Oxide nanostructures for artificial olfaction

Abstract

Artificial olfaction, inspired by biological sensory systems, offers new opportunities in environmental, industrial, and healthcare applications. Semiconducting metal oxide based chemoresistive gas sensors provide a scalable and core interface for chemical detection and therefore constitute the most extensively explored front end for artificial olfactory systems. Nevertheless, conventional chemoresistive sensing that relies on surface charge transfer remains constrained by incomplete response and recovery, humidity interference, cross selectivity, and strong temperature dependence. This review surveys material- and device-level strategies developed to address these bottlenecks, with an emphasis on nanostructuring approaches that improve gas accessibility and reaction kinetics. Moving beyond device-level performance, the review further situates oxide-based gas sensing within a hierarchical neuromorphic olfactory framework. In biological systems, chemical information is represented by distributed activation patterns and temporal dynamics that extend beyond individual receptor responses. Within this broader context, emerging oxide-based transduction concepts that extend conventional chemoresistive operation are also discussed. Recent artificial olfactory system studies have begun to explore alternative oxide-based transduction mechanisms that extend beyond conventional chemoresistive operation. Among these emerging approaches, chemo-memristive responses based on vacancy-mediated ion redox processes are briefly discussed as one possible pathway toward more tightly coupled sensing and signal encoding at the device level. Such developments reflect ongoing efforts to more closely couple sensing and signal processing at the device level. By integrating insights from nanostructured oxide sensors and neuromorphic encoding principles, this review outlines conceptual pathways toward artificial olfactory systems that extend beyond standalone gas detection toward more integrated sensory information processing architectures.

Keywords

Gas sensor / oxide / chemoresistive / chemo-memristive / nanostructure / neuromorphic / olfactory system

References

[1] Barnum G.,Hong E. J.. Olfactory coding Curr. Biol. 2022 32 R1296 301 PMC13084759

[2] Zarzo M.. The sense of smell: molecular basis of odorant recognition Biol. Rev. 2007 82 455 79

[3] Park C. O.,Fergus J. W.,Miura N.,Park J.,Choi A.. Solid-state electrochemical gas sensors Ionics 2009 15 261 84

[4] Paliwal A.,Sharma A.,Tomar M.,Gupta V.. Carbon monoxide (CO) optical gas sensor based on ZnO thin films Sensor. Actuat. B-Chem. 2017 250 679 85

[5] Li X.,Sun W.,Fu W..et al. Advances in sensing mechanisms and micro/nanostructured sensing layers for surface acoustic wave-based gas sensors J. Mater. Chem. A. 2023 11 9216 38

[6] Lee E.,Hwang I.,Cha J..et al. Micromachined catalytic combustible hydrogen gas sensor Sensor. Actuat. B-Chem. 2011 153 392 7

[7] Song Y. G.,Shim Y. S.,Suh J. M..et al. Ionic-activated chemiresistive gas sensors for room-temperature operation Small 2019 15 1902065

[8] Filipovic L.,Selberherr S.. Application of two-dimensional materials towards CMOS-integrated gas sensors Nanomaterials 2022 12 3651 PMC9611560

[9] Jo Y. K.,Jeong S.,Moon Y. K.,Jo Y.,Yoon J.,Lee J.. Exclusive and ultrasensitive detection of formaldehyde at room temperature using a flexible and monolithic chemiresistive sensor Nat. Commun. 2021 12 4955 PMC8368006

[10] Mei H.,Peng J.,Wang T..et al. Overcoming the limits of cross-sensitivity: pattern recognition methods for chemiresistive gas sensor array Nano-Micro Lett. 2024 16 269 PMC11324646

[11] Kaur N.,Singh M.,Comini E.. One-dimensional nanostructured oxide chemoresistive sensors Langmuir 2020 36 6326 44 PMC8154880

[12] Bulemo P. M.,Cheong J. Y.. Review on porosity control in nanostructured semiconducting metal oxides and its influence on chemiresistive gas sensing ACS Appl. Nano Mater. 2023 6 1027 49

[13] Gao D. H.,Yu Q. C.,Kebeded M. A..et al. Advances in modification of metal and noble metal nanomaterials for metal oxide gas sensors: a review Rare Metals 2025 44 1443 96

[14] Zhu L.,Ou L.,Mao L.,Wu X.,Liu Y.,Lu H.. Advances in noble metal-decorated metal oxide nanomaterials for chemiresistive gas sensors: overview Nano-Micro Lett. 2023 15 89 PMC10082150

[15] Das S.,Mojumder S.,Saha D.,Pal M.. Influence of major parameters on the sensing mechanism of semiconductor metal oxide based chemiresistive gas sensors: A review focused on personalized healthcare Sensor. Actuat. B-Chem. 2022 352 131066

