A research team from Skoltech, MIPT, Emanuel Institute of Biochemical Physics of Russian Academy of
Sciences, and other scientific organizations recently conducted a study to determine which conditions are the most suitable for storing graphene oxide.
The results showed that the most optimal conditions for graphene oxide, when its properties will not change, are low temperatures and a lack of light.
“The structure of graphene oxide manufactured chemically is very difficult to reproduce — it will always be different. And after a while, it begins to degrade, and the properties of the oxide itself change. If, after
manufacturing, the material is sent to another place — another institute or country, it will come in a
completely different state. And even when the test tubes are just there in the laboratory, the properties of
the material also change. We decided to conduct a comprehensive study of the best conditions to store
samples in,” said Dmitry Kvashnin, a study co-author, Doctor of Science in Physics and Mathematics,
docent, Leading Research Scientist at the Emanuel Institute of Biochemical Physics of Russian Academy of
Sciences.
The team produced several samples of graphene oxide, identical in the chemical composition and
production method, and placed them in different conditions: at room temperature and in the fridge, as
well as in the light and without it.
“For 150 days, we observed changes in the properties of the samples: We looked at how the absorption
spectra, X-ray photoelectron radiation spectra, hydrogen index, and viscosity of suspensions change. The
comprehensive analysis of these characteristics allowed us to expand our understanding of the processes
occurring on the surface of graphene oxide, leading to structural changes. We found out that graphene
oxide is best stored in the cold and without exposure to light. In this case, there is no reduction, that is,
oxygen-containing groups are not removed from the surface of graphene oxide, and it doesn’t turn back
into graphene. And at room temperature and in the light, it recovers faster. We can observe that even by
the changing color of the solution — it goes darker,” said the first author of the study, Julia Bondareva, a
research scientist at the Materials Center of Skoltech.
“To find out what changes can occur in the structure of graphene oxide and why it precipitates over time,
we used supercomputer atomistic modeling. Using quantum chemical calculations, we showed that in their
most stable state, oxygen groups on the surface of graphene oxide tend to cluster. This differs from the
bulk of the models used in the literature, which assume an even random distribution of oxygen. The
clustering of oxygen groups that we showed, on the one hand, should lead to a change in optical spectra,
and on the other, to the formation of pure graphene regions in those areas where oxygen ‘migrated’ from.
Since graphene is an extremely hydrophobic material, such areas will tend to stick together to minimize
contact with water. This is exactly what leads to precipitation observed in the experiment. Read more
about other collaborative research in the joint Telegram channel of the laboratories,” explained Nikita
Orekhov, a co-author of the work, Deputy Head at the Laboratory of Computer Design of Materials at
MIPT, PhD in Physics and Mathematics.
The results show that special attention should be paid to the storage conditions of materials and to their
properties at each stage of synthesis, the authors noted.