title: Direct electrochemical oxidation of S-captopril using gold electrodes modified with graphene-AuAg nanocomposites.
abstract: 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.
authors.affiliation: Department of Isotopic Physics and Technology, Chromatography, and Applied Physics, National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
authors.forename: Florina
authors.initials: F
authors.lastname: Pogacean
authors.affiliation: Department of Mass Spectrometry, Chromatography, and Applied Physics, National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
authors.forename: Alexandru R
authors.initials: AR
authors.lastname: Biris
authors.affiliation: Department of Isotopic Physics and Technology, Chromatography, and Applied Physics, National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
authors.forename: Maria
authors.initials: M
authors.lastname: Coros
authors.affiliation: Department of Isotopic Physics and Technology, Chromatography, and Applied Physics, National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
authors.forename: Mihaela Diana
authors.initials: MD
authors.lastname: Lazar
authors.affiliation: Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, Little Rock, Arkansas, USA.
authors.forename: Fumiya
authors.initials: F
authors.lastname: Watanabe
authors.affiliation: Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, Little Rock, Arkansas, USA.
authors.forename: Ganesh K
authors.initials: GK
authors.lastname: Kannarpady
authors.affiliation: Department of Physics, College of Science, King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Said A Farha
authors.initials: SA
authors.lastname: Al Said
authors.affiliation: Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, Little Rock, Arkansas, USA.
authors.forename: Alexandru S
authors.initials: AS
authors.lastname: Biris
authors.affiliation: Department of Isotopic Physics and Technology, Chromatography, and Applied Physics, National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
authors.forename: Stela
authors.initials: S
authors.lastname: Pruneanu
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000032:analysis / Q000737:chemistry; D002216:Captopril / Q000032:analysis* / Q000737:chemistry*; D055664:Electrochemical Techniques; D006046:Gold; D006108:Graphite; D053768:Metal Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D053761:Nanocomposites / Q000737:chemistry / Q000648:ultrastructure; D050997:Nanomedicine; D036103:Nanotechnology; D010084:Oxidation-Reduction; D012834:Silver; D013237:Stereoisomerism
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D012834:Silver; D006046:Gold; D006108:Graphite; D002216:Captopril
keywords: bimetallic AuAg nanoparticles; electrochemical detection; multi-layer graphene