{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,24]],"date-time":"2026-07-24T04:17:08Z","timestamp":1784866628390,"version":"3.55.0"},"reference-count":52,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2023,2,20]],"date-time":"2023-02-20T00:00:00Z","timestamp":1676851200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this study, a solid-state modified pH sensor with RF magnetron sputtering technology was developed. The sensor consists of an active electrode consisting of a titanium nitride (TiN) film with a protective membrane of Nafion and a reference glass electrode of Ag\/AgCl. The sensitivity of the pH sensor was investigated. Results show a sensor with excellent characteristics: sensitivity of 58.6 mV\/pH for pH values from 2 to 12, very short response time of approximately 12 s in neutral pH solutions, and stability of less than 0.9 mV in 10 min duration. Further improvement in the performance of the TiN sensor was studied by application of a Nafion protective membrane. Nafion improves the sensor sensitivity close to Nernstian by maintaining a linear response. This paves the way to implement TiN with Nafion protection to block any interference species during real time applications in biosensing and medical diagnostic pH sensors.<\/jats:p>","DOI":"10.3390\/s23042331","type":"journal-article","created":{"date-parts":[[2023,2,20]],"date-time":"2023-02-20T03:29:06Z","timestamp":1676863746000},"page":"2331","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Fabrication and Optimization of Nafion as a Protective Membrane for TiN-Based pH Sensors"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7784-797X","authenticated-orcid":false,"given":"Shimrith","family":"Paul Shylendra","sequence":"first","affiliation":[{"name":"School of Science, Edith Cowan University, Joondalup, WA 6027, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3666-2175","authenticated-orcid":false,"given":"Magdalena","family":"Wajrak","sequence":"additional","affiliation":[{"name":"School of Science, Edith Cowan University, Joondalup, WA 6027, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kamal","family":"Alameh","sequence":"additional","affiliation":[{"name":"School of Science, Edith Cowan University, Joondalup, WA 6027, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,2,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Nagy, G., and Nagy, L. (2015). Potentiometric Sensors, John Wiley & Sons, Inc.","DOI":"10.1002\/9781118684030.ch7"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2011","DOI":"10.1039\/c3an02195e","article-title":"A single-walled carbon nanotube thin film-based pH-sensing microfluidic chip","volume":"139","author":"Li","year":"2014","journal-title":"Analyst"},{"key":"ref_3","first-page":"8","article-title":"Modification in pH measurements for getting accurate pH values with different pH meters irrespective of aging and drifts in the meters","volume":"16","author":"Kulasekaran","year":"2015","journal-title":"Int. J. ChemTech. Res."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"01008","DOI":"10.1051\/matecconf\/20167901008","article-title":"Differential Sensor for PH Monitoring of Environmental Objects","volume":"79","author":"Romanenko","year":"2016","journal-title":"MATEC Web Conf."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"568","DOI":"10.1021\/acsmeasuresciau.2c00036","article-title":"A Solid-Contact Reference Electrode Based on Silver\/Silver Organic Insoluble Salt for Potentiometric Ion Sensing","volume":"2","author":"Gan","year":"2022","journal-title":"ACS Meas. Sci. Au"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.jart.2016.01.003","article-title":"Chemical sensor network for pH monitoring","volume":"14","author":"Garizado","year":"2016","journal-title":"J. Appl. Res. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Patil, P.H., Kulkarni, V.V., and Jadhav, S.A. (2022). An Overview of Recent Advancements in Conducting Polymer\u2013Metal Oxide Nanocomposites for Supercapacitor Application. J. Compos. Sci., 6.","DOI":"10.3390\/jcs6120363"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"22098","DOI":"10.1021\/jp407539c","article-title":"Preparation of RuO2\/TiO2 Mesoporous Heterostructures and Rationalization of Their Enhanced Photocatalytic Properties by Band Alignment Investigations","volume":"117","author":"Uddin","year":"2013","journal-title":"J. Phys. Chem. C."