Publications

Forthcoming
Aksay, I. A. ; Korkut, S. A. ; Kaczmarczyk, J. ; Gurdag, S. ; Korkmaz, D. Graphene dispersions, Forthcoming.Abstract
Method of making a composition comprising graphene sheets and at least one solvent, comprising dispersing a mixture of graphene sheets and graphite particles in a solvent, wherein the graphite particles have more than about 50 layers, separating the graphene sheets and the graphite particles to obtain a dispersion of graphene sheets that contains no more than 25% of graphite particles having more than about 50 layers, based on the total number of graphite particles and graphene sheets, and flocculating the dispersion of graphene sheets. The flocculated dispersion can be added to a polymer matrix to make a composite. The composite can be formed into articles.
Pope, M. A. ; Alain-Rizzo, V. ; Dabbs, D. M. ; Lettow, J. S. ; Aksay, I. A. Batteries incorporating graphene membranes for extending the cycle-life of lithium-ion batteries, Forthcoming.Abstract
Embodiments of the present invention relate to energy storage devices and associated methods of manufacture. In one embodiment, an energy storage device comprises an electrolyte. An anode is at least partially exposed to the electrolyte. A selectively permeable membrane comprising a graphene-based material is positioned proximate to the anode. The selectively permeable membrane reduces a quantity of a component that is included in the electrolyte from contacting the anode and thereby reduces degradation of the anode.
Aksay, I. A. ; Sallah, K. Conducting elastomers, Forthcoming.Abstract
The present invention relates to conducting elastomers and assocd. fabrication methods. In one embodiment, the conducting elastomer comprises a filler powder and a polymer. The filler powder includes carbon black and functionalized graphene sheets. The polymer has a mol. wt. of about 200 g/mol to about 5000 g/mol and is a liquid at room temperature.
Aksay, I. A. ; Dabbs, D. M. ; Pope, M. A. Electrodes incorporating composites of graphene and selenium-sulfur compounds for improved rechargeable lithium batteries. Forthcoming.Abstract
Embodiments of the present invention relate to battery electrodes incorporating composites of graphene and selenium-sulfur compds. for improved rechargeable batteries. In one embodiment, a conductive compn. comprises a conductive compn. having a Se-S compd., a conductive additive. The Se-S compd. is present as SexS8-x, wherein x is greater than zero and less than eight.
Aksay, I. A. ; Alain-Rizzo, V. ; Bozlar, M. ; Bozym, D. J. ; Dabbs, D. M. ; Szamreta, N. ; Ustundag, C. B. Electrohydrodynamically formed structures of carbonaceous material, Forthcoming.Abstract
A method for the electrohydrodynamic deposition of carbonaceous materials utilizing an electrohydrodynamic cell comprising two electrodes comprised of a conductive material, by first combining a solid phase comprising a carbonaceous material and a suspension medium, placing the suspension between the electrodes, applying an electric field in a first direction, varying the intensity of the electric field sufficiently to drive lateral movement, increasing the electric field to stop the lateral transport and fix the layers in place, then removing the applied field and removing the electrodes. Among the many different possibilities contemplated, the method may advantageously utilize: varying the spacing between the electrodes; removing the buildup from one or both electrodes; placing the electrodes into different suspensions; adjusting the concentration, pH, or temperature of the suspension(s); and varying the direction, intensity or duration of the electric fields.
2018
Aksay, I. A. ; Korkut, S. ; Pope, M. ; Punckt, C. Graphene-ionic liquid composites, 2018.Abstract
Method of making a graphene-ionic liquid composite. The composite can be used to make electrodes for energy storage devices, such as batteries and supercapacitors.
Prud'homme, R. K. ; Aksay, I. A. Thermal overload device containing a polymer composition containing thermally exfoliated graphite oxide and method of making the same, 2018.Abstract
A thermal overload device containing a polymer composite, which contains at least one polymer and a modified graphite oxide material, containing thermally exfoliated graphite oxide having a surface area of from about 300 m2/g to 2600 m2/g, and a method of making the same.
