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

Abstract

This work describes the synthesis of few-layer graphene sheets embedded with various amounts of gold nanoparticles (Gr-Au-x) over an Au x /MgO catalytic system (where x = 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 (I 0 , 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.

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

“…In the case of the Gr-AuAg-1.5 composite, the size of the crystalline domain was almost double (4.08 nm) that of the Gr-AuAg-1 composite and corresponded to about eleven graphitic layers. This finding is in excellent agreement with previous results, 30 which demonstrated, for the first time, that by increasing the amount of Au nanoparticles in the catalytic system (Au x /MgO) from x=1 to 3 wt%, the degree of crystallinity of graphene sheets considerably increased. The sample prepared with the catalyst having 3 wt% Au exhibited the highest degree of crystallinity.…”

Gold nanoparticles-based electrochemical method for the detection of protein kinase with a peptide-like inhibitor as the bioreceptor

“…However, when the peptide immobilized on the electrode surface bound with PKA, the resulting peptide-PKA complex prevented the assembly of AuNPs as the principle in the colorimetric assay. As AuNPs show excellent electrical conductivity and high surface area of AuNPs, [63][64][65][66][67] this process could easily be monitored by electrochemical impedance spectroscopy or voltammetric technique by employing a redox-labeled PKA-binding peptide. The proposed electrochemical method not only features simple manipulation principle similar to that of colorimetric assay but also shows high sensitivity and specificity of electroanalysis.…”

Graphene based nanomaterials as chemical sensors for hydrogen peroxide – A comparison study of their intrinsic peroxidase catalytic behavior

“…Graphene-metalic nanoparticles composites (Gr-Au, Gr-Ag and Gr-Pt) were prepared by catalytic Chemical Vapor Deposition with Induction Heating (cCVD-IH) as described in detail elsewhere [9][10][11]. Briefly, Gr-Au, Gr-Ag and Gr-Pt composites were prepared over the corresponding mixed catalyst (Au x /MgO, Ag x /MgO, Pt x /MgO, where x = 3 wt%) at 1000 • C, using methane gas as carbon source.…”

“…The methods corresponding to the first approach (e.g. catalytic chemical vapor deposition [9][10][11]) are generally providing high-quality graphene with quite low productivity. Similar quality of graphene nanosheets but limited quantities can be obtained by mechanical exfoliation of graphite as a top-down approach.…”