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Block Copolymer Assisted Fabrication of Graphene/Carbon Nanotube Hybrid Architectures and Their Application in Supercapacitors Aaron S. George1, Maziar Ghazinejad2,3, Wei Wang1,3, Isaac Ruiz3, Mihrimah Ozkan1,3, Cengiz S. Ozkan1,2 1

Materials Science and Engineering Program, University of California Riverside, CA 92521, USA 2 Department of Mechanical Engineering, University of California Riverside, CA 92521, USA 3 Department of Electrical Engineering, University of California Riverside, CA 92521, USA Abstract Sustainable energy is currently limited by the ability of materials to store energy and deliver it on demand. Allotropes of carbon are attractive for their potential for use in energy storage due to low weight, high chemical stability and low production cost. Carbon nanotubes and graphene can be combined to provide an effective three-dimensional material with high conductivity and high surface area. We demonstrate the use of block copolymers to obtain patterned arrays of iron nanoparticles which give rise to ordered carbon nanotubes with good size distribution. A one-step chemical vapor deposition process for large-area fabrication of the graphene and carbon nanotube hybrid structure is described. Following chemical vapor deposition the hybrid material is demonstrated in a supercapacitor device. The fabricated supercapacitor exhibits high electrical conductivity, and has potential for extremely high energy storage capability. Introduction One of the current obstacles for nanotechnology research is the development of effective methodologies that allow for the preparation of materials on a few nm scale range. This challenge has been recently been addressed by repeatable, scalable, self-assembling block copolymer organization methods. Various periodic morphologies such as spherical1, lamellar2, and cylindrical3 domains have been experimentally obtained. Self-assembly of block copolymers (BCP) is made possible due to microphase separation of properly selected length blocks. In this work, cylindrical domains are hexagonally ordered by separation of the hydrophobic polystyrene (PS) block and the hydrophilic polyvinylpyridine (PVP) block. Metallic nanoparticle arrays are fabricated via poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) and poly(styrene)-blockpoly(2-vinylpyridine) (PS-b-P2VP) BCPs. The size of iron nanoparticles is controlled by the domain size of the PVP block. By choosing polymers of varied molecular weight, it is possible to control the size of the resulting nanoparticles. In the described methods nanoparticle fabrication can be carried out on conductive substrates as well as non-conductive substrates. Metallic nanoparticle fabrication by BCP techniques also allows a wide range in choice of particles including Au, Ag, Co, Fe, Pt, Pd, and Ni4,5. Nanoparticles deposited by BCPs show good ordering and size distribution. Additionally, BCP patterned metallic nanoparticles have been shown as catalysts for carbon nanotube (CNT) growth6. Chemical vapor deposition (CVD) allows for control of material pro