title: Fabrication of graphene thin films based on layer-by-layer self-assembly of functionalized graphene nanosheets.
abstract: In this study, we present a facile means of fabricating graphene thin films via layer-by-layer (LbL) assembly of charged graphene nanosheets (GS) based on electrostatic interactions. To this end, graphite oxide (GO) obtained from graphite powder using Hummers method is chemically reduced to carboxylic acid-functionalized GS and amine-functionalized GS to perform an alternate LbL deposition between oppositely charged GSs. Specifically, for successful preparation of positively charged GS, GOs are treated with an intermediate acyl-chlorination reaction by thionyl chloride and a subsequent amidation reaction in pyridine, whereby a stable GO dispersibility can be maintained within the polar reaction solvent. As a result, without the aid of additional hybridization with charged nanomaterials or polyelectrolytes, the oppositely charged graphene nanosheets can be electrostatically assembled to form graphene thin films in an aqueous environment, while obtaining controllability over film thickness and transparency. Finally, the electrical property of the assembled graphene thin films can be enhanced through a thermal treatment process. Notably, the introduction of chloride functions during the acyl-chlorination reaction provides the p-doping effect for the assembled graphene thin films, yielding a sheet resistance of 1.4 kΩ/sq with a light transmittance of 80% after thermal treatment. Since the proposed method allows for large-scale production as well as elaborate manipulation of the physical properties of the graphene thin films, it can be potentially utilized in various applications, such as transparent electrodes, flexible displays and highly sensitive biosensors.
authors.affiliation: SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors.forename: Je Seob
authors.initials: JS
authors.lastname: Park
authors.forename: Sung Min
authors.initials: SM
authors.lastname: Cho
authors.forename: Woo-Jae
authors.initials: WJ
authors.lastname: Kim
authors.forename: Juhyun
authors.initials: J
authors.lastname: Park
authors.forename: Pil J
authors.initials: PJ
authors.lastname: Yoo
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry; D004566:Electrodes; D006108:Graphite / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010087:Oxides / Q000737:chemistry; D055672:Static Electricity; D013461:Sulfur Oxides / Q000737:chemistry
chemical_list: D002264:Carboxylic Acids; D010087:Oxides; D013461:Sulfur Oxides; C023589:thionyl chloride; D006108:Graphite