Particle size and concentration are key to that. Logically if they were present in low concentration they would have little effect on the color, especially if small.
...in low concentration they would have little effect on the color, especially if small....
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From various readings, the graphene oxide nano-particles are described as optically transparent. They are also inert in vitro and become *active* (still unclear on what that means, but I think it refers to a self-organizing faculty)in serum (sic). Does that mean blood? Interstitial fluid? The injections also contain disclosed ‘bovine calf serum’.