[16] Goel N.,Kunal K.,Kushwaha A.,Kumar M.. Metal oxide semiconductors for gas sensing Eng. Rep. 2022 5 e12604

[17] Yang X.,Deng Y.,Yang H..et al. Functionalization of mesoporous semiconductor metal oxides for gas sensing: recent advances and emerging challenges Adv. Sci. 2022 10 2204810 PMC9811452

[18] Chun S. Y.,Song Y. G.,Kim J. E..et al. An artificial olfactory system based on a chemi-memristive device Adv. Mater. 2023 35 2302219

[19] Kim J. S.,Nam Y.,Kim D. Y..et al. Forming-free chemi-memristive gas sensing for artificial olfactory system Sensor. Actuat. B-Chem. 2025 444 138315

[20] Chen H.,Li H.,Ma T.,Han S.,Zhao Q.. Biological function simulation in neuromorphic devices: from synapse and neuron to behavior Sci. Technol. Adv. Mater. 2023 24 2183712 PMC10013381

[21] Chouhdry H. H.,Lee D. H.,Bag A.,Lee N.. A flexible artificial chemosensory neuronal synapse based on chemoreceptive ionogel-gated electrochemical transistor Nat. Commun. 2023 14 821 PMC9929093

[22] Francia S.,Lodovichi C.. The role of the odorant receptors in the formation of the sensory map BMC Biol. 2021 19 174 PMC8394594

[23] Han J. K.,Kang M.,Jeong J..et al. Artificial olfactory neuron for an in-sensor neuromorphic nose Adv. Sci. 2022 9 2106017

[24] Rahimzadeh H.,Sadeghi M.,Ghasemi-varnamkhasti M.,Mireei S. A.,Tohidi M.. On the feasibility of metal oxide gas sensor based electronic nose software modification to characterize rice ageing during storage J. Food Eng. 2019 245 1 10

[25] Cho W.,Yoon S.,Chung T. D.. Streamlining the interface between electronics and neural systems for bidirectional electrochemical communication Chem. Sci. 2023 14 4463 79 PMC10155913

[26] Miura K.,Mainen Z. F.,Uchida N.. Odor representations in olfactory cortex: distributed rate coding and decorrelated population activity Neuron 2012 74 1087 98 PMC3383608

[27] Tang Y.,Zhou B.,Liu J..et al. Specific odor coding using a single thin-film transistor Nano Lett. 2025 25 7587 94

[28] Kang M.,Han J. -K.,Lee K..et al. Neuromorphic olfaction with ultralow-power gas sensors and ovonic threshold switch Sci. Adv. 2025 11 eadv9222 PMC12459429

[29] Dominguez K.,Kumbhar D. D.,Syed A. M.,Martin R. C.,El-Atab N.. The evolution of gas sensors into neuromorphic systems Adv. Electron. Mater. 2025 12 e00639

[30] Stasenko S. V.,Mikhaylov A. N.,Kazantsev V. B.. Model of neuromorphic odorant-recognition network Biomimetics 2023 8 277 PMC10377415

[31] Dey A.. Semiconductor metal oxide gas sensors: a review Mat. Sci. Eng. B-Adv 2018 229 206 17

[32] Liu X.,Cheng S.,Liu H.,Hu S.,Zhang D.,Ning H.. A survey on gas sensing technology Sensors 2012 12 9635 65 PMC3444121

[33] Gebicki J.,Szulczynski B.,Kaminski M.. Determination of authenticity of brand perfume using electronic nose prototypes Meas. Sci. Technol. 2015 26 125103

[34] Lackner E.,Krainer J.,Wimmer-Teubenbacher R..et al. Carbon monoxide detection with CMOS integrated thin film SnO₂ gas sensor Mater. Today: Proc. 2017 4 7128 31

[35] Suh J.,Cho I.,Kang K..et al. Fully integrated and portable semiconductor-type multi-gas sensing module for IoT applications Sensor. Actuat. B-Chem. 2018 265 660 7

[36] Rüffer D.,Hoehne F.,Bühler J.. New digital metal-oxide (MO_x) sensor platform Sensors 2018 18 1052

[37] Park J.,Park K.,Kim T.,Shin S.,Park C.,Yoo H.. Three-electrode metal-oxide gas sensor system with CMOS interface IC IEEE Sensors J. 2016 1

[38] Korotcenkov G.,Cho B.. Spray pyrolysis deposition of undoped SnO₂ and In₂O₃ films and their structural properties Prog. Cryst. Growth Charact. Mater. 2017 63 1 47

[39] Hyodo T.,Fujii E.,Ishida K.,Ueda T.,Shimizu Y.. Microstructural control of porous In2O3 powders prepared by ultrasonic-spray pyrolysis employing self-synthesized polymethylmethacrylate microspheres as a template and their NO₂-sensing properties Sensor. Actuat. B-Chem. 2017 244 992 1003

