{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,18]],"date-time":"2026-01-18T09:00:50Z","timestamp":1768726850610,"version":"3.49.0"},"reference-count":40,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2022,4,21]],"date-time":"2022-04-21T00:00:00Z","timestamp":1650499200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100014735","name":"JKA Foundation","doi-asserted-by":"publisher","award":["2020M-206"],"award-info":[{"award-number":["2020M-206"]}],"id":[{"id":"10.13039\/501100014735","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Detection, monitoring, and analysis of ethanol are important in various fields such as health care, food industries, and safety control. In this study, we report that a solid electrolyte gas sensor based on a proton-conducting membrane is promising for detecting ethanol in air. We focused on graphene oxide (GO) as a new solid electrolyte because it shows a high proton conductivity at room temperature. GO nanosheets are synthesized by oxidation and exfoliation of expanded graphite via the Tour\u2019s method. GO membranes are fabricated by stacking GO nanosheets by vacuum filtration. To detect ethanol, Au-loaded WO3 is used as the sensing electrode due to the excellent activity of gold nanoparticles for the catalysis of organic molecules. Au-WO3 is coupled with rGO (reduced graphene oxide) to facilitate the electron transport in the electrode. Ce ions are intercalated into the GO membrane to facilitate proton transport. The sensor based on the Ce doped-GO membrane combined with Au-WO3\/rGO as a sensing electrode shows good electric potential difference (\u0394V) responses to ethanol in the air at room temperature. The sensor signal reaches more than 600 mV in response to ethanol at 40 ppm in air, making it possible to detect ethanol at a few ppb (parts per billion) level. The ethanol sensing mechanism was discussed in terms of the mixed-potential theory and catalysis of ethanol on Au-WO3.<\/jats:p>","DOI":"10.3390\/s22093194","type":"journal-article","created":{"date-parts":[[2022,4,24]],"date-time":"2022-04-24T00:45:21Z","timestamp":1650761121000},"page":"3194","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Electrochemical Detection of Ethanol in Air Using Graphene Oxide Nanosheets Combined with Au-WO3"],"prefix":"10.3390","volume":"22","author":[{"given":"Aynul Sakinah Ahmad","family":"Fauzi","sequence":"first","affiliation":[{"name":"Department of Material Science and Applied Chemistry, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan"}]},{"given":"Nur Laila","family":"Hamidah","sequence":"additional","affiliation":[{"name":"Department of Engineering Physics, Institut Teknologi Sepuluh Nopember (ITS), Surabaya 60111, Indonesia"}]},{"given":"Shota","family":"Kitamura","sequence":"additional","affiliation":[{"name":"Department of Material Science and Applied Chemistry, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan"}]},{"given":"Taiga","family":"Kodama","sequence":"additional","affiliation":[{"name":"Department of Material Science and Applied Chemistry, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan"}]},{"given":"Kosuke","family":"Sonda","sequence":"additional","affiliation":[{"name":"Department of Material Science and Applied Chemistry, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan"}]},{"given":"Ghina Kifayah","family":"Putri","sequence":"additional","affiliation":[{"name":"Department of Material Science and Applied Chemistry, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan"}]},{"given":"Takeshi","family":"Shinkai","sequence":"additional","affiliation":[{"name":"Department of Material Science and Applied Chemistry, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0151-3495","authenticated-orcid":false,"given":"Muhammad Sohail","family":"Ahmad","sequence":"additional","affiliation":[{"name":"Institute of Industrial Nanomaterials, Kumamoto University, Kumamoto 860-8555, Japan"}]},{"given":"Yusuke","family":"Inomata","sequence":"additional","affiliation":[{"name":"Division of Materials Science, Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan"},{"name":"International Research Organization for Advanced Science and Technology (IROAST), Kumamoto