition. Optimal conditions for uniform growth ofnanocrystals well-dispersed on the GFE have been determined, along with insight into the mechanism of crystal growth. A minimum gold film thickness of 80 nm is required to eliminate the effects of the gold-silicon interface. The PPY film thickness and homogeneity principally affect the shape uniformity of the nanocrystals, while the copper deposition potential could be used to regulate the size and number density of the nanocrystals. Both the Cu2+ and electrolyte concentrations are also found to play important roles in controlling the electrodeposition of nanocrystal growth.

  18. Application of three-dimensional reduced graphene oxide-gold composite modified electrode for direct electrochemistry and electrocatalysis of myoglobin.

    PubMed

    Shi, Fan; Xi, Jingwen; Hou, Fei; Han, Lin; Li, Guangjiu; Gong, Shixing; Chen, Chanxing; Sun, Wei

    2016-01-01

    In this paper a three-dimensional (3D) reduced graphene oxide (RGO) and gold (Au) composite was synthesized by electrodeposition and used for the electrode modification with carbon ionic liquid electrode (CILE) as the substrate electrode. Myoglobin (Mb) was further immobilized on the surface of 3D RGO-Au/CILE to obtain an electrochemical sensing platform. Direct electrochemistry of Mb on the modified electrode was investigated with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Mb with the modified electrode. The results can be ascribed to the presence of highly conductive 3D RGO-Au composite on the electrode surface that accelerate the electron transfer rate between the electroactive center of Mb and the electrode. The Mb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the concentration range from 0.2 to 36.0 mmol/L with the detection limit of 0.06 mmol/L (3σ).

  19. A highly oriented hybrid microarray modified electrode fabricated by a template-free method for ultrasensitive electrochemical DNA recognition

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Chu, Zhenyu; Dong, Xueliang; Jin, Wanqin; Dempsey, Eithne

    2013-10-01

    Highly oriented growth of a hybrid microarray was realized by a facile template-free method on gold substrates for the first time. The proposed formation mechanism involves an interfacial structure-directing force arising from self-assembled monolayers (SAMs) between gold substrates and hybrid crystals. Different SAMs and variable surface coverage of the assembled molecules play a critical role in the interfacial directing forces and influence the morphologies of hybrid films. A highly oriented hybrid microarray was formed on the highly aligned and vertical SAMs of 1,4-benzenedithiol molecules with rigid backbones, which afforded an intense structure-directing power for the oriented growth of hybrid crystals. Additionally, the density of the microarray could be adjusted by controlling the surface coverage of assembled molecules. Based on the hybrid microarray modified electrode with a large specific area (ca. 10 times its geometrical area), a label-free electrochemical DNA biosensor was constructed for the detection of an oligonucleotide fragment of the avian flu virus H5N1. The DNA biosensor displayed a significantly low detection limit of 5 pM (S/N = 3), a wide linear response from 10 pM to 10 nM, as well as excellent selectivity, good regeneration and high stability. We expect that the proposed template-free method can provide a new reference for the fabrication of a highly oriented hybrid array and the as-prepared microarray modified electrode will be a promising paradigm in constructing highly sensitive and selective biosensors.Highly oriented growth of a hybrid microarray was realized by a facile template-free method on gold substrates for the first time. The proposed formation mechanism involves an interfacial structure-directing force arising from self-assembled monolayers (SAMs) between gold substrates and hybrid crystals. Different SAMs and variable surface coverage of the assembled molecules play a critical role in the interfacial directing forces and

  20. Enhancement of electrogenerated chemiluminescence of luminol by ascorbic acid at gold nanoparticle/graphene modified glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Dong, Yongping; Gao, Tingting; Zhou, Ying; Chu, Xiangfeng; Wang, Chengming

    2015-01-01

    Gold nanoparticle/graphene (GNP/GR) nanocomposite was one-pot synthesized from water soluble graphene and HAuCl4 by hydrothermal method and characterized by TEM, Raman spectroscopy, XRD, XPS, UV-vis spectroscopy, and electrochemical impedance spectroscopy (EIS). Electrogenerated chemiluminescence (ECL) of luminol was investigated at the GNP/GR modified glassy carbon electrode (GNP/GR/GCE) and the GNP modified glassy carbon electrode (GNP/GCE) in aqueous solution respectively. The results revealed that one strong anodic ECL peak could be observed at ∼0.8 V at two modified electrodes compared with that at the bare electrode. The intensity of the anodic ECL at the GNP/GR/GCE is weaker than that at the GNP/GCE, which should be due to the synergic effect of the enhancing effect of gold nanoparticles and the inhibiting effect of graphene on anodic luminol ECL. One strong cathodic ECL peak located at ∼-0.8 V could be observed at the GNP/GR/GCE but not at the GNP/GCE, which should be result from the adsorbed oxygen at the graphene film. In the presence of ascorbic acid, the anodic ECL at the GNP/GR/GCE was enhanced more than 8-times, which is more apparent than that at the GNP/GCE. Whereas, the cathodic ECL peak was seriously inhibited at the GNP/GR/GCE. The enhanced ECL intensity at the GNP/GR/GCE varied linearly with the logarithm of ascorbic acid concentration in the range of 1.0 × 10-8 to 1.0 × 10-6 mol L-1 with a detection limit of 1.0 × 10-9 mol L-1. The possible ECL mechanism was also discussed.

  1. Electrochemical and DFT study of an anticancer and active anthelmintic drug at carbon nanostructured modified electrode.

    PubMed

    Ghalkhani, Masoumeh; Beheshtian, Javad; Salehi, Maryam

    2016-12-01

    The electrochemical response of mebendazole (Meb), an anticancer and effective anthelmintic drug, was investigated using two different carbon nanostructured modified glassy carbon electrodes (GCE). Although, compared to unmodified GCE, both prepared modified electrodes improved the voltammetric response of Meb, the carbon nanotubes (CNTs) modified GCE showed higher sensitivity and stability. Therefore, the CNTs-GCE was chosen as a promising candidate for the further studies. At first, the electrochemical behavior of Meb was studied by cyclic voltammetry and differential pulse and square wave voltammetry. A one step reversible, pH-dependent and adsorption-controlled process was revealed for electro-oxidation of Meb. A possible mechanism for the electrochemical oxidation of Meb was proposed. In addition, electronic structure, adsorption energy, band gap, type of interaction and stable configuration of Meb on the surface of functionalized carbon nanotubes were studied by using density functional theory (DFT). Obtained results revealed that Meb is weakly physisorbed on the CNTs and that the electronic properties of the CNTs are not significantly changed. Notably, CNTs could be considered as a suitable modifier for preparation of the modified electrode for Meb analysis. Then, the experimental parameters affecting the electrochemical response of Meb were optimized. Under optimal conditions, high sensitivity (b(Meb)=dIp,a(Meb)/d[Meb]=19.65μAμM(-1)), a low detection limit (LOD (Meb)=19nM) and a wide linear dynamic range (0.06-3μM) was resulted for the voltammetric quantification of Meb. PMID:27612835

  2. Optimization of modified carbon paste electrode with multiwalled carbon nanotube/ionic liquid/cauliflower-like gold nanostructures for simultaneous determination of ascorbic acid, dopamine and uric acid.

    PubMed

    Afraz, Ahmadreza; Rafati, Amir Abbas; Najafi, Mojgan

    2014-11-01

    We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNTs) and an ionic liquid (IL). Electrochemical studies by using a D-optimal mixture design in Design-Expert software revealed an optimized composition of 60% graphite, 14.2% paraffin, 10.8% MWCNT and 15% IL. The optimal modified CPE shows good electrochemical properties that are well matched with model prediction parameters. In the next step, the optimized CPE was modified with gold nanostructures by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and electrochemical impedance spectroscopy. It gives three sharp and well-separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA). The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.3 to 285, 0.08 to 200, and 0.1 to 450 μM, respectively, and with 120, 30 and 30 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine.

  3. Plasmonic gold nanoparticles modified titania nanotubes for antibacterial application

    SciTech Connect

    Li, Jinhua; Zhou, Huaijuan; Qian, Shi; Liu, Ziwei; Feng, Jingwei; Jin, Ping E-mail: xyliu@mail.sic.ac.cn; Liu, Xuanyong E-mail: xyliu@mail.sic.ac.cn

    2014-06-30

    Close-packed TiO{sub 2} nanotube arrays are prepared on metallic Ti surface by electrochemical anodization. Subsequently, by magnetron sputtering, Au nanoparticles are coated onto the top sidewall and tube inwall. The Au@TiO{sub 2} systems can effectively kill Staphylococcus aureus and Escherichia coli in darkness due to the existence of Au nanoparticles. On the basis of classical optical theories, the antibacterial mechanism is proposed from the perspective of localized surface plasmon resonance. Respiratory electrons of bacterial membrane transfer to Au nanoparticles and then to TiO{sub 2}, which makes bacteria steadily lose electrons until death. This work provides insights for the better understanding and designing of noble metal nanoparticles-based plasmonic heterostructures for antibacterial application.

  4. Synergistic geometric and electronic effects for electrochemical reduction of carbon dioxide using gold-copper bimetallic nanoparticles.

    PubMed

    Kim, Dohyung; Resasco, Joaquin; Yu, Yi; Asiri, Abdullah Mohamed; Yang, Peidong

    2014-09-11

    Highly efficient and selective electrochemical reduction of carbon dioxide represents one of the biggest scientific challenges in artificial photosynthesis, where carbon dioxide and water are converted into chemical fuels from solar energy. However, our fundamental understanding of the reaction is still limited and we do not have the capability to design an outstanding catalyst with great activity and selectivity a priori. Here we assemble uniform gold-copper bimetallic nanoparticles with different compositions into ordered monolayers, which serve as a well-defined platform to understand their fundamental catalytic activity in carbon dioxide reduction. We find that two important factors related to intermediate binding, the electronic effect and the geometric effect, dictate the activity of gold-copper bimetallic nanoparticles. These nanoparticle monolayers also show great mass activities, outperforming conventional carbon dioxide reduction catalysts. The insights gained through this study may serve as a foundation for designing better carbon dioxide electrochemical reduction catalysts.

  5. Synergistic geometric and electronic effects for electrochemical reduction of carbon dioxide using gold-copper bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Dohyung; Resasco, Joaquin; Yu, Yi; Asiri, Abdullah Mohamed; Yang, Peidong

    2014-09-01

    Highly efficient and selective electrochemical reduction of carbon dioxide represents one of the biggest scientific challenges in artificial photosynthesis, where carbon dioxide and water are converted into chemical fuels from solar energy. However, our fundamental understanding of the reaction is still limited and we do not have the capability to design an outstanding catalyst with great activity and selectivity a priori. Here we assemble uniform gold-copper bimetallic nanoparticles with different compositions into ordered monolayers, which serve as a well-defined platform to understand their fundamental catalytic activity in carbon dioxide reduction. We find that two important factors related to intermediate binding, the electronic effect and the geometric effect, dictate the activity of gold-copper bimetallic nanoparticles. These nanoparticle monolayers also show great mass activities, outperforming conventional carbon dioxide reduction catalysts. The insights gained through this study may serve as a foundation for designing better carbon dioxide electrochemical reduction catalysts.

  6. Synergistic geometric and electronic effects for electrochemical reduction of carbon dioxide using gold-copper bimetallic nanoparticles.

    PubMed

    Kim, Dohyung; Resasco, Joaquin; Yu, Yi; Asiri, Abdullah Mohamed; Yang, Peidong

    2014-01-01

    Highly efficient and selective electrochemical reduction of carbon dioxide represents one of the biggest scientific challenges in artificial photosynthesis, where carbon dioxide and water are converted into chemical fuels from solar energy. However, our fundamental understanding of the reaction is still limited and we do not have the capability to design an outstanding catalyst with great activity and selectivity a priori. Here we assemble uniform gold-copper bimetallic nanoparticles with different compositions into ordered monolayers, which serve as a well-defined platform to understand their fundamental catalytic activity in carbon dioxide reduction. We find that two important factors related to intermediate binding, the electronic effect and the geometric effect, dictate the activity of gold-copper bimetallic nanoparticles. These nanoparticle monolayers also show great mass activities, outperforming conventional carbon dioxide reduction catalysts. The insights gained through this study may serve as a foundation for designing better carbon dioxide electrochemical reduction catalysts. PMID:25208828

  7. A polydopamine-modified optical fiber SPR biosensor using electroless-plated gold films for immunoassays.

    PubMed

    Shi, Se; Wang, Libing; Su, Rongxin; Liu, Boshi; Huang, Renliang; Qi, Wei; He, Zhimin

    2015-12-15

    A sensitive and stable electroless-plated gold film for the preparation of an optical fiber surface plasmon resonance (SPR) sensor is presented in this work, together with a facile antibody immobilization method. Gold nanoparticles were uniformly adsorbed onto the surface of an optical fiber forming a film with a thickness of approximately 56.3 nm. The sensor had a high sensitivity with 2054 nm/RIU and 3980 nm/RIU in the refractive index ranges of 1.333-1.359 and 1.359-1.386, respectively. An SPR biosensor was developed based on polydopamine-modified gold film (PDA-Au), which was fabricated by a simple and quick spontaneous polymerization of dopamine (DA) on the gold film. When goat anti-human IgG antibodies were immobilized, the PDA-Au surface had a larger resonant wavelength shift of 66.21 nm compared with the traditional 11-mercaptoundecanoic acid-modified gold film (MUA-Au) surface. In addition, the PDA-Au surface enabled the sensitive and selective determination of human IgG down to a concentration of 2 μg mL(-1) with a high sensitivity of 0.41 nm per μg mL(-1). The PDA-Au surface exhibited an approximately four fold higher sensitivity and an about seven fold lower LOD than the MUA-Au surface to human IgG.

  8. 3D nanoporous gold scaffold supported on graphene paper: Freestanding and flexible electrode with high loading of ultrafine PtCo alloy nanoparticles for electrochemical glucose sensing.

    PubMed

    Zhao, Anshun; Zhang, Zhaowei; Zhang, Penghui; Xiao, Shuang; Wang, Lu; Dong, Yue; Yuan, Hao; Li, Peiwu; Sun, Yimin; Jiang, Xueliang; Xiao, Fei

    2016-09-28

    Recent advances in on-body wearable medical apparatus and implantable devices drive the development of light-weight and bendable electrochemical sensors, which require the design of high-performance flexible electrode system. In this work, we reported a new type of freestanding and flexible electrode based on graphene paper (GP) supported 3D monolithic nanoporous gold (NPG) scaffold (NPG/GP), which was further modified by a layer of highly dense, well dispersed and ultrafine binary PtCo alloy nanoparticles via a facile and effective ultrasonic electrodeposition method. Our results demonstrated that benefited from the synergistic effect of the electrocatalytically active PtCo alloy nanoparticles, the large-active-area and highly conductive 3D NPG scaffold, and the mechanically strong and stable GP electrode substrate, the resultant PtCo alloy nanoparticles modified NPG/GP (PtCo/NPG/GP) exhibited high mechanical strength and good electrochemical sensing performances toward nonenzymatic detection of glucose, including a wide linear range from 35 μM- to 30 mM, a low detection limit of 5 μM (S/N = 3) and a high sensitivity of 7.84 μA cm(-2) mM(-1) as well as good selectivity, long-term stability and reproducibility. The practical application of the proposed PtCo/NPG/GP has also been demonstrated in in vitro detection of blood glucose in real clinic samples. PMID:27619087

  9. Poly(dopamine) coated gold nanocluster functionalized electrochemical immunosensor for brominated flame retardants using multienzyme-labeling carbon hollow nanochains as signal amplifiers.

    PubMed

    Lin, Mouhong; Liu, Yingju; Chen, Xiaofen; Fei, Shidong; Ni, Chunlin; Fang, Yueping; Liu, Chengbin; Cai, Qingyun

    2013-07-15

    An electrochemical, signal amplified immunosensor was developed to detect 3-bromobiphenyl (BBP) by using a bio-inspired polydopamine (PDOP)/gold nanocluster (AuNc) as the sensor platform and multienzyme-labeled carbon hollow nanochains as the signal amplifier. The self-polymerized dopamine membrane on the AuNc-modified indium tin oxide (ITO) electrode were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle and electrochemical measurements. Such PDOP/AuNc platform featured the mild cross-linking reaction with the dense immobilization of BBP-antigens (BBP-Ag). Moreover, by using multiple horseradish peroxidase (HRP) and secondary antibodies (Ab2) modified one-dimensional carbon hollow nanochains (CHNc) as the signal enhancer, it held promise for improving the sensitivity and detection limit of the immunoassay. Based on the competitive immunoassay protocol, this immunosensor showed a linear range from 1 pM to 2 nM for BBP with a detection limit of 0.5 pM. Also, it exhibited high sensitivity, wide linear range, acceptable stability and reproducibility on a promising immobilization platform using a novel signal amplifier, which may extend its application in other environmental monitoring. PMID:23455046

  10. 3D nanoporous gold scaffold supported on graphene paper: Freestanding and flexible electrode with high loading of ultrafine PtCo alloy nanoparticles for electrochemical glucose sensing.

    PubMed

    Zhao, Anshun; Zhang, Zhaowei; Zhang, Penghui; Xiao, Shuang; Wang, Lu; Dong, Yue; Yuan, Hao; Li, Peiwu; Sun, Yimin; Jiang, Xueliang; Xiao, Fei

    2016-09-28

    Recent advances in on-body wearable medical apparatus and implantable devices drive the development of light-weight and bendable electrochemical sensors, which require the design of high-performance flexible electrode system. In this work, we reported a new type of freestanding and flexible electrode based on graphene paper (GP) supported 3D monolithic nanoporous gold (NPG) scaffold (NPG/GP), which was further modified by a layer of highly dense, well dispersed and ultrafine binary PtCo alloy nanoparticles via a facile and effective ultrasonic electrodeposition method. Our results demonstrated that benefited from the synergistic effect of the electrocatalytically active PtCo alloy nanoparticles, the large-active-area and highly conductive 3D NPG scaffold, and the mechanically strong and stable GP electrode substrate, the resultant PtCo alloy nanoparticles modified NPG/GP (PtCo/NPG/GP) exhibited high mechanical strength and good electrochemical sensing performances toward nonenzymatic detection of glucose, including a wide linear range from 35 μM- to 30 mM, a low detection limit of 5 μM (S/N = 3) and a high sensitivity of 7.84 μA cm(-2) mM(-1) as well as good selectivity, long-term stability and reproducibility. The practical application of the proposed PtCo/NPG/GP has also been demonstrated in in vitro detection of blood glucose in real clinic samples.

  11. Size-dependent mobility of gold nano-clusters during growth on chemically modified graphene

    SciTech Connect

    Bell, Gavin R. Dawson, Peter M.; Pandey, Priyanka A.; Wilson, Neil R.; Mulheran, Paul A.

    2014-01-01

    Gold nano-clusters were grown on chemically modified graphene by direct sputter deposition. Transmission electron microscopy of the nano-clusters on these electron-transparent substrates reveals an unusual bimodal island size distribution (ISD). A kinetic Monte Carlo model of growth incorporating a size-dependent cluster mobility rule uniquely reproduces the bimodal ISD, providing strong evidence for the mobility of large clusters during surface growth. The cluster mobility exponent of −5/3 is consistent with cluster motion via one-dimensional diffusion of gold atoms around the edges of the nano-clusters.

  12. Electrochemical Impedance Spectroscopy (bio)sensing through hydrogen evolution reaction induced by gold nanoparticles.

    PubMed

    Mayorga-Martinez, Carmen C; Chamorro-Garcia, Alejandro; Merkoçi, Arben

    2015-05-15

    A new gold nanoparticle (AuNP) based detection strategy using Electrochemical Impedance Spectroscopy (EIS) through hydrogen evolution reaction (HER) is proposed. This EIS-HER method is used as an alternative to the conventional EIS based on [Fe(CN)6](3-/4-) or [Ru(NH3)6](3+/2+) indicators. The proposed method is based on the HER induced by AuNPs. EIS measurements for different amounts of AuNP are registered and the charge transfer resistance (Rct) was found to correlate and be useful for their quantification. Moreover the effect of AuNP size on electrical properties of AuNPs for HER using this sensitive technique has been investigated. Different EIS-HER signals generated in the presence of AuNPs of different sizes (2, 5, 10, 15, 20, and 50 nm) are observed, being the corresponding phenomena extendible to other nanoparticles and related catalytic reactions. This EIS-HER sensing technology is applied to a magneto-immunosandwich assay for the detection of a model protein (IgG) achieving improvements of the analytical performance in terms of a wide linear range (2-500 ng mL(-1)) with a good limit of detection (LOD) of 0.31 ng mL(-1) and high sensitivity. Moreover, with this methodology a reduction of one order of magnitude in the LOD for IgG detection, compared with a chroamperometric technique normally used was achieved. PMID:24953452

  13. An ultrasensitive supersandwich electrochemical DNA biosensor based on gold nanoparticles decorated reduced graphene oxide.

    PubMed

    Wang, Jiao; Shi, Anqi; Fang, Xian; Han, Xiaowei; Zhang, Yuzhong

    2015-01-15

    In this article, a supersandwich-type electrochemical biosensor for sequence-specific DNA detection is described. In design, single-strand DNA labeled with methylene blue (MB) was used as signal probe, and auxiliary probe was designed to hybridize with two different regions of signal probe. The biosensor construction contained three steps: (i) capture DNA labeled with thiol was immobilized on the surface of gold nanoparticles decorated reduced graphene oxide (Au NPs/rGO); (ii) the sandwich structure formation contained "capture-target-signal probe"; and (iii) auxiliary probe was introduced to produce long concatamers containing signal molecule MB. Differential pulse voltammetry (DPV) was used to monitor the DNA hybridization event using peak current changes of MB in phosphate-buffered saline (PBS) containing 1.0M NaClO4. Under optimal conditions, the peak currents of MB were linear with the logarithm of the concentration of target DNA in the range of 0.1μM to 0.1fM with a detection limit of 35aM (signal/noise=3). In addition, this biosensor exhibited good selectivity even for single-base mismatched target DNA detection.

  14. Electrochemical Immunosensors for Interleukin-6. Comparison of Carbon Nanotube Forest and Gold Nanoparticle platforms.

    PubMed

    Munge, Bernard S; Krause, Colleen E; Malhotra, Ruchika; Patel, Vyomesh; Gutkind, J Silvio; Rusling, James F

    2009-01-01

    Electrochemical immunosensors based on single wall nanotube (SWNT) forests and 5 nm glutathione-protected gold nanoparticles (GSH-AuNP) were developed and compared for the measurement of human cancer biomarker interleukin-6 (IL-6) in serum. Detection was based on sandwich immunoassays using multiple (14-16) horseradish peroxidase labels conjugated to a secondary antibody. Performance was optimized by effective blocking of non-specific binding (NSB) of the labels using bovine serum albumin. The GSH-AuNP immunosensor gave a detection limit (DL) of 10 pg mL(-1) IL-6 (500 amol mL(-1)) in 10 muL calf serum, which was 3-fold better than 30 pg mL(-1) found for the SWNT forest immunosensor for the same assay protocol. The GSH-AuNPs platform also gave a much larger linear dynamic range (20-4000 pg mL(-1)) than the SWNT system (40-150 pg mL(-1)), but the SWNTs had 2-fold better sensitivity in the low pg mL(-1) range. PMID:20046945

  15. Electrochemical Gold(III) Sensor with High Sensitivity and Tunable Dynamic Range.

    PubMed

    Wu, Yao; Lai, Rebecca Y

    2016-02-16

    We report the design and fabrication of a sensitive, specific, and selective electrochemical ion (E-ION) sensor for detection of Au(III). The signaling mechanism is based on the interactions between Au(III) and adenine; formation of these complexes rigidifies the methylene blue (MB)-modified oligoadenine probes, resulting in a concentration-dependent reduction in the MB signal. The dynamic range of the sensor can be tuned by simply changing the length of the DNA probe (six (A6) or 12 (A12) adenines). Independent of the probe length, both sensors have demonstrated to be sensitive, with a limits of detection of 50 and 20 nM for the A6 and A12 sensors, respectively. With further optimization, this sensing strategy may offer a promising approach for analyzing Au(III).

  16. Molecularly imprinted electrochemical sensor based on amine group modified graphene covalently linked electrode for 4-nonylphenol detection.

    PubMed

    Chen, Hong-Jun; Zhang, Zhao-Hui; Cai, Rong; Chen, Xing; Liu, Yu-Nan; Rao, Wei; Yao, Shou-Zhuo

    2013-10-15

    In this work, an imprinted electrochemical sensor based on electrochemical reduced graphene covalently modified carbon electrode was developed for the determination of 4-nonylphenol (NP). An amine-terminated functional graphene oxide was covalently modified onto the electrode surface with diazonium salt reactions to improve the stability and reproducibility of the imprinted sensor. The electrochemical properties of each modified electrodes were investigated with differential pulse voltammetry (DPV). The electrochemical characteristic of the imprinted sensor was also investigated using electrochemical impedance spectroscopy (EIS) in detail. The response currents of the imprinted electrode exhibited a linear relationship toward 4-nonylphenol concentration ranging from 1.0 × 10(-11) to 1.0 × 10(-8) gm L(-1) with the detection limit of 3.5 × 10(-12) gm L(-1) (S/N=3). The fabricated electrochemical imprinted sensor was successfully applied to the detection of 4-nonylphenol in rain and lake water samples.

  17. Electrochemical investigation of the voltammetric determination of hydrochlorothiazide using a nickel hydroxide modified nickel electrode.

    PubMed

    Machini, Wesley B S; David-Parra, Diego N; Teixeira, Marcos F S

    2015-12-01

    The preparation and electrochemical characterization of a nickel hydroxide modified nickel electrode as well as its behavior as electrocatalyst toward the oxidation of hydrochlorothiazide (HCTZ) were investigated. The electrochemical behavior of the modified electrode and the electrooxidation of HCTZ were explored using cyclic voltammetry. The voltammetric response of the modified electrode in the detection of HCTZ is based on the electrochemical oxidation of the Ni(II)/Ni(III) and a chemical redox process. The analytical parameters for the electrooxidation of HCTZ by the nickel hydroxide modified nickel electrode were obtained in NaOH solution, in which the linear voltammetric response was in the concentration range from 1.39×10(-5) to 1.67×10(-4)mol L(-1) with a limit of detection of 7.92×10(-6)mol L(-1) and a sensitivity of 0.138 μA Lmmol(-1). Tafel analysis was used to elucidate the kinetics and mechanism of HCTZ oxidation by the modified electrode.

  18. An electrochemical fungicide pyrimethanil sensor based on carbon nanotubes/ionic-liquid construction modified electrode.

    PubMed

    Yang, Jichun; Wang, Qiong; Zhang, Minhui; Zhang, Shuming; Zhang, Lei

    2015-11-15

    In this study, a simple, rapid, sensitive and environmentally friendly electroanalytical detection method for pyrimethanil (PMT) was developed, which was based on multi-walled carbon nanotubes (MWCNTs) and ionic liquids (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) modified glassy carbon electrode (GCE). MWCNTs-IL modified electrode significantly enhanced the oxidation peak current of PMT by combining the excellent electrochemical properties of MWCNTs and IL, suggesting that the modified electrode can remarkably improve the sensitivity of PMT detection. Under the optimum conditions, this electrochemical sensor exhibited a linear concentration range for PMT of 1.0 × 10(-7)-1.0 × 10(-4) mol L(-1) and the detection limit was 1.6 × 10(-8) mol L(-1) (S/N = 3). The fabricated electrode showed good reproducibility, stability and anti-interference, and also it was successfully employed to detect PMT in real samples.

  19. An electrochemical nanobiosensor for plasma miRNA-155, based on graphene oxide and gold nanorod, for early detection of breast cancer.

    PubMed

    Azimzadeh, Mostafa; Rahaie, Mahdi; Nasirizadeh, Navid; Ashtari, Khadijeh; Naderi-Manesh, Hossein

    2016-03-15

    Circulating miRNAs are emerging as novel reliable biomarkers for early detection of cancer diseases. Through combining the advantages of electrochemical methods and nanomaterials with the selectivity of the oligo-hybridization-based biosensors, a novel electrochemical nanobiosensor for plasma miR-155 detection have demonstrated here, based on thiolated probe-functionalized gold nanorods (GNRs) decorated on the graphene oxide (GO) sheet on the surface of the glassy carbon electrode (GCE). The reduction signals of a novel intercalating label Oracet Blue (OB), were measured by differential pulse voltammetry (DPV) method. The transmission electron microscope (TEM) imaging, UV-vis spectrophotometry, cyclic voltammetry (CV), field emission scanning electron microscope (FE-SEM) imaging and energy dispersive spectroscopy (EDS) were proved the right synthesis of the GNRs and correct assembly of the modified electrode. The electrochemical signal had a linear relationship with the concentration of the target miRNA ranging from 2.0 fM to 8.0 pM, and the detection limit was 0.6 fM. Furthermore, the nanobiosensor showed high Specificity, and was able to discriminate sharply between complementary target miRNA, single-, three-base mismatch, and non-complementary miRNA. Alongside the outstanding sensitivity and selectivity, this nanobiosensor had great storage ability, reproducibility, and showed a decent response in the real sample analysis with plasma. In conclusion, the proposed electrochemical nanobiosensor could clinically be used in the early detection of the breast cancer, by direct detection of the plasma miR-155 in real clinical samples, without a need for sample preparation, RNA extraction and/or amplification.

  20. Increased electrocatalyzed performance through hairpin oligonucleotide aptamer-functionalized gold nanorods labels and graphene-streptavidin nanomatrix: Highly selective and sensitive electrochemical biosensor of carcinoembryonic antigen.

    PubMed

    Wen, Wei; Huang, Jing-Yi; Bao, Ting; Zhou, Jun; Xia, Hong-Xing; Zhang, Xiu-Hua; Wang, Sheng-Fu; Zhao, Yuan-Di

    2016-09-15

    We report a triplex signal amplification strategy for sensitive biosensing of cancer biomarker by taking advantage of hairpin-shaped oligonucleotide-functionalized gold nanorods (HO-GNRs), graphene and the avidin-biotin reation. The strategy expands electrochemical detection of carcinoembryonic antigen (CEA) by using an aptamer as biosensor's recognition element and HO-GNRs as signal enhancer. To construct this biosensor, the GNR was used as a carrier of horseradish peroxidase (HRP) and HO aptamer with a biotin at the 3'-end and a thiol at the 5'-end, which amplified the electrochemical response because of a large molar ratio of HRP to HO. In the presence of target CEA, the binding reactions of CEA with the loop portions of the HOs caused HOs' loop-stem structure opened and exposed the biotins, and then HRP-GNRs-HO conjugates were captured on graphene and streptavidin modified electrodes via the reaction between the exposed biotins and preimmobilized streptavidins. The accumulation of HRP effectively catalyzed the hydrogen peroxide-mediated oxidation of o-phenylenediamine to generate an electrochemical reduction current for CEA detection. Under optimal conditions, the electrochemical biosensor exhibited a wide dynamic range of 5pgmL(-1) and 50ngmL(-1) toward CEA standards with a low detection limit of 1.5pgmL(-1) (signal-to-noise ratio of 3). The proposed biosensor accurately detected CEA concentration in 8 human serum samples from patients with lung diseases, showing excellent correlations with standard chemiluminescence immunoassay. Furthermore, these results of target DNA detection made it abundantly clear that the proposed strategy can also be extended for detection of other relative biomarkers using different functional DNA structures, which shows great prospects in single-nucleotide polymorphisms analysis, biomedical sensing and application for accurate clinical diseases diagnostic.

  1. Increased electrocatalyzed performance through hairpin oligonucleotide aptamer-functionalized gold nanorods labels and graphene-streptavidin nanomatrix: Highly selective and sensitive electrochemical biosensor of carcinoembryonic antigen.

    PubMed

    Wen, Wei; Huang, Jing-Yi; Bao, Ting; Zhou, Jun; Xia, Hong-Xing; Zhang, Xiu-Hua; Wang, Sheng-Fu; Zhao, Yuan-Di

    2016-09-15

    We report a triplex signal amplification strategy for sensitive biosensing of cancer biomarker by taking advantage of hairpin-shaped oligonucleotide-functionalized gold nanorods (HO-GNRs), graphene and the avidin-biotin reation. The strategy expands electrochemical detection of carcinoembryonic antigen (CEA) by using an aptamer as biosensor's recognition element and HO-GNRs as signal enhancer. To construct this biosensor, the GNR was used as a carrier of horseradish peroxidase (HRP) and HO aptamer with a biotin at the 3'-end and a thiol at the 5'-end, which amplified the electrochemical response because of a large molar ratio of HRP to HO. In the presence of target CEA, the binding reactions of CEA with the loop portions of the HOs caused HOs' loop-stem structure opened and exposed the biotins, and then HRP-GNRs-HO conjugates were captured on graphene and streptavidin modified electrodes via the reaction between the exposed biotins and preimmobilized streptavidins. The accumulation of HRP effectively catalyzed the hydrogen peroxide-mediated oxidation of o-phenylenediamine to generate an electrochemical reduction current for CEA detection. Under optimal conditions, the electrochemical biosensor exhibited a wide dynamic range of 5pgmL(-1) and 50ngmL(-1) toward CEA standards with a low detection limit of 1.5pgmL(-1) (signal-to-noise ratio of 3). The proposed biosensor accurately detected CEA concentration in 8 human serum samples from patients with lung diseases, showing excellent correlations with standard chemiluminescence immunoassay. Furthermore, these results of target DNA detection made it abundantly clear that the proposed strategy can also be extended for detection of other relative biomarkers using different functional DNA structures, which shows great prospects in single-nucleotide polymorphisms analysis, biomedical sensing and application for accurate clinical diseases diagnostic. PMID:27111123

  2. Highly sensitive determination of hydroxylamine using fused gold nanoparticles immobilized on sol-gel film modified gold electrode.

    PubMed

    Kannan, P; John, S Abraham

    2010-03-24

    We are reporting the highly sensitive determination of hydroxylamine (HA) using 2-mercapto-4-methyl-5-thiazoleacetic acid (TAA) capped fused spherical gold nanoparticles (AuNPs) modified Au electrode. The fused TAA-AuNPs were immobilized on (3-mercaptopropyl)-trimethoxysilane (MPTS) sol-gel film, which was pre-assembled on Au electrode. The immobilization of fused TAA-AuNPs on MPTS sol-gel film was confirmed by UV-vis absorption spectroscopy and atomic force microscopy (AFM). The AFM image showed that the AuNPs retained the fused spherical morphology after immobilized on sol-gel film. The fused TAA-AuNPs on MPTS modified Au electrode were used for the determination of HA in phosphate buffer (PB) solution (pH=7.2). When compared to bare Au electrode, the fused AuNPs modified electrode not only shifted the oxidation potential of HA towards less positive potential but also enhanced its oxidation peak current. Further, the oxidation of HA was highly stable at fused AuNPs modified electrode. Using amperometric method, determination of 17.5 nM HA was achieved for the first time. Further, the current response of HA increases linearly while increasing its concentration from 17.5 nM to 22 mM and a detection limit was found to be 0.39 nM (S/N=3). The present modified electrode was also successfully used for the determination of 17.5 nM HA in the presence of 200-fold excess of common interferents such as urea, NO(2)(-), NH(4)(+), oxalate, Mn(2+), Na(+), K(+), Mg(2+), Ca(2+), Ba(2+) and Cu(2+). The practical application of the present modified electrode was demonstrated by measuring the concentration of HA in ground water samples.

  3. Direct electrochemistry of lactate dehydrogenase immobilized on silica sol-gel modified gold electrode and its application.

    PubMed

    Di, Junwei; Cheng, Jiongjia; Xu, Quan; Zheng, Huie; Zhuang, Jingyue; Sun, Yongbo; Wang, Keyu; Mo, Xiangyin; Bi, Shuping

    2007-12-15

    The direct electrochemistry of lactate dehydrogenase (LDH) immobilized in silica sol-gel film on gold electrode was investigated, and an obvious cathodic peak at about -200 mV (versus SCE) was found for the first time. The LDH-modified electrode showed a surface controlled irreversible electrode process involving a one electron transfer reaction with the charge-transfer coefficient (alpha) of 0.79 and the apparent heterogeneous electron transfer rate constant (K(s)) of 3.2 s(-1). The activated voltammetric response and decreased charge-transfer resistance of Ru(NH(3))(6)(2+/3+) on the LDH-modified electrode provided further evidence. The surface morphologies of silica sol-gel and the LDH embedded in silica sol-gel film were characterized by SEM. A potential application of the LDH-modified electrode as a biosensor for determination of lactic acid was also investigated. The calibration range of lactic acid was from 2.0 x 10(-6) to 3.0 x 10(-5) mol L(-1) and the detection limit was 8.0 x 10(-7) mol L(-1) at a signal-to-noise ratio of 3. Finally, the effect of environmental pollutant resorcinol on the direct electrochemical behavior of LDH was studied. The experimental results of voltammetry indicated that the conformation of LDH molecule was altered by the interaction between LDH and resorcinol. The modified electrode can be applied as a biomarker to study the pollution effect in the environment.

  4. Gold

    USGS Publications Warehouse

    Kirkemo, Harold; Newman, William L.; Ashley, Roger P.

    1998-01-01

    Through the ages, men and women have cherished gold, and many have had a compelling desire to amass great quantities of it -- so compelling a desire, in fact, that the frantic need to seek and hoard gold has been aptly named "gold fever." Gold was among the first metals to be mined because it commonly occurs in its native form -- that is, not combined with other elements -- because it is beautiful and imperishable, and because exquisite objects can be made from it.

  5. Effects on electrochemical performances for host material caused by structure change of modifying material.

    PubMed

    Zhang, Yantao; Zhou, Enlou; Song, Dawei; Shi, Xixi; Wang, Xiaoqing; Guo, Jian; Zhang, Lianqi

    2014-09-01

    High ionic conductive lithium niobium oxides were selected as the modifying material to investigate the effects on the electrochemical performances for host material LiNi1/3Co1/3Mn1/3O2 caused by the structure change of the modifying material at various calcination temperatures and modifying amounts. X-ray diffraction (XRD) studies revealed that the structure of the modifying material was single LiNbO3 phase after being calcined at 500 °C and changed to LiNbO3-Li3NbO4 mixture phases at 600 and 700 °C, and further changed to single Li3NbO4 phase at 800 °C. Electrochemical tests displayed that both LiNbO3 and Li3NbO4 phases of modifying material could contribute to the improvement of the cycle performances for the host material, but the improvement degree of Li3NbO4 phase was more evident. The cycle performances and high rate performances of the modified host material (calcined at 700 °C) electrodes were improved with the right modifying amount.

  6. Functionalization of organically modified silica with gold nanoparticles in the presence of lignosulfonate.

    PubMed

    Konował, Emilia; Modrzejewska-Sikorska, Anna; Motylenko, Mykhailo; Klapiszewski, Łukasz; Wysokowski, Marcin; Bazhenov, Vasilii V; Rafaja, David; Ehrlich, Hermann; Milczarek, Grzegorz; Jesionowski, Teofil

    2016-04-01

    It is shown that lignosulfonate (LS) can be used as an effective reducing agent for gold ions and simultaneously as a stabilizing agent for gold nanoparticles (AuNPs). When organically modified silica is introduced to the reaction mixture, most of the AuNPs grow on the surface of the silica due to hydrophobic interactions between LS and organic layers covering the solid particles. It was also found that the structure of the organic layer is crucial for the effective deposition of gold nanoparticles onto silica spheres in terms of particle size and gold content in the final SiO2-LS-AuNPs composites. Due to the hydrophobicity of the modified silica it was necessary to carry out the modification in mixed organic/aqueous solvent. The polarity of the organic co-solvent was found to have an effect on the size of the deposited Au-NPs and their quantity. The physical appearance of the obtained hybrids was analyzed by colorimetry, and their structure and composition were evaluated using transmission electron microscopy (TEM). Additionally dispersive and thermal properties were examined by dynamic light scattering (DLS) and thermogravimetry (TG), respectively. The obtained multifunctional hybrid materials exhibits remarkable catalytic activity for the reduction of C.I. Basic Blue 9 (Methylene Blue) by borohydride.

  7. Functionalization of organically modified silica with gold nanoparticles in the presence of lignosulfonate.

    PubMed

    Konował, Emilia; Modrzejewska-Sikorska, Anna; Motylenko, Mykhailo; Klapiszewski, Łukasz; Wysokowski, Marcin; Bazhenov, Vasilii V; Rafaja, David; Ehrlich, Hermann; Milczarek, Grzegorz; Jesionowski, Teofil

    2016-04-01

    It is shown that lignosulfonate (LS) can be used as an effective reducing agent for gold ions and simultaneously as a stabilizing agent for gold nanoparticles (AuNPs). When organically modified silica is introduced to the reaction mixture, most of the AuNPs grow on the surface of the silica due to hydrophobic interactions between LS and organic layers covering the solid particles. It was also found that the structure of the organic layer is crucial for the effective deposition of gold nanoparticles onto silica spheres in terms of particle size and gold content in the final SiO2-LS-AuNPs composites. Due to the hydrophobicity of the modified silica it was necessary to carry out the modification in mixed organic/aqueous solvent. The polarity of the organic co-solvent was found to have an effect on the size of the deposited Au-NPs and their quantity. The physical appearance of the obtained hybrids was analyzed by colorimetry, and their structure and composition were evaluated using transmission electron microscopy (TEM). Additionally dispersive and thermal properties were examined by dynamic light scattering (DLS) and thermogravimetry (TG), respectively. The obtained multifunctional hybrid materials exhibits remarkable catalytic activity for the reduction of C.I. Basic Blue 9 (Methylene Blue) by borohydride. PMID:26724689

  8. Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium.

    PubMed

    Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

    2016-02-01

    A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03-200μmolL(-1). The lower detection limits were found to be 0.02μmolL(-1). The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. PMID:26652361

  9. Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium.

    PubMed

    Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

    2016-02-01

    A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03-200μmolL(-1). The lower detection limits were found to be 0.02μmolL(-1). The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility.

  10. Highly Efficient Electrochemical Hydrogen Evolution Reaction at Insulating Boron Nitride Nanosheet on Inert Gold Substrate.

    PubMed

    Uosaki, Kohei; Elumalai, Ganesan; Dinh, Hung Cuong; Lyalin, Andrey; Taketsugu, Tetsuya; Noguchi, Hidenori

    2016-01-01

    It is demonstrated that electrochemical hydrogen evolution reaction (HER) proceeds very efficiently at Au electrode, an inert substrate for HER, modified with BNNS, an insulator. This combination has been reported to be an efficient electrocatalyst for oxygen reduction reaction. Higher efficiency is achieved by using the size controlled BNNS (<1 μm) for the modification and the highest efficiency is achieved at Au electrode modified with the smallest BNNS (0.1-0.22 μm) used in this study where overpotentials are only 30 mV and 40 mV larger than those at Pt electrode, which is known to be the best electrode for HER, at 5 mAcm(-2) and at 15 mAcm(-2), respectively. Theoretical evaluation suggests that some of edge atoms provide energetically favored sites for adsorbed hydrogen, i.e., the intermediate state of HER. This study opens a new route to develop HER electrocatalysts. PMID:27558958

  11. Highly Efficient Electrochemical Hydrogen Evolution Reaction at Insulating Boron Nitride Nanosheet on Inert Gold Substrate

    PubMed Central

    Uosaki, Kohei; Elumalai, Ganesan; Dinh, Hung Cuong; Lyalin, Andrey; Taketsugu, Tetsuya; Noguchi, Hidenori

    2016-01-01

    It is demonstrated that electrochemical hydrogen evolution reaction (HER) proceeds very efficiently at Au electrode, an inert substrate for HER, modified with BNNS, an insulator. This combination has been reported to be an efficient electrocatalyst for oxygen reduction reaction. Higher efficiency is achieved by using the size controlled BNNS (<1 μm) for the modification and the highest efficiency is achieved at Au electrode modified with the smallest BNNS (0.1–0.22 μm) used in this study where overpotentials are only 30 mV and 40 mV larger than those at Pt electrode, which is known to be the best electrode for HER, at 5 mAcm−2 and at 15 mAcm−2, respectively. Theoretical evaluation suggests that some of edge atoms provide energetically favored sites for adsorbed hydrogen, i.e., the intermediate state of HER. This study opens a new route to develop HER electrocatalysts. PMID:27558958

  12. Highly Efficient Electrochemical Hydrogen Evolution Reaction at Insulating Boron Nitride Nanosheet on Inert Gold Substrate

    NASA Astrophysics Data System (ADS)

    Uosaki, Kohei; Elumalai, Ganesan; Dinh, Hung Cuong; Lyalin, Andrey; Taketsugu, Tetsuya; Noguchi, Hidenori

    2016-08-01

    It is demonstrated that electrochemical hydrogen evolution reaction (HER) proceeds very efficiently at Au electrode, an inert substrate for HER, modified with BNNS, an insulator. This combination has been reported to be an efficient electrocatalyst for oxygen reduction reaction. Higher efficiency is achieved by using the size controlled BNNS (<1 μm) for the modification and the highest efficiency is achieved at Au electrode modified with the smallest BNNS (0.1–0.22 μm) used in this study where overpotentials are only 30 mV and 40 mV larger than those at Pt electrode, which is known to be the best electrode for HER, at 5 mAcm‑2 and at 15 mAcm‑2, respectively. Theoretical evaluation suggests that some of edge atoms provide energetically favored sites for adsorbed hydrogen, i.e., the intermediate state of HER. This study opens a new route to develop HER electrocatalysts.

  13. Surface Analysis of Gold Nanoparticles Functionalized with Thiol-Modified Glucose SAMs for Biosensor Applications

    PubMed Central

    Spampinato, Valentina; Parracino, Maria Antonietta; La Spina, Rita; Rossi, Francois; Ceccone, Giacomo

    2016-01-01

    In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Principal Component Analysis (PCA) and X-ray Photoelectron Spectroscopy (XPS) have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP). The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules. Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behavior of the glucose-modified particles in the presence of the maltose binding protein. PMID:26973830

  14. Electrical resistivity of nanoporous gold modified with thiol self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Hakamada, Masataka; Kato, Naoki; Mabuchi, Mamoru

    2016-11-01

    The electrical resistivity of nanoporous gold (NPG) modified with thiol self-assembled monolayers (SAMs) has been measured at 298 K using a four-probe method. We found that the adsorption of thiol SAMs increases the electrical resistivity of NPG by up to 22.2%. Dependence of the electrical resistivity on the atmosphere (air or water) was also observed in SAMs-modified NPG, suggesting that the electronic states of the tail groups affect the electrons of the binding sulfur and adjacent surface gold atoms. The present results suggest that adsorption of thiol molecules can influence the behavior of the conducting electrons in NPG and that modification of NPG with SAMs may be useful for environmental sensing.

  15. Comparison of the peroxidase-like activity of unmodified, amino-modified, and citrate-capped gold nanoparticles.

    PubMed

    Wang, Sheng; Chen, Wei; Liu, Ai-Lin; Hong, Lei; Deng, Hao-Hua; Lin, Xin-Hua

    2012-04-10

    The origin of the peroxidase-like activity of gold nanoparticles and the impact of surface modification are studied. Furthermore, some influencing factors, such as fabrication process, redox property of the modifier, and charge property of the substrate, are investigated. Compared to amino-modified or citrate-capped gold nanoparticles, unmodified gold nanoparticles show significantly higher catalytic activity toward peroxidase substrates, that is, the superficial gold atoms are a contributing factor to the observed peroxidase-like activity. The different catalytic activities of amino-modified and citrate-capped gold nanoparticles toward 3,3',5,5'-tetramethylbenzidine (TMB) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) show that the charge characteristics of the nanoparticles and the substrate also play an important role in the catalytic reactions. PMID:22383315

  16. 4-Fluoro-3-nitrophenyl grafted gold electrode based platform for label free electrochemical detection of interleukin-2 protein.

    PubMed

    Arya, Sunil K; Park, Mi Kyoung

    2014-11-15

    A new platform based on 4-Fluoro-3-nitrophenyl (FNP) grafted gold disk electrode prepared via electrochemical reduction of 4-fluoro-3-nitrobenzene diazonium ion has been developed and utilized for biosensor fabrication. Anti-interleukin-2 (anti-IL2) antibody has been covalently immobilized onto FNP/Au surface and utilized for label free electrochemical impedance based detection of cytokine IL2. FNP acts as a bridge (cross-linker) between gold surface and anti-IL2, where fluoro group of FNP undergoes nucleophilic substitution by amino group of biomolecule and results in its covalent immobilization. The immobilization process and fabricated electrode have been characterized using contact angle (CA) measurements, cyclic voltammetry (CV) and electrochemical impedance (EIS) technique. CV studies show that FNP grafted surface provides conductive surface for anti-IL2 immobilization. The EIS response of studies as a function of IL2 concentrations exhibits a detection in linear range from 1 pg ml(-1) to 10 ng ml(-1) with minimum detectable concentration of 1 pg ml(-1). The electrode has been found to be selective against other cytokine molecules.

