Electrically Transduced Gas Sensors Based on Semiconducting Metal Oxide Nanowires

Abstract

Semiconducting metal oxide-based nanowires (SMO-NWs) for gas sensors have been extensively studied for their extraordinary surface-to-volume ratio, high chemical and thermal stabilities, high sensitivity, and unique electronic, photonic and mechanical properties. In addition to improving the sensor response, vast developments have recently focused on the fundamental sensing mechanism, low power consumption, as well as novel applications. Herein, this review provides a state-of-art overview of electrically transduced gas sensors based on SMO-NWs. We first discuss the advanced synthesis and assembly techniques for high-quality SMO-NWs, the detailed sensor architectures, as well as the important gas-sensing performance. Relationships between the NWs structure and gas sensing performance are established by understanding general sensitization models related to size and shape, crystal defect, doped and loaded additive, and contact parameters. Moreover, major strategies for low-power gas sensors are proposed, including integrating NWs into microhotplates, self-heating operation, and designing room-temperature gas sensors. Emerging application areas of SMO-NWs-based gas sensors in disease diagnosis, environmental engineering, safety and security, flexible and wearable technology have also been studied. In the end, some insights into new challenges and future prospects for commercialization are highlighted.

Morphology of Ga2O3 Nanowires and Their Sensitivity to Volatile Organic Compounds

“…where -resistivity of the grain boundaries, -resistivity of the grains, -oxygen partial pressure, -height of the energy gap between the grains. Both of the factors in the Equation (19) depend on the oxygen partial pressure in the ambient and the temperature [2,49,50]. Whereas changes of the conductance result from physicochemical processes occurring at the surface of a gas-sensitive material and in its bulk (i.e., at the grains boundaries, at the grain contacts, in the near-electrode areas).…”

Improving Gas-Sensing Performance Based on MOS Nanomaterials: A Review

“…However, the main limitation of nanoflower gas sensors is stability over their long-term operation of bending and stretching [ 47 ]. Thus, we should improve the synthetic technology of nanoflowers and add some other materials to enhance structural stability.…”

Electrospun Metal Oxide Nanofibers and Their Conductometric Gas Sensor Application. Part 2: Gas Sensors and Their Advantages and Limitations

“…Unlike classical 1D nanomaterials, which are monocrystalline in nature, metal oxide nanofibers are amorphous or polycrystalline. Earlier in [15][16][17][18][19][20][21][22][23], it was shown that one of the most promising fields of application of metal oxide 1D nanomaterials is the development of conductometric gas sensors based on them. As it is followed from discussions presented in Part 1 of our article [24], metal oxide nanofibers are also a promising material for these applications, since a nanofiber mat, forming a gas-sensitive layer, is characterized by high porosity and a large surfaceto-volume ratio [12,25,26].…”

“…However, it is not clear how justified these expectations are from the use of nanofibers in conductometric gas sensors. For example, in [23], it was shown that 1D and 2D nanomaterials, despite the numerous advantages attributed to them [15][16][17][18][19][20][21][22], still do not find application in the development of gas sensors intended for the market.…”