AVS 58th Annual International Symposium and Exhibition
    Nanometer-scale Science and Technology Division Wednesday Sessions
       Session NS-WeM

Paper NS-WeM9
Solution Plasma-Assisted Surface Functionalization of Chemically Converted Graphene Sheet toward an Enhancement of Solubility in Solution

Wednesday, November 2, 2011, 10:40 am, Room 203

Session: Carbon-Based Nanomaterials
Presenter: Noriaki Tsuda, Nagoya University, Japan
Authors: N. Tsuda, Nagoya University, Japan
T. Ueno, Nagoya University, Japan
N. Zettsu, Nagoya University, Japan
S. Cho, Nagoya University, Japan
O. Takai, Nagoya University, Japan
N. Saito, Nagoya University, Japan
Correspondent: Click to Email
Graphene, a one-atom layer of graphite, possesses a unique two-dimensional structure and excellent mechanical, thermal, and electrical properties. Thus, it has been regarded as an important component for making various functional composite materials. Graphene can be prepared through micromechanical exfoliation, epitaxial growth, and chemical vapor deposition and electrochemical approaches. Different from these approaches, chemical synthesis of graphene using graphite, graphite oxide (GO) or other graphite derivatives as starting materials were tested to be effective for producing chemically converted graphene (CCG) from various precursors, such as graphite, carbon nanotubes, and polymers, in large scale and at low costs. Therefore, CCG is more suitable for synthesizing high-performance graphene based composites.

Graphene oxide can be chemically reduced to CCG. Hydrazine monohydrate was most widely used, mainly due to its strong reduction activity and the stability in aqueous media. Upon reduction with hydrazine, most oxygen-containing functional groups of graphene oxide are eliminated and the π-electron conjugation within the aromatic system of graphite is partially restored. As a result, the reduced graphene oxide (or CCG) is usually precipitated from the reaction medium because of the recovered graphite domains of CCG sheets increased their hydrophobic property and π-stacking interaction. The use of hydrazine as reducing agent also has several disadvantages. The trace residual may strongly decrease the performance of CCG in devices.

In this work, we demonstrate solution plasma-assisted surface functionalization of chemically converted graphene sheet in order to enhancement of solubility in both aqueous and organic solvent. Solution plasma (SPP) is a plasma discharge in solution, which is expected a higher reaction rate under low-temperature conditions, and the greater chemical reaction variability since the molecular density of liquid is much higher than that of gas phase.

A colloidal grapheme oxide sheets was treated with SP in ammonium containing aqueous solution in order to make reduced CCG and functionalize CCG surface with primary amine group.. A glow discharge was produced at bipolar-pulsed voltages with pulse width and frequency of 2 ms and 15 kHz, respectively. The all products were characterized by IR, Raman, spectroscopy, AFM, XRD, and TEM. Furthermore, we also demonstrate an introduction of organic and polymeric molecule as a second component onto the aminated CCG surface to insulate hydrophobic property and π-stacking interaction of neighboring CCG sheets in aqueous solution, and to be organic solvent solubilization.