Efficient Electrochemical Sensing Using Hybrid Boron-Doped Diamond/Graphene Nanowall Electrodes
Authors: Dettlaff Anna , Jakóbczyk Paweł , Kowalski Marcin Krzysztof , Brodowski Mateusz , Ficek Mateusz , Ossowski Tadeusz , Bogdanowicz Robert 
Published: May 2020

Electrochemical sensors have attracted increasing interest due to their low cost, high sensitivity of detected analytes, and the possibility of sensor miniaturization, which allows for portable and field applications. These devices provide information about the system composition in real-time by combining a chemically selective layer with an electrochemical transducer. Thereby, the chemical energy of the specific interaction between the chemical substances and the sensor is converted into an analytically useful signal.
Herein we demonstrate the electrochemical sensor based on boron-doped diamond/graphene nanowall electrodes (B:DGNW). A B:DGNW electrode is a hybrid electrode, which combines the extraordinary features of boron-doped diamond and a graphene nanowall on the same surface. B:DGNW is a sp2
-rich phase material with multilayered graphene walls oriented vertically to the substrate. Moreover, the presence of the boron-doped diamond phase enhances the electrochemical performance and kinetics of the electrode surface when compared with typical carbon nanowalls. The electrodes were fabricated in a one-step growth process using chemical vapor deposition without any additional modifications (thin films were grown on (100)-oriented silicon substrates).
Two different sensing platforms will be presented: i) impedimetric biosensor for detection of pathogenic bacteria (e.g., Haemophilus influenzae), and ii) voltammetric sensor for determination of important nitroaromatic explosive compounds (2,4,6-trinitrotoluene (TNT), 2,4,6-trinitroanisole (TNA), 4,4',5,5'-tetranitro-1H,1'H-2,2'-biimidazole (TNBI)). The proposed B:DGNW electrodes were revealed to have a high electroactive area towards the voltammetric detection of various nitroaromatic compounds.
The biosensor platform was obtained by B:DGNW surface functionalization firstly by electrografting of diazonium salt and secondly by the attachment of antibodies. The electrochemical biosensor shows high sensitivity and selectivity towards Haemophilus influenzae. The measurements were conducted in the presence of three non-target pathogens S. pyogenes, S. pneumoniae, and B. parapertussis.

The proposed B:DGNW nonmodified carbon electrodes were revealed to have a high electroactive area towards the voltammetric determination of various nitroaromatic compounds, thus appearing to be an attractive nanocarbon surface for further applications. The B:DGNW electrode exhibits high sensing performance for TNT detection with linearity between 0.05 to 2 ppm and 4 to 15 ppm, and a limit of detection (LOD) of 73 ppb. The LOD for 2,4,6-trinitroanisole, in turn, is equal to 0.27 ppm, whereas the limit of detection of TNBI is equal to 0.52 ppm. To the authors' knowledge, this is the first time B:DGNW has been used to detect the nitroaromatic compounds electrochemically [1].
Acknowledgment
This work was supported by the Science for Peace Programme of NATO [Grant no. G5147], Polish National Science Centre [2016/22/E/ST7/00102], and the National Centre for Science and Development [347324/12/NCBR/2017]. The DS funds of the Faculty of Electronics, Telecommunications, and Informatics of the Gdansk University of Technology are also acknowledged.
Reference:
[1] A. Dettlaff et al., J. Hazard. Mater [In press]. Doi: 10.1016/j.jhazmat.2019.121672.