{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,31]],"date-time":"2026-03-31T10:41:22Z","timestamp":1774953682113,"version":"3.50.1"},"reference-count":61,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2020,12,20]],"date-time":"2020-12-20T00:00:00Z","timestamp":1608422400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002261","name":"Russian Foundation for Basic Research","doi-asserted-by":"publisher","award":["18-03-00091"],"award-info":[{"award-number":["18-03-00091"]}],"id":[{"id":"10.13039\/501100002261","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004285","name":"Saint Petersburg State University","doi-asserted-by":"publisher","award":["Event 3-2018 (id: 46380300)"],"award-info":[{"award-number":["Event 3-2018 (id: 46380300)"]}],"id":[{"id":"10.13039\/501100004285","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Variable air humidity affects the characteristics of semiconductor metal oxides, which complicates the reliable and reproducible determination of CO content in ambient air by resistive gas sensors. In this work, we determined the sensor properties of electrospun ZnO and ZnO\/Pd nanofibers in the detection of CO in dry and humid air, and investigated the sensing mechanism. The microstructure of the samples, palladium content, and oxidation state, type, and concentration of surface groups were characterized using complementary techniques: X-ray fluorescent spectroscopy, XRD, high-resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray (EDX) mapping, XPS, and FTIR spectroscopy. The sensor properties of ZnO and ZnO\/Pd nanofibers were studied at 100\u2013450 \u00b0C in the concentration range of 5\u201315 ppm CO in dry (RH25 = 0%) and humid (RH25 = 60%) air. It was found that under humid conditions, ZnO completely loses its sensitivity to CO, while ZnO\/Pd retains a high sensor response. On the basis of in situ diffuse reflectance IR Fourier transform spectroscopy (DRIFTS) results, it was concluded that high sensor response of ZnO\/Pd nanofibers in dry and humid air was due to the electronic sensitization effect, which was not influenced by humidity change.<\/jats:p>","DOI":"10.3390\/s20247333","type":"journal-article","created":{"date-parts":[[2020,12,21]],"date-time":"2020-12-21T01:01:08Z","timestamp":1608512468000},"page":"7333","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["Electrospun ZnO\/Pd Nanofibers: CO Sensing and Humidity Effect"],"prefix":"10.3390","volume":"20","author":[{"given":"Vadim","family":"Platonov","sequence":"first","affiliation":[{"name":"Chemistry Department, Moscow State University, 119991 Moscow, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3354-0885","authenticated-orcid":false,"given":"Marina","family":"Rumyantseva","sequence":"additional","affiliation":[{"name":"Chemistry Department, Moscow State University, 119991 Moscow, Russia"},{"name":"Institute of Chemistry, Saint Petersburg State University, Petergof, 198504 Saint Petersburg, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8011-4635","authenticated-orcid":false,"given":"Nikolay","family":"Khmelevsky","sequence":"additional","affiliation":[{"name":"Material Properties Research Laboratory (LISM), Moscow State Technological University Stankin, 127055 Moscow, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alexander","family":"Gaskov","sequence":"additional","affiliation":[{"name":"Chemistry Department, Moscow State University, 119991 Moscow, Russia"},{"name":"Institute of Chemistry, Saint Petersburg State University, Petergof, 198504 Saint Petersburg, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,12,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"54","DOI":"10.1016\/j.snb.2016.06.072","article-title":"The oxidizing effect of humidity on WO3 based sensors","volume":"237","author":"Staerz","year":"2016","journal-title":"Sens. Actuators B Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"455","DOI":"10.1016\/j.snb.2014.10.016","article-title":"Conduction mechanism switch for SnO2 based sensors during operation in application relevant conditions; implications for modeling of sensing","volume":"207","author":"Rebholz","year":"2015","journal-title":"Sens. Actuators B Chem."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"787","DOI":"10.1016\/j.snb.2012.03.075","article-title":"Interplay of H2, water vapor and oxygen at the surface of SnO2 based gas sensors\u2014An operando investigation utilizing deuterated gases","volume":"166","author":"Grossmann","year":"2012","journal-title":"Sens. Actuators B Chem."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1016\/j.aca.2018.01.062","article-title":"Estimation of the limit of detection in semiconductor gas sensors through linearized calibration models","volume":"1013","author":"Marco","year":"2018","journal-title":"Anal. Chim. Acta"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1016\/j.aca.2018.03.005","article-title":"Multivariate estimation of the limit of detection by orthogonal partial least squares in temperature-modulated MOX sensors","volume":"1019","author":"Marco","year":"2018","journal-title":"Anal. Chim. Acta"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"502","DOI":"10.1016\/j.snb.2017.07.100","article-title":"Selective detection of individual gases and CO\/H2 mixture at low concentrations in air by single semiconductor metal oxide sensors working in dynamic temperature mode","volume":"254","author":"Krivetskiy","year":"2018","journal-title":"Sens. Actuators B Chem."