One thing I found interesting about that article is that it mentioned that the carbon nanoparticles increase absorption of wavelengths in the green, ultraviolet, and near-infrared wavelengths. This gave me the idea that it would change the color of the plants since less green light would be reflected.
And this reminded about how different photosynthetic microbes in microbial consortia have different colors in order to make use of different wavelengths of light that penetrate to different depths within a biofilm.
So I thought, maybe a similar effect could be produced by bioengineering plants with a variety of different photosynthetic pigments in order to absorb a wider range of wavelengths of light.
I'm not sure about the environmental consequences of carbon nanoparticles, but this would bypass any of the possible consequences of the nanoparticles. Then the problem becomes the ecological impact of such bioengoneered plants.
I'm sure that an infertile plant completely dependent on human cultivation could be developed, but I'm always wary of fiddling with natural system in this way since natural selection could always throw in a monkey wrench and lead to the collapse of the world's ecosystems as we know them in this case.
Maay-yo-naze!