  17. Towards the use of protein A-tagged gold nanoparticles for signal amplification of electrochemical immunosensors in virus detection

    NASA Astrophysics Data System (ADS)

    Tran, Quang Huy; Mai, Anh Tuan; Thuy Nguyen, Thanh; Chung Pham, Van; Hanh Nguyen, Thi Hong

    2012-06-01

    In this paper we represent a study on the potential use of protein A-tagged gold nanoparticles applied for signal amplification of electrochemical immunosensors. Gold nanoparticles (GNPs) were synthesized by the chemical reduction of tetrachloroauric (III) acid trihydrate using sodium ascorbate, and then tagged with protein A (PrA) via ultracentrifugation. UV-Vis spectroscopy and transmission electron microscopy were used to verify the characteristics of formed GNPs/PrA complex. The analyzed results indicate that GNPs were found spherically, homogeneously, and with an average diameter of about 10 nm. Immunoelectron microscopy was then used to investigate the bioactivity of the GNPs/PrA complex in solution by the effective binding of GNPs to viral particles. Scanning electron and fluorescence microscopies were also used to investigate the distribution and the bioactivity of the GNPs/PrA complex on the surface of the interdigitated sensor. Consequently, this study provided some assumptions of the potential application of protein A-tagged gold nanoparticles for signal amplification of electrochemical immunosensors in virus detection from clinical samples.

  18. Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: a review.

    PubMed

    Barsan, Madalina M; Ghica, M Emilia; Brett, Christopher M A

    2015-06-30

    The aim of this review is to present the contributions to the development of electrochemical sensors and biosensors based on polyphenazine or polytriphenylmethane redox polymers together with carbon nanotubes (CNT) during recent years. Phenazine polymers have been widely used in analytical applications due to their inherent charge transport properties and electrocatalytic effects. At the same time, since the first report on a CNT-based sensor, their application in the electroanalytical chemistry field has demonstrated that the unique structure and properties of CNT are ideal for the design of electrochemical (bio)sensors. We describe here that the specific combination of phenazine/triphenylmethane polymers with CNT leads to an improved performance of the resulting sensing devices, because of their complementary electrical, electrochemical and mechanical properties, and also due to synergistic effects. The preparation of polymer/CNT modified electrodes will be presented together with their electrochemical and surface characterization, with emphasis on the contribution of each component on the overall properties of the modified electrodes. Their importance in analytical chemistry is demonstrated by the numerous applications based on polymer/CNT-driven electrocatalytic effects, and their analytical performance as (bio) sensors is discussed.

  19. Electrochemical sensing of bisphenol using a multilayer graphene nanobelt modified photolithography patterned platinum electrode.

    PubMed

    Kannan, Padmanathan Karthick; Hu, Chunxiao; Morgan, Hywel; Moshkalev, Stanislav A; Rout, Chandra Sekhar

    2016-09-16

    An electrochemical sensor has been developed for the detection of Bisphenol-A (BPA) using photolithographically patterned platinum electrodes modified with multilayer graphene nanobelts (GNB). Compared to bare electrodes, the GNB modified electrode exhibited enhanced BPA oxidation current, due to the high effective surface area and high adsorption capacity of the GNB. The sensor showed a linear response over the concentration range from 0.5 μM-9 μM with a very low limit of detection = 37.33 nM. In addition, the sensor showed very good stability and reproducibility with good specificity, demonstrating that GNB is potentially a new material for the development of a practical BPA electrochemical sensor with application in both industrial and plastic industries.

  20. Electrochemical sensing of bisphenol using a multilayer graphene nanobelt modified photolithography patterned platinum electrode

    NASA Astrophysics Data System (ADS)

    Karthick Kannan, Padmanathan; Hu, Chunxiao; Morgan, Hywel; Moshkalev, Stanislav A.; Sekhar Rout, Chandra

    2016-09-01

    An electrochemical sensor has been developed for the detection of Bisphenol-A (BPA) using photolithographically patterned platinum electrodes modified with multilayer graphene nanobelts (GNB). Compared to bare electrodes, the GNB modified electrode exhibited enhanced BPA oxidation current, due to the high effective surface area and high adsorption capacity of the GNB. The sensor showed a linear response over the concentration range from 0.5 μM-9 μM with a very low limit of detection = 37.33 nM. In addition, the sensor showed very good stability and reproducibility with good specificity, demonstrating that GNB is potentially a new material for the development of a practical BPA electrochemical sensor with application in both industrial and plastic industries.

  1. Electrochemical sensing of bisphenol using a multilayer graphene nanobelt modified photolithography patterned platinum electrode.

    PubMed

    Kannan, Padmanathan Karthick; Hu, Chunxiao; Morgan, Hywel; Moshkalev, Stanislav A; Rout, Chandra Sekhar

    2016-09-16

    An electrochemical sensor has been developed for the detection of Bisphenol-A (BPA) using photolithographically patterned platinum electrodes modified with multilayer graphene nanobelts (GNB). Compared to bare electrodes, the GNB modified electrode exhibited enhanced BPA oxidation current, due to the high effective surface area and high adsorption capacity of the GNB. The sensor showed a linear response over the concentration range from 0.5 μM-9 μM with a very low limit of detection = 37.33 nM. In addition, the sensor showed very good stability and reproducibility with good specificity, demonstrating that GNB is potentially a new material for the development of a practical BPA electrochemical sensor with application in both industrial and plastic industries. PMID:27504686

  2. Electrochemical sensing of bisphenol using a multilayer graphene nanobelt modified photolithography patterned platinum electrode

    NASA Astrophysics Data System (ADS)

    Karthick Kannan, Padmanathan; Hu, Chunxiao; Morgan, Hywel; Moshkalev, Stanislav A.; Sekhar Rout, Chandra

    2016-09-01

    An electrochemical sensor has been developed for the detection of Bisphenol-A (BPA) using photolithographically patterned platinum electrodes modified with multilayer graphene nanobelts (GNB). Compared to bare electrodes, the GNB modified electrode exhibited enhanced BPA oxidation current, due to the high effective surface area and high adsorption capacity of the GNB. The sensor showed a linear response over the concentration range from 0.5 μM–9 μM with a very low limit of detection = 37.33 nM. In addition, the sensor showed very good stability and reproducibility with good specificity, demonstrating that GNB is potentially a new material for the development of a practical BPA electrochemical sensor with application in both industrial and plastic industries.

  3. Calculation of Electrochemical Reorganization Energies for Redox Molecules at Self-Assembled Monolayer Modified Electrodes.

    PubMed

    Ghosh, Soumya; Hammes-Schiffer, Sharon

    2015-01-01

    Electrochemical electron transfer reactions play an important role in energy conversion processes with many technological applications. Electrodes modified by self-assembled monolayers (SAMs) exhibit reduced double layer effects and are used in molecular electronics. An important quantity for calculating the electron transfer rate constant is the reorganization energy, which is associated with changes in the solute geometry and the environment. In this Letter, an approach for calculating the electrochemical reorganization energy for a redox molecule attached to or near a SAM modified electrode is presented. This integral equations formalism polarizable continuum model (IEF-PCM) approach accounts for the detailed electronic structure of the molecule, as well as the contributions from the electrode, SAM, and electronic and inertial solvent responses. The calculated total reorganization energies are in good agreement with experimental data for a series of metal complexes in aqueous solution. This approach will be useful for calculating electron transfer rate constants for molecular electrocatalysts. PMID:26263083

  4. Fabrication of an Electrochemical Sensor Based on Gold Nanoparticles/Carbon Nanotubes as Nanocomposite Materials: Determination of Myricetin in Some Drinks

    PubMed Central

    Hajian, Reza; Yusof, Nor Azah; Faragi, Tayebe; Shams, Nafiseh

    2014-01-01

    In this paper, the electrochemical behavior of myricetin on a gold nanoparticle/ethylenediamine/multi-walled carbon-nanotube modified glassy carbon electrode (AuNPs/en/MWCNTs/GCE) has been investigated. Myricetin effectively accumulated on the AuNPs/en/MWCNTs/GCE and caused a pair of irreversible redox peaks at around 0.408 V and 0.191 V (vs. Ag/AgCl) in 0.1 mol L−1 phosphate buffer solution (pH 3.5) for oxidation and reduction reactions respectively. The heights of the redox peaks were significantly higher on AuNPs/en/MWNTs/GCE compare with MWCNTs/GC and there was no peak on bare GC. The electron-transfer reaction for myricetin on the surface of electrochemical sensor was controlled by adsorption. Some parameters including pH, accumulation potential, accumulation time and scan rate have been optimized. Under the optimum conditions, anodic peak current was proportional to myricetin concentration in the dynamic range of 5.0×10−8 to 4.0×10−5 mol L−1 with the detection limit of 1.2×10−8 mol L−1. The proposed method was successfully used for the determination of myricetin content in tea and fruit juices. PMID:24809346

  5. Plasma-Modified, Epitaxial Fabricated Graphene on SiC for the Electrochemical Detection of TNT

    PubMed Central

    Trammell, Scott A.; Hernández, Sandra C.; Myers-Ward, Rachael L.; Zabetakis, Daniel; Stenger, David A.; Gaskill, D. Kurt; Walton, Scott G.

    2016-01-01

    Using square wave voltammetry, we show an increase in the electrochemical detection of trinitrotoluene (TNT) with a working electrode constructed from plasma modified graphene on a SiC surface vs. unmodified graphene. The graphene surface was chemically modified using electron beam generated plasmas produced in oxygen or nitrogen containing backgrounds to introduce oxygen or nitrogen moieties. The use of this chemical modification route enabled enhancement of the electrochemical signal for TNT, with the oxygen treatment showing a more pronounced detection than the nitrogen treatment. For graphene modified with oxygen, the electrochemical response to TNT can be fit to a two-site Langmuir isotherm suggesting different sites on the graphene surface with different affinities for TNT. We estimate a limit of detection for TNT equal to 20 ppb based on the analytical standard S/N ratio of 3. In addition, this approach to sensor fabrication is inherently a high-throughput, high-volume process amenable to industrial applications. High quality epitaxial graphene is easily grown over large area SiC substrates, while plasma processing is a rapid approach to large area substrate processing. This combination facilitates low cost, mass production of sensors. PMID:27529251

  6. Plasma-Modified, Epitaxial Fabricated Graphene on SiC for the Electrochemical Detection of TNT.

    PubMed

    Trammell, Scott A; Hernández, Sandra C; Myers-Ward, Rachael L; Zabetakis, Daniel; Stenger, David A; Gaskill, D Kurt; Walton, Scott G

    2016-01-01

    Using square wave voltammetry, we show an increase in the electrochemical detection of trinitrotoluene (TNT) with a working electrode constructed from plasma modified graphene on a SiC surface vs. unmodified graphene. The graphene surface was chemically modified using electron beam generated plasmas produced in oxygen or nitrogen containing backgrounds to introduce oxygen or nitrogen moieties. The use of this chemical modification route enabled enhancement of the electrochemical signal for TNT, with the oxygen treatment showing a more pronounced detection than the nitrogen treatment. For graphene modified with oxygen, the electrochemical response to TNT can be fit to a two-site Langmuir isotherm suggesting different sites on the graphene surface with different affinities for TNT. We estimate a limit of detection for TNT equal to 20 ppb based on the analytical standard S/N ratio of 3. In addition, this approach to sensor fabrication is inherently a high-throughput, high-volume process amenable to industrial applications. High quality epitaxial graphene is easily grown over large area SiC substrates, while plasma processing is a rapid approach to large area substrate processing. This combination facilitates low cost, mass production of sensors. PMID:27529251

  7. Amplified electrochemical detection of protein kinase activity based on gold nanoparticles/multi-walled carbon nanotubes nanohybrids.

    PubMed

    Liu, Jinquan; He, Xiaoxiao; Wang, Kemin; Wang, Yonghong; Yan, Genping; Mao, Yinfei

    2014-11-01

    A sensitive and simple electrochemical strategy has been developed for assay of protein kinase A (PKA) activity and inhibition using gold nanoparticles/multi-walled carbon nanotubes (AuNPs/MWNTs) nanohybrids. Key features of this assay included intrinsic peroxidase-like activity of positively-charged gold nanoparticles (+AuNPs) and signal transduction and amplification of multi-walled carbon nanotubes (MWNTs). In this assay, an N-terminally cysteine-containing peptide was self-assembled onto the gold electrode via Au-S bonding and used as substrate for PKA, and adenosine-5'-(γ-thio)-triphosphate was used as co-substrate. Upon thiophosphorylation in the presence of PKA, the AuNPs/MWNTs nanohybrids would be fixed onto the peptides via Au-S bond. The conjugated AuNPs/MWNTs nanohybrids could catalyze the 3, 3', 5, 5'-Tetramethylbenzidine (TMB) oxidation by H2O2 to form TMB oxidation product, which was reduced at the electrode surface to generate an electrochemical current. It was eT on state. The current signal intensity is proportional to the activity of PKA. Here, the presence of MWNTs not only increased the surface area for accumulation of +AuNPs but also could promote electron-transfer reaction. It was found that the electrochemical strategy can be employed to assay PKA activity with a low detection limit of 0.09 U/mL. The linear range of the assay for PKA enzymatic unit/ml was 0.1-1 U/mL. Furthermore, the interferences experiments of T4 polynucleotide kinase (T4 PNK) and Casein kinase II (CK2), and inhibition of PKA, have also been studied by using this strategy. The developed method would provide a diversified platform for kinase activity and inhibition monitoring.

  8. Photocatalytic Destruction of Tetracycline Hydrochloride on the Surface of Titanium Dioxide Films Modified by Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Linnik, O. P.; Zhukovskiy, M. A.; Starukh, G. N.; Smirnova, N. P.; Gaponenko, N. V.; Asharif, A. M.; Khoroshko, L. S.; Borisenko, V. E.

    2015-01-01

    Films of titania (TiO2) and titania modified with gold nanoparticles (TiO2:Au) were synthesized by a sol-gel method on substrates of glass, aluminum, and aluminum with a layer of nanotextured aluminum or porous anodic alumina. The photocatalytic activity of the samples was investigated in an aqueous solution of the antibiotic tetracycline hydrochloride (TC). TC decomposition was observed in the presence of all samples as a reduction of the solution optical density in the range below 500 nm. Titania was in the crystalline anatase phase with incorporated spherical gold nanoparticles primarily of sizes 1-10 nm after heat treatment at 400°C. Modification of TiO2 films with gold nanoparticles on glass or aluminum substrates did not increase the photocatalytic activity of the samples. It was found that complexes of TC with Al3+ in solution formed only in the presence of gold nanoparticles in the film either in the dark or with UV irradiation.

  9. Targeting helicase-dependent amplification products with an electrochemical genosensor for reliable and sensitive screening of genetically modified organisms.

    PubMed

    Moura-Melo, Suely; Miranda-Castro, Rebeca; de-Los-Santos-Álvarez, Noemí; Miranda-Ordieres, Arturo J; Dos Santos Junior, J Ribeiro; da Silva Fonseca, Rosana A; Lobo-Castañón, Maria Jesús

    2015-08-18

    Cultivation of genetically modified organisms (GMOs) and their use in food and feed is constantly expanding; thus, the question of informing consumers about their presence in food has proven of significant interest. The development of sensitive, rapid, robust, and reliable methods for the detection of GMOs is crucial for proper food labeling. In response, we have experimentally characterized the helicase-dependent isothermal amplification (HDA) and sequence-specific detection of a transgene from the Cauliflower Mosaic Virus 35S Promoter (CaMV35S), inserted into most transgenic plants. HDA is one of the simplest approaches for DNA amplification, emulating the bacterial replication machinery, and resembling PCR but under isothermal conditions. However, it usually suffers from a lack of selectivity, which is due to the accumulation of spurious amplification products. To improve the selectivity of HDA, which makes the detection of amplification products more reliable, we have developed an electrochemical platform targeting the central sequence of HDA copies of the transgene. A binary monolayer architecture is built onto a thin gold film where, upon the formation of perfect nucleic acid duplexes with the amplification products, these are enzyme-labeled and electrochemically transduced. The resulting combined system increases genosensor detectability up to 10(6)-fold, allowing Yes/No detection of GMOs with a limit of detection of ∼30 copies of the CaMV35S genomic DNA. A set of general utility rules in the design of genosensors for detection of HDA amplicons, which may assist in the development of point-of-care tests, is also included. The method provides a versatile tool for detecting nucleic acids with extremely low abundance not only for food safety control but also in the diagnostics and environmental control areas. PMID:26198403

  10. Targeting helicase-dependent amplification products with an electrochemical genosensor for reliable and sensitive screening of genetically modified organisms.

    PubMed

    Moura-Melo, Suely; Miranda-Castro, Rebeca; de-Los-Santos-Álvarez, Noemí; Miranda-Ordieres, Arturo J; Dos Santos Junior, J Ribeiro; da Silva Fonseca, Rosana A; Lobo-Castañón, Maria Jesús

    2015-08-18

    Cultivation of genetically modified organisms (GMOs) and their use in food and feed is constantly expanding; thus, the question of informing consumers about their presence in food has proven of significant interest. The development of sensitive, rapid, robust, and reliable methods for the detection of GMOs is crucial for proper food labeling. In response, we have experimentally characterized the helicase-dependent isothermal amplification (HDA) and sequence-specific detection of a transgene from the Cauliflower Mosaic Virus 35S Promoter (CaMV35S), inserted into most transgenic plants. HDA is one of the simplest approaches for DNA amplification, emulating the bacterial replication machinery, and resembling PCR but under isothermal conditions. However, it usually suffers from a lack of selectivity, which is due to the accumulation of spurious amplification products. To improve the selectivity of HDA, which makes the detection of amplification products more reliable, we have developed an electrochemical platform targeting the central sequence of HDA copies of the transgene. A binary monolayer architecture is built onto a thin gold film where, upon the formation of perfect nucleic acid duplexes with the amplification products, these are enzyme-labeled and electrochemically transduced. The resulting combined system increases genosensor detectability up to 10(6)-fold, allowing Yes/No detection of GMOs with a limit of detection of ∼30 copies of the CaMV35S genomic DNA. A set of general utility rules in the design of genosensors for detection of HDA amplicons, which may assist in the development of point-of-care tests, is also included. The method provides a versatile tool for detecting nucleic acids with extremely low abundance not only for food safety control but also in the diagnostics and environmental control areas.

  11. Fabrication of DNA Microarrays on Polydopamine-Modified Gold Thin Films for SPR Imaging Measurements

    PubMed Central

    Wood, Jennifer B.; Szyndler, Megan W.; Halpern, Aaron R.; Cho, Kyunghee

    2013-01-01

    Polydopamine (PDA) films were fabricated on thin film gold substrates in a single-step polymerization-deposition process from dopamine solutions and then employed in the construction of robust DNA microarrays for the ultra-sensitive detection of biomolecules with nanoparticle-enhanced surface plasmon resonance (SPR) imaging. PDA multilayers with thicknesses varying from 1 to 5 nm were characterized with a combination of scanning angle SPR and AFM experiments, and 1.3 ± 0.2 nm PDA multilayers were chosen as an optimal thickness for the SPR imaging measurements. DNA microarrays were then fabricated by the reaction of amine-functionalized single-stranded DNA (ssDNA) oligonucleotides with PDA-modified gold thin film microarray elements, and were subsequently employed in SPR imaging measurements of DNA hybridization adsorption and protein-DNA binding. Concurrent control experiments with noncomplementary ssDNA sequences demonstrated that the adhesive PDA multilayer was also able to provide good resistance to the nonspecific binding of biomolecules. Finally, a series of SPR imaging measurements of the hybridization adsorption of DNA-modified gold nanoparticles onto mixed sequence DNA microarrays were used to confirm that the use of PDA multilayer films is a simple, rapid and versatile method for fabricating DNA microarrays for ultrasensitive nanoparticle-enhanced SPR imaging biosensing. PMID:23902428

  12. Electrochemical impedance spectroscopy for graphene surface modification and protein translocation through the chemically modified graphene nanopore

    NASA Astrophysics Data System (ADS)

    Tiwari, Purushottam; Shan, Yuping; Wang, Xuewen; Darici, Yesim; He, Jin

    2014-03-01

    The multilayer graphene surface has been modified using mercaptohexadecanoic acid (MHA) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-750] (DPPE-PEG750). The surface modifications are evaluated using electrochemical impedance spectroscopy (EIS). EIS measurements show the better graphene surface passivation with DPPE-PEG750 than with MHA. After modification with ferritin, the MHA modified surface shows greater charge transfer resistance (Rct) change than DPPE-PEG750 modified surface. Based on these results the translocations of ferritin through modified graphene nanopore with diameter 5-20 nm are studied. The translocation is more successful through DPPE-PEG750 modified graphene nanopore. This concludes that that the attachment of ferritin to DPPE-PEG750 modified graphene nanopore is not significant compared to MHA modified pore for the ferritin translocation hindrance. These results nicely correlate with the EIS data for respective Rct change of ferritin modified surfaces. P. Tiwari would like to thank FIU School of Integrated Science & Humanity, College Arts & Sciences for the research assistantship.

  13. Modified lead titanate thin films for pyroelectric infrared detectors on gold electrodes

    NASA Astrophysics Data System (ADS)

    Ahmed, Moinuddin; Butler, Donald P.

    2015-07-01

    Pyroelectric infrared detectors provide the advantage of both a wide spectral response and dynamic range, which also has enabled systems to be developed with reduced size, weight and power consumption. This paper demonstrates the deposition of lead zirconium titanate (PZT) and lead calcium titanate (PCT) thin films for uncooled pyroelectric detectors with the utilization of gold electrodes. The modified lead titanate thin films were deposited by pulsed laser deposition on gold electrodes. The PZT and PCT thins films deposited and annealed at temperatures of 650 °C and 550 °C respectively demonstrated the best pyroelectric performance in this work. The thin films displayed a pyroelectric effect that increased with temperature. Poling of the thin films was carried out for a fixed time periods and fixed dc bias voltages at elevated temperature in order to increase the pyroelectric coefficient by establishing a spontaneous polarization of the thin films. Poling caused the pyroelectric current to increase one order of magnitude.

  14. Prussian blue-modified nanoporous gold film electrode for amperometric determination of hydrogen peroxide.

    PubMed

    Ghaderi, Seyran; Mehrgardi, Masoud Ayatollahi

    2014-08-01

    In this manuscript, the electrocatalytic reduction of hydrogen peroxides on Prussian blue (PB) modified nanoporous gold film (NPGF) electrode is described. The PB/NPGF is prepared by simple anodizing of a smooth gold film followed by PB film electrodeposition method. The morphology of the PB/NPGF electrode is characterized using scanning electron microscopy (SEM). The effect of solution pH and the scan rates on the voltammetric responses of hydrogen peroxide have also been examined. The amperometric determination of H2O2 shows two linear dynamic responses over the concentration range of 1μM-10μM and 10μM-100μM with a detection limit of 3.6×10(-7)M. Furthermore, this electrode demonstrated good stability, repeatability and selectivity remarkably.

  15. Modified glassy carbon electrodes based on carbon nanostructures for ultrasensitive electrochemical determination of furazolidone.

    PubMed

    Shahrokhian, Saeed; Naderi, Leila; Ghalkhani, Masoumeh

    2016-04-01

    The electrochemical behavior of Furazolidone (Fu) was investigated on the surface of the glassy carbon electrode modified with different carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG), graphene oxide (GO), reduced graphene oxide (RGO) and RGO-CNT hybrids (various ratios) using linear sweep voltammetry (LSV). The results of voltammetric studies exhibited a considerable increase in the cathodic peak current of Fu at the RGO modified GCE, compared to other modified electrodes and also bare GCE. The surface morphology and nature of the RGO film was thoroughly characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The modified electrode showed two linear dynamic ranges of 0.001-2.0 μM and 2.0-10.0 μM with a detection limit of 0.3 nM for the voltammetric determination of Fu. This sensor was used successfully for Fu determination in pharmaceutical and clinical preparations.

  16. Graphene Oxide Modified TiO2 Micro Whiskers and Their Photo Electrochemical Performance.

    PubMed

    Rambabu, Y; Jaiswal, Manu; Roy, Somnath C

    2016-05-01

    Harnessing the solar energy and producing clean fuel hydrogen through efficient photo-electrochemical water splitting has remained one of the most challenging endeavors in materials science. The core problem is to develop a suitable photo-catalyst material that absorbs a significant part of the solar spectrum and produces electron-hole pairs that can be easily separated without recombination. In the recent times, the composite of Titanium dioxide with graphene have been investigated to explore the advantages of both class of materials. Here we report on the photo-electrochemical properties of reduced graphene oxide functionalised TiO2 whiskers. The TiO2 whiskers are obtained from potassium titanium oxide (KTi8O16) synthesized through hydrothermal technique followed by ion exchange method and heat treatment. Graphene oxide was deposited on the as prepared TiO2 whiskers using hydrothermal method. As formed samples were characterized by Raman spectroscopy to confirm the presence of reduced graphene oxide (RGO) attached to TiO2 whiskers. Comparative photo electrochemical studies were carried out for TiO2 and reduced graphene oxide modified TiO2 whiskers. Among these, RGO modified TiO2 whiskers show significantly higher photo current density possibly due to enhancement in charge separation ability and longer electron life times. PMID:27483830

  17. Selective electrochemical determination of cysteine with a cyclotricatechylene modified carbon electrode.

    PubMed

    Lee, Patricia T; Thomson, James E; Karina, Athanasia; Salter, Chris; Johnston, Colin; Davies, Stephen G; Compton, Richard G

    2015-01-01

    We report the selective electrochemical detection of cysteine in the presence of homocysteine and glutathione with the use of an electrode modified with cyclotricatechylene (CTC). A carbon electrode was first modified with cyclotriveratrylene (CTV) and then electrochemically converted into CTC. Using cyclic voltammetry, the redox activity of CTC was investigated along with its electrochemical response to cysteine and the closely related compounds, glutathione and homocysteine which are commonly found in biological media alongside cysteine. The selective detection of cysteine was achieved with the use of the electrocatalytic oxidation reaction and exploiting the different rates of reaction of each thiol with the oxidized CTC via variable scan rate studies. The analytical parameters consisting of sensitivity, range of linear detection, and limit of detection were determined for selective cysteine detection in phosphate buffer solution and tissue culture media where the sensitivity of the system is ca. 0.023 μA μM(-1) and ca. 0.031 μA μM(-1) with a limit of detection of ca. 0.6 μM and ca. 0.9 μM for buffer solution and tissue culture media respectively. Practical assessment of this analytical method was carried out in mixed solutions containing a combination of cysteine, homocysteine and glutathione in both media. The determined results agree well with the added cysteine content. This work presents a novel way of utilizing CTC into detecting cysteine, and is well-suited for bio-marker sensing.

  18. Graphene Oxide Modified TiO2 Micro Whiskers and Their Photo Electrochemical Performance.

    PubMed

    Rambabu, Y; Jaiswal, Manu; Roy, Somnath C

    2016-05-01

    Harnessing the solar energy and producing clean fuel hydrogen through efficient photo-electrochemical water splitting has remained one of the most challenging endeavors in materials science. The core problem is to develop a suitable photo-catalyst material that absorbs a significant part of the solar spectrum and produces electron-hole pairs that can be easily separated without recombination. In the recent times, the composite of Titanium dioxide with graphene have been investigated to explore the advantages of both class of materials. Here we report on the photo-electrochemical properties of reduced graphene oxide functionalised TiO2 whiskers. The TiO2 whiskers are obtained from potassium titanium oxide (KTi8O16) synthesized through hydrothermal technique followed by ion exchange method and heat treatment. Graphene oxide was deposited on the as prepared TiO2 whiskers using hydrothermal method. As formed samples were characterized by Raman spectroscopy to confirm the presence of reduced graphene oxide (RGO) attached to TiO2 whiskers. Comparative photo electrochemical studies were carried out for TiO2 and reduced graphene oxide modified TiO2 whiskers. Among these, RGO modified TiO2 whiskers show significantly higher photo current density possibly due to enhancement in charge separation ability and longer electron life times.

  19. Single step synthesis of gold-amino acid composite, with the evidence of the catalytic hydrogen atom transfer (HAT) reaction, for the electrochemical recognition of Serotonin

    NASA Astrophysics Data System (ADS)

    Choudhary, Meenakshi; Siwal, Samarjeet; Nandi, Debkumar; Mallick, Kaushik

    2016-03-01

    A composite architecture of amino acid and gold nanoparticles has been synthesized using a generic route of 'in-situ polymerization and composite formation (IPCF)' [1,2]. The formation mechanism of the composite has been supported by a model hydrogen atom (H•≡H++e-) transfer (HAT) type of reaction which belongs to the proton coupled electron transfer (PCET) mechanism. The 'gold-amino acid composite' was used as a catalyst for the electrochemical recognition of Serotonin.

  20. Fabrication of a Polyaniline Ultramicroelectrode via a Self Assembled Monolayer Modified Gold Electrode

    PubMed Central

    Bolat, Gulcin; Kuralay, Filiz; Eroglu, Gunes; Abaci, Serdar

    2013-01-01

    Herein, we report a simple and inexpensive way for the fabrication of an ultramicroelectrode and present its characterization by electrochemical techniques. The fabrication of polyaniline UME involves only two steps: modification of a gold (Au) electrode by self assembled monolayers (SAM) and then electrodeposition of polyaniline film on this thiol-coated Au electrode by using cyclic voltammetry and constant potential electrolysis methods. Two types of self-assembled monolayers (4-mercapto-1-butanol, MB, and 11-mercaptoundecanoic acid, MUA) were used, respectively, to see the effect of chain length on microelectrode formation. Microelectrode fabrication and utility of the surface was investigated by cyclic voltammetric measurements in a redox probe. The thus prepared polyaniline microelectrode was then used for DNA immobilization. Discrimination between double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) was obtained with enhanced electrochemical signals compared to a polyaniline-coated Au electrode. Different modifications on the electrode surfaces were examined using scanning electron microscopy (SEM). PMID:23797740

  1. Inkjet-printed gold nanoparticle electrochemical arrays on plastic. Application to immunodetection of a cancer biomarker protein

    PubMed Central

    Jensen, Gary C.; Krause, Colleen E.; Sotzing, Gregory A.; Rusling, James F.

    2011-01-01

    Electrochemical detection combined with nanostructured sensor surfaces offers potentially low-cost, high-throughput solutions for detection of clinically significant proteins. Inkjet printing offers an inexpensive non-contact fabrication method for microelectronics that is easily adapted for incorporating into protein immunosensor devices. Herein we report the first direct fabrication of inkjet-printed gold nanoparticle arrays, and apply them to electrochemical detection of the cancer biomarker interleukin-6 (IL-6) in serum. The gold nanoparticle ink was printed on a flexible, heat resistant polyimide Kapton substrate and subsequently sintered to create eight-electrode arrays costing <0.2 euro per array. The inkjet-printed working electrodes had reproducible surface areas with RSD <3%. Capture antibodies for IL-6 were linked onto the eight-electrode array, and used in sandwich immunoassays. A biotinylated secondary antibody with 16-18 horseradish peroxidase labels was used, and detection was achieved by hydroquinone-mediated amperometry. The arrays provided a clinically relevant detection limit of 20 pg mL−1 in calf serum, sensitivity of 11.4 nA pg−1 cm−2, and a linear dynamic range of 20–400 pg mL−1. PMID:21212889

  2. Inkjet-printed gold nanoparticle electrochemical arrays on plastic. Application to immunodetection of a cancer biomarker protein.

    PubMed

    Jensen, Gary C; Krause, Colleen E; Sotzing, Gregory A; Rusling, James F

    2011-03-21

    Electrochemical detection combined with nanostructured sensor surfaces offers potentially low-cost, high-throughput solutions for detection of clinically significant proteins. Inkjet printing offers an inexpensive non-contact fabrication method for microelectronics that is easily adapted for incorporating into protein immunosensor devices. Herein we report the first direct fabrication of inkjet-printed gold nanoparticle arrays, and apply them to electrochemical detection of the cancer biomarker interleukin-6 (IL-6) in serum. The gold nanoparticle ink was printed on a flexible, heat resistant polyimide Kapton substrate and subsequently sintered to create eight-electrode arrays costing <0.2 euro per array. The inkjet-printed working electrodes had reproducible surface areas with RSD <3%. Capture antibodies for IL-6 were linked onto the eight-electrode array, and used in sandwich immunoassays. A biotinylated secondary antibody with 16-18 horseradish peroxidase labels was used, and detection was achieved by hydroquinone-mediated amperometry. The arrays provided a clinically relevant detection limit of 20 pg mL(-1) in calf serum, sensitivity of 11.4 nA pg(-1) cm(-2), and a linear dynamic range of 20-400 pg mL(-1).

  3. Effects of Synthetic Amphiphilic alpha-Helical Peptides on the Electrochemical and Structural Properties of Supported Hybrid Bilayers on Gold

    SciTech Connect

    Smith,M.; Tong, J.; Genzer, J.; Fischer, D.; Kilpatrick, P.

    2006-01-01

    Amphiphilic {alpha}-helices were formed from designed synthetic peptides comprising alanine, phenylalanine, and lysine residues. The insertion of the -helical peptides into hybrid bilayers assembled on gold was studied by a variety of methods to assess the resulting structural characteristics, such as electrical resistance and molecular orientation. Self-assembled monolayers (SAMs) of dodecanethiol (DDT); octadecanethiol (ODT); and 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) were formed on gold substrates with and without incorporated peptide. Supported hybrid bilayers and multilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were formed on SAMs by the 'paint-freeze' method of bilayer formation. Modeling of electrochemical impedance spectroscopy data using equivalent electrochemical circuits revealed that the addition of peptide decreased dramatically the resistive element of the bilayer films while maintaining the value of the capacitive element, indicating successful incorporation of peptide into a well-formed bilayer. Near-edge X-ray absorption fine structure spectroscopy data provided evidence that the molecules in the SAMs and hybrid multilayers were ordered even in the presence of peptide. The peptide insertion into the SAM was confirmed by observing the {pi}* resonance peak correlating with phenylalanine and a peak in the nitrogen K-edge regime attributable to the peptide bond.

  4. Modified Electrodes Used for Electrochemical Detection of Metal Ions in Environmental Analysis

    PubMed Central

    March, Gregory; Nguyen, Tuan Dung; Piro, Benoit

    2015-01-01

    Heavy metal pollution is one of the most serious environmental problems, and regulations are becoming stricter. Many efforts have been made to develop sensors for monitoring heavy metals in the environment. This review aims at presenting the different label-free strategies used to develop electrochemical sensors for the detection of heavy metals such as lead, cadmium, mercury, arsenic etc. The first part of this review will be dedicated to stripping voltammetry techniques, on unmodified electrodes (mercury, bismuth or noble metals in the bulk form), or electrodes modified at their surface by nanoparticles, nanostructures (CNT, graphene) or other innovative materials such as boron-doped diamond. The second part will be dedicated to chemically modified electrodes especially those with conducting polymers. The last part of this review will focus on bio-modified electrodes. Special attention will be paid to strategies using biomolecules (DNA, peptide or proteins), enzymes or whole cells. PMID:25938789

  5. A Genetically Modified Tobacco Mosaic Virus that can Produce Gold Nanoparticles from a Metal Salt Precursor

    PubMed Central

    Love, Andrew J.; Makarov, Valentine V.; Sinitsyna, Olga V.; Shaw, Jane; Yaminsky, Igor V.; Kalinina, Natalia O.; Taliansky, Michael E.

    2015-01-01

    We genetically modified tobacco mosaic virus (TMV) to surface display a characterized peptide with potent metal ion binding and reducing capacity (MBP TMV), and demonstrate that unlike wild type TMV, this construct can lead to the formation of discrete 10–40 nm gold nanoparticles when mixed with 3 mM potassium tetrachloroaurate. Using a variety of analytical physicochemical approaches it was found that these nanoparticles were crystalline in nature and stable. Given that the MBP TMV can produce metal nanomaterials in the absence of chemical reductants, it may have utility in the green production of metal nanomaterials. PMID:26617624

  6. A Genetically Modified Tobacco Mosaic Virus that can Produce Gold Nanoparticles from a Metal Salt Precursor.

    PubMed

    Love, Andrew J; Makarov, Valentine V; Sinitsyna, Olga V; Shaw, Jane; Yaminsky, Igor V; Kalinina, Natalia O; Taliansky, Michael E

    2015-01-01

    We genetically modified tobacco mosaic virus (TMV) to surface display a characterized peptide with potent metal ion binding and reducing capacity (MBP TMV), and demonstrate that unlike wild type TMV, this construct can lead to the formation of discrete 10-40 nm gold nanoparticles when mixed with 3 mM potassium tetrachloroaurate. Using a variety of analytical physicochemical approaches it was found that these nanoparticles were crystalline in nature and stable. Given that the MBP TMV can produce metal nanomaterials in the absence of chemical reductants, it may have utility in the green production of metal nanomaterials. PMID:26617624

  7. Electrochemical sensor based on magnetic graphene oxide@gold nanoparticles-molecular imprinted polymers for determination of dibutyl phthalate.

    PubMed

    Li, Xiangjun; Wang, Xiaojiao; Li, Leilei; Duan, Huimin; Luo, Chuannan

    2015-01-01

    A novel composite of magnetic graphene oxide @ gold nanoparticles-molecular imprinted polymers (MGO@AuNPs-MIPs) was synthesized and applied as a molecular recognition element to construct dibutyl phthalate (DBP) electrochemical sensor. The composite of MGO@AuNPs was first synthesized using coprecipitation and self-assembly technique. Then the template molecules (DBP) were absorbed at the MGO@AuNPs surface due to their excellent affinity, and subsequently, selective copolymerization of methacrylic acid and ethylene glycol dimethacrylate was further achieved at the MGO@AuNPs surface. Potential scanning was presented to extract DBP molecules from the imprinted polymers film rapidly and completely. As a consequence, an electrochemical sensor for highly sensitive and selective detection of DBP was successfully constructed as demonstration based on the synthesized MGO@AuNPs-MIPs composite. Under optimal experimental conditions, selective detection of DBP in a linear concentration range of 2.5 × 10(-9)-5.0 × 10(-6)mol/L was obtained. The new DBP electrochemical sensor also exhibited excellent repeatability, which expressed as relative standard deviation (RSD) was about 2.50% for 30 repeated analyses of 2.0 × 10(-6)mol/L DBP.

  8. Electrochemical generation of mercury cold vapor and its in-situ trapping in gold-covered graphite tube atomizers

    NASA Astrophysics Data System (ADS)

    Červený, Václav; Rychlovský, Petr; Netolická, Jarmila; Šíma, Jan

    2007-03-01

    The combination of more efficient flow-through electrochemical mercury cold vapor generation with its in-situ trapping in a graphite tube atomizer is described. This coupled technique has been optimized to attain the maximum sensitivity for Hg determination and to minimize the limits of detection and determination. A laboratory constructed thin-layer flow-through cell with a platinum cathode served as the cold vapor generator. Various cathode arrangements with different active surface areas were tested. Automated sampling equipment for the graphite atomizer with an untreated fused silica capillary was used for the introduction of the mercury vapor. The inner surface of the graphite tube was covered with a gold foil placed against the sampling hole. The results attained for the electrochemical mercury cold vapor generation (an absolute limit of detection of 80 pg; peak absorbance, 3 σ criterion) were compared with the traditional vapor generation using NaBH 4 as the reducing agent (an absolute limit of detection of 124 pg; peak absorbance, 3 σ criterion). The repeatability at the 5 ng ml - 1 level was better than 4.1% (RSD) for electrochemical mercury vapor generation and better than 5.6% for the chemical cold vapor generation. The proposed method was applied to the determination the of Hg contents in a certified reference material and in spiked river water samples.

  9. A micro hemoglobin-A1c immunosensor based on FET and electrochemical growth of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Qu, Lan; Bian, Chao; Sun, Jizhou; Han, Jinghong; Xia, Shanhong

    2008-12-01

    A micro potentiometric hemoglobin-A1c (HbA1c) immunosensor based on field-effect transistor (FET) and electrochemical growth of gold nanoparticles (AuNPs) in polypyrrole (PPy) film is reported. Integrated ion-sensitive field-effect transistors (ISFETs) chips containing two ISFETs, two reference FETs (REFET) and the signal read-out circuits were fabricated. Micro electrodes of the sensor were fabricated by MEMS techniques and electrochemical method, both compatible with electrode miniaturization. The simple and direct procedure to form PPy-AuNPs composite film enhances the sensitivity of the micro sensor. Electrochemical characterization and morphology study by scanning electron microscopy (SEM) confirm the presence of AuNPs in PPy. Simple, rapid and precise differential measurement of HbA1c is achieved. HbA1c in the concentration ranges of 2-20 ng/ml and 4-15 µg/ml can be detected by this sensor with a response time less than 1 min, which meets the needs of clinical detection of HbA1c. The miniaturized electrodes and integrated ISFET chip have the potential to be integrated and to achieve system on chip (SOC).

  10. Functional graphene-gold nano-composite fabricated electrochemical biosensor for direct and rapid detection of bisphenol A.

    PubMed

    Pan, Daodong; Gu, Yuanyuan; Lan, Hangzhen; Sun, Yangying; Gao, Huiju

    2015-01-01

    In this research, the graphene with excellent dispersity is prepared successfully by introducing gold nanoparticle to separate the individual sheets. Various techniques are adopted to characterize the prepared graphene and graphene-gold nanoparticle composite materials. This fabricated new composite material is used as the support material to construct a novel tyrosinase based biosensor for detection of bisphenol A (BPA). The electrochemical performances of the proposed new enzyme biosensor were investigated by differential pulse voltammetry (DPV) method. The proposed biosensor exhibited excellent performance for BPA determination with a wide linear range (2.5×10(-3)-3.0 μM), a highly reproducible response (RSD of 2.7%), low interferences and long-term stability. And more importantly, the calculated detection limit of the proposed biosensor was as low as 1 nM. Compared with other detection methods, this graphene-gold nanoparticle composite based tyrosinase biosensor is proved to be a promising and reliable tool for rapid detection of BPA for on-site analysis of emergency BPA related pollution affairs.

  11. Electrochemical biosensor modified with dsDNA monolayer for restriction enzyme activity determination.

    PubMed

    Zajda, Joanna; Górski, Łukasz; Malinowska, Elżbieta

    2016-06-01

    A simple and cost effective method for the determination of restriction endonuclease activity is presented. dsDNA immobilized at a gold electrode surface is used as the enzymatic substrate, and an external cationic redox probe is employed in voltammetric measurements for analytical signal generation. The assessment of enzyme activity is based on a decrease of a current signal derived from reduction of methylene blue which is present in the sample solution. For this reason, the covalent attachment of the label molecule is not required which significantly reduces costs of the analysis and simplifies the entire determination procedure. The influence of buffer components on utilized dsDNA/MCH monolayer stability and integrity is also verified. Electrochemical impedance spectroscopy measurements reveal that due to pinhole formation during enzyme activity measurement the presence of any surfactants should be avoided. Additionally, it is shown that the sensitivity of the electrochemical biosensor can be tuned by changing the restriction site location along the DNA length. Under optimal conditions the proposed biosensor exhibits a linear response toward PvuII activity within a range from 0.25 to 1.50 U/μL. PMID:26859430

  12. Electrochemical biosensor modified with dsDNA monolayer for restriction enzyme activity determination.

    PubMed

    Zajda, Joanna; Górski, Łukasz; Malinowska, Elżbieta

    2016-06-01

    A simple and cost effective method for the determination of restriction endonuclease activity is presented. dsDNA immobilized at a gold electrode surface is used as the enzymatic substrate, and an external cationic redox probe is employed in voltammetric measurements for analytical signal generation. The assessment of enzyme activity is based on a decrease of a current signal derived from reduction of methylene blue which is present in the sample solution. For this reason, the covalent attachment of the label molecule is not required which significantly reduces costs of the analysis and simplifies the entire determination procedure. The influence of buffer components on utilized dsDNA/MCH monolayer stability and integrity is also verified. Electrochemical impedance spectroscopy measurements reveal that due to pinhole formation during enzyme activity measurement the presence of any surfactants should be avoided. Additionally, it is shown that the sensitivity of the electrochemical biosensor can be tuned by changing the restriction site location along the DNA length. Under optimal conditions the proposed biosensor exhibits a linear response toward PvuII activity within a range from 0.25 to 1.50 U/μL.

  13. Fluorescence Characterization of Gold Modified Liposomes with Antisense N-myc DNA Bound to the Magnetisable Particles with Encapsulated Anticancer Drugs (Doxorubicin, Ellipticine and Etoposide)

    PubMed Central

    Skalickova, Sylvie; Nejdl, Lukas; Kudr, Jiri; Ruttkay-Nedecky, Branislav; Jimenez Jimenez, Ana Maria; Kopel, Pavel; Kremplova, Monika; Masarik, Michal; Stiborova, Marie; Eckschlager, Tomas; Adam, Vojtech; Kizek, Rene

    2016-01-01

    Liposome-based drug delivery systems hold great potential for cancer therapy. The aim of this study was to design a nanodevice for targeted anchoring of liposomes (with and without cholesterol) with encapsulated anticancer drugs and antisense N-myc gene oligonucleotide attached to its surface. To meet this main aim, liposomes with encapsulated doxorubicin, ellipticine and etoposide were prepared. They were further characterized by measuring their fluorescence intensity, whereas the encapsulation efficiency was estimated to be 16%. The hybridization process of individual oligonucleotides forming the nanoconstruct was investigated spectrophotometrically and electrochemically. The concentrations of ellipticine, doxorubicin and etoposide attached to the nanoconstruct in gold nanoparticle-modified liposomes were found to be 14, 5 and 2 µg·mL−1, respectively. The study succeeded in demonstrating that liposomes are suitable for the transport of anticancer drugs and the antisense oligonucleotide, which can block the expression of the N-myc gene. PMID:26927112

  14. Electrochemical degradation of carbamazepine using modified electrode with graphene-AuAg composite

    NASA Astrophysics Data System (ADS)

    Pogacean, F.; Biris, A. R.; Socaci, C.; Floare-Avram, V.; Rosu, M. C.; Coros, M.; Pruneanu, S.

    2015-12-01

    Carbamazepine is a pharmaceutical drug which has been detected in surface and drinking water primarily due to human usage but also from the accidental disposal of pharmaceuticals into sewers. We have developed a graphene-modified electrode which was tested at the detection and degradation of carbamazepine. The oxidation process was studied by cyclic voltammetry in aqueous and organic solutions. The electrochemical degradation of carbamazepine was performed by polarizing the working electrode at a certain potential, for different times (from 5 to 60 minutes). The degradation efficiency was highly dependent on the type of solution and on the supporting electrolyte.

  15. Electrochemical Determination of Trace Sudan I Contamination in Chili Powder at Carbon Nanotube Modified Electrodes

    PubMed Central

    Ming, Liang; Xi, Xia; Chen, Tingting; Liu, Jie

    2008-01-01

    We have developed a simple, convenient and inexpensive voltammetric method for determining trace Sudan I contamination in chili powder, based on the catalyzed electrochemical reduction of Sudan I at the carbon nanotube modified electrode. Under optimized conditions, the method exhibited acceptable analytical performance in terms of linearity (over the concentration range 6.0×10−7 to 7.5×10−5 M, r = 0.9967), detection limit (2.0×10−7 M) and reproducibility (RSD = 4.6%, n=10, for 2.0×10−5 M Sudan I).

  16. Self-assembled monolayer films of C[sub 60]/on cysteamine-modified gold

    SciTech Connect

    Caldwell, W.B.; Chen, K.; Mirkin, C.A.; Babinec, S.J. Dow Chemical Company, Midland, MI )

    1993-08-01

    Self-assembled monolayer films (SAMs) of C[sub 60] on cysteamine-modified and cysteamine/ethanethiol-modified Au are reported. The monolayers were characterized via contact angle measurements, X-ray photoelectron spectroscopy, electrochemistry, and quartz crystal microbalance (QCM) measurements. C[sub 60] surface coverage (2.0 [times] 10[sup [minus]10] mol/cm[sup 2]) for a film formed on pure cysteamine was determined by QCM measurements and compares remarkably well with monolayer coverage (1.9 [times] 10[sup [minus]10] mol/cm[sup 2]) predicted by a model based on crystallographic data for C[sub 60]. These experiments demonstrate the utility of the QCM in characterizing and monitoring the growth of fullerene SAMs. C[sub 60] SAMs formed on pure cysteamine yield strikingly different electrochemical responses than those formed on prelayers consisting of varying ratios of ethanethiol and cysteamine and previously reported monolayers of C[sub 60] on (aminopropyl)silanized oxide surfaces. Although the C[sub 60] SAMs are stable under ambient conditions, the fullerenes may be desorbed from the surface through electrochemical reduction of the films for extended periods of time (> 10 min). 11 refs., 2 figs.

