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Open AccessFeature PaperArticle

Nitrogen-Doped Graphene: The Influence of Doping Level on the Charge-Transfer Resistance and Apparent Heterogeneous Electron Transfer Rate

1
National Institute for Research and Development of Isotopic and Molecular Technologies, Donat Street, No. 67-103, 400293 Cluj-Napoca, Romania
2
Department of Chemistry and Chemical Engineering, Hungarian Line of Study, Babes-Bolyai University, 11 Arany János St., 400028 Cluj-Napoca, Romania
*
Authors to whom correspondence should be addressed.
Sensors 2020, 20(7), 1815; https://doi.org/10.3390/s20071815
Received: 19 February 2020 / Revised: 20 March 2020 / Accepted: 23 March 2020 / Published: 25 March 2020
Three nitrogen-doped graphene samples were synthesized by the hydrothermal method using urea as doping/reducing agent for graphene oxide (GO), previously dispersed in water. The mixture was poured into an autoclave and placed in the oven at 160 °C for 3, 8 and 12 h. The samples were correspondingly denoted NGr-1, NGr-2 and NGr-3. The effect of the reaction time on the morphology, structure and electrochemical properties of the resulting materials was thoroughly investigated using scanning electron microscopy (SEM) Raman spectroscopy, X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), elemental analysis, Cyclic Voltammetry (CV) and electrochemical impedance spectroscopy (EIS). For NGr-1 and NGr-2, the nitrogen concentration obtained from elemental analysis was around 6.36 wt%. In the case of NGr-3, a slightly higher concentration of 6.85 wt% was obtained. The electrochemical studies performed with NGr modified electrodes proved that the charge-transfer resistance (Rct) and the apparent heterogeneous electron transfer rate constant (Kapp) depend not only on the nitrogen doping level but also on the type of nitrogen atoms found at the surface (pyrrolic-N, pyridinic-N or graphitic-N). In our case, the NGr-1 sample which has the lowest doping level and the highest concentration of pyrrolic-N among all nitrogen-doped samples exhibits the best electrochemical parameters: a very small Rct (38.3 Ω), a large Kapp (13.9 × 10−2 cm/s) and the best electrochemical response towards 8-hydroxy-2′-deoxyguanosine detection (8-OHdG). View Full-Text
Keywords: nitrogen-doped graphene; charge-transfer resistance; apparent heterogeneous electron transfer rate; modified electrodes; detection of 8-OHdG nitrogen-doped graphene; charge-transfer resistance; apparent heterogeneous electron transfer rate; modified electrodes; detection of 8-OHdG
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MDPI and ACS Style

Coros, M.; Varodi, C.; Pogacean, F.; Gal, E.; Pruneanu, S.M. Nitrogen-Doped Graphene: The Influence of Doping Level on the Charge-Transfer Resistance and Apparent Heterogeneous Electron Transfer Rate. Sensors 2020, 20, 1815.

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