September 2011 - Ifeffit - millenia.cars.aps.anl.gov

particle size and coordination number in Ru nanoparticles on carbon
by Dreher Marian 11 Oct '11

11 Oct '11

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, Marian.

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Fit with Artemis in Demeter
by Kleper Rocha 30 Sep '11

30 Sep '11

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Preparation help with fly ash sample with diluted Tl
by Mengling Yi Stuckman 30 Sep '11

30 Sep '11

Dear Ifeffit Community, I am currently working on project "Evaluating Speciation of Thallium in Coal Fly Ash". The project was accepted by APS and we will conduct our measurement on beamline 5-BM-D. My fly ash sample has Tl concentration ranging from 0.5ppm to 13ppm. How can I know whether the sample can generate enough photon counts if using fluorescence mode? what would be the appropriate sample preparation procedure I should follow? Is there any interference I should pay attention to? I understand that I should use Hephaestus, but I don't know how to do that if my sample contains lots of different oxides. I attached the elemental composition in this email. Most metals should be in form of oxides, or sulfates. Any input would be highly appreciated, Mengling

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Re: [Ifeffit] Preparation help with fly ash sample with
by fred.mosselmans＠diamond.ac.uk 30 Sep '11

30 Sep '11

Dear Mengling, As Caroline Peacock from Leeds has successfully done Tl L3 microXAFS on some samples on I18 at diamond, I Have a little experience. She has a paper on the work currently in review. As Matt says if you have Pb in the sample your data is limited to just under 350 eV (10 k). Micro EXAFS past 10 k is quite hard but feasible and the big advantage is your localised concs. are possibly (probably?) a lot higher than for the bulk. If the Tl was equally distributed at 13 ppm max then micro Xanes might work, XAFS wont - but i think that's not likely. Thus with a local high concentration you might with time get 12 k XAFS from the Tl. As for using a total yield detector the big advantage is that they are count rate unlimited so you don't have to worry about count rate saturating your detector and can have it dead close to the sample to get the maximum Tl counts. Even with Al attenuation which will remove the Fe signal quicker than the Tl you are throwing away some Tl counts. Hence for XANES in particular it may be advantageous. Cheers Fred Prof. J F W Mosselmans Principal Beamline Scientist I18 Diamond Light Source Diamond House Harwell Campus Didcot Oxon OX11 ODE UK T 00 44 1235 778568 M 00 44 7785510211 E fred.mosselmans(a)diamond.ac.uk F 00 44 1235 778448 Never mind the W it's the tax that counts -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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Fly ash sample with diluted Tl
by Mengling Yi Stuckman 29 Sep '11

29 Sep '11

Dear Ifeffit Community, I am currently working on project "Evaluating Speciation of Thallium in Coal Fly Ash". The project was accepted by APS and we will conduct our measurement on beamline 5-BM-D. My fly ash sample has Tl concentration ranging from 0.5ppm to 13ppm. How can I know whether the sample can generate enough photon counts if using fluorescence mode? what would be the appropriate sample preparation procedure I should follow? Is there any interference I should pay attention to? I understand that I should use Hephaestus, but I don't know how to do that if my sample contains lots of different oxides. I attached the elemental composition in this email. Most metals should be in form of oxides, or sulfates. Any input would be highly appreciated, Mengling -- Mengling Yi Stuckman Graduate Research Assistant Civil and Environmental Engineering and Geodetic Science Ohio State University 2070 Neil Ave., Columbus, OH, 43210

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Artemis fitting k-weight
by George Sterbinsky 20 Sep '11

20 Sep '11

Hello, When fitting data in Artemis with the "other k weight" box checked and the kw = 1, 2, or 3 boxes unchecked, I find that the log file lists "k-weight = 1, kw", where kw is the value I entered into the "other k weight" text box. If I choose 0 as the other k weight, then the log file lists "k-weight = 1". Is it possible to run a fit in Artemis using only a k-weight of something other than 1, 2, or 3? Thank you, George

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Re: [Ifeffit] particle size and coordination number in Ru nanoparticles on carbon
by Anatoly I Frenkel 20 Sep '11

20 Sep '11

Ru oxidizes easily. Since you fixed CN in bulk Ru as total 12 in the fit to hcp Ru it probably gave you a small amplitude factor for the foil. Thus when you transferred that small amplitude factor to fit NP Ru it resulted in large CN. We use freshly made Ru powders as standards. What amplitude factor have you got from the foil? Anatoly Sent from my mobile phone, please forgive typos. -----Original message----- From: Anatoly I Frenkel <afrenke2(a)yu.edu> To: Dreher Marian <Marian.Dreher(a)psi.ch>, "ifeffit(a)millenia.cars.aps.anl.gov" <ifeffit(a)millenia.cars.aps.anl.gov> Sent: Tue, Sep 20, 2011 18:27:57 GMT+00:00 Subject: Re: [Ifeffit] particle size and coordination number in Ru nanoparticles on carbon You have to be careful using Ru foil. Sent from my mobile phone, please forgive typos. -----Original message----- From: Dreher Marian <Marian.Dreher(a)psi.ch> To: "ifeffit(a)millenia.cars.aps.anl.gov" <ifeffit(a)millenia.cars.aps.anl.gov> Sent: Tue, Sep 20, 2011 18:00:15 GMT+00:00 Subject: [Ifeffit] particle size and coordination number in Ru nanoparticles on carbon 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, Marian.

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Re: [Ifeffit] particle size and coordination number in Ru nanoparticles on carbon
by Anatoly I Frenkel 20 Sep '11

20 Sep '11

You have to be careful using Ru foil. Sent from my mobile phone, please forgive typos. -----Original message----- From: Dreher Marian <Marian.Dreher(a)psi.ch> To: "ifeffit(a)millenia.cars.aps.anl.gov" <ifeffit(a)millenia.cars.aps.anl.gov> Sent: Tue, Sep 20, 2011 18:00:15 GMT+00:00 Subject: [Ifeffit] particle size and coordination number in Ru nanoparticles on carbon 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, Marian.

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Re: [Ifeffit] Spline range?
by Matt Newville 19 Sep '11

19 Sep '11

Wei, On Sun, Sep 18, 2011 at 9:10 AM, Wei Li <weili(a)udel.edu> wrote: > Dear all, > > I am wondering about what range should be chosen in Athena? Some literature > says from 1 to the end; some says from 0.5 to the end. What literature says this? Do you mean to imply that someone is saying it should be 0.5 or 1.0, and *not* some other value? In principle, the background should start at k=0, and one should use k-weight=1, as Integral_E=E0^E=infinity chi(E) dE = 0 Integral_k=0^k=infinity chi(k) * k * dk = 0 In practice, that is nearly useless beyond the suggestion that the integral (which is to say, the DC component), *should* be zero. Using kmin between 0 and 1 and k-weight between 0 and 2 usually "work best", especially in the sense of "stable". In my experience, the value of E0 is much more important than kmin, and it is hard to predict whether k-weight = 1 or 2 works better. My advice is to not over-think or spend too much time worrying about background subtraction. --Matt

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Spline range?
by Wei Li 18 Sep '11

18 Sep '11

Dear all, I am wondering about what range should be chosen in Athena? Some literature says from 1 to the end; some says from 0.5 to the end. Wei -- Wei Li Postdoc researcher Environmental Soil Chemistry Group Delaware Environmental Institute University of Delaware, Newark,19713 Tel:631-949-0663 http://ag.udel.edu/soilchem/li.html <http://ag.udel.edu/soilchem/>

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