Flexible and conductive graphene-poly (diallyldimethylammoniumchloride) buckypaper

This paper describes the fabrication and characterization of flexible, conductive reduced graphene oxide (rGO)-poly(diallyldimethylammoniumchloride) (PDDA) buckypaper (BP). PDDA acts as a reducing agent to prepare an rGO-PDDA nanosheet dispersion from graphite oxide. The incorporation of PDDA as a "glue" molecule successfully binds rGO nanosheets into BPs with strong interlayer binding. The resulting BPs were characterized by scanning electronic microscopy (SEM), Raman, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and resistivity measurements. The sp² structure was greatly restored by the PDDA-induced reduction. Moreover, rGO was chemically doped from the adsorbed PDDA, which causes the Raman G band to shift from ∼1585 to ∼1610 cm^-1. This chemical doping substantially increased the density of the free charge carriers in rGO and thereby further enhanced the electrical conductivity of the rGO-BP. Good interlayer connection in the rGO percolating network was obtained after thermal annealing at higher than ∼250 °C. The resulting rGO-PDDA-BPs exhibited an isotropic sheet resistance as low as ∼100 ω;/sq, which indicates a reduction by six orders of magnitude compared to the GO-BPs resistance before annealing. This PDDA-induced reduction with a low-temperature annealing process preserved the BPs' structural integrity and mechanical flexibility, thus overcoming the fragility problems with high-temperature annealing.