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Krivetskiy, V.V., Andreev, M.D., Efitorov, A.O., and Gaskov, A.M. (2020). Statistical shape analysis pre-processing of temperature modulated metal oxide gas sensor response for machine learning improved selectivity of gases detection in real atmospheric conditions. Sens. Actuators B Chem., 129187. in press.","DOI":"10.1016\/j.snb.2020.129187"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1016\/j.progsurf.2006.12.002","article-title":"The chemistry and physics of zinc oxide surfaces","volume":"82","author":"Woell","year":"2007","journal-title":"Prog. Surf. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"6642","DOI":"10.1002\/anie.200461696","article-title":"Partial dissociation of water leads to stable superstructures on the surface of zinc oxide","volume":"43","author":"Meyer","year":"2004","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"7092","DOI":"10.1039\/b811029h","article-title":"The identification of hydroxyl groups on ZnO nanoparticles by infrared spectroscopy","volume":"10","author":"Noei","year":"2008","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"10073","DOI":"10.1007\/s10854-019-01111-8","article-title":"Carbon monoxide gas sensing features of zinc oxide nanoneedles: Practical selectivity and long-term stability","volume":"30","author":"Bandari","year":"2019","journal-title":"J. Mater. Sci. Mater. Electron."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"127054","DOI":"10.1016\/j.snb.2019.127054","article-title":"Gas sensitive ZnO structures with reduced humidity-interference","volume":"301","author":"Vallejos","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Fomekong, R.L., and Saruhan, B. (2019). Influence of Humidity on NO2-Sensing and Selectivity of Spray-CVD Grown ZnO Thin Film above 400 \u00b0C. Chemosensors, 7.","DOI":"10.3390\/chemosensors7030042"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"813","DOI":"10.1088\/0953-8984\/15\/20\/201","article-title":"Understanding the fundamental principles of metal oxide based gas sensors; the example of CO sensing with SnO2 sensors in the presence of humidity","volume":"15","author":"Weimar","year":"2003","journal-title":"J. Phys. Condens. Matter"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"76","DOI":"10.1016\/S0040-6090(03)00512-1","article-title":"DRIFT studies of thick film un-doped and Pd-doped SnO2 sensors: Temperature changes effect and CO detection mechanism in the presence of water vapour","volume":"436","author":"Harbeck","year":"2003","journal-title":"Thin Solid Film."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.snb.2006.04.014","article-title":"Spectroscopic insights into CO sensing of undoped and palladium doped tin dioxide sensors derived from hydrothermally treated tin oxide sol","volume":"118","author":"Koziej","year":"2006","journal-title":"Sens. Actuators B Chem."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"8620","DOI":"10.1039\/b906829e","article-title":"Operando X-ray absorption spectroscopy studies on Pd-SnO2 based sensors","volume":"11","author":"Koziej","year":"2009","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"5863","DOI":"10.1021\/am509082w","article-title":"Effect of Water Vapor on Pd-loaded SnO2 Nanoparticles Gas Sensor","volume":"7","author":"Ma","year":"2015","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"28149","DOI":"10.1039\/C5RA26302F","article-title":"Structure and chemistry of surface-doped Pt:SnO2 gas sensing materials","volume":"6","author":"Degler","year":"2016","journal-title":"RSC Adv."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1016\/j.snb.2019.02.107","article-title":"Microfluidically synthesized Au, Pd and AuPd nanoparticles supported on SnO2 for gas sensing applications","volume":"292","author":"Tofighi","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"336","DOI":"10.1016\/j.snb.2018.09.004","article-title":"Sensitivity of nanocrystalline tungsten oxide to CO and ammonia gas determined by surface catalysts","volume":"277","author":"Marikutsa","year":"2018","journal-title":"Sens. Actuators B Chem."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1109\/JSEN.2016.2620185","article-title":"An Investigation on Electrical and Hydrogen Sensing Characteristics of RF Sputtered ZnO Thin-Film with Palladium Schottky Contact","volume":"17","author":"Rajan","year":"2017","journal-title":"IEEE Sens. J."