AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Crumpling of Graphene-oxide by Evaporative Confinement in Nano-droplets using Electrospray
SHALINEE KAVADIYA, Ramesh Raliya, Michael Schrock, Pratim Biswas, Washington University in St. Louis
Abstract Number: 155 Working Group: Nanoparticles and Materials Synthesis
Abstract Crumpled graphene oxide (CGO) has attracted significant attention recently due to its remarkable properties, including high surface area and dispersion as a single crumpled ball, unlike graphene oxide (GO) sheets, which tend to restack. CGO has been synthesized through the evaporative confinement of GO sheets in a droplet$^1. Furthermore, as the solvent evaporates from the droplet, a capillary force is induced on the GO sheets, resulting in their crumpling. Previously used techniques include spray drying, furnace aerosol reactor, and electrospray. However, these techniques were all demonstrated at elevated temperature environments for complete solvent evaporation or the addition of a crumple-inducing material. Such techniques also produce larger crumpled structures, and have not demonstrated the fabrication of nanometer sized particles.
In this study, an electrospray was used to produce CGO at sizes <100 nm under ambient conditions and without the use of any crumpling agent. Nanometer-sized crumpled particles are favorable in many applications due to their high surface area to volume ratio, high packing efficiency, and easy surface decoration. The effect of various process parameters such as substrate-to-nozzle distance, GO concentration and flow rate (droplet size) was investigated on the crumpling force and the crumpled particle size. Crumpled particles were characterized on-line using scanning mobility particle sizer (SMPS) and off-line using electron microscopy. Effects of these parameters were then linked to the characteristic times -- namely, time for the complete solvent evaporation (τ$_e), residence time of the droplet (τ$_(res)), and the time for the charge droplet to reach Rayleigh limit (τ$_(ray)). The size distribution of the crumpled particles was observed to be bimodal mainly as a result of the charged droplet break-up. Furthermore, another interesting morphology of thread-like morphology of GO particles were produced under certain experimental conditions. Finally, the synthesis and deposition of CGO at ambient conditions provide flexibility in substrate selection and enables a variety of applications.
Reference:
1. Wang et. al., J. Phys. Chem. Lett., 2012, 3, 3228−3233.