[40] Park S.,Kim C.,Lee W.,Sung S.,Yoon M.. Sol-gel metal oxide dielectrics for all-solution-processed electronics Mat. Sci. Eng. R. 2017 114 1 22

[41] Znaidi L.. Sol-gel-deposited ZnO thin films: a review Mat. Sci. Eng. B-Adv. 2010 174 18 30

[42] Banger K. K.,Yamashita Y.,Mori K..et al. Low-temperature, high-performance solution-processed metal oxide thin-film transistors formed by a ‘sol-gel on chip’ process Nat. Mater. 2010 10 45 50

[43] Montero J.,Ji Y.,Li S.,Niklasson G. A.,Granqvist C. G.. Sputter deposition of thermochromic VO₂ films on In₂O₃:Sn, SnO₂, and glass: structure and composition versus oxygen partial pressure J. Vac. Sci. Technol. B:Nanotechnol. Microelectron. 2015 33 031805

[44] Lahlalia A.,Filipovic L.,Selberherr S.. Modeling and simulation of novel semiconducting metal oxide gas sensors for wearable devices IEEE Sensors J. 2018 18 1960 70

[45] Imash A.,Smagulova G.,Kaidar B..et al. Chemoresistive gas sensors based on electrospun 1D nanostructures: synergizing morphology and performance optimization Sensors 2024 24 6797 PMC11548165

[46] Sopiha K. V.,Malyi O. I.,Persson C.,Wu P.. Chemistry of oxygen ionosorption on SnO₂ surfaces ACS Appl. Mater. Interfaces 2021 13 33664 76

[47] Motsoeneng R. G.,Kortidis I.,Ray S. S.,Motaung D. E.. Designing SnO₂ nanostructure-based sensors with tailored selectivity toward propanol and ethanol vapors ACS Omega 2019 4 13696 709

[48] Ahmad N.,Kanjariya P.,Priya G. P..et al. Recent advances on the gas-sensing properties and mechanism of perovskite oxide materials - a review ACS Omega 2025 10 13780 96

[49] Liu Y.,Xiao S.,Du K.. Chemiresistive gas sensors based on hollow heterojunction: a review Adv. Mater. Inter. 2021 8 2002122

[50] Mori M.,Noguchi A.,Itagaki Y.. VOC detections by p-type semiconducting sensors using nano-sized SmFeO₃ particles Sensors 2022 22 5616

[51] Kim H.,Lee J.. Highly sensitive and selective gas sensors using p-type oxide semiconductors: overview Sensor. Actuat. B-Chem. 2014 192 607 27

[52] Wu J.,Gao D.,Sun T..et al. Highly selective gas sensing properties of partially inversed spinel zinc ferrite towards H₂S Sensor. Actuat. B-Chem. 2016 235 258 62

[53] Chander S.,Tripathi S.,Kaur I.. ABO₃-based perovskite oxides for gas sensors: a review of recent advancement in materials, mechanisms, and strategies for real-time applications Chem. Eng. J. 2025 524 169490

[54] Miller D. R.,Akbar S. A.,Morris P. A.. Nanoscale metal oxide-based heterojunctions for gas sensing: a review Sensor. Actuat. B-Chem. 2014 204 250 72

[55] Shao F.,Hoffmann M.,Prades J..et al. Heterostructured p-CuO (nanoparticle)/n-SnO₂ (nanowire) devices for selective H₂S detection Sensor. Actuat. B-Chem. 2013 181 130 5

[56] Kim J.,Jeong H.,Na C. W..et al. Highly selective and sensitive xylene sensors using Cr₂O₃-ZnCr₂O₄ hetero-nanostructures prepared by galvanic replacement Sensor. Actuat. B-Chem. 2016 235 498 506

[57] Sharma A.,Eadi S. B.,Noothalapati H.,Otyepka M.,Lee H.,Jayaramulu K.. Porous materials as effective chemiresistive gas sensors Chem. Soc. Rev. 2024 53 2530 77

[58] Majhi S. M.,Mirzaei A.,Kim H. W.,Kim S. S.,Kim T. W.. Recent advances in energy-saving chemiresistive gas sensors: a review Nano Energy 2021 79 105369

[59] Bing Y.,Zhang F.,Han J.,Zhou T.,Mei H.,Zhang T.. A method of ultra-low power consumption implementation for MEMS gas sensors Chemosensors 2023 11 236

[60] Wang Y.,Zhou Y.. Recent progress on anti-humidity strategies of chemiresistive gas sensors Materials 2022 15 8728

[61] Turlybekuly A.,Shynybekov Y.,Soltabayev B.,Yergaliuly G.,Mentbayeva A.. The cross-sensitivity of chemiresistive gas sensors: nature, methods, and peculiarities: a systematic review ACS Sens. 2024 9 6358 71