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"125017","DOI":"10.1088\/2053-1591\/aa9cb4","article-title":"Electrical and NO2 sensing characteristics of Pd\/ZnO nanoparticles based Schottky diode at room temperature","volume":"4","author":"Chandra","year":"2017","journal-title":"Mater. Res. Express"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"16294","DOI":"10.1016\/j.ijhydene.2017.05.135","article-title":"On-chip growth of patterned ZnO nanorod sensors with PdO decoration for enhancement of hydrogen-sensing performance","volume":"42","author":"Jiao","year":"2017","journal-title":"Int. J. Hydrog. Energy"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"243503","DOI":"10.1063\/1.1949707","article-title":"Hydrogen-selective sensing at room temperature with ZnO nanorods","volume":"86","author":"Wang","year":"2005","journal-title":"Appl. Phys. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"6461","DOI":"10.1016\/j.ceramint.2013.01.075","article-title":"Sol-gel synthesis of Pd doped ZnO nanorods for room temperature hydrogen sensing applications","volume":"39","author":"Kashif","year":"2013","journal-title":"Ceram. Int."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1021\/am302294v","article-title":"Outstanding H2 sensing performance of Pd nanoparticle-decorated ZnO nanorod arrays and the temperature-dependent sensing mechanisms","volume":"5","author":"Chang","year":"2013","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2469","DOI":"10.1039\/c2ra01016j","article-title":"Improvement in CO sensing characteristics by decorating ZnO nanorod arrays with Pd nanoparticles and the related mechanisms","volume":"2","author":"Chang","year":"2012","journal-title":"RSC Adv."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"84312","DOI":"10.1063\/1.3647310","article-title":"Enhanced H2 sensitivity at room temperature of ZnO nanowires functionalized by Pd nanoparticles","volume":"110","author":"Ren","year":"2011","journal-title":"J. Appl. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1016\/j.snb.2018.10.063","article-title":"NO2 Sensing properties of one-pot-synthesized ZnO nanowires with Pd functionalization","volume":"280","author":"Chen","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"628","DOI":"10.1016\/j.snb.2018.12.120","article-title":"Combination of Pd loading and electron beam irradiation for superior hydrogen sensing of electrospun ZnO nanofibers","volume":"284","author":"Kim","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"11116","DOI":"10.1021\/acsami.7b17877","article-title":"Improved Sensitivity with Low Limit of Detection of a Hydrogen Gas Sensor Based on rGO-Loaded Ni-Doped ZnO Nanostructures","volume":"10","author":"Bhati","year":"2018","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"34765","DOI":"10.1021\/acsami.8b12569","article-title":"High-Performance Nanowire Hydrogen Sensors by Exploiting the Synergistic Effect of Pd Nanoparticles and Metal\u2013Organic Framework Membranes","volume":"10","author":"Weber","year":"2018","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"297676","DOI":"10.1155\/2013\/297676","article-title":"Preparation, Characterization, and Mechanistic Understanding of Pd-Decorated ZnO Nanowires for Ethanol Sensing","volume":"2013","author":"Deng","year":"2013","journal-title":"J. Nanomater."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1261","DOI":"10.3762\/bjnano.5.140","article-title":"Effects of palladium on the optical and hydrogen sensing characteristics of Pd-doped ZnO nanoparticles","volume":"5","author":"Do","year":"2014","journal-title":"Beilstein J. Nanotechnol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"196","DOI":"10.1007\/s10832-007-9377-y","article-title":"CO gas sensing properties in Pd-added ZnO sensors","volume":"23","author":"Moon","year":"2009","journal-title":"J. Electroceram."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Baraton, M.I. (2009). Sensors based on technology \u201cnano-on-micro\u201d for wireless instruments preventing ecological and industrial catastrophes. Sensors for Environment, Health and Security, Springer.","DOI":"10.1007\/978-1-4020-9009-7"},{"key":"ref_38","unstructured":"Penney, D., Benignus, V., Kephalopoulos, S., Kotzias, D., Kleinman, M., and Verrier, A. (2010). Carbon monoxide. WHO Guidelines for Indoor Air Quality: Selected Pollutants, WHO Regional Office for Europe."},{"key":"ref_39","unstructured":"Thermo Scientifics (2020, November 10). Palladium. Transition Metal. Available online: https:\/\/xpssimplified.com\/elements\/palladium.php."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Davydov, A. (2003). Molecular Spectroscopy of Oxide Catalyst Surfaces, John Wiley & Sons.","DOI":"10.1002\/0470867981"},{"key":"ref_41","first-page":"2059","article-title":"Infrared spectrum of microcrystalline Zinc Oxide. electronic and vibrational contributions under different temperature and environmental conditions","volume":"2","author":"Boccuzzi","year":"1981","journal-title":"J. Chem. Soc. Faraday Trans. 2 Mol. Chem. Phys."