Fig. 3: Reduced time course of the peak position of the π-π^* transition of GO colloids ripened at different temperatures for various durations.

The horizontal axis is the logarithm of the reduced time (t_red). The reduced time course consists of three regions attributed to intrinsic GO (iGO), metastable GO (mGO) and transient GO (tGO). Brown and gray zones represent the transition regions. Photographs of the GO colloids are shown on top of the graph; the arrows indicate the corresponding reduced time. A photo of commercial GO is shown on the right side, and the peak position of its \(\pi -{\pi }^{*}\) transition is indicated by an arrow and a dashed line. Ripening temperature: black circles, 298 K; green squares, 308 K; blue diamonds, 333 K; red triangles, 348 K. Open circle represents a peak position of the non-ripened GO colloid. Error bars represent the reproducibility in the peak position determination of at least three measurements.