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Sample records for electrochemical modified gold

  1. 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

  2. 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

  3. Electrochemical investigation of tryptophan at gold nanoparticles modified electrode in the presence of sodium dodecylbenzene sulfonate.

    PubMed

    Li, Chunya; Ya, Yu; Zhan, Guoqing

    2010-03-01

    Glassy carbon electrode modified with gold nanoparticles was prepared using electrodeposition at constant potential of -0.20V, and characterized with scanning electron microscopy and electrochemical techniques. Voltammetry was employed to study the electrochemical behaviors of tryptophan at the Au nanoparticles modified electrode in the presence of sodium dodecylbenzene sulfonate. The results showed that the Au nanoparticles modified electrode had good performance for the electrochemical oxidation of tryptophan. Compared with the unmodified electrode, the Au nanoparticles modified electrode improved the adsorption of tryptophan on the nanointerface and amplified its current response. The oxidation peak potential showed a negative shift of 50mV in the presence of sodium dodecylbenzene sulfonate indicating that the electron transfer between the electrode and bulk solution of tryptophan was facilitated. Experimental parameters for tryptophan determination, such as deposition time, pH value, and accumulation conditions have been optimized. The oxidation peak current was linearly dependent on the tryptophan concentration and a calibration curve was obtained in the concentration range of 9.0x10(-8)molL(-1) to 5.0x10(-5)molL(-1) with detection limit of 8.0x10(-8)molL(-1) (S/N=3). PMID:20015621

  4. An electrochemical sulfite biosensor based on gold coated magnetic nanoparticles modified gold electrode.

    PubMed

    Rawal, Rachna; Chawla, Sheetal; Pundir, Chandra Shekhar

    2012-01-15

    A sulfite oxidase (SO(X)) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto carboxylated gold coated magnetic nanoparticles (Fe(3)O(4)@GNPs) electrodeposited onto the surface of a gold (Au) electrode through N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC)-N-hydroxy succinimide (NHS) chemistry. An amperometric sulfite biosensor was fabricated using SO(X)/Fe(3)O(4)@GNPs/Au electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode. The working electrode was characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Cyclic Voltammetry (CV), Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS) before and after immobilization of SO(X). The biosensor showed optimum response within 2s when operated at 0.2V (vs. Ag/AgCl) in 0.1 M Tris-HCl buffer, pH 8.5 and at 35 °C. Linear range and detection limit were 0.50-1000 μM and 0.15 μM (S/N=3) respectively. Biosensor was evaluated with 96.46% recovery of added sulfite in red wine and 1.7% and 3.3% within and between batch coefficients of variation respectively. Biosensor measured sulfite level in red and white wines. There was good correlation (r=0.99) between red wines sulfite value by standard DTNB (5,5'-dithio-bis-(2-nitrobenzoic acid)) method and the present method. Enzyme electrode was used 300 times over a period of 4 months, when stored at 4 °C. Biosensor has advantages over earlier biosensors that it has excellent electrocatalysis towards sulfite, lower detection limit, higher storage stability and no interference by ascorbate, cysteine, fructose and ethanol. PMID:22035973

  5. Electrochemical investigation of methyl parathion at gold-sodium dodecylbenzene sulfonate nanoparticles modified glassy carbon electrode.

    PubMed

    Li, Chunya; Wang, Zhengguo; Zhan, Guoqin

    2011-01-01

    A gold/sodium dodecylbenzene sulfonate nanoparticles modified glassy carbon electrode (nano-Au/SDBS/GCE) was electrochemically fabricated with a constant potential at -0.4V. The obtained nano-Au/SDBS/GCE was characterized with scanning electronic microscopy, X-ray photoelectron spectroscopy and electrochemical techniques. Electrochemical behaviors of methyl parathion at the nano-Au/SDBS/GCE were thoroughly investigated. Compared to the unmodified electrode, the peak current obviously increased and the oxidation peak potential negatively shifted. These changes indicated that the composite nanoparticles possess good electrocatalytic performance on the electrochemical reaction of methyl parathion. Experimental parameters such as deposition time, pH value and accumulation conditions were optimized. Under optimum conditions, the peak current corresponding to the oxidation of the hydroxylamine group was found in a good linear relationship with the methyl parathion concentration. In addition, a calibration curve with excellent linearity was obtained in the concentration range from 5.0×10(-7)molL(-1) to 1.0×10(-4)molL(-1) with an estimated detection limit of 8.6×10(-8)molL(-1) (S/N=3). The successful determination of methyl parathion in real samples demonstrated the usefulness and potential applications of this method. PMID:20832258

  6. 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

  7. 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...

  8. Electrochemical behavior of gold nanoparticles modified nitrogen incorporated tetrahedral amorphous carbon and its application in glucose sensing.

    PubMed

    Liu, Aiping; Wu, Huaping; Qiu, Xu; Tang, Weihua

    2011-12-01

    Gold nanoparticles (NPs) with 10-50 nm in diameter were synthesized on nitrogen incorporated tetrahedral amorphous carbon (ta-C:N) thin film electrode by electrodeposition. The deposition and nucleation processes of Au on ta-C:N surface were investigated by cyclic voltammetry and chronoamperometry. The morphology of Au NPs was characterized by scanned electron microscopy. The electrochemical properties of Au NPs modified ta-C:N (ta-C:N/Au) electrode and its ability to sense glucose were investigated by voltammetric and amperometric measurements. The potentiostatic current-time transients showed a progressive nucleation process and diffusion growth of Au on the surface of ta-C:N film according to the Scharifker-Hills model. The Au NPs acted as microelectrodes improved the electron transfer and electrocatalytic oxidation of glucose on ta-C:N electrode. The ta-C:N/Au electrode exhibited fast current response, a linear detection range of glucose from 0.5 to 25 mM and a detection limit of 120 microM, which hinted its potential application as a glucose biosensor. PMID:22409057

  9. 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

  10. Electrochemical albumin sensing based on silicon nanowires modified by gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Kwon, Dae Hoon; An, Hyeun Hwan; Kim, Hee-Soo; Lee, Jong Ho; Suh, Sang Hee; Kim, Young Ho; Yoon, Chong Seung

    2011-03-01

    Si nanowires (SiNWs) were modified by Au nanoparticles (AuNPs) using a self-assembled monolayer of aminopropyltriethoxysilane (APTES) and used for direct sensing of the bovine serum albumin (BSA). It was shown that repeated thermal treatment of the sensor greatly enhanced the reliability of the SiNW sensor by increasing the electrical conductivity largely from carbonization of the APTES molecules and from bringing the AuNPs in intimate contact with the SiNW surface. The AuNP-modified SiNW array sensor was able to detect 1-7 μM of BSA. The sensor exhibited a good sensitivity over the tested concentration range and linear behavior. It is expected that the proposed label-free biosensor can be further developed to selectively detect and quantify biomolecules other than BSA.

  11. 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

  12. An electrochemical ELISA-like immunosensor for miRNAs detection based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes.

    PubMed

    Tran, H V; Piro, B; Reisberg, S; Huy Nguyen, L; Dung Nguyen, T; Duc, H T; Pham, M C

    2014-12-15

    We design an electrochemical immunosensor for miRNA detection, based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes. An original immunological approach is followed, using antibodies directed to DNA.RNA hybrids. An electrochemical ELISA-like amplification strategy was set up using a secondary antibody conjugated to horseradish peroxidase (HRP). Hydroquinone is oxidized into benzoquinone by the HRP/H2O2 catalytic system. In turn, benzoquinone is electroreduced into hydroquinone at the electrode. The catalytic reduction current is related to HRP amount immobilized on the surface, which itself is related to miRNA.DNA surface density on the electrode. This architecture, compared to classical optical detection, lowers the detection limit down to 10 fM. Two miRNAs were studied: miR-141 (a prostate biomarker) and miR-29b-1 (a lung cancer biomarker). PMID:24973539

  13. Electrochemical immunosensor for botulinum neurotoxin type-E using covalently ordered graphene nanosheets modified electrodes and gold nanoparticles-enzyme conjugate.

    PubMed

    Narayanan, J; Sharma, Mukesh K; Ponmariappan, S; Sarita; Shaik, Mahabul; Upadhyay, Sanjay

    2015-07-15

    In this work, a novel electrochemical immunosensor was developed for the detection of botulinum neurotoxin-E (BoNT/E). This method relied on graphene nanosheets-aryldiazonium salt modified glassy carbon electrodes (GCE) as sensing platform and enzyme induced silver nanoparticles (AgNPs) deposited on gold nanoparticles (AuNPs) as signal amplifier. Herein, a GCE was electrografted with mixed monolayer of phenyl and aminophenyl (Ph-PhNH2/GCE) by diazotization reaction. Further, graphene nanosheets (GNS) were covalently attached on electrode surface (GNS/Ph-PhNH2/GCE). Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were employed to characterize synthesized graphene oxide and modified electrode surfaces. In the sandwich immunoassay format, the sensitivity was amplified using rabbit anti-mouse IgG-alkaline phosphatase (RαMIgG-ALP) functionalized with gold nanoparticles (RαMIgG-ALP/AuNPs). In order to study the immunosensing performance of GNS/Ph-PhNH2/GCE, first the capturing antibody (rabbit-anti BoNT/E antibody) was covalently immobilized via EDC/NHS chemistry. Further, the electrode was sequentially subjected to sample containing spiked BoNT/E, revealing antibody (mouse-anti BoNT/E) followed by RαMIgG-ALP/AuNPs. 3-indoxyl phosphate (3-IP) was used as substrate which finally reduces the silver ions. The deposited AgNPs on electrode surface were determined by linear sweep voltammetry (LSV). The developed electrochemical immunosensor could detect BoNT/E with linear range from 10pg/ml to 10ng/ml with the minimum detection limit of 5.0pg/ml and total analysis time of 65min. In addition, the immunosensor was successfully evaluated against food samples (orange juice and milk). PMID:25754919

  14. Electrochemical sensors using gold submicron particles modified electrodes based on calcium complexes formed with alizarin red S for determination of Ca(2+) in isolated rat heart mitochondria.

    PubMed

    Yang, Jin-Xiang; He, Yan-Bin; Lai, Li-Na; Li, Jun-Bo; Song, Xiao-Liang

    2015-04-15

    A simple glassy carbon electrode (GCE) modified with gold submicron particles (AuSPs), characterized by a mean diameter of about0.15-0.20μm has been developed. Herein, the complexation reaction of Ca(2+) with alizarin red S (ARS), in 0.1M KOH, has been followed by electrochemical methods using the modified electrode which is able to catalyze the electro-reduction of ARS. When the stoichiometry ratio of Ca(2+) and ARS is 1:2, a new reduction peak at a higher negative potential of -0.975V appeared, and the peak of ARS at -0.815V disappeared. The peak current of ARS in alkaline solution is proportional to the concentration of Ca(2+) in the range 6.0×10(-7)-1.2×10(-4)M with a limit of detection (LOD) of 5.1×10(-7)M. Furthermore, the complex site of Ca(2+) with ARS was analysized by the experimental UV-vis and infrared spectrums and those calculated electronic and vibrational spectroscopies with density functional theory (DFT). The good accordance between theoretical and experimental data confirms that chelation of calcium ion preferentially occurs at the deprotonated catechol site. Then, we implemented an electrochemical assay for the investigation of Ca(2+) in preparations of isolated rat heart mitochondria, which demonstrates the submicron particles modified electrode is a simple and rapid sensor for determining the Ca(2+) in the biological samples. PMID:25497981

  15. 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

  16. An electrochemical biosensor based on nanoporous stainless steel modified by gold and palladium nanoparticles for simultaneous determination of levodopa and uric acid.

    PubMed

    Rezaei, Behzad; Shams-Ghahfarokhi, Leila; Havakeshian, Elaheh; Ensafi, Ali A

    2016-09-01

    In this paper, an electrochemical biosensor based on gold and palladium nano particles-modified nanoporous stainless steel (Au-Pd/NPSS) electrode has been introduced for the simultaneous determination of levodopa (LD) and uric acid (UA). To prepare the electrode, the stainless steel was anodized to fabricate NPSS and then Cu was electrodeposited onto the nanoporous steel by applying the multiple step potential. Finally, the electrode was immersed into a gold and palladium precursor's solution by the atomic ratio of 9:1 to form Au-Pd/NPSS through the galvanic replacement reaction. Morphological aspects, structural properties and the electroanalytical behavior of the Au-Pd/NPSS electrode were studied using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and voltammetric techniques. Also, differential pulse voltammetry (DPV) was used for the simultaneous determination of LD and UA. According to results, the surface of Au-Pd/NPSS electrode contained Au and Pd nanoparticles with an average diameter of 75nm. The electrode acted better than Au/NPSS and Pd/NPSS electrodes for the simultaneous determination of LD and UA, with the peak separation potential of about 220mV. Also, the calibration plot for LD was in two linear concentration ranges of 5.0-10.0 and 10.0-55.0μmolL(-1) and for UA, it was in the range of 100-1200μmolL(-1). The detection limit for LD and UA was 0.2 and 15μmolL(-1), respectively. The modified electrode had a good performance for LD and UA detection in urine, blood serum and levodopa C-Forte tablet. PMID:27343576

  17. Amplified electrochemical hydrogen peroxide reduction based on hemin/G-quadruplex DNAzyme as electrocatalyst at gold particles modified heated copper disk electrode.

    PubMed

    Wu, Shao-Hua; Tang, You; Chen, Liang; Ma, Xian-Gui; Tian, Song-Mao; Sun, Jian-Jun

    2015-11-15

    A new gold particles modified heated copper disk electrode (Au-HCuDE) with direct current was fabricated. The hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme (HRP-DNAzyme) was self-assembled on the heated electrode and resulted in a new biosensor denoted as HRP-DNAzyme/Au-HCuDE. By controlling the temperature of the surface of the electrode, the dramatic temperature effect on the electrocatalytic reduction of H2O2 at HRP-DNAzyme/Au-HCuDE sensing platform was demonstrated. This electrocatalytic activity of HRP-DNAzyme was enhanced with electrode temperature elevated. This method was thus preliminarily used to develop an electrochemical biosensor for highly sensitive detection of H2O2. A detection limit of 1.6×10(-7) M could be obtained (S/N=3) with an electrode temperature of 50 °C, which was more than one magnitude lower than that at electrode temperature of 0 °C. This heated electrochemical biosensor shows many merits such as easy fabrication and simple heating equipment, low cost, high thermal stability, and high sensitivity and good reproducibility. PMID:26043314

  18. 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.

  19. 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.

  20. 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.

  1. 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})

  2. 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). PMID:24769451

  3. Electrochemical detection of the disease marker human chitinase-3-like protein 1 by matching antibody-modified gold electrodes as label-free immunosensors.

    PubMed

    Chaocharoen, Wethaka; Suginta, Wipa; Limbut, Warakorn; Ranok, Araya; Numnuam, Apon; Khunkaewla, Panida; Kanatharana, Proespichaya; Thavarungkul, Panote; Schulte, Albert

    2015-02-01

    Tissue inflammation, certain cardiovascular syndromes and the occurrence of some solid tumors are correlated with raised serum concentrations of human chitinase-3-like protein 1 (YKL-40), a mammalian chitinase-like glycoprotein, which has become the subject of current research. Here we report the construction and characterization of an electrochemical platform for label-free immunosensing of YKL-40. Details of the synthesis of YKL-40 and production of anti-YKL-40 immunoglobulin G (IgG) are provided and cross-reactivity tests presented. Polyclonal anti-YKL-40 IgG was immobilized on gold electrodes and the resulting immunosensors were operated in an electrochemical flow system with capacitive signal generation. The strategy offered a wide linear detection range (0.1μg/L to 1mg/L) with correlation coefficients (R(2)) above 0.99 and good sensitivity (12.28±0.27nF/cm(2) per decade of concentration change). Additionally, the detection limit of 0.07±0.01μg/L was well below that of optical enzyme-linked immunosorbent assays (ELISAs), which makes the proposed methodology a promising alternative for YKL-40 related disease studies. PMID:25203453

  4. 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. PMID:25932794

  5. 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.

