(Plenary) Rational Design of Oxide Chemiresistors for Next-Generation Gas Sensors and Artificial Olfaction
Authors: Lee Jong-Heun 
Published: July 2021

Oxide semiconductor chemiresistors have been widely used to detect harmful gases because of their advantages such as high sensitivity, facile integration, and cost effectiveness, and their applications are being expanded to pollutant monitoring, medical diagnosis from exhaled breath, food quality assessment, and smart farming. The collection of big gas sensing data becomes easier than before thanks to the progresses in wireless communication, Internet of Things, and sensor integration. Furthermore, machine learning algorithm and enhanced computing capability are supporting the artificial olfaction. Despite the growth of market demand and relevant technology, oxide semiconductor gas sensors and electronic noses using their array need further improvement since oxide-based chemiresistors often show low gas selectivity and the sensors in the array are frequently insufficient to cover all the complex chemicals. To date, various nanostructures with high surface area to volume ratio have been explored to enhance the gas response and sensing materials have been loaded with noble metal or oxide catalysts for tailoring gas selectivity. Nevertheless, for demand-based design of high performance gas sensors and artificial olfaction, many issues still remain unsolved, which include the detection of ultralow concentration of analyte gas, highly selective detection of a specific gas, moisture-independent gas sensing, and the establishment of distinctive gas sensing library toward numerous analyte gases as well as complex odors [1]. How can we overcome above challenges? The diversity of gas sensing materials provides a rational solution for the complexity of chemicals, which can be accomplished by introducing new sensing materials, designing new nano-architectures, making new methods to tune the reforming/oxidation of analyte/interference gases, establishing new strategies to maximize/control catalytic activity, and using different ways to control electronic/chemical sensitization. In this presentation, various new, promising and general strategies to design sensitive, selective, and reliable chemiresistors for next-generation gas sensors and artificial olfaction will be suggested, which are as follows:

Hollow and hierarchical nanostructures with high gas accessibility for rapid gas detection [2]

P-type oxide semiconductors with high catalytic activity for detecting new gas species [3]

Multi-valence additives for humidity-independent oxide semiconductor gas sensors [4,5]

Catalyst-loaded or catalytic micro-reactors for highly selective detection of aromatic compounds [6]

Bilayer sensors consisting of sensing layer and nanoscale catalytic overlayer for separating catalytic and sensing reactions and modulating gas sensing behaviors [7,8]

Hetero-nanostructures composed of two different materials with dissimilar catalytic activity [9]

Monolayer oxide nanofiber sensor with tailored exposure of catalytic electrode for controlling gas selectivity [10]

References

[1] S.-Y. Jeong, J.-S. Kim, J.-H. Lee, Rational Design of Semiconductor‐Based Chemiresistors and their Libraries for Next‐Generation Artificial Olfaction, Adv. Mater. (online published) doi.org/10.1002/adma.202002075
[2] J.-H. Lee, Gas sensors using hierarchical and hollow oxide nanostructures: Overview, Sens. Actuators B 140 (2009) 319-336. doi:10.1016/j.snb.2009.04.026.
[3] H.-J. Kim, J.-H. Lee, Highly sensitive and selective gas sensors using p-type oxide semiconductors: Overview, Sens. Actuators B 192 (2014) 607-627. doi:10.1016/j.snb.2013.11.005.
[4] H.-R. Kim, A. Haensch, I.-D. Kim, U. Weimar, J.-H. Lee, Role of NiO doping in reducing the humidity impact on the performance of SnO2-based gas sensors: synthesis strategies, phenomenological and spectroscopic studies, Adv. Funct. Mater. 21 (2011) 4229-4240. doi:10.1002/adfm.201101154.
[5] J.‐W. Yoon, J.‐S. Kim, T.‐H. Kim, Y. J. Hong, Y. C. Kang, J.‐H. Lee, A new strategy for humidity independent oxide chemiresistors: Dynamic self‐refreshing of In2O3 sensing surface assisted by layer‐by‐layer coated CeO2 nanoclusters, Small 12 (2016) 4456-4463. doi:10.1002/smll.201601507.
[6] J.-W. Yoon, Y.J. Hong, G.D. Park, S.-J. Hwang, F. Abdel-Hady, A.A.Wazzan, Y.C. Kang, J.-H.Lee, Kilogram-scale synthesis of Pd-loaded quintuple-shelled Co3O4 microreactors and their application to ultrasensitive and ultraselective detection of methylbenzenes, ACS Appl. Mater. Interfaces 7 (2015) 7717-7723. doi: 10.1021/acsami.5b00706.
[7] S.-Y.Jeong, Y.K. Moon, T.-H. Kim, .S-W. Park, K. B. Kim, Y.C. Kang, J.-H. Lee, A New Strategy for Detecting Plant Hormone Ethylene Using Oxide Semiconductor Chemiresistors: Exceptional Gas Selectivity and Response Tailored by Nanoscale Cr2O3 Catalytic Overlayer ethylene sensor Adv. Sci. 7 (2020) 1903093. 10.1002/advs.201903093
[8] S.‐Y. Jeong, Y.K. Moon, J.K. Kim, S.‐W. Park, Y.K. Jo, Y.C. Kang, J.‐H. Lee, A General Solution to Mitigate Water Poisoning of Oxide Chemiresistors: Bilayer Sensors with Tb4O7 Overlayer, Adv. Funct. Mater. (online published) 10.1002/adfm.202007895
[9] T.-H. Kim, C.-H. Kwak, J.-H. Lee, NiO/NiWO4 composite yolk−shell spheres with nanoscale NiO outer layer for ultrasensitive and selective detection of sub ppm-level p-xylene, ACS Appl. Mater. Interfaces 9 (2017) 32034-32043. doi:10.1021/acsami.7b10294.
[10] K. Lim, Y.-M. Jo, J.-W. Yoon, J.-H. Lee, Metal oxide patterns of one-dimensional nanofibers: on-demand, direct-write fabrication, and application as a novel platform for gas detection, J. Mater. Chem. A 7 (2019) 24919-24928. doi:10.1039/C9TA09708B.