▎ 摘　　要

Formulation of stable aqueous graphene solution is attempted either through esterification of GO with PEG and subsequent reduction in covalent approach or in situ chemical reduction of aqueous GO solution in the presence of NF(2)-PEG-NH(2) in noncovalent approach. While covalent approach produces insoluble graphite-like precipitation, noncovalent approach produces practically homogeneous reduced graphene solution for several months without any precipitate. Noncovalent interaction between NH(2)-PEG-NH(2) and graphene is crucial for formulating fully reduced graphene solution with high stability. Various wet process such as spin-coating, ink-jet printing, and spraying can be directly utilized to formulate graphene-based electronic devices such as transparent electrode or anti-static coating without any additional reduction process which is necessary when insulating GO solution is used instead. Non-conducting NH(2)-PEG-NH(2) can be simply removed from conducting graphene film by simple filtration and washing process to formulate pure graphene film because interaction between graphene and NH(2)-PEG-NH(2) is not covalent. The initial surface resistance of graphene thin film with NH(2)-PEG-NH(2) is in the range of 10(6) Omega/square but it decreases to 10(4) Omega/square after removing NH(2)-PEG-NH(2). (C) 2011 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.