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"39101","DOI":"10.1038\/srep39101","article-title":"Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility","volume":"6","author":"Wedege","year":"2016","journal-title":"Sci. Rep."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"P\u00e1lla, T., Mirzahosseini, A., and Nosz\u00e1l, B. (2020). Species-Specific, pH-Independent, Standard Redox Potential of Selenocysteine and Selenocysteamine. Antioxidants, 9.","DOI":"10.3390\/antiox9060465"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1016\/j.talanta.2017.12.070","article-title":"Manufacture and application of RuO2 solid-state metal-oxide pH sensor to common beverages","volume":"180","author":"Lonsdale","year":"2018","journal-title":"Talanta"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"756","DOI":"10.3390\/coatings4040756","article-title":"Recent Developments in R.F. Magnetron Sputtered Thin Films for pH Sensing Applications\u2014An Overview","volume":"4","author":"Maurya","year":"2014","journal-title":"Coatings"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"6311","DOI":"10.1143\/JJAP.40.6311","article-title":"Titanium Nitride Membrane Application to Extended Gate Field Effect Transistor pH Sensor Using VLSI Technology","volume":"40","author":"Chin","year":"2001","journal-title":"Jpn. J. Appl. Phys."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"7790","DOI":"10.1021\/acs.jpcb.8b06493","article-title":"Inherent Acidity of Perfluorosulfonic Acid Ionomer Dispersions and Implications for Ink Aggregation","volume":"122","author":"Berlinger","year":"2018","journal-title":"J. Phys. Chem. B."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Li, S., Terao, K., and Sato, T. (2018). Colloidal Dispersion of a Perfluorosulfonated Ionomer in Water\u2013Methanol Mixtures. Polymers, 10.","DOI":"10.3390\/polym10010072"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"361","DOI":"10.1149\/07514.0361ecst","article-title":"Investigation of Solvent Effects on the Dispersion of Carbon Agglomerates and Nafion Ionomer Particles in Catalyst Inks Using Ultra Small Angle X-ray Scattering Method","volume":"75","author":"Yang","year":"2016","journal-title":"ECS Trans."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"6530","DOI":"10.1021\/acsami.6b12949","article-title":"Investigation of the Interaction between Nafion Ionomer and Surface Functionalized Carbon Black Using Both Ultrasmall Angle X-ray Scattering and Cryo-TEM","volume":"9","author":"Yang","year":"2017","journal-title":"ACS Appl. Mater. Interfaces."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1273","DOI":"10.1002\/elan.202100652","article-title":"Nafion\u00ae Coated Electropolymerised Flavanone-based pH Sensor","volume":"34","author":"Miranda","year":"2022","journal-title":"Electroanalysis"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1371","DOI":"10.1016\/j.petsci.2021.11.004","article-title":"Recent developments in high-performance Nafion membranes for hydrogen fuel cells applications","volume":"19","author":"Zhu","year":"2022","journal-title":"Pet. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"7776","DOI":"10.1021\/acsomega.8b01209","article-title":"Electrochemical Sensing of Biotin Using Nafion-Modified Boron-Doped Diamond Electrode","volume":"3","author":"Buzid","year":"2018","journal-title":"ACS Omega"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"102088","DOI":"10.1039\/C6RA17786G","article-title":"Impedimetric blood pH sensor based on MoS2 \u2013Nafion coated microelectrode","volume":"6","author":"Awasthi","year":"2016","journal-title":"RSC Adv."