University, Kumamoto 860-8555, Japan"}]},{"given":"Armando T.","family":"Quitain","sequence":"additional","affiliation":[{"name":"International Research Organization for Advanced Science and Technology (IROAST), Kumamoto University, Kumamoto 860-8555, Japan"},{"name":"Center for International Education, Kumamoto University, Kumamoto 860-8555, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9357-9557","authenticated-orcid":false,"given":"Tetsuya","family":"Kida","sequence":"additional","affiliation":[{"name":"Institute of Industrial Nanomaterials, Kumamoto University, Kumamoto 860-8555, Japan"},{"name":"Division of Materials Science, Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan"},{"name":"International Research Organization for Advanced Science and Technology (IROAST), Kumamoto University, Kumamoto 860-8555, Japan"}]}],"member":"1968","published-online":{"date-parts":[[2022,4,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"35485","DOI":"10.1021\/acsami.6b13006","article-title":"Ultrasensitive Detection of Volatile Organic Compounds by a Pore Tuning Approach Using Anisotropically Shaped SnO2 Nanocrystals","volume":"8","author":"Kida","year":"2016","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2662","DOI":"10.1021\/cm100228d","article-title":"Synthesis of Monodispersed SnO2 Nanocrystals and Their Remarkably High Sensitivity to Volatile Organic Compounds","volume":"22","author":"Kida","year":"2010","journal-title":"Chem. Mater."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"319","DOI":"10.1016\/0167-2738(80)90012-0","article-title":"Carbon monoxide gas sensor made of stabilized zirconia","volume":"1","author":"Okamoto","year":"1980","journal-title":"Solid State Ion."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"H279","DOI":"10.1149\/1.1621880","article-title":"Brosha, E.; Garzon, F. Mixed Potential Hydrocarbon Sensors Based on a YSZ Electrolyte and Oxide Electrodes","volume":"150","author":"Mukundan","year":"2003","journal-title":"J. Electrochem. Soc."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"901","DOI":"10.1007\/s11581-014-1140-1","article-title":"A review of mixed-potential type zirconia-based gas sensors","volume":"20","author":"Miura","year":"2014","journal-title":"Ionics"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"7484","DOI":"10.1016\/j.electacta.2011.06.108","article-title":"Electrochemical detection of volatile organic compounds using a Na3Zr2Si2PO12\/Bi2Cu0.1V0.9O5.35 heterojunction device","volume":"56","author":"Kida","year":"2011","journal-title":"Electrochim. Acta"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"15141","DOI":"10.1021\/jp1047419","article-title":"Control of electrode reactions in a mixed-potential-type gas sensor based on a BiCuVOx solid electrolyte","volume":"114","author":"Kida","year":"2010","journal-title":"J. Phys. Chem. C"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"118","DOI":"10.1016\/j.snb.2018.04.160","article-title":"CeO2-Based Mixed Potential Type Acetone Sensor Using La1-xSrxCoO3 Sensing Electrode","volume":"269","author":"Yang","year":"2018","journal-title":"Sens. Actuators B Chem."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"575","DOI":"10.1016\/j.talanta.2011.04.024","article-title":"Stabilization of sensing performance for mixed-potential-type zirconia-based hydrocarbon sensor","volume":"85","author":"Fujio","year":"2011","journal-title":"Talanta"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"8097","DOI":"10.1021\/ja401060q","article-title":"Graphene oxide nanosheet with high proton conductivity","volume":"135","author":"Karim","year":"2013","journal-title":"J. Am. Chem. Soc."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"6997","DOI":"10.1002\/anie.201309931","article-title":"Proton conductivities of graphene oxide nanosheets: Single, multilayer, and modified nanosheets","volume":"53","author":"Hatakeyama","year":"2014","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2994","DOI":"10.1021\/acsomega.7b00239","article-title":"Solid Electrolyte Gas Sensor Based on a Proton-Conducting Graphene Oxide Membrane","volume":"2","author":"Miyamoto","year":"2017","journal-title":"ACS Omega"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"128678","DOI":"10.1016\/j.snb.2020.128678","article-title":"Carbon-based potentiometric hydrogen sensor using a proton conducting graphene oxide membrane coupled with a WO3 sensing electrode","volume":"323","author":"Fauzi","year":"2020","journal-title":"Sens. Actuators B Chem."