Graphene-enhanced metal oxide gas sensors at room temperature: a review

Abstract

Owing to the excellent sensitivity to gases, metal-oxide semiconductors (MOS) are widely used as materials for gas sensing. Usually, MOS gas sensors have some common shortages, such as relatively poor selectivity and high operating temperature. Graphene has drawn much attention as a gas sensing material in recent years because it can even work at room temperature, which reduces power consumption. However, the low sensitivity and long recovery time of the graphene-based sensors limit its further development. The combination of metal-oxide semiconductors and graphene may significantly improve the sensing performance, especially the selectivity and response/recovery rate at room temperature. In this review, we have summarized the latest progress of graphene/metal-oxide gas sensors for the detection of NO2, NH3, CO and some volatile organic compounds (VOCs) at room temperature. Meanwhile, the sensing performance and sensing mechanism of the sensors are discussed. The improved experimental schemes are raised and the critical research directions of graphene/metal-oxide sensors in the future are proposed.

Graphene derivative coated QCM-based gas sensor for volatile organic compound (VOC) detection at room temperature

“…Among these sensing materials, graphene has attracted the research community due to its unique properties at room temperature for instance, large surface area (2630 m 2 g −1 ) for molecular adsorption, outstanding thermal (~5000 W.m -1 .k -1 ) and electrical conductivity (up to 6000 S.cm -1 ) and high carrier mobility of 1.5 × 10 5 cm 2 /Vs [12]. Apart from graphene, the graphene derivative like reduced graphene oxide (rGO) is also being explored for gas sensing applications owing to its facile preparation and novel applications for gas molecule detection [13,14]. Many gas sensors based on rGO have been recently reported for the detection of various gases, such as CH4, H2, CO2, CO, NO2, NH3, and H2S [12,[15][16][17][18].…”

Metal Oxide Gas Sensors by Nanostructures

“…In general, incorporation of C-based material into MO structure, n-type to p-type convert or p-n junction are observed so active sites available for gas adsorption and formation desired depletion layer [36].…”

“…Graphene-ZnO 17.4 (100 ppm) 1.25 (10 ppm) 23.5 (1 ppm) [36][37][38] Graphene-SnO 2 2.45 (20 ppm) 1.9 (500 ppm) 9 (400 ppm) [39][40][41] Graphene-TiO 2 -1.7 (10 ppm) 6.5 (100 ppm) [42,43] MWCNT-ZnO 1.025 (10 ppm) 41 (10 ppm) - [44,45] MWCNT-SnO 2 2 (10 ppm) 1.06 (60 ppm) 0 (100 ppm) [39,46,47] MWCNT-TiO 2 -2 (100 ppm) 7 (50 ppm) [48,49] SWCNT-ZnO 6 (250 ppm) -0 (50 ppm) [50,51] SWCNT-SnO 2 11.1 (10 ppm) 50 (100 ppm) 1.29 (50 ppm) [52][53][54] SWCNT-TiO 2 ---- Table 1.…”

Synthesis and acetone sensing properties of ZnFe2O4/rGO gas sensors

“…First, the sensing mechanism is based on the mentioned reaction at the gas-solid interface. Second, an appropriate content of rGO can improve the electron mobility inside the composites, which is helpful for the interface reaction [24,51]. Third, as shown in Figure 11a, the Fermi energy levels equalize when two semiconducting systems are in contact via the transfer of carriers.…”

“…Plenty of works are in progress to investigate the applications of graphene or its derivatives in the field of gas sensing [20,21], including room temperature CO 2 gas sensors and room temperature double-layer graphene NO 2 gas sensors prepared by deposition processes [22,23]. Furthermore, the combination of metal oxides with graphene or its derivatives can enhance the gas sensing capability by improving the adsorption/desorption ability of the incorporated molecules, the transfer of carriers and the formation of local heterojunctions [24][25][26][27][28]. An optimum ratio of the composition and the fine nanostructure will contribute to obtaining better gas-sensing properties.…”