  6. 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.

  7. Glassy carbon electrode modified with gold nanoparticles for ractopamine and metaproterenol sensing

    NASA Astrophysics Data System (ADS)

    Duan, Jiahua; He, Dawei; Wang, Wenshuo; Liu, Yongchuan; Wu, Hongpeng; Wang, Yongsheng; Fu, Ming

    2013-06-01

    In this Letter, the gold nanoparticles (AuNPs) were used as an enhanced material for selective detection of ractopamine and metaproterenol with electrochemical methods. The morphology and size of gold nanoparticles were characterized by scanning electron microscopy and absorption spectrum. Meanwhile, the electrical properties of modified glass carbon electrode (GCE) were studied by electrochemical impedance spectroscopy. The electrochemical behaviors of ractopamine and metaproterenol were well explained by PM3 calculated method and cyclic voltammetry. Importantly, the ractopamine and metaproterenol were effectively detected. The detection range has been broadened to (10-9-10-5 M) and the detection time has been shortened to a few minutes.

  8. Electrochemical apparatus comprising modified disposable rectangular cuvette

    SciTech Connect

    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.

  9. 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.

  10. The active site behaviour of electrochemically synthesised gold nanomaterials.

    PubMed

    Plowman, Blake J; O'Mullane, Anthony P; Bhargava, Suresh K

    2011-01-01

    Even though gold is the noblest of metals, a weak chemisorber and is regarded as being quite inert, it demonstrates significant electrocatalytic activity in its nanostructured form. It is demonstrated here that nanostructured and even evaporated thin films of gold are covered with active sites which are responsible for such activity. The identification of these sites is demonstrated with conventional electrochemical techniques such as cyclic voltammetry as well as a large amplitude Fourier transformed alternating current (FT-ac) method under acidic and alkaline conditions. The latter technique is beneficial in determining if an electrode process is either Faradaic or capacitive in nature. The observed behaviour is analogous to that observed for activated gold electrodes whose surfaces have been severely disrupted by cathodic polarisation in the hydrogen evolution region. It is shown that significant electrochemical oxidation responses occur at discrete potential values well below that for the formation of the compact monolayer oxide of bulk gold and are attributed to the facile oxidation of surface active sites. Several electrocatalytic reactions are explored in which the onset potential is determined by the presence of such sites on the surface. Significantly, the facile oxidation of active sites is used to drive the electroless deposition of metals such as platinum, palladium and silver from their aqueous salts on the surface of gold nanostructures. The resultant surface decoration of gold with secondary metal nanoparticles not only indicates regions on the surface which are rich in active sites but also provides a method to form interesting bimetallic surfaces. PMID:22455038

  11. DNA-gold nanoparticles network based electrochemical biosensors for DNA MTase activity.

    PubMed

    Hong, Lu; Wan, Jing; Zhang, Xiaojun; Wang, Guangfeng

    2016-05-15

    In this work, a highly sensitive electrochemical DNA methyltransferase (MTase) activity assay was fabricated with DNA-gold nanoparticles (Au NPs) network as signal amplification unit and an easy assembly method by the linkage of benzenedithiol bridge. By two complementary AuNPs modified single-stranded DNA, DNA-gold nanoparticles network was self-assembled. With the linkage of benzenedithiol bridge, the DNA network structure was immobilized on the surface of gold electrode through the covalent Au-S bond. In the presence of Dam MTase, the special sites of DNA-AuNPs network were methylated and could not be digested by restriction endonuclease Mbo I. Thus the loaded electrochemical indicator Methylene blue (MB) was MB molecules still remained on the DNA-Au NPs network. The electrochemical response depended on the methylated degree, which could be used to detect MTase activity. By the differential pulse voltammetry (DPV), it was demonstrated that a linear relationship between the DPV response and logarithm of Dam concentration ranged from 0.075 to 30U/mL, achieving a low detection limit of 0.02U/mL. The use of benzenedithiol avoided the direct incubation of the solid electrode with the capture DNA probe under complex and harsh conditions. Therefore the immobilization of DNA-AuNPs network was easy to be carried out, which is favorable for the specially high stability and reproducibility of the electrochemical biosensor. PMID:26992515

  12. An electrochemical metalloimmunoassay based on a colloidal gold label.

    PubMed

    Dequaire, M; Degrand, C; Limoges, B

    2000-11-15

    A novel, sensitive electrochemical immunoassay has been developed using a colloidal gold label that, after oxidative gold metal dissolution in an acidic solution, was indirectly determined by anodic stripping voltammetry (ASV) at a single-use carbon-based screen-printed electrode (SPE). The use of disposable electrodes allows for simplified measurement in 35 microL of solution. The method was evaluated for a noncompetitive heterogeneous immunoassay of an immunoglobulin G (IgG) and a concentration as low as 3 x 10(-12) M was determined, which is competitive with colorimetric ELISA or with immunoassays based on fluorescent europium chelate labels. The high performance of the method is related to the sensitive ASV determination of gold(III) at a SPE (detection limit of 5 x 10(-9) M) and to the release of a large number of gold(III) ions from each gold particle anchored on the immunocomplex (e.g., 1.7 x 10(5) gold atoms are theoretically contained in a 18-nm spherical gold particle). PMID:11101226

  13. Rapid microwave-assisted synthesis and electrochemical characterization of gold/carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Hu, Qitu; Gan, Zibao; Zheng, Xiuwen; Lin, Qingfu; Xu, Baofeng; Zhao, Aihua; Zhang, Xu

    2011-05-01

    Hybrid nanostructures composed of gold nanoparticles (NPs) and carbon nanotubes (CNTs) have been prepared by a microwave-assisted method in the mixed solvents of oleylamine and oleic. The morphology, structure and composition of as-obtained Au/CNT composites are characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD). The composites show characteristic plasmon absorption of Au NPs in the Ultraviolet-visual spectrum. Fourier transform infrared spectrum shows the successful introduction of functional groups on the surface of CNTs, which are crucial factors to assist the nucleation in situ of Au NPs on the surface of CNTs. Electrochemical measurements show the enhancement electrochemical response for the gold electrode modified with Au/CNT composites.

  14. Gold nanotip array for ultrasensitive electrochemical sensing and spectroscopic monitoring.

    PubMed

    Jiang, Yueyue; Meng, Fanben; Qi, Dianpeng; Cai, Pingqiang; Yin, Zongyou; Shao, Fangwei; Zhang, Hua; Boey, Freddy; Chen, Xiaodong

    2013-07-01

    A gold nanotip array platform with a combination of ultrasensitive electrochemical sensing and spectroscopic monitoring capability is reported. Adenosine triphosphate is detected down to 1 pM according to the impedance changes in response to aptamer-specific binding. Furthermore, the local molecular information can be monitored at the individual plasmonic nanotips, and hence provide the capability for a better understanding of complex biological processes. PMID:23362212

  15. 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.

  16. Electrochemical analysis of Shewanella oneidensis engineered to bind gold electrodes.

    PubMed

    Kane, Aunica L; Bond, Daniel R; Gralnick, Jeffrey A

    2013-02-15

    Growth in three-electrode electrochemical cells allows quantitative analysis of mechanisms involved in electron flow from dissimilatory metal reducing bacteria to insoluble electron acceptors. In these systems, gold electrodes are a desirable surface to study the electrophysiology of extracellular respiration, yet previous research has shown that certain Shewanella species are unable to form productive biofilms on gold electrodes. To engineer attachment of Shewanella oneidensis to gold, five repeating units of a synthetic gold-binding peptide (5rGBP) were integrated within an Escherichia coli outer membrane protein, LamB, and displayed on the outer surface of S. oneidensis. Expression of LamB-5rGBP increased cellular attachment of S. oneidensis to unpoised gold surfaces but was also associated with the loss of certain outer membrane proteins required for extracellular respiration. Loss of these outer membrane proteins during expression of LamB-5rGBP decreased the rate at which S. oneidensis was able to reduce insoluble iron, riboflavin, and electrodes. Moreover, poising the gold electrode resulted in repulsion of the engineered cells. This study provides a strategy to specifically immobilize bacteria to electrodes while also outlining challenges involved in merging synthetic biology approaches with native cellular pathways and cell surface charge. PMID:23656372

  17. 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

  18. Electrochemical sensing based on gold nanoparticle-decorated halloysite nanotube composites.

    PubMed

    Cao, Hongmei; Sun, Xiumei; Zhang, Yang; Jia, Nengqin

    2012-11-15

    Novel gold nanoparticle-decorated halloysite nanotube (AuNP-HNT) composites were effectively synthesized and then used for electrochemical sensing applications. The AuNP-HNT nanocomposites were characterized by transmission electron microscopy, field emission scanning electron microscopy, zeta potential, and UV-Vis spectroscopy. The AuNP-HNT composite-based modified electrode exhibited high eletrocatalytic activity to the reduction of hydrogen peroxide (H(2)O(2)) with a linear range of 5.0×10(-6) to 2.55×10(-4)M and a detection limit of 1×10(-6)M (signal/noise=3), indicating that it could be used as a novel nonenzymatic electrochemical H(2)O(2) sensor. Furthermore, the Ru(bpy)(3)(2+)/AuNP-HNT/Nafion composite film modified electrode exhibited good electrochemiluminescence activity for determining tripropylamine. PMID:22922384

  19. "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

  20. 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.

  1. 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

  2. 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

  3. Synthesis of Crooked Gold Nanocrystals by Electrochemical Technique

    NASA Astrophysics Data System (ADS)

    Huang, Chien-Jung; Chiu, Pin-Hsiang; Chen, Ming-Da; Meen, Teen-Hang

    2005-07-01

    In this article, we demonstrate the synthesis of crooked gold nanocrystals (CGNCs) by an electrochemical technique using micelle templates formed by two surfactants with different amounts of isopropanol solvent, the primary surfactant being hexadecyltrimethylammonium bromide (C16TABr) and the cosurfactant being tetradodecylammonium bromide (TC12ABr). To investigate the influence of isopropanol solvent on the CGNCs, the amount of isopropanol was varied in the range from 50 to 300 μL. It was found that the aspect ratios (γ) of CGNCs were in the range from 1.06 to 1.46, and the UV--vis optical absorption measurement revealed a pronounced redshift of the surface plasmon band from 532 to 560 nm. The CGNCs were composed of many large gold grains with small gold nuclei, and it was determined that several grains are present within each of the CGNCs using a dark-field transmission electron microscopy (TEM) image. It is suggested that the CGNCs have a polycrystalline structure. The CGNCs have been determined to be pure gold with a face-centered cubic (fcc) structure by electron diffraction (ED) analysis.

  4. Chemically modified flexible strips as electrochemical biosensors.

    PubMed

    Thota, Raju; Ganesh, V

    2014-09-21

    A flexible and disposable strip sensor for non-enzymatic glucose detection is demonstrated in this work. The strips are prepared by using chemical modification processes followed by a simple electroless deposition of copper. Essentially, polyester overhead projector (OHP) transparent films are modified with a monolayer of 3-aminopropyltrimethoxysilane (APTMS) and polyaniline (PANI) conducting polymer. Later, nanostructured copper is deposited onto this modified film. Scanning electron microscope (SEM) and X-ray diffraction (XRD) studies are used for the structural, morphological and crystallinity characterization of the modified films. Electrochemical techniques, namely cyclic voltammetry (CV) and chronoamperometry (CA), are employed for the non-enzymatic detection of glucose. These studies clearly reveal the formation of homogeneous, close-packed spherical Cu particles converged into uniform film that exhibits a good catalytic activity towards the oxidation of glucose. The Cu/PANI/APTMS/OHP sensor displays a remarkable enhancement in the oxidation current density, a very high sensitivity value of 2.8456 mA cm(-2) per mM, and a linear concentration range from 100 μM to 6.5 mM associated with glucose detection. Detection limit is estimated to be 5 μM and the response time of the sensor is determined to be less than 5 s. For comparison, similar studies are performed without PANI, namely Cu/APTMS/OHP films for glucose detection. In this case, a sensitivity value of 2.4457 mA cm(-2) per mM and a linear concentration range of 100 μM-3 mM are estimated. The higher performance characteristics observed in the case of Cu/PANI/APTMS/OHP are attributed to the synergistic effects of the conducting polymer acting as an electron facilitator and the nanostructured Cu films. These disposable, flexible and low-cost strip sensors have also been applied to the detection of glucose in clinical blood serum samples and the results obtained agree very well with the actual glucose

  5. 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

  6. 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

  7. Three-dimensional mesoporous gold film to enhance the sensitivity of electrochemical detection

    NASA Astrophysics Data System (ADS)

    El-Said, Waleed Ahmed; Kim, Tae-Hyung; Kim, Hyuncheol; Choi, Jeong-Woo

    2010-11-01

    Cell-cell and cell-extracellular matrix (ECM) adhesion are fundamental and important in the development of a cell-based chip. In this study, a novel, simple, rapid, and one-step technique was developed for the fabrication of a uniform three-dimensional mesoporous gold thin film (MPGF) onto a gold (Au) coated glass plate based on an electrochemical deposition method. Scanning electron microscopy images demonstrated that the resulting MPGF electrode had uniformly distributed pores with diameters of about 20 nm. The cyclic voltammetric behavior of [Fe(CN)6]4 - /3 - coupled onto MPGF and Au electrodes demonstrated that the MPGF electrode had a higher electrocatalytic sensitivity and reversibility than the bare Au electrode. The Arg-Gly-Asp (RGD) sequence containing the peptide was immobilized on the MPGF and bare Au substrates. HeLa cancer cells were then cultured on the RGD peptide layer. The successful immobilization of the peptide and cells was confirmed by atomic force microscopy. The cell proliferation and viability were evaluated by cyclic voltammetry and Trypan blue dyeing assay. These results indicated that the RGD/MPGF modified electrodes showed an electrochemical sensitivity in the detection of cancer cells which is approximately three times higher, especially at low cell density, than RGD/Au electrodes. This much improved sensitivity of the MPGF modified electrode demonstrates the potential for the fabrication of a highly sensitive and low-cost cell-based chip for rapid cancer detection.

  8. Modified gold surfaces by 6-(ferrocenyl)hexanethiol/dendrimer/gold nanoparticles as a platform for the mediated biosensing applications.

    PubMed

    Karadag, Murat; Geyik, Caner; Demirkol, Dilek Odaci; Ertas, F Nil; Timur, Suna

    2013-03-01

    An electrochemical biosensor mediated by using 6-(Ferrocenyl) hexanethiol (FcSH) was fabricated by construction of gold nanoparticles (AuNPs) on the surface of polyamidoamine dendrimer (PAMAM) modified gold electrode. Glucose oxidase (GOx) was used as a model enzyme and was immobilized onto the gold surface forming a self assembled monolayer via FcSH and cysteamine. Cyclic voltammetry and amperometry were used for the characterization of electrochemical response towards glucose substrate. Following the optimization of medium pH, enzyme loading, AuNP and FcSH amount, the linear range for the glucose was studied and found as 1.0 to 5.0mM with the detection limit (LOD) of 0.6mM according to S/N=3. Finally, the proposed Au/AuNP/(FcSH+Cyst)/PAMAM/GOx biosensor was successfully applied for the glucose analysis in beverages, and the results were compared with those obtained by HPLC. PMID:25427467

  9. Scanning Electrochemical Microscopy of DNA Monolayers Modified with Nile Blue

    PubMed Central

    Gorodetsky, Alon A.; Hammond, William J.; Hill, Michael G.; Slowinski, Krzysztof; Barton, Jacqueline K.