[62] Yu S.,Jia X.,Zhang J.,Yang W.,Song H.. Recent advances in different materials for moisture resistance of metal oxide-based gas sensors: a review Chem. Eng. J. 2025 505 159639

[63] Liu L.,Wang Y.,Liu Y..et al. Heteronanostructural metal oxide-based gas microsensors Microsyst. Nanoeng. 2022 8 85

[64] Lee D.,Yun M. J.,Kim K. H.,Kim S.,Kim H.. Advanced recovery and high-sensitive properties of memristor-based gas sensor devices operated at room temperature ACS Sens. 2021 6 4217 24

[65] Panžić I.,Bafti A.,Radovanović-Perić F..et al. Advancements in nanostructured functional constituent materials for gas sensing applications: a comprehensive review Appl. Sci. 2025 15 2522

[66] Mirzaei A.,Lee J.,Majhi S. M..et al. Resistive gas sensors based on metal-oxide nanowires J. Appl. Phys. 2019 126 241102

[67] Kolmakov A.,Moskovits M.. Chemical sensing and catalysis by one-dimensional metal-oxide nanostructures Annu. Rev. Mater. Res. 2004 34 151 80

[68] Korotcenkov G.. Gas response control through structural and chemical modification of metal oxide films: state of the art and approaches Sensor. Actuat. B-Chem. 2005 107 209 32

[69] Fan Z.,Wang D.,Chang P.,Tseng W.,Lu J. G.. ZnO nanowire field-effect transistor and oxygen sensing property Appl. Phys. Lett. 2004 85 5923 5

[70] Kirkpatrick S.. Percolation and conduction Rev. Mod. Phys. 1973 45 574 88

[71] Hübner M.,Simion C.,Tomescu-Stănoiu A.,Pokhrel S.,Bârsan N.,Weimar U.. Influence of humidity on CO sensing with p-type CuO thick film gas sensors Sensor. Actuat. B-Chem. 2011 153 347 53

[72] Moon C. S.,Kim H.,Auchterlonie G.,Drennan J.,Lee J.. Highly sensitive and fast responding CO sensor using SnO₂ nanosheets Sensor. Actuat. B-Chem. 2008 131 556 64

[73] Kim H.,Choi K.,Lee J.,Akbar S. A.. Highly sensitive and ultra-fast responding gas sensors using self-assembled hierarchical SnO₂ spheres Sensor. Actuat. B-Chem. 2009 136 138 43

[74] Qin L.,Xu J.,Dong X..et al. The template-free synthesis of square-shaped SnO₂ nanowires: the temperature effect and acetone gas sensors Nanotechnology 2008 19 185705

[75] Zhang J.,Wang S.,Wang Y..et al. NO₂ sensing performance of SnO₂ hollow-sphere sensor Sensor. Actuat. B-Chem. 2009 135 610 7

[76] Yoon J.,Choi S. H.,Kim J.,Jang H. W.,Kang Y. C.,Lee J.. Trimodally porous SnO₂ nanospheres with three-dimensional interconnectivity and size tunability: a one-pot synthetic route and potential application as an extremely sensitive ethanol detector NPG Asia Mater. 2016 8 e244

[77] Zan H.,Dai M.,Hsu T.,Lin H.,Meng H.,Yang Y.. Porous organic TFTs for the applications on real-time and sensitive gas sensors IEEE Electron Device Lett. 2011 32 1143 5

[78] Guo T.,Yao M.,Lin Y.,Nan C.. A comprehensive review on synthesis methods for transition-metal oxide nanostructures CrystEngComm 2015 17 3551 85

[79] Xiao X.,Liu L.,Ma J..et al. Ordered mesoporous tin oxide semiconductors with large pores and crystallized walls for high-performance gas sensing ACS Appl. Mater. Interfaces 2018 10 1871 80

[80] Choi Y.,Hwang I.,Park J.,Choi K. J.,Park J.,Lee J.. Novel fabrication of an SnO₂ nanowire gas sensor with high sensitivity Nanotechnology 2008 19 095508

[81] Bhowmik B.,Fecht H.,Bhattacharyya P.. Vertical mode gas sensing performance of TiO₂ nanotube array by tuning of surface area and carrier transport length IEEE Sensors J. 2015 15 5919 26

[82] Zhou J.,Hua Z.,Liu Z.,Wu W.,Zhu Y.,Shi J.. Direct synthetic strategy of mesoporous ZSM-5 zeolites by using conventional block copolymer templates and the improved catalytic properties ACS Catal. 2011 1 287 91

[83] Kim I.,Rothschild A.,Tuller H. L.. Advances and new directions in gas-sensing devices Acta Mater. 2013 61 974 1000

[84] Baek J. W.,Kim I.. Advances in perovskite oxides for chemiresistive sensors Acc. Mater. Res. 2023 4 1108 20