Aksay, I. A. ; Milius, D. L. ; Korkut, S. ; Prud'homme, R. K. Functionalized graphene sheets having high carbon to oxygen ratios, 2018.Abstract
Functionalized graphene sheets having a carbon to oxygen molar ratio of at least about 23:1 and method of preparing the same.
Aksay, I. A. ; Buyukdincer, B. ; Javaherian, N. ; Lettow, J. S. ; Pino, G. ; Redmond, K. ; Yildirim, I. O. Reinforced polymeric articles, 2018.Abstract
Polymeric article reinforced with a reinforcing component. The reinforcing component includes a composition made from at least one polymer and graphene sheets.
Crain, J. M. ; Lettow, J. S. ; Aksay, I. A. ; Korkut, S. ; Chiang, K. S. ; Chen, C. - H. ; Prud'homme, R. K. Printed electronics, 2018.Abstract
Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.
Pan, S. ; Aksay, I. A. ; Prud'homme, R. K. Multifunctional graphene-silicone elastomer nanocomposite, method of making the same, and uses thereof, 2018.Abstract
A nanocomposite composition having a silicone elastomer matrix having therein a filler loading of greater than 0.05 wt %, based on total nanocomposite weight, wherein the filler is functional graphene sheets (FGS) having a surface area of from 300 m2/g to 2630 m2/g; and a method for producing the nanocomposite and uses thereof.
2017
Prud’homme, R. K. ; Aksay, I. A. Conductive circuit containing a polymer composition containing thermally exfoliated graphite oxide and method of making the same, 2017.Abstract
A conductive circuit containing a polymer composite, which contains at least one polymer and a modified graphite oxide material, containing thermally exfoliated graphite oxide having a surface area of from about 300 m2/g to 2600 m2/g, and a method of making the same.
Aksay, I. A. ; Milius, D. L. ; Korkut, S. ; Prud'homme, R. K. Functionalized Graphene Sheets having High Carbon to Oxygen Ratios, 2017.Abstract
The present invention relates to functionalized graphene sheets having low oxygen content and methods for their prepartion.
Alifierakis, M. ; Sallah, K. S. ; Aksay, I. A. ; Prevost, J. H. Reversible Cluster Aggregation and Growth Model for Graphene Suspensions. AIChE Journal 2017, 63, 5462-5473.Abstract
We present a reversible cluster aggregation model for 2-D macromolecules represented by line segments in 2-D; and, we use it to describe the aggregation process of functionalized graphene particles in an aqueous SDS surfactant solution. The model produces clusters with similar sizes and structures as a function of SDS concentration in agreement with experiments and predicts the existence of a critical surfactant concentration (C-crit) beyond which thermodynamically stable graphene suspensions form. Around C-crit, particles form dense clusters rapidly and sediment. At C << C-crit, a contiguous ramified network of graphene gel forms which also densifies, but at a slower rate, and sediments with time. The deaggregation-reaggregation mechanism of our model captures the restructuring of the large aggregates towards a graphite-like structure for the low SDS concentrations. (C) 2017 American Institute of Chemical Engineers
2016
Uralcan, B. ; Aksay, I. A. ; Debenedetti, P. G. ; Limmer, D. T. Concentration Fluctuations and Capacitive Response in Dense Ionic Solutions. Journal of Physical Chemistry Letters 2016, 7 2333-2338.Abstract
We use molecular dynamics simulations in a constant potential ensemble to study the effects of solution composition on the electrochemical response of a double layer capacitor. We find that the capacitance first increases with ion concentration following its expected ideal solution behavior but decreases upon approaching a pure ionic liquid in agreement with recent experimental observations. The nonmonotonic behavior of the capacitance as a function of ion concentration results from the competition between the independent motion of solvated ions in the dilute regime and solvation fluctuations in the concentrated regime. Mirroring the capacitance, we find that the characteristic decay length of charge density correlations away from the electrode is also nonmonotonic. The correlation length first decreases with ion concentration as a result of better electrostatic screening but increases with ion concentration as a result of enhanced steric interactions. When charge fluctuations induced by correlated ion-solvent fluctuations are large relative to those induced by the pure ionic liquid, such capacitive behavior is expected to be generic.