  17. Electrical characterization of gold and platinum thin film electrodes with polyaniline modified surfaces

    NASA Astrophysics Data System (ADS)

    Aggas, John Richard

    Recent studies into soft organic electronics have burgeoned as a result of discoveries of conducting polymers such as polyaniline, polythiophene, and polypyrrole. However, in order to make these conducting polymers suitable for in vivo soft organic electronics, they must be developed so that they can be biocompatible and provide accurate sensing. Chitosan, a naturally occurring polymer structure found in exoskeletons of crustaceans, has been studied for its biocompatible properties. Composites of polyaniline (PAn), an intrinsically conductive polymer (ICP) and chitosan (Chi), a biopolymer, were developed and applied to gold and platinum Thin Film Electrode (TFE) devices. Electropolymerization and drop cast deposition were utilized to modify TFEs with a thin film of PAn or PAn-Chi composite. The impedance response over a spectrum of frequencies was studied for blank control TFEs, platinized TFEs, and platinized TFEs with various polyaniline coatings. Impedance measurements were taken in dry environments, DI Water, and in buffers such as PBS, and HEPES. Current-Voltage (I-V) characterization was used to study the current response and SEM imaging was used to study the surface topography. Resistance was measured for PAn modified unplatinized gold TFEs with varying amounts of incorporated chitosan. Impedance measurements of control and platinized TFEs yielded results similar to a low pass filter. Due to the conductive nature of polyaniline, the impedance of TFEs decreased substantially after poylaniline deposition. Measured resistance values for polyaniline and chitosan composites on TFEs revealed a window of concentrations of incorporated chitosan to lower resistance.

  18. A multianalyte electrochemical immunosensor based on patterned carbon nanotubes modified substrates for detection of pesticides.

    PubMed

    Liu, Guozhen; Guo, Wenqi; Song, Dandan

    2014-02-15

    A novel multianalyte electrochemical immunosensor based on the assembly of patterned SWNTs on glassy carbon (GC) substrates was developed for simultaneous detection of endosulfan and paraoxon. Based on aryldiazonium salt chemistry, forest of SWNTs can be patterned on GC substrates by C3C bonding using micro contact printing (MCP), which provides an interface showing efficient electron transfer between biomolecules and electrodes. Then redox molecules FDMA and PQQ can be attached to the SWNTs, respectively followed by the attachment of specific epitopes and antibodies. The modified sensing surfaces were characterized by XPS, SEM, AFM and electrochemistry. Based on the current change of specific redox probes, the fabricated immunosensor array can be used for simultaneous detection of endosulfan and paraoxon by a displacement assay. In phosphate buffer solution (50mM, pH 7.0), there is a linear relationship between electrochemical signal of FDMA and the concentration of endosulfan over the range of 0.05-100 ppb with a detection limit of 0.05ppb; the linear range between electrochemical signal of PQQ and the concentration of paraoxon is 2-2500 ppb with a detection limit of 2 ppb. The immunosensor array demonstrates high repeatability, reproducibility, stability and selectivity for the detection of endosulfan and paraoxon.

  19. Highly sensitive voltammetric sensor based on immobilization of bisphosphoramidate-derivative and quantum dots onto multi-walled carbon nanotubes modified gold electrode for the electrocatalytic determination of olanzapine.

    PubMed

    Mohammadi-Behzad, Leila; Gholivand, Mohammad Bagher; Shamsipur, Mojtaba; Gholivand, Khodayar; Barati, Ali; Gholami, Akram

    2016-03-01

    In the present paper, a new bisphosphoramidate derivative compound, 1, 4-bis(N-methyl)-benzene-bis(N-phenyl, N-benzoylphosphoramidate) (BMBPBP), was synthesized and used as a mediator for the electrocatalytic oxidation of olanzapine. The electro-oxidation of olanzapine at the surface of the BMBPBP/CdS-quantum dots/multi-walled carbon nanotubes (BMBPBP/CdS-QDs/MWCNTs) modified gold electrode was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. This sensor showed an excellent electrocatalytic oxidation activity toward olanzapine at less positive potential, pronounced current response, and good sensitivity. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) were determined for olanzapine oxidation, using the electrochemical approaches. Surface morphology and electrochemical properties of the prepared modified electrode were investigated by scanning electron microscopy (SEM), cyclic voltammetry and electrochemical impedance spectroscopy techniques. The hydrodynamic amperometry at rotating modified electrode at constant potential versus reference electrode was used for detection of olanzapine. Under optimized conditions, the calibration plot was linear in the concentration range of 20 nM to 100 μM and detection limit was found to be 6 nM. The proposed method was successfully applied to the determination of olanzapine in pharmaceuticals and human serum samples.

  20. Highly sensitive voltammetric sensor based on immobilization of bisphosphoramidate-derivative and quantum dots onto multi-walled carbon nanotubes modified gold electrode for the electrocatalytic determination of olanzapine.

    PubMed

    Mohammadi-Behzad, Leila; Gholivand, Mohammad Bagher; Shamsipur, Mojtaba; Gholivand, Khodayar; Barati, Ali; Gholami, Akram

    2016-03-01

    In the present paper, a new bisphosphoramidate derivative compound, 1, 4-bis(N-methyl)-benzene-bis(N-phenyl, N-benzoylphosphoramidate) (BMBPBP), was synthesized and used as a mediator for the electrocatalytic oxidation of olanzapine. The electro-oxidation of olanzapine at the surface of the BMBPBP/CdS-quantum dots/multi-walled carbon nanotubes (BMBPBP/CdS-QDs/MWCNTs) modified gold electrode was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. This sensor showed an excellent electrocatalytic oxidation activity toward olanzapine at less positive potential, pronounced current response, and good sensitivity. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) were determined for olanzapine oxidation, using the electrochemical approaches. Surface morphology and electrochemical properties of the prepared modified electrode were investigated by scanning electron microscopy (SEM), cyclic voltammetry and electrochemical impedance spectroscopy techniques. The hydrodynamic amperometry at rotating modified electrode at constant potential versus reference electrode was used for detection of olanzapine. Under optimized conditions, the calibration plot was linear in the concentration range of 20 nM to 100 μM and detection limit was found to be 6 nM. The proposed method was successfully applied to the determination of olanzapine in pharmaceuticals and human serum samples. PMID:26706508

  1. A novel electrochemical alkylation of aniline with methanol over Zn/Cu salts modified kaolin.

    PubMed

    Ma, Hongzhu; Wang, Bo; Zhao, Jun

    2008-04-01

    A novel liquid phase alkylation of aniline with methanol over Zn/Cu salts modified kaolin assisted with a pair of porous carbon electrode in slurry-bed reactor under constant current intensity, room temperature and atmospheric pressure was reported. The Zn/Cu salts modified kaolin catalysts were synthesized and characterized by infrared spectrometer (IR), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), which showed that the transition metals were completely supported on kaolin's structure and formed a pored one. The effect parameters, such as initial pH, electrolysis time, metal ratio with kaolin and salts composition in this electrochemical catalytic system, were studied. The procedure was inspected by ultraviolet-visible spectrum (UV-vis), and the product distribution was detected by gas chromatography/mass spectrometry (GC/MS). In addition, a possible reaction mechanism was also proposed. PMID:17706340

  2. A novel electrochemical alkylation of aniline with methanol over Zn/Cu salts modified kaolin.

    PubMed

    Ma, Hongzhu; Wang, Bo; Zhao, Jun

    2008-04-01

    A novel liquid phase alkylation of aniline with methanol over Zn/Cu salts modified kaolin assisted with a pair of porous carbon electrode in slurry-bed reactor under constant current intensity, room temperature and atmospheric pressure was reported. The Zn/Cu salts modified kaolin catalysts were synthesized and characterized by infrared spectrometer (IR), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), which showed that the transition metals were completely supported on kaolin's structure and formed a pored one. The effect parameters, such as initial pH, electrolysis time, metal ratio with kaolin and salts composition in this electrochemical catalytic system, were studied. The procedure was inspected by ultraviolet-visible spectrum (UV-vis), and the product distribution was detected by gas chromatography/mass spectrometry (GC/MS). In addition, a possible reaction mechanism was also proposed.

  3. A Novel Electrochemical Detector using Prussian Blue Modified Indium Tin Oxide Electrode

    NASA Astrophysics Data System (ADS)

    Yi, In-Je; Kim, Ju-Ho; Kang, C. J.; Choi, Y. J.; Lee, Kisay; Kim, Yong-Sang

    2006-01-01

    We propose a novel electrochemical detector (ECD) to catalyze redox efficiently by electrodepositing Prussian blue (PB, ferric hexacyanoferrate) on the indium tin oxide (ITO) electrode. Capillary electrophoresis (CE) and amperometric methods were used. We investigated the PB surface properties by topography from atomic force microscopy (AFM). The PB film on dense and smooth surfaces could catalyze redox reaction efficiently. Compared with CE-ECD microchips using a bare-ITO electrode, the proposed CE-ECD microchip using a PB modified electrode has shown better sensitivity of the electropherograms. It has been verified that wide-ranging detection can be performed under the limits of 0.01 mM of dopamine and catechol respectively when we use a PB modified electrode.

  4. Electrochemical Determination of Glycoalkaloids Using a Carbon Nanotubes-Phenylboronic Acid Modified Glassy Carbon Electrode

    PubMed Central

    Wang, Huiying; Liu, Mingyue; Hu, Xinxi; Li, Mei; Xiong, Xingyao

    2013-01-01

    A versatile strategy for electrochemical determination of glycoalkaloids (GAs) was developed by using a carbon nanotubes-phenylboronic acid (CNTs-PBA) modified glassy carbon electrode. PBA reacts with α-solanine and α-chaconine to form a cyclic ester, which could be utilized to detect GAs. This method allowed GA detection from 1 μM to 28 μM and the detection limit was 0.3 μM. Affinity interaction of GAs and immobilized PBA caused an essential change of the peak current. The CNT-PBA modified electrodes were sensitive for detection of GAs, and the peak current values were in quite good agreement with those measured by the sensors. PMID:24287539

  5. Enzymatic immuno-assembly of gold nanoparticles for visualized activity screening of histone-modifying enzymes.

    PubMed

    Zhen, Zhen; Tang, Li-Juan; Long, Haoxu; Jiang, Jian-Hui

    2012-04-17

    Activity screening of histone-modifying enzymes is of paramount importance for epigenetic research as well as clinical diagnostics and therapeutics. A novel biosensing strategy has been developed for sensitive and selective detection of histone-modifying enzymes as well as their inhibitors. This strategy relies on the antibody-mediated assembly of gold nanoparticles (AuNPs) decorated with substrate peptides that are subjected to enzymatic modifications by the histone-modifying enzymes. This design allows a visual and homogeneous assay of the enzyme activity using antibodies without any labels, which circumvents the requirements to prefunctionalize the antibody and affords improved assay simplicity and throughput. Additionally, the use of antibody-based recognition of modified peptides could offer improved specificity as compared with existing techniques based on the enzyme coupled assay. We have demonstrated this strategy using a histone methyltransferase acting on histone H3 (Lys 4) and a histone acetyltransferase acting on histone H3 (Lys 14). The results reveal that the absorption peak characteristic for AuNPs decreases dynamically with increasing activity of the enzymes with concomitant visualizable color attenuation, and subnanomolar detection limits are readily achieved for both enzymes. The developed strategy can thus offer a robust and convenient visualized platform for screening the enzyme activities and their inhibitors with high sensitivity and selectivity.

  6. Zinc oxide inverse opal electrodes modified by glucose oxidase for electrochemical and photoelectrochemical biosensor.

    PubMed

    Xia, Lei; Song, Jian; Xu, Ru; Liu, Dali; Dong, Biao; Xu, Lin; Song, Hongwei

    2014-09-15

    The ZnO inverse opal photonic crystals (IOPCs) were synthesized by the sol-gel method using the polymethylmethacrylate (PMMA) as a template. For glucose detection, glucose oxidase (GOD) was further immobilized on the inwall and surface of the IOPCs. The biosensing properties toward glucose of the Nafion/GOD/ZnO IOPCs modified FTO electrodes were carefully studied and the results indicated that the sensitivity of ZnO IOPCs modified electrode was 18 times than reference electrode due to the large surface area and uniform porous structure of ZnO IOPCs. Moreover, photoelectrochemical detection for glucose using the electrode was realized and the sensitivity approached to 52.4 µA mM(-1) cm(-2), which was about four times to electrochemical detection (14.1 µA mM(-1) cm(-2)). It indicated that photoelectrochemical detection can highly improve the sensor performance than conventional electrochemical method. It also exhibited an excellent anti-interference property and a good stability at the same time. This work provides a promising approach for realizing excellent photoelectrochemical biosensor of similar semiconductor photoelectric material. PMID:24752145

  7. Zinc oxide inverse opal electrodes modified by glucose oxidase for electrochemical and photoelectrochemical biosensor.

    PubMed

    Xia, Lei; Song, Jian; Xu, Ru; Liu, Dali; Dong, Biao; Xu, Lin; Song, Hongwei

    2014-09-15

    The ZnO inverse opal photonic crystals (IOPCs) were synthesized by the sol-gel method using the polymethylmethacrylate (PMMA) as a template. For glucose detection, glucose oxidase (GOD) was further immobilized on the inwall and surface of the IOPCs. The biosensing properties toward glucose of the Nafion/GOD/ZnO IOPCs modified FTO electrodes were carefully studied and the results indicated that the sensitivity of ZnO IOPCs modified electrode was 18 times than reference electrode due to the large surface area and uniform porous structure of ZnO IOPCs. Moreover, photoelectrochemical detection for glucose using the electrode was realized and the sensitivity approached to 52.4 µA mM(-1) cm(-2), which was about four times to electrochemical detection (14.1 µA mM(-1) cm(-2)). It indicated that photoelectrochemical detection can highly improve the sensor performance than conventional electrochemical method. It also exhibited an excellent anti-interference property and a good stability at the same time. This work provides a promising approach for realizing excellent photoelectrochemical biosensor of similar semiconductor photoelectric material.

  8. Calculation of Electrochemical Reorganization Energies for Redox Molecules at Self-Assembled Monolayer Modified Electrodes

    SciTech Connect

    Ghosh, Soumya; Hammes-Schiffer, Sharon

    2015-01-02

    Electrochemical electron transfer reactions play an important role in energy conversion processes with many technological applications. Electrodes modified by self-assembled monolayers (SAMs) are useful because the double layer effects are reduced. An important quantity for calculating the electron transfer rate constant is the reorganization energy, which is associated with changes in solute geometry and solvent configuration. In this Letter, an approach for calculating the electrochemical solvent reorganization energy for a redox molecule attached to or near a SAM modified electrode is presented. This integral equations formalism polarizable continuum model (IEF-PCM) approach accounts for the detailed electronic structure of the molecule, as well as the contributions from the electrode, SAM, and electronic and inertial solvent responses. The calculated total reorganization energies are in good agreement with experimental data for a series of metal complex in aqueous solution. This approach will be useful for calculating electron transfer rate constants for molecular electrocatalysts. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  9. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    SciTech Connect

    Marina, Olga A; Stevenson, Jeffry W

    2010-11-23

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  10. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-03-02

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  11. Electrochemical and scanning probe microscopic characterization of spontaneously adsorbed organothiolate monolayers at gold

    SciTech Connect

    Wong, Sze-Shun Season

    1999-12-10

    This dissertation presented several results which add to the general knowledge base regarding organothiolates monolayer spontaneously adsorbed at gold films. Common to the body of this work is the use of voltammetric reductive resorption and variants of scanning probe microscopy to gain insight into the nature of the monolayer formation process as well as the resulting interface. The most significant result from this work is the success of using friction force microscopy to discriminate the end group orientation of monolayer chemisorbed at smooth gold surfaces with micrometer resolution (Chapter 4). The ability to detect the differences in the orientational disposition is demonstrated by the use PDMS polymer stamp to microcontact print an adlayer of n-alkanethiolate of length n in a predefine pattern onto a gold surface, followed by the solution deposition of a n-alkanethiol of n {+-} 1 to fill in the areas on the gold surface intentionally not coated by the stamping process. These two-component monolayers can be discriminated by using friction force microscopy which detects differences in friction contributed by the differences in the orientation of the terminal groups at surfaces. This success has recently led to the detection of the orientation differences at nanometer scale. Although the substrates examined in this work consisted entirely of smooth gold films, the same test can be performed on other smooth substrates and monolayer materials.

  12. Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films.

    PubMed

    Zhu, Wencai; Huang, Hui; Gao, Xiaochun; Ma, Houyi

    2014-12-01

    Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1-65 μM with a low detection limit of 0.01 μM (S/N=3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets.

  13. Fabrication of an ultrasensitive ibuprofen nanoaptasensor based on covalent attachment of aptamer to electrochemically deposited gold-nanoparticles on glassy carbon electrode.

    PubMed

    Roushani, Mahmoud; Shahdost-Fard, Faezeh

    2015-11-01

    The paper reports the development of an ultrasensitive nanoaptasensor based on the covalent attachment of an aptamer (Apt) to gold-nanoparticles (AuNPs) deposited on the surface of a glassy carbon electrode (GCE) as the unique platform. The developed nanoaptasensor was utilized to assay the anti-inflammatory drug, ibuprofen (IBP). The sensing platform was fabricated using a single-stage electrodeposite approach. It is worth noting that the proposed nanoaptasensor combines the advantages of the deposition of neatly arranged AuNPs (enlarged active surface area and strengthened electrochemical signal) and the elimination of enzymes or antibodies for the amplified detection of IBP, with the covalent attachment of the Apt to the surface of the modified electrode. Moreover, the newly developed nanoaptasensor embraces a number of attractive features such as ease of fabrication, low detection limit, excellent selectivity, good stability and a wide linear range with respect to IBP. Meanwhile, interference of common interfering analgesic drugs was effectively avoided. In optimized empirical conditions, the response current of the nanoaptasensor is linear to IBP concentrations from 0.005 nmol(-1) to 7 nmol(-1) with the detection limit (LOD) as accurate as 0.5 pmol(-1). This LOD value proves more sensitive in comparison with previously reported methods. Thus, the fabricated nanoaptasensor can serve as a powerful sensor for rapid diagnosis of IBP in human blood samples and shows great potential for practical bioapplication.

  14. Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing.

    PubMed

    Nandini, Seetharamaiah; Nalini, Seetharamaiah; Reddy, M B Madhusudana; Suresh, Gurukar Shivappa; Melo, Jose Savio; Niranjana, Pathappa; Sanetuntikul, Jakkid; Shanmugam, Sangaraju

    2016-08-01

    This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting β-diphenylalanine (β-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples.

  15. Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing.

    PubMed

    Nandini, Seetharamaiah; Nalini, Seetharamaiah; Reddy, M B Madhusudana; Suresh, Gurukar Shivappa; Melo, Jose Savio; Niranjana, Pathappa; Sanetuntikul, Jakkid; Shanmugam, Sangaraju

    2016-08-01

    This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting β-diphenylalanine (β-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples. PMID:27100467

  16. Surface science and electrochemical studies of metal-modified carbides for fuel cells and hydrogen production

    NASA Astrophysics Data System (ADS)

    Kelly, Thomas Glenn

    Carbides of the early transition metals have emerged as low-cost catalysts that are active for a wide range of reactions. The surface chemistry of carbides can be altered by modifying the surface with small amounts of admetals. These metal-modified carbides can be effective replacements for Pt-based bimetallic systems, which suffer from the drawbacks of high cost and low thermal stability. In this dissertation, metal-modified carbides were studied for reactions with applications to renewable energy technologies. It is demonstrated that metal-modified carbides possess high activity for alcohol reforming and electrochemical hydrogen production. First, the surface chemistry of carbides towards alcohol decomposition is studied using density functional theory (DFT) and surface science experiments. The Vienna Ab initio Simulation Package (VASP) was used to calculate the binding energies of alcohols and decomposition intermediates on metal-modified carbides. The calculated binding energies were then correlated to reforming activity determined experimentally using temperature programmed desorption (TPD). In the case of methanol decomposition, it was found that tungsten monocarbide (WC) selectively cleaved the C-O bond to produce methane. Upon modifying the surface with a single layer of metal such as Ni, Pt, or Rh, the selectivity shifted towards scission of the C-H bonds while leaving the C-O bond intact, producing carbon monoxide (CO) and H2. High resolution energy loss spectroscopy (HREELS) was used to examine the bond breaking sequence as a function of temperature. From HREELS, it was shown that the surfaces followed an activity trend of Rh > Ni > Pt. The Au-modified WC surface possessed too low of a methanol binding energy, and molecular desorption of methanol was the most favorable pathway on this surface. Next, the ability of Rh-modified WC to break the C-C bond of C2 and C3 alcohols was demonstrated. HREELS showed that ethanol decomposed through an acetaldehyde

  17. A continuous glucose monitoring device by graphene modified electrochemical sensor in microfluidic system.

    PubMed

    Pu, Zhihua; Zou, Chongwei; Wang, Ridong; Lai, Xiaochen; Yu, Haixia; Xu, Kexin; Li, Dachao

    2016-01-01

    This paper presents a continuous glucose monitoring microsystem consisting of a three-electrode electrochemical sensor integrated into a microfluidic chip. The microfluidic chip, which was used to transdermally extract and collect subcutaneous interstitial fluid, was fabricated from five polydimethylsiloxane layers using micromolding techniques. The electrochemical sensor was integrated into the chip for continuous detection of glucose. Specifically, a single-layer graphene and gold nanoparticles (AuNPs) were decorated onto the working electrode (WE) of the sensor to construct a composite nanostructured surface and improve the resolution of the glucose measurements. Graphene was transferred onto the WE surface to improve the electroactive nature of the electrode to enable measurements of low levels of glucose. The AuNPs were directly electrodeposited onto the graphene layer to improve the electron transfer rate from the activity center of the enzyme to the electrode to enhance the sensitivity of the sensor. Glucose oxidase (GOx) was immobilized onto the composite nanostructured surface to specifically detect glucose. The factors required for AuNPs deposition and GOx immobilization were also investigated, and the optimized parameters were obtained. The experimental results displayed that the proposed sensor could precisely measure glucose in the linear range from 0 to 162 mg/dl with a detection limit of 1.44 mg/dl (S/N = 3). The proposed sensor exhibited the potential to detect hypoglycemia which is still a major challenge for continuous glucose monitoring in clinics. Unlike implantable glucose sensors, the wearable device enabled external continuous monitoring of glucose without interference from foreign body reaction and bioelectricity. PMID:26958097

  18. A continuous glucose monitoring device by graphene modified electrochemical sensor in microfluidic system.

    PubMed

    Pu, Zhihua; Zou, Chongwei; Wang, Ridong; Lai, Xiaochen; Yu, Haixia; Xu, Kexin; Li, Dachao

    2016-01-01

    This paper presents a continuous glucose monitoring microsystem consisting of a three-electrode electrochemical sensor integrated into a microfluidic chip. The microfluidic chip, which was used to transdermally extract and collect subcutaneous interstitial fluid, was fabricated from five polydimethylsiloxane layers using micromolding techniques. The electrochemical sensor was integrated into the chip for continuous detection of glucose. Specifically, a single-layer graphene and gold nanoparticles (AuNPs) were decorated onto the working electrode (WE) of the sensor to construct a composite nanostructured surface and improve the resolution of the glucose measurements. Graphene was transferred onto the WE surface to improve the electroactive nature of the electrode to enable measurements of low levels of glucose. The AuNPs were directly electrodeposited onto the graphene layer to improve the electron transfer rate from the activity center of the enzyme to the electrode to enhance the sensitivity of the sensor. Glucose oxidase (GOx) was immobilized onto the composite nanostructured surface to specifically detect glucose. The factors required for AuNPs deposition and GOx immobilization were also investigated, and the optimized parameters were obtained. The experimental results displayed that the proposed sensor could precisely measure glucose in the linear range from 0 to 162 mg/dl with a detection limit of 1.44 mg/dl (S/N = 3). The proposed sensor exhibited the potential to detect hypoglycemia which is still a major challenge for continuous glucose monitoring in clinics. Unlike implantable glucose sensors, the wearable device enabled external continuous monitoring of glucose without interference from foreign body reaction and bioelectricity.

  19. Magnetic Bead/Gold Nanoparticle Double-Labeled Primers for Electrochemical Detection of Isothermal Amplified Leishmania DNA.

    PubMed

    de la Escosura-Muñiz, Alfredo; Baptista-Pires, Luis; Serrano, Lorena; Altet, Laura; Francino, Olga; Sánchez, Armand; Merkoçi, Arben

    2016-01-13

    A novel methodology for the isothermal amplification of Leishmania DNA using labeled primers combined with the advantages of magnetic purification/preconcentration and the use of gold nanoparticle (AuNP) tags for the sensitive electrochemical detection of such amplified DNA is developed. Primers labeled with AuNPs and magnetic beads (MBs) are used for the first time for the isothermal amplification reaction, being the amplified product ready for the electrochemical detection. The electrocatalytic activity of the AuNP tags toward the hydrogen evolution reaction allows the rapid quantification of the DNA on screen-printed carbon electrodes. Amplified products from the blood of dogs with Leishmania (positive samples) are discriminated from those of healthy dogs (blank samples). Quantitative studies demonstrate that the optimized method allows us to detect less than one parasite per microliter of blood (8 × 10(-3) parasites in the isothermal amplification reaction). This pioneering approach is much more sensitive than traditional methods based on real-time polymerase chain reaction (PCR), and is also more rapid, cheap, and user-friendly.

  20. Construction of an Electrochemical Sensor Based on Carbon Nanotubes/Gold Nanoparticles for Trace Determination of Amoxicillin in Bovine Milk.

    PubMed

    Muhammad, Aliyu; Yusof, Nor Azah; Hajian, Reza; Abdullah, Jaafar

    2016-01-20

    In this work, a novel electrochemical sensor was fabricated for determination of amoxicillin in bovine milk samples by decoration of carboxylated multi-walled carbon nanotubes (MWCNTs) with gold nanoparticles (AuNPs) using ethylenediamine (en) as a cross linker (AuNPs/en-MWCNTs). The constructed nanocomposite was homogenized in dimethylformamide and drop casted on screen printed electrode. Field emission scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX), X-Ray diffraction (XRD) and cyclic voltammetry were used to characterize the synthesized nanocomposites. The results show that the synthesized nanocomposites induced a remarkable synergetic effect for the oxidation of amoxicillin. Effect of some parameters, including pH, buffer, scan rate, accumulation potential, accumulation time and amount of casted nanocomposites, on the sensitivity of fabricated sensor were optimized. Under the optimum conditions, there was two linear calibration ranges from 0.2-10 µM and 10-30 µM with equations of Ipa (µA) = 2.88C (µM) + 1.2017; r = 0.9939 and Ipa (µA) = 0.88C (µM) + 22.97; r = 0.9973, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were calculated as 0.015 µM and 0.149 µM, respectively. The fabricated electrochemical sensor was successfully applied for determination of Amoxicillin in bovine milk samples and all results compared with high performance liquid chromatography (HPLC) standard method.

  1. Selective detection of silver ions using mushroom-like polyaniline and gold nanoparticle nanocomposite-based electrochemical DNA sensor.

    PubMed

    Yang, Yanqin; Zhang, Shuai; Kang, Mengmeng; He, Linghao; Zhao, Jihong; Zhang, Hongzhong; Zhang, Zhihong

    2015-12-01

    A highly sensitive electrochemical DNA biosensor made of polyaniline (PANI) and gold nanoparticles (AuNPs) nanocomposite (AuNPs@PANI) has been used for the detection of trace concentration of Ag(+). In the presence of Ag(+), with the interaction of cytosine-Ag(+)-cytosine (C-Ag(+)-C), cytosine-rich DNA sequence immobilized onto the surface of AuNPs@PANI has a self-hybridization and then forms a duplex-like structure. The whole detection procedure of Ag(+) based on the developed biosensor was evaluated by electrochemical impedance spectroscopy. On semi-logarithmic plots of the log Ag(+) concentration versus peak current, the results show that the prepared biosensor can detect silver ions at a wide linear range of 0.01-100 nM (R = 0.9828) with a detection limit of 10 pM (signal/noise = 3). Moreover, the fabricated sensor exhibits good selectivity and repeatability. The detection of Ag(+) was determined by Ag(+) self-induced conformational change of DNA scaffold that involved only one oligonucleotide, showing its convenience and availability. PMID:26292168

  2. Construction of an Electrochemical Sensor Based on Carbon Nanotubes/Gold Nanoparticles for Trace Determination of Amoxicillin in Bovine Milk

    PubMed Central

    Muhammad, Aliyu; Yusof, Nor Azah; Hajian, Reza; Abdullah, Jaafar

    2016-01-01

    In this work, a novel electrochemical sensor was fabricated for determination of amoxicillin in bovine milk samples by decoration of carboxylated multi-walled carbon nanotubes (MWCNTs) with gold nanoparticles (AuNPs) using ethylenediamine (en) as a cross linker (AuNPs/en-MWCNTs). The constructed nanocomposite was homogenized in dimethylformamide and drop casted on screen printed electrode. Field emission scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX), X-Ray diffraction (XRD) and cyclic voltammetry were used to characterize the synthesized nanocomposites. The results show that the synthesized nanocomposites induced a remarkable synergetic effect for the oxidation of amoxicillin. Effect of some parameters, including pH, buffer, scan rate, accumulation potential, accumulation time and amount of casted nanocomposites, on the sensitivity of fabricated sensor were optimized. Under the optimum conditions, there was two linear calibration ranges from 0.2–10 µM and 10–30 µM with equations of Ipa (µA) = 2.88C (µM) + 1.2017; r = 0.9939 and Ipa (µA) = 0.88C (µM) + 22.97; r = 0.9973, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were calculated as 0.015 µM and 0.149 µM, respectively. The fabricated electrochemical sensor was successfully applied for determination of Amoxicillin in bovine milk samples and all results compared with high performance liquid chromatography (HPLC) standard method. PMID:26805829

  3. Single domain antibody coated gold nanoparticles as enhancer for Clostridium difficile toxin detection by electrochemical impedance immunosensors

    PubMed Central

    Zhu, Zanzan; Shi, Lianfa; Feng, Hanping; Zhou, H. Susan

    2016-01-01

    This work presents a sandwich-type electrochemical impedance immunosensor for detecting Clostridium difficile toxin A (TcdA) and toxin B (TcdB). Single domain antibody conjugated gold nanoparticles were applied to amplify the detection signal. Gold nanoparticles (Au NPs) were characterized by transmission electron microscopy and UV–vis spectra. The electron transfer resistance (Ret) of the working electrode surface was used as a parameter in the measurement of the biosensor. With the increase of the concentration of toxins from 1 pg/mL to 100 pg/mL, a linear relationship was observed between the relative electron transfer resistance and toxin concentration. In addition, the detection signal was enhanced due to the amplification effect. The limit of detection for TcdA and TcdB was found to be 0.61 pg/mL and 0.60 pg/mL respectively at a signal-to-noise ratio of 3 (S/N = 3). This method is simple, fast and ultrasensitive, thus possesses a great potential for clinical applications in the future. PMID:25460611

  4. Enhanced catalysis of the electrochemical hydrogen evolution reaction using composites of molybdenum-based compounds, gold nanoparticles and carbon.

    PubMed

    Joshi, Ubisha; Lee, Jing; Giordano, Cristina; Malkhandi, Souradip; Yeo, Boon Siang

    2016-08-21

    Molybdenum nitride has been recently reported to interact synergistically with gold to show an enhanced activity for the electrochemical hydrogen evolution reaction (2H(+) + 2e(-)→ H2, HER). In this work, we elucidated the roles of nitrogen, carbon, molybdenum and gold on this observed phenomenon. Composites of Mo-based compounds, carbon black (black pearl 2000) and/or Au nanoparticles (AuNP) were prepared, and their activities for the HER in a 0.5 M H2SO4 electrolyte were measured using linear sweep voltammetry. We show and discuss here for the first time that, while the presence of carbon is necessary for the synergy phenomenon, the nitrogen atoms present in the compounds play no apparent role in this synergy. In fact, all the compounds containing Mo, namely Mo2N, MoB and metallic Mo(0), exhibited extensive synergy with Au for the HER. A hypothesis for the enhanced catalysis of H2 evolution by the mixed metal composites is proposed and discussed. PMID:27424516

  5. Electrochemical oxidation of borohydride at nano-gold-based electrodes: Application in direct borohydride fuel cells

    NASA Astrophysics Data System (ADS)

    Coowar, Fazlil A.; Vitins, Girts; Mepsted, Gary O.; Waring, Susan C.; Horsfall, Jacqueline A.

    Nano-particulate gold-based materials along with commercial gold supported over carbon were investigated as possible alternative electrocatalysts for the oxidation of borohydride in alkaline media. Cyclic voltammetry experiments conducted on these materials show very high activity for the nano-particulate materials compared to the commercial materials despite a lower loading of gold (0.8 mg cm -2 compared to 1.0 mg cm -2) and lower interface area in the nano-particulate materials. The presence of BH 4 - appears to have detrimental effect on the performances of the air-electrode for oxygen reduction. The current density recorded at -0.6 V versus Hg/HgO has decreased by a factor of six for silver nitrate AC65 while for MnO 2 a reduction in the current density by a factor of two only was observed. The implementation of the nano-particulate gold-based materials and the air-electrodes along with a low-cost anionic membrane in QinetiQ's tubular cell design has led to power density exceeding 28 mW cm -2 obtained at ambient temperature.

  6. ELECTROCHEMICALLY DEPOSITED POLYMER-COATED GOLD ELECTRODES SELECTIVE FOR 2,4-DICHLOROPHENOXYACETIC ACID

    EPA Science Inventory

    Electropolymerized membranes on gold electrodes doped with 2,4-dichlorophenoxyacetic acid (2,4-D) were prepared from a solution containing resorcinol, o-phenylenediamine and 2,4-D. Fourier Transform Infrared (FTIR) spectroscopy was used to evaluate the incorporation and interact...

  7. Multidentate zwitterionic chitosan oligosaccharide modified gold nanoparticles: stability, biocompatibility and cell interactions

    NASA Astrophysics Data System (ADS)

    Liu, Xiangsheng; Huang, Haoyuan; Liu, Gongyan; Zhou, Wenbo; Chen, Yangjun; Jin, Qiao; Ji, Jian

    2013-04-01

    Surface engineering of nanoparticles plays an essential role in their colloidal stability, biocompatibility and interaction with biosystems. In this study, a novel multidentate zwitterionic biopolymer derivative is obtained from conjugating dithiolane lipoic acid and zwitterionic acryloyloxyethyl phosphorylcholine to the chitosan oligosaccharide backbone. Gold nanoparticles (AuNPs) modified by this polymer exhibit remarkable colloidal stabilities under extreme conditions including high salt conditions, wide pH range and serum or plasma containing media. The AuNPs also show strong resistance to competition from dithiothreitol (as high as 1.5 M). Moreover, the modified AuNPs demonstrate low cytotoxicity investigated by both MTT and LDH assays, and good hemocompatibility evaluated by hemolysis of human red blood cells. In addition, the intracellular fate of AuNPs was investigated by ICP-MS and TEM. It showed that the AuNPs are uptaken by cells in a concentration dependent manner, and they can escape from endosomes/lysosomes to cytosol and tend to accumulate around the nucleus after 24 h incubation but few of them are excreted out of the cells. Gold nanorods are also stabilized by this ligand, which demonstrates robust dispersion stability and excellent hemocompatibility. This kind of multidentate zwitterionic chitosan derivative could be widely used for stabilizing other inorganic nanoparticles, which will greatly improve their performance in a variety of bio-related applications.Surface engineering of nanoparticles plays an essential role in their colloidal stability, biocompatibility and interaction with biosystems. In this study, a novel multidentate zwitterionic biopolymer derivative is obtained from conjugating dithiolane lipoic acid and zwitterionic acryloyloxyethyl phosphorylcholine to the chitosan oligosaccharide backbone. Gold nanoparticles (AuNPs) modified by this polymer exhibit remarkable colloidal stabilities under extreme conditions including high salt

  8. Colorimetric Detection of Cadmium Ions Using DL-Mercaptosuccinic Acid-Modified Gold Nanoparticles.

    PubMed

    Chen, Na; Chen, Jun; Yang, Jing-Hua; Bai, Lian-Yang; Zhang, Yu-Ping

    2016-01-01

    A colorimetric assay has been developed for detection of Cd²⁺ utilizing DL-mercaptosuccinic acid-modified gold nanoparticles (MSA-AuNPs). The method showed good selectivity for Cd²⁺ over other metal ions. As a result, the linear relationships (r > 0.9606) between concentration 0.07 mM and 0.20 mM for cadmium ion were obtained. The detection limit was as low as 0.07 mM by the naked eye. The effect of pH on the aggregation was optimized. The MSA-AuNPs probe could be used to detect Cd²⁺ in an aqueous solution based on the aggregation-induced color change of MSA-AuNPs. PMID:27398533

  9. Accelerated colorimetric immunosensing using surface-modified porous monoliths and gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Chuag, Shao-Hsuan; Chen, Guan-Hua; Chou, Hsin-Hao; Shen, Shu-Wei; Chen, Chien-Fu

    2013-08-01

    A rapid and sensitive immunoassay platform integrating polymerized monoliths and gold nanoparticles (AuNPs) has been developed. The porous monoliths are photopolymerized in situ within a silica capillary and serve as solid support for high-mass transport and high-density capture antibody immobilization to create a shorter diffusion length for antibody-antigen interactions, resulting in a rapid assay and low reagent consumption. AuNPs are modified with detection antibodies and are utilized as signals for colorimetric immunoassays without the need for enzyme, substrate and sophisticated equipment for quantitative measurements. This platform has been verified by performing a human IgG sandwich immunoassay with a detection limit of 0.1 ng ml-1. In addition, a single assay can be completed in 1 h, which is more efficient than traditional immunoassays that require several hours to complete.

  10. Electrochemical Investigation of Interaction between a Bifunctional Probe and GG Mismatch Duplex.

    PubMed

    Li, Jiao; He, Hanping; Peng, Xiaoqian; Huang, Min; Zhang, Xiuhua; Wang, Shengfu

    2015-01-01

    A bifunctional probe (FecNC), containing a recognition part and an electrochemical active center, was applied to electrochemical detection of GG mismatch duplexes. The preparation of gold electrodes modified by mismatch and complementatry duplexes was characterized by electrochemical impedance spectroscopy (EIS) and optimized for better detection in terms of self-assembly time, hybridization time, and incubation time. The interaction between FecNC and DNA duplexes modified on the surface of a gold electrode was explored by square wave voltammetry (SWV) and EIS. The results showed that the DNA duplexes with GG mismatch on the surface of a gold electrode was easily detected by the largest electrochemical signal of the bifunctional probe because of its selective binding to GG mismatches. The bifunctional probe could offer a simple, effective electrochemical detection of GG mismatches, and theoretical bases for development of electrochemical biosensors. Further, the method would be favorable for diagnosis of genetic diseases. PMID:26165289

  11. Electrochemical Investigation of Interaction between a Bifunctional Probe and GG Mismatch Duplex.

    PubMed

    Li, Jiao; He, Hanping; Peng, Xiaoqian; Huang, Min; Zhang, Xiuhua; Wang, Shengfu

    2015-01-01

    A bifunctional probe (FecNC), containing a recognition part and an electrochemical active center, was applied to electrochemical detection of GG mismatch duplexes. The preparation of gold electrodes modified by mismatch and complementatry duplexes was characterized by electrochemical impedance spectroscopy (EIS) and optimized for better detection in terms of self-assembly time, hybridization time, and incubation time. The interaction between FecNC and DNA duplexes modified on the surface of a gold electrode was explored by square wave voltammetry (SWV) and EIS. The results showed that the DNA duplexes with GG mismatch on the surface of a gold electrode was easily detected by the largest electrochemical signal of the bifunctional probe because of its selective binding to GG mismatches. The bifunctional probe could offer a simple, effective electrochemical detection of GG mismatches, and theoretical bases for development of electrochemical biosensors. Further, the method would be favorable for diagnosis of genetic diseases.

  12. Antibody modified gold nanoparticles for fast and selective, colorimetric T7 bacteriophage detection.

    PubMed

    Lesniewski, Adam; Los, Marcin; Jonsson-Niedziółka, Martin; Krajewska, Anna; Szot, Katarzyna; Los, Joanna M; Niedziolka-Jonsson, Joanna

    2014-04-16

    Herein, we report a colorimetric immunosensor for T7 bacteriophage based on gold nanoparticles modified with covalently bonded anti-T7 antibodies. The new immunosensor allows for a fast, simple, and selective detection of T7 virus. T7 virions form immunological complexes with the antibody modified gold nanoparticles which causes them to aggregate. The aggregation can be observed with the naked eye as a color change from red to purple, as well as with a UV-vis spectrophotometer. The aggregate formation was confirmed with SEM imaging. Sensor selectivity against the M13 bacteriophage was demonstrated. The limit of detection (LOD) is 1.08 × 10(10) PFU/mL (18 pM) T7. The new method was compared with a traditional plaque test. In contrast to biological tests the colorimetric method allows for detection of all T7 phages, not only those biologically active. This includes phage ghosts and fragments of virions. T7 virus has been chosen as a model organism for adenoviruses. The described method has several advantages over the traditional ones. It is much faster than a standard plaque test. It is more robust since no bacteria-virus interactions are utilized in the detection process. Since antibodies are available for a large variety of pathogenic viruses, the described concept is very flexible and can be adapted to detect many different viruses, not only bacteriophages. Contrary to the classical immunoassays, it is a one-step detection method, and no additional amplification, e.g., enzymatic, is needed to read the result.

  13. Colorimetric sensing strategy for mercury(II) and melamine utilizing cysteamine-modified gold nanoparticles.

    PubMed

    Ma, Yujie; Jiang, Ling; Mei, Yajun; Song, Rongbin; Tian, Danbi; Huang, He

    2013-09-21

    A quantitative colorimetric sensing strategy utilizing cysteamine modified gold nanoparticles (CA-AuNPs) as reporters for Hg(2+) and melamine was demonstrated. Cysteamine is a cheap and commercially available aminothiol and is also the most important chelating ligand in coordination chemistry possessing the ability to coordinate to Hg(2+) and melamine. The terminal thiol group in cysteamine is used to bind to AuNPs and another terminal amine group is used as a colorimetric probe either for Hg(2+) or melamine. By adjusting the pH, protonation of cysteamine's terminal amine groups allows for tuning of the surface charge on the cysteamine-modified gold nanoparticles. At acidic pH, the CA-AuNPs are positively charged due to the protonated amine groups, which may electrostatically bind melamine resulting in aggregation of CA-AuNPs, while at alkaline pH, the amine groups are deprotonated, and if Hg(2+) is present, they may form an N-Hg(2+)-N structure to induce the aggregation of CA-AuNPs. The detection limits (S/N = 3) of Hg(2+) and melamine were 30 nM and 80 nM respectively, which were comparable with or even lower than those of other single analyte methods. The proposed sensing mechanisms, which are based on electrostatic attraction for melamine and the N-Hg(2+)-N structure for Hg(2+), were validated by zeta potential measurements. The facile one-step surface modification strategy for AuNPs is suitable for the effective analysis of large numbers of samples, which would open new opportunities for development of miniaturized Hg(2+) and melamine sensors.

  14. Rapid quantitative detection of Brucella melitensis by a label-free impedance immunosensor based on a gold nanoparticle-modified screen-printed carbon electrode.

    PubMed

    Wu, Haiyun; Zuo, Yueming; Cui, Chuanjin; Yang, Wei; Ma, Haili; Wang, Xiaowen

    2013-07-04

    A rapid and simple method for quantitative monitoring of Brucella melitensis using electrochemical impedance spectroscopy (EIS) is reported for the first time. The label-free immunosensors were fabricated by immobilizing Brucella melitensis antibody on the surface of gold nanoparticle-modified screen-printed carbon electrodes (GNP-SPCEs). Cyclic voltammetry (CV) and EIS were used to characterize the Brucella melitensis antigen interaction on the surface of GNP-SPCEs with antibody. A general electronic equivalent model of an electrochemical cell was introduced for interpretation of the impedance components of the system. The results showed that the change in electron-transfer resistance (Rct) was significantly different due to the binding of Brucella melitensis cells. A linear relationship between the Rct variation and logarithmic value of the cell concentration was found from 4 × 10(4) to 4 × 10(6) CFU/mL in pure culture. The label-free impedance biosensor was able to detect as low as 1 × 10(4) and 4 × 10(5) CFU/mL of Brucella melitensis in pure culture and milk samples, respectively, in less than 1.5 h. Moreover, a good selectivity versus Escherichia coli O157:H7 and Staphylococcus aureus cells was obtained for our developed immunosensor demonstrating its specificity towards only Brucella melitensis.

  15. Highly sensitive determination of sunset yellow FCF (E110) in food products based on Chitosan/Nanoparticles/MWCNTs with modified gold electrode

    NASA Astrophysics Data System (ADS)

    Rovina, K.; Siddiquee, S.; Shaarani, S. M.

    2016-06-01

    Sunset Yellow belongs to the family of azo dyes, commonly used in food industry. High consumption of Sunset Yellow can cause health problem to human. Due to arising of the health issues, there are several analytical methods available for determination of Sunset Yellow. However, these methods are required skilled manpower, complicated procedures, time consuming and high cost. Herein, an electrochemical sensor was developed based on the combination of chitosan (CHIT), calcium oxide nanoparticles (CaONPs) and multiwall carbon nanotubes (MWCNTs) sensing film for detection of Sunset Yellow in food products. Electrochemical behavior of the modified gold electrode in the presence of Sunset Yellow was studied by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The morphological characteristics of CHIT/CaONPs/MWCNTs were observed under scanning electron microscope and transmission electron microscope. Under optimal conditions, the DPV was detected with different concentrations of Sunset Yellow in the range of 0.9 to 10 ppm, with detection limit of 0.8 ppm. The developed method has successfully applied for monitoring the presence of Sunset Yellow with different food products including candy, royal jelly, ice cream and soft drink with satisfactory results.

  16. Facile fabrication of a novel anisotropic gold nanoparticle-chitosan-ionic liquid/graphene modified electrode for the determination of theophylline and caffeine.

    PubMed

    Yang, Guangming; Zhao, Faqiong; Zeng, Baizhao

    2014-09-01

    In the present study, a suspension solution containing anisotropic gold nanoparticle (GNP), chitosan (CHIT) and ionic liquid (IL, i.e. 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]), is prepared by reducing HAuCl4 with sodium citrate in CHIT-IL aqueous solution. The hybrid solution is coated on a graphene (r-GO) modified glassy carbon electrode to construct an electrochemical sensor for the determination of theophylline (TP) and caffeine (CAF). The obtained hybrid film shows rough surface, and anisotropic GNPs are well dispersed on it. The factors concerning this assay strategy are carefully investigated, including the components of the hybrid film, the concentrations of r-GO, HAuCl4 and IL, and the pH of buffer solution. Under the optimized conditions, the linear response ranges are 2.50×10(-8)-2.10×10(-6) mol L(-1) and 2.50×10(-8)-2.49×10(-6) mol L(-1) for TP and CAF, respectively; the detection limits are 1.32×10(-9) mol L(-1) and 4.42×10(-9) mol L(-1), respectively. The electrochemical sensor shows good reproducibility, stability and selectivity, and it has been successfully applied to the determination of TP and CAF in real samples.

  17. Gold electrode modified with a self-assembled glucose oxidase and 2,6-pyridinedicarboxylic acid as novel glucose bioanode for biofuel cells

    NASA Astrophysics Data System (ADS)

    Ammam, Malika; Fransaer, Jan

    2014-07-01

    In this study, we have constructed a gold electrode modified with (3-aminopropyl)trimethoxysilane/2,6-pyridinedicarboxylic acid/glucose oxidase (abbreviated as, Au/ATS/PDA/GOx) by sequential chemical adsorption. Au/ATS/PDA/GOx electrode was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Electrochemical Impedance Spectroscopy (EIS). The data from FT-IR illustrated deposition of ATS, PDA and GOx on the surface of gold electrode. The latter has been confirmed by EIS which showed that the electron transfer resistance of the electrode increases after adsorption of each supplementary layer. Linear sweep voltammetry (LSV) in phosphate buffer solution containing 5 mM glucose displayed that compared to Au/ATS/GOx, oxidation of glucose at Au/ATS/PDA/GOx electrode starts 461 mV earlier. This gain in potential is attributed to presence of PDA in the constructed Au/ATS/PDA/GOx electrode, which plays some sort of electron mediator for glucose oxidation. The Au/ATS/PDA/GOx electrode was stabilized by an outer layer of polystyrene sulfonate (PSS) and was connected to a Pt electrode as cathode and the non-compartmentalized cell was studied under air in phosphate buffer solution pH 7.4 containing 10 mM glucose. Under these conditions, the maximum power density reaches 0.25 μW mm-2 (25 μW cm-2) for the deposited GOx layer that has an estimated surface coverage of ∼70% of a monolayer.

