XRF Microscopy and Micro-Spectroscopy -...
Transcript of XRF Microscopy and Micro-Spectroscopy -...
XRF Microscopy and Micro-Spectroscopy
Campinas 22/08/2016DVTEC – Laboratório de Instrumentação Nuclear
Asst. Prof. Hudson W.P. [email protected] of Applied X-ray Spectroscopy
CENA-USP
DVTEC – Laboratório de Instrumentação Nuclear
Overview
Micro-speciation, what for?
Sample preparation strategies
PCA and LC
Hands on: Quantitative analysis of Zn accumulation spot the
body of Daphnia magna
XRF Microscopy and Micro-Spectroscopy
USB Stick Lecture
Data for hands on tutorial
Literature
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Micro-speciation, what for?
XRF Microscopy and Micro-Spectroscopy
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Speciation using hard X-rayWhich spectroscopic tools?
XANES
Pre-edge
EXAFS
XRF weak lines
1XRF Microscopy and Micro-Spectroscopy
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Why Micro-Speciation ? A simple example from materials science
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A catalytic reactor: A tube filled with SiO2+ few wt% of a transition metal
Gas inlet Gas outlet
Is the metal chemical species the same along the tube?
P 1 P 2 P 3 P 4 P 5 P 6
XRF Microscopy and Micro-Spectroscopy
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Cu and Zn species depend on the position
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Long time ago, catalysis scientists realized that catalysts must be studied in operando.
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What about plants? Plants are far more complex than a glass tube with SiO2 inside!
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0.90 mm
Two approaches:Where is it? What is it?
Xylem
Phloem
Phaseolus vulgaris, stem cross sectionTatiane Nishida, Masters ThesisCENA-USP
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What about plants? Plants are far more complex than a glass tube with SiO2 inside!
5
0.90 mm
Two approaches:Where is it? What is it?
Xylem Phloem
Would you expect Feand Ca to be homogenously distributed?
Phaseolus vulgaris, stem cross sectionTatiane Nishida, Masters ThesisCENA-USP
XRF Microscopy and Micro-Spectroscopy
X-ray Absorption Spectroscopy for the Direct Analysis of Solids
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Elemental distribution
Distribution is discrete!
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Ca
Fe
And the speciation?
Phaseolus vulgaris, stem cross sectionTatiane Nishida, Masters ThesisCENA-USPData record at LIN-CENA with an Orbis PC EDAX
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Phytopatology leaf of Syzygium spp. carrying rust disease. At the disease spot one can see higher P and S concentration, whereas Ca is lower and K completely absent. Fe is distributed along the leaf presenting hotspots
7XRF Microscopy and Micro-Spectroscopy
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Chemical speciation Distribution is discrete!
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Phaseolus vulgaris, splitted beanSusi Savassa, Doctoral ThesisCENA-USPData recorded at XRF-LNLS
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Sample preparation strategies
XRF Microscopy and Micro-Spectroscopy
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Several possibilities
X- not recomended for speciation
or radiation dose is <106
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Is this procedure correct?
Cut Oven dried
For micro distribution: maybe yes…
For speciation: probably not http://www.agencia.cnptia.embrapa.br/Repositorio/muda_000fkmu488h02wyiv80sq98yq5k5aq1s.jpg
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Some examples from our group @CENA-USP
In vivo spectroscopy
μ-XRF
XAFS2-LNLS
HH-XRFXRF-LNLS
XRF Microscopy and Micro-Spectroscopy
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PCA and LC
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12XRF Microscopy and Micro-Spectroscopy
Procedure/mechanics
Component 1Component 2Component 2
Energy (eV)Number of pure
components
Pure spectra
Energy (eV)
Tem
pe
ratu
re
Tim
e
pH
Spectrum 1Spectrum 2Spectrum 3Spectrum 4Spectrum 5Spectrum 6Spectrum 7Spectrum 8Spectrum 9
Set of XAS data
c1
Concentration profiles
c2 c3
Tem
pe
ratu
re (
oC
)
How many components in total? The same as the number of spectra
How many principal components? PCA tells us you
How do I know whether a reference is part of the mixture?Target transformation
Once you know how many PC and the references….Perform linear combination fitting
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13XRF Microscopy and Micro-Spectroscopy
Example: Transformation of Mo under reaction conditions
How many principal components?
