Orientation of 4-n-octyl-4′-cyanobiphenyl molecules on graphene oxide surface via electron–phonon interaction and its applications in nonlinear electronics†
We investigate the graphene oxide (GO) dispersed 4-n-octyl-4′-cyanobiphenyl (8CB) hybrid system in order to reveal the long range molecular interactions. Polarized optical microscopy reveals the vertical orientation of 8CB molecules on the GO surface. The bulk orientation of the 8CB molecules significantly depends upon the concentration of GO. The mechanism of the so obtained vertical orientation was further investigated by using Raman and Fourier transformed infrared spectroscopy. We have found that the electron–phonon interaction, between the cyano (CN) functional group of 4-n-octyl-4′-cyanobiphenyl and phonons of GO, is responsible for the vertical orientation of the 8CB molecules over the GO surface. The roles of the CN functional group, orientational order parameter and defect intensities have been quantitatively analyzed to support the observations. We have also explored the possibility of integrating the nonlinear electronic applications of the hybrid system by studying the current–voltage (I–V) characteristics. The I–V curves of the hybrid system have shown the 103 order higher current in comparison to pristine 8CB material which is due to the combined effect of enhanced charge carrier mobility and the formation of GO networking.