Highly Efficient Response of Ammonia Gas Sensor Based on Surfactant‐Free Sorted‐Semiconducting Single‐Walled Carbon Nanotubes at Room Temperature

Abstract

A comparative analysis of sorted semiconducting (sc‐) single‐walled carbon nanotubes (SWCNTs) films, metallic (m‐) SWCNTs films, pristine SWCNTs films, and graphene‐based simple two‐terminal sensors for the applications of ammonia gas sensing is presented. The comparison of the sensing response of different devices by separately measuring the SWCNTs film resistance and the contact resistance between SWCNTs and the electrodes reveals that the performance mainly relies on the modification of tube conductivity under exposure to gas. Moreover, the measurements show that the highest sensitivity of the devices is achieved by use of sc‐SWCNTs as the conducting channels. Sensor coated with surfactant‐free sc‐SWCNTs shows a sensitivity of 0.78% ppm at 5–100 ppm ammonia (NH3) concentrations that happened to be ≈28, ≈22, and ≈173 times more sensitive than pristine‐SWCNTs, m‐SWCNTs, and graphene‐based sensors, respectively, at 50 ppm and ≈4.5 times the previously reported sc‐SWCNTs‐based sensor at 5 ppm. Notably, all the experiments values are achieved at room temperature without any extra heating treatment for the recovery process. These results show that surfactant‐free sc‐SWCNTs provide a promising way of creating sensors with improved selectivity and sensitivity, which predicts the auspicious prospects in the development of future applications.

NH3 Gas Sensors Based on Single-Walled Carbon Nanotubes Interlocked with Metal-Tethered Tetragonal Nanobrackets

“…In contrast, the pristine SWNT sensors responded comparably to NH 3 (2 ppm) and the other analytes (200 ppm). This lack of selectivity is consistent with the recently reported results for semiconductor-enriched SWNT sensors . Therefore, the high selectivity of the M-NB–SWNT sensor for NH 3 can be ascribed to the interlocking M-NB moieties.…”

“…This lack of selectivity is consistent with the recently reported results for semiconductor-enriched SWNT sensors. 11 Therefore, the high selectivity of the M-NB−SWNT sensor for NH 3 can be ascribed to the interlocking M-NB moieties.…”

“…Since SWNTs exhibit either semiconducting or metallic properties, depending on their structure, semiconductor-enriched SWNT networks demonstrate a higher sensitivity to NH 3 because the gas response is primarily attributed to their semiconducting properties. 11 However, nonfunctionalized CNTs are not selective to NH 3 at room temperature. 11 Decorating CNTs with functional materials is an effective way to improve the sensitivity and selectivity of CNT-based sensors for specific gas species by changing the interactions between the materials and CNTs.…”

“…11 However, nonfunctionalized CNTs are not selective to NH 3 at room temperature. 11 Decorating CNTs with functional materials is an effective way to improve the sensitivity and selectivity of CNT-based sensors for specific gas species by changing the interactions between the materials and CNTs. 3,7 Various metal nanoparticles, 12 metal oxides, 13,14 organic molecules, 15−21 and polymers 22 have been investigated as enhancers and selectors decorating on or forming composites with CNTs to improve NH 3 sensing properties.…”

Gas Sensors Based on Single-Wall Carbon Nanotubes

“…A sensitivity improvement of ~21 to 76% in the 20–80 ppm NO 2 concentration range was observed in the case of aligned s-SWCNT devices compared to the random network-based sensors. Thereafter, a sorted high concentration of s-SWCNTs has been used extensively as a sensing material [ 88 , 89 , 90 , 91 , 92 ]. Specifically, a floating gate FET-structured sensor constructed using a high-purity network film of s-SWCNTs decorated with Pd nanoparticles as the channel [ 88 ], showed a record LOD of 90 ppb at room temperature and even reached the sub ppb level at higher temperatures.…”