Stable dispersions of single and multiple graphene layers in solution
A method for producing colloidal graphene dispersions comprises the steps of: (i) dispersing graphite oxide in a dispersion medium to form a colloidal graphene oxide or multi-graphene oxide dispersion, and (ii) thermally reducing the graphene oxide or multi-graphene oxide in dispersion. Depending on the method used for the preparation of the starting dispersion, a graphene or a multi-graphene dispersion is obtained that can be further processed to multi-graphene with larger inter-planar distances than graphite. Such dispersions and multi-graphenes are, for example, suitable materials in the manufacturing of rechargeable lithium ion batteries.
1. A method for producing stable colloidal graphene dispersions or stable multi-graphene dispersions, the method comprising the steps of:
(i) stirring graphite oxide in an aqueous dispersion medium to form a dispersion;
(ii) determining if the dispersion is optically clear in a light microscope at 1000 fold magnification after 1 to 5 hours of stirring, and, if not clear, removing any undissolved impurities in the dispersion, in order to form a colloidal graphene oxide dispersion, or a multi-graphene oxide dispersion, that is optically clear in a light microscope at 1000 fold magnification; and
(iii) forming a stable colloidal graphene dispersion or a stable multi-graphene dispersion by thermally reducing the graphene oxide, or the multi-graphene oxide, in dispersion in the aqueous dispersion medium at a temperature between 120° C. and 170° C. under pressure in order to ensure that the dispersion medium is not evaporated.
2. The method of claim 1 wherein step (ii) is performed at a temperature between 130° C. and 170° C.
3. The method of claim 1 wherein step (ii) is performed at a temperature between 150° C. and 170° C.
4. The method of claim 1 , wherein the dispersion medium is water, and the dispersion produced in step (i) is a colloidal graphene oxide dispersion and the dispersion produced in step (ii) is a colloidal graphene dispersion.
5. The method of claim 1 , wherein the dispersion medium further comprises ammonia.
6. The method of claim 1 , wherein step (ii) is performed at a temperature and for a time to result in a colloidal graphene dispersion with a carbon:oxygen (C/O) ratio of between about 4 and about 25.
7. The method of claim 1 , wherein the dispersion medium is acidified water, having a pH of about 4, and the dispersion produced in step (i) is a multi-graphene oxide dispersion and the dispersion produced in step (ii) is a multi-graphene dispersion.
8. The method of claim 1 , wherein step (ii) is performed at a temperature and for a time to result in a colloidal graphene dispersion with a carbon:oxygen (C/O) ratio of between about 4 and about 20.
9. The method of claim 1 , wherein step (ii) is performed at a temperature and for a time to result in a colloidal graphene dispersion with a carbon:oxygen (C/O) ratio of between about 4 and about 13.5.
10. The method of claim 1 , wherein step (ii) is performed at a temperature and for a time to result in a colloidal graphene dispersion with a carbon:oxygen (C/O) ratio of about 7.
11. The method of claim 1 , wherein the aqueous dispersion medium consists essentially of water.
12. The method of claim 11 , wherein the aqueous dispersion medium further includes ammonia.
13. The method of claim 11 , wherein the aqueous dispersion medium further includes an acid.
14. A method for producing stable colloidal graphene dispersions or stable multi-graphene dispersions, the method comprising the steps of:
(i) dispersing graphite oxide in an aqueous dispersion medium to form a colloidal graphene oxide dispersion, or to form a multi-graphene oxide dispersion, that is optically clear in a light microscope at 1000 fold magnification;
(ii) forming a stable colloidal graphene dispersion or a stable multi-graphene dispersion by thermally reducing the graphene oxide, or the multi-graphene oxide, in dispersion in the aqueous dispersion medium at a temperature between 120° C. and 130° C. under pressure in order to ensure that the dispersion medium is not evaporated.
15. A method for producing stable colloidal graphene dispersions or stable multi-graphene dispersions, the method comprising the steps of:
(i) stirring not intercalated graphite oxide in an aqueous dispersion medium to form a dispersion;
(ii) determining if the dispersion is optically clear in a light microscope at 1000 fold magnification after 1 to 5 hours of stirring, and, if not clear, removing any undissolved impurities in the dispersion, in order to form a colloidal graphene oxide dispersion, or a multi-graphene oxide dispersion, that is optically clear in a light microscope at 1000 fold magnification; and
(iii) forming a stable colloidal graphene dispersion or a stable multi-graphene dispersion by thermally reducing the graphene oxide, or the multi-graphene oxide, in dispersion in the aqueous dispersion medium at a temperature between 120° C. and 170° C. under pressure in order to ensure that the dispersion medium is not evaporated.
16. The method of claim 15 , wherein step (ii) is performed at a temperature of 120° C. to 130° C.
17. The method of claim 15 , wherein step (ii) is performed at a temperature between 130° C. and 170° C.
18. The method of claim 15 , wherein step (ii) is performed at a temperature between 150° C. and 170° C.
19. The method of claim 15 , wherein the dispersion medium is water, and the dispersion produced in step (i) is a colloidal graphene oxide dispersion and the dispersion produced in step (ii) is a colloidal graphene dispersion.
20. The method of claim 15 , wherein the dispersion medium further comprises ammonia.
21. The method of claim 15 , wherein step (ii) is performed at a temperature and for a time to result in a colloidal graphene dispersion with a carbon:oxygen (C/O) ratio of between about 4 and about 25.
22. The method of claim 15 , wherein the dispersion medium is acidified water, having a pH of about 4, and the dispersion produced in step (i) is a multi-graphene oxide dispersion and the dispersion produced in step (ii) is a multi-graphene dispersion.
23. The method of claim 15 , wherein step (ii) is performed at a temperature and for a time to result in a colloidal graphene dispersion with a carbon:oxygen (C/O) ratio of between about 4 and about 20.
24. The method of claim 15 , wherein step (ii) is performed at a temperature and for a time to result in a colloidal graphene dispersion with a carbon:oxygen (C/O) ratio of between about 4 and about 13.5.
25. The method of claim 15 , wherein the aqueous dispersion medium consists essentially of water.
26. The method of claim 25 , wherein the aqueous dispersion medium further includes ammonia.
27. The method of claim 25 , wherein the aqueous dispersion medium further includes an acid.