This indicated that the quinoid ring of the TCNQ molecules transformed to a benzene ring after CT, as in the case of adsorbed TCNQ on single-wall carbon nanohorns [32]. Meanwhile, the C ≡ N stretching vibration shifted up to 2,210 cm-1 in the RGO + TCNQ complex sample. The degree of charge transfer, Z, was estimated at 0.39 from the C ≡ N vibration Alvocidib manufacturer frequency, which should be

a linear function of Z[33]. Moreover, we also examined doping effect from surface adsorption by immersing pristine RGO films in a TCNQ dispersion for comparison [34]. The sheet resistance was also improved because the surface electrons of the RGO film were withdrawn by adsorbed TCNQ molecules, as represented in Figure 3a. The Z value (degree of CT) was estimated at 0.27 from the C ≡ N vibration frequency in the Raman spectra. Doping effects from the surface adsorption were limited by the amount of adsorbed molecules, due to the strong intermolecular repulsive interaction [35, 36]. On the other INCB018424 supplier hand, our RGO + TCNQ complex films, which are shown as a schematic image in Figure 3b, were improved in terms of sheet resistance from those in previous reports [19, 21, 26]. It is expected that the notable doping effect was S3I-201 ic50 principally achieved by the strong mutual reaction between radicalized TCNQ

molecules and RGO flakes in the liquid phase, as predicted from the absorbance spectra. Furthermore, the TCNQ-RGO interaction might accelerate and improve the stacking of films during film fabrication [35, 37]. We presumed that these phenomena

supported the existence of a high doping effect and a high degree of charge transfer (Z = 0.39). Figure 2 Raman spectra of fabricated films. From RGO + TCNQ complex film (red line), RGO film (black line) and TCNQ single crystal (blue line) with an image of TCNQ molecular structure. The Raman spectrum of the RGO + TCNQ complex consists of peaks from TCNQ and RGO (and other unknown peaks). The shifts in the Raman peaks from the TCNQ in RGO + TCNQ complex indicates a charge transfer interaction. Figure 3 Schematic images of doped RGO films by surface adsorption (a) and RGO + TCNQ complex films (b). Additional evidence for the CT interaction was obtained via UPS using He1 radiation (hν = 21.2 eV). Celastrol We measured the UPS spectra of doped and non-doped RGO films under an applied sample bias voltage of -9 eV. The work function (Φ) increased by 0.4 eV from pristine RGO films relative to the RGO + TCNQ films as shown in Figure 4. The change in the surface work function (ΔΦ) might be mainly caused by the Fermi level (E F ) shifting towards the Dirac point (E D ) due to hole doping from TCNQ via CT, and the interface dipole effect for the TCNQ + RGO films might be smaller than that induced at a deposited F4-TCNQ/graphene interface [34, 38]. Figure 4 Secondary electron cut-off region UPS spectra of doped and non-doped RGO films.