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1016\/j.jcrysgro.2005.04.053","article-title":"Infrared spectroscopy of polycrystalline ZnO and ZnO:N thin films","volume":"281","author":"Keyes","year":"2005","journal-title":"J. Cryst. Growth"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"617","DOI":"10.1016\/0009-2614(79)87186-9","article-title":"IR detection of surface microscopic modes of microcrystalline ZnO","volume":"61","author":"Boccuzzi","year":"1979","journal-title":"Chem. Phys. Lett."},{"key":"ref_44","first-page":"1457","article-title":"Infrared study of CO2 adsorption on ZnO. Adsorption sites","volume":"78","author":"Saussey","year":"1982","journal-title":"J. Chem. Soc. Faraday Trans. 2 Mol. Chem. Phys."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1039\/df9715200033","article-title":"Infra-red spectroscopic studies of zinc oxide surfaces","volume":"52","author":"Atherton","year":"1971","journal-title":"Discuss. Faraday Soc."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"566","DOI":"10.1016\/j.snb.2007.07.036","article-title":"Theory of power laws for semiconductor gas sensor","volume":"128","author":"Yamazoe","year":"2008","journal-title":"Sens. Actuators B Chem."},{"key":"ref_47","unstructured":"Fierro, J.L.G. (2006). Gas Sensors Based on Semiconducting Metal Oxides. Metal Oxides: Chemistry and Applications, CRC Press."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"073111","DOI":"10.1063\/1.1866511","article-title":"Infrared spectroscopy of ZnO nanoparticles containing CO2 impurities","volume":"86","author":"McCluskey","year":"2005","journal-title":"Appl. Phys. Lett."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"2135","DOI":"10.1016\/0022-3697(67)90237-5","article-title":"Infrared study of oxygen adsorption on impure zinc oxide","volume":"28","author":"Smith","year":"1967","journal-title":"J. Phys. Chem. Solids"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"43","DOI":"10.3389\/fmats.2019.00043","article-title":"Effect of zinc oxide modification by indium oxide on microstructure, adsorbed surface species, and sensitivity to CO","volume":"6","author":"Marikutsa","year":"2019","journal-title":"Front. Mater."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"982","DOI":"10.1063\/1.1730907","article-title":"Infrared Absorption of Zinc Oxide and of Adsorbed CO2, I","volume":"32","author":"Matsushita","year":"1960","journal-title":"J. Chem. Phys."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"491","DOI":"10.1002\/open.201800044","article-title":"Exploring the interactions of Oxygen with defective ZnO","volume":"7","author":"Wang","year":"2018","journal-title":"ChemistryOpen"},{"key":"ref_53","first-page":"1","article-title":"Hydrogenation and Izomerization over Zinc Oxide","volume":"Volume 22","author":"Kokes","year":"1972","journal-title":"Advances in Catalysis"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"3537","DOI":"10.1039\/C7LC00810D","article-title":"Toward breath analysis on a chip for disease diagnosis using semiconductor-based chemiresistors: Recent progress and future perspectives","volume":"17","author":"Yoon","year":"2017","journal-title":"Lab Chip"},{"key":"ref_55","unstructured":"Nakamoto, K. (1997). Infrared and Raman Spectra of Inorganic and Coordination Compounds, John Wiley & Sons."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"535","DOI":"10.1139\/v61-064","article-title":"Infrared spectra of gases chemisorbed on zinc oxide","volume":"30","author":"Taylor","year":"1961","journal-title":"Can. J. Chem."},{"key":"ref_57","doi-asserted-by":"crossref","unstructured":"Ginley, D.S., Hosono, H., and Paine, D.C. (2011). Handbook on Transparent Conductors, Springer.","DOI":"10.1007\/978-1-4419-1638-9"},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"203","DOI":"10.1016\/j.susc.2015.08.043","article-title":"Promotion of CO oxidation on PdO (101) by adsorbed H2O","volume":"650","author":"Choi","year":"2016","journal-title":"Surf. Sci."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"9091","DOI":"10.1021\/la500743u","article-title":"Energetics of CO2 and H2O Adsorption on Zinc Oxide","volume":"30","author":"Ushakov","year":"2014","journal-title":"Langmuir"},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"1728","DOI":"10.1007\/s11172-017-1949-7","article-title":"Active sites on the surface of nanocrystalline semiconductor oxides ZnO and SnO2 and gas sensitivity","volume":"66","author":"Marikutsa","year":"2017","journal-title":"Russ. Chem. Bull."},{"key":"ref_61","first-page":"307","article-title":"Characterization of oxide surfaces and zeolites by carbon monoxide as an IR probe molecule","volume":"Volume 47","author":"Hadjiivanov","year":"2002","journal-title":"Advances in Catalysis"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/24\/7333\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T10:47:40Z","timestamp":1760179660000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/24\/7333"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,12,20]]},"references-count":61,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2020,12]]}},"alternative-id":["s20247333"],"URL":"https:\/\/doi.org\/10.3390\/s20247333","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,12,20]]}}}