Dear Rashed,

If you have the thickness and mass density, you could directly convert that to molecules/cm2 following the equation S8 (page 10) from the attached supporting information of our paper published recently (Langmuir, 2015, 31 (6), pp 1921–1930). In this case, density of PEG is used and you have to use the density of your material and you need molar mass too. Have a look. It might be what you are looking for.

All the best.

Santanu

Dear Sir,

Thank you so very much.

Sincerely,

Rashed

Dear Rahed,

what you need is the molar mass of your coating. If you have thickness and density you can calculate the mass which gives you mol via the molar mass. Additionally you need the surface area which is covered. This can be calculated by e.g. Langmiur ewuation or Brunauer-Emmet-Taylor-equation (BEM).

Good luck with your sience

Alexander

Using your method, you may obtain an estimate of the coverage but I'm not sure how accurate it will be.  A simple calculation based on your parameters has the implicit assumption that the film is uniform and compact and it may not be.  If possible, you should measure coverage directly.  There are at least 3 cases:

(1) If your film is electrochemically active you can calculate coverage from coulometric experiments by adjusting the surface potential to a value where one electron oxidation (or reduction) of the film occurs and monitoring the current-time profile, with the integrated area ultimately yielding the surface coverage.

(2) If your film contains an element having atomic weight of Cl or larger, Rutherford Backscattering Spectroscopy can give you a direct measure of the coverage in molecules/cm2.  This method works better the higher the molecular weight of elements present.  However, sometimes RBS can erode a film, displacing the element to be measured and leading to a null result.

(3) Hoernschemeyer's equation relating water drop contact angles of a surface film on different substrates can be used in conjunction with absorbance measurements in certain cases to derive molecular surface coverages. We have used it for determining organosiloxane self-assembled monolayer film coverages, see: S.L. Brandow, et. al., Langmuir 2008, 24, 3888-3896.

I don't know if this helps, but in my opinion its always better to measure a property than calculate it when possible.

Dear Dr. Dresssick,

Thank you so very much for your valuable advice. 

I think I can't measure surface coverage in my film with case (1) and (2), because my film is not electrochemically active and contain elements atomic weight less than Cl. However, I could try with case (3), to calculate surface coverage.

Thank you so very much for your valuable suggestions. I can apply those techniques in my future study.

Sincerely,

Rashed

If there is a sheet and made defect in it . then we put one atom above some distance of  defect.. it makes bond with sheet after relaxation n then it also make bond with gas molecule..so in this case can we find SURFACE COVERAGE ??? BY QE using DFT