Highly Sensitive Room-Temperature NO₂ Gas Sensors Based on Three-Dimensional Multiwalled Carbon Nanotube Networks on SiO₂ Nanospheres

Abstract

The electrical conductivity of carbon nanotubes (CNTs) has been demonstrated to be highly sensitive to the change of vapor/gas molecules in the local environment owing to the large specific surface area and quantum size effect, which enable CNTs to be an ideal sensing material for next-generation room-temperature gas sensors. However, the sensing properties of CNT films or networks cannot be maximized because of the inevitable agglomeration during the fabrication process. Herein, three-dimensional (3D) SiO2@multiwalled CNTs (MWCNTs) core–shell nanospheres have been first used to fabricate room-temperature gas sensors, which were prepared using an electrostatic self-assembly method. The as-fabricated 3D SiO2@MWCNTs sensor exhibits a recorded sensitivity of 82.61% toward 1 ppm nitrogen dioxide (NO2) at room temperature, which is 1.97 times higher than that of devices based on random two-dimensional (2D) MWCNTs. Meanwhile, the recovery time of ∼44 s is smaller than that of a 2D MWCNT gas sensor. Such an ultrahigh sensing performance is attributed to an effective utilization of the large specific surface area of MWCNT networks with 3D structures. We believe that our findings will contribute to the further development of high-performance CNT-based sensing devices and also provide a new approach to fabricate the sensing devices using one-dimensional nanomaterials.

Ultrasensitive, Transparent, Flexible, and Ecofriendly NO2 Gas Sensors Enabled by Oxidized Single-Walled Carbon Nanotube Bundles on Cellulose with Engineered Surface Roughness

“…It should be emphasized that ecofriendly cellulose with engineered surface roughness is better than hard silicon as a NO 2 sensing template. Although our sensors exhibited low recovery characteristics, supplying extra energy with UV or heat can enhance sensor recovery as demonstrated in the previous results. ,, …”

“…However, combining these materials needs a complicated process to optimize their morphology and structure. Also, the resistance and operating temperature of the devices were typically increasing so that they lost the merits of CNTs. − Introducing nanoparticles or control of surface energy and morphology in the supporting substrate has been applied to increase the adsorption of target gas molecules for enhanced gas response. − In addition, attaching functional groups onto the CNTs by defect engineering can increase their binding affinity with target gas molecules . However, the functionalization, such as oxidation, inevitably decreases the electrical properties of CNTs, which is undesirable for sensor response.…”

Recent Progress in Gas Sensor Based on Nanomaterials

“…The recording sensitivity of carbon nanotubes-based gas sensors to nitrogen dioxide at room temperature is 1.97 times higher than that of random equipment of the same dimension, which is due to the use of the specific surface area of a carbon nanotube network, and it dramatically enhances the sensing performance. Ma Defu's studies demonstrate a visible-light-driven room temperature gas sensor made of novel carbide nanocrystals [2]. The fluorescence emission of carbide nanocrystals has been attributed to light-driven sensing.…”

Zinc stannate microcubes with an integrated microheater for low-temperature NO2 detection

“…[13][14][15] Other reported methods include substitutional doping, the formation of composites and hybrids with other nanomaterials, such as metal oxides, 2D materials, carbon nanotubes, and so on, as well as chemical functionalization with noble metal nanoparticles. For example, Ma et al 16 reported 3D SiO 2 @MWCNT core-shell nanospheres for the highly sensitive detection of nitrogen dioxide gas (NO 2 ) at room temperature, with a maximum sensitivity of 82.61%. The response time was observed to be 25 min, and they used UV illumination to achieve complete recovery (44 s).…”