Nanostructured materials synthesized by the hydrothermal and thermal reduction process were tested to detect the dimethyl methylphosphonate (DMMP) as a simulant for chemical warfare agents. Manganese oxide nitrogen-doped graphene oxide with polypyrrole (MnO2@NGO/PPy) exhibited the sensitivity of 51 Hz for 25 ppm of DMMP and showed the selectivity of 1.26 Hz/ppm. Nitrogen-doped multi-walled carbon nanotube (N-MWCNT) demonstrated good linearity with a correlation coefficient of 0.997. A comparison between a surface acoustic wave and quartz crystal microbalance sensor exhibited more than 100-times higher sensitivity of SAW sensor than QCM sensor.

Summary Co3O4/RuO2@nitrogen‐doped graphene oxide (NGO) composite materials were synthesized through a sonication‐assisted thermal reduction method in the presence of cobalt and ruthenium starting reagents for supercapacitor and gas sensor applications. The composite materials were characterized using various analytical tools to confirm the structural and morphological properties. The synthesized Co3O4/RuO2@NGO composites showed the nanostructured grains anchored on the NGO surface. The electrochemical storage performance was studied by using cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy using a two‐electrode asymmetric configuration. The prepared Co3O4/RuO2@NGO electrode exhibited a maximum capacitance of ~149 F/g at an applied current of ~0.5 A/g, an energy density of 20.69 Wh kg−1, and at a power density of 250 W kg−1. The cycling behavior of the fabricated asymmetric capacitor revealed a 90% capacitance retention after 5000 cycles. Moreover, the prepared composite material was used successfully for dimethyl methylophosphonate (DMMP) vapor detection, showing excellent sensitivity, selectivity, and stability. Therefore, the constructed Co3O4/RuO2@NGO composite is a suitable material for supercapacitors and DMMP gas‐detection applications.

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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@MnO2) and NGO@MnO2/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@MnO2 and NGO@MnO2/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@MnO2 and NGO@MnO2/PPy showed coefficients of determination (R2) of 0.992 and 0.975 for the QCM sensor and 0.979 and 0.989 for the SAW sensor. (4) NGO@MnO2 and NGO@MnO2/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@MnO2 and NGO@MnO2/PPy as potential candidate materials that could be used to detect CWAs.

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