Transparent and conductive films from liquid phase exfoliated graphene

We describe transparent and conductive films of liquid-phase exfoliated graphene deposited with the Langmuir–Blodgett (LB) method. Graphene sheets (GS) were exfoliated from graphite by ultrasonic treatment in N-Methyl-2-pyrrolidone (NMP) and N, N-dimethylacetamide (DMA) solvents. For comparison, graphene sheets were also exfoliated in a water solution of surfactants. We confirm a higher exfoliation rate for surfactant-based processing compared to NMP and DMA. Furthermore, we demonstrate that our films exfoliated in NMP and DMA, deposited with LB and annealed have a higher optical transmittance and lower sheet resistance compared to films obtained with vacuum filtration, which is a necessary step for GS exfoliated in water solutions. The structural, optical and electrical properties of graphene layers were characterized with scanning electron microscopy, atomic force microscopy, UV/VIS spectrophotometry and sheet resistance measurements. Our facile and reproducible method results in high-quality transparent conductive films with potential applications in flexible and printed electronics and coating technology.