Article

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

National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
International Journal of Nanomedicine (Impact Factor: 4.2). 04/2013; 8:1429-38. DOI: 10.2147/IJN.S42613
Source: PubMed

ABSTRACT 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.

0 Followers
 · 
155 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nanocomposite based on graphene and platinum nanoparticles was prepared by Radio Frequency catalytic Chemical Vapour Deposition (RF-cCVD) method over a Ptx/MgO catalytic system (x=1 wt.%). This composite was used for modification of a platinum electrode, and next employed to investigate the electrochemical behaviour of adenine by Linear Sweep Voltammetry (LCV). The results showed that the modified electrode had a good electro-catalytic activity towards the oxidation of adenine. The electrochemical characteristics of the modified electrode were also investigated by Electrochemical Impedance Spectroscopy (EIS). A theoretical model was developed based on an electrical equivalent circuit which contained: the solution resistance (Rs), the charge transfer resistance (Rct), the Warburg impedance (Zw) and the double layer capacitance (Cdl).
    11/2013; DOI:10.1063/1.4833731
  • [Show abstract] [Hide abstract]
    ABSTRACT: Composite materials based on graphene and platinum nanoparticles (Gr-Pt-2 and Gr-Pt-3) were synthesized over two catalysts (Pt-x/MgO, where x=2 or 3 wt.%) using radio-frequency catalytic chemical vapor deposition (RF-CCVD), with methane as carbon source. After morphological (TEM/HRTEM) and structural characterization (XRD, XPS, FTIR and UV-Vis) they were used to modify two gold electrodes and subsequently employed for the investigation of adenine and guanine electrochemical oxidation. For the Au/Gr-Pt-2 electrode, the oxidation peak potential of adenine was observed at +1.19V vs. Ag/AgCl, while, for Au/Gr-Pt-3 electrode, this was negatively shifted to +1.09V vs. Ag/AgCl. In addition, the oxidation current densities were approximately 2.7 x 10(-4) and 6.9 x 10(-4) A.cm(-2) (for Au/Gr-Pt-2 and Au/Gr-Pt-3, respectively) demonstrating that the Gr-Pt-3 composite had a better electro-catalytic activity towards the oxidation of adenine. A similar behavior was observed for guanine oxidation. The excellent electro-catalytic properties of the Gr-Pt-3 sample were correlated with the fact that the composite material had a higher amount of platinum nanoparticles which were not fully covered by graphene layers (about 50%). In addition, it has a larger surface area (335 m(2).g(-1)) compared with that of the Gr-Pt-2 sample (271 m(2).g(-1)), which also greatly improved the electron kinetics.
    Electrochimica Acta 09/2014; 139:386-393. DOI:10.1016/j.electacta.2014.06.163 · 4.09 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Interest in electrochemical analysis of purine nucleobases and few other important purine derivatives has been growing rapidly. Over the period of the past decade, the design of electrochemical biosensors has been focused on achieving high sensitivity and efficiency. The range of existing electrochemical methods with carbon electrode displays the highest rate in the development of biosensors. Moreover, modification of electrode surfaces based on nanomaterials is frequently used due to their extraordinary conductivity and surface to volume ratio. Different strategies for modifying electrode surfaces facilitate electron transport between the electrode surface and biomolecules, including DNA, oligonucleotides and their components. This review aims to summarize recent developments in the electrochemical analysis of purine derivatives, as well as discuss different applications.
    Sensors 01/2015; 15(1):1564-1600. DOI:10.3390/s150101564 · 2.05 Impact Factor