title: Enabling Inkjet Printed Graphene for Ion Selective Electrodes with Postprint Thermal Annealing.
abstract: Inkjet printed graphene (IPG) has recently shown tremendous promise in reducing the cost and complexity of graphene circuit fabrication. Herein we demonstrate, for the first time, the fabrication of an ion selective electrode (ISE) with IPG. A thermal annealing process in a nitrogen ambient environment converts the IPG into a highly conductive electrode (sheet resistance changes from 52.8 ± 7.4 MΩ/□ for unannealed graphene to 172.7 ± 33.3 Ω/□ for graphene annealed at 950 °C). Raman spectroscopy and field emission scanning electron microscopy (FESEM) analysis reveals that the printed graphene flakes begin to smooth at an annealing temperature of 500 °C and then become more porous and more electrically conductive when annealed at temperatures of 650 °C and above. The resultant thermally annealed, IPG electrodes are converted into potassium ISEs via functionalization with a poly(vinyl chloride) (PVC) membrane and valinomycin ionophore. The developed potassium ISE displays a wide linear sensing range (0.01-100 mM), a low detection limit (7 μM), minimal drift (8.6 × 10-6V/s), and a negligible interference during electrochemical potassium sensing against the backdrop of interfering ions [i.e., sodium (Na), magnesium (Mg), and calcium (Ca)] and artificial eccrine perspiration. Thus, the IPG ISE shows potential for potassium detection in a wide variety of human fluids including plasma, serum, and sweat.
authors.affiliation: Mechanical Engineering Department, Iowa State University , Ames, Iowa 50011, United States.
authors.forename: Qing
authors.initials: Q
authors.lastname: He
authors.affiliation: Mechanical Engineering Department, Iowa State University , Ames, Iowa 50011, United States.|Ames Laboratory, Ames, Iowa 50011, United States.
authors.forename: Suprem R
authors.initials: SR
authors.lastname: Das
authors.affiliation: Mechanical Engineering Department, Iowa State University , Ames, Iowa 50011, United States.
authors.forename: Nathaniel T
authors.initials: NT
authors.lastname: Garland
authors.affiliation: Materials Analysis and Research Laboratory, Iowa State University , Ames, Iowa 50010, United States.
authors.forename: Dapeng
authors.identifier: http://orcid.org/0000-0001-7600-7071
authors.initials: D
authors.lastname: Jing
authors.affiliation: Mechanical Engineering Department, Iowa State University , Ames, Iowa 50011, United States.
authors.forename: John A
authors.initials: JA
authors.lastname: Hondred
authors.affiliation: Mechanical Engineering Department, Iowa State University , Ames, Iowa 50011, United States.
authors.forename: Allison A
authors.initials: AA
authors.lastname: Cargill
authors.affiliation: Mechanical Engineering Department, Iowa State University , Ames, Iowa 50011, United States.
authors.forename: Shaowei
authors.initials: S
authors.lastname: Ding
authors.affiliation: Biomedical Research Laboratory, Department of Chemistry, VHNSN College (Autonomous) , Virudhunagar 626 001, Tamil Nadu, India.
authors.forename: Chandran
authors.initials: C
authors.lastname: Karunakaran
authors.affiliation: Mechanical Engineering Department, Iowa State University , Ames, Iowa 50011, United States.|Ames Laboratory, Ames, Iowa 50011, United States.
authors.forename: Jonathan C
authors.identifier: http://orcid.org/0000-0001-7065-1077
authors.initials: JC
authors.lastname: Claussen
keywords: graphene; inkjet printing; ion selective electrode; potassium; potentiometry; thermal annealing