Hydrophobic laser-induced graphene potentiometric ion-selective electrodes for nitrate sensing

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Hartfiel, Lindsey
Chen, Bolin
Van Belle, Brian
Soupir, Michelle
Smith, Emily
McLamore, Eric
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Mechanical EngineeringAgricultural and Biosystems EngineeringFood Science and Human NutritionVirtual Reality Applications CenterCivil, Construction and Environmental EngineeringChemistryAmes Laboratory
Current solid-contact ion-selective electrodes (ISEs) suffer from signal-to-noise drift and short lifespans partly due to water uptake and the development of an aqueous layer between the transducer and ion-selective membrane. To address these challenges, we report on a nitrate ISE based on hydrophobic laser-induced graphene (LIG) coated with a poly(vinyl) chloride–based nitrate selective membrane. The hydrophobic LIG was created using a polyimide substrate and a double lasing process under ambient conditions (air at 23.0 ± 1.0 °C) that resulted in a static water contact angle of 135.5 ± 0.7° (mean ± standard deviation) in wettability testing. The LIG–ISE displayed a Nernstian response of − 58.17 ± 4.21 mV dec−1 and a limit-of-detection (LOD) of 6.01 ± 1.44 µM. Constant current chronopotentiometry and a water layer test were used to evaluate the potential (emf) signal stability with similar performance to previously published work with graphene-based ISEs. Using a portable potentiostat, the sensor displayed comparable (p > 0.05) results to a US Environmental Protection Agency (EPA)–accepted analytical method when analyzing water samples collected from two lakes in Ames, IA. The sensors were stored in surface water samples for 5 weeks and displayed nonsignificant difference in performance (LOD and sensitivity). These results, combined with a rapid and low-cost fabrication technique, make the development of hydrophobic LIG–ISEs appealing for a wide range of long-term in situ surface water quality applications.
This version of the article has been accepted for publication after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but it is not the Version of Record and does not reflect post-acceptance improvements or any corrections. The Version of Record is available online at DOI: 10.1007/s00604-022-05233-5. Copyright 2022 The Author(s). Posted with permission.
Ion-selective electrodes (ISE), Solid contact, PVC membrane, Graphene, Potentiometry, Water quality, Agricultural nutrients