Low-Temperature Solid-State Microwave Reduction of Graphene Oxide for Transparent Electrically Conductive Coatings on Flexible Polydimethylsiloxane (PDMS)

Microwaves (MWs) are applied to initialize deoxygenation of graphene oxide (GO) in the solid state and at low temperatures (similar to 165 degrees C). The Fourier-transform infrared (FTIR) spectra of MW-reduced graphene oxide (rGO) show a significantly reduced concentration of oxygen-containing functional groups, such as carboxyl, hydroxyl and carbonyl. X-ray photoelectron spectra confirm that microwaves can promote deoxygenation of GO at relatively low temperatures. Raman spectra and TGA measurements indicate that the defect level of GO significantly decreases during the isothermal solid-state MW-reduction process at low temperatures, corresponding to an efficient recovery of the fine graphene lattice structure. Based on both deoxygenation and defect-level reduction, the resurgence of interconnected graphene-like domains contributes to a low sheet resistance (similar to 7.9x10(4) Omega per square) of the MW-reduced GO on SiO2-coated Si substrates with an optical transparency of 92.7% at similar to 547 nm after MW reduction, indicating the ultrahigh efficiency of MW in GO reduction. Moreover, the low-temperature solid-state MW reduction is also applied in preparing flexible transparent conductive coatings on polydimethylsiloxane (PDMS) substrates. UV/Vis measurements indicate that the transparency of the thus-prepared MW-reduced GO coatings on PDMS substrates ranges from 34 to 96%. Correspondingly, the sheet resistance of the coating ranges from 10(5) to 10(9) Omega per square, indicating that MW reduction of GO is promising for the convenient low-temperature preparation of transparent conductors on flexible polymeric substrates.