Optical Annealing of Graphene Oxide Thin Films*

Graphene oxide (GO) can be converted to highly conductive reduced GO (rGO) via photochemical methods, solution chemistry, and high-temperature treatments. Specifically, highly localized, controllable laser-based annealing has been shown to create conductive patterns of rGO. This optically induced thermal transition is characterized by the ratio of sp²-to-sp³-hybridized carbon (using Raman spectroscopy) and electrical conductivity. Here, we show that circuit-like patterns of rGO can be created using a 532 nm laser at intensities of ~6 MW/cm². Using the integrated ratio of the GO sp² G-band (~1594 cm^-1) to sp³ D-band (~1363 cm^-1), we show that the optically generated GO-to-rGO conversion is slower and more uniform in an argon environment than in vacuum, an observation we attribute to the greater thermal exchange created by the high heat capacity argon gas. We determine the GO-to-rGO transition temperature of our optical process using the ratio of the integrated Stokes to anti-Stokes peaks and find that this temperature is consistent with standard induction furnace rGO annealing. Our findings suggest that optically created circuits of conductive rGO can be reproducibly created from GO films.