Thermal reduction of graphene oxide and polyethyleneimine composite membranes with selective ion permeability

Graphene oxide has great potential as filtration membranes because its permeability and selectivity can be controlled through its functional groups. Herein, we studied the morphologies of graphene oxide and polyethyleneimine composite membranes. We demonstrated that polyethyleneimine helps to reduce oxygen-containing functional groups in such composite membranes through Raman, X-ray photoelectron, and Fourier-transform infrared spectroscopies. This indicates that thermally annealed graphene oxide and polyethyleneimine composite membranes tend to remove oxygen functional groups. Furthermore, we investigated the change in permeability due to the reduction in oxygen groups. Consequently, we revealed that the loss of hydroxyl and carboxyl groups impart hydrophobicity to the membranes. Our study is useful for the construction of artificial membranes.