Advances in solution-phase graphene patterning has provided a facile route for rapid, low-cost and scalable manufacturing of electrochemical devices, even on flexible substrates. While graphene possesses advantageous electrochemical properties of high surface area and fast heterogenous charge transport, these properties are attributed to the edge planes and defect sites, not the basal plane. Herein, we demonstrate enhancement of the electroactive nature of patterned solution-phase graphene by increasing the porosity and edge planes through the construction of a multidimensional architecture via salt impregnated inkjet maskless lithography (SIIML) and CO 2 laser annealing. Various sized macroscale pores (<25 to ∼250 μm) are patterned directly in the graphene surface by incorporating porogens ( i.e. , salt crystals) in the graphene ink which act as hard templates for pore formation and are later dissolved in water. Subsequently, microsized pores (∼100 nm to 2 μm in width) with edge plane defects are etched in the graphene lattice structure by laser annealing with a CO 2 laser, simultaneously improving electrical conductivity by nearly three orders of magnitude (sheet resistance decreases from >10 000 to ∼50 Ω sq −1 ). We demonstrate that this multidimensional porous graphene fabrication method can improve electrochemical device performance through design and manufacture of an electrochemical organophosphate biosensor that uses the enzyme acetylcholinesterase for detection. This pesticide biosensor exhibits enhanced sensitivity to acetylthiocholine compared to graphene without macropores (28.3 μA nM −1 to 13.3 μA nM −1 ) and when inhibited by organophosphate pesticides (paraoxon) has a wide linear range (10 nM to 500 nM), low limit of detection (0.6 nM), and high sensitivity (12.4 nA nM −1 ). Moreover, this fabrication method is capable of patterning complex geometries [ i.e. interdigitated electrodes (IDEs)] even on flexible surfaces as demonstrated by an IDE supercapacitor made of SIIML graphene on a heat sensitive polymer substrate. The supercapacitor demonstrates a high energy density of 0.25 mW h cm −3 at a power density of 0.3 W cm −3 . These electrochemical devices demonstrate the benefit of using SIIML and CO 2 laser annealing for patterning graphene electrodes with a multidimensional porous surface even on flexible substrates and is therefore a platform technology which could be applied to a variety of different biosensors and other electrochemical devices.
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Pore‐scale Study of Ion Transport Mechanisms in Inhomogeneously Charged Nanoporous Rocks: Impacts of Interface Properties on Macroscopic Transport
The electrokinetic transport mechanisms of multispecies ions through 3‐D nanoporous rocks with chemical reaction at the solid‐aqueous solution interfaces are investigated. We systematically study the multiphysics transport phenomena by considering either inhomogeneous (local surface charge based on local pH and ion concentrations) or prescribed homogeneous surface charge at solid‐aqueous solution interface while the pores are screened via electric double layers. We develop a lattice Boltzmann numerical framework to solve the set of governing equations (Poisson‐Nernst‐Planck plus Navier–Stokes). Our modeling results reveal that the averaged local electric potential of the nanoporous rock is significantly underestimated (about 83%) when a homogeneous surface charge is prescribed based on the bulk solution properties. It is shown that increasing the porosity of the nanoporous media considerably increases the absolute values and inhomogeneity of the surface charge, which means that while the electric double layers screened the pores, increasing the porosity enhances the ion selectivity of the porous medium. When the scenario with inhomogeneous charge is taken into account, the predicted electroosmotic permeability and tortuosity are higher in comparison with the prescribed homogeneous case. Moreover, we have studied the electrostatic tortuosity, coupling coefficient, and the effective excess charge density of the nanoporous rocks. The results demonstrate that ignoring the inhomogeneity of surface charges may cause erroneous prediction of the ion transport through porous rocks with chemically active surfaces.
more » « less- NSF-PAR ID:
- 10457245
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Solid Earth
- Volume:
- 124
- Issue:
- 6
- ISSN:
- 2169-9313
- Page Range / eLocation ID:
- p. 5387-5407
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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