[Ifeffit] particle size and coordination number in Ru nanoparticles on carbon
Wayne W Lukens Jr
wwlukens at lbl.gov
Tue Sep 20 13:25:38 CDT 2011
There is a very nice paper by Scott Calvin that describes this in some
J. Appl. Phys. 94:778–83 (2003)
On Tue, Sep 20, 2011 at 11:04 AM, Scott Calvin <scalvin at sarahlawrence.edu>wrote:
> Hi Marian,
> My big tip is to look at the second nearest-neighbor CN as well, and even
> further out if you can get it. It's sometimes hard to pin down the
> near-neighbor coordination number because of issues like the one you
> describe. But the ratio of higher CNs to near-neighbor CN is quite
> diagnostic of small nanoparticles. (Actually, for reasons too lengthy to get
> in to at the moment, this method does tend to produce results a bit biased
> to the small side, so it's best to try the identical fitting model on a bulk
> standard for comparison.)
> --Scott Calvin
> Sarah Lawrence College
> On Sep 20, 2011, at 1:50 PM, Dreher Marian wrote:
> Dear Ifeffit Community,
> I am currently trying to extract the particle size of Ru supported on
> carbon from EXAFS data. I also recorded spectra of a Ru foil as a bulk
> reference sample.
> So, my approach is to fit the first coordination shell of my bulk
> reference, setting CN to 12. From that I get a value for s02. I'm then using
> this value in the first shell fit for the Ru nanoparticles in order to get
> the coordination number.
> However, the fit suggests that CN is still pretty much 12. What is changing
> drastically, though, is sigma^2 which usually doubles in value compared to
> the bulk sample. That makes sense, I guess, since there might be higher
> disorder in the nanoparticles.
> Obviously, there is a chance that my nanoparticles are rather big, in which
> case CN would be close to 12. However, STEM and HRTEM pictures suggest that
> the Ru particles are between 1 and 2 nm in diameter.
> I'm just starting to get into EXAFS analysis and pretty clueless right now
> about how to approach this.
> Happy about any input,
> many thanks,
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
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