  18. Acetylcholinesterase biosensor based on a gold nanoparticle-polypyrrole-reduced graphene oxide nanocomposite modified electrode for the amperometric detection of organophosphorus pesticides.

    PubMed

    Yang, Yuqi; Asiri, Abdullah Mohamed; Du, Dan; Lin, Yuehe

    2014-06-21

    A nanohybrid of gold nanoparticles, polypyrrole, and reduced graphene oxide sheets (named as Au-PPy-rGO) was achieved by electrochemical deposition of reduced graphene oxide with pyrrole and the introduction of gold nanoparticles. Acetylcholinesterase (AChE) was further encapsulated in a silica matrix and immobilized on the Au-PPy-rGO nanocomposite by co-deposition with (NH4)2SiF6. The presence of PPy helped to avoid the aggregation of rGO caused by van der Waals interactions between individual sheets and significantly increased the surface area of the modified electrode. The obtained Au-PPy-rGO nanocomposite not only showed excellent conductivity but also exhibited a high electrocatalytic activity and specific affinity for thiocholine, the hydrolysis product of the enzyme, and thus an improved detection sensitivity. Since AChE molecules were protected by the circumambient silica matrix, which provided a biocompatible environment and facilitated mass transport, the fabricated AChE biosensor displayed high stability and excellent activity together with a fast response to organophosphorus pesticides. Under optimum conditions, the biosensor led to the rapid and sensitive detection of paraoxon-ethyl from 1.0 nM to 5 μM with a detection limit of 0.5 nM.

  19. Sensitive voltammetric determination of chloramphenicol by using single-wall carbon nanotube-gold nanoparticle-ionic liquid composite film modified glassy carbon electrodes.

    PubMed

    Xiao, Fei; Zhao, Faqiong; Li, Jiangwen; Yan, Rui; Yu, Jingjing; Zeng, Baizhao

    2007-07-16

    A novel composite film modified glassy carbon electrode has been fabricated and characterized by scanning electron microscope (SEM) and voltammetry. The composite film comprises of single-wall carbon nanotube (SWNT), gold nanoparticle (GNP) and ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophosphate), thus has the characteristics of them. The resulting electrode shows good stability, high accumulation efficiency and strong promotion to electron transfer. On it, chloramphenicol can produce a sensitive cathodic peak at -0.66 V (versus SCE) in pH 7.0 phosphate buffer solutions. Parameters influencing the voltammetric response of chloramphenicol are optimized, which include the composition of the film and the operation conditions. Under the optimized conditions, the peak current is linear to chloramphenicol concentration in the range of 1.0x10(-8)-6.0x10(-6) M, and the detection limit is estimated to be 5.0x10(-9) M after an accumulation for 150 s on open circuit. The electrode is applied to the determination of chloramphenicol in milk samples, and the recoveries for the standards added are 97.0% and 100.3%. In addition, the electrochemical reaction of chloramphenicol and the effect of single-wall carbon nanotube, gold nanoparticle and ionic liquid are discussed.

  20. Controllable Synthesis of Formaldehyde Modified Manganese Oxide Based on Gas-Liquid Interfacial Reaction and Its Application of Electrochemical Sensing.

    PubMed

    Bai, Wushuang; Sheng, Qinglin; Nie, Fei; Zheng, Jianbin

    2015-12-30

    Controllable synthesis of manganese oxides was performed via a simple one-step synthetic method. Then obtained manganese oxides which exhibit flower-like, cloud-like, hexagon-like, and rod-like morphologies were modified by formaldehyde based on a simple self-made gas-liquid reaction device respectively and the modified manganese oxides with coral-like, scallop-like and rod-like morphology were synthesized accordingly. The obtained materials were characterized and the formation mechanism was also researched. Then the modified manganese oxides were used to fabricate electrochemical sensors to detect H2O2. Comparison of electrochemical properties between three kinds of modified manganese oxides was investigated and the best one has been successfully employed as H2O2 sensor which shows a low detection limit of 0.01 μM, high sensitivity of 162.69 μA mM(-1) cm(-2), and wide linear range of 0.05 μM-12.78 mM. The study provides a new method for controllable synthesis of metal oxides, and electrochemical application of formaldehyde modified manganese oxides will provides a new strategy for electrochemical sensing with high performance, low cost, and simple fabrication. PMID:26647786

  1. Controllable Synthesis of Formaldehyde Modified Manganese Oxide Based on Gas-Liquid Interfacial Reaction and Its Application of Electrochemical Sensing.

    PubMed

    Bai, Wushuang; Sheng, Qinglin; Nie, Fei; Zheng, Jianbin

    2015-12-30

    Controllable synthesis of manganese oxides was performed via a simple one-step synthetic method. Then obtained manganese oxides which exhibit flower-like, cloud-like, hexagon-like, and rod-like morphologies were modified by formaldehyde based on a simple self-made gas-liquid reaction device respectively and the modified manganese oxides with coral-like, scallop-like and rod-like morphology were synthesized accordingly. The obtained materials were characterized and the formation mechanism was also researched. Then the modified manganese oxides were used to fabricate electrochemical sensors to detect H2O2. Comparison of electrochemical properties between three kinds of modified manganese oxides was investigated and the best one has been successfully employed as H2O2 sensor which shows a low detection limit of 0.01 μM, high sensitivity of 162.69 μA mM(-1) cm(-2), and wide linear range of 0.05 μM-12.78 mM. The study provides a new method for controllable synthesis of metal oxides, and electrochemical application of formaldehyde modified manganese oxides will provides a new strategy for electrochemical sensing with high performance, low cost, and simple fabrication.

  2. Mediatorless sugar/oxygen enzymatic fuel cells based on gold nanoparticle-modified electrodes.

    PubMed

    Wang, Xiaoju; Falk, Magnus; Ortiz, Roberto; Matsumura, Hirotoshi; Bobacka, Johan; Ludwig, Roland; Bergelin, Mikael; Gorton, Lo; Shleev, Sergey

    2012-01-15

    We report on the fabrication and characterisation of a gold-nanoparticle (AuNP)-based mediatorless sugar/oxygen biofuel cell (BFC) operating in neutral sugar-containing buffers and human physiological fluids, such as blood and plasma. First, Corynascus thermophilus cellobiose dehydrogenase (CtCDH) and Myrothecium verrucaria bilirubin oxidase (MvBOx), used as anodic and cathodic bioelements, respectively, were immobilised on gold electrodes modified with 20 nm AuNPs. Detailed characterisation and optimisation of a new CDH/AuNP-based bioanode were performed and the following fundamental parameters were obtained: (i) the redox potential of the haem-containing centre of the enzyme was measured to be 75 mV vs. NHE, (ii) the surface coverage of CtCDH was found to be 0.65 pmol cm(-2) corresponding to a sub-monolayer coverage of the thiol-modified AuNPs by the enzyme, (iii) a turnover number for CtCDH immobilised on thiol-modified AuNPs was calculated to be ca. 0.5 s(-1), and (iv) the maximal current densities as high as 40 μA cm(-2) were registered in sugar-containing neutral buffers. Second, both biomodified electrodes, namely the CtCDH/AuNP-based bioanode and the MvBOx/AuNP-based biocathode, were combined into a functional BFC and the designed biodevices were carefully investigated. The following characteristics of the mediator-, separator- and membrane-less, miniature BFC were obtained: in phosphate buffer; an open-circuit voltage of 0.68 V, a maximum power density of 15 μW cm(-2) at a cell voltage of 0.52 V and in human blood; an open-circuit voltage of 0.65 V, a maximum power density of 3 μW cm(-2) at a cell voltage of 0.45 V, respectively. The estimated half-lives of the biodevices were found to be >12, <8, and <2 h in a sugar-containing buffer, human plasma, and blood, respectively. The basic characteristics of mediatorless sugar/oxygen BFCs were significantly improved compared with previously designed biodevices, because of the usage of three-dimensional AuNP-modified

  3. Multiplex electrochemical DNA platform for femtomolar-level quantification of genetically modified soybean.

    PubMed

    Manzanares-Palenzuela, C Lorena; de-los-Santos-Álvarez, Noemí; Lobo-Castañón, María Jesús; López-Ruiz, Beatriz

    2015-06-15

    Current EU regulations on the mandatory labeling of genetically modified organisms (GMOs) with a minimum content of 0.9% would benefit from the availability of reliable and rapid methods to detect and quantify DNA sequences specific for GMOs. Different genosensors have been developed to this aim, mainly intended for GMO screening. A remaining challenge, however, is the development of genosensing platforms for GMO quantification, which should be expressed as the number of event-specific DNA sequences per taxon-specific sequences. Here we report a simple and sensitive multiplexed electrochemical approach for the quantification of Roundup-Ready Soybean (RRS). Two DNA sequences, taxon (lectin) and event-specific (RR), are targeted via hybridization onto magnetic beads. Both sequences are simultaneously detected by performing the immobilization, hybridization and labeling steps in a single tube and parallel electrochemical readout. Hybridization is performed in a sandwich format using signaling probes labeled with fluorescein isothiocyanate (FITC) or digoxigenin (Dig), followed by dual enzymatic labeling using Fab fragments of anti-Dig and anti-FITC conjugated to peroxidase or alkaline phosphatase, respectively. Electrochemical measurement of the enzyme activity is finally performed on screen-printed carbon electrodes. The assay gave a linear range of 2-250 pM for both targets, with LOD values of 650 fM (160 amol) and 190 fM (50 amol) for the event-specific and the taxon-specific targets, respectively. Results indicate that the method could be applied for GMO quantification below the European labeling threshold level (0.9%), offering a general approach for the rapid quantification of specific GMO events in foods. PMID:25590971

  4. Probing the electrochemical properties of biopolymer modified EMD nanoflakes through electrodeposition for high performance alkaline batteries.

    PubMed

    Biswal, Avijit; Minakshi, Manickam; Tripathy, Bankim Chandra

    2016-04-01

    In the present work, a novel biopolymer approach has been made to electrodeposit manganese dioxide from manganese sulphate in a sulphuric acid bath containing chitosan in the absence and presence of glutaraldehyde as a cross-linking agent. Galvanostatically synthesised electrolytic manganese dioxide (EMD) nanoflakes were used as electrode materials and their electrochemical properties with the influence of biopolymer chitosan were systematically characterized. The structural determination, surface morphology and porosity of nanostructured EMD were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and nitrogen adsorption-desorption techniques. The results obtained were compared with that of blank EMD (polymer free). The results indicated that the EMD having chitosan cross-linked with glutaraldehyde possesses a reduced particle size and more porous structure than the blank and EMDs synthesized in the presence of chitosan but without glutaraldehyde. The results revealed that chitosan was unable to play any significant role on its own but chitosan in the presence of glutaraldehyde forms a cross-linking structure, which in turn influences the nucleation and growth of the EMDs during electrodeposition. EMDs obtained in the presence of chitosan (1 g dm(-3)) and glutaraldehyde (1% glutaraldehyde) exhibited a reversible and better discharge capacity upon cycling than the blank which showed its typical capacity fading behaviour with cycling. In addition, EMD synthesized in the presence of 1 g dm(-3) chitosan and 2% glutaraldehyde exhibited a superior electrochemical performance than the blank and lower amounts (1%; 1.5%) of glutaraldehyde, showing a stable discharge capacity of 60 mA h g(-1) recorded up to 40 cycles in alkaline KOH electrolyte for a Zn-MnO2 system. Our results demonstrate the potential of using polymer modified EMDs as a new generation of alkaline battery materials. The XPS data show that

  5. Multiplex electrochemical DNA platform for femtomolar-level quantification of genetically modified soybean.

    PubMed

    Manzanares-Palenzuela, C Lorena; de-los-Santos-Álvarez, Noemí; Lobo-Castañón, María Jesús; López-Ruiz, Beatriz

    2015-06-15

    Current EU regulations on the mandatory labeling of genetically modified organisms (GMOs) with a minimum content of 0.9% would benefit from the availability of reliable and rapid methods to detect and quantify DNA sequences specific for GMOs. Different genosensors have been developed to this aim, mainly intended for GMO screening. A remaining challenge, however, is the development of genosensing platforms for GMO quantification, which should be expressed as the number of event-specific DNA sequences per taxon-specific sequences. Here we report a simple and sensitive multiplexed electrochemical approach for the quantification of Roundup-Ready Soybean (RRS). Two DNA sequences, taxon (lectin) and event-specific (RR), are targeted via hybridization onto magnetic beads. Both sequences are simultaneously detected by performing the immobilization, hybridization and labeling steps in a single tube and parallel electrochemical readout. Hybridization is performed in a sandwich format using signaling probes labeled with fluorescein isothiocyanate (FITC) or digoxigenin (Dig), followed by dual enzymatic labeling using Fab fragments of anti-Dig and anti-FITC conjugated to peroxidase or alkaline phosphatase, respectively. Electrochemical measurement of the enzyme activity is finally performed on screen-printed carbon electrodes. The assay gave a linear range of 2-250 pM for both targets, with LOD values of 650 fM (160 amol) and 190 fM (50 amol) for the event-specific and the taxon-specific targets, respectively. Results indicate that the method could be applied for GMO quantification below the European labeling threshold level (0.9%), offering a general approach for the rapid quantification of specific GMO events in foods.

  6. Impedance spectroscopy study of a catechol-modified activated carbon electrode as active material in electrochemical capacitor

    NASA Astrophysics Data System (ADS)

    Cougnon, C.; Lebègue, E.; Pognon, G.

    2015-01-01

    Modified activated carbon (Norit S-50) electrodes with electrochemical double layer (EDL) capacitance and redox capacitance contributions to the electric charge storage were tested in 1 M H2SO4 to quantify the benefit and the limitation of the surface redox reactions on the electrochemical performances of the resulting pseudo-capacitive materials. The electrochemical performances of an electrochemically anodized carbon electrode and a catechol-modified carbon electrode, which make use both EDL capacitance of the porous structure of the carbon and redox capacitance, were compared to the performances obtained for the pristine carbon. Nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the BET surface area, pore size distribution, pore volume and average pore diameter. The electrochemical behavior of carbon materials was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The EIS data were discussed by using a complex capacitance model that allows defining the characteristic time constant, the global capacitance and the frequency at which the maximum charge stored is reached. The EIS measurements were achieved at different dc potential values where a redox activity occurs and the evolution of the capacitance and the capacitive relaxation time with the electrode potential are presented. Realistic galvanostatic charge/discharge measurements performed at different current rates corroborate the results obtained by impedance.

  7. Carboxybetaine Modified Interface for Electrochemical Glycoprofiling of Antibodies Isolated from Human Serum

    PubMed Central

    2015-01-01

    Impedimetric lectin biosensors capable of recognizing two different carbohydrates (galactose and sialic acid) in glycans attached to antibodies isolated from human serum were prepared. The first step entailed the modification of a gold surface by a self-assembled monolayer (SAM) deposited from a solution containing a carboxybetaine-terminated thiol applied to the subsequent covalent immobilization of lectins and to resist nonspecific protein adsorption. In the next step, Sambucus nigra agglutinin (SNA) or Ricinus communis agglutinin (RCA) was covalently attached to the SAM, and the whole process of building a bioreceptive layer was optimized and characterized using a diverse range of techniques including electrochemical impedance spectroscopy, cyclic voltammetry, quartz crystal microbalance, contact angle measurements, zeta-potential assays, X-ray photoelectron spectroscopy, and atomic force microscopy. In addition, the application of the SNA-based lectin biosensor in the glycoprofiling of antibodies isolated from the human sera of healthy individuals and of patients suffering from rheumatoid arthritis (RA) was successfully validated using an SNA-based lectin microarray. The results showed that the SNA lectin, in particular, is capable of discriminating between the antibodies isolated from healthy individuals and those from RA patients based on changes in the amount of sialic acid present in the antibodies. In addition, the results obtained by the application of RCA and SNA biosensors indicate that the abundance of galactose and sialic acid in antibodies isolated from healthy individuals is age-related. PMID:26048139

  8. Electrochemical detection of phenolic estrogenic compounds at clay modified carbon paste electrode

    NASA Astrophysics Data System (ADS)

    Belkamssa, N.; Ouattara, L.; Kawachi, A.; Tsujimura, M.; Isoda, H.; Chtaini, A.; Ksibi, M.

    2015-04-01

    A simple and sensitive electroanalytical method was developed to determine the Endocrine Disrupting chemical 4-tert-octylphenol on clay modified carbon paste electrode (Clay/CPE). The electrochemical response of the proposed electrode was studied by means of cyclic and square wave voltammetry. It has found that the oxidation of 4-tert-octylphenol on the clay/CPE displayed a well-defined oxidation peak. Under these optimal conditions, a linear relation between concentrations of 4-tert-octylphenol current response was obtained over range of 7.26×10-6 to 3.87×10-7 with a detection and quantification limit of 9.2×10-7 M and 3.06×10-6 M, respectively. The correlation coefficient is 0.9963. The modified electrode showed suitable sensitivity, high stability and an accurate detection of 4-tert-octylphenol. The modified electrode also relevant suitable selectivity for various phenolic estrogenic compounds.

  9. Performance and stability of electrochemical capacitor based on anthraquinone modified activated carbon

    NASA Astrophysics Data System (ADS)

    Pognon, Grégory; Brousse, Thierry; Demarconnay, Laurent; Bélanger, Daniel

    A series of high surface area activated carbon powders modified with various loadings of electroactive anthraquinone groups was obtained by the spontaneous reduction of the corresponding in situ generated diazonium derivative on activated carbon. The diazotation and grafting reactions are fast and efficient and by varying the stoichiometry of these reactions the grafting amount can be controlled. With appropriate reaction conditions, the attachment of anthraquinone groups allows to double the capacitance of the modified carbonaceous material (195 F g -1) compared to the unmodified carbon (100 F g -1) due to the contribution of the redox reaction of grafted anthraquinone molecules. Long time galvanostatic charge-discharge cycling experiments were performed for composite electrodes prepared using modified carbons having two different AQ loadings (e.g. 6.7 and 11.1 wt.%). Following 10 000 charge/discharge cycles, only a 17% loss of the faradaic capacitance was observed for these two carbons. Thus, this hybrid bifunctional material appears to be an excellent candidate for application as active electrode in electrochemical capacitors.

  10. Electrochemical Sensing of Bisphenol A by a Didodecyldimethylammonium Bromide-Modified Expanded Graphite Paste Electrode.

    PubMed

    Zhang, Jing; Ma, Sa; Wang, Wenchang; Chen, Zhidong

    2016-07-01

    An electrochemical and sensitive sensing of 2,2-bis(4-hydroxyphenyl) propane [bisphenol A (BPA)] was developed based on a didodecyldimethylammonium bromide-modified expanded graphite paste electrode (DDAB-EGPE). The DDAB-EGPE was prepared by suspending an EGPE in a DDAB aqueous solution, and allowing the DDAB to form a hydrophobic film on the expanded graphite surface. Compared with the EGPE, the DDAB-EGPE showed improved electrochemical response of BPA because of the preconcentration of BPA in DDAB via hydrophobic interaction. Due to the electrocatalytic activity of BPA, a sensor for BPA was constructed based on the DDAB-EGPE. The DDAB-EGPE exhibited a wide linear response to BPA ranging from 6.0 × 10(-8) to 2.0 × 10(-5) mol/L with a detection limit of 7.1 nmol/L at S/N = 3. The designed sensor showed good reproducibility and stability. The proposed sensor was successfully applied to the determination of BPA in three types of real plastic product samples. This sensor presented a simple, rapid, and sensitive platform for the determination of BPA and could become a versatile and powerful tool for food safety. PMID:27213485

  11. High sensitivity and label-free detection of Enterovirus 71 by nanogold modified electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Fang-Yu; Li, Hsing-Yuan; Tseng, Shing-Hua; Cheng, Tsai-Mu; Chu, Hsueh-Liang; Yang, Jyh-Yuan; Chang, Chia-Ching

    2013-03-01

    Enterovirus 71 (EV71), which is the most fulminant and invasive species of enterovirus, can cause children neurologic complications and death within 2-3 days after fever and rash developed. Besides, EV71 has high sequence similarity with Coxsackie A 16 (CA16) that makes differential diagnosis difficult in clinic and laboratory. Since conventional viral diagnostic method cannot diagnose EV71 quickly and EV71 can transmit at low viral titer, the patients might delay in treatment. A quick, high sensitive, and high specific test for EV71 detection is pivotal. Electrochemical impedance spectroscopy (EIS) has been applied for detecting bio-molecules as biosensors recently. In this study, we try to build a detection platform for EV71 detection by nanogold modified EIS probe. The result shows that our probe can detect 3.6 VP1/50 μl (one EV71 particle has 60 VP1) in 3 minutes. The test can also distinguish EV71 from CA16 and lysozyme. Diagnosis of enterovirus 71 by electrochemical impedance spectroscopy has the potential to apply in clinic.

  12. Microstructure and electrochemical behavior of cerium conversion coating modified with silane agent on magnesium substrates

    NASA Astrophysics Data System (ADS)

    Lei, Li; Shi, Jing; Wang, Xin; Liu, Dan; Xu, Haigang

    2016-07-01

    The cerium conversion coating with and without different concentrations of silane agent bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) modification is obtained on magnesium alloys. Detailed properties of the coatings and the role of BTESPT as an additive are studied and followed with careful discussion. The coating morphology, wettability, chemical composition and corrosion resistance are characterized by scanning electronic microscope (SEM), water contact-angle, X-ray photoelectron spectroscopy (XPS), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of the coatings is investigated using EIS. The results indicate that the coating morphology and composition can be controlled by changing silane concentration. The combination of cerium ions and silane molecules could promote the formation of more homogenous and higher hydrophobic coating. The coating turns to be more compact and the adhesive strength between the coating and the magnesium substrate are strongly improved with the formation of Sisbnd Osbnd Si and Sisbnd Osbnd M chemical bonds. The optimum corrosion resistance of the coating in the corrosive media is obtained by 25 ml L-1 BTESPT modification. This whole study implies that the cerium conversion coating modified with certain silane agent deserves cautiousness before its application for corrosion resistance.

  13. Electrochemical behaviour and surface conductivity of niobium carbide-modified austenitic stainless steel bipolar plate

    NASA Astrophysics Data System (ADS)

    Wang, Lixia; Sun, Juncai; Kang, Bin; Li, Song; Ji, Shijun; Wen, Zhongsheng; Wang, Xiaochun

    2014-01-01

    A niobium carbide diffusion layer with a cubic NbC phase surface layer (∼6 μm) and a Nb and C diffusion subsurface layer (∼1 μm) is fabricated on the surface of AISI 304 stainless steel (304 SS) bipolar plate in a proton exchange membrane fuel cell (PEMFC) using plasma surface diffusion alloying. The electrochemical behaviour of the niobium carbide diffusion-modified 304 SS (Nb-C 304 SS) is investigated in simulated PEMFC environments (0.5 M H2SO4 and 2 ppm HF solution at 80 °C). Potentiodynamic, potentiostatic polarisation and electrochemical impedance spectroscopy measurements reveal that the niobium carbide diffusion layer considerably improves the corrosion resistance of 304 SS compared with untreated samples. The corrosion current density of Nb-C 304 SS is maintained at 0.058 μA cm-2 and 0.051 μA cm-2 under simulated anodic and cathodic conditions, respectively. The interfacial contact resistance of Nb-C 304 SS is 8.47 mΩ cm2 at a compaction force of 140 N cm-2, which is significantly lower than that of the untreated sample (100.98 mΩ cm2). Moreover, only a minor increase in the ICR of Nb-C 304 SS occurs after 10 h potentiostatic tests in both cathodic and anodic environments.

  14. Graphene electrode modified with electrochemically reduced graphene oxide for label-free DNA detection.

    PubMed

    Li, Bing; Pan, Genhua; Avent, Neil D; Lowry, Roy B; Madgett, Tracey E; Waines, Paul L

    2015-10-15

    A novel printed graphene electrode modified with electrochemically reduced graphene oxide was developed for the detection of a specific oligonucleotide sequence. The graphene oxide was immobilized onto the surface of a graphene electrode via π-π bonds and electrochemical reduction of graphene oxide was achieved by cyclic voltammetry. A much higher redox current was observed from the reduced graphene oxide-graphene double-layer electrode, a 42% and 36.7% increase, respectively, in comparison with that of a bare printed graphene or reduced graphene oxide electrode. The good electron transfer activity is attributed to a combination of the large number of electroactive sites in reduced graphene oxide and the high conductivity nature of graphene. The probe ssDNA was further immobilized onto the surface of the reduced graphene oxide-graphene double-layer electrode via π-π bonds and then hybridized with its target cDNA. The change of peak current due to the hybridized dsDNA could be used for quantitative sensing of DNA concentration. It has been demonstrated that a linear range from 10(-7)M to 10(-12)M is achievable for the detection of human immunodeficiency virus 1 gene with a detection limit of 1.58 × 10(-13)M as determined by three times standard deviation of zero DNA concentration.

  15. Preparative separation of enantiomers based on functional nucleic acids modified gold nanoparticles.

    PubMed

    Huang, Rong; Wang, Daifang; Liu, Shuzhen; Guo, Longhua; Wang, Fangfang; Lin, Zhenyu; Qiu, Bin; Chen, Guonan

    2013-11-01

    The preparative-scale separation of chiral compounds is vitally important for the pharmaceutical industry and related fields. Herein we report a simple approach for rapid preparative separation of enantiomers using functional nucleic acids modified gold nanoparticles (AuNPs). The separation of DL-tryptophan (DL-Trp) is demonstrated as an example to show the feasibility of the approach. AuNPs modified with enantioselective aptamers were added into a racemic mixture of DL -Trp. The aptamer-specific enantiomer (L-Trp) binds to the AuNPs surface through aptamer-L-Trp interaction. The separation of DL-Trp is then simply accomplished by centrifugation: the precipitate containing L-Trp bounded AuNPs is separated from the solution, while the D-Trp remains in the supernatant. The precipitate is then redispersed in water. The aptamer is denatured under 95 °C and a second centrifugation is then performed, resulting in the separation of AuNPs and L-Trp. The supernatant is finally collected to obtain pure L-Trp in water. The results show that the racemic mixture of DL-Trp is completely separated into D-Trp and L-Trp, respectively, after 5 rounds of repeated addition of fresh aptamer-modified AuNPs to the DL-Trp mixture solution. Additionally, the aptamer-modified AuNPs can be repeatedly used for at least eight times without significant loss of its binding ability because the aptamer can be easily denatured and renatured in relatively mild conditions. The proposed approach could be scaled up and extended to the separation of other enantiomers by the adoption of other enantioselective aptamers.

  16. Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid: An Undergraduate Analytical Chemistry Laboratory Experiment

    ERIC Educational Resources Information Center

    Ito, Takashi; Perera, D. M. Neluni T.; Nagasaka, Shinobu

    2008-01-01

    This article describes an undergraduate electrochemistry laboratory experiment in which the students measure the L-ascorbic acid content of a real sample. Gold electrodes modified with self-assembled monolayers (SAMs) of thioctic acid and cysteamine are prepared to study the effects of surface modification on the electrode reaction of L-ascorbic…

  17. Simple electrochemical sensor for caffeine based on carbon and Nafion-modified carbon electrodes.

    PubMed

    Torres, A Carolina; Barsan, Madalina M; Brett, Christopher M A

    2014-04-15

    A simple, economic, highly sensitive and highly selective method for the detection of caffeine has been developed at bare and Nafion-modified glassy carbon electrodes (GCE). The electrochemical behaviour of caffeine was examined in electrolyte solutions of phosphate buffer saline, sodium perchlorate, and in choline chloride plus oxalic acid, using analytical determinations by fixed potential amperometry, phosphate buffer saline being the best. Modifications of the GCE surface with poly(3,4-ethylenedioxythiophene) (PEDOT), Nafion, and multi-walled carbon nanotubes were tested in order to evaluate possible sensor performance enhancements, Nafion giving the most satisfactory results. The effect of interfering compounds usually found in samples containing caffeine was examined at GCE without and with Nafion coating, to exclude interferences, and the sensors were successfully applied to determine the caffeine content in commercial beverages and drugs.

  18. Simple electrochemical sensor for caffeine based on carbon and Nafion-modified carbon electrodes.

    PubMed

    Torres, A Carolina; Barsan, Madalina M; Brett, Christopher M A

    2014-04-15

    A simple, economic, highly sensitive and highly selective method for the detection of caffeine has been developed at bare and Nafion-modified glassy carbon electrodes (GCE). The electrochemical behaviour of caffeine was examined in electrolyte solutions of phosphate buffer saline, sodium perchlorate, and in choline chloride plus oxalic acid, using analytical determinations by fixed potential amperometry, phosphate buffer saline being the best. Modifications of the GCE surface with poly(3,4-ethylenedioxythiophene) (PEDOT), Nafion, and multi-walled carbon nanotubes were tested in order to evaluate possible sensor performance enhancements, Nafion giving the most satisfactory results. The effect of interfering compounds usually found in samples containing caffeine was examined at GCE without and with Nafion coating, to exclude interferences, and the sensors were successfully applied to determine the caffeine content in commercial beverages and drugs. PMID:24295698

  19. Highly sensitive electrochemical determination of Sunset Yellow based on gold nanoparticles/graphene electrode.

    PubMed

    Wang, Jin; Yang, Beibei; Wang, Huiwen; Yang, Ping; Du, Yukou

    2015-09-17

    An electrochemical sensor was prepared using Au nanoparticles and reduced graphene successfully decorated on the glassy carbon electrode (Au/RGO/GCE) through an electrochemical method which was applied to detect Sunset Yellow (SY). The as-prepared electrode was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and electrochemical measurements. The results of cyclic voltammetry (CV) proved that Au/RGO/GCE had the highest catalytic activity for the oxidation of SY as compared with GCE, Au/GCE, and RGO/GCE. Differential pulse voltammetry (DPV) showed that the linear calibration curves for SY on Au/RGO/GCE in the range of 0.002 μM-109.14 μM, and the detection limit was estimated to be 2 nM (S/N = 3). These results suggested that the obtained Au/RGO/GCE was applied to detect SY with high sensitivity, low detection limit and good stability, which provided a promising future for the development of portable sensor in food additives.

  20. Electrochemical machining of gold microstructures in LiCl/dimethyl sulfoxide.

    PubMed

    Ma, Xinzhou; Bán, Andreas; Schuster, Rolf

    2010-02-22

    LiCl/dimethyl sulfoxide (DMSO) electrolytes were applied for the electrochemical micromachining of Au. Upon the application of short potential pulses in the nanosecond range to a small carbon-fiber electrode, three-dimensional microstructures with high aspect ratios were fabricated. We achieved machining resolutions down to about 100 nm. In order to find appropriate machining parameters, that is, tool and workpiece rest potentials, the electrochemical behavior of Au in LiCl/DMSO solutions with and without addition of water was studied by cyclic voltammetry. In waterless electrolyte Au dissolves predominantly as Au(I), whereas upon the addition of water the formation of Au(III) becomes increasingly important. Because of the low conductivity of LiCl/DMSO compared with aqueous electrolytes, high machining precision is obtained with moderately short pulses. Furthermore, the redeposition of dissolved Au can be effectively avoided, since Au dissolution in LiCl/DMSO is highly irreversible. Both observations render LiCl/DMSO an appropriate electrolyte for the routine electrochemical micromachining of Au. PMID:20017182

  1. Enzymatically catalytic signal tracing by a glucose oxidase and ferrocene dually functionalized nanoporous gold nanoprobe for ultrasensitive electrochemical measurement of a tumor biomarker.

    PubMed

    Cheng, Hui; Xu, Lingling; Zhang, Haili; Yu, Aimin; Lai, Guosong

    2016-07-21

    A nanoporous gold nanosphere (pAu NS) was synthesized to load high-content glucose oxidase (GOx) and ferrocene (Fc) for the successful preparation of a new gold nanoprobe. After the specific recognition of the tumor biomarker of carcinoembryonic antigen (CEA) at a gold electrode based aptasensor, this GOx and Fc dually functionalized pAu NS nanoprobe was further used for sandwich immunoreaction and signal tracing. Based on the Fc-mediated GOx-catalytic reaction, the gold nanoprobes quantitatively captured onto the electrode surface produced a sensitive electrochemical signal corresponding to the protein recognition events, which led to the development of a new biosensing method for CEA measurement. Both the high loading of GOx and Fc on the pAu NS nanocarrier and the enzymatically catalytic reaction of the nanoprobe greatly amplify the electrochemical signal; meanwhile, the immobilization of the Fc mediator on this enzyme nanoprobe and the highly specific aptamer recognition drastically decrease the background current, resulting in the achievement of ultrahigh sensitivity of the method. Under optimum conditions, this method shows an excellent analytical performance including a wide linear relationship of five-order of magnitude and a low detection limit down to 0.45 pg mL(-1). Thus this pAu NS based gold nanoprobe and the proposed immunoassay method provide great potential for practical applications. PMID:27186605

  2. An investigation of the electrochemical action of the epoxy zinc-rich coatings containing surface modified aluminum nanoparticle

    NASA Astrophysics Data System (ADS)

    Jalili, M.; Rostami, M.; Ramezanzadeh, B.

    2015-02-01

    Aluminum nanoparticle was modified with amino trimethylene phosphonic acid (ATMP). The surface characterization of the nanoparticles was done by X-ray photo electron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis. The influence of the replacement of 2 wt% of zinc dust in the standard zinc-rich epoxy coating by nanoparticles on the electrochemical action of the coating was studied by electrochemical impedance spectroscopy (EIS) and salt spray tests. The morphology and phase composition of the zinc rich paints were evaluated by X-ray diffraction (XRD) and filed-emission scanning electron microscopy (FE-SEM). Results showed that the ATMP molecules successfully adsorbed on the surface of Al nanoparticles. Results obtained from salt spray and electrochemical measurements revealed that the addition of surface modified nanoparticles to the zinc rich coating enhanced its galvanic action and corrosion protection properties.

  3. Glassy carbon electrodes sequentially modified by cysteamine-capped gold nanoparticles and poly(amidoamine) dendrimers generation 4.5 for detecting uric acid in human serum without ascorbic acid interference.

    PubMed

    Ramírez-Segovia, A S; Banda-Alemán, J A; Gutiérrez-Granados, S; Rodríguez, A; Rodríguez, F J; Godínez, Luis A; Bustos, E; Manríquez, J

    2014-02-17

    Glassy carbon electrodes (GCE) were sequentially modified by cysteamine-capped gold nanoparticles (AuNp@cysteamine) and PAMAM dendrimers generation 4.5 bearing 128-COOH peripheral groups (GCE/AuNp@cysteamine/PAMAM), in order to explore their capabilities as electrochemical detectors of uric acid (UA) in human serum samples at pH 2. The results showed that concentrations of UA detected by cyclic voltammetry with GCE/AuNp@cysteamine/PAMAM were comparable (deviation <±10%; limits of detection (LOD) and quantification (LOQ) were 1.7×10(-4) and 5.8×10(-4) mg dL(-1), respectively) to those concentrations obtained using the uricase-based enzymatic-colorimetric method. It was also observed that the presence of dendrimers in the GCE/AuNp@cysteamine/PAMAM system minimizes ascorbic acid (AA) interference during UA oxidation, thus improving the electrocatalytic activity of the gold nanoparticles. PMID:24491759

  4. Porous platinum nanotubes modified with dendrimers as nanocarriers and electrocatalysts for sensitive electrochemical aptasensors based on enzymatic signal amplification.

    PubMed

    Xu, Wenju; Wu, Yongmei; Yi, Huayu; Bai, Lijuan; Chai, Yaqin; Yuan, Ruo

    2014-02-11

    A highly sensitive electrochemical aptasensor for thrombin detection is developed and demonstrated by using porous platinum nanotubes modified with polyamidoamine dendrimers as nanocarriers and electrocatalysts. The proposed strategy affords a low detection limit of 0.03 pM based on enzyme-based signal amplification.

  5. Controlled Integration of Gold Nanoparticles and Organic Fluorophores Using Synthetically Modified MS2 Viral Capsids

    PubMed Central

    Capehart, Stacy L.; Coyle, Michael P.; Glasgow, Jeff E.

    2013-01-01

    The placement of fluorophores in close proximity to metal nanoparticle surfaces is proposed to enhance several photo-physical properties of the dyes, potentially leading to improved quantum yields and decreased photobleaching. It is difficult in practice, however, to establish and maintain the nanoscale distances that are required to maximize these effects. The type of metal, size, and shape of the nanoparticle, the physical distance separating the metal nanoparticle from the organic dye, and the spectral properties of the fluorophore itself are all proposed to influence the quantum yield and lifetime. This results in a complex behavior that can lead to either enhanced or quenched fluorescence in different contexts. In this report, we describe a well-defined system that can be used to explore these effects, while physically preventing the fluorophores from contacting the nanoparticle surfaces. The basis of this system is the spherical protein capsid of bacteriophage MS2, which was used to house gold particles within its interior volume. The exterior surface of each capsid was then modified with Alexa Fluor 488 (AF 488) labeled DNA strands. By placing AF 488 dyes at distances of 3 bp, 12 bp, and 24 bp from the surface of capsids containing 10 nm gold nanoparticles, fluorescence intensity enhancements of 2.2, 1.2, and 1.0 were observed, respectively. A corresponding decrease in fluorescence lifetime was observed for each distance. Due to its well-defined and modular nature, this architecture allows the rapid exploration of the many variables involved in metal-controlled fluorescence, leading to a better understanding of this phenomenon. PMID:23402352

  6. Examining the effects of self-assembled monolayers on nanoporous gold based amperometric glucose biosensors.

    PubMed

    Xiao, Xinxin; Li, Hui; Wang, Meng'en; Zhang, Kai; Si, Pengchao

    2014-01-21

    Nanoporous gold (NPG) based biosensors have been constructed by covalently immobilizing glucose oxidase (GOx) onto self-assembled monolayers (SAMs). With p-benzoquinone (BQ) as a mediator, diffusion behavior and amperometric biosensor performance are evaluated by electrochemical characterization. The enzyme modified electrodes are demonstrated to show a thickness-sensitive behavior. Compared with planar polycrystalline gold, the unique porous structure of NPG has also been characterized via an electrochemical surface reconstruction process. Single-crystal gold-like electrochemical behavior on NPG and a comprehensive understanding of its impacts on sensor performance have been proposed. PMID:24256634

  7. Hydrodechlorination catalytic activity of gold nanoparticles supported on TiO 2 modified SBA-15 investigated by IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Hannus, I.; Búza, M.; Beck, A.; Guczi, L.; Sáfrán, G.

    2009-04-01

    The hydrodechlorination catalytic activity of gold nanoparticles on SBA-15 silica modified by TiO 2 promoters has been investigated. Comparing the hydrodechlorination catalytic activity platinum nanoparticles supported on TiO 2 catalyst was used in the hydrodechlorination of CCl 4 as model compound. The IR spectroscopic experimental results showed that the gold nanoparticles have higher catalytic activity, than platinum ones. The two samples were tested also in CO oxidation, in which Au/TiO 2/SBA-15 possess also somewhat higher activity than Pt/TiO 2.

  8. Highly Selective Electrochemical Determination of Taxol Based on ds-DNA-Modified Pencil Electrode.

    PubMed

    Taei, M; Hassanpour, F; Salavati, H; Sadeghi, Z; Alvandi, H

    2015-05-01

    In this research, TiO2/ZrO2 nanocomposite has been prepared using sol-gel method. The TiO2/ZrO2 composite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). A sensitive electrochemical biosensor is also presented for the determination of Taxol based on ds-DNA decorated multiwall carbon nanotubes-TiO2/ZrO2-chitosan-modified pencil electrode (ds-DNA-MWNTs-TiO2/ZrO2-CHIT-PGE). The UV spectroscopic data and differential pulse voltammetry revealed that there is a strong interaction between ds-DNA and Taxol. The groove binding of Taxol to ds-DNA helix has been characterized by a red shift (less than 8 nm) in wavelength and the decrease in the differential pulse voltammetry oxidation signal intensity of the Taxol at pencil graphite electrode (PGE) after its interaction with ds-DNA. Finally, a pretreated PGE modified with ds-DNA-MWNTs-TiO2/ZrO2-CHIT was tested in order to determine Taxol content in the solution. The dynamic range was from 0.7 to 1874.0 nmol L(-1) with a detection limit of 0.01 nmol L(-1). This sensing platform was successfully applied for the determination of Taxol in pharmaceutical and biological samples.

  9. An Electrochemical DNA Microbiosensor Based on Succinimide-Modified Acrylic Microspheres

    PubMed Central

    Ulianas, Alizar; Heng, Lee Yook; Hanifah, Sharina Abu; Ling, Tan Ling

    2012-01-01

    An electrochemical microbiosensor for DNA has been fabricated based on new acrylic microspheres modified with reactive N-acryloxysuccinimide (NAS) functional groups. Hydrophobic poly(n-butylacrylate-N-acryloxysuccinimide) microspheres were synthesized in an emulsion form with a simple one-step photopolymerization technique. Aminated DNA probe was attached to the succinimde functional group of the acrylic microspheres via covalent bonding. The hybridization of the immobilized DNA probe with the complementary DNA was studied by differential pulse voltametry using anthraquninone-2-sulfonic acid monohydrate sodium salt (AQMS) as the electroactive hybridization label. The influences of many factors such as duration of DNA probe immobilization and hybridization, pH, type of ions, buffer concentrations, ionic strength, operational temperature and non-complementary DNA on the biosensor performance were evaluated. Under optimized conditions, the DNA microbiosensor demonstrated a linear response range to target DNA over a wide concentration range of 1.0 × 10−16 and 1.0 × 10−8 M with a lower limit of detection (LOD) of 9.46 × 10−17 M (R2 = 0.97). This DNA microbiosensor showed good reproducibility with 2.84% RSD (relative standard deviation) (n = 3). Application of the NAS-modified acrylic microspheres in the construction of DNA microbiosensor had improved the overall analytical performance of the resultant DNA microbiosensor when compared with other reported DNA biosensors using other nano-materials for membranes and microspheres as DNA immobilization matrices. PMID:22778594

  10. Highly Selective Electrochemical Determination of Taxol Based on ds-DNA-Modified Pencil Electrode.

    PubMed

    Taei, M; Hassanpour, F; Salavati, H; Sadeghi, Z; Alvandi, H

    2015-05-01

    In this research, TiO2/ZrO2 nanocomposite has been prepared using sol-gel method. The TiO2/ZrO2 composite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). A sensitive electrochemical biosensor is also presented for the determination of Taxol based on ds-DNA decorated multiwall carbon nanotubes-TiO2/ZrO2-chitosan-modified pencil electrode (ds-DNA-MWNTs-TiO2/ZrO2-CHIT-PGE). The UV spectroscopic data and differential pulse voltammetry revealed that there is a strong interaction between ds-DNA and Taxol. The groove binding of Taxol to ds-DNA helix has been characterized by a red shift (less than 8 nm) in wavelength and the decrease in the differential pulse voltammetry oxidation signal intensity of the Taxol at pencil graphite electrode (PGE) after its interaction with ds-DNA. Finally, a pretreated PGE modified with ds-DNA-MWNTs-TiO2/ZrO2-CHIT was tested in order to determine Taxol content in the solution. The dynamic range was from 0.7 to 1874.0 nmol L(-1) with a detection limit of 0.01 nmol L(-1). This sensing platform was successfully applied for the determination of Taxol in pharmaceutical and biological samples. PMID:25825248

  11. Flower-like self-assembly of gold nanoparticles for highly sensitive electrochemical detection of chromium(VI).

    PubMed

    Ouyang, Ruizhuo; Bragg, Stefanie A; Chambers, James Q; Xue, Zi-Ling

    2012-04-13

    We report here the fabrication of a flower-like self-assembly of gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) as a highly sensitive platform for ultratrace Cr(VI) detection. Two AuNP layers are used in the current approach, in which the first is electroplated on the GCE surface as anchors for binding to an overcoated thiol sol-gel film derived from 3-mercaptopropyltrimethoxysilane (MPTS). The second AuNP layer is then self-assembled on the surface of the sol-gel film, forming flower-like gold nanoelectrodes enlarging the electrode surface. When functionalized by a thiol pyridinium, the fabricated electrode displays a well-defined peak for selective Cr(VI) reduction with an unusually large, linear concentration range of 10-1200 ng L(-1) and a low detection limit of 2.9 ng L(-1). In comparison to previous approaches using MPTS and AuNPs on Au electrodes, the current work expands the use of AuNPs to the GCE. Subsequent functionalization of the secondary AuNPs by a thiol pyridinium and adsorption/preconcentration of Cr(VI) lead to the unusually large detection range and high sensitivity. The stepwise preparation of the electrode has been characterized by electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM), and IR. The newly designed electrode exhibits good stability, and has been successfully employed to measure chromium in a pre-treated blood sample. The method demonstrates acceptable fabrication reproducibility and accuracy.

  12. Optimized design of a nanostructured SPCE-based multipurpose biosensing platform formed by ferrocene-tethered electrochemically-deposited cauliflower-shaped gold nanoparticles

    PubMed Central

    Argoubi, Wicem; Saadaoui, Maroua

    2015-01-01

    Summary The demand for on-site nanodevices is constantly increasing. The technology development for the design of such devices is highly regarded. In this work, we report the design of a disposable platform that is structured with cauliflower-shaped gold nanoparticles (cfAuNPs) and we show its applications in immunosensing and enzyme-based detection. The electrochemical reduction of Au(III) allows for the electrodeposition of highly dispersed cauliflower-shaped gold nanoparticles on the surface of screen-printed carbon electrodes (SPCEs). The nanostructures were functionalized using ferrocenylmethyl lipoic acid ester which allowed for the tethering of the ferrocene group to gold, which serves as an electrochemical transducer/mediator. The bioconjugation of the surface with anti-human IgG antibody (α-hIgG) or horseradish peroxidase (HRP) enzyme yields biosensors, which have been applied for the selective electrochemical detection of human IgG (hIgG) or H2O2 as model analytes, respectively. Parameters such as the number of sweeps, amount of charge generated from the oxidation of the electrodeposited gold, time of incubation and concentration of the ferrocene derivatives have been studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Selectivity and specificity tests have been also performed in the presence of potentially interfering substances to either hIgG or H2O2. Results showed that the devised immunosensor is endowed with good selectivity and specificity in the presence of several folds of competitive analytes. The enzyme-based platform showed a good catalytic activity towards H2O2 oxidation which predestined it to potential applications pertaining to enzymatic kinetics studies. The levels of hIgG in human serum and H2O2 in honey were successfully determined and served as assessment tools of the applicability of the platforms for real samples analysis. PMID:26425435

  13. Optimized design of a nanostructured SPCE-based multipurpose biosensing platform formed by ferrocene-tethered electrochemically-deposited cauliflower-shaped gold nanoparticles.

    PubMed

    Argoubi, Wicem; Saadaoui, Maroua; Ben Aoun, Sami; Raouafi, Noureddine

    2015-01-01

    The demand for on-site nanodevices is constantly increasing. The technology development for the design of such devices is highly regarded. In this work, we report the design of a disposable platform that is structured with cauliflower-shaped gold nanoparticles (cfAuNPs) and we show its applications in immunosensing and enzyme-based detection. The electrochemical reduction of Au(III) allows for the electrodeposition of highly dispersed cauliflower-shaped gold nanoparticles on the surface of screen-printed carbon electrodes (SPCEs). The nanostructures were functionalized using ferrocenylmethyl lipoic acid ester which allowed for the tethering of the ferrocene group to gold, which serves as an electrochemical transducer/mediator. The bioconjugation of the surface with anti-human IgG antibody (α-hIgG) or horseradish peroxidase (HRP) enzyme yields biosensors, which have been applied for the selective electrochemical detection of human IgG (hIgG) or H2O2 as model analytes, respectively. Parameters such as the number of sweeps, amount of charge generated from the oxidation of the electrodeposited gold, time of incubation and concentration of the ferrocene derivatives have been studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Selectivity and specificity tests have been also performed in the presence of potentially interfering substances to either hIgG or H2O2. Results showed that the devised immunosensor is endowed with good selectivity and specificity in the presence of several folds of competitive analytes. The enzyme-based platform showed a good catalytic activity towards H2O2 oxidation which predestined it to potential applications pertaining to enzymatic kinetics studies. The levels of hIgG in human serum and H2O2 in honey were successfully determined and served as assessment tools of the applicability of the platforms for real samples analysis.

  14. Transforming the fabrication and biofunctionalization of gold nanoelectrode arrays into versatile electrochemical glucose biosensors.

