Exfoliation and Spray Deposition of Graphene Nanoplatelets in Ethyl Acetate and Acetone: Implications for Additive Manufacturing of Low-Cost Electrodes and Heat Sinks

Nonaqueous dispersions of graphene nanoplatelets (GrNPs)can beused to prepare thin films and coatings free of surfactants, but typicallyinvolve polar organic solvents with high boiling points and low exposurelimits. Here, we describe the mechanochemical exfoliation and dispersionof GrNPs in volatile aprotic solvents such as ethyl acetate (EtOAc)and acetone, which rank favorably in green solvent selection guides.GrNPs in powder form were exfoliated with a solvent on a horizontalball mill for 48 h and then sonicated at moderate power to producesuspensions in excess of 300 & mu;g/mL with minimum loss of dispersionstability over 7 weeks at room temperature. Atomic force microscopyof individual particles indicates a median thickness and lateral widthof 8-10 layers and 180 nm, respectively. GrNP films can bedeposited by conventional airbrush equipment with a dry time of secondsand applied as layers and coatings that enhance the reproducibilityand performance of electronic devices. We demonstrate the utilityof spray-coated GrNPs as contact layers for low-cost electrochemicalsensing with improvements in intrabatch reproducibility and as conformalcoatings on metal heat sinks with enhanced rates of heat dissipation.