Selective N,N-Dimethylformamide Vapor Sensing Using MoSe2/Multiwalled Carbon Nanotube Composites at Room Temperature

ACS Appl. Mater. Interfaces

Chen

Xuan

et al. 2022

Self Cite

Continuous detection of toxic and hazardous gases like nitric oxide (NO) and ammonia (NH3) is needed for environmental management and noninvasive diagnosis of various diseases. However, to the best of our knowledge, dual detection of these two gases has not been previously reported. To address the challenge, we demonstrate the design and fabrication of low-cost NH3 and NO dual gas sensors using tungsten disulfide/multiwall carbon nanotube (WS2/MWCNT) nanocomposites as sensing channels which maintained their performance in a humid environment. The composite-based device has shown successful dual detection at temperatures down to 18 °C and relative humidity of 90%. For 0.1 ppm ammonia, it exhibited a p-type conduction with response and recovery times of 102 and 261 s, respectively; on the other hand, with NO (10 ppb, n-type), these times were 285 and 198 s, respectively. The device with 5 mg MWCNTs possesses a superior selectivity along with a relative response of ≈7% (5 ppb) and ≈5% (0.1 ppm) for NO and NH3, respectively, at 18 °C. The response is less affected by relative humidity, and this is attributed to the presence of MWCNTs that are hydrophobic in nature. Upon simultaneous exposure to NO (5–10 ppb) and NH3 (0.1–5 ppm), the response was dominated by NO, implying clear discrimination to the simultaneous presence of these two gases. We propose a sensing mechanism based on adsorption/desportion and accompanied charge transfer between the adsorbed gas molecules and sensing surface. The results suggest that an optimized weight ratio of WS2 and MWCNTs could govern favorable sensing conditions for a particular gas molecule.

Section: Resultsmentioning

confidence: 72%

Section: ■ Experimental Sectionmentioning

confidence: 63%

Humidity-Tolerant Room-Temperature Selective Dual Sensing and Discrimination of NH₃ and NO Using a WS₂/MWCNT Composite

ACS Appl. Mater. Interfaces

Chen

Xuan

et al. 2022

Self Cite

“…Panels b and d give corresponding relative responses for these RH levels, respectively. The Freundlich isotherm model can be used to represent the relationship between sensing response and gas concentration ( C ) in ppm. , The obtained experimental data can be described using a regression equation of sensing response (Δ R / R a %) = A × C b with satisfactory coefficients of R 2 = 0.98 and 0.97 for RH = 40% ( A = 17.7, b = 0.15) and 60% ( A = 10, b = 0.22). Response variation and consistency are two critical factors in the design of practical sensor systems.…”

Section: Resultsmentioning

confidence: 99%

“…Note that same name was assigned to two-terminal devices that were obtained from the respective composite. The procedure for making sensor devices has been described elsewhere. , In brief, the paste obtained after mixing 0.5 mg of composite with DI water was applied on an alumina substrate with predeposited gold contacts and a separation close to 2 mm. After a drying process in a vacuum oven at 80 °C for 6 h, the devices were ready for electrical measurements.…”

Section: Experimental Sectionmentioning

confidence: 99%

Highly Selective Ethyl Mercaptan Sensing Using a MoSe₂/SnO₂ Composite at Room Temperature

Deb

ACS Appl. Mater. Interfaces

et al. 2022

Self Cite

Volatile organic sulfur compounds (VOSCs) serve not only as biomarkers for dental diseases such as halitosis but also as a tracer for monitoring air quality. Room-temperature selective detection and superior sensitivity against VOSCs at a sub-ppm level has remained a challenging task. Here, we propose a heterostructure-based design using a MoSe 2 /SnO 2 composite for achieving sensitive and selective detection of ethyl mercaptan at room temperature. The composite was synthesized via a facile two-step method. A composite-based device has shown detection down to 1 ppm of ethyl mercaptan over a wider range of relative humidity (40−90%). Notably, the composite has shown adsorption selectivity toward ethyl mercaptan compared to hydrogen sulfide and other reducing or oxidizing analytes. Moreover, a density functional theory (DFT) study has been performed to understand the adsorption selectivity, charge transfer, and modification in the electronic properties after molecule adsorption on the host surface. Simulations predicted the lowest negative adsorption energy for ethyl mercaptan, implying the chemisorption (−142.029 kJ mol −1 ) process of adsorption. The device thus-obtained has also shown a stable response even at an extreme relative humidity level of 90%. The obtained results and superior signal-to-noise ratio indicate that a MoSe 2 /SnO 2 -based sensor may be a promising candidate for highly selective and sensitive detection of ethyl mercaptan even below 1 ppm.

“…These VOC gases degrade air quality and even destroy the ozone layer. At the same time, these gases threaten human body [1][2][3]. For example, ethanol exists in laboratories, medical industries, and industrial production.…”

Section: Introductionmentioning

confidence: 99%

NiO-Based Gas Sensors for Ethanol Detection: Recent Progress

Zeng

2022

Journal of Sensors

In this review, we summarized the state-of-the-art progress on the ethanol performance of NiO by means of morphology, doping, loading noble metal particles, and forming heterojunctions. We first introduced the effect of modulating NiO morphology on ethanol performance that has been reported in recent years. The morphology with large specific surface area and high porosity was considered to be the one that can bring high gas response. Then, we discussed the enhanced effect of the doping of metal cations and noble metal particle loading on the ethanol-sensitive properties of NiO. Doping ions increased the ground-state resistance and increased the oxygen defect concentration of NiO. The effects of noble metal particles on the performance of NiO included chemical sensitization and electronic sensitization. Finally, the related contents of NiO forming complexes with metal oxides and bimetallic oxides were discussed. In this section, the specific improvement mechanism was discussed first, and then, the related work of researchers in recent years was summarized. At the same time, we presented a reasonable outlook for NiO-based ethanol sensors, imagining future directions.