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Chen, Z., Patel, R., Berry, J., Keyes, C., Satterfield, C., Simmons, C., Neeson, A., Cao, X., and Wu, Q. (2022). Development of Screen-Printable Nafion Dispersion for Electrochemical Sensor. Appl. Sci., 12.","DOI":"10.3390\/app12136533"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3653","DOI":"10.1021\/la0470535","article-title":"Cast Thin Film Biosensor Design Based on a Nafion Backbone, a Multiwalled Carbon Nanotube Conduit, and a Glucose Oxidase Function","volume":"21","author":"Tsai","year":"2005","journal-title":"Langmuir"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Stozhko, N., Bukharinova, M., Galperin, L., and Brainina, K. (2018). A Nanostructured Sensor Based on Gold Nanoparticles and Nafion for Determination of Uric Acid. Biosensors, 8.","DOI":"10.3390\/bios8010021"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"361","DOI":"10.1016\/0142-9612(91)90003-S","article-title":"Preliminary in vivo biocompatibility studies on perfluorosulphonic acid polymer membranes for biosensor applications","volume":"12","author":"Turner","year":"1991","journal-title":"Biomaterials"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"4811","DOI":"10.1021\/ja00382a013","article-title":"Polymer films on electrodes. 8. Investigation of charge-transport mechanisms in Nafion polymer modified electrodes","volume":"104","author":"White","year":"1982","journal-title":"J. Am. Chem. Soc."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"880","DOI":"10.1002\/elan.201600591","article-title":"AgNP\/Bi\/Nafion-modified Disposable Electrodes for Sensitive Zn(II), Cd(II), and Pb(II) Detection in Aerosol Samples","volume":"29","author":"Mettakoonpitak","year":"2017","journal-title":"Electroanalysis"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Myndrul, V., Iatsunskyi, I., Babayevska, N., Jarek, M., and Jesionowski, T. (2022). Effect of Electrode Modification with Chitosan and Nafion\u00ae on the Efficiency of Real-Time Enzyme Glucose Biosensors Based on ZnO Tetrapods. Materials, 15.","DOI":"10.3390\/ma15134672"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Guimer\u00e0, X., Moya, A., Dorado, A.D., Illa, X., Villa, R., Gabriel, D., Gamisans, X., and Gabriel, G. (2019). A Minimally Invasive Microsensor Specially Designed for Simultaneous Dissolved Oxygen and pH Biofilm Profiling. Sensors, 19.","DOI":"10.3390\/s19214747"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"023001","DOI":"10.1088\/0953-8984\/28\/2\/023001","article-title":"Grotthuss mechanisms: From proton transport in proton wires to bioprotonic devices","volume":"28","author":"Miyake","year":"2016","journal-title":"J. Phys. Condens. Matter."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1150","DOI":"10.1021\/acscentsci.0c00340","article-title":"Slow Proton Transfer in Nanoconfined Water","volume":"6","author":"Sofronov","year":"2020","journal-title":"ACS Cent. Sci."},{"key":"ref_32","unstructured":"Majsztrik, P.W. (2008). Mechanical and Transport Properties of NafionRTM for Pem Fuel Cells; Temperature and Hydration Effects. [Master\u2019s Thesis, Princeton University]."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1016\/0925-4005(94)01254-7","article-title":"A solid-state pH sensor based on a Nafion-coated iridium oxide indicator electrode and a polymer-based silver chloride reference electrode","volume":"22","author":"Kinlen","year":"1994","journal-title":"Sens. Actuators B Chem."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1600660","DOI":"10.1002\/admi.201600660","article-title":"Lithium Salt Inclusion as a Strategy for Improving the Li + Conductivity of Nafion Membranes in Aprotic Systems","volume":"3","author":"Yang","year":"2016","journal-title":"Adv. Mater. Interfaces"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1366\/000370203321165232","article-title":"Evaluation of Acridine in Nafion as a Fluorescence-Lifetime-Based pH Sensor","volume":"57","author":"Ryder","year":"2003","journal-title":"Appl. Spectrosc."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1016\/j.talanta.2015.09.069","article-title":"Potentiometric RuO2\u2013Ta2O5 pH sensors fabricated using thick film and LTCC technologies","volume":"147","author":"Manjakkal","year":"2016","journal-title":"Talanta"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"416","DOI":"10.1016\/1350-4533(94)00006-U","article-title":"Effect of interference on the performance of glucose enzyme electrodes using Nafion\u00ae coatings","volume":"17","author":"Vaidya","year":"1995","journal-title":"Med. Eng. Phys."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"107511","DOI":"10.1149\/1945-7111\/ac2d3c","article-title":"Nafion Protective Membrane Enables Using Ruthenium Oxide Electrodes for pH Measurement in Milk","volume":"168","author":"Lazouskaya","year":"2021","journal-title":"J. Electrochem. Soc."