Fluo, 0.5 wt% Cu.

On 22 Apr 2023, at 11:41 am, Anatoly Frenkel mailto:anatoly.frenkel@stonybrook.edu> wrote:

Fluorescence or transmission? What is the Cu concentration? Could be self absorption.

Anatoly

...

On Apr 21, 2023, at 9:31 PM, Joel Brugger mailto:joel.brugger@monash.edu> wrote:

Dear list,

We are trying to fit EXAFS from data collected on solutions within a capillary. The capillary has OD 1mm, ID 0.8mm, and was placed horizontally. The beam is 1x2 mm (VxH).

Fitting the copper reference foil, we get the expected SO2 value of ~0.7.

However, the solution containing the Cu(II) aqua ion gives a coordination of 2, instead of the expected 5-6. So our SO2 for this solution is apparently ~0.25.

I couldn’t find a discussion of the effect of geometry (in our case cylindrical rather than planar) on SO2. Is it possible that the low SO2 is a result of the odd geometry?

Confused as ever,

JOEL

Joël Brugger Professor of Synchrotron Geosciences

Monash University School of Earth, Atmosphere and Environment Room 257A, Level 2, 9 Rainforest Walk x-apple-data-detectors://2 Clayton, Victoria 3800 x-apple-data-detectors://2 Australia x-apple-data-detectors://2

T: +61 3 9905 4898 tel:+61%203%209902%209095 E: Joel.Brugger@monash.edu mailto:Andrew.Mackintosh@monash.edu Twitter: @JoelBrugger

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Capillary is silica glass :-)

On 22 Apr 2023, at 11:57 am, Anatoly Frenkel wrote:

Capillary made or what?

Anatoly

...

On Apr 21, 2023, at 9:52 PM, Joel Brugger wrote:

Fluo, 0.5 wt% Cu.

...

On 22 Apr 2023, at 11:41 am, Anatoly Frenkel mailto:anatoly.frenkel@stonybrook.edu> wrote:

Fluorescence or transmission? What is the Cu concentration? Could be self absorption.

Anatoly

...

On Apr 21, 2023, at 9:31 PM, Joel Brugger mailto:joel.brugger@monash.edu> wrote:

Dear list,

We are trying to fit EXAFS from data collected on solutions within a capillary. The capillary has OD 1mm, ID 0.8mm, and was placed horizontally. The beam is 1x2 mm (VxH).

Fitting the copper reference foil, we get the expected SO2 value of ~0.7.

However, the solution containing the Cu(II) aqua ion gives a coordination of 2, instead of the expected 5-6. So our SO2 for this solution is apparently ~0.25.

I couldn’t find a discussion of the effect of geometry (in our case cylindrical rather than planar) on SO2. Is it possible that the low SO2 is a result of the odd geometry?

Confused as ever,

JOEL

Joël Brugger Professor of Synchrotron Geosciences

Monash University School of Earth, Atmosphere and Environment Room 257A, Level 2, 9 Rainforest Walk x-apple-data-detectors://2 Clayton, Victoria 3800 x-apple-data-detectors://2 Australia x-apple-data-detectors://2

T: +61 3 9905 4898 tel:+61%203%209902%209095 E: Joel.Brugger@monash.edu mailto:Andrew.Mackintosh@monash.edu Twitter: @JoelBrugger

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Thanks Rob., Good thought, but definitively Cu++; we get the right energy shift and the right shape for XANES (linear Cu+ is very distinctive). We actually maintain nice oxidising conditions (4 bar of air applied to the capillary), and the spectra were stable over time (slew scan mode, with ~5 minutes per scan, and 10 scans collected). Note that Cu+ is not stable in solution unless you give it a ligand such as chloride; reduction to Cu+ in our solution most likely would result in precipitation of Cu(0) via disproportionation. No evidence for this at all.

On 22 Apr 2023, at 12:14 pm, Robert Gordon wrote:

Hi Joel,

How much edge shift are you seeing between your foil and the solution? Cu+2 is about 4.5 eV up from Cu metal...you seeing about that much?

Cu+2 can photoreduce...I know Cu+(aq) isn't stable, but maybe some complex is forming? Just a thought...CN=2 and I think linear Cu+

-R.

On 2023-04-21 6:58 p.m., Joel Brugger wrote:

...

Capillary is silica glass :-)

...

On 22 Apr 2023, at 11:57 am, Anatoly Frenkel mailto:anatoly.frenkel@stonybrook.edu> wrote:

Capillary made or what?

Anatoly

...

On Apr 21, 2023, at 9:52 PM, Joel Brugger mailto:joel.brugger@monash.edu> wrote:

 Fluo, 0.5 wt% Cu.

...

On 22 Apr 2023, at 11:41 am, Anatoly Frenkel mailto:anatoly.frenkel@stonybrook.edu> wrote:

Fluorescence or transmission? What is the Cu concentration? Could be self absorption.

Anatoly

...

On Apr 21, 2023, at 9:31 PM, Joel Brugger mailto:joel.brugger@monash.edu> wrote:

 Dear list,

We are trying to fit EXAFS from data collected on solutions within a capillary. The capillary has OD 1mm, ID 0.8mm, and was placed horizontally. The beam is 1x2 mm (VxH).

Fitting the copper reference foil, we get the expected SO2 value of ~0.7.

However, the solution containing the Cu(II) aqua ion gives a coordination of 2, instead of the expected 5-6. So our SO2 for this solution is apparently ~0.25.

I couldn’t find a discussion of the effect of geometry (in our case cylindrical rather than planar) on SO2. Is it possible that the low SO2 is a result of the odd geometry?

Confused as ever,

JOEL

Joël Brugger Professor of Synchrotron Geosciences

Monash University School of Earth, Atmosphere and Environment Room 257A, Level 2, 9 Rainforest Walk x-apple-data-detectors://2 Clayton, Victoria 3800 x-apple-data-detectors://2 Australia x-apple-data-detectors://2

T: +61 3 9905 4898 tel:+61%203%209902%209095 E: Joel.Brugger@monash.edu mailto:Andrew.Mackintosh@monash.edu Twitter: @JoelBrugger

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