Abstract
Nanocomposite structures, where the Fe, Fe2O3, or Ni2O3 nanoparticles with thin carbon layers are distributed among a single-wall carbon nanotube (SWCNT) network, are architectured using the co-arc discharge method. A synergistic effect between the nanoparticles and SWCNT is achieved with the composite structures, leading to the enhanced sensing response in ammonia detection. Thorough studies about the correlation between the electric properties and sensing performance confirm the independent operation of the receptor and transducer in the sensor structure by nanoparticles and SWCNT, respectively. Nanoparticles with a large specific surface area provide adsorption sites for the NH3 gas molecules, whereas hole carriers are supplied by the SWCNT to complete the chemisorption process. A new chemo-resistive sensor concept and its operating mechanism is proposed in our work. Furthermore, the separated receptor and transducer sensor scheme allows us more freedom in the design of sensor materials and structures, thereby enabling the design of high-performance gas sensors.
Highlights
Metal oxides have been extensively studied for chemoresistive gas sensors because of their high reactivity with various gas molecules as well as their adoptability to modern microfabrication technologies [1]
An ammonia sensing response was thoroughly studied in the Fe:single-wall carbon nanotube (SWCNT), Fe2 O3 :SWCNT, and
Ni2 O3 :SWCNT nanocomposite structures, in which carbon-encapsulated metals or metal oxide nanoparticles are finely distributed among the SWCNT bundles
Summary
Metal oxides have been extensively studied for chemoresistive gas sensors because of their high reactivity with various gas molecules as well as their adoptability to modern microfabrication technologies [1]. It is well known that the molecular adsorption of gas phases followed by the chemical reaction with the oxide occurs by the charge exchange between the gas molecule and oxide, and the consequent change of conductance change in the oxide is translated to the sensing signal through the metal electrodes underneath [2,3,4] In such oxide gas sensors, the surface plays the role of the sensory receptor by the supply of gas molecular ionosorption sites while the bulk structure donates charges for the ionosorption reaction on the surface. Based on the comparative study with single-body gas sensors, hematite or SWCNTs sensors, we explored the underlying sensing mechanism of the composite structure. We showed that such a sensor scheme can be a general route to overcome the nanosize limit regardless of the junction types by comparison with the p-p junction composite of Ni2 O3 :SWCNT
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