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"630","DOI":"10.1007\/s42452-019-0641-y","article-title":"Improving the Proton Conductivity of Graphene Oxide Membranes by Intercalating Cations","volume":"1","author":"Hamidah","year":"2019","journal-title":"SN Appl. Sci."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"4292","DOI":"10.1021\/acsanm.0c00439","article-title":"Graphene Oxide Membranes with Cerium-Enhanced Proton Conductivity for Water Vapor Electrolysis","volume":"3","author":"Hamidah","year":"2020","journal-title":"ACS Appl. Nano Mater."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1799","DOI":"10.1039\/C9NA00048H","article-title":"Porous Reduced Graphene Oxide (RGO)\/WO3 Nanocomposites for the Enhanced Detection of NH3 at Room Temperature","volume":"1","author":"Jeevitha","year":"2019","journal-title":"Nanoscale Adv."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Jiang, Z., Chen, W., Jin, L., Cui, F., Song, Z., and Zhu, C. (2018). High Performance Acetylene Sensor with Heterostructure Based on WO3 Nanolamellae\/Reduced Graphene Oxide (RGO) Nanosheets Operating at Low Temperature. Nanomaterials, 8.","DOI":"10.3390\/nano8110909"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"171691","DOI":"10.1098\/rsos.171691","article-title":"Effects of Sintering Temperature on Sensing Properties of WO3 and Ag-WO3 Electrode for NO2 Sensor","volume":"5","author":"Lu","year":"2018","journal-title":"R. Soc. Open Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"11040","DOI":"10.1038\/srep11040","article-title":"Porous Au-Embedded WO3 Nanowire Structure for Efficient Detection of CH4 and H2S","volume":"5","author":"Kim","year":"2015","journal-title":"Sci. Rep."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"464","DOI":"10.1021\/acs.chemrev.9b00551","article-title":"Importance of Size and Contact Structure of Gold Nanoparticles for the Genesis of Unique Catalytic Processes","volume":"120","author":"Ishida","year":"2020","journal-title":"Chem. Rev."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1016\/j.matlet.2013.07.072","article-title":"Mass Production of Graphene Oxide from Expanded Graphite","volume":"109","author":"Sun","year":"2013","journal-title":"Mater. Lett."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"7634","DOI":"10.1021\/jp0144810","article-title":"Alternative Methods for the Preparation of Gold Nanoparticles Supported on TiO2","volume":"106","author":"Zanella","year":"2002","journal-title":"J. Phys. Chem. B"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"572","DOI":"10.1021\/nn700349a","article-title":"Graphene Oxide Papers Modified by Divalent Ions\u2014Enhancing Mechanical Properties via Chemical Cross-Linking","volume":"2","author":"Park","year":"2008","journal-title":"ACS Nano"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"473","DOI":"10.1039\/a907510k","article-title":"Preparation of Monodispersed Cerium(IV) Oxide Particles by Thermal Hydrolysis: Influence of the Presence of Urea and Gd Doping on Their Morphology and Growth","volume":"10","author":"Hirano","year":"2000","journal-title":"J. Mater. Chem."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"6339","DOI":"10.1039\/c3ra40336j","article-title":"Strong Electron-Conjugation Interaction Facilitates Electron Transfer of Hemoglobin by Ce(OH)3 Nanorods","volume":"3","author":"Wang","year":"2013","journal-title":"RSC Adv."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"23900","DOI":"10.1038\/srep23900","article-title":"Transition-Metal Doped Ceria Microspheres with Nanoporous Structures for CO Oxidation","volume":"6","author":"Zhou","year":"2016","journal-title":"Sci. Rep."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"3790","DOI":"10.1039\/C6RA26309G","article-title":"Efficient Conversion of Fructose into 5-Hydroxymethylfurfural over WO3\/Reduced Graphene Oxide Catalysts","volume":"7","author":"Han","year":"2017","journal-title":"RSC Adv."