    2009-01-01

    Scanning electrochemical microscopy (SECM) is used to probe long-range charge transport (CT) through DNA monolayers containing the redox-active Nile Blue (NB) intercalator covalently affixed at a specific location in the DNA film. At substrate potentials negative of the formal potential of covalently attached NB, the electrocatalytic reduction of Fe(CN)63− generated at the SECM tip is observed only when NB is located at the DNA/solution interface; for DNA films containing NB in close proximity to the DNA/electrode interface, the electrocatalytic effect is absent. This behavior is consistent with both rapid DNA-mediated CT between the NB intercalator and the gold electrode as well as a rate-limiting electron transfer between NB and the solution phase Fe(CN)63−. The DNA-mediated nature of the catalytic cycle is confirmed through sequence-specific and localized detection of attomoles of TATA-binding protein, a transcription factor that severely distorts DNA upon binding. Importantly, the strategy outlined here is general and allows for the local investigation of the surface characteristics of DNA monolayers both in the absence and in the presence of DNA binding proteins. These experiments highlight the utility of DNA-modified electrodes as versatile platforms for SECM detection schemes that take advantage of CT mediated by the DNA base pair stack. PMID:19053641

  10. 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.

  11. Copper-modified gold electrode specific for monosaccharide detection Use in amperometric determination of phenylmercury based on invertase enzyme inhibition.

    PubMed

    Mohammadi, H; Amine, A; El Rhazi, M; Brett, C M A

    2004-04-19

    The electrochemical oxidation of mono- and disaccharides at various copper-modified electrodes is reported: glassy carbon modified at open circuit or by electrochemical deposition of copper, gold modified by electrochemical deposition, and at bulk copper electrodes. A comparative study of these four electrodes was made by linear sweep voltammetry and amperometry. The maximum oxidation peak separation between disaccharides and monosaccharides is about 200mV. After optimization, amperometric determination of monosaccharides was done at +0.30 versus Ag/AgCl in 0.15M NaOH at the copper-modified gold electrode. Using the developed method, the enzymatic activities of invertase and beta-galactosidase were determined through their reaction with sucrose and lactose, respectively. Validation was carried out by a spectrophotometric method based on 3,5-dinitrosalicylic acid, and it was shown that the proposed electrochemical method is more sensitive. The analytical utility of the copper-modified gold electrode was tested for the determination of organic mercury. Addition of phenylmercury standards to the invertase solution caused a decrease in the enzyme activity, and allowed the determination of phenylmercury in pharmaceutical samples. The concentration has been determined in the 10-55ngml(-1) range. PMID:18969385

  12. 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.

  13. [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

  14. 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

  15. 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

  16. 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.

  17. 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

  18. 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. PMID:24840469

  19. Few-layer graphene sheets with embedded gold nanoparticles for electrochemical analysis of adenine

    PubMed Central

    Biris, Alexandru R; Pruneanu, Stela; Pogacean, Florina; Lazar, Mihaela D; Borodi, Gheorghe; Ardelean, Stefania; Dervishi, Enkeleda; Watanabe, Fumiya; Biris, Alexandru S

    2013-01-01

    This work describes the synthesis of few-layer graphene sheets embedded with various amounts of gold nanoparticles (Gr-Au-x) over an Aux/MgO catalytic system (where × = 1, 2, or 3 wt%). The sheet-like morphology of the Gr-Au-x nanostructures was confirmed by transmission electron microscopy and high resolution transmission electron microscopy, which also demonstrated that the number of layers within the sheets varied from two to seven. The sample with the highest percentage of gold nanoparticles embedded within the graphitic layers (Gr-Au-3) showed the highest degree of crystallinity. This distinct feature, along with the large number of edge-planes seen in high resolution transmission electron microscopic images, has a crucial effect on the electrocatalytic properties of this material. The reaction yields (40%–50%) and the final purity (96%–98%) of the Gr-Au-x composites were obtained by thermogravimetric analysis. The Gr-Au-x composites were used to modify platinum substrates and subsequently to detect adenine, one of the DNA bases. For the bare electrode, no oxidation signal was recorded. In contrast, all of the modified electrodes showed a strong electrocatalytic effect, and a clear peak for adenine oxidation was recorded at approximately +1.05 V. The highest increase in the electrochemical signal was obtained using a platinum/Gr-Au-3-modified electrode. In addition, this modified electrode had an exchange current density (I0, obtained from the Tafel plot) one order of magnitude higher than that of the bare platinum electrode, which also confirmed that the transfer of electrons took place more readily at the Gr-Au-3-modified electrode. PMID:23610521

  20. 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.

  1. Specific and selective electrochemical immunoassay for Pseudomonas aeruginosa based on pectin-gold nano composite.

    PubMed

    Krithiga, N; Viswanath, K Balaji; Vasantha, V S; Jayachitra, A

    2016-05-15

    In this report, we have successfully fabricated an immunosensor for detection of Pseudomonas aeruginosa in water. The monoclonal antibody was immobilized on the surface modified with CCLP (Calcium Cross-Linked Pectin)-Au NPs (gold nanoparticles)/Glassy Carbon Electrode. The building of the immunosensor was evaluated in each step by cyclic voltammetry (CV) and impedance spectroscopy (EIS). The electrochemical detection was done based on the anti rabbit IgG HRP (Horseradish Peroxidase) which binds to the immune complex and the response was observed using Hydro Quininone (HQ) and Hydrogen peroxide (H2O2) in PB (Phosphate Buffer) electrolyte. From the results, the sensitivity range is from 10(1) to 10(7)CFU/ml and LOD is calculated as 9×10(2)CFU/ml. The developed immunosensor also have high selectivity, stability, reproducibility and reusability. PMID:26703990

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

    PubMed Central

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

    2015-01-01

    An electrochemical method for annealing the pore sizes of nanoporous gold is reported. The pore sizes of nanoporous gold 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 nanoporous gold 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 nanoporous gold surface when subjected to annealing in different electrolytes as well as the subsequent structural changes in nanoporous gold are also reported. The effect of the annealing process on the application of nanoporous gold as a substrate for glucose electro-oxidation is briefly examined. PMID:25649027

  3. Gold nanoparticles directly modified glassy carbon electrode for non-enzymatic detection of glucose

    NASA Astrophysics Data System (ADS)

    Chang, Gang; Shu, Honghui; Ji, Kai; Oyama, Munetaka; Liu, Xiong; He, Yunbin

    2014-01-01

    This work describes controllable preparation of gold nanoparticles on glassy carbon electrodes by using the seed mediated growth method, which contains two steps, namely, nanoseeds attachment and nanocrystals growth. The size and the dispersion of gold nanoparticles grown on glassy carbon electrodes could be easily tuned through the growth time based on results of field-emission scanning electron microscopy. Excellent electrochemical catalytic characteristics for glucose oxidation were observed for the gold nanoparticles modified glassy carbon electrodes (AuNPs/GC), resulting from the extended active surface area provided by the dense gold nanoparticles attached. It exhibited a wide linear range from 0.1 mM to 25 mM with the sensitivity of 87.5 μA cm-2 mM-1 and low detection limit down to 0.05 mM for the sensing of glucose. The common interfering species such as chloride ion, ascorbic acid, uric acid and 4-acetamidophenol were verified having no interference effect on the detection of glucose. It is demonstrated that the seed mediated method is one of the facile approaches for fabricating Au nanoparticles modified substrates, which could work as one kind of promising electrode materials for the glucose nonenzymatic sensing.

  4. Electrochromic properties of WO3 thin film onto gold nanoparticles modified indium tin oxide electrodes

    NASA Astrophysics Data System (ADS)

    Deng, Jiajia; Gu, Ming; Di, Junwei

    2011-04-01

    Gold nanoparticles (GNPs) thin films, electrochemically deposited from hydrogen tetrachloroaurate onto transparent indium tin oxide (ITO) thin film coated glass, have different color prepared by variation of the deposition condition. The color of GNP film can vary from pale red to blue due to different particle size and their interaction. The characteristic of GNPs modified ITO electrodes was studied by UV-vis spectroscopy, scanning electron microscope (SEM) images and cyclic voltammetry. WO3 thin films were fabricated by sol-gel method onto the surface of GNPs modified electrode to form the WO3/GNPs composite films. The electrochromic properties of WO3/GNPs composite modified ITO electrode were investigated by UV-vis spectroscopy and cyclic voltammetry. It was found that the electrochromic performance of WO3/GNPs composite films was improved in comparison with a single component system of WO3.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. Creation of a gold nanoparticle based electrochemical assay for the detection of inhibitors of bacterial cytochrome bd oxidases.

    PubMed

    Fournier, Eugénie; Nikolaev, Anton; Nasiri, Hamid R; Hoeser, Jo; Friedrich, Thorsten; Hellwig, Petra; Melin, Frederic

    2016-10-01

    Cytochrome bd oxidases are membrane proteins expressed by bacteria including a number of pathogens, which make them an attractive target for the discovery of new antibiotics. An electrochemical assay is developed to study the activity of these proteins and inhibition by quinone binding site tool compounds. The setup relies on their immobilization at electrodes specifically modified with gold nanoparticles, which allows achieving a direct electron transfer to/from the heme cofactors of this large enzyme. After optimization of the protein coverages, the assay shows at pH7 a good reproducibility and readout stability over time, and it is thus suitable for further screening of small molecule collections. PMID:27314676

  10. 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

  11. 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

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

    PubMed

    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 10(6) 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  14. 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. PMID:26893086

  15. 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.

  16. 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.

  17. 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.

  18. Electrochemical Corrosion of Stainless Steel in Thiosulfate Solutions Relevant to Gold Leaching

    NASA Astrophysics Data System (ADS)

    Choudhary, Lokesh; Wang, Wei; Alfantazi, Akram

    2016-01-01

    This study aims to characterize the electrochemical corrosion behavior of stainless steel in the ammoniacal thiosulfate gold leaching solutions. Electrochemical corrosion response was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy, while the semi-conductive properties and the chemical composition of the surface film were characterized using Mott-Schottky analysis and X-ray photoelectron spectroscopy, respectively. The morphology of the corroded specimens was analyzed using scanning electron microscopy. The stainless steel 316L showed no signs of pitting in the ammoniacal thiosulfate solutions.

  19. Gold Binding by Native and Chemically Modified Hops Biomasses

    DOE PAGESBeta

    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

  20. 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.

  1. 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.

  2. A high-performance hydrazine electrochemical sensor based on gold nanoparticles/single-walled carbon nanohorns composite film

    NASA Astrophysics Data System (ADS)

    Zhao, Shuang; Wang, Liangliang; Wang, Tingting; Han, Qinghua; Xu, Shukun

    2016-04-01

    A novel electrochemical sensor was developed by electrodepositing gold nanoparticles on the single-walled carbon nanohorns modified glassy carbon electrode. We used the prepared sensor to determine hydrazine for the first time. The results show that the modified electrode has good electrocatalytic activity toward the oxidation of hydrazine. Under the optimized conditions, two wide linear segments were observed between the catalytic currents and the concentration of hydrazine within the range of 0.005-3.345 mM with a detection limit of 1.1 μM (s/n = 3). The diffusion coefficient of hydrazine was also estimated using chronoamperometry. Additionally, the sensor showed excellent sensitivity, selectivity, and reproducibility properties.

  3. 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.

  4. Electrochemical Immunosensor Based on Polythionine/Gold Nanoparticles for the Determination of Aflatoxin B1

    PubMed Central

    Owino, Joseph H.O.; Arotiba, Omotayo A.; Hendricks, Nicolette; Songa, Everlyne A.; Jahed, Nazeem; Waryo, Tesfaye T.; Ngece, Rachel F.; Baker, Priscilla G.L.; Iwuoha, Emmanuel I.

    2008-01-01

    An aflatoxin B1 (AFB1) electrochemical immunosensor was developed by the immobilisation of aflatoxin B1-bovine serum albumin (AFB1-BSA) conjugate on a polythionine (PTH)/gold nanoparticles (AuNP)-modified glassy carbon electrode (GCE). The surface of the AFB1-BSA conjugate was covered with horseradish peroxidase (HRP), in order to prevent non-specific binding of the immunosensors with ions in the test solution. The AFB1 immunosensor exhibited a quasi-reversible electrochemistry as indicated by a cyclic voltammetric (CV) peak separation (ΔEp) value of 62 mV. The experimental procedure for the detection of AFB1 involved the setting up of a competition between free AFB1 and the immobilised AFB1-BSA conjugate for the binding sites of free anti-aflatoxin B1 (anti-AFB1) antibody. The immunosensor's differential pulse voltammetry (DPV) responses (peak currents) decreased as the concentration of free AFB1 increased within a dynamic linear range (DLR) of 0.6 - 2.4 ng/mL AFB1 and a limit of detection (LOD) of 0.07 ng/mL AFB1. This immunosensing procedure eliminates the need for enzyme-labeled secondary antibodies normally used in conventional ELISA–based immunosensors.

  5. Electrochemical study of thiols and disulfides using modified electrodes

    SciTech Connect

    Linders, C.R.; Patriarche, G.J.; Kauffman, J.M.

    1986-01-01

    The electrochemical oxidative behavior of cysteine and several disulfides, such as cysteine, lipoic acid and disulfiram, have been investigated using a carbon paste (EPC) and a modified carbon paste (EPCM) electrode. The study has permitted the differentiation of the oxidative behavior of the thiol and of the disulfides. Modification of the carbon paste, by incorporating cobalt(II) phthalocyanine, offers interesting properties due to the electrocatalytic capability of the electrode. Using these types of electrodes the different molecules have been quantitatively determined at concentrations as low as 2.10/sup -7/ M. 14 references, 2 figures, 1 table.

  6. 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

  7. 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.

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

    PubMed

    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

  9. 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

  10. 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. PMID:26592594

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. A ω-mercaptoundecylphosphonic acid chemically modified gold electrode for uranium determination in waters in presence of organic matter.

    PubMed

    Merli, Daniele; Protti, Stefano; Labò, Matteo; Pesavento, Maria; Profumo, Antonella

    2016-05-01

    A chemically modified electrode (CME) on a gold surface assembled with a ω-phosphonic acid terminated thiol was investigated for its capability to complex uranyl ions. The electrode, characterized by electrochemical techniques, demonstrated to be effective for the determination of uranyl at sub-μgL(-1) level by differential pulse adsorptive stripping voltammetry (DPAdSV) in environmental waters, also in presence of humic matter and other potential chelating agents. The accuracy of the measurements was investigated employing as model probes ligands of different complexing capability (humic acids and EDTA). PMID:26946018

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

    PubMed

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

    2013-05-31

    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. PMID:23619092

  19. 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

  20. 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.

  1. 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

  2. Electron transport in two-dimensional arrays of gold nanocrystals investigated by scanning electrochemical microscopy.

    PubMed

    Liljeroth, Peter; Vanmaekelbergh, Daniël; Ruiz, Virginia; Kontturi, Kyösti; Jiang, Hua; Kauppinen, Esko; Quinn, Bernadette M

    2004-06-01

    This article reports the use of the scanning electrochemical microscope (SECM) to investigate the electronic properties of Langmuir monolayers of alkane thiol protected gold nanocrystals (NCs). A substantial increase in monolayer conductivity upon mechanical compression of the Au NC monolayer is reported for the first time. This may be the room temperature signature of the insulator to metal transition previously reported for comparable silver NC monolayers. Factors influencing the conductivity of the monolayer NC array are discussed. PMID:15174884

  3. Passivation of pinholes in octadecanethiol monolayers on gold electrodes by electrochemical polymerization of phenol

    SciTech Connect

    Finklea, H.O.; Snider, D.A.; Fedyk, J. )

    1990-02-01

    An organized monolayer of octadecanethiol on a gold electrode strongly inhibits faradaic reactions except at pinholes in the monolayer. For simple outer-sphere redox couples, the monolayer-coated electrode behaves like a microelectrode array, with pinholes acting as the microelectrodes. The average size and separation of the pinholes can be estimated by fitting the experimental cyclic voltammograms with simulated voltammograms for a microarray electrode. The pinholes are selectively and permanently passivated by electrochemical polymerization of phenol in dilute sulfuric acid.