[85] Moseley P. T.. Progress in the development of semiconducting metal oxide gas sensors: a review Meas. Sci. Technol. 2017 28 082001

[86] Shin H.,Jung W.,Kim D..et al. Single-atom Pt stabilized on one-dimensional nanostructure support via carbon nitride/SnO₂ heterojunction trapping ACS Nano 2020 14 11394 405

[87] Koo W.,Cho H.,Kim D..et al. Chemiresistive hydrogen sensors: fundamentals, recent advances, and challenges ACS Nano 2020 14 14284 322

[88] Bezkrovnyi O.,Bruix A.,Blaumeiser D..et al. Metal-support interaction and charge distribution in ceria-supported Au particles exposed to CO Chem. Mater. 2022 34 7916 36

[89] Koshevoy E.,Gribov E.,Lyulyukin M.,Selishchev D.,Kozlov D.. Photoelectrochemical study of M/TiO₂ (M = Pt, Pd, Au) supported catalysts: flat-band potentials and photoelectrocatalytic properties in glycerol oxidation reaction J. Photoch. Photobio. A 2026 471 116678

[90] Shin H.,Ko J.,Park C..et al. Sacrificial template-assisted synthesis of inorganic nanosheets with high-loading single-atom catalysts: a general approach Adv. Funct. Mater. 2021 32 2110485

[91] Van Tran T.,Kim D.,Duc Le T.,Oh G.,Shin G.,Yu Y.. Alloy core composition effect of Pd-Augr-alloy@ZnO core-shell nanoparticles on hydrogen gas sensing performance Chem. Eng. J. 2024 483 149050

[92] Kim D.,Kim J. K.,Oh D..et al. Ex-solution hybrids functionalized on oxide nanofibers for highly active and durable catalytic materials ACS Nano 2023 17 5842 51

[93] Li Y.,Cheng X.,Zhang S..et al. Alcohol selectivity of a room temperature-operated gas sensor based on TiO₂ burr-like nanorods Chem. Eng. J. 2025 508 160923

[94] Sanghikian Marques Dos Santos G.,Theodoro R. D. S.,Gera G. O.,Micheli Perfecto T.,Paschoalini Volanti D.. Ethyl acetate detection using mixed-phase In₂O₃ nanorods ACS Appl. Nano Mater. 2025 8 11458 69

[95] Du Y.,Ren L.,Yuan J.,Zhang R.,Xie M.,Xu H.. In-situ synthesized Sn-doped In₂O₃ nanorods for low-temperature NO₂ sensing with high response Sensor. Actuat. B-Chem. 2025 445 138564

[96] Kandhare N.,Mathe V.,Bhagwat S.. Room temperature NO₂ gas sensor using h-WO₃ nanorod based thin films Mat. Sci. Eng. B-Adv. 2024 305 117422

[97] Li X.,Hu H.,Tan T..et al. Enhancing methane gas sensing through defect engineering in Ag-Ru Co-doped ZnO nanorods ACS Appl. Mater. Interfaces 2024 16 26395 405

[98] Jo M.,Kim S.,Park S..et al. Fast-response and low-power self-heating gas sensor using metal/metal oxide/metal (MMOM) structured nanowires. ACS Sens. 2024, 9, 1896-905

[99] Lai L.,Hsueh H.,Chiu C.,Cheng T.,Chang S.. Thermal oxidation CuO nanowire gas sensor for ozone detection applications Sens. Actuators Rep. 2024 8 100228

[100] Thi Nguyet T.,Van Duy L.,Nam N. C..et al. Transition from p-type to n-type semiconductor in V₂O₅ nanowire-based gas sensors: synthesis and understanding of the sensing mechanism Sensor. Actuat. B-Chem. 2025 424 136841

[101] Malik S. B.,Mejia-Centeno K. V.,Martínez-Alanis P. R..et al. Synergistic effect of CeO₂ nanoparticles and WO₃ nanowires in gas sensing applications Sensor. Actuat. B-Chem. 2024 400 134879

[102] Wang X.,Wang X.,Sui X..et al. ZnO nanowire/NiO foam 3D nanostructures for high-performance ethylene glycol sensing Sensor. Actuat. B-Chem. 2024 400 134918

[103] Khomarloo N.,Gidik H.,Bagherzadeh R..et al. Enhancing nitric oxide gas detection by tuning the structural dimension of electrospun ZnO nanofibers fibers and polymers Fibers Polym. 2024 26 197 209

[104] To D. T. H.,Yang B.,Myung N. V.. Enhancing nitrous oxide chemiresistive sensing performance by reducing ionic Oxygen species adsorption in Gold functionalized Tungsten Trioxide nanofibers Sens. Actuators Rep. 2024 8 100255