Bozym, D. J. ; Korkut, S. ; Pope, M. A. ; Aksay, I. A. Dehydrated Sucrose Nanoparticles as Spacers for Graphene-Ionic Liquid Supercapacitor Electrodes. ACS Sustainable Chemistry & Engineering 2016, 4 7167-7174.Abstract
The addition of dehydrated sucrose nano particles increases the gravimetric capacitance of electrochemical double-layer capacitor electrodes produced via the evaporative consolidation of graphene oxide-water-ionic liquid gels by more than two-fold. Dehydrated sucrose adsorbs onto graphene oxide and serves as a spacer, preventing the graphene oxide from restacking during solvent evaporation. Despite 61 wt % of the solids being electrochemically inactive dehydrated sucrose nanoparticles, the best electrodes achieved an energy density of similar to 13.3 Wh/kg, accounting for the total mass of all electrode components.
Aksay, I. A. ; Korkut, S. ; Pope, M. ; Punckt, C. Graphene-Ionic Liquid Composites, 2016.Abstract
Method of making a graphene-ionic liquid composite. The composite can be used to make electrodes for energy storage devices, such as batteries and supercapacitors. Disclosed and claimed herein is method of making a graphene-ionic liquid composite, comprising combining a graphene source with at least one ionic liquid and heating the combination at a temperature of at least about 130 °C.
Roy-Mayhew, J. D. ; Pope, M. A. ; Punckt, C. ; Aksay, I. A. Intrinsic Catalytic Activity of Graphene Defects for the Co-II/III(bpy)(3) Dye-Sensitized Solar Cell Redox Mediator. ACS Applied Materials & Interfaces 2016, 8 9134-9141.Abstract
We demonstrate that functionalized graphene, rich with lattice defects but lean with oxygen sites, catalyzes the reduction of Co-III(bpy)(3) as well as platinum does, exhibiting a rate of heterogeneous electron transfer, k(0), of similar to 6 x 10(-3) cm/s. We show this rate to be an order of magnitude higher than on oxygen-site-rich graphene oxide, and over 2 orders of magnitude higher than on the basal plane of graphite (as a surrogate for pristine graphene). Furthermore, dye-sensitized solar. cells using defect-rich graphene monolayers perform similarly to those using platinum nanoparticles as the catalyst.
Liu, J. ; Aksay, I. A. ; Kou, R. ; Wang, D. H. Mesoporous Metal Oxide Graphene Nanocomposite Materials, 2016.Abstract
A nanocomposite material formed of graphene and a mesoporous metal oxide having a demonstrated specific capacity of more than 200 F/g with particular utility when employed in supercapacitor applications. A method for making these nanocomposite materials by first forming a mixture of graphene, a surfactant, and a metal oxide precursor, precipitating the metal oxide precursor with the surfactant from the mixture to form a mesoporous metal oxide. The mesoporous metal oxide is then deposited onto a surface of the graphene.
Pan, S. Y. ; Aksay, I. A. ; Prud'homme, R. K. Multifunctional Graphene-Silicone Elastomer Nanocomposite, Method of Making the Same, and Uses Thereof, 2016.Abstract
A nanocomposite composition having a silicone elastomer matrix having therein a filler loading of greater than 0.05 wt %, based on total nanocomposite weight, wherein the filler is functional graphene sheets (FGS) having a surface area of from 300 m2/g to 2630 m2/g; and a method for producing the nanocomposite and uses thereof.

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