    PubMed

    Claussen, Jonathan C; Wickner, Monique M; Fisher, Timothy S; Porterfield, D Marshall

    2011-05-01

    High-density arrays of conducting nanoelectrodes (i.e., nanoelectrode arrays [NEAs]) have been developed on the surface of a single electrode for numerous electrochemical sensing paradigms. However, a scalable fabrication technique and robust biofunctionalization protocol are oftentimes lacking and thus many NEA designs have limited efficacy and overall commercial viability in biosensing applications. In this report, we develop a lithography-free nanofabrication protocol to create large arrays of Au nanoelectrodes on a silicon wafer via a porous anodic alumina template. To demonstrate their effectiveness as electrochemical glucose biosensors, alkanethiol self-assembled monolayers (SAMs) are used to covalently attach the enzyme glucose oxidase to the Au NEA surface for subsequent glucose sensing. The sensitivity and linear sensing range of the biosensor is controlled by introducing higher concentrations of long-chain SAMs (11-mercaptoundecanoic acid: MUA) with short-chain SAMs (3-mercaptopropionic acid: MPA) into the enzyme immobilization scheme. This facile NEA fabrication protocol (that is well-suited for integration into electronic devices) and biosensor performance controllability (via the mixed-length enzyme-conjugated SAMs) transforms the Au NEAs into versatile glucose biosensors. Thus these Au NEAs could potentially be used in important real-word applications such as in health-care and bioenergy where biosensors with very distinct sensing capabilities are needed.

  15. Electrochemical determination of bisphenol A at ordered mesoporous carbon modified nano-carbon ionic liquid paste electrode.

    PubMed

    Li, Yonghong; Zhai, Xiurong; Liu, Xinsheng; Wang, Ling; Liu, Herong; Wang, Haibo

    2016-02-01

    A simple bisphenol A (BPA) sensor was successfully fabricated based on ordered mesoporous carbon CMK-3 modified nano-carbon ionic liquid paste electrode (CMK-3/nano-CILPE). The nanostructure of CMK-3 and the surface morphologies of modified electrodes were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Electrochemical properties of the fabricated electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated sensor displayed excellent electroactivity towards bisphenol A using linear sweep voltammetry (LSV). Experimental conditions influencing the analytical performance of the modified electrode were optimized. Under optimal conditions, the oxidation peak current was proportional to BPA concentration in the range from 0.2 μM to 150 μM with a detection limit of 0.05 μM (S/N=3). This method was successfully used for determination of BPA leached from drinking bottle and plastic bag with good recoveries.

  16. Graphene-metallic nanocomposites as modifiers in electrochemical glucose biosensor transducers

    NASA Astrophysics Data System (ADS)

    Altuntas, Derya Bal; Tepeli, Yudum; Anik, Ulku

    2016-09-01

    Graphene sheets and three different graphene-metallic nanocomposites including graphene-copper (graphene-Cu), graphene-nickel (graphene-Ni) and graphene-platinum (graphene-Pt) were prepared and characterized in the first place. Then the electrochemical performances of these nanocomposites were tested in glucose biosensor transducers, which were formed by combining these metallic nanocomposites with glucose oxidase enzyme and glassy carbon paste electrode (GCPE). This is the first work that includes the usage of these graphene-Me nanocomposites as a part of glucose biosensor transducer. Fabricated amperometric biosensors linear ranges were obtained as follow: For the plain graphene, the linear range was found in the concentration range between 50 μM and 800 μM with the RSD (n = 3 for 50 μM glucose) value of 12.86% and LOD value of 7.2 μM. For graphene-Pt modified glucose biosensor, the linear range was between 10 μM and 600 μM with the RSD (n = 3 for 50 μM glucose) value of 3.45% and LOD value of 3.06 μM. In the case of graphene-Ni modified glucose biosensor, the values were 25 μM to 600 μM with the RSD (n = 3 for 50 μM glucose) value of 8.76% and LOD value of 24.71 μM and for graphene-Cu modified glucose biosensor linear range was 25 μM to 400 μM with the RSD (n = 3 for 50 μM glucose) value of 3.93% and LOD value of 2.87 μM.

  17. The electrochemical preparation of FAD/ZnO with hemoglobin film-modified electrodes and their electroanalytical properties.

    PubMed

    Lin, Kuo-Chiang; Chen, Shen-Ming

    2006-03-15

    Flavin adenine dinucleotide (FAD)-modified zinc oxide self-assembly films were prepared using repeated cyclic voltammetry. The electrochemical reaction of the hemoglobin with the FAD/ZnO self-assembly film-modified electrodes and their electrocatalytic properties were investigated. This paper describes the successful loading of the electrochemically active molecules of hemoglobin and FAD along with ZnO by electrochemical method. In addition to the cyclic voltammetry, an electrochemical quartz crystal microbalance was used to study the growth mechanism and the properties of the films. The FAD/zinc oxide films exhibited a single redox couple, which corresponded to the FAD redox couple. The electrocatalytic properties of the O2, H2O2, trichloroacetic acid and SO(3)2- were studied by the FAD/zinc oxide films in the absence or in the presence of hemoglobin. The electrocatalytic reduction current had been developed from the cathodic peak of the FAD/zinc oxide redox couple. The electrocatalytic process involved an interaction of hemoglobin and FAD/GC film-modified electrode to increase the electrocatalytic reduction current. The electrocatalytic reduction of O2 using the FAD/zinc oxide films was investigated by cyclic voltammetry and rotating ring-disk electrode methods.

  18. On the High Sensitivity of the Electronic States of 1 nm Gold Particles to Pretreatments and Modifiers.

    PubMed

    Martynyuk, Oxana; Kotolevich, Yulia; Vélez, Rodrigo; Cabrera Ortega, Jesus Efren; Tiznado, Hugo; Zepeda Partida, Trino; Mota-Morales, Josué D; Pestryakov, Alexey; Bogdanchikova, Nina

    2016-03-31

    In this paper, the effect of modifiers and pretreatments on the electronic states of 1 nm gold nanoparticles (AuNPs) supported on silica was systematically studied. AuNPs deposited on silica (particle size of 2-4 nm) modified with Ce, La and Fe oxides, were studied by FTIR of adsorbed CO after different redox treatments at 100, 300 and 500 °C. This study was conducted at room temperature to allow detecting the electronic states of gold, which is more likely involved in CO oxidation at the same temperature. AuNP size distribution was measured by HRTEM. It is shown that the electronic state of gold species (Aun(δ-), Au⁰, Aun(δ+), Au⁺) in 1 nm AuNPs is sensitive to the modifier as well as to the temperatures of redox pretreatments. Supports modified with the same additives but containing larger AuNPs (~3, 4, 5, and 7 nm) were also studied. They showed that Au⁰ remains stable irrespective of additives and redox pretreatments, indicating no significant effect of such treatments on the electronic properties of larger AuNPs. Samples with a predominant AuNP size of 2 nm are an intermediate case between these two groups of materials.

  19. On the High Sensitivity of the Electronic States of 1 nm Gold Particles to Pretreatments and Modifiers.

    PubMed

    Martynyuk, Oxana; Kotolevich, Yulia; Vélez, Rodrigo; Cabrera Ortega, Jesus Efren; Tiznado, Hugo; Zepeda Partida, Trino; Mota-Morales, Josué D; Pestryakov, Alexey; Bogdanchikova, Nina

    2016-01-01

    In this paper, the effect of modifiers and pretreatments on the electronic states of 1 nm gold nanoparticles (AuNPs) supported on silica was systematically studied. AuNPs deposited on silica (particle size of 2-4 nm) modified with Ce, La and Fe oxides, were studied by FTIR of adsorbed CO after different redox treatments at 100, 300 and 500 °C. This study was conducted at room temperature to allow detecting the electronic states of gold, which is more likely involved in CO oxidation at the same temperature. AuNP size distribution was measured by HRTEM. It is shown that the electronic state of gold species (Aun(δ-), Au⁰, Aun(δ+), Au⁺) in 1 nm AuNPs is sensitive to the modifier as well as to the temperatures of redox pretreatments. Supports modified with the same additives but containing larger AuNPs (~3, 4, 5, and 7 nm) were also studied. They showed that Au⁰ remains stable irrespective of additives and redox pretreatments, indicating no significant effect of such treatments on the electronic properties of larger AuNPs. Samples with a predominant AuNP size of 2 nm are an intermediate case between these two groups of materials. PMID:27043514

  20. Mediated electron transfer of cellobiose dehydrogenase and glucose oxidase at osmium polymer-modified nanoporous gold electrodes.

    PubMed

    Salaj-Kosla, Urszula; Scanlon, Micheál D; Baumeister, Tobias; Zahma, Kawah; Ludwig, Roland; Ó Conghaile, Peter; MacAodha, Domhnall; Leech, Dónal; Magner, Edmond

    2013-04-01

    Nanoporous and planar gold electrodes were utilised as supports for the redox enzymes Aspergillus niger glucose oxidase (GOx) and Corynascus thermophilus cellobiose dehydrogenase (CtCDH). Electrodes modified with hydrogels containing enzyme, Os-redox polymers and the cross-linking agent poly(ethylene glycol)diglycidyl ether were used as biosensors for the determination of glucose and lactose. Limits of detection of 6.0 (±0.4), 16.0 (±0.1) and 2.0 (±0.1) μM were obtained for CtCDH-modified lactose and glucose biosensors and GOx-modified glucose biosensors, respectively, at nanoporous gold electrodes. Biofuel cells composed of GOx- and CtCDH-modified gold electrodes were utilised as anodes, together with Myrothecium verrucaria bilirubin oxidase (MvBOD) or Melanocarpus albomyces laccase as cathodes, in biofuel cells. A maximum power density of 41 μW/cm(2) was obtained for a CtCDH/MvBOD biofuel cell in 5 mM lactose and O2-saturated buffer (pH 7.4, 0.1 M phosphate, 150 mM NaCl).

  1. Mediated electron transfer of cellobiose dehydrogenase and glucose oxidase at osmium polymer-modified nanoporous gold electrodes.

    PubMed

    Salaj-Kosla, Urszula; Scanlon, Micheál D; Baumeister, Tobias; Zahma, Kawah; Ludwig, Roland; Ó Conghaile, Peter; MacAodha, Domhnall; Leech, Dónal; Magner, Edmond

    2013-04-01

    Nanoporous and planar gold electrodes were utilised as supports for the redox enzymes Aspergillus niger glucose oxidase (GOx) and Corynascus thermophilus cellobiose dehydrogenase (CtCDH). Electrodes modified with hydrogels containing enzyme, Os-redox polymers and the cross-linking agent poly(ethylene glycol)diglycidyl ether were used as biosensors for the determination of glucose and lactose. Limits of detection of 6.0 (±0.4), 16.0 (±0.1) and 2.0 (±0.1) μM were obtained for CtCDH-modified lactose and glucose biosensors and GOx-modified glucose biosensors, respectively, at nanoporous gold electrodes. Biofuel cells composed of GOx- and CtCDH-modified gold electrodes were utilised as anodes, together with Myrothecium verrucaria bilirubin oxidase (MvBOD) or Melanocarpus albomyces laccase as cathodes, in biofuel cells. A maximum power density of 41 μW/cm(2) was obtained for a CtCDH/MvBOD biofuel cell in 5 mM lactose and O2-saturated buffer (pH 7.4, 0.1 M phosphate, 150 mM NaCl). PMID:23274559

  2. Gold-platinum alloy nanowires as highly sensitive materials for electrochemical detection of hydrogen peroxide.

    PubMed

    Zhou, Yibo; Yu, Gang; Chang, Fangfang; Hu, Bonian; Zhong, Chuan-Jian

    2012-12-13

    The exploitation of the unique electrical properties of nanowires requires an effective assembly of nanowires as functional materials on a signal transduction platform. This paper describes a new strategy to assemble gold-platinum alloy nanowires on microelectrode devices and demonstrates the sensing characteristics to hydrogen peroxide. The alloy nanowires have been controllably electrodeposited on microelectrodes by applying an alternating current. The composition, morphology and alloying structures of the nanowires were characterized, revealing a single-phase alloy characteristic, highly monodispersed morphology, and controllable bimetallic compositions. The alloy nanowires were shown to exhibit electrocatalytic response characteristics for the detection of hydrogen peroxide, exhibiting a high sensitivity, low detection limit, and fast response time. The nanowire's response mechanism to hydrogen peroxide is also discussed in terms of the synergistic activity of the bimetallic binding sites, which has important implications for a better design of functional nanowires as sensing materials for a wide range of applications.

  3. SYNTHESIS OF GOLD-MODIFIED POLYOXYDIANILINE MEMBRANES: AN ELECTROCHEMICAL STUDY. (R830906)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  4. Electrochemical and Numerical Studies of Surface, Grain-Boundary and Bulk Copper Diffusion Into Gold

    NASA Astrophysics Data System (ADS)

    Miller, Eric Todd

    Surface, grain-boundary, and bulk chemical diffusivities of copper into gold were measured by chronoamperometry -potentiometry applied to Cu|CuCl |Au solid state galvanic cells at 300-400^circC. The cells were constructed using a novel vapor deposition technique which is described. The automated data acquisition techniques utilizing unique hardware and custom designed software are also presented. Chronoamperometry and a two electrode limited potential cyclic voltammetry technique were comparatively used to determine cell capacitance and resistance. Both gave similar RC values at lower temperatures but diverged from each other at higher temperatures. Electron hole conductivity of CuCl could not be determined from intercept values in the chronoamperometry Cottrell analysis. The partial molar enthalpy and entropy of mixing copper into gold were determined from Emf vs temperature vs composition measurements of Cu|CuCl |Au-Cu alloy cells. The results support the regular solution model of mixing with interaction energy parameter {bf{cal Q}} = 10kJ. Diffusion coefficients were calculated from the chronoamperometry-potentiometry time/flux/concentration data in two ways: via the Cottrell equation, for an average diffusion coefficient; and via a simplex and finite difference program for the simultaneous determination of surface, grain-boundary, and bulk diffusion coefficients. This program was run on a MASPAR MP-2 massively parallel computer. The surface and grain-boundary diffusivities were numerically determinable in single and polycrystalline cathodes at short diffusion times. Bulk diffusivity was determinable at short and long diffusion times and agreed with previous data. Surface diffusivity was two orders of magnitude larger than the bulk with lower activation energy. Grain -boundary diffusivity was one order of magnitude larger than the bulk with similar activation energy. The Cottrell equation was only valid at very long diffusion times due to the transient interface

  5. Selective capture of glycoproteins using lectin-modified nanoporous gold monolith.

    PubMed

    Alla, Allan J; D' Andrea, Felipe B; Bhattarai, Jay K; Cooper, Jared A; Tan, Yih Horng; Demchenko, Alexei V; Stine, Keith J

    2015-12-01

    The surface of nanoporous gold (np-Au) monoliths was modified via a flow method with the lectin Concanavalin A (Con A) to develop a substrate for separation and extraction of glycoproteins. Self-assembled monolayers (SAMs) of α-lipoic acid (LA) on the np-Au monoliths were prepared followed by activation of the terminal carboxyl groups to create amine reactive esters that were utilized in the immobilization of Con A. Thermogravimetric analysis (TGA) was used to determine the surface coverages of LA and Con A on np-Au monoliths which were found to be 1.31×10(18) and 1.85×10(15)moleculesm(-2), respectively. An in situ solution depletion method was developed that enabled surface coverage characterization without damaging the substrate and suggesting the possibility of regeneration. Using this method, the surface coverages of LA and Con A were found to be 0.989×10(18) and 1.32×10(15)moleculesm(-2), respectively. The selectivity of the Con A-modified np-Au monolith for the high mannose-containing glycoprotein ovalbumin (OVA) versus negative control non-glycosylated bovine serum albumin (BSA) was demonstrated by the difference in the ratio of the captured molecules to the immobilized Con A molecules, with OVA:Con A=2.3 and BSA:Con A=0.33. Extraction of OVA from a 1:3 mole ratio mixture with BSA was demonstrated by the greater amount of depletion of OVA concentration during the circulation with the developed substrate. A significant amount of captured OVA was eluted using α-methyl mannopyranoside as a competitive ligand. This work is motivated by the need to develop new materials for chromatographic separation and extraction substrates for use in preparative and analytical procedures in glycomics.

  6. Formation of alloys upon the simultaneous electrochemical deposition of gold and tin from ethylene glycol and aqueous electrolytes

    NASA Astrophysics Data System (ADS)

    Vorobyova, T. N.; Maltanova, H. M.; Vrublevskaya, O. N.

    2016-05-01

    An ethylene glycol (EG) solution containing Au(III) and Sn(IV) compounds, and conditions for the electrochemical deposition of Au-Sn alloy based on AuSn and Au5Sn intermetallics with total tin content of 30-55 at % are proposed. Fundamental difficulties of the deposition of alloys with high tin content, (including eutectic Au-Sn alloy) from aqueous electrolytes are revealed. It is determined via voltammetry that the simultaneous deposition of gold and tin from aqueous and EG electrolytes proceeds with the depolarization effect of both Au(III) and Sn(IV) as a result of the formation of the alloy, the increase in the rate of tin cathodic reduction being more noticeable in case of EG solution. Formation of SnCl2EG(H2O) 2 + complex upon the dissolution of SnCl4 · 5H2O in glycol, the stability of the composition of tetracyanoaurate ions upon the dissolution of K[Au(CN)4], and the weakening of intermolecular interactions in EG with small amounts of water were revealed via IR spectroscopy. It is suggested that the depolarization effect is due not only to alloy formation, but also to the formation of SnCl2EG(H2O) 2 + cations, their association with Au(CN) 4 - anions, and a change in the mechanism of Au(III) and Sn(IV) reduction.

  7. Diamondoid-functionalized gold nanogaps as sensors for natural, mutated, and epigenetically modified DNA nucleotides.

    PubMed

    Sivaraman, Ganesh; Amorim, Rodrigo G; Scheicher, Ralph H; Fyta, Maria

    2016-05-21

    Modified tiny hydrogen-terminated diamond structures, known as diamondoids, show a high efficiency in sensing DNA molecules. These diamond cages, as recently proposed, could offer functionalization possibilities for gold junction electrodes. In this investigation, we report on diamondoid-functionalized electrodes, showing that such a device would have a high potential in sensing and sequencing DNA. The smallest diamondoid including an amine modification was chosen for the functionalization. Here, we report on the quantum tunneling signals across diamondoid-functionalized Au(111) electrodes. Our work is based on quantum-transport calculations and predicts the expected signals arising from different DNA units within the break junctions. Different gating voltages are proposed in order to tune the sensitivity of the functionalized electrodes with respect to specific nucleotides. The relation of this sensitivity to the coupling or decoupling of the electrodes is discussed. Our results also shed light on the sensing capability of such a device in distinguishing the DNA nucleotides, in their natural and mutated forms. PMID:27121677

  8. Enhanced detection sensitivity of Escherichia coli O157:H7 using surface-modified gold nanorods

    PubMed Central

    Ramasamy, Mohankandhasamy; Yi, Dong Kee; An, Seong Soo A

    2015-01-01

    Escherichia coli O157:H7 (O157) is a Gram negative and highly virulent bacteria found in food and water sources, and is a leading cause of chronic diseases worldwide. Diagnosis and prevention from the infection require simple and rapid analysis methods for the detection of pathogens, including O157. Endogenous membrane peroxidase, an enzyme present on the surface of O157, was used for the colorimetric detection of bacteria by catalytic oxidation of the peroxidase substrate. In this study, we have analyzed the impact of the synthesized bare gold nanorods (AuNRs) and silica-coated AuNRs on the growth of E. coli O157. Along with the membrane peroxidase activity of O157, other bacteria strains were analyzed. Different concentrations of nanorods were used to analyze the growth responses, enzymatic changes, and morphological alterations of bacteria by measuring optical density, 3,3′,5,5′-tetramethylbenzidine assay, flow cytometry analysis, and microscopy studies. The results revealed that O157 showed higher and continuous membrane peroxidase activity than other bacteria. Furthermore, O157 treated with bare AuNRs showed a decreased growth rate in comparison with the bacteria with surface modified AuNRs. Interestingly, silica-coated AuNRs favored the growth of bacteria and also increased membrane peroxidase activity. This result can be particularly important for the enzymatic analysis of surface treated AuNRs in various microbiological applicants. PMID:26347081

  9. Exonuclease I manipulating primer-modified gold nanoparticles for colorimetric telomerase activity assay.

    PubMed

    Zhang, Lei; Zhang, Sijin; Pan, Wei; Liang, Qingcheng; Song, Xingyu

    2016-03-15

    Telomerase is a widely accepted cancer biomarker. The conventional method for telomerase activity assay, the telomeric repeat amplification protocol (TRAP), is time-consuming and susceptible to contaminants. Therefore, development of simple and sensitive strategies for telomerase detection is still a challenging subject. Here we develop a highly sensitive method for telomerase detection based on primer-modified gold nanoparticles (GNPs) manipulated by exonuclease I (Exo I). In the absence of telomerase, Exo I digests the substrate nucleic acid on the surface of GNPs, inducing the GNPs' aggregation. In the presence of telomerase, the telomerase elongation products which fold into G-quadruplex are resistant to the digestion of Exo I, and protect the GNPs from aggregation. By using this method, we can detect telomerase activity in 100 HL-60 cancer cells mL(-1) by naked eyes, and the detection limit is 29 HL-60 cells mL(-1). This method is very simple and reliable, without any separation and amplification procedure. We also demonstrate the feasibility of this protocol for screening of telomerase inhibitors as anticancer agents. This method is promising to be applied in early clinical diagnosis and drug discovery. PMID:26402592

  10. Diamondoid-functionalized gold nanogaps as sensors for natural, mutated, and epigenetically modified DNA nucleotides

    NASA Astrophysics Data System (ADS)

    Sivaraman, Ganesh; Amorim, Rodrigo G.; Scheicher, Ralph H.; Fyta, Maria

    2016-05-01

    Modified tiny hydrogen-terminated diamond structures, known as diamondoids, show a high efficiency in sensing DNA molecules. These diamond cages, as recently proposed, could offer functionalization possibilities for gold junction electrodes. In this investigation, we report on diamondoid-functionalized electrodes, showing that such a device would have a high potential in sensing and sequencing DNA. The smallest diamondoid including an amine modification was chosen for the functionalization. Here, we report on the quantum tunneling signals across diamondoid-functionalized Au(111) electrodes. Our work is based on quantum-transport calculations and predicts the expected signals arising from different DNA units within the break junctions. Different gating voltages are proposed in order to tune the sensitivity of the functionalized electrodes with respect to specific nucleotides. The relation of this sensitivity to the coupling or decoupling of the electrodes is discussed. Our results also shed light on the sensing capability of such a device in distinguishing the DNA nucleotides, in their natural and mutated forms.

  11. Yeast-based Biochemical Oxygen Demand Sensors Using Gold-modified Boron-doped Diamond Electrodes.

    PubMed

    Ivandini, Tribidasari A; Harmesa; Saepudin, Endang; Einaga, Yasuaki

    2015-01-01

    A gold nanoparticle modified boron-doped diamond electrode was developed as a transducer for biochemical oxygen demand (BOD) measurements. Rhodotorula mucilaginosa UICC Y-181 was immobilized in a sodium alginate matrix, and used as a biosensing agent. Cyclic voltammetry was applied to study the oxygen reduction reaction at the electrode, while amperometry was employed to detect oxygen, which was not consumed by the microorganisms. The optimum waiting time of 25 min was observed using 1-mm thickness of yeast film. A comparison against the system with free yeast cells shows less sensitivity of the current responses with a linear dynamic range (R(2) = 0.99) of from 0.10 mM to 0.90 mM glucose (equivalent to 10 - 90 mg/L BOD) with an estimated limit of detection of 1.90 mg/L BOD. However, a better stability of the current responses could be achieved with an RSD of 3.35%. Moreover, less influence from the presence of copper ions was observed. The results indicate that the yeast-immobilized BOD sensors is more suitable to be applied in a real condition.

  12. Modified titanium surface with gelatin nano gold composite increases osteoblast cell biocompatibility

    NASA Astrophysics Data System (ADS)

    Lee, Young-Hee; Bhattarai, Govinda; Aryal, Santosh; Lee, Nan-Hee; Lee, Min-Ho; Kim, Tae-Gun; Jhee, Eun-Chung; Kim, Hak-Yong; Yi, Ho-Keun

    2010-08-01

    This study examined the gelatin nano gold (GnG) composite for surface modification of titanium in addition to insure biocompatibility on dental implants or biomaterials. The GnG composite was constructed by gelatin and hydrogen tetrachloroaurate in presence of reducing agent, sodium borohydrate (NabH 4). The GnG composite was confirmed by UV-VIS spectroscopy and transmission electron microscopy (TEM). A dipping method was used to modify the titanium surface by GnG composite. Surface was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The MC-3T3 E1 cell viability was assessed by trypan blue and the expression of proteins to biocompatibility were analyzed by Western blotting. The GnG composite showed well dispersed character, the strong absorption at 530 nm, roughness, regular crystal and clear C, Na, Cl, P, and Au signals onto titanium. Further, this composite allowed MC-3T3 E1 growth and viability compared to gelatin and pure titanium. It induced ERK activation and the expression of cell adherent molecules, FAK and SPARC, and growth factor, VEGF. However, GnG decreased the level of SAPK/JNK. This shows that GnG composite coated titanium surfaces have a good biocompatibility for osteoblast growth and attachment than in intact by simple and versatile dipping method. Furthermore, it offers good communication between cell and implant surfaces by regulating cell signaling and adherent molecules, which are useful to enhance the biocompatibility of titanium surfaces.

  13. Enhanced detection sensitivity of Escherichia coli O157:H7 using surface-modified gold nanorods.

    PubMed

    Ramasamy, Mohankandhasamy; Yi, Dong Kee; An, Seong Soo A

    2015-01-01

    Escherichia coli O157:H7 (O157) is a Gram negative and highly virulent bacteria found in food and water sources, and is a leading cause of chronic diseases worldwide. Diagnosis and prevention from the infection require simple and rapid analysis methods for the detection of pathogens, including O157. Endogenous membrane peroxidase, an enzyme present on the surface of O157, was used for the colorimetric detection of bacteria by catalytic oxidation of the peroxidase substrate. In this study, we have analyzed the impact of the synthesized bare gold nanorods (AuNRs) and silica-coated AuNRs on the growth of E. coli O157. Along with the membrane peroxidase activity of O157, other bacteria strains were analyzed. Different concentrations of nanorods were used to analyze the growth responses, enzymatic changes, and morphological alterations of bacteria by measuring optical density, 3,3',5,5'-tetramethylbenzidine assay, flow cytometry analysis, and microscopy studies. The results revealed that O157 showed higher and continuous membrane peroxidase activity than other bacteria. Furthermore, O157 treated with bare AuNRs showed a decreased growth rate in comparison with the bacteria with surface modified AuNRs. Interestingly, silica-coated AuNRs favored the growth of bacteria and also increased membrane peroxidase activity. This result can be particularly important for the enzymatic analysis of surface treated AuNRs in various microbiological applicants. PMID:26347081

  14. Electrochemically reduced graphene oxide-modified screen-printed carbon electrodes for a simple and highly sensitive electrochemical detection of synthetic colorants in beverages.

    PubMed

    Jampasa, Sakda; Siangproh, Weena; Duangmal, Kiattisak; Chailapakul, Orawon

    2016-11-01

    A simple and highly sensitive electrochemical sensor based on an electrochemically reduced graphene oxide-modified screen-printed carbon electrode (ERGO-SPCE) for the simultaneous determination of sunset yellow (SY) and tartrazine (TZ) was proposed. An ERGO film was coated onto the electrode surface using a cyclic voltammetric method and then characterized by scanning electron microscopy (SEM). In 0.1M phosphate buffer at a pH of 6, the two oxidation peaks of SY and TZ appeared separately at 0.41 and 0.70V, respectively. Surprisingly, the electrochemical response remarkably increased approximately 90- and 20-fold for SY and TZ, respectively, using the modified electrode in comparison to the unmodified electrode. The calibration curves exhibited linear ranges from 0.01 to 20.0µM for SY and from 0.02 to 20.0µM for TZ. The limits of detection were found to be 0.50 and 4.50nM (at S/N=3) for SY and TZ, respectively. Furthermore, this detection platform provided very high selectivity for the measurement of both colorants. This electrochemical sensor was successfully applied to determine the amount of SY and TZ in commercial beverages. Comparison of the results obtained from this proposed method to those obtained by an in-house standard technique proved that this developed method has good agreement in terms of accuracy for practical applications. This sensor offers an inexpensive, rapid and sensitive determination. The proposed system is therefore suitable for routine analysis and should be an alternative method for the analysis of food colorants.

  15. Electrochemically reduced graphene oxide-modified screen-printed carbon electrodes for a simple and highly sensitive electrochemical detection of synthetic colorants in beverages.

    PubMed

    Jampasa, Sakda; Siangproh, Weena; Duangmal, Kiattisak; Chailapakul, Orawon

    2016-11-01

    A simple and highly sensitive electrochemical sensor based on an electrochemically reduced graphene oxide-modified screen-printed carbon electrode (ERGO-SPCE) for the simultaneous determination of sunset yellow (SY) and tartrazine (TZ) was proposed. An ERGO film was coated onto the electrode surface using a cyclic voltammetric method and then characterized by scanning electron microscopy (SEM). In 0.1M phosphate buffer at a pH of 6, the two oxidation peaks of SY and TZ appeared separately at 0.41 and 0.70V, respectively. Surprisingly, the electrochemical response remarkably increased approximately 90- and 20-fold for SY and TZ, respectively, using the modified electrode in comparison to the unmodified electrode. The calibration curves exhibited linear ranges from 0.01 to 20.0µM for SY and from 0.02 to 20.0µM for TZ. The limits of detection were found to be 0.50 and 4.50nM (at S/N=3) for SY and TZ, respectively. Furthermore, this detection platform provided very high selectivity for the measurement of both colorants. This electrochemical sensor was successfully applied to determine the amount of SY and TZ in commercial beverages. Comparison of the results obtained from this proposed method to those obtained by an in-house standard technique proved that this developed method has good agreement in terms of accuracy for practical applications. This sensor offers an inexpensive, rapid and sensitive determination. The proposed system is therefore suitable for routine analysis and should be an alternative method for the analysis of food colorants. PMID:27591594

  16. Synthesis, spectroscopic characterization, electrochemical behavior and computational analysis of mixed diamine ligand gold(III) complexes: antiproliferative and in vitro cytotoxic evaluations against human cancer cell lines.

    PubMed

    Al-Jaroudi, Said S; Monim-ul-Mehboob, M; Altaf, Muhammad; Al-Saadi, Abdulaziz A; Wazeer, Mohammed I M; Altuwaijri, Saleh; Isab, Anvarhusein A

    2014-12-01

    The gold(III) complexes of the type [(DACH)Au(en)]Cl3, 1,2-Diaminocyclohexane ethylenediamine gold(III) chloride [where 1,2-DACH = cis-, trans-1,2- and S,S-1,2diaminocyclohexane and en = ethylenediamine] have been synthesized and characterized using various analytical and spectroscopic techniques including elemental analysis, UV-Vis and FTIR spectra; and solution as well as solid-state NMR measurements. The solid-state (13)C NMR shows that 1,2-diaminocyclohexane (1,2-DACH) and ethylenediamine (en) are strongly bound to the gold(III) center via N donor atoms. The stability of the mixed diamine ligand gold(III) was determined by (1)H and (13)C NMR spectra. Their electrochemical behavior was studied by cyclic voltammetry. The structural details and relative stabilities of the four possible isomers of the complexes were also reported at the B3LYP/LANL2DZ level of theory. The coordination sphere of these complexes around gold(III) center adopts distorted square planar geometry. The computational study also demonstrates that trans- conformations is slightly more stable than the cis-conformations. The antiproliferative effects and cytotoxic properties of the mixed diamine ligand gold(III) complexes were evaluated in vitro on human gastric SGC7901 and prostate PC3 cancer cells using MTT assay. The antiproliferative study of the gold(III) complexes on PC3 and SGC7901 cells indicate that complex 1 is the most effective antiproliferative agent among mixed ligand based gold(III) complexes 1-3. The IC50 data reveal that the in vitro cytotoxicity of complexes 1 and 3 against SGC7901 cancer cells are fairly better than that of cisplatin. PMID:25034122

  17. Electrochemical synthesis of nickel-iron layered double hydroxide: application as a novel modified electrode in electrocatalytic reduction of metronidazole.

    PubMed

    Nejati, Kamellia; Asadpour-Zeynali, Karim

    2014-02-01

    A new and simple approach based on the electrochemical method was used for preparation of reproducible nanostructure thin film of Ni/Fe-layered double hydroxides (Ni/Fe-LDH) on the glassy carbon electrode (GCE). The electrochemical behavior of the Ni/Fe-LDH deposited on GCE electrode is studied. Study of the scanning electron microscopy shows the formation of a nanostructure thin film on the glassy carbon electrode. Electrochemical experiments show that Ni/Fe-LDH modified glassy carbon electrode exhibits excellent electrocatalytic reduction activity with Metronidazole. The method was successfully applied for the analysis of Metronidazole in tablets. The results were favorably compared to those obtained by the reported BP method.

  18. Synthesis of netlike gold nanoparticles using ampicillin as a stabilizing reagent and its application

    SciTech Connect

    Song, Y.Z.; Zhou, J.F.; Song, Y.; Cheng, Z.P.; Xu, J.

    2012-12-15

    Graphical abstract: Electrochemical deposition of netlike gold nanoparticles (GNPs) on the surface of glassy carbon electrode and preparation of netlike GNPs in aqueous solution using ampicillin as a stabilizing reagent were proposed. The catalytic properties of netlike gold nanoparticles on the glassy carbon electrode for dopamine were demonstrated. The results indicate that the netlike gold nanoparticle modified electrode has an excellent repeatability and reproducibility. Display Omitted Highlights: ► Synthesis of netlike gold nanoparticles using ampicillin as a stabilizing reagent. ► Excellent repeatability and reproducibility of netlike gold nanoparticle modified glassy carbon electrode. ► The catalytic properties of netlike gold nanoparticle for dopamine. -- Abstract: Electrochemical deposition of netlike gold nanoparticles on the surface of glassy carbon electrode and preparation of netlike GNPs in aqueous solution using ampicillin as a stabilizing reagent were proposed. The netlike gold nanoparticles were characterized by scanning electron microscope, transmission electron microscope, infrared spectrometer, UV spectrophotometer, powder X-ray diffractometer and electrochemical analyzer. The catalysis of the netlike gold nanoparticles on the glassy carbon electrode for dopamine was demonstrated. The results indicate that the gold nanoparticle modified electrode has an excellent repeatability and reproducibility.

  19. Electrochemical immunosensors for antibodies to peanut allergen ara h2 using gold nanoparticle-peptide films.

    PubMed

    Liu, Hongyun; Malhotra, Ruchika; Peczuh, Mark W; Rusling, James F

    2010-07-01

    Life-threatening allergies to peanuts and tree nuts can be revealed by detecting antibodies (IgEs) to their allergens in patient serum. Herein, we compare several immunosensor-like methodologies for sensitive detection of antibodies to a peptide sequence from the major peanut allergen, Arachis hypogaea 2 (Ara h2). The sensors feature a synthetic peptide layer of the major IgE-binding epitope from Ara h2 attached to a dense gold nanoparticle (AuNP) film on a pyrolytic graphite (PG) electrode. The AuNP-peptide sensor was used to determine model chicken antipeanut antibodies (IgY) in serum. Faradaic and nonfaradaic impedance strategies were compared to amperometric detection. Measurements employed goat antichicken secondary antibodies (Ab(2)) labeled with horseradish peroxidase (HRP) to bind to IgY on the sensor and provide amplified signals. The best impedimetric sensor configuration featured HPR-catalyzed precipitation of the enzyme product onto the sensor measured by nonfaradaic impedance. This sensor configuration had the best detection limit (DL) of 5 pg mL(-1) and the best linear range of over 5 orders of magnitude (from 5 pg mL(-1) to 1 microg mL(-1)) for IgY antibody in undiluted calf serum. This DL was 100-fold lower than label-free impedimetric immunosensors (0.5 ng mL(-1)) and 60-fold lower than when using HRP-Ab(2) in amperometric immunosensors (0.3 ng mL(-1)).

  20. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-03-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL‑1, with a detection limit of 0.1 ng·mL‑1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples.

  1. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    PubMed Central

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-01-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL−1, with a detection limit of 0.1 ng·mL−1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples. PMID:27003798

  2. Alkanephosphonates on hafnium-modified gold: a new class of self-assembled organic monolayers.

    PubMed

    Jespersen, Michael L; Inman, Christina E; Kearns, Gregory J; Foster, Evan W; Hutchison, James E

    2007-03-14

    A new method for assembling organic monolayers on gold is reported that employs hafnium ions as linkers between a phosphonate headgroup and the gold surface. Monolayers of octadecylphosphonic acid (ODPA) formed on gold substrates that had been pretreated with hafnium oxychloride are representative of this new class of organic thin films. The monolayers are dense enough to completely block assembly of alkanethiols and resist displacement by alkanethiols. The composition and structure of the monolayers were investigated by contact angle goniometry, XPS, PM-IRRAS, and TOF-SIMS. From these studies, it was determined that this assembly strategy leads to the formation of ODPA monolayers similar in quality to those typically formed on metal oxide substrates. The assembly method allows for the ready generation of patterned surfaces that can be easily prepared by first patterning hafnium on the gold surface followed by alkanephosphonate assembly. Using the bifunctional (thiol-phosphonate) 2-mercaptoethylphosphonic acid (2-MEPA), we show that this new assembly chemistry is compatible with gold-thiol chemistry and use TOF-SIMS to show that the molecule attaches through the phosphonate functionality in the patterned region and through the thiol in the bare gold regions. These results demonstrate the possibility of functionalizing metal substrates with monolayers typically formed on metal oxide surfaces and show that hafnium-gold chemistry is complementary and orthogonal to well-established gold-thiol assembly strategies.

  3. Magnetic controlling of migration of DNA and proteins using one-step modified gold nanoparticles.

    PubMed

    Xu, Lu; Feng, Lei; Dong, Shuli; Hao, Jingcheng

    2015-06-01

    A protocol was developed for preparing magnetic gold nanoparticles via one-step modification with a paramagnetic cationic surfactant. These magnetic gold nanoparticles can bind to and manipulate a low strength magnetic field-based delivery of DNA and proteins powerfully and non-invasively. PMID:25847127

  4. A 3D Microfluidic Chip for Electrochemical Detection of Hydrolysed Nucleic Bases by a Modified Glassy Carbon Electrode

    PubMed Central

    Vlachova, Jana; Tmejova, Katerina; Kopel, Pavel; Korabik, Maria; Zitka, Jan; Hynek, David; Kynicky, Jindrich; Adam, Vojtech; Kizek, Rene

    2015-01-01

    Modification of carbon materials, especially graphene-based materials, has wide applications in electrochemical detection such as electrochemical lab-on-chip devices. A glassy carbon electrode (GCE) modified with chemically alternated graphene oxide was used as a working electrode (glassy carbon modified by graphene oxide with sulphur containing compounds and Nafion) for detection of nucleobases in hydrolysed samples (HCl pH = 2.9, 100 °C, 1 h, neutralization by NaOH). It was found out that modification, especially with trithiocyanuric acid, increased the sensitivity of detection in comparison with pure GCE. All processes were finally implemented in a microfluidic chip formed with a 3D printer by fused deposition modelling technology. As a material for chip fabrication, acrylonitrile butadiene styrene was chosen because of its mechanical and chemical stability. The chip contained the one chamber for the hydrolysis of the nucleic acid and another for the electrochemical detection by the modified GCE. This chamber was fabricated to allow for replacement of the GCE. PMID:25621613

  5. Chemically and compositionally modified solid solution disordered multiphase nickel hydroxide positive electrode for alkaline rechargeable electrochemical cells

    DOEpatents

    Ovshinsky, Stanford R.; Corrigan, Dennis; Venkatesan, Srini; Young, Rosa; Fierro, Christian; Fetcenko, Michael A.

    1994-01-01

    A high capacity, long cycle life positive electrode for use in an alkaline rechargeable electrochemical cell comprising: a solid solution nickel hydroxide material having a multiphase structure that comprises at least one polycrystalline .gamma.-phase including a polycrystalline .gamma.-phase unit cell comprising spacedly disposed plates with at least one chemical modifier incorporated around the plates, the plates having a range of stable intersheet distances corresponding to a 2.sup.+ oxidation state and a 3.5.sup.+, or greater, oxidation state; and at least one compositional modifier incorporated into the solid solution nickel hydroxide material to promote the multiphase structure.

  6. Enzyme-triggered tyramine-enzyme repeats on prussian blue-gold hybrid nanostructures for highly sensitive electrochemical immunoassay of tissue polypeptide antigen.

    PubMed

    Xu, Tisen; Zhang, Haiying; Li, Xuegui; Xie, Zhaohui; Li, Xiangyong

    2015-11-15

    A novel sandwich-type electrochemical immunoassay with sensitivity enhancement was developed for quantitative detection of tissue polypeptide antigen (TPA) by coupling with target-induced tyramine signal amplification on prussian blue-gold hybrid nanostructures. The immunosensor was prepared through immobilizing anti-TPA capture antibody on a cleaned screen-printed carbon electrode (SPCE). Prussian blue-gold hybrid nanostructures (PBGNS) labeled with horseradish peroxidase (HRP) and detection antibody were utilized as the signal-transduction tags. Upon target TPA introduction, the sandwiched immunocomplex was formed between capture antibody and detection antibody on the electrode. The carried HRP could trigger the formation of tyramine-HRP repeats on the PBGNS in the presence of H2O2. Using the doped prussian blue as the electron mediator, the conjugated HRP could catalyze the reduction of H2O2. Under the optimal conditions, the catalytic currents increased with the increasing target TPA in the dynamic range from 1.0 pg mL(-1) to 100 ng mL(-1) with a detection limit of 0.3 pg mL(-1). The reproducibility and specificity of the electrochemical immunoassay were acceptable. In addition, the contents of target TPA in nine human serum specimens were evaluated by using the developed electrochemical immunosensor, and the obtained results correlated well with those from commercially enzyme-linked immunosorbent assay (ELISA) method with a correlation coefficient of 0.9975.

  7. Detection of Ara h 1 (a major peanut allergen) in food using an electrochemical gold nanoparticle-coated screen-printed immunosensor.

    PubMed

    Alves, Rita C; Pimentel, Filipa B; Nouws, Henri P A; Marques, Raquel C B; González-García, María Begoña; Oliveira, M Beatriz P P; Delerue-Matos, Cristina

    2015-02-15

    A gold nanoparticle-coated screen-printed carbon electrode was used as the transducer in the development of an electrochemical immunosensor for Ara h 1 (a major peanut allergen) detection in food samples. Gold nanoparticles (average diameter = 32 nm) were electrochemically generated on the surface of screen-printed carbon electrodes. Two monoclonal antibodies were used in a sandwich-type immunoassay and the antibody-antigen interaction was electrochemically detected through stripping analysis of enzymatically (using alkaline phosphatase) deposited silver. The total time of the optimized immunoassay was 3h 50 min. The developed immunosensor allowed the quantification of Ara h 1 between 12.6 and 2000 ng/ml, with a limit of detection of 3.8 ng/ml, and provided precise (RSD <8.7%) and accurate (recovery >96.6%) results. The immunosensor was successfully applied to the analysis of complex food matrices (cookies and chocolate), being able to detect Ara h 1 in samples containing 0.1% of peanut.

  8. A novel method for simultaneous analysis of three β2-agonists in foods with the use of a gold-nanoparticle modified glassy carbon electrode and chemometrics.

    PubMed

    Lin, Xiaoyun; Ni, Yongnian; Li, Shuzhen; Kokot, Serge

    2012-05-01

    An electrochemical method involving a gold nanoparticle modified glassy carbon electrode (AuNPs/GCE) was researched and developed for the simultaneous analysis of three β(2)-agonists, ractopamine (RAC), salbutamol (SAL) and clenbuterol (CLB). The three analytes were electrocatalytically oxidized at the AuNP/GCE, which enhanced the oxidation peak current and influenced the shift of the oxidation potentials to lower values in comparison with the analysis involving only the GCE. The differential pulse stripping voltammetry (DPSV) voltammograms from the drug mixture produced complex, overlapping profiles, and chemometrics methods were applied for calibration modeling. The peak currents associated with RAC, SAL and CLB measurements were linear as a function of their concentrations (ranges within 0.005-0.150 μg mL(-1)); the detection limits for RAC, SAL and CLB were 2.4, 5.8 and 2.6 ng mL(-1), respectively. It was shown that satisfactory quantitative results were obtained with the use of the MVC1 package of chemometrics methods e.g. the PLS1 calibration model produced a relative prediction error (RPE(T)) of 7.0% and an average recovery of 97.6%. The above AuNP/GCE was successfully employed for the simultaneous analysis of RAC, SAL and CLB in pork meat, liver and pig feed samples.

  9. Simple flow injection for determination of sulfite by amperometric detection using glassy carbon electrode modified with carbon nanotubes-PDDA-gold nanoparticles.

    PubMed

    Amatatongchai, Maliwan; Sroysee, Wongduan; Chairam, Sanoe; Nacapricha, Duangjai

    2015-02-01

    A new approach is presented for sensitive and selective measurement of sulfite (SO3(2-)) in beverages based on a simple flow injection system with amperometric detection. In this work, the sulfite sensor was a glassy carbon electrode modified with multiwall carbon nanotubes-poly(diallyldimethylammonium chloride)-gold nanoparticles composites (CNTs-PDDA-AuNPs/GC). Electrochemical oxidation of sulfite with this electrode was first studied in 0.1M phosphate buffer (pH 7.0) using cyclic voltammetry. The results indicated that the CNTs-PDDA-AuNPs/GC electrode possesses electrocatalytic activity for the oxidation of sulfite with high sensitivity and selectivity. Sulfite was quantified using amperometric measurement with the new sensor at +0.4V vs Ag/AgCl in conjunction with flow injection. The linear working range for the quantitation of sulfite was 2-200 mg L(-1) (r(2)=0.998) with a detection limit of 0.03 mg L(-1) (3σ of blank) and an estimated precision of 1.5%.The proposed method was successfully applied to the determination of sulfite in fruit juices and wines with a sample throughput of 23 samples per hour.

  10. Simple flow injection for determination of sulfite by amperometric detection using glassy carbon electrode modified with carbon nanotubes-PDDA-gold nanoparticles.

    PubMed

    Amatatongchai, Maliwan; Sroysee, Wongduan; Chairam, Sanoe; Nacapricha, Duangjai

    2015-02-01

    A new approach is presented for sensitive and selective measurement of sulfite (SO3(2-)) in beverages based on a simple flow injection system with amperometric detection. In this work, the sulfite sensor was a glassy carbon electrode modified with multiwall carbon nanotubes-poly(diallyldimethylammonium chloride)-gold nanoparticles composites (CNTs-PDDA-AuNPs/GC). Electrochemical oxidation of sulfite with this electrode was first studied in 0.1M phosphate buffer (pH 7.0) using cyclic voltammetry. The results indicated that the CNTs-PDDA-AuNPs/GC electrode possesses electrocatalytic activity for the oxidation of sulfite with high sensitivity and selectivity. Sulfite was quantified using amperometric measurement with the new sensor at +0.4V vs Ag/AgCl in conjunction with flow injection. The linear working range for the quantitation of sulfite was 2-200 mg L(-1) (r(2)=0.998) with a detection limit of 0.03 mg L(-1) (3σ of blank) and an estimated precision of 1.5%.The proposed method was successfully applied to the determination of sulfite in fruit juices and wines with a sample throughput of 23 samples per hour. PMID:25435239

  11. Beyond the use of modifiers in selective alkyne hydrogenation: silver and gold nanocatalysts in flow mode for sustainable alkene production.

    PubMed

    Vilé, Gianvito; Pérez-Ramírez, Javier

    2014-11-21

    We report on the excellent stereo and chemoselectivity of nanosized silver and gold catalysts in the three-phase hydrogenation of acetylenic compounds under flow chemistry conditions. The materials featuring metal nanoparticles in the range of 2-21 nm were prepared by spray deposition or incipient wetness impregnation of silver nitrate and sol immobilisation of gold chloride on different carriers (Al2O3, SiO2, TiO2, and carbon), followed by activation in various atmospheres. The samples were characterised by ICP-OES, N2 sorption, XPS, HAADF-STEM, and HRTEM, and evaluated in a continuous-flow flooded-bed micro-reactor. Both metals display optimal activities for particles below 5 nm, enabling stable operation at T = 373 K and P = 10 bar. While the performance of the silver catalysts is less influenced by the support, the gold nanoparticles exhibit significant activity only when deposited on TiO2, likely due to the strong metal-support interaction. Hydrogenations of functionalised alkynes reveal that silver and gold match, and in some cases exceed, the selectivity of benchmark palladium-based catalysts. Furthermore, in contrast to Pd, the Ag and Au samples require no modifiers, which brings fundamental and practical simplifications for their understanding and large scale manufacture. Therefore, these materials could be advantageously used for the continuous production of olefinic intermediates in the fine chemical and pharmaceutical industries. PMID:25132414

  12. Electrochemical transduction of DNA hybridization at modified electrodes by using an electroactive pyridoacridone intercalator.