[105] Luo Q.,Wan Y.,Wang Z.,Gao S.,Chen Y.,Feng C.. Excellent-performing gas sensor based on Yttrium-doped ZnFe₂O₄ nanofibers for detection of n-Butanol J. Alloys Compd. 2025 1027 180605

[106] Kim Y. W.,Yang B.,To D. T. H..et al. Improved selectivity toward methanol detection via Pd-functionalized tungsten trioxide nanofiber gas sensors Chem. Eng. J. 2025 523 168814

[107] Wu J.,Zheng Z.,Chi H.,Jiang J.,Zhu L.,Ye Z.. Ultrasensitive and exclusive chemiresistors with a ZIF-67-derived oxide cage/nanofiber Co₃O₄/In₂O₃ heterostructure for acetone detection ACS Appl. Mater. Interfaces 2024 16 9126 36

[108] Bhunia A. K.,Mahata B.,Mandal B.,Guha P. K.,Saha S.. Emerging 2D nanoscale metal oxide sensor: semiconducting CeO₂ nano-sheets for enhanced formaldehyde vapor sensing Nanotechnology 2024 35 455501

[109] Li J.,Deng Y.,Liu L..et al. Synthesis of 2D porous indium oxide nanosheets for fabrication of high-performance flexible gas sensors Small 2025 21 e05870

[110] Kim M. Y.,Choa H.,Park C. O..et al. Boundary engineering of porous zinc oxide nanosheets to enhance gas sensing performance Sens. Actuators Rep 2025 9 100322

[111] Nii Okai Amu-Darko J.,Hussain S.,Zhang X..et al. Enhanced H₂S gas sensing utilizing UV-assisted In₂O₃@ZnO nanosheets Ceram. Int. 2024 50 38242 52

[112] Zhang Y.,Shen Y.,Zhang W.,Sun Z.,Gu F.,Wang L.. Enhanced low-working temperature 2-butanone gas-sensing performance of N-doped ZnO mesoporous nanosheets J. Mater. Sci:. Mater. Electron. 2024 35 485

[113] Abedzadeh M.,Ranjbar M.,Kameli P.. Fabrication of Pd-decorated tungsten oxide nanoflakes for hydrogen sensors via facile anodizing oxidation method Int. J. Hydrogen Energy 2024 50 1325 34

[114] Yang M.,Liu L.,Li B..et al. Novel NiO nanoflakes in situ grown on graphene layers for the sensitive detection of low concentration H₂S Appl. Surf. Sci. 2026 720 165191

[115] Awale M.,Lokhande S. D.,Kathwate L. H.,Vasundhara M.,Mote V. D.,Kadam A. B.. Highly sensitive and selective gas sensors for ethanol based on Mn doped ZnO nanoflakes J. Cluster Sci. 2024 35 2273 82

[116] Cheng Y.,Portela R.,Wang P..et al. Ultrasensitive In₂O₃-Based nanoflakes for lung cancer diagnosis and the sensing mechanism investigated by operando spectroscopy ACS Sens. 2024 9 6382 9

[117] Parveen R. A.,Vinoth E.,Archana J.,Ponnusamy S.,Navaneethan M.. Highly sensitive parts per trillion detection of microwave assisted V₂O₅ nano-flake sensor for hazardous NO₂ Chem. Phys. 2026 601 112949

[118] Chen L.,Sun X.,Song Z.,Gao R.,Guo Z.,Huang X.. Theoretical validation of non-noble Cu sites integrated on SnO₂ nanoflowers for enhanced gas sensing of ethanethiol at room temperature Inorg. Chem. 2024 63 11438 49

[119] Fu S.,Wang A.,Yin M.,Li G.. Pd nanoparticles decorated 3D peony-like ZnO nanoflowers enable ultra-high response and selectivity of TEA gas sensing: experimental and DFT validation J. Alloys Compd. 2025 1047 184972

[120] Li Y.,Kuang X.,Yu L..et al. Fe sites engineering unlocks selective chemiresistive sensing of n-propanol for breath-based lung cancer diagnostics Chem. Eng. J. 2025 521 166508

[121] Nimbalkar T. M.,Kadam S. A.,Ma Y.,Selvaraj M.,Assiri M. A.,Patil V. B.. Tailoring Zn mixed WO₃ nanoflowers for highly efficient NO₂ gas detection Ceram. Int. 2024 50 38514 21

[122] Qi L.,Song B.,Wu H..et al. Synthesis of Ag-doped SnO₂ nanoflowers and applications to room temperature high-performance NO₂ gas sensing Sensor. Actuat. B-Chem. 2024 420 136494

[123] Ni P.,Ma S.,Ma N..et al. Porous hollow sphere structure PrFeO₃ as an efficient sensing material for n-butanol detection J. Alloys Compd. 2024 1002 175392