  4. Electrochemical determination of mesotrione at organoclay modified glassy carbon electrodes.

    PubMed

    Kamga Wagheu, Josephine; Forano, Claude; Besse-Hoggan, Pascale; Tonle, Ignas K; Ngameni, Emmanuel; Mousty, Christine

    2013-01-15

    A natural Cameroonian smectite-type clay (SaNa) was exchanged with cationic surfactants, namely cetyltrimethylammonium (CTA) and didodecyldimethyl ammonium (DDA) modifying its physico-chemical properties. The resulting organoclays that have higher adsorption capacity for mesotrione than the pristine SaNa clay, have been used as modifiers of glassy carbon electrode for the electrochemical detection of this herbicide by square wave voltammetry. The stripping performances of SaNa, SaCTA and SaDDA modified electrodes were therefore evaluated and the experimental parameters were optimized. SaDDA gives the best results in deoxygenated acetate buffer solution (pH 6.0) after 2 min accumulation under open circuit conditions. Under optimal conditions, the reduction current is proportional to mesotrione concentration in the range from 0.25 to 2.5 μM with a detection limit of 0.26 μM. The fabricated electrode was also applied for the commercial formulation CALLISTO, used in European maize market. PMID:23200396

  5. 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. PMID:23117146

  6. 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.

  7. 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...

  8. Hg(2+) detection using a disposable and miniaturized screen-printed electrode modified with nanocomposite carbon black and gold nanoparticles.

    PubMed

    Cinti, Stefano; Santella, Francesco; Moscone, Danila; Arduini, Fabiana

    2016-05-01

    A miniaturized screen-printed electrode (SPE) modified with a carbon black-gold nanoparticle (CBNP-AuNP) nanocomposite has been developed as an electrochemical sensor for the detection of inorganic mercury ions (Hg(2+)). The working electrode surface has been modified with nanocomposite constituted of CBNPs and AuNPs by an easy drop casting procedure that makes this approach extendible to an automatable mass production of modified SPEs. Square wave anodic stripping voltammetry (SWASV) was adopted to perform Hg(2+) detection, revealing satisfactory sensitivity and detection limit, equal to 14 μA ppb(-1) cm(-2) and 3 ppb, respectively. The applicability of the CBNP-AuNP-SPE for the determination of inorganic mercury has been assessed in river water by a simple filtration and acidification of the sample as well as in soil by means of a facile acidic extraction procedure assisted by ultrasound. PMID:26803751

  9. 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.

  10. 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

  11. Ionic liquid of a gold nanocluster: a versatile matrix for electrochemical biosensors.

    PubMed

    Kwak, Kyuju; Kumar, S Senthil; Pyo, Kyunglim; Lee, Dongil

    2014-01-28

    Ionic liquids are room-temperature molten salts that are increasingly used in electrochemical devices, such as batteries, fuel cells, and sensors, where their intrinsic ionic conductivity is exploited. Here we demonstrate that combining anionic, redox-active Au25 clusters with imidazolium cations leads to a stable ionic liquid possessing both ionic and electronic conductivity. The Au25 ionic liquid was found to act as a versatile matrix for amperometric enzyme biosensors toward the detection of glucose. Enzyme electrodes prepared by incorporating glucose oxidase in the Au25 ionic liquid show high electrocatalytic activity and substrate affinity. Au25 clusters in the electrode were found to act as effective redox mediators as well as electronic conductors determining the detection sensitivity. With the unique electrochemical properties and almost unlimited structural tunability, the ionic liquids of quantum-sized gold clusters may serve as versatile matrices for a variety of electrochemical biosensors. PMID:24350837

  12. Ultrasensitive electrochemical immunosensor employing glucose oxidase catalyzed deposition of gold nanoparticles for signal amplification.

    PubMed

    Zhang, Jie; Pearce, Mark C; Ting, Boon Ping; Ying, Jackie Y

    2011-09-15

    This paper describes a novel enzymatic amplification strategy for ultrasensitive electrochemical immunosensing. This approach utilizes glucose oxidase for the enzymatic deposition of gold nanoparticles onto an indium tin oxide (ITO) electrode surface using a novel gold developer solution consisting of 20 mM of glucose, 20 mM of NaSCN, 0.5 M of p-benzoquinone (PBQ) and 1 mM of AuCl(4)(-) dissolved in 0.1 M of pH 7.5 phosphate buffer solution. The amount of gold deposited was quantified electrochemically by monitoring the reduction of gold oxide in an aqueous solution of 0.5 M of H(2)SO(4), which was correlated to the amount of antigens in the solution. The effectiveness of this strategy was demonstrated experimentally through the construction of an immunosensor for the detection of mouse IgG using a sandwich immunoassay in a linear dynamic range of 5 pg/ml to 50 ng/ml. A good mean apparent recovery in the range of 88-102% was obtained over the entire linear dynamic range of the sensor response in the serum samples. This suggested that the immunosensor would be useful for the testing of proteins in real clinical samples. PMID:21782410

  13. Hydrogen peroxide biosensor based on gold nanoparticles/thionine/gold nanoparticles/multi-walled carbon nanotubes-chitosans composite film-modified electrode

    NASA Astrophysics Data System (ADS)

    Li, Shenfeng; Zhu, Xiaoying; Zhang, Wei; Xie, Guoming; Feng, Wenli

    2012-01-01

    In this paper, an amperometric electrochemical biosensor for the detection of hydrogen peroxide (H2O2), based on gold nanoparticles (GNPs)/thionine (Thi)/GNPs/multi-walled carbon nanotubes (MWCNTs)-chitosans (Chits) composite film was developed. MWCNTs-Chits homogeneous composite was first dispersed in acetic acid solution and then the GNPs were in situ synthesized at the composite. The mixture was dripped on the glassy carbon electrode (GCE) and then the Thi was deposited by electropolymerization by Au-S or Au-N covalent bond effect and electrostatic adsorption effect as an electron transfer mediator. Finally, the mixture of GNPs and horseradish peroxidase (HRP) was assembled onto the modified electrode by covalent bond. The electrochemical behavior of the modified electrode was investigated by scanning electron microscope, cyclic voltammetry and chronoamperometry. This study introduces the in situ-synthesized GNPs on the other surface of the modified materials in H2O2 detection. The linear response range of the biosensor to H2O2 concentration was from 5 × 10-7 mol L-1 to 1.5 × 10-3 mol L-1 with a detection limit of 3.75 × 10-8 mol L-1 (based on S/N = 3).

  14. Electrochemical fabrication and evaluation of highly sensitive nanorod-modified electrodes for a biotin/avidin system.

    PubMed

    Lee, Seung-Jun; Anandan, Venkataramani; Zhang, Guigen

    2008-02-28

    Bioaffinity sensors need to be rapid, specific, and highly sensitive. To realize these features, electrodes that can elicit high electrochemical performance are necessary. In this study, we developed nanorod array electrode and performed cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments to study the interfacial properties of the nanorod array electrode with Fe(CN)(6)(3-/4-) as the redox molecules. Results showed that both the CV and EIS measurements captured very well the resistive and capacitive changes due to the adsorption of functionalizing molecules and the coupling between avidin and biotin. The EIS measurements were more sensitive in discriminating small changes caused by the surface adsorption of various molecules. The use of avidin-functionalized gold nanorod modified electrodes had led to much increased detection sensitivity along with a detection-limit as low as 1 ng/mL of biotin. PMID:18077147

  15. 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

  16. A Highly Sensitive Oligonucleotide Hybridization Assay for Klebsiella pneumoniae Carbapenemase with the Probes on a Gold Nanoparticles Modified Glassy Carbon Electrode.

    PubMed

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

    2015-01-01

    To develop a new electrochemical DNA biosensor for determination of Klebsiella pneumoniae carbapenemase, a highly sensitive and selective electrochemical biosensor for DNA detection was constructed based on a glassy carbon electrode (GCE) modified with gold nanoparticles (Au-nano). The Au-nano/GCE was characterized by scanning electromicroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The hybridization detection was measured by differential pulse voltammetry using methylene blue as the hybridization indicator. The dynamic range of detection of the sensor for the target DNA sequences was from 1 × 10(-11) to 1 × 10(-8) M, with an LOD of 1 × 10(-12) M. The DNA biosensor had excellent specificity for distinguishing complementary DNA sequence in the presence of non-complementary and mismatched DNA sequence. The Au-nano/GCE showed significant improvement in electrochemical characteristics, and this biosensor was successfully applied for determination of K. pneumoniae. PMID:26651586

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

    PubMed Central

    2014-01-01

    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. PACS 78. 67. Bf; 78.55.-m PMID:24708532

  18. Label-free amperometric immunobiosensor based on a gold colloid and Prussian blue nanocomposite film modified carbon ionic liquid electrode.

    PubMed

    Huang, Ke-Jing; Niu, De-Jun; Sun, Jun-Yong; Zhu, Xiao-Li; Zhu, Jun-Jie

    2010-08-01

    A novel experimental methodology based on a Prussian blue (PB) and gold nanoparticles (AuNPs) modified carbon ionic liquid electrode (CILE) was developed for use in a label-free amperometric immunosensor for the sensitive detection of human immunoglobulin G (HIgG) as a model protein. The CILE was fabricated by using the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate as binder. Controllable electrodeposition of PB on the surface of the CILE and coating with 3-aminopropyl triethylene silane (APS) formed a film with high electronic catalytic activity and large surface area for the assembly of AuNPs and further immobilization of HIgG antibody. The electrochemistry of the formed nanocomposite biofilm was investigated by electrochemical techniques including cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The HIgG concentration was measured through the decrease of amperometric responses in the corresponding specific binding of antigen and antibody. The decreased differential pulse voltammetric values were proportional to the HIgG concentration in two ranges, 0.05-1.25 ng mL(-1) and 1.25-40 ng mL(-1), with a detection limit of 0.001 ng mL(-1) (S/N = 3). This electrochemical immunoassay combined the specificity of the immunological reaction with the sensitivity of the AuNPs, ionic liquid, and PB amplified electrochemical detection and would therefore be valuable for clinical immunoassays. PMID:20577722

  19. 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

  20. 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

  1. MnO2-modified hierarchical graphene fiber electrochemical supercapacitor

    NASA Astrophysics Data System (ADS)

    Chen, Qing; Meng, Yuning; Hu, Chuangang; Zhao, Yang; Shao, Huibo; Chen, Nan; Qu, Liangti

    2014-02-01

    A novel hybrid fiber that MnO2 modified graphene sheets on graphene fiber has been fabricated by direct deposition of MnO2 onto graphene network surrounding graphene fiber (MnO2/G/GF). In this hierarchical structure, the graphene fiber with a sheath of 3D graphene network is coated with MnO2 nanoflowers. The 3D graphene on graphene fibers (G/GF) serves as highly conductive backbones with high surface area for deposition of nanostructured MnO2, which provide the high accessibility of electrolytic ions for shorten diffusion paths. An all-solid-state flexible supercapacitor based on a MnO2/G/GF hybrid fiber structure has been developed on the basis of the intrinsic mechanical flexibility of GF and the unique hierarchical structure. By combination of electric double layer capacitance of graphene network with the pseudocapacitance of MnO2 nanostructures, the all-solid-state fiber supercapacitor shows the much enhanced electrochemical capacitive behaviors with robust tolerance to mechanical deformation, promising for being woven into a textile for wearable electronics.

  2. 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.

  3. Scanning electrochemical microscopy for study of aptamer-thrombin interfacial interactions on gold disk microelectrodes.

    PubMed

    Bai, Huei-Yu; del Campo, F Javier; Tsai, Yu-Chen

    2014-03-01

    A feasibility for the determination of thrombin on gold disk microelectrodes (GDMs) using scanning electrochemical microscopy (SECM) is reported. The assembly process step-by-step of thrombin aptasensor on GDMs is monitored by SECM. SECM analysis reveals the immobilization of thrombin aptamers on GDMs. The interaction between thrombin aptamers and thrombin on GDMs is imaged by SECM with feedback mode using ferrocenemethanol as an electrochemical mediator. The formation of thrombin/thrombin aptamer complex on GDMs results in a decrease in the tip peak current on spatial SECM images. This method is able to linearly and selectively detect thrombin over a linear range from 10(-12) to 10(-5)M with a detection limit of 6.07 fM. PMID:24407695

  4. Graphene encapsulated gold nanoparticle-quantum dot heterostructures and their electrochemical characterization

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Chopra, Nitin

    2015-07-01

    A simple technique for patterning multilayer graphene shell encapsulated gold nanoparticles (GNPs) on the silicon substrate and their further surface decoration with semiconducting quantum dots (QDs) is reported. This leads to the fabrication of a novel silicon electrode decorated with GNP-QD hybrids or heterostructures. The morphology, structure, and composition of the GNPs and GNP-QD heterostructures were evaluated using microscopic and spectroscopic techniques. The heterostructures decorated silicon electrode was also evaluated for the electronic and electrochemical properties. The results showed that the electrical characteristics of the silicon substrate were significantly improved by decorating with GNPs and quantum dots. Furthermore, GNP-QD heterostructure electrode was observed to show significantly increased electrochemical charge transfer activity.

  5. 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. PMID:15308218

  6. Planar Arrays of Nanoporous Gold Nanowires: When Electrochemical Dealloying Meets Nanopatterning.

    PubMed

    Chauvin, Adrien; Delacôte, Cyril; Molina-Luna, Leopoldo; Duerrschnabel, Michael; Boujtita, Mohammed; Thiry, Damien; Du, Ke; Ding, Junjun; Choi, Chang-Hwan; Tessier, Pierre-Yves; El Mel, Abdel-Aziz

    2016-03-16

    Nanoporous materials are of great interest for various technological applications including sensors based on surface-enhanced Raman scattering, catalysis, and biotechnology. Currently, tremendous efforts are dedicated to the development of porous one-dimensional materials to improve the properties of such class of materials. The main drawback of the synthesis approaches reported so far includes (i) the short length of the porous nanowires, which cannot reach the macroscopic scale, and (ii) the poor organization of the nanostructures obtained by the end of the synthesis process. In this work, we report for the first time on a two-step approach allowing creating highly ordered porous gold nanowire arrays with a length up to a few centimeters. This two-step approach consists of the growth of gold/copper alloy nanowires by magnetron cosputtering on a nanograted silicon substrate, serving as a physical template, followed by a selective dissolution of copper by an electrochemical anodic process in diluted sulfuric acid. We demonstrate that the pore size of the nanowires can be tailored between 6 and 21 nm by tuning the dealloying voltage between 0.2 and 0.4 V and the dealloying time within the range of 150-600 s. We further show that the initial gold content (11 to 26 atom %) and the diameter of the gold/copper alloy nanowires (135 to 250 nm) are two important parameters that must carefully be selected to precisely control the porosity of the material. PMID:26926232

  7. Label-free electrochemical aptasensing of the human prostate-specific antigen using gold nanospears.

    PubMed

    Rahi, A; Sattarahmady, N; Heli, H

    2016-08-15

    Gold nanospears were electrodeposited with the assistance of arginine as a soft template and precise selection of experimental parameters. The nanospears were then employed as a transducer to immobilize an aptamer of prostate-specific antigen (PSA) and fabrication of a label-free electrochemical aptasensor. The aptasensor was employed for the detection of PSA with a linear concentration range of 0.125-200ngmL(-1) and a limit of detection of 50pgmL(-1). The aptasensor was successfully applied to detect PSA in blood serum samples of healthy and patient persons. PMID:27260456

  8. 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

  9. 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. PMID:25300210

  10. A miniaturized electrochemical assay for homocysteine using screen-printed electrodes with cytochrome c anchored gold nanoparticles.

