Electrochemical Sensing of 2,4-Dinitrotoluene on Boron-Doped Carbon Nanowall Electrodes in Seawater
Authors: Kaczmarzyk Iwona , Walczak Juliusz , Sobaszek Michal , Dettlaff Anna 
Published: September 2023

50 000 tons of chemical weapons and 500 000 tons of conventional weapons, containing nitroexplosive compounds such as 2,4,6-trinitrotoluene (TNT) have been dumped in the Baltic Sea since the end of World War II. In addition, many wrecks from World War II are still laying at the bottom of the Baltic Sea. The marine environment, due to the content of chloride ions, shows high corrosion aggressiveness. As a result, the degradation of metal ammunition casings, fuel tanks and other metal elements causes the successive release of toxic substances into the ecosystem. Uncontrolled emission of those chemicals hinders the development of biological life and poisons fish living in the sea, which later as food posing a real threat to human health.

TNT is a highly energetic material commonly utilized as a filling of shell casting and mines, thus it is used in large quantities in armed conflicts. 2,4-dinitrotoluene (2,4-DNT) is the decomposition product of TNT and has a similar structure (2,4-DNT has two nitro groups (-NO2) and TNT three). Exposure to high 2,4-DNT concentrations may cause lung and liver complications as well as reproductive problems. 2,4-DNT is spread all over the world and is found in air, surface water, groundwater, and soil [1]. Therefore, environmental monitoring of DNT using an effective sensor is essential. The development of DNT sensors able to effectively work in marine water with the required sensitivity is extremely necessary and remains a challenge.

Carbon nanomaterials have been used in various fields, such as electronic, optoelectronic, photovoltaic, and electrochemical applications, owing to their excellent electrical, electrochemical and mechanical properties. Boron-doped carbon nanowall (B:CNW) electrodes are characterized by excellent charge transfer and compared to for example boron-doped diamond electrodes exhibit highly developed active surface area [2]. Moreover, these electrodes showed a sensitive and selective response to nitroaromatic compounds, such as TNT and 2,4,6-trinitroanisole (TNA) [3].

In this study, we propose a 2,4-DNT electrochemical sensor based on a boron-doped carbon nanowall electrode prepared in a one-step process using a chemical vapor deposition technique. The determination of 2,4-dinitrotoluene was performed using differential pulses voltammetry (DPV) and cyclic voltammetry (CV) in saline water matrices on B:CNW electrodes, using a three-electrode setup. The objective of this work is to test the influence of water salinity level on the 2,4-dinitrotoluene detection sensitivity. For this purpose, water containing various levels of salinity (from 2 – 20 ‰) was investigated. Furthermore, real-sample measurements were conducted using the Baltic See water from the Gulf of Gdansk. The levels of salinity were selected based on average salinity of the Baltic Sea (7.5‰).

Literature:

[1] D. E. Rickert, et al., CRC Critical Reviews in Toxicology. (1984) 13:3 217-234

[2] M. Sobaszek, et al., J. Phys. Chem. C. 121 (2017) 20821–20833

[3] A. Dettlaff, et al., J. Hazard. Mater. 387 (2020) 121672

Acknowledgements:

The research leading to these results has received funding from the Norway Grants 2014-2021 via the National Centre for Research and Development within research grant no. NOR/SGS/NITROsens/0011/2020-00.