Citation: Lama, S.; Bae, B.-G.;
Ramesh, S.; Lee, Y.-J.; Kim, N.; Kim,
J.-H. Nano-Sheet-like Morphology of
Nitrogen-Doped Graphene-Oxide
-Grafted Manganese Oxide and
Polypyrrole Composite for Chemical
Warfare Agent Simulant Detection.
Nanomaterials 2022, 12, 2965.
https://doi.org/10.3390/
nano12172965
Academic Editor: Li Hai
Received: 21 July 2022
Accepted: 22 August 2022
Published: 27 August 2022
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Article
Nano-Sheet-like Morphology of Nitrogen-Doped
Graphene-Oxide-Grafted Manganese Oxide and Polypyrrole
Composite for Chemical Warfare Agent Simulant Detection
Sanjeeb Lama
1
, Bong-Gyu Bae
1
, Sivalingam Ramesh
2
, Young-Jun Lee
1
, Namjin Kim
3
and Joo-Hyung Kim
1,
*
1
Laboratory of Intelligent Devices and Thermal Control, Department of Mechanical Engineering,
Inha University, Incheon 22212, Korea
2
Department of Mechanical, Robotics and Energy Engineering, Dongguk University, Seoul 04620, Korea
3
Department of Mechanical Engineering, Jeju National University, Jeju 63243, Korea
* Correspondence: joohyung.kim@inha.ac.kr
Abstract:
Chemical warfare agents (CWAs) have inflicted monumental damage to human lives from
World War I to modern warfare in the form of armed conflict, terrorist attacks, and civil wars. Is
it possible to detect the CWAs early and prevent the loss of human lives? To answer this research
question, we synthesized hybrid composite materials to sense CWAs using hydrothermal and thermal
reduction processes. The synthesized hybrid composite materials were evaluated with quartz crystal
microbalance (QCM) and surface acoustic wave (SAW) sensors as detectors. The main findings
from this study are: (1) For a low dimethyl methyl phosphonate (DMMP) concentration of 25 ppm,
manganese dioxide nitrogen-doped graphene oxide (NGO@MnO
2
) and NGO@MnO
2
/Polypyrrole
(PPy) showed the sensitivities of 7 and 51 Hz for the QCM sensor and 146 and 98 Hz for the
SAW sensor. (2) NGO@MnO
2
and NGO@MnO
2
/PPy showed sensitivities of more than 50-fold
in the QCM sensor and 100-fold in the SAW sensor between DMMP and potential interferences.
(3) NGO@MnO
2
and NGO@MnO
2
/PPy showed coefficients of determination (R
2
) of 0.992 and 0.975
for the QCM sensor and 0.979 and 0.989 for the SAW sensor. (4) NGO@MnO
2
and NGO@MnO
2
/PPy
showed repeatability of 7.00
±
0.55 and 47.29
±
2.69 Hz in the QCM sensor and 656.37
±
73.96 and
665.83
±
77.50 Hz in the SAW sensor. Based on these unique findings, we propose NGO@MnO
2
and
NGO@MnO
2
/PPy as potential candidate materials that could be used to detect CWAs.
Keywords:
chemical warfare agents (CWAs); quartz crystal microbalance (QCM); surface acoustic
wave (SAW); dimethyl methyl phosphonate (DMMP); volatile compounds (VOCs)
1. Introduction
Chemical warfare agents (CWAs) are considered extremely lethal weapons that have
the potential to cause mass destruction [
1
]. The CWA attacks on the Tokyo subway (1995) [
2
]
and the Syrian civil war (2013) [
3
] demonstrated to the world the ramifications of the misuse
of CWAs. Based on this, we understand that the early detection of CWAs is crucial for
preventing the loss of human lives. Figure S1 shows the chemical structure of G-series nerve
agents, such as sarin (GB series), soman (GD series), Tabun (GA series), and simulant DMMP.
For many years, detection technologies have been suggested and developed to detect
CWAs. Some of these include gas chromatography, Raman spectroscopy, Fourier-Transform
Infrared Spectroscopy, atomic emission detection, and ion mobility spectroscopy [
4
,
5
]. This
equipment is used for the detection of both CWAs and their simulants, and it is accurate,
precise, and reliable.
However, this equipment has crucial problems when used in field monitoring of
CWAs. For practical purposes, it is important to detect CWAs in the field. For the field
monitoring and detection of CWAs, devices with less power consumption, high accuracy,
portability, reliability, inexpensive manufacturing and maintenance costs, and stability
Nanomaterials 2022, 12, 2965. https://doi.org/10.3390/nano12172965 https://www.mdpi.com/journal/nanomaterials