    PubMed

    Madasamy, Thangamuthu; Santschi, Christian; Martin, Olivier J F

    2015-09-01

    Determination of homocysteine (HcySH) is highly beneficial in human physiology and pathophysiology for diagnosis and prognosis of cardiovascular diseases (CVD). Unfortunately, the practicability of the existing methodologies for the determination of HcySH is limited in terms of sample requirements, preparation time and instrumentation cost. To overcome these limitations, we have developed a new miniaturized electrochemical assay for HcySH in which cytochrome c (cyt c) immobilized on gold nanoparticle (GNP) modified screen printed carbon electrode (SPE) is employed as a biosensing element. The electrochemical characterization of the biosensor (cyt c-GNP-SPE) shows quasi-reversible redox peaks at the potentials 0 and -0.2 V, confirming the cyt c binding. The methodology of quantification is based on the electrochemical oxidation of HcySH by the Fe(3+)/Fe(2+) crevice of cyt c, observed at a potential of +0.56 V. Using the amperometric technique, the detection limit of HcySH is found to be 0.3 ± 0.025 μM in the linear range between 0.4 μM and 700 μM, with a sensitivity of 3.8 ± 0.12 nA μM(-1) cm(-2). The practical application of the present assay is validated through the measurement of HcySH in blood plasma samples and the selectivity is ensured by eliminating the impact of the common interfering biological substrates using a Nafion membrane. This biosensor shows striking analytical properties of good repeatability, reproducibility (2.85% SD) and high stability (83% of its initial current response after 4 weeks). This work paves the way for cheap, efficient and reliable point-of-care biosensors for screening one of the major causes of deaths both in the developed and developing countries. PMID:26198379

  11. 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

  12. 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

  13. 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.

  14. 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. PMID:25989146

  15. 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

  16. 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

  17. Growth of pentacene on clean and modified gold surfaces

    SciTech Connect

    Kaefer, Daniel; Ruppel, Lars; Witte, Gregor

    2007-02-15

    The growth and evolution of pentacene films on gold substrates have been studied. By combining complementary techniques including scanning tunneling microscopy, atomic force microscopy, scanning electron microscopy, near-edge x-ray-absorption fine structure, and x-ray diffraction, the molecular orientation, crystalline structure, and morphology of the organic films were characterized as a function of film thickness and growth parameters (temperature and rate) for different gold substrates ranging from Au(111) single crystals to polycrystalline gold. Moreover, the influence of precoating the various gold substrates with self-assembled monolayers (SAM's) of organothiols with different chemical terminations has been studied. On bare gold the growth of pentacene films is characterized by a pronounced dewetting while the molecular orientation within the resulting crystalline three-dimensional islands depends distinctly on the roughness and cleanliness of the substrate surface. After completion of the first wetting layer where molecules adopt a planar orientation parallel to the surface the molecules continue to grow in a tilted fashion: on Au(111) the long molecular axis is oriented parallel to the surface while on polycrystalline gold it is upstanding oriented and thus parallels the crystalline orientation of pentacene films grown on SiO{sub 2}. On SAM pretreated gold substrates the formation of a wetting layer is effectively suppressed and pentacene grows in a quasi-layer-by-layer fashion with an upstanding orientation leading to rather smooth films. The latter growth mode is observed independently of the chemical termination of the SAM's and the roughness of the gold substrate. Possible reasons for the different growth mechanism as well as consequences for the assignment of spectroscopic data of thin pentacene film are discussed.

  18. Growth of pentacene on clean and modified gold surfaces

    NASA Astrophysics Data System (ADS)

    Käfer, Daniel; Ruppel, Lars; Witte, Gregor

    2007-02-01

    The growth and evolution of pentacene films on gold substrates have been studied. By combining complementary techniques including scanning tunneling microscopy, atomic force microscopy, scanning electron microscopy, near-edge x-ray-absorption fine structure, and x-ray diffraction, the molecular orientation, crystalline structure, and morphology of the organic films were characterized as a function of film thickness and growth parameters (temperature and rate) for different gold substrates ranging from Au(111) single crystals to polycrystalline gold. Moreover, the influence of precoating the various gold substrates with self-assembled monolayers (SAM’s) of organothiols with different chemical terminations has been studied. On bare gold the growth of pentacene films is characterized by a pronounced dewetting while the molecular orientation within the resulting crystalline three-dimensional islands depends distinctly on the roughness and cleanliness of the substrate surface. After completion of the first wetting layer where molecules adopt a planar orientation parallel to the surface the molecules continue to grow in a tilted fashion: on Au(111) the long molecular axis is oriented parallel to the surface while on polycrystalline gold it is upstanding oriented and thus parallels the crystalline orientation of pentacene films grown on SiO2 . On SAM pretreated gold substrates the formation of a wetting layer is effectively suppressed and pentacene grows in a quasi-layer-by-layer fashion with an upstanding orientation leading to rather smooth films. The latter growth mode is observed independently of the chemical termination of the SAM’s and the roughness of the gold substrate. Possible reasons for the different growth mechanism as well as consequences for the assignment of spectroscopic data of thin pentacene film are discussed.

  19. Effect of nanoporous gold thin film morphology on electrochemical DNA sensing.

    PubMed

    Daggumati, Pallavi; Matharu, Zimple; Seker, Erkin

    2015-08-18

    Advances in materials science and chemistry have led to the development of a wide range of nanostructured materials for building novel electrochemical biosensors. A systematic understanding of the challenges related to electrode morphology involved in designing such sensors is essential for developing effective biosensing tools. In this study, we use nanoporous gold (np-Au) thin film electrode coatings with submicrometer thicknesses, as a model system to investigate the influence of nanostructuring on DNA-methylene blue (MB) interactions and their application to DNA biosensors. The interaction of single- and double-stranded DNA immobilized onto morphologically different np-Au films with MB was electrochemically interrogated via square wave voltammetry (SWV). The electrochemical signal from these electrodes in response to MB decayed progressively with each SWV scan. The decay rate was governed by accessibility of the electrochemically active np-Au surface by the analyte. The optimum frequency for extracting the maximum signal via SWV was influenced by the film morphology, where the optimum frequency was lower for the nanoporous morphology with lower density of molecular access points into the porous coating. Overall, the np-Au electrodes exhibited a 10-fold enhancement in probe grafting density and approximately 10-fold higher electrochemical current upon probe-target hybridization as compared to the planar Au electrodes. The np-Au electrodes enabled sensitive detection with a dynamic range of 10 to 100 nM that shifts by 1 order of magnitude for coarsened np-Au morphology due to increased target penetration into the porous network and hence enhanced hybridization efficiency. These findings provide insight into the influence of nanostructuring on the transport mechanisms of small molecules and nucleic acids, and yield an understanding of diverse sensor performance parameters such as DNA grafting density, hybridization efficiency, sensitivity and dynamic range. PMID

  20. A simple electrochemical platform based on pectin stabilized gold nanoparticles for picomolar detection of biologically toxic amitrole.

    PubMed

    Mani, Veerappan; Devasenathipathy, Rajkumar; Chen, Shen-Ming; Vasantha, V S; Ajmal Ali, M; Huang, Sheng-Tung; Al-Hemaid, Fahad M A

    2015-08-21

    Amitrole is a biologically toxic nonselective herbicide which contaminates surface and ground waters at unprecedented rates. All reported modified electrodes that detect amitrole within sub-micromolar to nanomolar levels were based on the electro-oxidation of amitrole. Herein, we developed a new conceptual idea to detect picomolar concentrations of amitrole based on calcium cross linked pectin stabilized gold nanoparticle (CCLP-GNP) film modified electrode which was prepared by electrodeposition. When the electrochemical behavior of amitrole was investigated at the CCLP-GNP film, the reduction peak current of the GNPs linearly decreased as the concentration of amitrole increases. We have designed a determination platform based on the amitrole dependent decrease of the GNP cathodic peak. The described concept and high sensitivity of square wave voltammetry together facilitate the great sensing ability; as a result the described approach is able to reach a low detection limit of 36 pM which surpassed the detection limits of existing protocols. The sensor presents a good ability to determine amitrole in two linear concentration ranges: (1) 100 pM-1500 pM with a detection limit of 36 pM; (2) 100 nM-1500 nM with a detection limit of 20 nM. The preparation of CCLP-GNPs is simple, rapid and does not require any reducing agents. PMID:26171468

  1. 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.

  2. 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

  3. Amplified electrochemical detection of nucleic acid hybridization via selective preconcentration of unmodified gold nanoparticles.

    PubMed

    Li, Yuan; Tian, Rui; Zheng, Xingwang; Huang, Rongfu

    2016-08-31

    The common drawback of optical methods for rapid detection of nucleic acid by exploiting the differential affinity of single-/double-stranded nucleic acids for unmodified gold nanoparticles (AuNPs) is its relatively low sensitivity. In this article, on the basis of selective preconcentration of AuNPs unprotected by single-stranded DNA (ssDNA) binding, a novel electrochemical strategy for nucleic acid sequence identification assay has been developed. Through detecting the redox signal mediated by AuNPs on 1, 6-hexanedithiol blocked gold electrode, the proposed method is able to ensure substantial signal amplification and a low background current. This strategy is demonstrated for quantitative analysis of the target microRNA (let-7a) in human breast adenocarcinoma cells, and a detection limit of 16 fM is readily achieved with desirable specificity and sensitivity. These results indicate that the selective preconcentration of AuNPs for electrochemical signal readout can offer a promising platform for the detection of specific nucleic acid sequence. PMID:27506344

  4. Gold and Magnetic Nanoparticles-Based Electrochemical Biosensors for Cancer Biomarker Determination.

    PubMed

    Ravalli, Andrea; Marrazza, Giovanna

    2015-05-01

    Detecting cancer at early stage is one of the most important factors associated with the increase of the survival rate of the patients. Cancer biomarkers are able to detect a specific disease early and help to provide treatments before it becomes incurable in later stages. Biomarkers can also be used to determine the recurrence of the disease and to evaluate the follow-up of the patients after a chemio- or radio-therapy and surgery treatments. Electrochemical biosensors are successfully applied for the detection of cancer biomarkers due to their high sensibility, rapid response and low cost. In recent years, the advance in nanotechnology has led to the discovery and the employment of a great number of new materials in nanoscale dimensions. Due to their particular properties, the development of nanostructured biosensors (in particular using gold and magnetic nanoparticles) with high analytical performances increases constantly. In this review recent different strategies for the development of gold and magnetic nanoparticles-based electrochemical biosensors for cancer biomarkers detection were presented. PMID:26504948

  5. 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. PMID:23851924

  6. 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

  7. 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

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

    PubMed Central

    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

  9. 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

  10. 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

  11. 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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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

  14. 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

  15. Electrochemical immunosensor for ultrasensitive detection of microcystin-LR based on graphene-gold nanocomposite/functional conducting polymer/gold nanoparticle/ionic liquid composite film with electrodeposition.

    PubMed

    Ruiyi, Li; Qianfang, Xia; Zaijun, Li; Xiulan, Sun; Junkang, Liu

    2013-06-15

    The study developed an electrochemical immunosensor for ultrasensitive detection of microcystin-LR in water. Graphene oxide and chloroauric acid were alternately electrodeposited on the surface of glassy carbon electrode for 20 cycles to fabricate graphene-gold nanocomposite. The composite was characterized and its apparent heterogeneous electron transfer rate constant (37.28±0.16 cm s (-1)) was estimated by Laviron's model. To immobilize microcystin-LR antibody and improve the electrical conductivity, 2,5-di-(2-thienyl)-1-pyrrole-1-(p-benzoic acid) and chloroauric acid were electrodeposited on the modified electrode in sequence. The ionic liquid was then dropped on the electrode surface and finally microcystin-LR antibody was covalently connected to the conducting polymer film. Experiment showed the electrochemical technique offers control over reaction parameters and excellent repeatability. The graphene-gold nanocomposite and gold nanoparticles enhance electron transfer of Fe(CN)6(3-/4-) to the electrode. The ionic liquid, 1-isobutyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide, improves stability of the antibody. The sensor displays good repeatability (RSD=1.2%), sensitive electrochemical response to microcystin-LR in the range of 1.0×10(-16)-8.0×10(-15)M and detection limit of 3.7×10(-17)M (S/N=3). The peak current change of the sensor after and before incubation with 2.0×10(-15)M of microcystin-LR can retain 95% over a 20-weeks storage period. Proposed method presents remarkable improvement of sensitivity, repeatability and stability when compared to present microcystin-LR sensors. It has been successfully applied to the microcystin-LR determination in water samples with a spiked recovery in the range of 96.3-105.8%. PMID:23434759

  16. Synthesis and characterization of reduced graphene oxide supported gold nanoparticles-poly(pyrrole-co-pyrrolepropylic acid) nanocomposite-based electrochemical biosensor.

    PubMed

    Puri, Nidhi; Niazi, Asad; Srivastava, Avanish K; Rajesh

    2014-10-01

    A conducting poly(pyrrole-co-pyrrolepropylic acid) copolymer nanocomposite film (AuNP-PPy-PPa) incorporating gold nanoparticles (AuNP) was electrochemically grown using a single step procedure over electrochemically reduced graphene oxide (RGO) flakes deposited on a silane-modified indium-tin-oxide (ITO) glass plate. The RGO support base provided excellent mechanical and chemical stability to the polymer nanocomposite matrix. The porous nanostructure of AuNP-PPy-PPa/RGO provided a huge accessible area to disperse AuNP, and it avoided metallic agglomeration within the polymer matrix. The AuNP-PPy-PPa/RGO was characterized by high-resolution transmission electron microscopy (HRTEM), contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and electrochemical techniques. The pendant carboxyl group of AuNP-PPy-PPa/RGO was covalently bonded with myoglobin protein antibody, Ab-Mb, for the construction of a bioelectrode. Electrochemical impedance spectroscopy technique was used for the characterization of the bioelectrode and as an impedimetric biosensor for the detection of human cardiac biomarker, Ag-cMb. The bioelectrode exhibited a linear impedimetric response to Ag-cMb in the range of 10 ng mL(-1) to 1 μg mL(-1), in phosphate-buffered solution (PBS) (pH 7.4, 0.1 M KCl) with a sensitivity of 92.13 Ω cm(2) per decade. PMID:24928550

  17. 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.

  18. 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 10ng/L-1.0µg/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. PMID:26720921

  19. Electrocatalytic oxidation of L-tryptophan using copper hexacyanoferrate film modified gold nanoparticle graphite-wax electrode.

