Finally, the solvent of reduced graphene oxide (RGO) dispersion was replaced by N,N-dimethylformamide (DMF) using an evaporator. RGO can be dispersed well in many kinds of organic solvents including DMF, while it is easily aggregated in aqueous solution because of its low electrostatic repulsion force. Doping and film fabrication Doping graphene via charge transfer by TCNQ molecules was carried out as follows. First, 0.01 g of TCNQ powder (>98.0%, Tokyo Chemical Industry Co. Ltd., Tokyo, Japan) was dissolved into 5 ml of DMF solvent. Then, 5 ml of RGO dispersion and radicalized TCNQ in DMF were mixed and stirred for 1 week at room temperature.

The color of mixture solution changed from yellow-green GSK1120212 manufacturer to orange. Our graphene films were deposited on glass substrates (Corning7059) by a spray coat method at a substrate temperature of 200°C in an atmosphere containing the solvent vapor. The thickness of the films was controlled by varying the spray amounts. Characterization The Raman spectroscopy was measured with a Jasco NRS-1000 (excited by a 532-nm green laser; Easton, MD, USA). Absorbance and transmittance spectra were obtained with Shimadzu SolidSpec3700 Selinexor UV–vis by using a quartz cell for absorbance measurements. The sheet resistance was measured by

van der Pauw method at room temperature in air. The presence of monolayered GO flakes in our synthesized GO aqueous solution was verified by atomic force microscope images by Raman peak shifts and by the peak shape of the second-order two-phonons process peak at 2,700 cm-1, referred to as the 2D band. The size of the flakes is up to 50 × 50 μm2. After liquid phase reduction by N2H4 and NH3, the solvent of the RGO aqueous solution was replaced by DMF using an evaporator. RGO can be dispersed well in many kinds of organic solvents including DMF, while it is easy to aggregate in aqueous solution due to its low electrostatic repulsion force. The

conductivity and the Hall carrier mobility of individual monolayered RGO flakes were as high as 308 S · cm-1 and 121 cm2 · V-1 · s-1, respectively. Hall measurements were conducted in air at room temperature using Hall-cross geometry and Protein kinase N1 Au/Ti electrodes. Calculation details The electronic structural analysis is carried out using the SIESTA3.1 code, which performs fully self-consistent calculations solving the Kohn-Sham equations [28]. The Kohn-Sham orbitals are expanded using linear combinations of pseudo-atomics orbitals. The double-zeta polarized (DZP) basis set was chosen in this study. The calculations were done with the local density approximation (LDA), using the Ceperley-Alder correlation as parameterized by Perdew and Zunger [29]. The electron-ion interaction was treated by using norm-conserving, fully separable pseudo-potentials [30]. A cutoff of 200 Ry for the grid integration was utilized to represent the charge density.