Figure 6.

Digital images of solutions of: (a and b) as-prepared graphene oxide (0.1 mg mL⁻¹) in different media, (c and d) doubly oxidized graphene oxide (0.1 mg mL⁻¹) in different media, and (e and f) as-prepared graphene oxide (0.1 mg mL⁻¹) in the presence of Pluronic F127 (1.0 mM) and different media. To accentuate contrast, the images in the right column are grayscale reproductions of those on the left. Images were recorded 5 min after the graphene oxide formulations were combined with the different media: (1) ultrapure deionized water, (2) 1× PBS, (3) 10% FBS in MEM cell culture medium, and (4) Pure FBS. Samples were briefly centrifuged (~30 sec) to accentuate the extent of aggregation of the nanosheet into powders at the bottom of the tube, if any.