Hi,

I think you are talking about graphene, HR-TEM is the best way to find a layer thickness (from d space) or number of layers.  

1. Use TEM to estimate the NS dimensions

2. Estimate/find the density of the material to give you mass per nanosheet.

3. Provided that the solution is pure (only nanosheets and water), dry a known volume of the dispersion extensively and weight.

4. Divide the total mass by the mass of a single nanosheet.

NB. If there is a organic capping agent, you will need to use TGA to estimate the mass fraction of this component.

Thanks a lot @ Dr. Adam Perriman