    PubMed

    Bouffier, Laurent; Wang, Bingquan Stuart; Roget, André; Livache, Thierry; Demeunynck, Martine; Mailley, Pascal

    2014-02-01

    A synthetic redox probe structurally related to natural pyridoacridones was designed and electrochemically characterised. These heterocycles behave as DNA intercalators due to their extended planar structure that promotes stacking in between nucleic acid base pairs. Electrochemical characterization by cyclic voltammetry revealed a quasi-reversible electrochemical behaviour occurring at a mild negative potential in aqueous solution. The study of the mechanism showed that the iminoquinone redox moiety acts similarly to quinone involving a two-electron reduction coupled with proton transfer. The easily accessible potential region with respect to aqueous electro-inactive window makes the pyridoacridone ring suitable for the indirect electrochemical detection of chemically unlabelled DNA. Its usefulness as electrochemical hybridization indicator was assessed on immobilised DNA and compared to doxorubicin. The voltamperometric response of the intercalator acts as an indicator of the presence of double-stranded DNA at the electrode surface and allows the selective transduction of immobilised oligonucleotide hybridization at both macro- and microscale electrodes.

  13. Bienzyme HRP-GOx-modified gold nanoelectrodes for the sensitive amperometric detection of glucose at low overpotentials.

    PubMed

    Delvaux, Marc; Walcarius, Alain; Demoustier-Champagne, Sophie

    2005-02-15

    Gold nanotubular electrode ensembles were prepared by using electroless deposition of the metal within the pores of polycarbonate track-etched membranes. Mono-enzyme (GOx) and monolayer/bilayer bienzyme (GOx/HRP) bioelectrodes were prepared by immobilizing the enzymes onto gold nanotubes surfaces modified with mercaptoethylamine. Batch amperometric responses to glucose for the different bioelectrodes were determined and compared. The response of the two geometries (monolayer and bilayer) of the bienzyme electrodes was shown to vary with regard to sensitivity at detection potentials above 0V. On the contrary, at detection potentials below 0V, no noticeable influence of the configuration of the bienzyme on the response intensity was observed. The mono-enzyme (650 microAmM-1 in benzoquinone (BQ) at -0.8 V versus Ag/AgCl) and the two bienzyme bioelectrodes (+/-400 microAmM-1 in hydroquinone (H2Q) at -0.2V versus Ag/AgCl) display remarkable sensitivities compared to a classical GOx-modified gold macroelectrode (13 microAmM-1 in BQ at -0.8 V versus Ag/AgCl). A remarkable feature of the bienzyme electrodes is the possibility to detect glucose at very low applied potentials where the noise level and interferences from other electro-oxidizable compounds are minimal. Another important characteristic of the monolayer bienzyme electrode is the possible existence of a direct electronic communication between HRP and the transducer surface.

  14. Modulation of electrochemical hydrogen evolution rate by araliphatic thiol monolayers on gold

    PubMed Central

    Muglali, Mutlu I.; Erbe, Andreas; Chen, Ying; Barth, Christoph; Koelsch, Patrick; Rohwerder, Michael

    2013-01-01

    Electroreductive desorption of a highly ordered self-assembled monolayer (SAM) formed by the araliphatic thiol (4-(4-(4-pyridyl)phenyl)phenyl)methanethiol leads to a concurrent rapid hydrogen evolution reaction (HER). The desorption process and resulting interfacial structure were investigated by voltammetric techniques, in situ spectroscopic ellipsometry, and in situ vibrational sum–frequency–generation (SFG) spectroscopy. Voltammetric experiments on SAM-modified electrodes exhibit extraordinarily high peak currents, which di er between Au(111) and polycrystalline Au substrates. Association of reductive desorption with HER is shown to be the origin of the observed excess cathodic charges. The studied SAM preserves its two–dimensional order near Au surface throughout a fast voltammetric scan even when the vertex potential is set several hundred millivolt beyond the desorption potential. A model is developed for the explanation of the observed rapid HER involving ordering and pre–orientation of water present in the nanometer–sized reaction volume between desorbed SAM and the Au electrode, by the structurally extremely stable monolayer, leading to the observed catalysis of the HER. PMID:24235778

  15. Modulation of electrochemical hydrogen evolution rate by araliphatic thiol monolayers on gold.

    PubMed

    Muglali, Mutlu I; Erbe, Andreas; Chen, Ying; Barth, Christoph; Koelsch, Patrick; Rohwerder, Michael

    2013-02-15

    Electroreductive desorption of a highly ordered self-assembled monolayer (SAM) formed by the araliphatic thiol (4-(4-(4-pyridyl)phenyl)phenyl)methanethiol leads to a concurrent rapid hydrogen evolution reaction (HER). The desorption process and resulting interfacial structure were investigated by voltammetric techniques, in situ spectroscopic ellipsometry, and in situ vibrational sum-frequency-generation (SFG) spectroscopy. Voltammetric experiments on SAM-modified electrodes exhibit extraordinarily high peak currents, which di er between Au(111) and polycrystalline Au substrates. Association of reductive desorption with HER is shown to be the origin of the observed excess cathodic charges. The studied SAM preserves its two-dimensional order near Au surface throughout a fast voltammetric scan even when the vertex potential is set several hundred millivolt beyond the desorption potential. A model is developed for the explanation of the observed rapid HER involving ordering and pre-orientation of water present in the nanometer-sized reaction volume between desorbed SAM and the Au electrode, by the structurally extremely stable monolayer, leading to the observed catalysis of the HER.

  16. Mechanical Strength and Stability of DNA-modified Gold Nanoparticle Systems

    NASA Astrophysics Data System (ADS)

    Lam, Letisha McLaughlin

    Systems in which gold nanoparticles (AuNPs) are functionalized with DNA have the potential for a broad range of applications in gene regulation therapies, drug delivery, sensing, innovative biomaterials and material templates. The use of DNA-modified gold nanoparticle (AuNP-DNA) systems is driven by their ease of assembly with bottom-up methods as well as the tunability of the systems' mechanical, optical, and electronic properties by exploiting AuNP characteristics and behavior in a multi-particle arrangement. Periodic arrangements of AuNPs precisely distributed through ligated DNA linkers may be assembled and used on relatively large length scales, on the order of hundreds of nanometers, for use in potential nanoscale technologies and applications. However, because of the size and heterogeneous composition of AuNP-DNA systems, their stability under mechanical loading is not well understood or quantified on relevant physical scales for these applications. Hence, a large-scale specialized finite-element predictive approach with a dislocation-density based crystalline plasticity has been used to investigate the mechanical stability of AuNP-DNA-ligand systems with AuNPs within the physical dimensions required for plasmon resonance. The crystalline formulation for the AuNPs accounts for multiple crystalline slip, dislocation-density evolution, lattice rotations, and large inelastic strains. A hypoelastic formulation was used for the DNA and the ligands. The nonlinear finite-element scheme is based on accounting for finite elastic and inelastic strains. These approaches were employed to predict and understand the fundamental scale-dependent microstructural behavior, the evolving heterogeneous microstructure, and localized phenomena that can contribute to failure initiation and instability. Each system was loaded using quasi-static plane strain tension and compression to simulate application loading conditions, and the elastic and inelastic evolutions were analyzed for

  17. Electroless Gold-Modified Diatoms as Surface-Enhanced Raman Scattering Supports.

    PubMed

    Pannico, Marianna; Rea, Ilaria; Chandrasekaran, Soundarrajan; Musto, Pellegrino; Voelcker, Nicolas H; De Stefano, Luca

    2016-12-01

    Porous biosilica from diatom frustules is well known for its peculiar optical and mechanical properties. In this work, gold-coated diatom frustules are used as low-cost, ready available, functional support for surface-enhanced Raman scattering. Due to the morphology of the nanostructured surface and the smoothness of gold deposition via an electroless process, an enhancement factor for the p-mercaptoaniline Raman signal of the order of 10(5) is obtained. PMID:27356562

  18. Electroless Gold-Modified Diatoms as Surface-Enhanced Raman Scattering Supports

    NASA Astrophysics Data System (ADS)

    Pannico, Marianna; Rea, Ilaria; Chandrasekaran, Soundarrajan; Musto, Pellegrino; Voelcker, Nicolas H.; De Stefano, Luca

    2016-06-01

    Porous biosilica from diatom frustules is well known for its peculiar optical and mechanical properties. In this work, gold-coated diatom frustules are used as low-cost, ready available, functional support for surface-enhanced Raman scattering. Due to the morphology of the nanostructured surface and the smoothness of gold deposition via an electroless process, an enhancement factor for the p-mercaptoaniline Raman signal of the order of 105 is obtained.

  19. Electroless Gold-Modified Diatoms as Surface-Enhanced Raman Scattering Supports.

    PubMed

    Pannico, Marianna; Rea, Ilaria; Chandrasekaran, Soundarrajan; Musto, Pellegrino; Voelcker, Nicolas H; De Stefano, Luca

    2016-12-01

    Porous biosilica from diatom frustules is well known for its peculiar optical and mechanical properties. In this work, gold-coated diatom frustules are used as low-cost, ready available, functional support for surface-enhanced Raman scattering. Due to the morphology of the nanostructured surface and the smoothness of gold deposition via an electroless process, an enhancement factor for the p-mercaptoaniline Raman signal of the order of 10(5) is obtained.

  20. Direct Electrochemistry of Cytochrome bo Oxidase at a series of Gold Nanoparticles-Modified Electrodes.

    PubMed

    Melin, Frederic; Meyer, Thomas; Lankiang, Styven; Choi, Sylvia K; Gennis, Robert B; Blanck, Christian; Schmutz, Marc; Hellwig, Petra

    2013-01-01

    New membrane-protein based electrodes were prepared incorporating cytochrome bo(3) from E. coli and gold nanoparticles. Direct electron transfer between the electrode and the immobilized enzymes was achieved, resulting in an electrocatalytic activity in presence of O(2). The size of the gold nanoparticles was shown to be important and smaller particles were shown to reduce the overpotential of the process. PMID:23335854

  1. The Application of Nafion Metal Catalyst Free Carbon Nanotube Modified Gold Electrode: Voltammetric Zinc Detection in Serum

    PubMed Central

    Yue, Wei; Bange, Adam; Riehl, Bill L.; Johnson, Jay M.; Papautsky, Ian; Heineman, William R.

    2013-01-01

    Metal catalyst free carbon nanotube (MCFCNT) whiskers were first used as an electrode modification material on a gold electrode surface for zinc voltammetric measurements. A composite film of Nafion and MCFCNT whiskers was applied to a gold electrode surface to form a mechanically stable sensor. The sensor was then used for zinc detection in both acetate buffer solution and extracted bovine serum solution. A limit of detection of 53 nM was achieved for a 120 s deposition time. The zinc in bovine serum was extracted via a double extraction procedure using dithizone in chloroform as a zinc chelating ligand. The modified electrode was found to be both reliable and sensitive for zinc measurements in both matrices. PMID:24436574

  2. Surface-enhanced Raman spectroscopy of cadmium sulfide/cadmium selenide superlattices formed on gold by electrochemical atomic-layer epitaxy

    NASA Astrophysics Data System (ADS)

    Zou, Shouzhong; Weaver, Michael J.

    1999-10-01

    The phonon properties of ultrathin CdS/CdSe superlattice films formed on gold by electrochemical atomic-layer epitaxy are characterized by means of surface-enhanced Raman spectroscopy (SERS). Substantial (15-25 cm -1) red-shifts in the CdS phonon frequencies are observed, whereas the CdSe frequencies are essentially unaltered, indicating that substantial crystallographic strain occurs in the former, but not the latter, superlattice component. The findings demonstrate the virtues of SERS for exploring the structure of such solid-solid interfaces with unique monolayer-level sensitivity.

  3. Highly sensitive interference-free electrochemical determination of pyridoxine at graphene modified electrode: Importance in Parkinson and Asthma treatments.

    PubMed

    Raj, M Amal; Gowthaman, N S K; John, S Abraham

    2016-07-15

    To reduce the side effects in the medication of Parkinson and Asthma, pyridoxine (PY) is administered along with l-3,4-dihydroxyphenyl alanine (l-dopa) and theophylline (TP), respectively. However, excessive dosage of PY leads to nervous disorder. Thus, a sensitive and selective electrochemical method was developed for the determination of PY in the presence of major interferences including TP, l-dopa, ascorbic acid (AA) and riboflavin (RB) using electrochemically reduced graphene oxide (ERGO) film modified glassy carbon electrode (GCE) in this paper. The ERGO fabrication process involves the nucleophilic substitution of graphene oxide at basic pH on amine terminal of 1,6-hexadiamine which was pre-assembled on GCE followed by electrochemical reduction. The electrocatalytic activity of the ERGO modified electrode was examined towards the oxidation of PY. It greatly enhanced the oxidation current of PY in contrast to bare and GO modified GCEs due to facile electron transfer besides π-π interaction between ERGO film and PY. Since TP and l-dopa drugs antagonize the drug action of PY, ERGO modified GCE was also used for the simultaneous determination of PY and l-dopa and PY and TP. Further, the selective determination of PY in the presence of other water soluble vitamins such as ascorbic acid and riboflavin was also demonstrated. Using amperometry, detection of 100nM PY was achieved and the detection limit was found to be 5.6×10(-8)M (S/N=3). The practical application of the present method was demonstrated by determining the concentration of PY in human blood serum and commercial drugs. PMID:27124811

  4. Nanostructured multilayer thin films of multiwalled carbon nanotubes/gold nanoparticles/glutathione for the electrochemical detection of dopamine

    NASA Astrophysics Data System (ADS)

    Detsri, Ekarat; Rujipornsakul, Sirilak; Treetasayoot, Tanapong; Siriwattanamethanon, Pawarit

    2016-10-01

    In the present study, multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs), and glutathione (GSH) were used to fabricate multilayer nanoscale thin films. The composite thin films were fabricated by layer-by-layer technique as the films were constructed by the alternate deposition of cationic and anionic polyelectrolytes. The MWCNTs were modified via a noncovalent surface modification method using poly(diallydimethylammonium chloride) to form a cationic polyelectrolyte. An anionic polyelectrolyte was prepared by the chemical reduction of HAuCl4 using sodium citrate as both the stabilizing and reducing agent to form anionic AuNPs. GSH was used as an electrocatalyst toward the electro-oxidation of dopamine. The constructed composite electrode exhibits excellent electrocatalytic activity toward dopamine with a short response time and a wide linear range from 1 to 100 μmol/L. The limits of detection and quantitation of dopamine are (0.316 ± 0.081) μmol/L and (1.054 ± 0.081) μmol/L, respectively. The method is satisfactorily applied for the determination of dopamine in plasma and urine samples to obtain the recovery in the range from 97.90% to 105.00%.

  5. Sub-femtomolar electrochemical detection of DNA hybridization based on latex/gold nanoparticle-assisted signal amplification.

    PubMed

    Pinijsuwan, Suttiporn; Rijiravanich, Patsamon; Somasundrum, Mithran; Surareungchai, Werasak

    2008-09-01

    We report a relatively simple electrostatic method for modifying submicrometer-size latex spheres with gold nanoparticles (AuNPs) based on layer-by-layer modification of the latex by polyelectrolytes. The AuNP coverages for 343- and 501-nm-diameter spheres were 4.0 x 10 (10) +/- 1.3 x 10 (10) and 8.2 x 10 (10) +/- 2.7 x 10 (10) particles cm (-2), respectively, which is an increase of 1 order of magnitude on the previously reported coverage at latex-AuNPs using streptavidin-biotin binding (Kawde, A.N.; Wang, J. Electroanalysis 2004, 16, 101-107). Due to the fact that the AuNPs used here are also of a larger size (mean diameter 15.5 +/- 1.6 nm, cf. 5 nm), this represents an increase of 2 orders of magnitude in the number of Au atoms delivered per sphere. The spheres were attached to DNA probes specific to E. coli and used to detect probe hybridization by dissolution of the AuNPs, followed by measurement of Au (3+) ions by anodic stripping voltammetry (ASV). Use of differential pulse voltammetry for the stripping step, along with optimization of the ASV conditions, enabled a detection limit of 0.5 fM, which is, to the best of our knowledge, equal or lower than previous voltammetric nanoparticle methods for detection of DNA hybridization.

  6. Signal amplification architecture for electrochemical aptasensor based on network-like thiocyanuric acid/gold nanoparticle/ssDNA.

    PubMed

    Chen, Zhengbo; Li, Lidong; Tian, Yu; Mu, Xiaojiao; Guo, Lin

    2012-01-01

    In this work, we described signal amplification architecture for electronic aptamer-based sensor (E-AB), which is applicable to a wide range of aptamers. Herein, we only take lysozyme as the representative sensing target. The amplification method was based on the network of thiocyanuric acid (TCA)/gold nanoparticles (AuNPs) modified with ssDNA. The binding event can be detected by a decrease in the integrated charge of the surface-bound [Ru(NH(3))(6)](3+) which electrostatically absorbed onto the negatively charged phosphate backbones of DNA. In the presence of target molecules, a large amount of TCA/AuNP/ssDNA network associated with [Ru(NH(3))(6)](3+) would be removed from the electrode surface, leading to a significant decrease of redox current. Cyclic voltammetry (CV) signals of [Ru(NH(3))(6)](3+) provides quantitative measures of the concentrations of lysozyme, with a linear calibration ranging from 5 pM to 1 nM and a detection limit is 0.1 pM. The detection limit of the proposed sensor is one order of magnitude and three orders of magnitude more sensitive than the detection limits in the absence of TCA (5 pM) and in the absence of TCA/AuNP/ssDNA network (0.5 nM). This amplification method is promising for broad potential application in clinic assay and various protein analysis.

  7. Modified enzyme-linked immunosorbent assay strategy using graphene oxide sheets and gold nanoparticles functionalized with different antibody types.

    PubMed

    Lin, Hongjun; Liu, Yingfu; Huo, Jingrui; Zhang, Aihong; Pan, Yiting; Bai, Haihong; Jiao, Zhang; Fang, Tian; Wang, Xin; Cai, Yun; Wang, Qingming; Zhang, Yangjun; Qian, Xiaohong

    2013-07-01

    Gold nanoparticles (GNPs) and graphene oxide (GO) sheets are excellent nano carriers in many analytical methods. In this study, a modified enzyme-linked immunosorbent assay (ELISA) strategy was developed using antibody-functionalized GO sheets and GNPs. This modification significantly reduced the limit of detection (LOD) and cost greatly of this assay. The applicability of the method was demonstrated by detecting HSP70 in a human serum sample. This result suggests that the 3G-ELISA method is feasible to detect an antigen in a complex mixture, and the LOD is up to 64-fold and the cost is as low as one-tenth of the conventional ELISA method.

  8. Modifying the chemistry of graphene with substrate selection: A study of gold nanoparticle formation

    NASA Astrophysics Data System (ADS)

    Zaniewski, Anna M.; Trimble, Christie J.; Nemanich, Robert J.

    2015-03-01

    Graphene and metal nanoparticle composites are a promising class of materials with unique electronic, optical, and chemical properties. In this work, graphene is used as a reducing surface to grow gold nanoparticles out of solution-based metal precursors. The nanoparticle formation is found to strongly depend upon the graphene substrate selection. The studied substrates include diamond, p-type silicon, aluminum oxide, lithium niobate, and copper. Our results indicate that the chemical properties of graphene depend upon this selection. For example, for the same reaction times and concentration, the reduction of gold chloride to gold nanoparticles on graphene/lithium niobate results in 3% nanoparticle coverage compared to 20% coverage on graphene/silicon and 60% on graphene/copper. On insulators, nanoparticles preferentially form on folds and edges. Energy dispersive X-ray analysis is used to confirm the nanoparticle elemental makeup.

  9. Modifying the chemistry of graphene with substrate selection: A study of gold nanoparticle formation

    SciTech Connect

    Zaniewski, Anna M.; Trimble, Christie J.; Nemanich, Robert J.

    2015-03-23

    Graphene and metal nanoparticle composites are a promising class of materials with unique electronic, optical, and chemical properties. In this work, graphene is used as a reducing surface to grow gold nanoparticles out of solution-based metal precursors. The nanoparticle formation is found to strongly depend upon the graphene substrate selection. The studied substrates include diamond, p-type silicon, aluminum oxide, lithium niobate, and copper. Our results indicate that the chemical properties of graphene depend upon this selection. For example, for the same reaction times and concentration, the reduction of gold chloride to gold nanoparticles on graphene/lithium niobate results in 3% nanoparticle coverage compared to 20% coverage on graphene/silicon and 60% on graphene/copper. On insulators, nanoparticles preferentially form on folds and edges. Energy dispersive X-ray analysis is used to confirm the nanoparticle elemental makeup.

  10. Electrochemical Characterization of Layer-By-Layer Assembled Ferrocene-Modified Linear Poly(ethylenimine)/Enzyme Bioanodes for Glucose Sensor and Biofuel Cell Applications.

    PubMed

    Godman, Nicholas P; DeLuca, Jared L; McCollum, Sean R; Schmidtke, David W; Glatzhofer, Daniel T

    2016-04-12

    Ferrocenylhexyl- and ferrocenylpropyl-modified linear poly(ethylenimine) (Fc-C6-LPEI, Fc-C3-LPEI) were used with periodate-modified glucose oxidase (p-GOX) in the layer-by-layer assembly of enzymatic bioanodes on gold. Fc-C6-LPEI/p-GOX and Fc-C3-LPEI/p-GOX films of 16 bilayers were capable of generating up to 381 ± 3 and 1417 ± 63 μA cm(-2), respectively, in response to glucose. These responses are greater than those of analogous bioanodes fabricated using conventional cross-linking techniques and are extremely high for planar, low surface area, single-enzyme electrodes. (Fc-C3-LPEI/p-GOX)8 films generated 86 ± 3 μW cm(-2) at pH 7.0 and 149 ± 7 μW cm(-2) at pH 5.0, when poised against an air-breathing platinum cathode in a compartment-less biofuel cell. An increase in power output with decreasing pH was shown to be a result of increases in the platinum cathode performance, indicating it is the rate-limiting electrode in the biofuel cells. The effect of fabrication wash time on the buildup of material at the electrode's surface was probed using cyclic voltammetry (CV) and constant potential amperometry. The use of electrochemical techniques as a diagnostic tool for studying the material deposition process is discussed. CV peak separation (ΔE), surface coverage of the electroactive ferrocene (ΓFc), and amperometric sensitivity of the enzyme to glucose (Jmax), studied as a function of numbers of bilayers, showed that physisorption of materials onto the surface results from initial patchy deposition, rather than in distinctly uniform layers.

  11. Electrochemical determination of the anticancer drug taxol at a ds-DNA modified pencil-graphite electrode and its application as a label-free electrochemical biosensor.

    PubMed

    Tajik, Somayeh; Taher, Mohammad Ali; Beitollahi, Hadi; Torkzadeh-Mahani, Mosoud

    2015-03-01

    In this study a novel biosensor for determination of taxol is described. The interaction of taxol with salmon-sperm double-stranded DNA (ds-DNA) based on the decreasing of the oxidation signals of guanine and adenine bases was studied electrochemically with a pencil-graphite electrode (PGE) using a differential pulse voltammetry (DPV) method. The decreases in the intensity of the guanine and adenine oxidation signals after interaction with taxol were used as indicator signals for the sensitive determination of taxol. DPV exhibits a linear dynamic range of 2.0×10(-7)-1.0×10(-5) M for taxol with a detection limit of 8.0×10(-8) M. Finally, this modified electrode was used for determination of taxol in some real samples.

  12. The utilization of SiNWs/AuNPs-modified indium tin oxide (ITO) in fabrication of electrochemical DNA sensor.

    PubMed

    Rashid, Jahwarhar Izuan Abdul; Yusof, Nor Azah; Abdullah, Jaafar; Hashim, Uda; Hajian, Reza

    2014-12-01

    This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0-178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4°C in silica gel.

  13. Phosphomolybdic acid functionalized graphene loading copper nanoparticles modified electrodes for non-enzymatic electrochemical sensing of glucose.

    PubMed

    Xu, Jiaoyan; Cao, Xiyue; Xia, Jianfei; Gong, Shida; Wang, Zonghua; Lu, Lin

    2016-08-31

    A sensitive non-enzymatic glucose electrochemical biosensor (Cu/PMo12-GR/GCE) was developed based on the combination of copper nanoparticles (CuNPs) and phosphomolybdic acid functionalized graphene (PMo12-GR). PMo12-GR films were modified on the surface of glassy carbon electrode (GCE) through electrostatic self-assembly with the aid of poly diallyl dimethyl ammonium chloride (PDDA). Then CuNPs were successfully decorated onto the PMo12-GR modified GCE through electrodeposition. The morphology of Cu/PMo12-GR/GCE was characterized by scanning electron microscope (SEM). Cyclic voltammetry (CV) and chronoamperometry were used to investigate the electrochemical performances of the biosensor. The results indicated that the modified electrode displayed a synergistic effect of PMo12-GR sheets and CuNPs towards the electro-oxidation of glucose in the alkaline solution. At the optimal detection potential of 0.50 V, the response towards glucose presented a linear response ranging from 0.10 μM to 1.0 mM with a detection limit of 3.0 × 10(-2) μM (S/N = 3). In addition, Cu/PMo12-GR/GCE possessed a high selectivity, good reproducibility, excellent stability and acceptable recovery, which indicating the potential application in clinical field. PMID:27506342

  14. Electrochemical Cathodic Polarization, a Simplified Method That Can Modified and Increase the Biological Activity of Titanium Surfaces: A Systematic Review

    PubMed Central

    2016-01-01

    Background The cathodic polarization seems to be an electrochemical method capable of modifying and coat biomolecules on titanium surfaces, improving the surface activity and promoting better biological responses. Objective The aim of the systematic review is to assess the scientific literature to evaluate the cellular response produced by treatment of titanium surfaces by applying the cathodic polarization technique. Data, Sources, and Selection The literature search was performed in several databases including PubMed, Web of Science, Scopus, Science Direct, Scielo and EBSCO Host, until June 2016, with no limits used. Eligibility criteria were used and quality assessment was performed following slightly modified ARRIVE and SYRCLE guidelines for cellular studies and animal research. Results Thirteen studies accomplished the inclusion criteria and were considered in the review. The quality of reporting studies in animal models was low and for the in vitro studies it was high. The in vitro and in vivo results reported that the use of cathodic polarization promoted hydride surfaces, effective deposition, and adhesion of the coated biomolecules. In the experimental groups that used the electrochemical method, cellular viability, proliferation, adhesion, differentiation, or bone growth were better or comparable with the control groups. Conclusions The use of the cathodic polarization method to modify titanium surfaces seems to be an interesting method that could produce active layers and consequently enhance cellular response, in vitro and in vivo animal model studies. PMID:27441840

  15. Electrochemical Aptasensor for Endocrine Disrupting 17β-Estradiol Based on a Poly(3,4-ethylenedioxylthiopene)-Gold Nanocomposite Platform

    PubMed Central

    Olowu, Rasaq A.; Arotiba, Omotayo; Mailu, Stephen N.; Waryo, Tesfaye T.; Baker, Priscilla; Iwuoha, Emmanuel

    2010-01-01

    A simple and highly sensitive electrochemical DNA aptasensor with high affinity for endocrine disrupting 17β-estradiol, was developed. Poly(3,4-ethylenedioxylthiophene) (PEDOT) doped with gold nanoparticles (AuNPs) was electrochemically synthesized and employed for the immobilization of biotinylated aptamer towards the detection of the target. The diffusion coefficient of the nanocomposite was 6.50 × 10−7 cm2 s−1, which showed that the nanocomposite was highly conducting. Electrochemical impedance investigation also revealed the catalytic properties of the nanocomposite with an exchange current value of 2.16 × 10−4 A, compared to 2.14 × 10−5 A obtained for the bare electrode. Streptavidin was covalently attached to the platform using carbodiimide chemistry and the aptamer immobilized via streptavidin—biotin interaction. The electrochemical signal generated from the aptamer–target molecule interaction was monitored electrochemically using cyclic voltammetry and square wave voltammetry in the presence of [Fe(CN)6]−3/−4 as a redox probe. The signal observed shows a current decrease due to interference of the bound 17β-estradiol. The current drop was proportional to the concentration of 17β-estradiol. The PEDOT/AuNP platform exhibited high electroactivity, with increased peak current. The platform was found suitable for the immobilization of the DNAaptamer. The aptasensor was able to distinguish 17β-estradiol from structurally similar endocrine disrupting chemicals denoting its specificity to 17β-estradiol. The detectable concentration range of the 17β-estradiol was 0.1 nM–100 nM, with a detection limit of 0.02 nM. PMID:22163445

  16. Gold nanoparticles-induced enhancement of the analytical response of an electrochemical biosensor based on an organic-inorganic hybrid composite material.

    PubMed

    Barbadillo, M; Casero, E; Petit-Domínguez, M D; Vázquez, L; Pariente, F; Lorenzo, E

    2009-12-15

    The design and characterization of a new organic-inorganic hybrid composite material for glucose electrochemical sensing are described. This material is based on the entrapment of both gold nanoparticles (AuNPs) and glucose oxidase, which was chosen as a model, into a sol-gel matrix. The addition of spectroscopic grade graphite to this system, which confers conductivity, leads to the development of a material particularly attractive for electrochemical biosensor fabrication. The characterization of the hybrid composite material was performed using atomic force microscopy and scanning electron microscopy techniques. This composite material was applied to the determination of glucose in presence of hydroxymethylferrocene as a redox mediator. The system exhibits a clear electrocatalytic activity towards glucose, allowing its determination at 250 mV vs Ag/AgCl. The performance of the resulting enzyme biosensor was evaluated in terms of sensitivity, detection limit, linear response range, stability and accuracy. Finally, the enhancement of the analytical response of the resulting biosensor induced by the presence of gold nanoparticles was evaluated by comparison with a similar organic-inorganic hybrid composite material without AuNPs.

  17. Beyond the use of modifiers in selective alkyne hydrogenation: silver and gold nanocatalysts in flow mode for sustainable alkene production

    NASA Astrophysics Data System (ADS)

    Vilé, Gianvito; Pérez-Ramírez, Javier

    2014-10-01

    We report on the excellent stereo and chemoselectivity of nanosized silver and gold catalysts in the three-phase hydrogenation of acetylenic compounds under flow chemistry conditions. The materials featuring metal nanoparticles in the range of 2-21 nm were prepared by spray deposition or incipient wetness impregnation of silver nitrate and sol immobilisation of gold chloride on different carriers (Al2O3, SiO2, TiO2, and carbon), followed by activation in various atmospheres. The samples were characterised by ICP-OES, N2 sorption, XPS, HAADF-STEM, and HRTEM, and evaluated in a continuous-flow flooded-bed micro-reactor. Both metals display optimal activities for particles below 5 nm, enabling stable operation at T = 373 K and P = 10 bar. While the performance of the silver catalysts is less influenced by the support, the gold nanoparticles exhibit significant activity only when deposited on TiO2, likely due to the strong metal-support interaction. Hydrogenations of functionalised alkynes reveal that silver and gold match, and in some cases exceed, the selectivity of benchmark palladium-based catalysts. Furthermore, in contrast to Pd, the Ag and Au samples require no modifiers, which brings fundamental and practical simplifications for their understanding and large scale manufacture. Therefore, these materials could be advantageously used for the continuous production of olefinic intermediates in the fine chemical and pharmaceutical industries.We report on the excellent stereo and chemoselectivity of nanosized silver and gold catalysts in the three-phase hydrogenation of acetylenic compounds under flow chemistry conditions. The materials featuring metal nanoparticles in the range of 2-21 nm were prepared by spray deposition or incipient wetness impregnation of silver nitrate and sol immobilisation of gold chloride on different carriers (Al2O3, SiO2, TiO2, and carbon), followed by activation in various atmospheres. The samples were characterised by ICP-OES, N2 sorption

  18. Ambient Filtration Method To Rapidly Prepare Highly Conductive, Paper-Based Porous Gold Films for Electrochemical Biosensing.

    PubMed

    Guntupalli, Bhargav; Liang, Pingping; Lee, Jung-Hoon; Yang, Yuehai; Yu, Haixiang; Canoura, Juan; He, Jin; Li, Wenzhi; Weizmann, Yossi; Xiao, Yi

    2015-12-16

    Thin gold films offer intriguing material properties for potential applications including fuel cells, supercapacitors, and electronic and photonic devices. We describe here an ambient filtration method that provides a simple and novel way to generate rapidly porous and thin gold films without the need for sophisticated instruments, clean-room environments, and any postgrowth process or sintering steps. Using this approach, we can fabricate highly conductive gold films composed of gold nanoparticles layered atop a matrix of metallic single-walled carbon nanotubes on mixed cellulose ester filter paper within 20 min. These hybrid films (thickness ∼40 nm) exhibit fast electron transfer and excellent electrocatalytic properties that are similar to purchased gold films, but with a larger electroactive surface that lends itself to more sensitive analyte detection. We used the neurotransmitters dopamine and serotonin as benchmark analytes to demonstrate that our hybrid gold films can clearly discriminate the presence of both molecules in a mixture with resolution that greatly exceeds that of either purchased gold slides or electrodeposited gold films. Importantly, we postulate that this new approach could readily be generalized for the rapid fabrication of films from various other metals under ambient conditions, and could also be used as a prelude to transferring the resulting films onto glass or other flexible substrates.

  19. Electrochemical and morphological investigation of silver and zinc modified calcium phosphate bioceramic coatings on metallic implant materials.

    PubMed

    Furko, M; Jiang, Y; Wilkins, T A; Balázsi, C

    2016-05-01

    In our research nanostructured silver and zinc doped calcium-phosphate (CaP) bioceramic coatings were prepared on commonly used orthopaedic implant materials (Ti6Al4V). The deposition process was carried out by the pulse current technique at 70 °C from electrolyte containing the appropriate amount of Ca(NO3)2 and NH4H2PO4 components. During the electrochemical deposition Ag(+) and Zn(2+) ions were introduced into the solution. The electrochemical behaviour and corrosion rate of the bioceramic coatings were investigated by potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) measurements in conventional Ringer's solution in a three electrode open cell. The coating came into contact with the electrolyte and corrosion occurred during immersion. In order to achieve antimicrobial properties, it is important to maintain a continuous release of silver ions into physiological media, while the bioactive CaP layer enhances the biocompatibility properties of the layer by fostering the bone cell growth. The role of Zn(2+) is to shorten wound healing time. Morphology and composition of coatings were studied by Scanning Electron Microscopy, Transmission Electron Microscopy and Energy-dispersive X-ray spectroscopy. Differential thermal analyses (DTA) were performed to determine the thermal stability of the pure and modified CaP bioceramic coatings while the structure and phases of the layers were characterized by X-ray diffraction (XRD) measurements.

  20. Electrochemical Determination of Chlorpyrifos on a Nano-TiO₂Cellulose Acetate Composite Modified Glassy Carbon Electrode.

    PubMed

    Kumaravel, Ammasai; Chandrasekaran, Maruthai

    2015-07-15

    A rapid and simple method of determination of chlorpyrifos is important in environmental monitoring and quality control. Electrochemical methods for the determination of pesticides are fast, sensitive, reproducible, and cost-effective. The key factor in electrochemical methods is the choice of suitable electrode materials. The electrode materials should have good stability, reproducibility, more sensitivity, and easy method of preparation. Mercury-based electrodes have been widely used for the determination of chlorpyrifos. From an environmental point of view mercury cannot be used. In this study a biocompatible nano-TiO2/cellulose acetate modified glassy carbon electrode was prepared by a simple method and used for the electrochemical sensing of chlorpyrifos in aqueous methanolic solution. Electroanalytical techniques such as cyclic voltammetry, differential pulse voltammetry, and amperometry were used in this work. This electrode showed very good stability, reproducibility, and sensitivity. A well-defined peak was obtained for the reduction of chlorpyrifos in cyclic voltammetry and differential pulse voltammetry. A smooth noise-free current response was obtained in amperometric analysis. The peak current obtained was proportional to the concentration of chlorpyrifos and was used to determine the unknown concentration of chlorpyrifos in the samples. Analytical parameters such as LOD, LOQ, and linear range were estimated. Analysis of real samples was also carried out. The results were validated through HPLC. This composite electrode can be used as an alternative to mercury electrodes reported in the literature.

  1. Electrochemical and morphological investigation of silver and zinc modified calcium phosphate bioceramic coatings on metallic implant materials.

    PubMed

    Furko, M; Jiang, Y; Wilkins, T A; Balázsi, C

    2016-05-01

    In our research nanostructured silver and zinc doped calcium-phosphate (CaP) bioceramic coatings were prepared on commonly used orthopaedic implant materials (Ti6Al4V). The deposition process was carried out by the pulse current technique at 70 °C from electrolyte containing the appropriate amount of Ca(NO3)2 and NH4H2PO4 components. During the electrochemical deposition Ag(+) and Zn(2+) ions were introduced into the solution. The electrochemical behaviour and corrosion rate of the bioceramic coatings were investigated by potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) measurements in conventional Ringer's solution in a three electrode open cell. The coating came into contact with the electrolyte and corrosion occurred during immersion. In order to achieve antimicrobial properties, it is important to maintain a continuous release of silver ions into physiological media, while the bioactive CaP layer enhances the biocompatibility properties of the layer by fostering the bone cell growth. The role of Zn(2+) is to shorten wound healing time. Morphology and composition of coatings were studied by Scanning Electron Microscopy, Transmission Electron Microscopy and Energy-dispersive X-ray spectroscopy. Differential thermal analyses (DTA) were performed to determine the thermal stability of the pure and modified CaP bioceramic coatings while the structure and phases of the layers were characterized by X-ray diffraction (XRD) measurements. PMID:26952421

  2. pH-insensitive fabrication of gold nanoparticles with high concentration by ultrasound-assisted electrochemical process via aid of chitosan

    SciTech Connect

    Yang, Kuang-Hsuan; Liu, Yu-Chuan; Hsu, Ting-Chu; Tsai, Huei-Ian

    2010-01-15

    In this work, we report a new pathway to prepare pure gold nanoparticles with high concentrations in acid solutions via the aid of chitosan without the addition of other stabilizers and reductants based on electrochemical methods. Interestingly, this fabrication of gold nanoparticles with high concentrations in solutions is pH-insensitive. The characteristics of prepared gold nanoparticles were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (HRXPS) measurements. Experimental results indicate the concentration and the particle size of Au nanoparticles prepared in 0.1N HCl are ca. 50 ppm and 12 nm in diameter, respectively. Similar experiment performed in 0.1N NaCl with the aid of chitosan shows that the corresponding concentration of prepared Au nanoparticles is ca. 100 ppm. Further similar experiments performed in 0.1N HCl and 0.1N NaCl without the aid of chitosan show that the corresponding concentrations of prepared Au nanoparticles are ca. 1 and 60 ppm, respectively.

  3. Target-induced formation of gold amalgamation on DNA-based sensing platform for electrochemical monitoring of mercury ion coupling with cycling signal amplification strategy.

    PubMed

    Chen, Jinfeng; Tang, Juan; Zhou, Jun; Zhang, Lan; Chen, Guonan; Tang, Dianping

    2014-01-31

    Heavy metal ion pollution poses severe risks in human health and environmental pollutant, because of the likelihood of bioaccumulation and toxicity. Driven by the requirement to monitor trace-level mercury ion (Hg(2+)), herein we construct a new DNA-based sensor for sensitive electrochemical monitoring of Hg(2+) by coupling target-induced formation of gold amalgamation on DNA-based sensing platform with gold amalgamation-catalyzed cycling signal amplification strategy. The sensor was simply prepared by covalent conjugation of aminated poly-T(25) oligonucleotide onto the glassy carbon electrode by typical carbodiimide coupling. Upon introduction of target analyte, Hg(2+) ion was intercalated into the DNA polyion complex membrane based on T-Hg(2+)-T coordination chemistry. The chelated Hg(2+) ion could induce the formation of gold amalgamation, which could catalyze the p-nitrophenol with the aid of NaBH4 and Ru(NH3)6(3+) for cycling signal amplification. Experimental results indicated that the electronic signal of our system increased with the increasing Hg(2+) level in the sample, and has a detection limit of 0.02nM with a dynamic range of up to 1000nM Hg(2+). The strategy afforded exquisite selectivity for Hg(2+) against other environmentally related metal ions. In addition, the methodology was evaluated for the analysis of Hg(2+) in spiked tap-water samples, and the recovery was 87.9-113.8%. PMID:24439499

  4. Electrochemical determination of Sudan I in food products using a carbon nanotube-ionic liquid composite modified electrode.

    PubMed

    Liu, Benzhi; Yin, Chuntao; Wang, Min

    2014-01-01

    A sensitive and convenient electrochemical method was developed for the determination of Sudan I using a carbon nanotube-ionic liquid composite modified electrode with the enhancement effect of cetyltrimethyl ammonium bromide (CTAB). The modified electrode exhibited an obvious electrocatalytic activity towards the oxidation of Sudan I, and the oxidation peak current significantly increased in the presence of CTAB. The experimental parameters, such as solution pH, concentration of CTAB and accumulation time, were optimised for Sudan I determination. The oxidation peak current showed a linear relationship with the concentration of Sudan I in the range of 3.0 × 10(-8) to 3.1 × 10(-6) mol l(-1), with a detection limit of 8.0 × 10(-9) mol l(-1). The proposed method was successfully applied for the determination of Sudan I in food products of ketchup and chilli sauce. PMID:25254422

  5. The electrochemical oxidation of troxerutin and its sensitive determination in pharmaceutical dosage forms at PVP modified carbon paste electrode.

    PubMed

    Yang, Xiaofeng; Wang, Fang; Hu, Shengshui

    2006-09-01

    The voltammetric responses of troxerutin were investigated at polyvinylpyrrolidone (cross-linked) (PVP) modified carbon paste electrode (CPE) in 0.1 mol/L KCl by several electrochemical techniques. A well-defined oxidation peak was observed at about 0.97 V. Compared with poor responses of troxerutin at bare electrode that at this modified electrode has been greatly improved. It is PVP that enhances the adsorption of troxerutin to electrode surface based on their hydrophobic property. Under some optimized experimental conditions, a simple and sensitive electroanalytical method was developed for the quantitative analysis of troxerutin. A very low detection limit of 5.0 x 10(-9)mol/L was obtained for 5 min accumulation at open circuit (S/N=3). This proposed method was successfully applied to the detection of troxerutin in pharmaceutical dosage forms and satisfying results had been obtained.

  6. Electrochemically triggered release of human insulin from an insulin-impregnated reduced graphene oxide modified electrode.

    PubMed

    Teodorescu, Florina; Rolland, Laure; Ramarao, Viswanatha; Abderrahmani, Amar; Mandler, Daniel; Boukherroub, Rabah; Szunerits, Sabine

    2015-09-28

    An electrochemical insulin-delivery system based on reduced graphene oxide impregnated with insulin is described. Upon application of a potential pulse of -0.8 V for 30 min, up to 70 ± 4% of human insulin was released into a physiological medium while preserving its biological activity.

  7. Bisphosphonate-modified gold nanoparticles: a useful vehicle to study the treatment of osteonecrosis of the femoral head

    NASA Astrophysics Data System (ADS)

    Fanord, Fedena; Fairbairn, Korie; Kim, Harry; Garces, Amanda; Bhethanabotla, Venkat; Gupta, Vinay K.

    2011-01-01

    Legg-Calvé-Perthes disease (LCPD) is a juvenile form of osteonecrosis of the femoral head that presents in children aged 2-14 years. To date, there is no effective medical therapy for treating LCPD largely due to an inability to modulate the repair process, including the predominance of bone resorption. This investigation aims to evaluate the feasibility of using gold nanoparticles (GNPs) that are surface modified with a bisphosphonate compound for the treatment of osteonecrosis at the cellular level. Studies have found osteoclast-mediated resorption to be a process that contributes significantly to the pathogenesis of femoral head deformities arising from Perthes disease. Our in vitro model was designed to elucidate the effect of alendronate-(a bisphosphonate) modified GNPs, on osteoclastogenesis and osteoclast function. RAW 264.7 macrophage cells were cultured with recombinant mouse receptor activator of NF-κB ligand (RANKL), which stimulates osteoclastogenesis, and were then treated with alendronate-modified GNPs for 24, 48, and 72 h. Cell proliferation, osteoclast function, and osteoclast morphology were evaluated by trypan blue dye exclusion assay, tartrate-resistant acid phosphatase (TRAP) staining, and transmission electron microscopy (TEM) imaging. Comparative studies were performed with GNPs that were only stabilized with citrate ions and with alendronate alone. Neither osteoclastogenesis nor osteoclast function were adversely affected by the presence of the citrate-GNP. Alendronate-modified GNPs had an enhanced effect on inducing osteoclast apoptosis and impairing osteoclast function when compared to unbound alendronate populations.

  8. Enzyme immunoassay using a reusable extended-gate field-effect-transistor sensor with a ferrocenylalkanethiol-modified gold electrode.

    PubMed

    Kamahori, Masao; Ishige, Yu; Shimoda, Maki

    2008-09-01

    A reusable extended-gate field-effect transistor (FET) sensor with an 11-ferrocenyl-1-undecanethiol (11-FUT) modified gold electrode was developed for applying to enzyme immunoassay. It was found that the 11-FUT modified FET sensor detected a thiol compound 50 times or more repeatedly after a treatment with a 5% hydrogen peroxide solution. The gate-voltage shift of the FET sensor showed a fairly good linearity (R(2) = 0.998) within a range from 10(-2) to 10(-6) M on the concentration of 6-hydroxyl-1-hexanethiol, which is a thiol compound, at a Nernstian response of 58.5 mV/decade. The FET-based immunoassay was constructed by combining the 11-FUT modified-FET sensor with the enzyme-linked immunosorbent assay (ELISA), in which the enzyme chemistry of acetylcholinesterase (AChE) was used to generate a thiol compound. The 11-FUT modified FET sensor with an AC voltage at 1 MHz superimposed onto the reference electrode detected the AChE-catalyzed product corresponding to a serum concentration of interleukin 1beta from 10 to 5000 pg/mL. In addition, all measurements were successfully performed by using the same FET-sensor chip after a treatment with a 5% hydrogen peroxide solution. PMID:18781015

  9. CdS quantum dots modified CuO inverse opal electrodes for ultrasensitive electrochemical and photoelectrochemical biosensor.

    PubMed

    Xia, Lei; Xu, Lin; Song, Jian; Xu, Ru; Liu, Dali; Dong, Biao; Song, Hongwei

    2015-06-04

    The CuO inverse opal photonic crystals (IOPCs) were synthesized by the sol-gel method and modified with CdS quantum dots by successive ionic layer adsorption and reaction (SILAR). CdS QDs modified CuO IOPCs FTO electrodes of different SILAR cycles were fabricated and their electrochemical properties were studied by cyclic voltammetry (CV) and chronoamperometry (I-t). Structure and morphology of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution TEM (HRTEM), Energy-dispersive X-ray analysis (EDX) and X-ray diffraction pattern (XRD). The result indicated that the structure of IOPCs and loading of CdS QDs could greatly improve the electrochemical properties. Three SILAR cycles of CdS QDs sensitization was the optimum condition for preparing electrodes, it exhibited a sensitivity of 4345 μA mM(-1) cm(-2) to glucose with a 0.15 μM detection limit (S/N= 3) and a linear range from 0.15 μM to 0.5 mM under a working potential of +0.7 V. It also showed strong stability, good reproducibility, excellent selectivity and fast amperometric response. This work provides a promising approach for realizing excellent photoelectrochemical nonenzymatic glucose biosensor of similar composite structure.

  10. CdS quantum dots modified CuO inverse opal electrodes for ultrasensitive electrochemical and photoelectrochemical biosensor.

