Abstract:Adsorption-induced change of carrier density is presently dominating inorganic semiconductor gas sensing, which is usually operated at a high temperature. Besides carrier density, other carrier characteristics might also play a critical role in gas sensing. Here, we show that carrier mobility can be an efficient parameter to dominate gas sensing, by which room-temperature gas sensing of inorganic semiconductors is realized via a carrier mobility-dominated gas-sensing (CMDGS) mode. To demonstrate CMDGS, we desi… Show more
“…Recently, 3D hierarchical structures have been extremely appealing due to their unique structures and better gas sensing performance than 1D and 2D materials [4,5,6]. Meanwhile, metal oxide (MO) materials gas sensors, such as ZnO [7,8,9], CuO [10,11], In 2 O 3 [12,13], WO 3 [14,15], CeO 2 [16], SnO 2 [17,18], etc., have attracted extensive attention. Besides, MO materials exhibit outstanding sensing properties in the detection of H 2 S gas [19,20,21,22].…”
Firecracker-like ZnO hierarchical structures (ZnO HS1) were synthesized by combining electrospinning with hydrothermal methods. Flower-like ZnO hierarchical structures (ZnO HS2) were prepared by a hydrothermal method using ultrasound-treated ZnO nanofibers (ZnO NFs) as raw material which has rarely been reported in previous papers. Scanning electron microscope (SEM) and transmission electron microscope’s (TEM) images clearly indicated the existence of nanoparticles on the ZnO HS2 material. Both gas sensors exhibited high selectivity toward H2S gas over various other gases at 180 °C. The ZnO HS2 gas sensor exhibited higher H2S sensitivity response (50 ppm H2S, 42.298) at 180 °C than ZnO NFs (50 ppm H2S, 9.223) and ZnO HS1 (50 ppm H2S, 17.506) gas sensors. Besides, the ZnO HS2 sensor showed a shorter response time (14 s) compared with the ZnO NFs (25 s) and ZnO HS1 (19 s) gas sensors. The formation diagram of ZnO hierarchical structures and the gas sensing mechanism were evaluated. Apart from the synergistic effect of nanoparticles and nanoflowers, more point–point contacts between flower-like ZnO nanorods were advantageous for the excellent H2S sensing properties of ZnO HS2 material.
“…Recently, 3D hierarchical structures have been extremely appealing due to their unique structures and better gas sensing performance than 1D and 2D materials [4,5,6]. Meanwhile, metal oxide (MO) materials gas sensors, such as ZnO [7,8,9], CuO [10,11], In 2 O 3 [12,13], WO 3 [14,15], CeO 2 [16], SnO 2 [17,18], etc., have attracted extensive attention. Besides, MO materials exhibit outstanding sensing properties in the detection of H 2 S gas [19,20,21,22].…”
Firecracker-like ZnO hierarchical structures (ZnO HS1) were synthesized by combining electrospinning with hydrothermal methods. Flower-like ZnO hierarchical structures (ZnO HS2) were prepared by a hydrothermal method using ultrasound-treated ZnO nanofibers (ZnO NFs) as raw material which has rarely been reported in previous papers. Scanning electron microscope (SEM) and transmission electron microscope’s (TEM) images clearly indicated the existence of nanoparticles on the ZnO HS2 material. Both gas sensors exhibited high selectivity toward H2S gas over various other gases at 180 °C. The ZnO HS2 gas sensor exhibited higher H2S sensitivity response (50 ppm H2S, 42.298) at 180 °C than ZnO NFs (50 ppm H2S, 9.223) and ZnO HS1 (50 ppm H2S, 17.506) gas sensors. Besides, the ZnO HS2 sensor showed a shorter response time (14 s) compared with the ZnO NFs (25 s) and ZnO HS1 (19 s) gas sensors. The formation diagram of ZnO hierarchical structures and the gas sensing mechanism were evaluated. Apart from the synergistic effect of nanoparticles and nanoflowers, more point–point contacts between flower-like ZnO nanorods were advantageous for the excellent H2S sensing properties of ZnO HS2 material.
“…With the requirement of environmental protection and safety, the dangerous, toxic, harmful, flammable and explosive gases need to be detected and regulated, which greatly promoted the development of gas sensor technology. Among many semiconductor materials, tin oxide (SnO 2 ) has been the mainstream of research owing to good chemical stability, fast response/recovery, high sensitivity, low cost and a wide variety of gas responses [1][2][3].…”
In order to investigate function of carrier behavior on gas-sensing properties, tin oxide-based films with different carrier concentration and mobility were obtained, by magnetron sputtering from the powder target, which was followed by further oxygen-management though the annealing treatment. The microstructure, surface morphology, electrical properties and gas sensitivity were characterized by XRD, Raman spectrum, photoluminescence spectrum, atomic force microscope, the hall effect system and electrochemical workstation, respectively. The results showed that all SnO2-based films had a tetragonal rutile phase with (101) preferred orientation. The introduction of fluorine and regulation of oxygen vacancies tuned carrier concentration from 1015/cm3 to 1021/cm3 and mobility from 102 cm2/V·s to 10−1 cm2/V·s. The decreasing carrier concentration as well as increasing mobility had a positively important function to improve the sensitivity of SnO2-based films. The air-annealed SnO2 film with lowest carrier concentration had a maximum sensitivity of R = 5.0, while vacuum-annealed SnO2:F film with the highest carrier concentration being the minimum sensitivity. This puts forward a novel reference for the design and application of SnO2-based gas sensing films.
“…The chemical activity of a gas sensor is rather weak at low operating temperature, which leads to low sensitivity. The desorption rate of gas increases with growing the sensor surface temperature, and at a certain temperature it will exceed the adsorption rate that results in sensitivity drop [40]. Therefore, 200 °C and 400 °C were defined experimentally as the optimum operating temperature for the gas sensing measurement and calcination temperature, respectively.Fig.…”
In this work, the hierarchical tin oxide nanoflowers have been successfully synthesized via a simple hydrothermal method followed by calcination. The as-obtained samples were investigated as a kind of gas sensing material candidate for methanol. A series of examinations has been performed to explore the structure, morphology, element composition, and gas sensing performance of as-synthesized product. The hierarchical tin oxide nanoflowers exhibit sensitivity to 100 ppm methanol and the response is 58, which is ascribed to the hierarchical structure. The response and recovery time are 4 s and 8 s, respectively. Moreover, the as-prepared sensor has a low working temperature of 200 °C which is lower than that for other gas sensors of such type has been reported elsewhere. The excellent sensitivity of the sensor is caused by its complex phase mixture of SnO, SnO
2
, Sn
2
O
3
, and Sn
6
O
4
revealed by XRD analysis. The proposed hierarchical tin oxide nanoflowers gas sensing material is promising for development of methanol gas sensor.
Graphical Abstract
The as-obtained hierarchical tin oxide nanoflower (HTONF) gas sensor shows excellent gas-sensing performance at low working temperature (200 °C) and high annealing temperature (400 °C).
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