    PubMed

    Prabhu, P; Babu, R Suresh; Narayanan, S Sriman

    2011-10-01

    A novel copper hexacyanoferrate (CuHCF) film modification on cysteamine (Cys)-gold nanoparticle (AuNp) graphite-wax (GW) composite electrode was achieved for the quantitative determination of L-Tryptophan (L-Trp) at a reduced overpotential of 400mV in comparison with the bare Cys-AuNp-GW composite electrode. This modified electrode exhibited a well resolved pair of redox peaks corresponding to the hexacyanoferrate (II/III) reactions of CuHCF film at a formal potential of 0.65 V at a scan rate of 20 mV s(-1). Electrochemical impedance spectroscopy (EIS) studies with the modified electrode showed a very low charge transfer resistance to the electron transfer kinetics of Fe(II)/Fe(III) reactions. A linear range of 8.5×10(-7) M to 1.2×10(-4) M with a detection limit of 1.85×10(-8) M was achieved for the determination of L-Trp with a sensitivity of 0.1198 μA/μM. The influence of ultrasonication on the stability of the CuHCF film modified electrode was investigated. In addition, the CuHCF film modified electrode displayed an excellent reproducibility towards the real time analysis of L-Trp in commercial milk samples. PMID:21621399

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Electrochemical sensing of etoposide using carbon quantum dot modified glassy carbon electrode.

    PubMed

    Nguyen, Hoai Viet; Richtera, Lukas; Moulick, Amitava; Xhaxhiu, Kledi; Kudr, Jiri; Cernei, Natalia; Polanska, Hana; Heger, Zbynek; Masarik, Michal; Kopel, Pavel; Stiborova, Marie; Eckschlager, Tomas; Adam, Vojtech; Kizek, Rene

    2016-04-25

    In this study, enhancement of the electrochemical signals of etoposide (ETO) measured by differential pulse voltammetry (DPV) by modifying a glassy carbon electrode (GCE) with carbon quantum dots (CQDs) is demonstrated. In comparison with a bare GCE, the modified GCE exhibited a higher sensitivity towards electrochemical detection of ETO. The lowest limit of detection was observed to be 5 nM ETO. Furthermore, scanning electron microscopy (SEM), fluorescence microscopy (FM), and electrochemical impedance spectroscopy (EIS) were employed for the further study of the working electrode surface after the modification with CQDs. Finally, the GCE modified with CQDs under optimized conditions was used to analyse real samples of ETO in the prostate cancer cell line PC3. After different incubation times (1, 3, 6, 9, 12, 18 and 24 h), these samples were then prepared prior to electrochemical detection by the GCE modified with CQDs. High performance liquid chromatography with an electrochemical detection method was employed to verify the results from the GCE modified with CQDs. PMID:26882954

  6. 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. PMID:25702990

  7. Gold nanoelectrode ensembles for the simultaneous electrochemical detection of ultratrace arsenic, mercury, and copper.

    PubMed

    Jena, Bikash Kumar; Raj, C Retna

    2008-07-01

    Simultaneous electrochemical detection of As(III), Hg(II), and Cu(II) using a highly sensitive platform based on gold nanoelectrode ensembles (GNEEs) is described. GNEEs were grown by colloidal chemical approach on thiol-functionalized solgel derived three-dimensional silicate network preassembled on a polycrystalline gold (Au) electrode. GNEEs on the silicate network have been characterized by field emission scanning electron microscopy, X-ray diffraction, diffuse reflectance spectroscopy, and electrochemical measurements. Square wave anodic stripping voltammetry (SWASV) has been used for the detection of As(III) and Hg(II) without any interference from Cu(II) at the potentials of 0.06 and 0.53 V, respectively. The GNEE electrode is highly sensitive, and it shows linear response for As(III) and Hg(II) up to 15 ppb. The detection limit (signal-to-noise ratio = 4) of the GNEE electrode toward As(III) and Hg(II) is 0.02 ppb, which is well below the guideline value given by the World Health Organization (WHO). The potential application of the GNEE electrode for the detection of As(III) in a real sample collected from the arsenic-contaminated water in 24 North Parganas, West Bengal is demonstrated. The GNEE electrode has been successfully used for the simultaneous detection of As(III), Cu(II), and Hg(II) at sub-part-per-billion level without any interference for the first time. The nanostructured electrode shows individual voltammetric peaks for As(III), Cu(II), and Hg(II) at 0.06, 0.35, and 0.53 V, respectively. The analytical performance of the GNEE electrode is superior to the existing electrodes. PMID:18444693

  8. 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.

  9. 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.

  10. Single on-chip gold nanowires for electrochemical biosensing of glucose.

    PubMed

    Dawson, Karen; Baudequin, Marine; O'Riordan, Alan

    2011-11-01

    The development of glucose diagnostic devices with low detection limits is of key importance in diabetes-related research. New highly sensitive sensors are required for non-invasive detection of glucose in bodily fluids, other than blood, and an electrochemical sensor based on a single gold nanowire for rapid, reliable and quantitative detection of low glucose concentrations (10 μM-1 mM), is presented in this paper. Single gold nanowire devices are fabricated at silicon chip substrates using a hybrid electron beam-photolithography approach. Critical dimensions of the nanowires are characterised using a combination of scanning electron and atomic force microscopies. Fabricated nanowire devices are characterised by direct electrical probing and cyclic voltammetry to explore functionality. The voltammetric detection of glucose was performed using ferrocene monocarboxylic acid as an oxidising mediator in the presence of glucose oxidase. The biosensor can be applied to the quantification of glucose in the range of 10 μM-100 mM, with an extremely high sensitivity of 7.2 mA mM(-1) cm(-2) and a low detection limit of 3 μM (S/N = 3). The sensor demonstrated high selectivity towards glucose with negligible interference from other oxidizable species including uric acid, ascorbic acid, mannose, fructose, salicylic acid (Aspirin) and acetaminophen (Paracetamol). PMID:21909570

  11. Fabrication and functionalization of PCB gold electrodes suitable for DNA-based electrochemical sensing.

    PubMed

    Salvo, P; Henry, O Y F; Dhaenens, K; Acero Sanchez, J L; Gielen, A; Werne Solnestam, B; Lundeberg, J; O'Sullivan, C K; Vanfleteren, J

    2014-01-01

    The request of high specificity and selectivity sensors suitable for mass production is a constant demand in medical research. For applications in point-of-care diagnostics and therapy, there is a high demand for low cost and rapid sensing platforms. This paper describes the fabrication and functionalization of gold electrodes arrays for the detection of deoxyribonucleic acid (DNA) in printed circuit board (PCB) technology. The process can be implemented to produce efficiently a large number of biosensors. We report an electrolytic plating procedure to fabricate low-density gold microarrays on PCB suitable for electrochemical DNA detection in research fields such as cancer diagnostics or pharmacogenetics, where biosensors are usually targeted to detect a small number of genes. PCB technology allows producing high precision, fast and low cost microelectrodes. The surface of the microarray is functionalized with self-assembled monolayers of mercaptoundodecanoic acid or thiolated DNA. The PCB microarray is tested by cyclic voltammetry in presence of 5 mM of the redox probe K3Fe(CN6) in 0.1 M KCl. The voltammograms prove the correct immobilization of both the alkanethiol systems. The sensor is tested for detecting relevant markers for breast cancer. Results for 5 nM of the target TACSTD1 against the complementary TACSTD1 and non-complementary GRP, MYC, SCGB2A1, SCGB2A2, TOP2A probes show a remarkable detection limit of 0.05 nM and a high specificity. PMID:24948454

  12. 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

  13. 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. PMID:27232390

  14. 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.

  15. 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. PMID:25882423

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

    PubMed

    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. PMID:25022493

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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. PMID:25280680

  2. Synthesis and in vitro cytotoxicity of mPEG-SH modified gold nanorods

    NASA Astrophysics Data System (ADS)

    Didychuk, Candice L.; Ephrat, Pinhas; Belton, Michelle; Carson, Jeffrey J. L.

    2008-02-01

    Plasmon-resonant gold nanorods show great potential as an agent for contrast-enhanced biomedical imaging or for phototherapeutics. This is primarily due to the high molar extinction coefficient at the absorption maximum and the dependence of the wavelength of the absorption maximum on the aspect ratio, which is tunable in the near-infrared (NIR) during synthesis. Although gold nanorods can be produced in high-yield through the seed-mediated growth technique, the presence of residual cetyltrimethylammonium bromide (CTAB), a stabilizing surfactant required for nanorod growth, interferes with cell function and causes cytotoxicity. To overcome this potential obstacle to in vivo use, we synthesized gold nanorods and conjugated them to a methoxy (polyethylene glycol)-thiol (mPEG (5000)-SH). This approach yielded mPEG-SH modified gold nanorods with optical and morphometric properties that were similar to raw (CTAB) nanorods. Both the CTAB and mPEG-SH nanorods were tested for cytotoxicity against the HL-60 human leukemia cell line by trypan blue exclusion, and the mPEG-SH modified gold nanorods were also tested against a rat insulinoma (RIN-38) and squamous cell carcinoma (SCCVII) cell line. Cells incubated for 24 h with the mPEG-SH modified nanorods had little change in cell viability compared to cells incubated with vehicle alone. This was in contrast to cytotoxicity of CTAB nanorods on HL-60 cells. These results suggest that mPEG-SH modified gold nanorods are better suited for cell loading protocols and injection into animals and facilitate their use for imaging and phototherapeutic purposes.

  3. Label-free electrochemical aptasensor for sensitive thrombin detection using layer-by-layer self-assembled multilayers with toluidine blue-graphene composites and gold nanoparticles.

    PubMed

    Xie, Shunbi; Yuan, Ruo; Chai, Yaqin; Bai, Lijuan; Yuan, Yali; Wang, Yan

    2012-08-30

    In the present study, toluidine blue-graphene (Tb-Gra) nanocomposites were prepared to design a Lable-free electrochemical aptasensor for highly sensitive detection of thrombin based on layer-by-layer (LBL) technology. The nanocomposites with excellent redox electrochemical activities were first immobilized on the gold nanoparticles (nano-Au) modified glassy carbon electrodes (GCE). Then, the LBL structure was performed by electrostatic adsorption between the positively charged Tb-Gra and negatively charged nano-Au, which formed {Tb-Gra/nano-Au}(n) multilayer films for electroactive species enrichment and biomolecule immobilization. Subsequently, the thiolated thrombin binding aptamer (TBA) was assembled on the nano-Au surface through Au-S bond. In the presence of target thrombin (TB), the TBA on the multilayer could catch the thrombin onto the electrode surface, which resulted in a barrier for electro-transfer, leading to the decrease of the electrochemical signal of Tb-Gra nanocomposites. Under the optimal conditions, a wide detection range from 0.001 nM to 80 nM and a low detection limit of 0.33 pM (defined as S/N=3) for thrombin were obtained. In addition, the sensor exhibited excellent selectivity against other proteins. PMID:22939121

  4. 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.

  5. 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

  6. One-pot synthesis of hierarchical MnO2-modified diatomites for electrochemical capacitor electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Yu Xin; Huang, Ming; Li, Fei; Wang, Xue Li; Wen, Zhong Quan

    2014-01-01

    The hierarchical and porous MnO2-modified diatomite structures are prepared for the first time by a one-pot hydrothermal method. The morphology and structure of MnO2-modified diatomite hierarchical structures are examined by focus ion beam scanning electron microscopy (FIB/SEM) and X-ray diffraction spectroscopy (XRD). The results show that Birnessite-type MnO2 nanosheets are observed to grow vertically on the purified diatomite, thus building hierarchical architecture. Furthermore, the electrochemical properties of the MnO2-modified diatomite electrodes are elucidated by cyclic voltammograms, galvanostatic charge/discharge tests and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte. The electrochemical results demonstrate that the MnO2-modified diatomite electrode exhibits highly reversible features and good rate abilities, respectively. Significantly, it exhibits the specific capacitance of 202.6 F g-1 for the MnO2-modified diatomite and 297.8 F g-1 for the MnO2 nanostructures after etching the diatomite. The capacitance retention of 95.92% over 5000 cycles further indicates the suitability of the low-cost MnO2-modified diatomite structure as a potential electrode material for supercapacitors.

  7. On the stabilization of gold nanoparticles over silica-based magnetic supports modified with organosilanes.

    PubMed

    Oliveira, Rafael L; Zanchet, Daniela; Kiyohara, Pedro K; Rossi, Liane M

    2011-04-11

    The immobilization of gold nanoparticles (Au NPs) on silica is made possible by the functionalization of the silica surfaces with organosilanes. Au NPs could only be stabilized and firmly attached to silica-support surfaces that were previously modified with amino groups. Au NPs could not be stabilized on bare silica surfaces and most of the NPs were then found in the solution. The metal-support interactions before and after the Au NP formation, observed by X-ray absorption fine structure spectroscopy (XAFS), indicate a stronger interaction of gold(III) ions with amino-modified silica surfaces than with the silanol groups in bare silica. An amino-modified, silica-based, magnetic support was used to prepare an active Au NP catalyst for the chemoselective oxidation of alcohols, a reaction of great interest for the fine chemical industry. PMID:21360597

  8. 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.

  9. An electrochemical biosensor for alpha-fetoprotein based on carbon paste electrode constructed of room temperature ionic liquid and gold nanoparticles.

    PubMed

    Ding, Caifeng; Zhao, Fei; Ren, Rui; Lin, Jin-Ming

    2009-05-15

    A novel and effective electrochemical immunosensor for the rapid determination of alpha-fetoprotein (AFP) based on carbon paste electrode (CPE) consisting of room temperature ionic liquid (RTIL) N-butylpyridinium hexafluorophosphate (BPPF(6)) and graphite. The surface of the CPE was modified with gold nanoparticles for the immobilization of the alpha-fetoprotein antibody (anti-AFP). By sandwiching the antigen between anti-AFP on the CPE modified with gold nanoparticles and the secondary antibody, polyclonal anti-human-AFP labeled with horseradish peroxidase (HRP-labeled anti-AFP), the immunoassay was established. The concentration of AFP was determined based on differential pulse voltammetry (DPV) signal, which was generated in the reaction between O-aminophenol (OAP) and H(2)O(2) catalyzed by HRP labeled on the sandwich immunosensor. AFP concentration could be measured in a linear range of 0.50-80.00 ng mL(-1) with a detection limit of 0.25 ng mL(-1). The immunosensor exhibited high sensitivity and good stability, and would be valuable for clinical assay of AFP. PMID:19269485

  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. PMID:27619087

  11. 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

  12. Optical properties of structurally modified glasses doped with gold ions.

    PubMed

    Qiu, Jianrong; Jiang, Xiongwei; Zhu, Congshan; Inouye, Hideyuki; Si, Jinhai; Hirao, Kazuyuki

    2004-02-15

    We report on the optical properties of a structurally modified silicate glass doped with Au ions. The area in the vicinity of the focal point of an 800-nm femtosecond laser in a glass sample became gray as a result of the formation of color centers after laser irradiation and turned red because of precipitation of Au nanoparticles after further annealing at 550 degrees C for 30 min. When the glass was excited by UV light at 365 nm, yellowish-white and orange-yellow emissions were observed in the laser-irradiated and the Au-nanoparticle-precipitated area, respectively. An optical Kerr shutter experiment showed that the Au nanoparticle-precipitated glass had an ultrafast nonlinear optical response, and the third-order nonlinear susceptibility was estimated to be approximately 10(-11) esu. PMID:14971756

  13. Optical properties of structurally modified glasses doped with gold ions

    NASA Astrophysics Data System (ADS)

    Qiu, Jianrong; Jiang, Xiongwei; Zhu, Congshan; Inouye, Hideyuki; Si, Jinhai; Hirao, Kazuyuki

    2004-02-01

    We report on the optical properties of a structurally modified silicate glass doped with Au ions. The area in the vicinity of the focal point of an 800-nm femtosecond laser in a glass sample became gray as a result of the formation of color centers after laser irradiation and turned red because of precipitation of Au nanoparticles after further annealing at 550 °C for 30 min. When the glass was excited by UV light at 365 nm, yellowish-white and orange-yellow emissions were observed in the laser-irradiated and the Au-nanoparticle-precipitated area, respectively. An optical Kerr shutter experiment showed that the Au nanoparticle-precipitated glass had an ultrafast nonlinear optical response, and the third-order nonlinear susceptibility was estimated to be ~10-11 esu.