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"2300","DOI":"10.1002\/elan.201700302","article-title":"Enzyme Deposition by Polydimethylsiloxane Stamping for Biosensor Fabrication","volume":"29","author":"Wang","year":"2017","journal-title":"Electroanalysis"},{"key":"ref_40","unstructured":"Wang, B. (2016). Biosensors Fabrication by Polydimethylsiloxane Stamping and Nanostructured Platinum for Construction of Improved Reference and Sensing Electrodes, University of California."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"13643","DOI":"10.1016\/j.ijhydene.2018.02.097","article-title":"The effect of Nafion membrane fouling on the power generation of a microbial fuel cell","volume":"45","author":"Flimban","year":"2020","journal-title":"Int. J. Hydrogen Energy"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1227","DOI":"10.2116\/analsci.22.1227","article-title":"An Improved Colorimetric Determination of Lead(II) in the Presence of Nonionic Surfactant","volume":"22","author":"Akl","year":"2006","journal-title":"Anal. Sci."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Shylendra, S.P., Wajrak, M., Alameh, K., and Kang, J.J. (2023). Nafion Modified Titanium Nitride pH Sensor for Future Biomedical Applications. Sensors, 23.","DOI":"10.3390\/s23020699"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Lonsdale, W., Wajrak, M., and Alameh, K. (2017). RuO2 pH Sensor with Super-Glue-Inspired Reference Electrode. Sensors, 17.","DOI":"10.3390\/s17092036"},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Paul Shylendra, S., Lonsdale, W., Wajrak, M., Nur-E-Alam, M., and Alameh, K. (2020). Titanium Nitride Thin Film Based Low-Redox-Interference Potentiometric pH Sensing Electrodes. Sensors, 21.","DOI":"10.3390\/s21010042"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"190","DOI":"10.1016\/j.memsci.2007.04.019","article-title":"The effects of thermal annealing on commercial Nafion\u00ae membranes","volume":"298","author":"Hensley","year":"2007","journal-title":"J. Memb. Sci."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"7213","DOI":"10.1016\/j.jpowsour.2010.05.005","article-title":"Effect of cations (Na+, Ca2+, Fe3+) on the conductivity of a Nafion membrane","volume":"195","author":"Hongsirikarn","year":"2010","journal-title":"J. Power Sources"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"10346","DOI":"10.1007\/s10853-019-03652-z","article-title":"Superior-performance TiN films sputtered for capacitor electrodes","volume":"54","author":"Sun","year":"2019","journal-title":"J. Mater. Sci."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Ramirez-Nava, J., Mart\u00ednez-Castrej\u00f3n, M., Garc\u00eda-Mesino, R.L., L\u00f3pez-D\u00edaz, J.A., Talavera-Mendoza, O., Sarmiento-Villagrana, A., Rojano, F., and Hern\u00e1ndez-Flores, G. (2021). The Implications of Membranes Used as Separators in Microbial Fuel Cells. Membranes, 11.","DOI":"10.3390\/membranes11100738"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"7920","DOI":"10.1021\/ma301289v","article-title":"Effect of Confinement on Structure, Water Solubility, and Water Transport in Nafion Thin Films","volume":"45","author":"Eastman","year":"2012","journal-title":"Macromolecules"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Uppuluri, K., Lazouskaya, M., Szwagierczak, D., Zaraska, K., and Tamm, M. (2021). Fabrication, Potentiometric Characterization, and Application of Screen-Printed RuO2 pH Electrodes for Water Quality Testing. Sensors, 21.","DOI":"10.3390\/s21165399"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"3080","DOI":"10.20964\/2018.03.04","article-title":"Development and Performance of an All-Solid-Stated pH Sensor Based on Modified Membranes","volume":"13","author":"Xu","year":"2018","journal-title":"Int. J. Electrochem. Sci."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/4\/2331\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T18:37:01Z","timestamp":1760121421000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/4\/2331"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,2,20]]},"references-count":52,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2023,2]]}},"alternative-id":["s23042331"],"URL":"https:\/\/doi.org\/10.3390\/s23042331","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,2,20]]}}}