For example, if IR-detectable concentration of calcium carbonate molecules is present in smectite powder after it had been exposed to high pressure CO2, how can one tell with confidence whether they are primarily sandwiched between the internal surfaces (in interlayer) or situated near the edges, external surfaces? If some of you believe that your group has such a capability and would like to reproduce the initial steps, I would be happy to discuss the experimental conditions and procedures. If anyone believes that there are no such capabilities currently available anywhere, I would appreciate if you could share your wild ideas of what kind of instrumentation or setup should be built to accomplish it.
Yes, XRD allows us to "see the difference" but it does not tell us what it is due to. For example, volumetric displacement of the interlayer H2O with CO2 does not affect the basal distance for all practical purposes. However, in that case we would be able to tell the difference between the interlayer and external species using IR fingerprints. Unfortunately, that is not true for broader peaks like carbonates. We did try various combinations of XRD, XPS, and IR.
Ken, if you will be interested, once you get a chance, you are welcome to check our group's publications. I believe the references below may clarify it, but speaking of the peak widths, I was referring to the IR characteristic vibrational frequencies.
V.N. Romanov "Evidence of irreversible CO2 intercalation in montmorillonite," Int. J. Greenhouse Gas Control 2013, 14, 220-226;
T.-B. Hur, J.P. Baltrus, B.H. Howard, W.P. Harbert, V.N. Romanov "Carbonate formation in Wyoming montmorillonite under high pressure carbon dioxide," Int. J. Greenhouse Gas Control 2013, 13, 149-155.
More can be found in my RG list of publications and uploads, if needed.-Slava
May I suggest the AFM if you dont want to identify the molecular species on the surfaces of interlayers of clay.
Thanks İlker,
I had explored AFM assisted chemical imaging awhile ago (see my thesis, "Unified Microscopy and Spectroscopy for Nanoscale Chemical Imaging") and it proved to be difficult to detect anything with spatial resolution
Methods for atom-sensitive imaging of small particles include atom probe tomography (APT) and synchrotron X-ray nanotomography. APT has atomic resolution, while X-ray nanotomography is currently limited to tens of nm. However, if a high enough X-ray beam energy may be used, X-ray nanotomography can be performed in situ (i.e. while heating/cooling under a controlled gas environment) I'm aware of APT capabilities at Pacific Northwest National Laboratory (PNNL) and Northwestern University, and atom-sensitive X-ray nanotomography at the Stanford Synchrotron Radiation Lightsource (SSRL). The attached/linked publications may be of interest.
http://www.nature.com/ncomms/2015/150702/ncomms8589/full/ncomms8589.html
Article Mapping Metals Incorporation of a Whole Single Catalyst Part...
Of course it seems to be interesting to have a image of intercalated particle in the clay layer. Yet no one have reported the same using any of the said tools. But I do have interest on the subject as a worker on pillared clay. We are only using XRD for indirect proof.