  14. 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

  15. 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. PMID:26354274

  16. Excitation energy migration in yellow fluorescent protein (citrine) layers adsorbed on modified gold surfaces

    NASA Astrophysics Data System (ADS)

    Yusoff, Hanis Mohd; Rzeźnicka, Izabela I.; Hoshi, Hirotaka; Kajimoto, Shinji; Horimoto, Noriko Nishizawa; Sogawa, Kazuhiro; Fukumura, Hiroshi

    2013-09-01

    The nature of functional proteins adsorbed on solid surfaces is interesting from the perspective of developing of bioelectronics and biomaterials. Here we present evidence that citrine (one of yellow fluorescent protein variants) adsorbed on modified gold surfaces would not undergo denaturation and energy transfer among the adsorbed citrine molecules would occur. Gold substrates were chemically modified with 3-mercaptopropionic acid and tert-butyl mercaptan for the preparation of hydrophilic and hydrophobic surfaces, respectively. A pure solution of citrine was dropped and dried on the modified gold substrates and their surface morphology was studied with scanning tunnelling microscopy (STM). The obtained STM images showed multilayers of citrine adsorbed on the modified surfaces. On hydrophobic surfaces, citrine was adsorbed more randomly, formed various non-uniform aggregates, while on hydrophilic surfaces, citrine appeared more aligned and isolated uniform protein clusters were observed. Fluorescence lifetime and anisotropy decay of these dried citrine layers were also measured using the time correlated single photon counting method. Fluorescence anisotropy of citrine on the hydrophobic surface decayed faster than citrine on the hydrophilic surface. From these results we concluded that fluorescence energy migration occurred faster among citrine molecules which were randomly adsorbed on the hydrophobic surface to compare with the hydrophilic surface.

  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. PMID:24061929

  18. Electrochemically assisted fabrication of size-exclusion films of organically modified silica and application to the voltammetry of phospholipids

    PubMed Central

    Mehdi, B. Layla; Rutkowska, Iwona A.; Kulesza, Pawel J.

    2013-01-01

    Modification of electrodes with nm-scale organically modified silica films with pores diameters controlled at 10- and 50-nm is described. An oxidation catalyst, mixed-valence ruthenium oxide with cyano crosslinks or gold nanoparticles protected by dirhodium-substituted phosophomolybdate (AuNP-Rh2PMo11), was immobilized in the pores. These systems comprise size-exclusion films at which the biological compounds, phosphatidylcholine and cardiolipin, were electrocatalytically oxidized without interference from surface-active concomitants such as bovine serum albumin. 10-nm pores were obtained by adding generation-4 poly(amidoamine) dendrimer, G4-PAMAM, to a (CH3)3SiOCH3 sol. 50-nm pores were obtained by modifying a glassy carbon electrode (GC) with a sub-monolayer film of aminopropyltriethoxylsilane, attaching 50-nm diameter poly(styrene sulfonate), PSS, spheres to the protonated amine, transferring this electrode to a (CH3)3SiOCH3 sol, and electrochemically generating hydronium at uncoated GC sites, which catalyzed ormosil growth around the PSS. Voltammetry of Fe(CN)63− and Ru(NH3)63+ demonstrated the absence of residual charge after removal of the templating agents. With the 50-nm system, the pore structure was sufficiently defined to use layer-by-layer electrostatic assembly of AuNP-Rh2PMo11 therein. Flow injection amperometry of phosphatidylcholine and cardiolipin demonstrated analytical utility of these electrodes. PMID:23935394

  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. PMID:26397420

  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. PMID:27111123

  1. 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

  2. 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

  3. 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

  4. Surface studies of aminoferrocene derivatives on gold: electrochemical sensors for chemical warfare agents.

    PubMed

    Khan, Mohammad A K; Long, Yi-Tao; Schatte, Gabriele; Kraatz, Heinz-Bernhard

    2007-04-01

    The cystamine conjugate [(BocNH)Fc(CO)CSA]2 was prepared by coupling cystamine with the N-protected ferrocene amino acid derivative BocHN-Fc-COOH and was fully characterized by spectroscopic methods and by single-crystal X-ray diffraction. The cystamine conjugate forms films on gold substrates, which upon deprotection of the amino group, react with chemical warfare agent (CWA) mimics, upon which the redox properties of the Fc group are affected significantly. Cyclic voltammetry shows 50(5) mV anodic shifts of the Fc redox potentials after exposure to EtSCH2CH2Cl, a simulant for sulfur mustard HD (MA), and (NC)(EtO)2P(O), a simulant for nerve agent Tabun (NA). Exposure to MA and NA causes an increase in 2.3 and 4.5 ng mass, respectively, in QCM which indicates ca. 70% efficiency in Boc-deprotection. Ellipsometry measured a film thickness increase from 6(+/-1) A for the deprotected film to 10(+/-4) A for the film modified with MA and to 7(+/-2) A for the film modified with NA. AFM measurements show changes in the thickness and morphology of the film after reaction with MA and NA. The surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and clearly show the attachment of the cystamine conjugate on the surface and its reaction with CWA mimics. PMID:17319647

  5. 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

  6. 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

  7. Highly sensitive electrochemical sensor based on β-cyclodextrin-gold@3, 4, 9, 10-perylene tetracarboxylic acid functionalized single-walled carbon nanohorns for simultaneous determination of myricetin and rutin.

    PubMed

    Ran, Xin; Yang, Long; Zhang, Jianqiang; Deng, Guogang; Li, Yucong; Xie, Xiaoguang; Zhao, Hui; Li, Can-Peng

    2015-09-10

    The application of macrocyclic hosts for construction of different electrochemical devices and separation matrices has attracted much attentions due to their benign biocompatibility and simplicity of synthesis. Myricetin and rutin are considered two of the most bioactive flavonoids, which have been proved to exhibit various physiological functions. This work reports a simple and facile approach for the synthesis of β-cyclodextrin-gold@3, 4, 9, 10-perylene tetracarboxylic acid functionalized single-walled carbon nanohorns (β-CD-Au@PTCA-SWCNHs) nanohybrids. The simultaneous electrochemical determination of myricetin and rutin using a β-CD-Au@PTCA-SWCNHs-modified glassy carbon electrode was established. The results show that the β-CD-Au@PTCA-SWCNHs-modified electrode displayed electrochemical signal superior to those of Au@PTCA-;SWCNHs and SWCNHs towards myricetin and rutin. The proposed modified electrode has a linear response range of 0.01-10.00 μM both for myricetin and rutin with relatively low detection limits of 0.0038 μM for myricetin and 0.0044 μM (S/N = 3) for rutin, respectively. The excellent performance of the sensing platform is considered to be the synergic effects of the SWCNHs (e.g. their good electrochemical properties and large surface area) and β-CD (e.g. a hydrophilic external surface, a high supramolecular recognition, and a good enrichment capability). PMID:26388478

  8. 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. PMID:26041516

  9. 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.

  10. 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

  11. Disposable electrochemical immunosensor by using carbon sphere/gold nanoparticle composites as labels for signal amplification.

    PubMed

    Xu, Qiunan; Yan, Feng; Lei, Jianping; Leng, Chuan; Ju, Huangxian

    2012-04-16

    This work designed a simple, sensitive, and low-cost immunosensor for the detection of protein marker by using a carbon sphere/gold nanoparticle (CNS/AuNP) composite as an electrochemical label. The nanoscale carbon spheres, prepared with a hydrothermal method by using glucose as raw material, were used to load AuNPs for labeling antibody by electrostatic interaction, which provided a feasible pathway for electron transfer due to the remarkable conductivity. The disposable immunosensor was constructed by coating a polyethylene glycol (PEG) film on a screen-printed carbon-working electrode and then immobilizing capture antibody on the film. With a sandwich-type immunoassay format, the analyte and then the CNS/AuNP-labeled antibody were successively bound to the immunosensor. The bound AuNPs were finally electro-oxidized in 0.1  M HCl to produce AuCl(4)(-) for differential pulse voltammetric (DPV) detection. The high-loading capability of AuNPs on CNS for the sandwich-type immunorecognition led to obvious signal amplification. By using human immunoglobulin G (IgG) as model target, the DPV signal of AuNPs after electro-oxidized at optimal potential of +1.40 V for 40 s showed a wide linear dependence on the logarithm of target concentration ranging from 10 pg  mL(-1) to 10 ng  mL(-1). The detection limit was around 9 pg  mL(-1). The immunosensor showed excellent analytical performance with cost effectivity, good fabrication reproducibility, and acceptable precision and accuracy, providing significant potential application in clinical analysis. PMID:22438025

  12. 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.

  13. Optical properties and electrochemical dealloying of Gold-Silver alloy nanoparticles immobilized on composite thin-film electrodes

    NASA Astrophysics Data System (ADS)

    Starr, Christopher A.

    potentials for both silver oxidation and gold dealloying also shifted to more oxidizing potentials with increasing gold content, and both processes converged for alloy NPs with >60% gold content. Charge-mediated electrochemistry of silver NPs immobilized in LbL films, using Fc(meOH) as the charge carrier, showed that 67% of the NPs were electrochemically inactive.

  14. Significantly improved electrochemical hydrogen storage properties of magnesium nickel hydride modified with nano-nickel

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Zhu, Yunfeng; Yang, Chen; Zhang, Jiguang; Li, Menghuai; Li, Liquan

    2015-04-01

    Magnesium nickel hydride (Mg2NiH4) used as negative electrode material in nickel-metal hydride (Ni-MH) secondary battery is modified by nano-nickel via mechanical milling. In this paper, we systematically investigate the microstructure and electrochemical properties of the modified system with different milling durations. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analyses confirm the amorphous transformation of Mg2Ni-based hydride and a novel NiH0.75 nanocrystalline with a diameter of about 5 nm embedding or covering on the surface of the base particle has been observed. Its formation mechanism and positive effects on electrochemical properties of the Mg2NiH4 have also been elaborated. Electrochemical measurements show that the 5 h milled composite possesses markedly increased discharge capacity up to 896 mAh g-1. With prolonging the milling duration from 5 h to 40 h, the discharge capacity at the 10th cycle increases from 99 mAh g-1 to 359 mAh g-1. Besides, the discharging procedure changes from stepwise processes to one single-step process with increasing the milling duration. Tafel polarization test shows that the nano-nickel modified system exhibits a much better anti-corrosion ability during charging/discharging cycles. Meanwhile, both the charge-transfer reaction on the alloy surface and hydrogen diffusion inside the alloy bulk are enhanced with nano-nickel modification.

  15. 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

  16. 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

  17. Fabrication of an electrochemical sensor based on gold nanoparticles/carbon nanotubes as nanocomposite materials: determination of myricetin in some drinks.

    PubMed

    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

  18. 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.

  19. 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

  20. Fabrication of DNA microarrays on polydopamine-modified gold thin films for SPR imaging measurements.

    PubMed

    Wood, Jennifer B; Szyndler, Megan W; Halpern, Aaron R; Cho, Kyunghee; Corn, Robert M

    2013-08-27

    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 ultrasensitive 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 non-complementary 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

  1. 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

  2. Synthesis, density functional theory, molecular dynamics and electrochemical studies of 3-thiopheneacetic acid-capped gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Sosibo, Ndabenhle M.; Mdluli, Phumlane S.; Mashazi, Philani N.; Dyan, Busiswa; Revaprasadu, Neerish; Nyokong, Tebello; Tshikhudo, Robert T.; Skepu, Amanda; van der Lingen, Elma

    2011-12-01

    Gold nanoparticles capped with a bifunctional ligand, 3-thiopheneacetic acid (3-TAA) were synthesised by borohydride reduction at room temperature. The transmission electron microscopy (TEM) analysis showed that the particle aggregates and had semi-linear partial linkages that could be attributed to multi-modal binding of the ligand with various gold nanoparticles through the terminal thiolether (-S-) group and oxygen of the carboxylic (-COOH) group. This bimodal interaction led to limited stability of the resultant nanoparticles when tested using highly electrolytic media. To investigate further, density functional theory (DFT) quantum chemical and molecular dynamic calculations were conducted. The energetically favorable binding modes of the ligand to gold nanoparticle surfaces using the Gaussian program were studied. The DFT results showed kinetic stability of Au-3-TAA-Au interactions leading to inter-particle coupling or aggregation. Electrochemical analysis of the resultant nature of the capping agent revealed that 3-thiopheneacetic acid did not form a polymer during the preparation of Au-3-TAA. The cyclic voltammograms of Au-3-TAA nanoparticles coated glassy carbon electrode showed a typical gold character with the oxidation and reduction peaks at 1.4 V and 0.9 V, respectively.

  3. 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.

  4. Development of a simple bioelectrode for the electrochemical detection of hydrogen peroxide using Pichia pastoris catalase immobilized on gold nanoparticle nanotubes and polythiophene hybrid.

    PubMed

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

    2014-11-21

    In this paper, a simple and innovative electrochemical hydrogen peroxide biosensor has been proposed using catalase (CATpp) derived from Pichia pastoris as bioelectrocatalyst. The model biocomponent was immobilized on gold nanoparticle nanotubes (AuNPNTs) and polythiophene composite using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide (EDC-NHS) coupling reagent. In this present work, we have successfully synthesized gold nanoparticles (AuNPs) by ultrasonic irradiation. The tubular gold nanostructures containing coalesced AuNPs were obtained by sacrificial template synthesis. The assembly of AuNPNTs onto the graphite (Gr) electrode was achieved via S-Au chemisorption. The latter was pre-coated with electropolymerized thiophene (PTh) to enable S groups to bind AuNPNTs. The combination of AuNPNTs-PTh, i.e., an inorganic-organic hybrid, provides a stable enzyme immobilization platform. The physical morphology of the fabricated biosensor Gr/PTh/AuNPNTs/EDC-NHS/CATpp was investigated using scanning electron microscopy and energy-dispersive microscopy. The analytical performance of the bioelectrode was examined using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. Operational parameters such as working potential, pH, and thermal stability of the modified electrode were examined. The beneficial analytical characteristics of the proposed electrode were demonstrated. Our results indicate that the Gr/PTh/AuNPNTs/EDC-NHS/CATpp bioelectrode exhibits a wide linear range from 0.05 mM to 18.5 mM of H2O2, fast response time of 7 s, excellent sensitivity of 26.2 mA mM(-1) cm(-2), good detection limit of 0.12 μM and good Michaelis-Menten constant of 1.4 mM. In addition, the bioelectrode displayed good repeatability, high stability and acceptable reproducibility, which can be attributed to the AuNPNTs-PTh composite that provides a biocompatible micro-environment. PMID:25208248

  5. 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. PMID:26838915

  6. Characterization of gold-thiol-8-hydroxyquinoline self-assembled monolayers for selective recognition of aluminum ion using voltammetry and electrochemical impedance spectroscopy.

