On the production, mechanical and electro-optic properties of large-area monolayer graphene films using Langmuir-Blodgett technique

We managed to produce truly transparent conductive monolayer graphene films using commercially available graphene nano-flakes by utilizing the Langmuir-Blodgett technique. The monolayer films could only be produced under specific solution concentration, sonication time, and evaporation conditions. The described method eliminates the need for intermediate processing steps, such as adding surfactant or annealing during the process. Film structure is characterized using scanning tunneling microscopy and high-resolution electron transmission microscopy. Mechanical characterization shows that the film exhibits a nonlinear stress-strain curve with a strain stiffening behavior in agreement with previous theoretical predictions. Film stiffness ranges between 40 and 80 MPa. The produced monolayer graphene films exhibit full transparency in the wavelength range of 400 nm to 1100 nm, and an excellent electrical conductivity ∼104 S cm-1 which is comparable to the transferred films produced by CVD, and comparable to that of ITO coating. These films have great potential applications in many different fields including transparent electrodes, sensor, optoelectronic devices and photovoltaics.