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 −6 V/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.

Cryoconcentration of flavonoid extract for enhanced biophotovoltaics and pH sensitive thin films

“…Inkjet printing of the extract closely followed our similar procedures for printing graphene inks . For preparing inkjet‐printed thin film biodetectors, aliquots (3 mL) of extract were filtered through a 0.45 µm.…”

“…The printed line morphology resulting from the drop spacing and the working temperature control edge effects (known as the coffee ring effect). Our previous work shows that average film thickness is between 3 and 5 µm, classifying this structure as a thin film . A circular array was designed using computer‐aided design (CAD software) and inkjet printed.…”

“…Based on I-E curves, the short circuit current density (J sc ), open circuit voltage (V oc ), maximum power output (P max ), voltage at max power (V mp ), current density at max power (J mp ), form factor (FF), and solar conversion efficiency (g) were calculated using the methods reported by Hug et al 52 Inkjet printing of the extract closely followed our similar procedures for printing graphene inks. [53][54][55] For preparing inkjet-printed thin film biodetectors, aliquots (3 mL) of extract were filtered through a 0.45 mm. Polytetrafluoroethylene (PTFE) syringe filter and then loaded into an inkjet printer cartridge (1.5 mL max.…”

“…Our previous work shows that average film thickness is between 3 and 5 mm, classifying this structure as a thin film. [53][54][55] A circular array was designed using computer-aided design (CAD software) and inkjet printed. For unbuffered calibration tests, pH was adjusted with 3M HCl or 2M NaOH, and then 5 mL aliquots were drop cast onto the pH sensitive film.…”

Recent Advances on 3D Printing Technique for Thermal‐Related Applications

“…The authors used these fibers to make fabrics. [41,42] Esther and co-workers developed a graphene oxide based ink with optimum rheological properties for 3D printing. [40] Graphene is another candidate for printing thermal devices as it offers excellent mechanical and thermal properties.…”