    PubMed

    Shervedani, Reza Karimi; Rezvaninia, Zeinab; Sabzyan, Hassan; Boeini, Hassan Zali

    2014-05-12

    Gold electrode surface is modified via covalent attachment of a synthesized thiol functionalized with 8-hydroxyquinoline, p-((8-hydroxyquinoline)azo) benzenethiol (SHQ), for the first time. The behavior of the nanostructured electrode surface (Au-SHQ) is characterized by electrochemical techniques including cyclic and differential pulse voltammetry (CV and DPV), and electrochemical impedance spectroscopy (EIS). The modified surface is stable in a wide range of potentials and pHs. A surface pKa of 6.0±0.1 is obtained for Au-SHQ electrode using surface acid/base titration curves constructed by CV and EIS measurements as a function of pH. These results helped to determine the charge state of the surface as a function of pH. The gold modified electrode surface showed good affinity for sensing the Al(III) ion at pH 5.5. The sensing process is based on (i) accumulation and complex formation between Al(III) from the solution phase and 8HQ function on the Au electrode surface (recognition step) and (ii) monitoring the impedance of the Au-SHQ-Al(III) complex against redox reaction rate of parabenzoquinone (PBQ) (signal transduction step). The PBQ is found to be a more suitable probe for this purpose, after testing several others. Thus, the sensor was tested for quantitative determination of Al(III) from the solution phase. At the optimized conditions, a linear response, from 1.0×10(-11) to 1.2×10(-5) M Al(III) in semi-logarithmic scale, with a detection limit of 8.32×10(-12) M and mean relative standard deviation of 3.2% for n=3 at 1.0×10(-7) M Al(III) is obtained. Possible interferences from coexisting cations and anions are also studied. The results show that many ions do not interfere significantly with the sensor response for Al(III). Validity of the method and applicability of the sensor are successfully tested by determination of Al(III) in human blood serum samples. PMID:24767148

  7. 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

  8. 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

  9. Gold nanoparticles decorated poly-melamine modified glassy carbon sensor for the voltammetric estimation of domperidone in pharmaceuticals and biological fluids.

    PubMed

    Rosy; Goyal, Rajendra N

    2015-08-15

    The electrochemical response of an unmodified glassy carbon (GCE), poly-melamine/GCE and gold nanoparticle (AuNP)/poly-melamine/GCE is compared in the present protocol for the sensitive and selective determination of domperidone (DOM). The AuNPs were synthesized in the laboratory and characterized using UV-visible spectroscopy and Transmission Electron Microscopy (TEM). Melamine was electropolymerized onto the glassy carbon surface using cyclic voltammetry and was investigated using Field Emission Scanning Electron Microscopy (FE-SEM) and Electrochemical Impedance Spectroscopy (EIS). The AuNP/poly-melamine/GCE exhibited the best electrochemical response among the three electrodes for the electro-oxidation of DOM, that was inferred from the EIS, cyclic and square wave voltammetry. The modified sensor showed a sensitive, stable and linear response in the concentration range of 0.05-100µM with a detection limit of 6nM. The selectivity of the proposed sensor was assessed in the presence of high concentration of major interfering molecules as xanthine, hypoxanthine, and uric acid. The analytical application of the sensor for the quantification of DOM in pharmaceutical formulations and biological fluids as urine and serum was also investigated and the results demonstrated a recovery of >95% with R.S.D of <5%. PMID:25966380

  10. Modified electrodes used for electrochemical detection of metal ions in environmental analysis.

    PubMed

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

    2015-06-01

    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

  11. 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

  12. Electrochemical behavior of an anticancer drug 5-fluorouracil at methylene blue modified carbon paste electrode.

    PubMed

    Bukkitgar, Shikandar D; Shetti, Nagaraj P

    2016-08-01

    A novel sensor for the determination of 5-fluorouracil was constructed by electrochemical deposition of methylene blue on surface of carbon paste electrode. The electrode surface morphology was studied using Atomic force microscopy and XRD. The electrochemical activity of modified electrode was characterized using cyclic voltammetry and differential pulse method. The developed sensor shows impressive enlargement in sensitivity of 5-fluorouracil determination. The peak currents obtained from differential pulse voltammetry was linear with concentration of 5-fluorouracil in the range 4×10(-5)-1×10(-7)M and detection limit and quantification limit were calculated to be 2.04nM and 6.18nM respectively. Further, the sensor was successfully applied in pharmaceutical and biological fluid sample analysis. PMID:27157751

  13. Folic-Acid-Modified Conducting Polymer: Electrochemical Detection of the Cell Attachment.

    PubMed

    Azak, Hacer; Barlas, Firat Baris; Yildiz, Huseyin Bekir; Gulec, Kadri; Demir, Bilal; Demirkol, Dilek Odaci; Timur, Suna

    2016-04-01

    Here, postfunctionalization and bioapplication of a π-conjugated polymer named 4-[4H-dithieno(3,2-b:2',3'-d)pyrrol-4-yl]aniline (DTP-aryl-NH2 ) are reported, which is successfully synthesized via electropolymerization onto the glassy carbon electrode. Folic acid (FA) is used to modify the amino functional polymer via N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide chemistry for the further steps. The selective adhesion of folate receptor positive cells on the surface is followed by the electrochemical methods. Cyclic voltammetry and electrochemical impedance spectroscopy have been used to characterize stepwise modification of the electroactive surface. After optimization studies such as scan rate during the polymer deposition, FA amount for the efficient surface targeting, incubation time with the cells etc., analytical characterization is carried out. The surface morphologies at each step are imaged by using fluorescence microscopy. PMID:26671168

  14. A Rapid Colorimetric Sensor of Clenbuterol Based on Cysteamine-Modified Gold Nanoparticles.

    PubMed

    Kang, Jingyan; Zhang, Yujie; Li, Xing; Miao, Lijing; Wu, Aiguo

    2016-01-13

    Demonstrated was a simple visual and rapid colorimetric sensor for detection of clenbuterol (CLB) based on gold nanoparticles (AuNPs) modified with cysteamine (CA) and characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-vis. The solution color from red to blue gray with increasing clenbuterol concentration resulted from the aggregation of AuNPs. The detection limit of clenbuterol is 50 nM by naked eyes. The selectivity of CA-AuNPs detection system for clenbuterol is excellent compared with other interferents in food. This sensor has been successfully applied to detect clenbuterol in real blood sample. PMID:26673452

  15. 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

  16. Electrochemical deoxyribonucleic acid biosensor based on the self-assembly film with nanogold decorated on ionic liquid modified carbon paste electrode.

    PubMed

    Gao, Hongwei; Qi, Xiaowei; Chen, Ying; Sun, Wei

    2011-10-17

    An electrochemical DNA biosensor was fabricated by self-assembling probe single-stranded DNA (ssDNA) with a nanogold decorated on ionic liquid modified carbon paste electrode (IL-CPE). IL-CPE was fabricated using 1-butylpyridinium hexafluorophosphate as the binder and the gold nanoparticles were electrodeposited on the surface of IL-CPE (Au/IL-CPE). Then mercaptoacetic acid was self-assembled on the Au/IL-CPE to obtain a layer of modified film, and the ssDNA probe was further covalently-linked with mercaptoacetic acid by the formation of carboxylate ester with the help of N-(3-dimethylamino-propyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The hybridization reaction with the target ssDNA was monitored with methylene blue (MB) as the electrochemical indicator. Under the optimal conditions, differential pulse voltammetric responses of MB was proportional to the specific ssDNA arachis sequences in the concentration range from 1.0×10(-11) to 1.0×10(-6) mol L(-1) with the detection limit as 1.5×10(-12) mol L(-1) (3σ). This electrochemical DNA sensor exhibited good stability and selectivity with the discrimination ability of the one-base and three-base mismatched ssDNA sequences. The polymerase chain reaction product of arachis Arabinose operon D gene was successfully detected by the proposed method, which indicated that the electrochemical DNA sensor designed in this paper could be further used for the detection of specific ssDNA sequence. PMID:21907030

  17. 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.

  18. 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

  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. A cationic azobenzene-surfactant-modified graphene hybrid: unique photoresponse and electrochemical behavior

    NASA Astrophysics Data System (ADS)

    Chen, Shu; Bao, Lin; Ou, Encai; Peng, Chang; Wang, Weimao; Xu, Weijian

    2015-11-01

    Surfactant-modified graphene hybrids containing azobenzene groups were for the first time prepared, and the electrochemical performance was investigated. The hybrids were obtained by electrostatic interactions between cationic azobenzene-surfactants and negatively charged graphene oxide in water. The electrostatic interactions, chemical structure and photoresponse of the hybrids were measured by using zeta potential values, fluorescence spectra, FTIR, XPS, XRD, SEM, UV-Vis absorption, AFM and Raman spectra. The electrochemical performance was estimated using cyclic voltammetry. The results show that strong electrostatic interactions exist between the azobenzene surfactants and graphene oxide. Notably, this azobenzene-graphene hybrid can self-assemble into aggregation structures in aqueous solution. Besides, the self-assembly can be reversibly controlled by ultraviolet light (365 nm) and blue light (455 nm) irradiation. This process is driven by the photoinduced polarity change of the cationic azobenzene surfactant and is responsible for the graphene hybrids' electrochemical performance. It is the first example of the reversible self-assembly of graphene driven by light irradiation.Surfactant-modified graphene hybrids containing azobenzene groups were for the first time prepared, and the electrochemical performance was investigated. The hybrids were obtained by electrostatic interactions between cationic azobenzene-surfactants and negatively charged graphene oxide in water. The electrostatic interactions, chemical structure and photoresponse of the hybrids were measured by using zeta potential values, fluorescence spectra, FTIR, XPS, XRD, SEM, UV-Vis absorption, AFM and Raman spectra. The electrochemical performance was estimated using cyclic voltammetry. The results show that strong electrostatic interactions exist between the azobenzene surfactants and graphene oxide. Notably, this azobenzene-graphene hybrid can self-assemble into aggregation structures in aqueous

  1. Assembly of hybrid oligonucleotide modified gold (Au) and alloy nanoparticles building blocks.

    PubMed

    Kuo, Yu-Ching; Jen, Chun-Ping; Chen, Yu-Hung; Su, Chia-Hao; Tsai, Shu-Hui; Yeh, Chen-Sheng

    2006-01-01

    The alloy-based hybrid materials with macroscopic network arrays were developed by AuAg/Au and AuAgPd/Au nanoparticle composites through oligonucleotides hybridization. AuAg/Au and AuAgPd/Au exhibited distinct organization. The morphology of AuAg/Au conjugation assembled mainly as compact aggregates while AuAgPd/Au hybrid conjugated into the loosen network assemblies. The dehybridization temperatures were studied as a function of molar ratio of alloy/Au. It was found that higher alloy/gold molar ratio led to stronger hybridization for alloy/gold composite, accompanied with increased melting temperature. These results could be interpreted in terms of more alloy nanoparticles bound to a Au particle when the molar ratio of alloy/gold increased. The thermal analysis also showed that AuAg/Au exhibited higher dehybridization temperature. A modified model describing the dehybridization probability of an intact Au/alloy aggregate was performed to support the dehybridization temperature increased with increasing alloy/Au molar ratio. As to more oligonucleotides carried by AuAg (4.9 +/- 1.9 nm) than by AuAgPd (4.4 +/- 1.5 nm) due to larger size in AuAg, the efficient hybridization could result in higher dehybridization temperature in AuAg/Au. PMID:16573077

  2. 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

  3. 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

  4. Electrochemical synthesis of nanostructured gold film for the study of carbohydrate–lectin interactions using localized surface plasmon resonance spectroscopy

    PubMed Central

    Bhattarai, Jay K.; Sharma, Abeera; Fujikawa, Kohki; Demchenko, Alexei V.; Stine, Keith J.

    2014-01-01

    Localized surface plasmon resonance (LSPR) spectroscopy is a label-free chemical and biological molecular sensing technique whose sensitivity depends upon development of nanostructured transducers. Herein, we report an electrodeposition method for fabricating nanostructured gold films (NGFs) that can be used as transducers in LSPR spectroscopy. The NGF was prepared by electrodepositing gold from potassium dicyanoaurate solution onto a flat gold surface using two sequential controlled potential steps. Imaging by scanning electron microscopy reveals a morphology consisting of randomly configured block-like nanostructures. The bulk refractive index sensitivity of the prepared NGF is 100 ± 2 nm RIU−1 and the initial peak in the reflectance spectrum is at 518 ± 1 nm under N2(g). The figure of merit is 1.7. In addition, we have studied the interaction between carbohydrate (mannose) and lectin (Concanavalin A) on the NGF surface using LSPR spectroscopy by measuring the interaction of 8-mercaptooctyl-α-D-mannopyranoside (αMan-C8-SH) with Concanavalin A by first immobilizing αMan-C8-SH in mixed SAMs with 3,6-dioxa-8-mercaptooctanol (TEG-SH) on the NGF surface. The interaction of Con A with the mixed SAMs is confirmed using electrochemical impedance spectroscopy. Finally, the NGF surface was regenerated to its original sensitivity by removing the SAM and the bound biomolecules. The results from these experiments contribute toward the development of inexpensive LSPR based sensors that could be useful for studying glycan–protein interactions and other bioanalytical purposes. PMID:25442712

  5. 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.

  6. A cationic azobenzene-surfactant-modified graphene hybrid: unique photoresponse and electrochemical behavior.

    PubMed

    Chen, Shu; Bao, Lin; Ou, Encai; Peng, Chang; Wang, Weimao; Xu, Weijian

    2015-12-14

    Surfactant-modified graphene hybrids containing azobenzene groups were for the first time prepared, and the electrochemical performance was investigated. The hybrids were obtained by electrostatic interactions between cationic azobenzene-surfactants and negatively charged graphene oxide in water. The electrostatic interactions, chemical structure and photoresponse of the hybrids were measured by using zeta potential values, fluorescence spectra, FTIR, XPS, XRD, SEM, UV-Vis absorption, AFM and Raman spectra. The electrochemical performance was estimated using cyclic voltammetry. The results show that strong electrostatic interactions exist between the azobenzene surfactants and graphene oxide. Notably, this azobenzene-graphene hybrid can self-assemble into aggregation structures in aqueous solution. Besides, the self-assembly can be reversibly controlled by ultraviolet light (365 nm) and blue light (455 nm) irradiation. This process is driven by the photoinduced polarity change of the cationic azobenzene surfactant and is responsible for the graphene hybrids' electrochemical performance. It is the first example of the reversible self-assembly of graphene driven by light irradiation. PMID:26553111

  7. The electrochemical behavior of gold in ammoniacal solutions at 75 °C

    NASA Astrophysics Data System (ADS)

    Dasgupta, Rajib; Guan, Y. Charles; Han, Kenneth N.

    1997-02-01

    The dissolution behavior of gold in ammoniacal solutions at 75 °C has been investigated. The variables investigated include concentration of lixiviants, pH of the solution, and various oxidants. The anodic dissolution of gold was studied in the absence of oxidants using the potentiodynamic polarization technique. The cathodic reaction of oxidants were studied on a platinum electrode. Tafel polarization tests were also performed to determine the dissolution rate. The overall dissolution of gold in ammoniacal solutions was examined using a mixed potential theory. A comparative study on the role of cupric ammine, oxygen, hydrogen peroxide, and sodium hypochlorite as oxidants for the dissolution of gold in ammoniacal solutions has been carried out.

  8. 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

  9. 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

  10. Electrochemical properties of seamless three-dimensional carbon nanotubes-grown graphene modified with horseradish peroxidase.

    PubMed

    Komori, Kikuo; Terse-Thakoor, Trupti; Mulchandani, Ashok

    2016-10-01

    Horseradish peroxidase (HRP) was immobilized through sodium dodecyl sulfate (SDS) on the surface of a seamless three-dimensional hybrid of carbon nanotubes grown at the graphene surface (HRP-SDS/CNTs/G) and its electrochemical properties were investigated. Compared with graphene alone electrode modified with HRP via SDS (HRP-SDS/G electrode), the surface coverage of electroactive HRP at the CNTs/G electrode surface was approximately 2-fold greater because of CNTs grown at the graphene surface. Based on the increase in the surface coverage of electroactive HRP, the sensitivity to H2O2 at the HRP-SDS/CNTs/G electrode was higher than that at the HRP-SDS/G electrode. The kinetics of the direct electron transfer from the CNTs/G electrode to compound I and II of modified HRP was also analyzed. PMID:27224430