    PubMed

    Xia, Lei; Xu, Lin; Song, Jian; Xu, Ru; Liu, Dali; Dong, Biao; Song, Hongwei

    2015-01-01

    The CuO inverse opal photonic crystals (IOPCs) were synthesized by the sol-gel method and modified with CdS quantum dots by successive ionic layer adsorption and reaction (SILAR). CdS QDs modified CuO IOPCs FTO electrodes of different SILAR cycles were fabricated and their electrochemical properties were studied by cyclic voltammetry (CV) and chronoamperometry (I-t). Structure and morphology of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution TEM (HRTEM), Energy-dispersive X-ray analysis (EDX) and X-ray diffraction pattern (XRD). The result indicated that the structure of IOPCs and loading of CdS QDs could greatly improve the electrochemical properties. Three SILAR cycles of CdS QDs sensitization was the optimum condition for preparing electrodes, it exhibited a sensitivity of 4345 μA mM(-1) cm(-2) to glucose with a 0.15 μM detection limit (S/N= 3) and a linear range from 0.15 μM to 0.5 mM under a working potential of +0.7 V. It also showed strong stability, good reproducibility, excellent selectivity and fast amperometric response. This work provides a promising approach for realizing excellent photoelectrochemical nonenzymatic glucose biosensor of similar composite structure. PMID:26042520

  11. CdS quantum dots modified CuO inverse opal electrodes for ultrasensitive electrochemical and photoelectrochemical biosensor

    PubMed Central

    Xia, Lei; Xu, Lin; Song, Jian; Xu, Ru; Liu, Dali; Dong, Biao; Song, Hongwei

    2015-01-01

    The CuO inverse opal photonic crystals (IOPCs) were synthesized by the sol-gel method and modified with CdS quantum dots by successive ionic layer adsorption and reaction (SILAR). CdS QDs modified CuO IOPCs FTO electrodes of different SILAR cycles were fabricated and their electrochemical properties were studied by cyclic voltammetry (CV) and chronoamperometry (I–t). Structure and morphology of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution TEM (HRTEM), Energy-dispersive X-ray analysis (EDX) and X-ray diffraction pattern (XRD). The result indicated that the structure of IOPCs and loading of CdS QDs could greatly improve the electrochemical properties. Three SILAR cycles of CdS QDs sensitization was the optimum condition for preparing electrodes, it exhibited a sensitivity of 4345 μA mM-1 cm-2 to glucose with a 0.15 μM detection limit (S/N= 3) and a linear range from 0.15 μM to 0.5 mM under a working potential of +0.7 V. It also showed strong stability, good reproducibility, excellent selectivity and fast amperometric response. This work provides a promising approach for realizing excellent photoelectrochemical nonenzymatic glucose biosensor of similar composite structure. PMID:26042520

  12. Simultaneous electrochemical detection of dopamine and ascorbic acid using an iron oxide/reduced graphene oxide modified glassy carbon electrode.

    PubMed

    Peik-See, Teo; Pandikumar, Alagarsamy; Nay-Ming, Huang; Hong-Ngee, Lim; Sulaiman, Yusran

    2014-08-19

    The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe3O4/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe3O4 nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe3O4/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The electrochemical studies revealed that the Fe3O4/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe3O4 and rGO. This implies that Fe3O4/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1-9 mM and 0.5-100 µM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3) was found to be 0.42 and 0.12 µM for AA and DA, respectively.

  13. Simultaneous Electrochemical Detection of Dopamine and Ascorbic Acid Using an Iron Oxide/Reduced Graphene Oxide Modified Glassy Carbon Electrode

    PubMed Central

    Peik-See, Teo; Pandikumar, Alagarsamy; Nay-Ming, Huang; Hong-Ngee, Lim; Sulaiman, Yusran

    2014-01-01

    The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe3O4/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe3O4 nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe3O4/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The electrochemical studies revealed that the Fe3O4/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe3O4 and rGO. This implies that Fe3O4/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 μM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3) was found to be 0.42 and 0.12 μM for AA and DA, respectively. PMID:25195850

  14. Development of gold nanoparticles modified screen-printed carbon electrode for the analysis of thiram, disulfiram and their derivative in food using ultra-high performance liquid chromatography.

    PubMed

    Charoenkitamorn, Kanokwan; Chailapakul, Orawon; Siangproh, Weena

    2015-01-01

    For the first time, gold nanoparticles (AuNPs) modified screen-printed carbon electrode (SPCE) was developed as working electrode in ultra-high performance liquid chromatography (UHPLC) coupled with electrochemical detection (UHPLC-ED) for simultaneous determination of thiram, disulfiram, and N,N-diethyl-N',N'-dimethylthiuram disulfide, their derivative compound. The separation was performed in reversed-phase mode using C18 column, mobile phase consisting of 55:45 (v/v) ratio of 0.05 M phosphate buffer solution (pH 5) and acetonitrile at a flow rate of 1.5 mL min(-1). For the detection part, the amperometric detection was chosen with a detection potential of 1.2 V vs. Ag/AgCl. Under the optimal conditions, the good linear relationship was obtained in the range of 0.07-15, 0.07-12, and 0.5-15 µg mL(-1) (correlation coefficient more than 0.9900) for thiram, N,N-diethyl-N',N'-dimethylthiuram disulfide, and disulfiram, respectively. The limits of detection (LODs) of thiram, N,N-diethyl-N',N'-dimethylthiuram disulfide, and disulfiram were 0.022, 0.023, and 0.165 µg mL(-1), respectively. Moreover, this method was successfully applied for the detection of these compounds in real samples (apple, grape and lettuce) with the recoveries ranging from 94.3% to 108.8%. To validate this developed method, a highly quantitative agreement was clearly observed compared to standard UHPLC-UV system. Therefore, the proposed electrode can be effectively used as an alternative electrode in UHPLC-ED for rapid, selective, highly sensitive, and simultaneous determination of thiram, disulfiram, and N,N-diethyl-N',N'-dimethylthiuram disulfide.

  15. Development of gold nanoparticles modified screen-printed carbon electrode for the analysis of thiram, disulfiram and their derivative in food using ultra-high performance liquid chromatography.

    PubMed

    Charoenkitamorn, Kanokwan; Chailapakul, Orawon; Siangproh, Weena

    2015-01-01

    For the first time, gold nanoparticles (AuNPs) modified screen-printed carbon electrode (SPCE) was developed as working electrode in ultra-high performance liquid chromatography (UHPLC) coupled with electrochemical detection (UHPLC-ED) for simultaneous determination of thiram, disulfiram, and N,N-diethyl-N',N'-dimethylthiuram disulfide, their derivative compound. The separation was performed in reversed-phase mode using C18 column, mobile phase consisting of 55:45 (v/v) ratio of 0.05 M phosphate buffer solution (pH 5) and acetonitrile at a flow rate of 1.5 mL min(-1). For the detection part, the amperometric detection was chosen with a detection potential of 1.2 V vs. Ag/AgCl. Under the optimal conditions, the good linear relationship was obtained in the range of 0.07-15, 0.07-12, and 0.5-15 µg mL(-1) (correlation coefficient more than 0.9900) for thiram, N,N-diethyl-N',N'-dimethylthiuram disulfide, and disulfiram, respectively. The limits of detection (LODs) of thiram, N,N-diethyl-N',N'-dimethylthiuram disulfide, and disulfiram were 0.022, 0.023, and 0.165 µg mL(-1), respectively. Moreover, this method was successfully applied for the detection of these compounds in real samples (apple, grape and lettuce) with the recoveries ranging from 94.3% to 108.8%. To validate this developed method, a highly quantitative agreement was clearly observed compared to standard UHPLC-UV system. Therefore, the proposed electrode can be effectively used as an alternative electrode in UHPLC-ED for rapid, selective, highly sensitive, and simultaneous determination of thiram, disulfiram, and N,N-diethyl-N',N'-dimethylthiuram disulfide. PMID:25476326

  16. RGD peptide-modified dendrimer-entrapped gold nanoparticles enable highly efficient and specific gene delivery to stem cells.

    PubMed

    Kong, Lingdan; Alves, Carla S; Hou, Wenxiu; Qiu, Jieru; Möhwald, Helmuth; Tomás, Helena; Shi, Xiangyang

    2015-03-01

    We report the use of arginine-glycine-aspartic (Arg-Gly-Asp, RGD) peptide-modified dendrimer-entrapped gold nanoparticles (Au DENPs) for highly efficient and specific gene delivery to stem cells. In this study, generation 5 poly(amidoamine) dendrimers modified with RGD via a poly(ethylene glycol) (PEG) spacer and with PEG monomethyl ether were used as templates to entrap gold nanoparticles (AuNPs). The native and the RGD-modified PEGylated dendrimers and the respective well characterized Au DENPs were used as vectors to transfect human mesenchymal stem cells (hMSCs) with plasmid DNA (pDNA) carrying both the enhanced green fluorescent protein and the luciferase (pEGFPLuc) reporter genes, as well as pDNA encoding the human bone morphogenetic protein-2 (hBMP-2) gene. We show that all vectors are capable of transfecting the hMSCs with both pDNAs. Gene transfection using pEGFPLuc was demonstrated by quantitative Luc activity assay and qualitative evaluation by fluorescence microscopy. For the transfection with hBMP-2, the gene delivery efficiency was evaluated by monitoring the hBMP-2 concentration and the level of osteogenic differentiation of the hMSCs via alkaline phosphatase activity, osteocalcin secretion, calcium deposition, and von Kossa staining assays. Our results reveal that the stem cell gene delivery efficiency is largely dependent on the composition and the surface functionality of the dendrimer-based vectors. The coexistence of RGD and AuNPs rendered the designed dendrimeric vector with specific stem cell binding ability likely via binding of integrin receptor on the cell surface and improved three-dimensional conformation of dendrimers, which is beneficial for highly efficient and specific stem cell gene delivery applications. PMID:25658033

  17. Optimized dendrimer-encapsulated gold nanoparticles and enhanced carbon nanotube nanoprobes for amplified electrochemical immunoassay of E. coli in dairy product based on enzymatically induced deposition of polyaniline.

    PubMed

    Zhang, Xinai; Shen, Jianzhong; Ma, Haile; Jiang, Yuxiang; Huang, Chenyong; Han, En; Yao, Boshui; He, Yunyao

    2016-06-15

    A highly sensitive immunosensor was reported for Escherichia coli assay in dairy product based on electrochemical measurement of polyaniline (PAn) that was catalytically deposited by horseradish peroxidase (HRP) labels. Herein, the immunosensor was developed by using poly(amidoamine) dendrimer-encapsulated gold nanoparticles (PAMAM(Au)) as sensing platform. Importantly, the optimal HAuCl4/PAMAM ratio was investigated to design the efficient PAMAM(Au) nanocomposites. The nanocomposites were proven to not only increase the amount of immobilized capture antibody (cAb), but also accelerate the electron transfer process. Moreover, the {dAb-CNT-HRP} nanoprobes were prepared by exploiting the amplification effect of multiwalled carbon nanotubes (CNTs) for loading detection antibody (dAb) and enormous HRP labels. After a sandwich immunoreaction, the quantitatively captured nanoprobes could catalyze oxidation aniline to produce electroactive PAn for electrochemical measurement. On the basis of signal amplification of the PAMAM(Au)-based immunosensor and the {dAb-CNT-HRP} nanoprobes, the proposed strategy exhibited a linear relationship between the peak current of PAn and the logarithmic value of E. coli concentration ranging from 1.0 × 10(2) to 1.0 × 10(6) cfu mL(-1) with a detection limit of 50 cfu mL(-1) (S/N=3), and the electrochemical detection of E. coli could be achieved in 3h. The electrochemical immunosensor was also used to determine E. coli in dairy product (pure fresh milk, infant milk powder, yogurt in shelf-life and expired yogurt), and the recoveries of standard additions were in the range of 96.8-108.7%. Overall, this method gave a useful protocol for E. coli assay with high sensitivity, acceptable accuracy and satisfying stability, and thus provided a powerful tool to estimate the quality of dairy product. PMID:26908184

  18. Nitrogen-doped multiple graphene aerogel/gold nanostar as the electrochemical sensing platform for ultrasensitive detection of circulating free DNA in human serum.

    PubMed

    Ruiyi, Li; Ling, Liu; Hongxia, Bei; Zaijun, Li

    2016-05-15

    Graphene aerogel has attracted increasing attention due to its large specific surface area, high-conductivity and electronic interaction. The paper reported a facile synthesis of nitrogen-doped multiple graphene aerogel/gold nanostar (termed as N-doped MGA/GNS) and its use as the electrochemical sensing platform for detection of double stranded (dsDNA). On the one hand, the N-doped MGA offers a much better electrochemical performance compared with classical graphene aerogel. Interestingly, the performance can be enhanced by only increasing the cycle number of graphene oxide gelation. On the other hand, the hybridization with GNS further enhances the electrocatalytic activity towards Fe(CN)6(3-/4-). In addition, the N-doped MGA/GNS provides a well-defined three-dimensional architecture. The unique structure make it is easy to combine with dsDNA to form the electroactive bioconjugate. The integration not only triggers an ultrafast DNA electron and charge transfer, but also realizes a significant synergy between N-doped MGA, GNS and dsDNA. As a result, the electrochemical sensor based on the hybrid exhibits highly sensitive differential pulse voltammetric response (DPV) towards dsDNA. The DPV signal linearly increases with the increase of dsDNA concentration in the range from 1.0×10(-)(21) g ml(-)(1) to 1.0×10(-16) g ml(-1) with the detection limit of 3.9×10(-22) g ml(-1) (S/N=3). The sensitivity is much more than that of all reported DNA sensors. The analytical method was successfully applied in the electrochemical detection of circulating free DNA in human serum. The study also opens a window on the electrical properties of multiple graphene aerogel and DNA as well their hybrids to meet the needs of further applications as special nanoelectronics in molecule diagnosis, bioanalysis and catalysis. PMID:26745792

  19. Nitrogen-doped multiple graphene aerogel/gold nanostar as the electrochemical sensing platform for ultrasensitive detection of circulating free DNA in human serum.

    PubMed

    Ruiyi, Li; Ling, Liu; Hongxia, Bei; Zaijun, Li

    2016-05-15

    Graphene aerogel has attracted increasing attention due to its large specific surface area, high-conductivity and electronic interaction. The paper reported a facile synthesis of nitrogen-doped multiple graphene aerogel/gold nanostar (termed as N-doped MGA/GNS) and its use as the electrochemical sensing platform for detection of double stranded (dsDNA). On the one hand, the N-doped MGA offers a much better electrochemical performance compared with classical graphene aerogel. Interestingly, the performance can be enhanced by only increasing the cycle number of graphene oxide gelation. On the other hand, the hybridization with GNS further enhances the electrocatalytic activity towards Fe(CN)6(3-/4-). In addition, the N-doped MGA/GNS provides a well-defined three-dimensional architecture. The unique structure make it is easy to combine with dsDNA to form the electroactive bioconjugate. The integration not only triggers an ultrafast DNA electron and charge transfer, but also realizes a significant synergy between N-doped MGA, GNS and dsDNA. As a result, the electrochemical sensor based on the hybrid exhibits highly sensitive differential pulse voltammetric response (DPV) towards dsDNA. The DPV signal linearly increases with the increase of dsDNA concentration in the range from 1.0×10(-)(21) g ml(-)(1) to 1.0×10(-16) g ml(-1) with the detection limit of 3.9×10(-22) g ml(-1) (S/N=3). The sensitivity is much more than that of all reported DNA sensors. The analytical method was successfully applied in the electrochemical detection of circulating free DNA in human serum. The study also opens a window on the electrical properties of multiple graphene aerogel and DNA as well their hybrids to meet the needs of further applications as special nanoelectronics in molecule diagnosis, bioanalysis and catalysis.

  20. Optimized dendrimer-encapsulated gold nanoparticles and enhanced carbon nanotube nanoprobes for amplified electrochemical immunoassay of E. coli in dairy product based on enzymatically induced deposition of polyaniline.

    PubMed

    Zhang, Xinai; Shen, Jianzhong; Ma, Haile; Jiang, Yuxiang; Huang, Chenyong; Han, En; Yao, Boshui; He, Yunyao

    2016-06-15

    A highly sensitive immunosensor was reported for Escherichia coli assay in dairy product based on electrochemical measurement of polyaniline (PAn) that was catalytically deposited by horseradish peroxidase (HRP) labels. Herein, the immunosensor was developed by using poly(amidoamine) dendrimer-encapsulated gold nanoparticles (PAMAM(Au)) as sensing platform. Importantly, the optimal HAuCl4/PAMAM ratio was investigated to design the efficient PAMAM(Au) nanocomposites. The nanocomposites were proven to not only increase the amount of immobilized capture antibody (cAb), but also accelerate the electron transfer process. Moreover, the {dAb-CNT-HRP} nanoprobes were prepared by exploiting the amplification effect of multiwalled carbon nanotubes (CNTs) for loading detection antibody (dAb) and enormous HRP labels. After a sandwich immunoreaction, the quantitatively captured nanoprobes could catalyze oxidation aniline to produce electroactive PAn for electrochemical measurement. On the basis of signal amplification of the PAMAM(Au)-based immunosensor and the {dAb-CNT-HRP} nanoprobes, the proposed strategy exhibited a linear relationship between the peak current of PAn and the logarithmic value of E. coli concentration ranging from 1.0 × 10(2) to 1.0 × 10(6) cfu mL(-1) with a detection limit of 50 cfu mL(-1) (S/N=3), and the electrochemical detection of E. coli could be achieved in 3h. The electrochemical immunosensor was also used to determine E. coli in dairy product (pure fresh milk, infant milk powder, yogurt in shelf-life and expired yogurt), and the recoveries of standard additions were in the range of 96.8-108.7%. Overall, this method gave a useful protocol for E. coli assay with high sensitivity, acceptable accuracy and satisfying stability, and thus provided a powerful tool to estimate the quality of dairy product.

  1. Electropolymerization of a calix[4]arene modified by N-substituted pyrrole moieties. New sensitive layer for ionic electrochemical detection

    NASA Astrophysics Data System (ADS)

    Buffenoir, A.; Bidan, G.

    1998-06-01

    A calix[4]arene modified by grafting N-substituted pyrrole moieties at the upper rim was synthetised. Electropolymerisation of this new calix[4]arene in a Bu4NClO4 (10-1 M) - CH3CN solution is described. The obtained film presents a rather stable electroactivity to electrochemical cycling but its growing is limited to a few monolayers. It's the first example of homopolymerisation of a calix[4]arene modified by electropolymerisable monomers. Un calix[4]arène modifié sur sa couronne supérieure par des pyrroles N-substitués a été synthétisé. Son électropolymérisation en milieu Bu4NClO4 (10-1 M) - CH3CN par balayage de potentiels est décrite. Le film obtenu présente une électroactivité assez stable au cyclage électrochimique mais sa croissance est limitée à quelques monocouches. C'est le premier exemple d'homopolymérisation d'un calix[4]arène modifié par des monomères électropolymérisables.

  2. An electrochemical biosensor for rapid detection of E. coli O157:H7 with highly efficient bi-functional glucose oxidase-polydopamine nanocomposites and Prussian blue modified screen-printed interdigitated electrodes.

    PubMed

    Xu, Meng; Wang, Ronghui; Li, Yanbin

    2016-09-21

    The presence of pathogenic bacteria in foods has always been a great threat to the wellbeing of people and the revenue of food manufacturers. Therefore, the demand for advanced detection methods that can sensitively and rapidly detect these pathogens has been of great importance. This study reports an electrochemical biosensor for rapid detection of E. coli O157:H7 with the integration of bifunctional glucose oxidase (GOx)-polydopamine (PDA) based polymeric nanocomposites (PMNCs) and Prussian blue (PB) modified screen-printed interdigitated microelectrodes (SP-IDMEs). The core-shell magnetic beads (MBs)-GOx@PDA PMNCs were first synthesized by the self-polymerization of dopamine (DA). Gold nanoparticles (AuNPs) were dispersed on the surface of PMNCs through biochemical synthesis to achieve further highly efficient adsorption of antibodies (ABs) and GOx. The final product ABs/GOxext/AuNPs/MBs-GOx@PDA PMNCs served as the carrier to separate target bacteria from food matrices as well as the amplifier for electrochemical measurement. The unbound PMNCs were separated by a filtration step and transferred into glucose solution to allow the enzymatic reaction to occur. The change of the current response was measured with an electrochemical detector using PB-modified SP-IDMEs. The constructed biosensor has been proven to be able to detect E. coli O157:H7 with the detection limit of 10(2) cfu ml(-1). The bifunctional PMNCs contain a high load of enzyme and can optimally utilize the binding sites on bacterial cells, which efficiently amplify the signals for measurement. The biosensor in this study exhibited good specificity, reproducibility, and stability and is expected to have a great impact on applications in the detection of foodborne pathogens. PMID:27358917

  3. An electrochemical biosensor for rapid detection of E. coli O157:H7 with highly efficient bi-functional glucose oxidase-polydopamine nanocomposites and Prussian blue modified screen-printed interdigitated electrodes.

    PubMed

    Xu, Meng; Wang, Ronghui; Li, Yanbin

    2016-09-21

    The presence of pathogenic bacteria in foods has always been a great threat to the wellbeing of people and the revenue of food manufacturers. Therefore, the demand for advanced detection methods that can sensitively and rapidly detect these pathogens has been of great importance. This study reports an electrochemical biosensor for rapid detection of E. coli O157:H7 with the integration of bifunctional glucose oxidase (GOx)-polydopamine (PDA) based polymeric nanocomposites (PMNCs) and Prussian blue (PB) modified screen-printed interdigitated microelectrodes (SP-IDMEs). The core-shell magnetic beads (MBs)-GOx@PDA PMNCs were first synthesized by the self-polymerization of dopamine (DA). Gold nanoparticles (AuNPs) were dispersed on the surface of PMNCs through biochemical synthesis to achieve further highly efficient adsorption of antibodies (ABs) and GOx. The final product ABs/GOxext/AuNPs/MBs-GOx@PDA PMNCs served as the carrier to separate target bacteria from food matrices as well as the amplifier for electrochemical measurement. The unbound PMNCs were separated by a filtration step and transferred into glucose solution to allow the enzymatic reaction to occur. The change of the current response was measured with an electrochemical detector using PB-modified SP-IDMEs. The constructed biosensor has been proven to be able to detect E. coli O157:H7 with the detection limit of 10(2) cfu ml(-1). The bifunctional PMNCs contain a high load of enzyme and can optimally utilize the binding sites on bacterial cells, which efficiently amplify the signals for measurement. The biosensor in this study exhibited good specificity, reproducibility, and stability and is expected to have a great impact on applications in the detection of foodborne pathogens.

  4. Facile formation of dendrimer-stabilized gold nanoparticles modified with diatrizoic acid for enhanced computed tomography imaging applications

    NASA Astrophysics Data System (ADS)

    Peng, Chen; Li, Kangan; Cao, Xueyan; Xiao, Tingting; Hou, Wenxiu; Zheng, Linfeng; Guo, Rui; Shen, Mingwu; Zhang, Guixiang; Shi, Xiangyang

    2012-10-01

    We report a facile approach to forming dendrimer-stabilized gold nanoparticles (Au DSNPs) through the use of amine-terminated fifth-generation poly(amidoamine) (PAMAM) dendrimers modified by diatrizoic acid (G5.NH2-DTA) as stabilizers for enhanced computed tomography (CT) imaging applications. In this study, by simply mixing G5.NH2-DTA dendrimers with gold salt in aqueous solution at room temperature, dendrimer-entrapped gold nanoparticles (Au DENPs) with a mean core size of 2.5 nm were able to be spontaneously formed. Followed by an acetylation reaction to neutralize the dendrimer remaining terminal amines, Au DSNPs with a mean size of 6 nm were formed. The formed DTA-containing [(Au0)50-G5.NHAc-DTA] DSNPs were characterized via different techniques. We show that the Au DSNPs are colloid stable in aqueous solution under different pH and temperature conditions. In vitro hemolytic assay, cytotoxicity assay, flow cytometry analysis, and cell morphology observation reveal that the formed Au DSNPs have good hemocompatibility and are non-cytotoxic at a concentration up to 3.0 μM. X-ray absorption coefficient measurements show that the DTA-containing Au DSNPs have enhanced attenuation intensity, much higher than that of [(Au0)50-G5.NHAc] DENPs without DTA or Omnipaque at the same molar concentration of the active element (Au or iodine). The formed DTA-containing Au DSNPs can be used for CT imaging of cancer cells in vitro as well as for blood pool CT imaging of mice in vivo with significantly improved signal enhancement. With the two radiodense elements of Au and iodine incorporated within one particle, the formed DTA-containing Au DSNPs may be applicable for CT imaging of various biological systems with enhanced X-ray attenuation property and detection sensitivity.We report a facile approach to forming dendrimer-stabilized gold nanoparticles (Au DSNPs) through the use of amine-terminated fifth-generation poly(amidoamine) (PAMAM) dendrimers modified by diatrizoic acid

  5. Electrochemical detection of nitrite on poly(pyronin Y)/graphene nanocomposites modified ITO substrate

    NASA Astrophysics Data System (ADS)

    Şinoforoğlu, Mehmet; Dağcı, Kader; Alanyalıoğlu, Murat; Meral, Kadem

    2016-06-01

    The present study reports on an easy preparation of poly(pyronin Y)/graphene (poly(PyY)/graphene) nanocomposites thin films on indium tin oxide coated glass substrates (ITO). The thin films of poly(PyY)/graphene nanocomposites are prepared by a novel method consisting of three steps; (i) preparation of graphene oxide (GO) thin films on ITO by spin-coating method, (ii) self-assembly of PyY molecules from aqueous solution onto the GO thin film, (iii) surface-confined electropolymerization (SCEP) of the adsorbed PyY molecules on the GO thin film. The as-prepared poly(PyY)/graphene nanocomposites thin films are characterized by using electroanalytical and spectroscopic techniques. Afterwards, the graphene-based polymeric dye thin film on ITO is used as an electrode in an electrochemical cell. Its performance is tested for electrochemical detection of nitrite. Under optimized conditions, the electrocatalytical effect of the nanocomposites thin film through electrochemical oxidation of nitrite is better than that of GO coated ITO.

  6. A novel nanogold-single wall carbon nanotube modified sensor for the electrochemical determination of 8-hydroxyguanine, a diabetes risk biomarker.

    PubMed

    Bishnoi, Sunita; Goyal, Rajendra N; Shim, Yoon-Bo

    2014-10-01

    An electrochemical study of the oxidation of 8-hydroxyguanine (8-OH-Gua) at gold nanoparticles attached to single walled carbon nanotube modified edge plane pyrolytic graphite electrode (AuNP-SWCNT/EPPGE) has been carried out to develop a method for the self diagnosis of diabetes. The level of 8-OH-Gua, an important biomarker of oxidative DNA damage, is higher in urine of diabetic patients than control subjects. A detailed comparison has been made between the square wave voltammetric (SWV) response of SWCNT/EPPGE and AuNP-SWCNT/EPPGE towards the oxidation of 8-OH-Gua in respect of several essential analytical parameters viz. sensitivity, detection limit, peak current and peak potential. The AuNP-SWCNT/EPPGE exhibited a well defined anodic peak at potential of ~221 mV for the oxidation of 8-OH-Gua as compared to ~312 mV using SWCNT/EPPGE at pH=7.2. Under optimized conditions linear calibration curve for 8-OH-Gua is obtained over a concentration range of 0.01-10.0 nM in phosphate buffer solution (PBS) of pH=7.2 with detection limit and sensitivity of 5.0 (±0.1) pM and 4.9 (±0.1) μA nM(-1), respectively. The oxidation of 8-OH-Gua occurred in a pH dependent process and the electrode reaction followed adsorption controlled pathway. The electrode exhibited an efficient catalytic response with good reproducibility and stability. The method has been found selective and successfully implemented for the determination of 8-OH-Gua in urine samples of diabetic patients.

  7. Clean Transformation of Ethanol to Useful Chemicals. The Behavior of a Gold-Modified Silicalite Catalyst.

    PubMed

    Falletta, Ermelinda; Rossi, Michele; Teles, Joaquim Henrique; Della Pina, Cristina

    2016-01-01

    Upon addition of gold to silicalite-1 pellets (a MFI-type zeolite), the vapor phase oxidation of ethanol could be addressed to acetaldehyde or acetic acid formation. By optimizing the catalyst composition and reaction conditions, the conversion of ethanol could be tuned to acetaldehyde with 97% selectivity at 71% conversion or to acetic acid with 78% selectivity at total conversion. Considering that unloaded silicalite-1 was found to catalyze the dehydration of ethanol to diethylether or ethene, a green approach for the integrated production of four important chemicals is herein presented. This is based on renewable ethanol as a reagent and a modular catalytic process. PMID:27007358

  8. Optimization of oleylamine-Fe3O4/MWCNTs nanocomposite modified GC electrode for electrochemical determination of ofloxacin.

    PubMed

    Kumar, Deivasigamani Ranjith; Manoj, Devaraj; Santhanalakshmi, Jayadevan

    2014-07-01

    Iron oxide (Fe3O4) nanoparticles are prepared by nucleation method using oleylamine (OLA) as the capping agent. The OLA capped Fe3O4 nanoparticles (OLA-Fe3O4) are characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD) and High Resolution Transmission Electron Microscopic (HRTEM) analysis. The morphology of the OLA-Fe3O4 nanoparticles is found to be spherical with an average size of 7.5 +/- 0.5 nm. OLA-Fe3O4 nanoparticles are incorporated into the carboxyl functionalized Multi-walled carbon nanotubes (MWCNTs) at different 10, 20, 30, 40 and 50 wt% by ultrasonication. The optimum loading of OLA-Fe3O4 nanoparticles on the MWCNTs was characterized by FTIR, Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and Linear Sweep Voltammetry (LSV). Finally, the 40wt% of OLA-Fe3O4 nanoparticles on MWCNTs was chosen as the optimum loading and this composition was used for the electrochemical oxidation of ofloxacin (OFX). For determination of OFX in OLA-Fe3O4/MWCNTs modified glassy carbon (GC) electrode show high sensitivity and fast response. The sensitivity of the modified electrode was calculated to be 0.578 microAmicroM(-1) with a detection limit of 0.060 microM. The high sensitivity, wider linear range, good reproducibility and the minimal surface fouling make this OLA-Fe3O4/MWCNTs/GC modified electrode acts as a promising platform for electrochemical determination of OFX.

  9. Solid-phase extraction based on ground methacrylate monolith modified with gold nanoparticles for isolation of proteins.

    PubMed

    Vergara-Barberán, María; Lerma-García, María Jesús; Simó-Alfonso, Ernesto Francisco; Herrero-Martínez, José Manuel

    2016-04-21

    In this study, a novel polymeric material functionalized with gold nanoparticles (AuNPs) was prepared as solid-phase extraction (SPE) sorbent for isolation of proteins. The sorbent was synthesized from a powdered poly(glycidyl-co-ethylene dimethacrylate) monolith, and modified with ammonia, followed by immobilization of AuNPs on the pore surface of the material. To evaluate the performance of this SPE support, proteins were selected as test solutes, being the extraction conditions and other parameters (loading capacity and regenerative ability of sorbent) established. The results indicated that this sorbent could be employed to selectively capture proteins according to their pI, on the basis of the strong affinity of these biomacromolecules towards to AuNPs surface. The applicability of this sorbent was demonstrated by isolating protein species of interest (bovine serum albumin, cytochrome c and lectins in European mistletoe leaves), followed by SDS-PAGE analysis. PMID:27026598

  10. Development of atom transfer radical polymer-modified gold nanoparticle-based enzyme-linked immunosorbent assay (ELISA).

    PubMed

    Chen, Feng; Hou, Shike; Li, Qingsheng; Fan, Haojun; Fan, Rong; Xu, Zhongwei; Zhala, Gahu; Mai, Xia; Chen, Xiaoyi; Chen, Xuyi; Liu, Yingfu

    2014-10-21

    In this work, a novel enzyme-linked immunosorbent assay (ELISA) with a low limit of detection and high sensitivity was developed using atom transfer radical polymer (ATRP)-modified gold nanoparticles (AuNPs). Clear signal amplification was achieved by introducing an abundance of horseradish peroxidase (HRP) to the AuNPs, because of the ATRP modification. This result suggested that the new ELISA was able to detect antigens in complex mixtures, and the limit of detection (LOD) was lower than that of conventional ELISA by a factor of 81. The new ELISA strategy greatly decreased the LOD during analysis and exhibited excellent reproducibility, stability, and feasibility. Therefore, it is a promising technique with many potential applications in biochemistry and medical science research.

  11. Solid-phase extraction based on ground methacrylate monolith modified with gold nanoparticles for isolation of proteins.

    PubMed

    Vergara-Barberán, María; Lerma-García, María Jesús; Simó-Alfonso, Ernesto Francisco; Herrero-Martínez, José Manuel

    2016-04-21

    In this study, a novel polymeric material functionalized with gold nanoparticles (AuNPs) was prepared as solid-phase extraction (SPE) sorbent for isolation of proteins. The sorbent was synthesized from a powdered poly(glycidyl-co-ethylene dimethacrylate) monolith, and modified with ammonia, followed by immobilization of AuNPs on the pore surface of the material. To evaluate the performance of this SPE support, proteins were selected as test solutes, being the extraction conditions and other parameters (loading capacity and regenerative ability of sorbent) established. The results indicated that this sorbent could be employed to selectively capture proteins according to their pI, on the basis of the strong affinity of these biomacromolecules towards to AuNPs surface. The applicability of this sorbent was demonstrated by isolating protein species of interest (bovine serum albumin, cytochrome c and lectins in European mistletoe leaves), followed by SDS-PAGE analysis.

  12. Functionalized gold nanoparticle-polypyrrole nanobiocomposite with high effective surface area for electrochemical/pH dual stimuli-responsive smart release of insulin.

    PubMed

    Shamaeli, Ehsan; Alizadeh, Naader

    2015-02-01

    A novel functionalized gold nanoparticle-polypyrrole-nanobiocomposite (PPy-FGNP-NBC) with large effective surface area was fabricated for electrical/pH dual stimuli-responsive local delivery of insulin. The fabrication method involves simple electrodeposition and immobilization processes without use of organic solvents. Release studies based on the nature of insulin-surface binding indicated that release was promoted for PPy-FGNP-NBC. Kinetics analysis showed that release of insulin strongly affected by applying external potential stimuli. Also, the insulin release was under influence of pH and was slowed down under lower pH. This pH-sensitivity was remarkably increased by applying potential. Based on in vitro release study under applied potential condition, insulin release in the artificial gastric juice is significantly slower than that in the artificial intestinal fluid. Circular dichroism analysis showed that insulin retained its original conformation during electrochemically stimulated release.

  13. Synthesis and Characterization of Curcumin-Functionalized HP-β-CD-Modified GoldMag Nanoparticles as Drug Delivery Agents.

    PubMed

    Lian, Ting; Peng, Mingli; Vermorken, Alphons J M; Jin, Yanyan; Luo, Zhiyi; Van de Ven, Wim J M; Wan, Yinsheng; Hou, Peng; Cui, Yali

    2016-06-01

    Curcumin, a polyphenol extracted from turmeric (Curcuma longa), has emerged as a potent multimodal cancer-preventing agent. It may attenuate the spread of cancer and render chemotherapy more effective. However, curcumin is neither well absorbed nor well retained in the blood, resulting in low efficacy. In an attempt to enhance the potency and to improve the bioavailability of curcumin, new delivery agents, hydroxypropyl-beta-cyclodextrin (HP-β-CD)-modified GoldMag nanoparticles (CD-GMNs) were designed and synthesized to incorporate curcumin. The CD-GMNs were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermo-gravimetric Analysis (TGA), X-ray Diffraction (XRD), Dynamic Light Scattering measurements (DLS), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM) analyses. For the magnetic carrier of CD-GMNs, the content of HP-β-CD was 26.9 wt%. CD-GMNs have a saturation magnetization of 22.7 emu/g with an average hydrodynamic diameter of 80 nm. The curcumin loading, encapsulation efficiency and releasing properties in vitro were also investigated. The results showed that the drug encapsulation ratio was 88% and the maximum curcumin loading capacity of CD-GMNs was 660 μg/5 mg. In vitro drug release studies showed a controlled and pH-sensitive curcumin release over a period of one week. Collectively, our data suggest that HP-β-CD-modified GoldMag nanoparticles can be considered to form a promising delivery system for curcumin to tumor sites. Targeting can be achieved by the combined effects of the application of an external magnetic field and the effect on drug release of lower pH values often found in the tumor microenvironment.

  14. Synthesis and Characterization of Curcumin-Functionalized HP-β-CD-Modified GoldMag Nanoparticles as Drug Delivery Agents.

    PubMed

    Lian, Ting; Peng, Mingli; Vermorken, Alphons J M; Jin, Yanyan; Luo, Zhiyi; Van de Ven, Wim J M; Wan, Yinsheng; Hou, Peng; Cui, Yali

    2016-06-01

    Curcumin, a polyphenol extracted from turmeric (Curcuma longa), has emerged as a potent multimodal cancer-preventing agent. It may attenuate the spread of cancer and render chemotherapy more effective. However, curcumin is neither well absorbed nor well retained in the blood, resulting in low efficacy. In an attempt to enhance the potency and to improve the bioavailability of curcumin, new delivery agents, hydroxypropyl-beta-cyclodextrin (HP-β-CD)-modified GoldMag nanoparticles (CD-GMNs) were designed and synthesized to incorporate curcumin. The CD-GMNs were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermo-gravimetric Analysis (TGA), X-ray Diffraction (XRD), Dynamic Light Scattering measurements (DLS), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM) analyses. For the magnetic carrier of CD-GMNs, the content of HP-β-CD was 26.9 wt%. CD-GMNs have a saturation magnetization of 22.7 emu/g with an average hydrodynamic diameter of 80 nm. The curcumin loading, encapsulation efficiency and releasing properties in vitro were also investigated. The results showed that the drug encapsulation ratio was 88% and the maximum curcumin loading capacity of CD-GMNs was 660 μg/5 mg. In vitro drug release studies showed a controlled and pH-sensitive curcumin release over a period of one week. Collectively, our data suggest that HP-β-CD-modified GoldMag nanoparticles can be considered to form a promising delivery system for curcumin to tumor sites. Targeting can be achieved by the combined effects of the application of an external magnetic field and the effect on drug release of lower pH values often found in the tumor microenvironment. PMID:27427699

  15. Electrodeposition of gold nanoclusters on overoxidized polypyrrole film modified glassy carbon electrode and its application for the simultaneous determination of epinephrine and uric acid under coexistence of ascorbic acid.

    PubMed

    Li, Jing; Lin, Xiang-Qin

    2007-07-23

    A novel biosensor was fabricated by electrochemical deposition of gold nanoclusters on ultrathin overoxidized polypyrrole (PPyox) film, formed a nano-Au/PPyox composite on glassy carbon electrode (nano-Au/PPyox/GCE). The properties of the nanocomposite have been characterized by field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and electrochemical investigations. The nano-Au/PPyox/GCE had strongly catalytic activity toward the oxidation of epinephrine (EP), uric acid (UA) and ascorbic acid (AA), and resolved the overlapping voltammetric response of EP, UA and AA into three well-defined peaks with a large anodic peak difference. The catalytic peak currents obtained from differential pulse voltammetry increased linearly with increasing EP and UA concentrations in the range of 3.0x10(-7) to 2.1x10(-5) M and 5.0x10(-8) to 2.8x10(-5) M with a detection limit of 3.0x10(-8) and 1.2x10(-8) M (s/n=3), respectively. The results showed that the modified electrode can selectively determine EP and UA in the coexistence of a large amount of AA. In addition, the sensor exhibited excellent sensitivity, selectivity and stability. The nano-Au/PPyox/GCE has been applied to determination of EP in epinephrine hydrochloride injection and UA in urine samples with satisfactory results.

  16. Growth of gold-manganese oxide nanostructures on a 3D origami device for glucose-oxidase label based electrochemical immunosensor.

    PubMed

    Li, Long; Xu, Jinmeng; Zheng, Xiaoxiao; Ma, Chao; Song, Xianrang; Ge, Shenguang; Yu, Jinghua; Yan, Mei

    2014-11-15

    Flexible biosensors are of considerable current interest for the development of portable point-of-care medical products, minimally invasive implantable devices, and compact diagnostic platforms. Here, we reported an electrochemical paper based analytical device fabricated (EPADs) by sequentially growing gold nanoparticles (AuNPs) and manganese oxide (MnO2) nanowires networks on a freestanding three dimensional (3D) origami device. This fabricated through the growth of an AuNPs layer on the surfaces of cellulose fibers in the screen-printed paper working electrode (PWE), and thus developed a gold paper working electrode (Au-PWE). Subsequently, MnO2 nanowires were successfully electrodeposited on Au-PWE to form a 3D network with large surface areas. Based on this novel EPADs and the principle of origami, we presented herein a simple immunosensing scheme using glucose oxidase (GOx) as an enzyme label, 3,3',5,5'-tetramethylbenzidine (TMB) as a redox terminator, and glucose as an enzyme substrate. The electrochemical enzymatic redox cycling was applied to the detection of prostate protein antigen (PSA), a biomarker of prostatic cancer. The proposed method successfully fulfilled the highly sensitive detection of PSA with a linear range of 0.005 ng mL(-1)-100 ng mL(-1) with a detection limit of 0.0012 ng mL(-1). This EPADs exhibited high sensitivity, specificity and excellent performance in real human serum assay, and could be applied in point-of-care testing of other tumor markers for remote regions and developing countries.

  17. Functionalized gold nanorod-based labels for amplified electrochemical immunoassay of E. coli as indicator bacteria relevant to the quality of dairy product.

    PubMed

    Zhang, Xinai; Zhang, Fan; Zhang, Hongyin; Shen, Jianzhong; Han, En; Dong, Xiaoya

    2015-01-01

    In this paper, we report an amplified electrochemical immunoassay for Escherichia coli as indicator bacteria relevant to the quality of dairy product using the functionalized gold nanorod-based labels ({dAb-AuNR-FCA}). The {dAb-AuNR-FCA} labels were designed by exploiting silica-functionalized gold nanorods (AuNR@SiO2) as the carriers for immobilization of detection antibody (dAb) and ferrocenecarboxylic acid (FCA), in which dAb was used for recognition of E. coli and FCA tags served as signal-generating molecule. Greatly amplified signal was achieved in the sandwich-type immunoassay when enormous FCA linked to AuNR@SiO2. Compared with the commercially available {dAb-FCA}, the {dAb-AuNR-FCA} labels exhibited a better performance for E. coli assay due to the advantages of AuNR@SiO2 as carriers. Under optimal experimental conditions, it showed a linear relationship between the peak current of FCA and the logarithmic value of E. coli concentration ranging from 1.0×10(2) to 5.0×10(4) cfu mL(-1) with a detection limit of 60 cfu mL(-1) (S/N=3), and the electrochemical detection of E. coli could be achieved in 3h. Moreover, the proposed strategy was used to determine E. coli in dairy product (pure fresh milk, yogurt in shelf-life, and expired yogurt), and the recoveries of standard additions were in the range of 95.1-106%. This proposed strategy exhibited rapid response, high sensitivity and specificity for E. coli assay in dairy product, and could become a promising technique to estimate the quality of dairy product.

  18. Electrochemical Determination of Bisphenol A with Pencil Graphite Electrodes Modified with Co(II), Ni(II), Cu(II) and Fe(II) Phthalocyaninetetrasulfonates.

    PubMed

    Özcan, Levent; Altuntas, Muhammet; Büyüksagis, Aysel; Türk, Hayrettin; Yurdakal, Sedat

    2016-01-01

    Pencil graphite electrodes modified with Co(II), Ni(II), Cu(II) and Fe(II) metallophthalocyaninetetrasulfonates (MePcTSs) were investigated for an electrochemical determination of bisphenol A (BPA). The electrochemical performances of the modified electrodes for different pH values in phosphate and the Britton-Robinson buffers were determined by cyclic voltammetry; the electrode performances were better in the Britton-Robinson buffer. NiPcTS and CoPcTS modifications of the electrodes had remarkable enhancements on their performances. The differential pulse voltammetry parameters for the electrodes were optimized, and we found that the electrochemical response versus the concentration of BPA is linear from 5.0 × 10(-7) to 1.0 × 10(-5) M for the NiPcTS and CoPcTS modified electrodes. The detection limits of these modified electrodes are 2.9 × 10(-7) and 4.3 × 10(-7) M, respectively, and the effects of interfering species are less than 5%. The results show that NiPcTS and CoPcTS modified pencil graphite electrodes could be used for electrochemical determinations of BPA for analytical purposes. PMID:27506715

  19. Electrochemical properties of modified highly ordered pyrolytic graphite by using ambient plasma

    NASA Astrophysics Data System (ADS)

    Kim, Ho Jun; Yang, Cheol-Soo; Jeong, HaeKyung

    2016-01-01

    Surface of highly ordered pyrolytic graphite (HOPG) is reformed by using ambient plasma. The HOPG film shows various pore structures after the plasma treatment, indicating improved electrochemical properties for supercapacitor applications because of the increase of the surface area. We also compare water effect on the film during the plasma treatment. Water might protect HOPG surface from the plasma and provide oxygen functional groups onto it, resulting in lower infected pores and higher impedance compared with them of HOPG film without water. Ambient plasma, therefore, could be considered as an economic and effective method for sample reformations.

  20. Branched zinc oxide nanorods arrays modified paper electrode for electrochemical immunosensing by combining biocatalytic precipitation reaction and competitive immunoassay mode.

    PubMed

    Sun, Guoqiang; Yang, Hongmei; Zhang, Yan; Yu, Jinghua; Ge, Shenguang; Yan, Mei; Song, Xianrang

    2015-12-15

    Branched zinc oxide nanorods (BZR) arrays, an array with high charge carries collection efficiency and specific surface area, are grown on the reduced graphene oxide-paper working electrode for the first time to construct a paper-based electrochemical (EC) immunosensor. Typically, the BZR are fabricated via a simple hydrothermal process, which can provide abundant sites for antibodies loading. By combining the large surface area of porous zinc oxide (PZS) and good biocompatibility of gold nanoparticles (AuNPs), PZS-AuNPs (PZS@Au) nanocomposites are designed to label horseradish peroxide (HRP) and antigens. After a competitive reaction between antigens and PZS@Au nanocomposites labeled antigens, the signal labels are introduced into the immunosensor, in which, HRP participate in biocatalytic precipitation process. The produced precipitate reduces the electrode surface area and hinders the electron transfer. With the increase of concentration of antigens, the signal labels introduced into the sensor decrease, thus, a signal-on immunoassay for α-fetoprotein detection is constructed. The proposed paper-based EC immunosensor combines enzymatic biocatalytic precipitation reaction and competitive immunoassay mode for the first time, and possesses a wide linear range from 0.2 pg mL(-1) to 500 ng mL(-1) with a detection limit of 0.08 pg mL(-1). In addition, the proposed method is simple, sensitive and specific and can be a promising platform for other protein detection.

  1. Electrochemical sensor for multiplex screening of genetically modified DNA: identification of biotech crops by logic-based biomolecular analysis.

    PubMed

    Liao, Wei-Ching; Chuang, Min-Chieh; Ho, Ja-An Annie

    2013-12-15

    Genetically modified (GM) technique, one of the modern biomolecular engineering technologies, has been deemed as profitable strategy to fight against global starvation. Yet rapid and reliable analytical method is deficient to evaluate the quality and potential risk of such resulting GM products. We herein present a biomolecular analytical system constructed with distinct biochemical activities to expedite the computational detection of genetically modified organisms (GMOs). The computational mechanism provides an alternative to the complex procedures commonly involved in the screening of GMOs. Given that the bioanalytical system is capable of processing promoter, coding and species genes, affirmative interpretations succeed to identify specified GM event in terms of both electrochemical and optical fashions. The biomolecular computational assay exhibits detection capability of genetically modified DNA below sub-nanomolar level and is found interference-free by abundant coexistence of non-GM DNA. This bioanalytical system, furthermore, sophisticates in array fashion operating multiplex screening against variable GM events. Such a biomolecular computational assay and biosensor holds great promise for rapid, cost-effective, and high-fidelity screening of GMO. PMID:23893064

  2. A reagentless non-enzymatic hydrogen peroxide sensor presented using electrochemically reduced graphene oxide modified glassy carbon electrode.

    PubMed

    Mutyala, Sankararao; Mathiyarasu, Jayaraman

    2016-12-01

    Herein, we report a simple, facile and reproducible non-enzymatic hydrogen peroxide (H2O2) sensor using electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). The modified electrode was characterized by Fourier transform infrared (FT-IR), UV-Visible, scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Cyclic voltammetric (CV) analysis revealed that ERGO/GCE exhibited virtuous charge transfer properties for a standard redox systems and showed excellent performance towards electroreduction of H2O2. Amperometric study using ERGO/GCE showed high sensitivity (0.3μA/μM) and faster response upon the addition of H2O2 at an applied potential of -0.25V vs. Ag/AgCl. The detection limit is assessed to be 0.7μM (S/N=3) and the time to reach a stable study state current is <3s for a linear range of H2O2 concentration (1-16μM). In addition, the modified electrode exhibited good reproducibility and long-term stability. PMID:27612728

  3. Electrochemical sensor for multiplex screening of genetically modified DNA: identification of biotech crops by logic-based biomolecular analysis.

    PubMed

    Liao, Wei-Ching; Chuang, Min-Chieh; Ho, Ja-An Annie

    2013-12-15

    Genetically modified (GM) technique, one of the modern biomolecular engineering technologies, has been deemed as profitable strategy to fight against global starvation. Yet rapid and reliable analytical method is deficient to evaluate the quality and potential risk of such resulting GM products. We herein present a biomolecular analytical system constructed with distinct biochemical activities to expedite the computational detection of genetically modified organisms (GMOs). The computational mechanism provides an alternative to the complex procedures commonly involved in the screening of GMOs. Given that the bioanalytical system is capable of processing promoter, coding and species genes, affirmative interpretations succeed to identify specified GM event in terms of both electrochemical and optical fashions. The biomolecular computational assay exhibits detection capability of genetically modified DNA below sub-nanomolar level and is found interference-free by abundant coexistence of non-GM DNA. This bioanalytical system, furthermore, sophisticates in array fashion operating multiplex screening against variable GM events. Such a biomolecular computational assay and biosensor holds great promise for rapid, cost-effective, and high-fidelity screening of GMO.

