Adsorption phenomena of tetracyano-p-quinodimethane on single-wall carbon nanohorns

We studied the interaction of tetracyano-p-quinodimethane (TCNQ) with single-wall carbon nanohorns (SWNHs), single graphene-tubes with large diameters (2-5 nm), and noticed two interesting phenomena. One is that adsorbed quantities on the inside (0.08 g/g) and outside (0.13 g/g) of SWNH corresponded-to about 20% and 60% of respective monolayer coverage, which did not increase even when the TCNQ was overdosed. The second is that Raman spectra suggested that the quinoid rings of TCNQ developed benzene-like character. The electron microscopy with electronic state analysis indicated that the charge transfers from SWNH to TCNQ. The theoretical calculations suggested that TCNQ was bended on the curved graphene of SWNHs, which mostly explained the unique characteristics of TCNQ adsorbed on SWNHs.