Ultrasensitive Room-Temperature NO₂ Detection Using SnS₂/MWCNT Composites and Accelerated Recovery Kinetics by UV Activation

Abstract

High performance with lower power consumption is one among the essential features of a sensing device. Minute traces of hazardous gases such as NO2 are difficult to detect. Tin disulfide (SnS2) nanosheets have emerged as a promising NO2 sensor. However, their poor room-temperature conductivity gives rise to inferior sensitivity and sluggish recovery rates, thereby hindering their applications. To mitigate this problem, we present a low-cost ultrasensitive NO2 gas sensor with tin disulfide/multiwalled carbon nanotube (SnS2/MWCNT) nanocomposites, prepared using a single-step hydrothermal method, as sensing elements. Relative to pure SnS2, the conductivity of nanocomposites improved significantly. The sensor displayed a decrease in resistance when exposed to NO2, an oxidizing gas, and exhibited p-type conduction, also confirmed in separate Mott–Schottky measurements. At a temperature of 20 °C, the sensor device has a relative response of about ≈5% (3%) for 25 ppb (1 ppb) of NO2 with complete recovery in air (10 min) and excellent recovery rates with UV activation (0.3 min). A theoretical lower limit of detection (LOD) of 7 ppt implies greater sensitivity than all previously reported SnS2-based gas sensors, to the best of our knowledge. The improved sensing characteristics were attributed to the formation of nano p–n heterojunctions, which enhances the charge transport and gives rise to faster response. The composite sensor also demonstrated good NO2 selectivity against a variety of oxidizing and reducing gases, as well as excellent stability and long-term durability. This work will provide a fresh perspective on SnS2-based composite materials for practical gas sensors.

Nanocomposites of Quasicrystal Nanosheets and MoS2 Nanoflakes for NO2 Gas Sensors

“…The specific surface area is an important parameter that affects the adsorption properties of sensing materials . To understand these properties, a BET analysis of nitrogen physisorption study was done on the MoS 2 and MoS 2 :2D-QC samples.…”

“…The specific surface area is an important parameter that affects the adsorption properties of sensing materials. 58 To understand these properties, a BET analysis of nitrogen physisorption study was done on the MoS NO 2 sensing measurement suggests that as-synthesized MoS 2 behaves as a p-type semiconductor (Figure 5a), and the resistance of the sensor deceased during the NO 2 (oxidizing gas) exposure. 4 Figure 4b Figure 5d shows the comparison in response to bare MoS 2 and MoS 2 :2D-QC sensors and found that the composite sensor response is 2.27 times larger than that of the bare sensor.…”

Detection of DMF and NH3 at Room Temperature Using a Sensor Based on a MoS2/Single-Walled Carbon Nanotube Composite

“…Furthermore, the high concentration of SWCNTs significantly increases the composite’s effective conductivity, masking the gas-induced change in conductivity. This can clearly decrease the sensor response, which relies on changes in conductivity due to gas adsorption on MoS 2 . , The MoS 2 –SW20 sensor’s higher response could be attributed to its high specific surface area, high charge carrier density, the presence of defects, and synergistic effects that occur when a heterostructure is formed. ,, As a result, all subsequent DMF sensing measurements were performed using the MoS 2 –SW20 sensor. For the sake of comparison, response transients for the SWCNT-based device toward 5 ppm of DMF and NH 3 are also included in Figure S6.…”

“…The current–voltage ( I – V ) measurements were conducted using a Keithley SourceMeter (2612A). The sensing measurements were performed under ambient humidity conditions over a large span of time. , The sensor characterization was conducted with the lab-built static setup described in previous reports ,, and briefly discussed in the Supporting Information.…”

Functionalized Multiwalled Carbon Nanotubes for Highly Stable Room Temperature and Humidity-Tolerant Triethylamine Sensing

“…After the sensing layer was applied, the sensor was dried in a vacuum oven at 80 °C for 10 h. A digital photograph of the two-terminal sensor device (1 cm × 1 cm) is shown in Figure S2. Sensing tests were performed using a homemade setup described in detail in other studies. , All gas-sensing tests were conducted at room temperature (20 ± 5 °C) and natural relative humidity levels over a long period of time. , The relative humidity (RH) of the experiment (40–80% RH) under a normal atmospheric environment was recorded during the sensing tests. In daily life, various stable RH conditions with a ±5% variation can be monitored .…”