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"14192","DOI":"10.1039\/C6RA28379A","article-title":"Controllable Synthesis and Enhanced Gas Sensing Properties of a Single-Crystalline WO3\u2013RGO Porous Nanocomposite","volume":"7","author":"Hao","year":"2017","journal-title":"RSC Adv."},{"key":"ref_29","first-page":"8379","article-title":"In-Situ Synthesis of Tetraphenylporphyrin\/Tungsten (VI) Oxide\/Reduced Graphene Oxide (TPP\/WO3 \/RGO) Nanocomposite for Visible Light Photocatalytic Degradation of Acid Blue 25","volume":"4","author":"Malefane","year":"2019","journal-title":"Chem. Select"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1016\/j.mcat.2017.11.014","article-title":"Simultaneous Photocatalytic Degradation of P-Cresol and Cr (VI) by Metal Oxides Supported Reduced Graphene Oxide","volume":"451","author":"Kumar","year":"2018","journal-title":"Mol. Catal."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"173109","DOI":"10.1063\/1.2731662","article-title":"Raman Properties of Gold Nanoparticle-Decorated Individual Carbon Nanotubes","volume":"90","author":"Assmus","year":"2007","journal-title":"Appl. Phys. Lett."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1977","DOI":"10.3762\/bjnano.9.188","article-title":"Self-Assembled Quasi-Hexagonal Arrays of Gold Nanoparticles with Small Gaps for Surface-Enhanced Raman Spectroscopy","volume":"9","author":"Dickreuter","year":"2018","journal-title":"Beilstein J. Nanotechnol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1002\/sia.2180","article-title":"XPS Study of Supported Gold Catalysts: The Role of Au0 and Au + \u03b4 Species as Active Sites","volume":"38","author":"Casaletto","year":"2006","journal-title":"Surf. Interface Anal."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"230","DOI":"10.1039\/C6TA08284J","article-title":"A Novel Method to Decorate Au Clusters onto Graphene via a Mild Co-Reduction Process for Ultrahigh Catalytic Activity","volume":"5","author":"Song","year":"2016","journal-title":"J. Mater. Chem. A"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"2096","DOI":"10.1039\/b707314n","article-title":"Supported Gold Nanoparticles as Catalysts for Organic Reactions","volume":"37","author":"Corma","year":"2008","journal-title":"Chem. Soc. Rev."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"9102","DOI":"10.1039\/C5CE01829C","article-title":"Exposed Facet and Crystal Phase Tuning of Hierarchical Tungsten Oxide Nanostructures and Their Enhanced Visible-Light-Driven Photocatalytic Performance","volume":"17","author":"Li","year":"2015","journal-title":"CrystEngComm"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1149\/1.1838220","article-title":"Proton Conductivity in Nafion 117 and in a Novel Bis[(Perfluoroalkyl)Sulfonyl]Imide Ionomer Membrane","volume":"145","author":"Sumner","year":"1998","journal-title":"J. Electrochem. Soc."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1007\/BF02410307","article-title":"Nafion Based Amperometric Hydrogen Sensor","volume":"10","author":"Velayutham","year":"2004","journal-title":"Ionics"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"16768","DOI":"10.1039\/D1RA01841H","article-title":"A comprehensive and critical review of the recent progress in electrocatalysts for the ethanol oxidation reaction","volume":"11","author":"Yaqoob","year":"2021","journal-title":"RSC Adv."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"27197","DOI":"10.1039\/C6RA01339B","article-title":"Highly Sensitive Mixed-Potential Type Ethanol Sensors Based on Stabilized Zirconia and ZnNb2O6 Sensing Electrode","volume":"6","author":"Liu","year":"2016","journal-title":"RSC Adv."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/9\/3194\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:58:18Z","timestamp":1760137098000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/9\/3194"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,4,21]]},"references-count":40,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2022,5]]}},"alternative-id":["s22093194"],"URL":"https:\/\/doi.org\/10.3390\/s22093194","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,4,21]]}}}