[124] Wang G.,Wang Y.,Guo L..et al. Chemiresistive n-butanol gas sensors based on Au@In₂O₃ hollow-sphere-array thin films Sensor. Actuat. B-Chem. 2025 422 136579

[125] Wang G.,Chen T.,Guo L..et al. Chemiresistive n-butanol gas sensors based on Co₃O₄@ZnO hollow-sphere-array thin films prepared by template-assisted magnetron sputtering Sensor. Actuat. B-Chem. 2024 413 135862

[126] Zhang F.,Qu Y.,Lu X..et al. Double-shelled hollow sphere V₂O₅-based conductometric ethanol gas sensor Sensor. Actuat. B-Chem. 2024 417 136009

[127] Li X.,Li Y.,Xu X..et al. Persistently boosted TEA sensing performance of In₂O₃ hollow spheres by sequentially modified with Bi₂O₃ and Pt nanoparticles Sensor. Actuat. B-Chem. 2025 422 136628

[128] Zhao Z.,Xu X.,Zhang H.. Pr-doped W₁₈O₄₉ sea urchin-like nanospheres for enhanced triethylamine gas sensor Sensor. Actuat. B-Chem. 2026 450 139280

[129] Xue T.,Yu J.,Yu H..et al. Construction of gas-sensing material with ZnO crystal flower clustered on sea urchin-like CuO structure and its gas-sensing properties to NO_x at room temperature Ceram. Int. 2025 51 42806 14

[130] Zhou Y.,Luo Y.,Zheng Z..et al. Urchin-like Na-doped zinc oxide nanoneedles for low-concentration and exclusive VOC detections J. Adv. Ceram. 2024 13 507 17

[131] Cheng Y.,Teng Y.,Zheng M..et al. 3D Urchin-Like WO_3-x based nanostructures with abundant oxygen vacancies for ppb-Level tea aroma sensing Sensor. Actuat. B-Chem. 2024 419 136293

[132] Sun Y.,Han D.,Sun S.,Dong Y.,Li X.,Qian K.. Urchin-like dual-shelled ZnO/SnO₂ hollow spheres for ultrahigh sensitive low-temperature NO₂ sensing Sensor. Actuat. B-Chem. 2026 450 139227

[133] Sung S.,Suh J. M.,Hwang Y. J.,Jang H. W.,Park J. G.,Jun S. C.. Data-centric artificial olfactory system based on the eigengraph Nat. Commun. 2024 15 1211

[134] Madvar H. R.,Kordrostami Z.,Mirzaei A.. Sensitivity enhancement of resistive ethanol gas sensor by optimized sputtered-assisted CuO decoration of ZnO nanorods Sensors 2022 23 365

[135] Zhai Y.,Yang R.,Wu J..et al. Nitrogen plasma-driven oxygen vacancy modulation in tin dioxide nanosheets enables sub-parts-per-billion nitrogen dioxide detection at low operating temperature ACS Sens. 2025 10 4184 93

[136] Bu W.,Zhang Y.,Qin Q..et al. Improved ppb-level NO₂ conductometric sensor induced by trace Au on SnO2 nanosheet Sensor. Actuat. B-Chem. 2023 379 133237

[137] Yi S. Y.,Song Y. G.,Park J. Y..et al. Morphological evolution induced through a heterojunction of W-decorated NiO nanoigloos: synergistic effect on high-performance gas sensors ACS Appl. Mater. Interfaces 2019 11 7529 38

[138] Li Q.,Zhang P.,Ning T..et al. Gas sensor based on flower-like NiO modified with WO₃ nanoparticles for NO₂ detection ACS Appl. Nano Mater. 2024 7 7856 64

[139] Hou J.,Yang Z.,Rong Q.,Zhang C.,Wang C.,Guo Y.. Au-decorated Sn₃O₄ nanoflower-based MEMS gas sensor for detecting ppb-level acetone ACS Appl. Nano Mater. 2024 7 6506 15

[140] Kim H. R.,Haensch A.,Kim I. D.,Barsan N.,Weimar U.,Lee J. H.. The role of NiO doping in reducing the impact of humidity on the performance of SnO₂-based gas sensors: synthesis strategies, and phenomenological and spectroscopic studies Adv. Funct. Mater. 2011 21 4456 63

[141] Suematsu K.,Sasaki M.,Ma N.,Yuasa M.,Shimanoe K.. Antimony-doped tin dioxide gas sensors exhibiting high stability in the sensitivity to humidity changes ACS Sens. 2016 1 913 20

[142] Ma N.,Suematsu K.,Yuasa M.,Kida T.,Shimanoe K.. Effect of water vapor on Pd-loaded SnO₂ nanoparticles gas sensor ACS Appl. Mater. Interfaces 2015 7 5863 9