  4. Electrochemically modified carbon and chromium surfaces for AFM imaging of double-strand DNA interaction with transposase protein.

    PubMed

    Esnault, Charles; Chénais, Benoît; Casse, Nathalie; Delorme, Nicolas; Louarn, Guy; Pilard, Jean-François

    2013-02-01

    Carbon and chromium surfaces were modified by electrochemical reduction of a diazonium salt formed in situ from the sulfanilic acid. The organic layer formed was activated by phosphorus pentachloride (PCl(5)) to form a benzene sulfonil chloride (Ar-SO(2)Cl). An electrochemical study of the blocking effect and the activity of this surface was carried out on a carbon electrode. The chromium surface study was completed by X-ray photoelectron spectroscopy and atomic force microscopy to characterize the formation of a compact monolayer (0.8 nm height and roughness 0.2-0.3 nm). The compactness and the activity of this organic monolayer allowed us to affix a length dsDNA with the aim of analyzing the formation of a complex between dsDNA and a protein. The interaction of a transposase protein with its target dsDNA was investigated. The direct imaging of the nucleoproteic complex considered herein gives new insights in the comprehension of transposase-DNA interaction in agreement with biochemical data.

  5. Selectable Ultrasensitive Detection of Hg2+ with Rhodamine 6G-Modified Nanoporous Gold Optical Sensor

    PubMed Central

    Wang, Zheng; Yang, Min; Chen, Chao; Zhang, Ling; Zeng, Heping

    2016-01-01

    An extremely sensitive fluorescence sensor has been developed for selectively detection of mercury ions based on metallophilic Hg2+-Au+ interactions, which results in an effective release of pre-adsorbed rhodamine 6G (R6G) molecules from the nanoporous gold substrate, associated with a significant decrease of fluorescence intensity. The optical sensor has a detection sensitivity down to 0.6 pM for Hg2+ and CH3Hg+ ions, in particular a superior selectivity in a complex aqueous system containing 13 different types of metal ions, meanwhile maintaining a long-term stability after 10 cycles. Such a fluorescence sensor combining multiple advantages therefore present promising potentials in various applications. PMID:27403721

  6. Selectable Ultrasensitive Detection of Hg2+ with Rhodamine 6G-Modified Nanoporous Gold Optical Sensor

    NASA Astrophysics Data System (ADS)

    Wang, Zheng; Yang, Min; Chen, Chao; Zhang, Ling; Zeng, Heping

    2016-07-01

    An extremely sensitive fluorescence sensor has been developed for selectively detection of mercury ions based on metallophilic Hg2+-Au+ interactions, which results in an effective release of pre-adsorbed rhodamine 6G (R6G) molecules from the nanoporous gold substrate, associated with a significant decrease of fluorescence intensity. The optical sensor has a detection sensitivity down to 0.6 pM for Hg2+ and CH3Hg+ ions, in particular a superior selectivity in a complex aqueous system containing 13 different types of metal ions, meanwhile maintaining a long-term stability after 10 cycles. Such a fluorescence sensor combining multiple advantages therefore present promising potentials in various applications.

  7. Selectable Ultrasensitive Detection of Hg(2+) with Rhodamine 6G-Modified Nanoporous Gold Optical Sensor.

    PubMed

    Wang, Zheng; Yang, Min; Chen, Chao; Zhang, Ling; Zeng, Heping

    2016-01-01

    An extremely sensitive fluorescence sensor has been developed for selectively detection of mercury ions based on metallophilic Hg(2+)-Au(+) interactions, which results in an effective release of pre-adsorbed rhodamine 6G (R6G) molecules from the nanoporous gold substrate, associated with a significant decrease of fluorescence intensity. The optical sensor has a detection sensitivity down to 0.6 pM for Hg(2+) and CH3Hg(+) ions, in particular a superior selectivity in a complex aqueous system containing 13 different types of metal ions, meanwhile maintaining a long-term stability after 10 cycles. Such a fluorescence sensor combining multiple advantages therefore present promising potentials in various applications. PMID:27403721

  8. Enzymatic Polymerization on DNA Modified Gold Nanowire for Label-Free Detection of Pathogen DNA

    PubMed Central

    Jeong, Jaepil; Kim, Hyejin; Lee, Jong Bum

    2015-01-01

    This paper presents a label-free biosensor for the detection of single-stranded pathogen DNA through the target-enhanced gelation between gold nanowires (AuNW) and the primer DNAs branched on AuNW. The target DNA enables circularization of the linear DNA template, and the primer DNA is elongated continuously via rolling circle amplification. As a result, in the presence of the target DNA, a macroscopic hydrogel was fabricated by the entanglement of the elongated DNA with AuNWs as a scaffold fiber for effective gelation. In contrast, very small separate particles were generated in the absence of the target DNA. This label-free biosensor might be a promising tool for the detection of pathogen DNAs without any devices for further analysis. Moreover, the biosensor based on the weaving of AuNW and DNAs suggests a novel direction for the applications of AuNWs in biological engineering. PMID:26084045

  9. Electrochemical immunosensor with NiAl-layered double hydroxide/graphene nanocomposites and hollow gold nanospheres double-assisted signal amplification.

    PubMed

    Qiao, Lu; Guo, Yemin; Sun, Xia; Jiao, Yancui; Wang, Xiangyou

    2015-08-01

    A sensitive electrochemical immunosensor based on NiAl-layered double hydroxide/graphene nanocomposites (NiAl-LDH/G) and hollow gold nanospheres (HGNs) was proposed for chlorpyrifos detection. The NiAl-LDH/G was prepared using a conventional coprecipitation process and reduction of the supporting graphene oxide. Subsequently, the nanocomposites were dispersed with chitosan (CS). The NiAl-LDH/G possessed good electrochemical behavior and high binding affinity to the electrode. The high surface areas of HGNs and the vast aminos and hydroxyls of CS provided a platform for the covalently crosslinking of antibody. Under optimal conditions, the immunosensor exhibited a wide linear range from 5 to 150 μg/mL and from 150 to 2 μg/mL, with a detection limit of 0.052 ng/mL. The detection results showed good agreement with standard gas chromatography method. The constructed immunosensor exhibited good reproducibility, high specificity, acceptable stability and regeneration performance, which provided a new promising tool for chlorpyrifos detection in real samples.

  10. An ultrasensitive sandwich-type electrochemical immunosensor based on signal amplification strategy of gold nanoparticles functionalized magnetic multi-walled carbon nanotubes loaded with lead ions.

    PubMed

    Li, Faying; Han, Jian; Jiang, Liping; Wang, Yulan; Li, Yueyun; Dong, Yunhui; Wei, Qin

    2015-06-15

    In this study, a novel and ultrasensitive sandwich-type electrochemical immunosensor was prepared for the quantitative detection of alpha fetoprotein (AFP), a well-known hepatocellular carcinoma biomarker. Gold nanoparticles (Au NPs) functionalized magnetic multi-walled carbon nanotubes (MWCNTs-Fe3O4) were prepared and utilized for the adsorption of lead ions (Pb(2+)) and the secondary antibodies (Ab2). The resultant nanocomposites (Pb(2+)@Au@MWCNTs-Fe3O4) were used as the label for signal amplification, showing better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) than MWCNTs, MWCNTs-Fe3O4 or Au@MWCNTs-Fe3O4 due to the synergetic effect presented in Pb(2+)@Au@MWCNTs-Fe3O4. Moreover, Au NPs were electrodeposited on the surface of glassy carbon electrode (GCE) for the effective immobilization of primary antibodies (Ab1). Under the optimal conditions, a linear range from 10 fg/mL to 100 ng/mL and a detection limit of 3.33 fg/mL were obtained. The proposed electrochemical sandwich-type immunosensor shows high sensitivity, good selectivity and stability for the quantitative detection of AFP, holding a great potential in clinical and diagnostic applications.

  11. Facile fabrication of magnetic gold electrode for magnetic beads-based electrochemical immunoassay: application to the diagnosis of Japanese encephalitis virus.

    PubMed

    Li, Fang; Mei, Li; Li, Yaoming; Zhao, Kaihong; Chen, Huanchun; Wu, Peng; Hu, Yonggang; Cao, Shengbo

    2011-06-15

    A novel magnetic beads-based electrochemical immunoassay strategy has been developed for the detection of Japanese encephalitis virus (JEV). The magnetic gold electrode was fabricated to manipulate magnetic beads for the direct sensing applications. Gold-coated magnetic beads were employed as the platforms for the immobilization and immunoreaction process, and horseradish peroxidase was chosen as an enzymatic tracer. The proteins (e.g., antibodies or immunocomplexes) attached on the surface of magnetic beads were found to induce a significant decline in their electric conductivity. Multiwalled carbon nanotubes were introduced to improve sensitivity of the assay. The envelope (E) protein, a major immunogenic protein of JEV, was utilized to optimize the assay parameters. Under the optimal conditions, the linear response range of E protein was 0.84 to 11,200 ng/mL with a detection limit of 0.56 ng/mL. When applied for detection of JEV, the proposed method generated a linear response range between 2×10(3) and 5×10(5) PFU/mL. The detection limit for JEV was 2.0×10(3) PFU/mL, which was 2 orders of magnitude lower than that of immunochromatographic strip and similar to that obtained from RT-PCR. This method was also successfully applied to detect JEV in clinical specimens.

  12. Electrochemical in-situ dissolution study of structurally ordered, disordered and gold doped PtCu3 nanoparticles on carbon composites

    NASA Astrophysics Data System (ADS)

    Jovanovič, Primož; Šelih, Vid Simon; Šala, Martin; Hočevar, Samo B.; Pavlišič, Andraž; Gatalo, Matija; Bele, Marjan; Ruiz-Zepeda, Francisco; Čekada, Miha; Hodnik, Nejc; Gaberšček, Miran

    2016-09-01

    Commercial deployment of low-temperature-fuel cells is still hugely restricted by platinum alloy catalysts corrosion. Extensive research of the last years is focused on increasing stability of the catalyst composite, however a comprehensive understanding is still lacking. In pursuing this fundamentally and practically very important objective we present a comparative corrosion study of a PtCu3 nano-alloy system by investigating the effects of structural ordering and gold doping. For that purpose a recently developed electrochemical flow cell (EFC) coupled to inductively coupled plasma mass spectrometer (ICP-MS) is employed. This approach provides potential- and time-resolved insight into dissolution process at extremely low concentrations (ppb level). Our results show a structure-dependent copper corrosion, where ordering and gold-doping significantly improve copper retention in the native alloy. Two assumptions can be drawn from the measured Pt dissolution profiles: (i) a better Pt re-deposition efficiency in catalysts with higher porosity and (ii) the beneficial effect of Au surface doping that lowers the amount of dissolved Pt amount and shifts the Pt cathodic dissolution to lower potentials. A 2.6 nm Pt/C standard catalyst with the same carbon loading shows a much lower stability which is due to the well-known particle size effect.

  13. Ultrasensitive electrochemical detection of nucleic acid by coupling an autonomous cascade target replication and enzyme/gold nanoparticle-based post-amplification.

    PubMed

    Liu, Shufeng; Wei, Wenji; Wang, Yanqun; Fang, Li; Wang, Li; Li, Feng

    2016-06-15

    Owing to the intrinsic importance of nucleic acid as bio-targets, the development of isothermal and ultrasensitive electrochemical DNA biosensor is very essential for biological studies and medical diagnostics. Herein, the autonomous cascade DNA replication strategy was effectively married with the enzyme/gold nanoparticle-based post-amplification strategy to promote the detection performance toward target DNA. A hairpin DNA probe (HP) is designed that consists of an overhang at 3'-end as the recognition unit for target DNA, a recognition site for nicking endonuclease, and an alkane spacer to terminate polymerization reaction. The autonomous DNA replication-scission-displacement reaction operated by the nicking endonuclease/KF polymerase induced the autocatalytic opening of HP, which was then specifically bound by the enzyme/gold nanoparticles for further dual-signal amplification toward target-related sensing events. A low detection limit of 0.065 fM with an excellent selectivity toward target DNA could be achieved. The proposed biosensor could be also easily regenerated for target detection. The developed biosensor creates an opportunity for the effective coupling of the target replication with post-amplification strategies and thus opens a promising avenue for the detection of nucleic acid with low abundance in bioanalysis and clinical biomedicine.

  14. Reflectometric measurement of n-hexane adsorption on ZnO2 nanohybrid film modified by hydrophobic gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Sebők, Dániel; Csapó, Edit; Ábrahám, Nóra; Dékány, Imre

    2015-04-01

    Zinc-peroxide/poly(styrenesulfonate) nanohybrid thin films (containing 20 bilayers: [ZnO2/PSS]20, d ∼ 500 nm) were prepared using layer-by-layer (LbL) method. The thin film surface was functionalized by different surface modifying agents (silanes, alkylthiols and hydrophobized nanoparticles). Based on the experimental results of quartz crystal microbalance (QCM) and contact angle measurements (as prequalifications) the octanethiol covered gold nanoparticles (OT-AuNPs) were selected for further vapour adsorption studies. Reflectometric interference spectroscopy (RIfS) was used to measure n-hexane vapour adsorption on the original and modified nanohybrid films in a gas flow platform. The thin film provides only the principle of the measurement (by interference phenomenon), the selectivity and hydrophobicity is controlled and enhanced by surface functionalization (by dispersion interaction between the alkyl chains). The interference pattern shift (Δλ) caused by the increase of the optical thickness of the thin film due to vapour adsorption was investigated. It was found that due to the surface functionalization by hydrophobic nanoparticles the effect of water vapour adsorption decreased significantly, while for n-hexane opposite tendency was observed (the effective refractive index and thus the interference pattern shift increased drastically). The correlation between QCM technique and optical method (RIfS) was specified: linear specific adsorbed amount vs. wavelength shift calibration curves were determined in the pr = 0-0.4 relative vapour pressure range. The thin film is suitable for sensorial application (e.g. volatile organic compound/VOC sensor).

  15. Generic phosphatase activity detection using zinc mediated aggregation modulation of polypeptide-modified gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Selegård, Robert; Enander, Karin; Aili, Daniel

    2014-11-01

    A challenge in the design of plasmonic nanoparticle-based colorimetric assays is that the change in colloidal stability, which generates the colorimetric response, is often directly linked to the biomolecular recognition event. New assay strategies are hence required for every type of substrate and enzyme of interest. Here, a generic strategy for monitoring of phosphatase activity is presented where substrate recognition is completely decoupled from the nanoparticle stability modulation mechanism, which enables detection of a wide range of enzymes using different natural substrates with a single simple detection scheme. Phosphatase activity generates inorganic phosphate that forms an insoluble complex with Zn2+. In a sample containing a preset concentration of Zn2+, phosphatase activity will markedly reduce the concentration of dissolved Zn2+ from the original value, which in turn affects the aggregation of gold nanoparticles functionalized with a designed Zn2+ responsive polypeptide. The change in nanoparticle stability thus provides a rapid and sensitive readout of the phosphatase activity. The assay is not limited to a particular enzyme or enzyme substrate, which is demonstrated using three completely different phosphatases and five different substrates, and thus constitutes a highly interesting system for drug screening and diagnostics.A challenge in the design of plasmonic nanoparticle-based colorimetric assays is that the change in colloidal stability, which generates the colorimetric response, is often directly linked to the biomolecular recognition event. New assay strategies are hence required for every type of substrate and enzyme of interest. Here, a generic strategy for monitoring of phosphatase activity is presented where substrate recognition is completely decoupled from the nanoparticle stability modulation mechanism, which enables detection of a wide range of enzymes using different natural substrates with a single simple detection scheme

  16. Electrochemically assisted deposition of strontium modified magnesium phosphate on titanium surfaces.

    PubMed

    Meininger, M; Wolf-Brandstetter, C; Zerweck, J; Wenninger, F; Gbureck, U; Groll, J; Moseke, C

    2016-10-01

    Electrochemically assisted deposition was utilized to produce ceramic coatings on the basis of magnesium ammonium phosphate (struvite) on corundum-blasted titanium surfaces. By the addition of defined concentrations of strontium nitrate to the coating electrolyte Sr(2+) ions were successfully incorporated into the struvite matrix. By variation of deposition parameters it was possible to fabricate coatings with different kinetics of Sr(2+) into physiological media, whereas the release of therapeutically relevant strontium doses could be sustained over several weeks. Morphological and crystallographic examinations of the immersed coatings revealed that the degradation of struvite and the release of Sr(2+) ions were accompanied by a transformation of the coating to a calcium phosphate based phase similar to low-crystalline hydroxyapatite. These findings showed that strontium doped struvite coatings may provide a promising degradable coating system for the local application of strontium or other biologically active metal ions in the implant-bone interface. PMID:27287100

  17. Electrodes and electrochemical storage cells utilizing tin-modified active materials

    DOEpatents

    Anani, Anaba; Johnson, John; Lim, Hong S.; Reilly, James; Schwarz, Ricardo; Srinivasan, Supramaniam

    1995-01-01

    An electrode has a substrate and a finely divided active material on the substrate. The active material is ANi.sub.x-y-z Co.sub.y Sn.sub.z, wherein A is a mischmetal or La.sub.1-w M.sub.w, M is Ce, Nd, or Zr, w is from about 0.05 to about 1.0, x is from about 4.5 to about 5.5, y is from 0 to about 3.0, and z is from about 0.05 to about 0.5. An electrochemical storage cell utilizes such an electrode as the anode. The storage cell further has a cathode, a separator between the cathode and the anode, and an electrolyte.

  18. Carbon foam anode modified by urea and its higher electrochemical performance in marine benthic microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Fu, Yubin; Lu, Zhikai; Zai, Xuerong; Wang, Jian

    2015-08-01

    Electrode materials have an important effect on the property of microbial fuel cell (MFC). Carbon foam is utilized as an anode and further modified by urea to improve its performance in marine benthic microbial fuel cell (BMFC) with higher voltage and output power. The electrochemical properties of plain carbon foam (PC) and urea-modified carbon foam (UC) are measured respectively. Results show that the UC obtains better wettability after its modification and higher anti-polarization ability than the PC. A novel phenomenon has been found that the electrical potential of the modified UC anode is nearly 100 mV lower than that of the PC, reaching -570 ±10 mV ( vs. SCE), and that it also has a much higher electron transfer kinetic activity, reaching 9399.4 mW m-2, which is 566.2-fold higher than that from plain graphite anode (PG). The fuel cell containing the UC anode has the maximum power density (256.0 mW m-2) among the three different BMFCs. Urea would enhance the bacteria biofilm formation with a more diverse microbial community and maintain more electrons, leading to a lower anodic redox potential and higher power output. The paper primarily analyzes why the electrical potential of the modified anode becomes much lower than that of others after urea modification. These results can be utilized to construct a novel BMFC with higher output power and to design the conditioner of voltage booster with a higher conversion ratio. Finally, the carbon foam with a bigger pore size would be a potential anodic material in conventional MFC.

  19. Supramolecular assembly of glucose oxidase on concanavalin A--modified gold electrodes.

    PubMed

    Pallarola, Diego; Queralto, Nuria; Battaglini, Fernando; Azzaroni, Omar

    2010-07-28

    There is a growing quest for the construction of functional supramolecular architectures to efficiently translate (bio)chemical events into easily measurable signals. This interest originates from its inherent scientific relevance as well as from their potential applications in the ever-flourishing areas of bioelectronics and biosensing. Herein, we describe the immobilization of glycoproteins onto electrode surfaces based on recognition-mediated supramolecular processes. Quartz crystal microbalance with dissipation (QCM-D), surface plasmon resonance (SPR) spectroscopy, and electrochemical (EC) measurements were used to characterize the structural and functional features of these bio-supramolecular systems. Carbohydrate-lectin interactions were successfully used to build up stable assemblies of glucose oxidase (GOx) layers mediated by the recognition properties of concanavalin A supramolecular architectures. The catalytic response of GOx indicates that the whole population of enzymes incorporated in the supramolecular architecture is fully active. Even though lectin-carbohydrate interactions are rather weak, the multivalency effects prevailing in the supramolecular assembly confer remarkable stability to the interfacial architecture, thus preventing the release of the enzyme from the surface even with high glucose (ligand) concentrations. This approach represents a simple and straightforward route to locally address functional glycoproteins at interfaces. In this context, we consider that the versatility of a supramolecular assembly using biological interactions could open up new ways of envisioning or to generate new ideas for the future development of highly efficient bioelectronic platforms.

  20. Solid phase extraction of gold(III) on silica gel modified with benzoylthiourea prior to its determination by flame atomic absorption spectrometry.

    PubMed

    Bozkurt, Serap Seyhan; Merdivan, Melek

    2009-11-01

    A new method has been developed for the determination of gold based on separation and preconcentration using silica gel modified with benzoylthiourea. The optimum experimental parameters for preconcentration of gold, such as acid concentration, sample flow rate, eluent and matrix ions, have been investigated. Gold could be quantitatively retained in the 0.25-2.0 mol L(-1) HCl and HNO(3) concentrations, and then eluted completely with 0.5 mol L(-1) thiourea in 1.0 mol L(-1) HCl. The sorption capacity of gold(III) is 0.92 +/- 0.04 mmol g(-1) with a high enrichment factor of 267. The relative standard deviation of the method, RSD%, was found as 1.2% for 0.1 microg mL(-1). The detection limit for gold was 1.4 microg L(-1). The validation of the proposed method was checked by the analysis of certified reference soil materials. The presented procedure was applied to the determination of gold in some environmental samples.

  1. ELECTROCHEMICAL DETERMINATION OF HYDROGEN SULFIDE AT CARBON NANOTUBE MODIFIED ELECTRODES. (R830900)

    EPA Science Inventory

    Carbon nanotube (CNT) modified glassy carbon electrodes exhibiting a strong and stable electrocatalytic response towards sulfide are described. A substantial (400 mV) decrease in the overvoltage of the sulfide oxidation reaction (compared to ordinary carbon electrodes) is...

  2. A nonenzymatic biosensor based on gold electrodes modified with peptide self-assemblies for detecting ammonia and urea oxidation.

    PubMed

    Bianchi, Roberta C; da Silva, Emerson Rodrigo; Dall'Antonia, Luiz H; Ferreira, Fabio Furlan; Alves, Wendel Andrade

    2014-09-30

    We have developed a nonenzymatic biosensor for the detection of ammonia and urea oxidation based on the deposition of peptide microstructures onto thiolated gold electrodes. FF-MNSs/MCP/Au assemblies were obtained by modifying gold substrates with 4-mercaptopyridine (MCP), followed by coating with l,l-diphenylalanine micro/nanostructures (FF-MNSs) grown in the solid-vapor phase. Benzene rings and amide groups with peptide micro/nanostructures interact with synthetic NH4(+) receptors through cation-π and hydrogen bonding. AuOH clusters on the Au surface provided the catalytic sites. The application of a predetermined concentration of analytes at the peptide interfaces activated the catalytic sites. We observed a relationship between the stability of films and the crystal structure of peptides, and we organized the FF-MNSs into an orthorhombic symmetry that was the most suitable assembly for creation of our biosensors. At 0.1 mol L(-1) NaOH, these FF-MNSs/MCP/Au electrodes have electrocatalytic properties regarding ammonia and urea oxidation that are comparable to those of enzyme-based architectures. Under optimal conditions, the electrocatalytic response is proportional to the ammonia and urea concentration in the range 0.1-1.0 mmol L(-1). The sensitivity was calculated as 2.83 and 81.3 μA mmol L(-1) cm(-2) for ammonia and urea, respectively, at +0.40 V (vs SCE). Our detection method is easy to follow, does not require a mediator or enzyme, and has strong potential for detecting urea via nonenzymatic routes.

  3. Visual detection of STAT5B gene expression in living cell using the hairpin DNA modified gold nanoparticle beacon.

    PubMed

    Xue, Jianpeng; Shan, Lingling; Chen, Haiyan; Li, Yang; Zhu, Hongyan; Deng, Dawei; Qian, Zhiyu; Achilefu, Samuel; Gu, Yueqing

    2013-03-15

    Signal transducer and activator of transcription 5B (STAT5B) is an important protein in JAK-STAT signaling pathway that is responsible for the metastasis and proliferation of tumor cells. Determination of the STAT5B messenger Ribonucleic Acid (mRNA) relating to the STAT5B expression provides insight into the mechanism of tumor progression. In this study, we designed and used a special hairpin deoxyribonucleic acid (DNA) for human STAT5B mRNA to functionalize gold nanoparticles, which served as a beacon for detecting human STAT5B expression. Up to 90% quenching efficiency was achieved. Upon hybridizing with the target mRNA, the hairpin DNA modified gold nanoparticle beacons (hDAuNP beacons) release the fluorophores attached at 5' end of the oligonucleotide sequence. The fluorescence properties of the beacon before and after the hybridization with the complementary DNA were confirmed in vitro. The stability of hDAuNP beacons against degradation by DNase I and GSH indicated that the prepared beacon is stable inside cells. The detected fluorescence in MCF-7 cancer cells correlates with the specific STAT5B mRNA expression, which is consistent with the result from PCR measurement. Fluorescence microscopy showed that the hDAuNP beacons internalized in cells without using transfection agents, with intracellular distribution in the cytoplasm rather than the nucleus. The results demonstrated that this beacon could directly provide quantitative measurement of the intracellular STAT5B mRNA in living cells. Compared to the previous approaches, this beacon has advantages of higher target to background ratio of detection and an increased resistance to nuclease degradation. The strategy reported in this study is a promising approach for the intracellular measurement of RNA or protein expression in living cells, and has great potential in the study of drug screening and discovery.

  4. Rapid prototyping of microfluidic devices with integrated wrinkled gold micro-/nano textured electrodes for electrochemical analysis.

    PubMed

    Gabardo, C M; Adams-McGavin, R C; Vanderfleet, O M; Soleymani, L

    2015-08-21

    Fully-integrated electro-fluidic systems with micro-/nano-scale features have a wide range of applications in lab-on-a-chip systems used for biosensing, biological sample processing, and environmental monitoring. Rapid prototyping of application-specific electro-fluidic systems is envisioned to facilitate the testing, validation, and market translation of several lab-on-a-chip systems. Towards this goal, we developed a rapid prototyping process for creating wrinkled micro-/nano-textured electrodes on shrink memory polymers, fabricating microfluidics using molds patterned by a craft-cutter, and bonding electrical and fluidic circuitries using a PDMS partial curing method optimized for creating void-free bonds at the side walls and surfaces of tall (>5 μm) micro-/nano-textured wrinkled electrodes. The resulting electro-fluidic devices, featuring closely spaced high topography electrodes for electrochemical analysis, can withstand flow-rates and burst pressures larger than 25 mL min(-1) and 125 kPa, respectively. In addition, the fully-integrated electrochemical flow-cell developed here demonstrates excellent electrochemical behaviour, with negligible scan to scan variation for over 100 cyclic voltammetry scans, and expected redox signatures measured under various voltage scan rates and fluidic flow rates.

  5. Rapid prototyping of microfluidic devices with integrated wrinkled gold micro-/nano textured electrodes for electrochemical analysis.

    PubMed

    Gabardo, C M; Adams-McGavin, R C; Vanderfleet, O M; Soleymani, L

    2015-08-21

    Fully-integrated electro-fluidic systems with micro-/nano-scale features have a wide range of applications in lab-on-a-chip systems used for biosensing, biological sample processing, and environmental monitoring. Rapid prototyping of application-specific electro-fluidic systems is envisioned to facilitate the testing, validation, and market translation of several lab-on-a-chip systems. Towards this goal, we developed a rapid prototyping process for creating wrinkled micro-/nano-textured electrodes on shrink memory polymers, fabricating microfluidics using molds patterned by a craft-cutter, and bonding electrical and fluidic circuitries using a PDMS partial curing method optimized for creating void-free bonds at the side walls and surfaces of tall (>5 μm) micro-/nano-textured wrinkled electrodes. The resulting electro-fluidic devices, featuring closely spaced high topography electrodes for electrochemical analysis, can withstand flow-rates and burst pressures larger than 25 mL min(-1) and 125 kPa, respectively. In addition, the fully-integrated electrochemical flow-cell developed here demonstrates excellent electrochemical behaviour, with negligible scan to scan variation for over 100 cyclic voltammetry scans, and expected redox signatures measured under various voltage scan rates and fluidic flow rates. PMID:26178719

  6. Electrochemical sensor based on molecularly imprinted film at Au nanoparticles-carbon nanotubes modified electrode for determination of cholesterol.

    PubMed

    Ji, Jian; Zhou, Zhihui; Zhao, Xiaolian; Sun, Jiadi; Sun, Xiulan

    2015-04-15

    A novel electrochemical sensor for cholesterol (CHO) detection based on molecularly imprinted polymer (MIP) membranes on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWNTs) and Au nanoparticles (AuNPs) was constructed. p-Aminothiophenol (P-ATP) and CHO were assembled on the surface of the modified GCE by the formation of Au-S bonds and hydrogen-bonding interactions, and polymer membranes were formed by electropolymerization in a polymer solution containing p-ATP, HAuCl4, tetrabutylammonium perchlorate (TBAP) and the template molecule CHO. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements were used to monitor the electropolymerization process and its optimization, which was further characterized by scanning electron microscopy (SEM). The linear response range of the MIP sensor was between 1×10(-13) and 1×10(-9)molL(-1), and the limit of detection (LOD) were 3.3×10(-14)molL(-1). The proposed system has the potential for application in clinical diagnostics of cholesterol with high-speed real-time detection capability, low sample consumption, high sensitivity, low interference and good stability.

  7. A strategy for fabricating nanoporous gold films through chemical dealloying of electrochemically deposited Au-Sn alloys

    NASA Astrophysics Data System (ADS)

    Xu, Yantong; Ke, Xi; Yu, Changchun; Liu, Shaofang; Zhao, Jie; Cui, Guofeng; Higgins, Drew; Chen, Zhongwei; Li, Qing; Wu, Gang

    2014-11-01

    We report a novel strategy for the fabrication of nanoporous gold (NPG) films. The fabrication process involves the electrodeposition of a gold-tin alloy, followed by subsequent chemical dealloying of tin. Scanning electron microscopy (SEM) images show a bicontinuous nanoporous structure formed on the substrates after chemical dealloying. Energy dispersive x-ray (EDX) analysis indicates that there are no impurities in the Au-Sn alloy film with an average composition of 58 at. % Au and 42 at. % Sn. After dealloying, only gold remains in the NPG film indicating the effectiveness of this technique. X-ray diffraction (XRD) results reveal that the as-prepared Au-Sn alloy film is composed of two phases (Au5Sn and AuSn), while the NPG film is composed of a single phase (Au). We demonstrate that this approach enables the fabrication of NPG films, either freestanding or supported on various conductive substrates such as copper foil, stainless steel sheet and nickel foam. The resulting NPG electrode exhibits enhanced electrocatalytic activity toward both H2O2 reduction and methanol oxidation compared to the polished Au disc electrode. Our strategy provides a general method to fabricate high quality NPG films on conductive substrates, which will broaden the application potential of NPG or NPG-based materials in various fields such as catalysis, optics and sensor technology.

  8. Nanostructure Modified Microelectrode for Electrochemical Detection of Dopamine with Ascorbic Acid and Uric Acid.

    PubMed

    Kim, Kyeong-Jun; Choi, Jin-Ha; Pyo, Su-Hyun; Yun, Kwang-Seok; Lee, Ji-Young; Choi, Jeong-Woo; Oh, Byung-Keun

    2016-03-01

    Dopamine (DA) is one kind of neurotransmitter in central nervous system which is indicator of neural disease. For this reason, determination of DA concentration in central nervous system is very important for early diagnosis of neural disease. In this study, we designed micro electrode array and fabricated by MEMS technology. Furthermore, we fabricated 3-D conducting nanostructure on electrode surface for enhanced sensitivity and selectivity due to increased surface area. Compared with macro and normal micro electrode, the 3-D nanostructure modified micro electrode shows better electrical performance. These surface modified pin type electrode was applied to detect low concentration of DA and successfully detect various concentration of DA from 100 μM to 1 μM with linear relationship in the presence of ascorbic acid and uric acid. From these results, our newly designed electrode shows possibility to be applied as brain biosensor for neural disease diagnosis such as Parkinson's diseases. PMID:27455760

  9. A highly sensitive electrochemical biosensor for catechol using conducting polymer reduced graphene oxide-metal oxide enzyme modified electrode.

    PubMed

    Sethuraman, V; Muthuraja, P; Anandha Raj, J; Manisankar, P

    2016-10-15

    The fabrication, characterization and analytical performances were investigated for a catechol biosensor, based on the PEDOT-rGO-Fe2O3-PPO composite modified glassy carbon (GC) electrode. The graphene oxide (GO) doped conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) was prepared through electrochemical polymerization by potential cycling. Reduction of PEDOT-GO was carried out by amperometric method. Fe2O3 nanoparticles were synthesized in ethanol by hydrothermal method. The mixture of Fe2O3, PPO and glutaraldehyde was casted on the PEDOT-rGO electrode. The surface morphology of the modified electrodes was studied by FE-SEM and AFM. Cyclic voltammetric studies of catechol on the enzyme modified electrode revealed higher reduction peak current. Determination of catechol was carried out successfully by Differential Pulse Voltammetry (DPV) technique. The fabricated biosensor investigated shows a maximum current response at pH 6.5. The catechol biosensor exhibited wide sensing linear range from 4×10(-8) to 6.20×10(-5)M, lower detection limit of 7×10(-9)M, current maxima (Imax) of 92.55µA and Michaelis-Menten (Km) constant of 30.48µM. The activation energy (Ea) of enzyme electrode is 35.93KJmol(-1) at 50°C. There is no interference from d-glucose and l-glutamic acid, ascorbic acid and o-nitrophenol. The PEDOT-rGO-Fe2O3-PPO biosensor was stable for at least 75 days when stored in a buffer at about 4°C. PMID:26751827

  10. A silk derived carbon fiber mat modified with Au@Pt urchilike nanoparticles: A new platform as electrochemical microbial biosensor.

    PubMed

    Deng, Liu; Guo, Shaojun; Zhou, Ming; Liu, Ling; Liu, Chang; Dong, Shaojun

    2010-06-15

    We present here a facile and efficient route to prepare silk derived carbon mat modified with Au@Pt urchilike nanoparticles (Au@Pt NPs) and develop an Escherichia coli (E. coli)-based electrochemical sensor using this material. Silk is a natural protein fiber, and it is abundant with kinds of functionalities which are important in the development of the derived material. The S-derived carbon fiber mat have amino, pyridine and carbonyl functional groups, these natural existent functionalities allow the Au@Pt NPs to self-assemble on the carbon fiber surface and provide a biocompatible microenvironment for bacteria. The Au@Pt NPs modified S-derived carbon fiber is sensitive to detect the E. coli activities with a low detection limit, where glucose is used as a prelimiltary substrate to evaluate them. The performance of Au@Pt/carbon fiber mat based biosensor is much better than that of commercial carbon paper based biosensor. The high sensitivity of this biosensor stems from the unique electrocatalytic properties of Au@Pt urchilike NPs and quinone groups presented in S-derived carbon fiber. This biosensor is also tested for detection of organophosphate pesticides, fenamiphos. The relative inhibition of E. coli activity is linear with -log[fenamiphos] at the concentration range from 0.5mg/L to 36.6 mg/L with lowest observable effect concentration (LOEC) of 0.09 mg/L. The Au@Pt NPs modified S-derived carbon fiber mat possesses high conductivity, biocompatibility and high electrocatalytic activity and be can used as advanced electrode materials for microbial biosensor improvement. The microbial biosensor based on this material shows potential applications in environmental monitoring.

  11. Gold nanoparticles modified with self-assembled hybrid monolayer of triblock aptamers as a photoreversible anticoagulant.

    PubMed

    Huang, San-Shan; Wei, Shih-Chun; Chang, Huan-Tsung; Lin, Han-Jia; Huang, Chih-Ching

    2016-01-10

    We demonstrated that thrombin-binding aptamer-conjugated gold nanoparticles (TBA-Au NPs), prepared from a self-assembled hybrid monolayer (SAHM) of triblock aptamers on Au NPs (13 nm), can effectively inhibit thrombin activity toward fibrinogen. The first block poly(adenine) at the end of the triblock TBA was used for the self-assembly on Au NP surface. The second block, in the middle of TBA, was composed of oligonucleotides that could hybridize with each other. The third block, containing TBA15 (15-base, binding to the exosite I of thrombin) and TBA29 (29-base, binding to the exosite II of thrombin) provided bivalent interaction with thrombin. The SAHM triblock aptamers have optimal distances between TBA15 and TBA29, aptamer density, and orientation on the Au NP surfaces. These properties strengthen the interactions with thrombin (Kd=1.5 × 10(-11)M), resulting in an extremely high anticoagulant potency. The thrombin clotting time mediated by SAHM TBA15/TBA29-Au NPs was >10 times longer than that of four commercially available drugs (heparin, argatroban, hirudin, or warfarin). In addition, the rat-tail bleeding assay time further demonstrated that the SAHM TBA15/TBA29-Au NPs were superior to heparin. The SAHM TBA15/TBA29-Au NPs exhibited excellent stability in the human plasma (half-life >14 days) and good biocompatibility (low cytotoxicity and hemolysis). Most interestingly, the inhibition by SAHM TBA15/TBA29-Au NPs was controllable by the irradiation of green laser, via heat transfer-induced TBA release from Au NPs. Therefore, these easily prepared (self-assembled), low cost (non-thiolated aptamer), photo-controllable, multivalent TBA15/TBA29-Au NPs (high density of TBA15/TBA29 on Au NPs) show good potential for the treatment of various diseases related to blood-clotting disorders. Our study opens up the possibility of regulation of molecule binding, protein recognition, and enzyme activity using SAHM aptamer-functionalized nanomaterials.

  12. Gold nanoparticles modified with self-assembled hybrid monolayer of triblock aptamers as a photoreversible anticoagulant.

    PubMed

    Huang, San-Shan; Wei, Shih-Chun; Chang, Huan-Tsung; Lin, Han-Jia; Huang, Chih-Ching

    2016-01-10

    We demonstrated that thrombin-binding aptamer-conjugated gold nanoparticles (TBA-Au NPs), prepared from a self-assembled hybrid monolayer (SAHM) of triblock aptamers on Au NPs (13 nm), can effectively inhibit thrombin activity toward fibrinogen. The first block poly(adenine) at the end of the triblock TBA was used for the self-assembly on Au NP surface. The second block, in the middle of TBA, was composed of oligonucleotides that could hybridize with each other. The third block, containing TBA15 (15-base, binding to the exosite I of thrombin) and TBA29 (29-base, binding to the exosite II of thrombin) provided bivalent interaction with thrombin. The SAHM triblock aptamers have optimal distances between TBA15 and TBA29, aptamer density, and orientation on the Au NP surfaces. These properties strengthen the interactions with thrombin (Kd=1.5 × 10(-11)M), resulting in an extremely high anticoagulant potency. The thrombin clotting time mediated by SAHM TBA15/TBA29-Au NPs was >10 times longer than that of four commercially available drugs (heparin, argatroban, hirudin, or warfarin). In addition, the rat-tail bleeding assay time further demonstrated that the SAHM TBA15/TBA29-Au NPs were superior to heparin. The SAHM TBA15/TBA29-Au NPs exhibited excellent stability in the human plasma (half-life >14 days) and good biocompatibility (low cytotoxicity and hemolysis). Most interestingly, the inhibition by SAHM TBA15/TBA29-Au NPs was controllable by the irradiation of green laser, via heat transfer-induced TBA release from Au NPs. Therefore, these easily prepared (self-assembled), low cost (non-thiolated aptamer), photo-controllable, multivalent TBA15/TBA29-Au NPs (high density of TBA15/TBA29 on Au NPs) show good potential for the treatment of various diseases related to blood-clotting disorders. Our study opens up the possibility of regulation of molecule binding, protein recognition, and enzyme activity using SAHM aptamer-functionalized nanomaterials. PMID:26643617

  13. Adsorption properties of aluminium oxide modified with palladium, gold, and cerium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Lanin, S. N.; Bannykh, A. A.; Vinogradov, A. E.; Kovaleva, N. V.; Lanina, K. S.; Nikolaev, S. A.

    2016-07-01

    The adsorption properties of nanocomposites based on γ-Al2O3 modified with CeO x , Au/CeO x , and Pd/CeO x nanoparticles with contents of deposited metals ranging from 0.07 to 1.71 wt % are investigated by means of dynamic sorption method. n-Alkanes (C6-C8), acetonitrile, diethyl ether, tetrahydrofuran, and dioxane are used as test adsorbates. Adsorption isotherms are measured, and the isosteric heats of adsorption of a number of test adsorbates are calculated. Electron-donor and electron-acceptor characteristics of the surfaces of γ-Al2O3-based nanocomposites are estimated. It is shown that Au(0.1%)/CeO x (0.07%)/γ-Al2O3 nanocomposite, which has the lowest content of nanoparticles of the deposited metals, has the highest adsorption activity.

  14. Photo-electrochemical communication between cyanobacteria (Leptolyngbia sp.) and osmium redox polymer modified electrodes.

    PubMed

    Hasan, Kamrul; Bekir Yildiz, Huseyin; Sperling, Eva; Conghaile, Peter Ó; Packer, Michael A; Leech, Dónal; Hägerhäll, Cecilia; Gorton, Lo

    2014-12-01

    Photosynthetic microbial fuel cells (PMFCs) are an emerging technology for renewable solar energy conversion. Major efforts have been made to explore the electrogenic activity of cyanobacteria, mostly using practically unsustainable reagents. Here we report on photocurrent generation (≈8.64 μA cm(-2)) from cyanobacteria immobilized on electrodes modified with an efficient electron mediator, an Os(2+/3+) redox polymer. Upon addition of ferricyanide to the electrolyte, cyanobacteria generate the maximum current density of ≈48.2 μA cm(-2).

  15. Photo-electrochemical communication between cyanobacteria (Leptolyngbia sp.) and osmium redox polymer modified electrodes.

    PubMed

    Hasan, Kamrul; Bekir Yildiz, Huseyin; Sperling, Eva; Conghaile, Peter Ó; Packer, Michael A; Leech, Dónal; Hägerhäll, Cecilia; Gorton, Lo

    2014-12-01

    Photosynthetic microbial fuel cells (PMFCs) are an emerging technology for renewable solar energy conversion. Major efforts have been made to explore the electrogenic activity of cyanobacteria, mostly using practically unsustainable reagents. Here we report on photocurrent generation (≈8.64 μA cm(-2)) from cyanobacteria immobilized on electrodes modified with an efficient electron mediator, an Os(2+/3+) redox polymer. Upon addition of ferricyanide to the electrolyte, cyanobacteria generate the maximum current density of ≈48.2 μA cm(-2). PMID:25325401

  16. Small organic molecules detection based on aptamer-modified gold nanoparticles-enhanced quartz crystal microbalance with dissipation biosensor.

    PubMed

    Zheng, Bin; Cheng, Sheng; Liu, Wei; Lam, Michael Hon-Wah; Liang, Haojun

    2013-07-15

    Small molecules are difficult to detect by the conventional quartz crystal microbalance with dissipation (QCM-D) technique directly because the changes in frequency resulting from the binding processes of small biomolecules are often small. In the current study, an aptamer-based gold nanoparticles (AuNPs)-enhanced sensing strategy for detection of small molecules was developed. The QCM crystal was first modified with a layer of thiolated linker DNA, which can be partly base-paired with the detection part containing the adenosine aptamer sequence. In the presence of adenosine, the aptamer bound with adenosine and folded to the complex structure, which precluded the reporter part carrying AuNPs to combine with the random coiled detection part. Therefore, the lower the concentration of adenosine, the more AuNPs combined to the crystal. The resulting aptasensor showed a linear response to the increase of the adenosine concentration in the range of 0-2 μM with a linear correlation of r=0.99148 and a detection limit of 65 nM. Moreover, the aptasensor exhibited several excellent characteristics such as high sensitivity, selectivity, good stability, and reproducibility.

  17. A gold nanoparticles-modified aptamer beacon for urinary adenosine detection based on structure-switching/fluorescence-"turning on" mechanism.

    PubMed

    Zhang, Jin-Quan; Wang, Yong-Sheng; Xue, Jin-Hua; He, Yan; Yang, Hui-Xian; Liang, Jun; Shi, Lin-Fei; Xiao, Xi-Lin

    2012-11-01

    A novel small molecule probe, aptamer beacon (AB), was introduced for adenosine (Ade) recognition and quantitative analysis. The Ade aptamer was engineered into an aptamer beacon by adding a gold nanoparticle-modified nucleotide sequence which is complementary to aptamer sequence (FDNA) at the 3'-end of FDNA. The fluorescence signal "turning on" was observed when AB was bound to Ade, which is attributed to a significant conformational change in AB from a FDNA/QDNA duplex to a FDNA-Ade complex. The Ade measurement was carried out in 20 mmol L(-1) Tris-HCl buffer solution of pH 7.4, ΔF signal linearly correlated with the concentration of Ade over the range of 2.0×10(-8) to 1.8×10(-6) mol L(-1). The limit of detection (LOD) for Ade is 6.0×10(-9) mol L(-1) with relative standard deviations (R.S.D) of 3.64-5.36%, and the recoveries were 98.6%, 100%, 102% (n=6), respectively. The present method has been successfully applied to determine Ade in human urine samples, and the obtained results were in good agreement with those obtained by the HPLC method. Our investigation shows that the unique properties of the AB could provide a promising potential for small molecules detection, and be benefit to extend the application of aptamer beacon technique.

  18. Graphitic electrodes modified with boron and nitrogen for electrochemical energy storage enhancement

    NASA Astrophysics Data System (ADS)

    Xiong, Guoping; Paul, Rajib; Reifenberger, Ron; Fisher, Timothy

    2013-03-01

    Electrodes based on carbon nanomaterials (carbon nanotubes or graphitic nanopetals) have been modified with boron (B) and nitrogen (N) through a facile microwave heating cycle. During the microwave heating, the electrodes are immersed in a precursor solution consisting of urea and boric acid dissolved in either water or methanol. After microwave heating and overnight vacuum drying, the electrodes are again heated in nitrogen to remove unreacted chemicals and to form CxBN. Hydrogen plasma was then used to remove any residual boron oxide from the surface of the electrodes. Carbon nanotubes modified with B and N exhibited higher lithium storage capacity as compared to pure carbon nanotube electrodes. We note that the modification appears to produce a highly unexpected and substantial cycle-to-cycle improvement in battery capacity as the electrode cycles through hundreds of charge-discharge iterations. This process can be applied to other carbon-based electrodes, which themselves are recognized for their high performance, to add further improvements. AFOSR MURI No. 105800

  19. Electrochemical glucose biosensor based on nickel oxide nanoparticle-modified carbon paste electrode.

    PubMed

    Erdem, Ceren; Zeybek, Derya Koyuncu; Aydoğdu, Gözde; Zeybek, Bülent; Pekyardımcı, Sule; Kılıç, Esma

    2014-08-01

    In the present work, we designed an amperometric glucose biosensor based on nickel oxide nanoparticles (NiONPs)-modified carbon paste electrode. The biosensor was prepared by incorporation of glucose oxidase and NiONPs into a carbon paste matrix. It showed good analytical performances such as high sensitivity (367 μA mmolL(-1)) and a wide linear response from 1.9×10(-3) mmolL(-1) to 15.0 mmolL(-1) with a limit of detection (0.11 μmolL(-1)). The biosensor was used for the determination of glucose in human serum samples. The results illustrate that NiONPs have enormous potential in the construction of biosensor for determination of glucose.

  20. An electrochemical investigation of glucose oxidase at a CdS nanoparticles modified electrode.

    PubMed

    Huang, Yinxi; Zhang, Wenjun; Xiao, Han; Li, Genxi

    2005-11-15

    The direct electrochemistry of glucose oxidase (GOD) adsorbed on a CdS nanoparticles modified pyrolytic graphite electrode was investigated, where the enzyme demonstrated significantly enhanced electron-transfer reactivity. GOD adsorbed on CdS nanoparticles maintained its bioactivity and structure, and could electro-catalyze the reduction of dissolved oxygen, which resulted in a great increase of the reduction peak current. Upon the addition of glucose, the reduction peak current decreased, which could be used for glucose detection. Performance and characteristics of the fabricated glucose biosensor were assessed with respect to detection limit, sensitivity, storage stability and interference exclusion. The results showed that the fabricated biosensor was sensitive and stable in detecting glucose, indicating that CdS nanoparticle was a good candidate material for the immobilization of enzyme in glucose biosensor construction. PMID:16242622