Coupling two-dimensional transition metal dichalcogenides (TMDs) with semiconductor metal oxides (SMOs) having adjustable characteristics has increased gas detection and overall system effectiveness. In a paper published in the journal ACS Applied Nano Materials, the development of an incredibly sensitive chemiresistor built on a Co3O4/MoS2 nanoscale structure was described.
Study: Co3O4/MoS2 Nanostructures for NOx Sensing. Image Credit: Toa55/Shutterstock.com
2D-TMD/SMO Hybrids
After graphene, two-dimensional transition metal dichalcogenides (TMDs) are by far the most investigated two-dimensional materials, with uses in a wide range of sectors, including gas detection, energy collection, optoelectronics, water splitting, health bio-indicators, and more.
Semiconducting metal oxide (SMO) gas detectors are becoming increasingly popular. Due to their size-reliant and adjustable features, including chemical, catalytic, electrical, mechanical, optical, and magnetic capabilities, these substances are often employed for gas detection.
Compared to isolated materials, combinations of two-dimensional TMDs and SMOs are an exciting topic of study. MoS2 flakes contain free-hanging bonds on the surface, facilitating oxide material development minus the difficulty of lattice mismatching.
The most significant benefit of producing hybridized nanostructures is that the creation of a heterojunction (p-p, n-p, or n-n) at the boundary connecting the two components improves gas detection capability.
Oxides of Nitrogen – A Menace to Human Health
Nitric oxide (NO) and nitrogen dioxide (NO2) are extremely harmful lung-irritating chemicals that may induce greater airway swelling, resulting in decreased pulmonary functioning. Prolonged exposure to these chemicals may also induce alterations in the mind's computational abilities and cardiac disorders, which may ultimately lead to death.
Nitrogen dioxide gas discharge from trucks and buses, cars, and treated gases from industrial sectors are significant contributors. As a result, specific detection of nitrogen dioxide gas is important, especially at small concentration levels.
Layered Inorganic Materials for Effective Gas Sensors
There is a growing need for effective gas detection with improved specificity, responsiveness, and robustness, as well as those that can function at reduced temperatures and are inexpensive. Since detecting materials is critical to gas detectors' effective functioning, much research aims to develop more appropriate materials with improved qualities.
TMDs, layered SMOs, and other stacked inorganic detection substances have garnered interest owing to their thickness-reliant chemical and physical characteristics.
Along with a high surface/volume ratio, these substances exhibit semiconductive capabilities with a configurable band gap, which is required to modify the transportation parameters and improve sensory effectiveness.
Highlights of the Research
In this paper, the team investigated the outstanding gas detection capability of 2D TMD/SMO (Co3O4/MoS2) hybridized nanostructures. The impact of precursor content and temperature on hybridized sensory effectiveness was analyzed.
The gas detector with the greatest precursor content had the highest response, as well as being the most stable.
The working temperature was increased in 50°C increments from 50 to 300°C. The findings showed that the gas detector had outstanding properties and response at a temperature of 250°C and was very responsive to NOx pollutants. Ammonia, carbon monoxide, hydrogen sulfide, and ethanol were also detectable by the device.
The sensor had the maximum response to nitrogen dioxide at 250°C, equal to 186.2 percent, with a minimal hysteresis error of 0.84 percent.
The device also reacted adequately to nitrogen dioxide, even at small concentrations of 50 ppb. This significant response, minimal hysteresis error, small activating energy, and faster response (on) and recovering (off) periods suggest that hybrid nanostructures of Co3O4/MoS2 at 25 mM concentration of the precursor are ideal detecting materials for nitrogen dioxide gas sensing at 250 °C.
It was also discovered that the developed nanostructure-based gas detectors with a precursor content of 25 mM could work effectively at lower temperatures down to 50 °C as well, in comparison with other gas detectors.
Advantages of Co3O4/MoS2 Hybridized Nanostructures
These findings point to various benefits of employing fused Co3O4/MoS2 nanostructures. Increased Co3O4 precursor content resulted in gas detectors with greater stability and efficiency.
By detecting NOX gases at smaller temperatures of about 50°C, the system demonstrated considerable promise in areas requiring low working temperatures. By measuring NOX at the ppb scale, the gadget demonstrated outstanding effectiveness even at increased working temperatures.
Reference
Fathima, N., Jha, R. K., & Bhat, N. (2022). Co3O4/MoS2 Nanostructures for NOx Sensing. ACS Applied Nano Materials. Available at: https://pubs.acs.org/doi/10.1021/acsanm.2c00736
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