Stable dispersions of single and multiple graphene layers in solution

A method for producing a graphene layer using a colloidal graphene or multi-graphene layers using a multi-graphene dispersion, the colloidal graphene or the multi-graphene dispersion, respectively, obtained by a first 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) thermally reducing the graphene oxide, or 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 to form a stable colloidal graphene dispersion or a stable multi-graphene dispersion,
• wherein the method for producing the graphene layer using the colloidal graphene or multi-graphene layers using a multi-graphene dispersion, comprises, either the steps of:
• (1) deposit the dispersion of step (ii) on a substrate or precipitate the dispersion of step (ii);
• and
• (2) then perform step (iii);
• or
• (3) deposit the dispersion of step (iii) on a substrate or precipitate the dispersion of step (iii).