How is Mo converted from one state to another?
Are there any intermediates?
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14XRF Microscopy and Micro-Spectroscopy
How many principal components?
Three PC seems to be suitable
Example: Transformation of Mo under reaction conditions
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15XRF Microscopy and Micro-Spectroscopy
Example: Transformation of Mo under reaction conditions
Linear combination analysis
DVTEC – Laboratório de Instrumentação Nuclear XRF Microscopy and Micro-Spectroscopy
Hands on:Quantitative analysis of Zn accumulation spot
in the body of Daphnia magna
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16XRF Microscopy and Micro-Spectroscopy
Daphnia magna is a bio indicator
Chemical image recorded in our lab at CENA-USP
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17XRF Microscopy and Micro-Spectroscopy
Daphnia magna is a bio indicator
Our equipment, Orbis PC, already plots the intensities
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18XRF Microscopy and Micro-Spectroscopy
Quantitative XRF
IF = C.S.A
Elemental sensitity ≈ geometry, absorption, fluorescence yield, detector efficiency....
Absorption factor:Thin samples = 1 Thick samples= 1 / μ ρ D ( infinity thickness)
Concentration
Is the sample is thin
C = IF / S How to calculate the sensitivity?
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19XRF Microscopy and Micro-Spectroscopy
Use a standard reference material to determine the sensitivity
51.6 51.8 52.0 52.2
33.8
34.0
34.2
coordinate xC
oord
inate
y
180.0
186.1
192.3
198.4
204.5
210.6
216.8
222.9
229.0
Net intensity
1st open the ‘Padrão Zn micromatter’ excel file 2nd Since the reference is not homogenous, take the average signal 3rd Determine the equipment's sensitivity for Zn
Standard: ZnTe 47.70 μg cm-2
Zn 16.16 μg cm-2
All coordinates in mm
http://www.micromatter.com/xrf.php
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Plot the D. magnas’ data
4th open the ‘D_magna_nano_ZnO_treated’ excel file 5th Convert the intensities to concentration using the formula C =If / S 6th Plot the data
48.2 48.0 47.8 47.6 47.4 47.2
36.8
36.6
36.4
36.2
36.0
coordinate x
coord
inate
y
20.00
415.0
810.0
1205
1600
1995
2390
2785
3180
Net intensity
48.2 48.0 47.8 47.6 47.4 47.2
36.9
36.8
36.7
36.6
36.5
36.4
36.3
36.2
36.1
36.0
coordinate x
coord
inate
y
2.000
33.25
64.50
95.75
127.0
158.3
189.5
220.8
252.0
ug cm^-2
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21XRF Microscopy and Micro-Spectroscopy
Plot the D. magnas’ data
D. magnaJoyce Paula, Doctoral ThesisCENA-USPData recorded at our lab
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Summary
X-ray Absorption Spectroscopy for the Direct Analysis of Solids 22
Micro analysis:Useful when samples are not homogenous in micro scale level Allows you to locate and explore the chemical environment
Sample preparation: Main rule: don’t change your sample into something else
PCA and LC:Helps you to solve mixtures
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Recommended Literature
XRF Microscopy and Micro-Spectroscopy
Regular courses @CENA-USP / 2nd Semester
CEN5792- Principles of Nuclear and Electronic Spectroscopy (Aug-Sep)
CEN5785- Introduction to XRF and XAFS Spectroscopy (Oct-Dec)
Thank You [email protected]
Young Researcher FAPESP 2015-2019/05942-0 Multi-User Equipment FAPESP 2015-2017/19121-8 SPRINT FAPESP 2016-2018/50014-6 FINEP 01.12.0535.00 USP-Santander Mobilidade Novos Docentes 2016/2017
Funding:
Group of Applied X-ray Spectroscopyhttp://hudson731.wix.com/xraysatcena
X-rays Enlightening the Fate of Nanomaterials in Agriculture and Environment
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PPG CENA Nota 7 Capes Título: Ciências
X-rays Enlightening the Fate of Nanomaterials in Agriculture and Environment