[143] Choi K.,Kim H.,Kang Y. C.,Lee J.. Ultraselective and ultrasensitive detection of H2S in highly humid atmosphere using CuO-loaded SnO₂ hollow spheres for real-time diagnosis of halitosis Sensor. Actuat. B-Chem. 2014 194 371 6

[144] Kim J.,Na C. W.,Kwak C..et al. Humidity-independent gas sensors using Pr-doped In₂O₃ macroporous spheres: role of cyclic Pr³⁺/Pr⁴⁺ redox reactions in suppression of water-poisoning effect ACS Appl. Mater. Interfaces 2019 11 25322 9

[145] Kwak C.,Kim T.,Jeong S.,Yoon J.,Kim J.,Lee J.. Humidity-independent oxide semiconductor chemiresistors using terbium-doped SnO₂ yolk-shell spheres for real-time breath analysis ACS Appl. Mater. Interfaces 2018 10 18886 94

[146] Yoon J. W.,Kim J. S.,Kim T. H.,Hong Y. J.,Kang Y. C.,Lee J. H.. A new strategy for humidity independent oxide chemiresistors: dynamic self-refreshing of In₂O₃ sensing surface assisted by layer-by-layer coated CeO₂ nanoclusters Small 2016 12 4229 40

[147] Yao M. S.,Tang W. X.,Wang G. E.,Nath B.,Xu G.. MOF Thin film-coated metal oxide nanowire array: significantly improved chemiresistor sensor performance Adv. Mater. 2016 28 5229 34

[148] Nasriddinov A.,Rumyantseva M.,Konstantinova E..et al. Effect of humidity on light-activated NO and NO₂ gas sensing by hybrid materials Nanomaterials 2020 10 915

[149] Jeong S.,Moon Y. K.,Wang J.,Lee J.. Exclusive detection of volatile aromatic hydrocarbons using bilayer oxide chemiresistors with catalytic overlayers Nat. Commun. 2023 14 233

[150] Sun Y.,Liu S.,Meng F..et al. Metal oxide nanostructures and their gas sensing properties: a review Sensors 2012 12 2610 31

[151] Wilson R. I.,Mainen Z. F.. Early events in olfactory processing Annu. Rev. Neurosci. 2006 29 163 201

[152] Wachowiak M.,Shipley M. T.. Coding and synaptic processing of sensory information in the glomerular layer of the olfactory bulb Semin. Cell Dev. Biol. 2006 17 411 23

[153] Imam N.,Cleland T. A.. Rapid online learning and robust recall in a neuromorphic olfactory circuit Nat. Mach. Intell. 2020 2 181 91

[154] Schmuker M.,Pfeil T.,Nawrot M. P.. A neuromorphic network for generic multivariate data classification Proc. Natl. Acad. Sci. U.S.A. 2014 111 2081 6

[155] Jang Y. W.,Kim J.,Shin J..et al. Autonomous artificial olfactory sensor systems with homeostasis recovery via a seamless neuromorphic architecture Adv. Mater. 2024 36 2400614

[156] Raman B.,Stopfer M.,Semancik S.. Mimicking biological design and computing principles in artificial olfaction ACS Chem. Neurosci. 2011 2 487 99

[157] Kwon H.,Kamboj O.,Song A..et al. Scalable optical nose realized with a chemiresistively modulated light-emitter array Adv. Mater. 2024 36 2402287

[158] Xiong Z.,Liang W.,Zhang M.,Mao D.,Xia Q.,Xu G.. Parallelizing analog in-sensor visual processing with arrays of gate-tunable silicon photodetectors Nat. Commun. 2025 16 4728

[159] Lee S.,Kang M.,Han J.,Yun S.,Park I.,Choi Y.. An artificial olfactory sensory neuron for selective gas detection with in-sensor computing Device 2023 1 100063

[160] Chen J. Y.,Huang C. W.,Chiu C. H.,Huang Y. T.,Wu W. W.. Switching kinetic of VCM-based memristor: evolution and positioning of nanofilament Adv. Mater. 2015 27 5028 33

[161] Ali M.,Lee D.,Ahmad I.,Kim H.. Recent progress in memristor-based gas sensors (Gasistor; gas sensor + memristor): device modeling, mechanisms, performance, and prospects Sens. Actuators Rep. 2025 9 100269

[162] Najafi P.,Ghaemi A.. Chemiresistor gas sensors: design, challenges, and strategies: a comprehensive review Chem. Eng. J. 2024 498 154999

[163] Wang Y.,Li R.,Xin S..et al. An artificial optical nose integrated by metal-organic frameworks three-dimensional photonic crystal array for identification of trace hazardous gases through machine learning integration J. Environ. Chem. Eng. 2025 13 117043

[164] Dennler N.,True A.,Van Schaik A.,Schmuker M.. Neuromorphic principles for machine olfaction Neuromorph. Comput. Eng. 2025 5 023001