1 christian vogel, manfred ramsteiner and christian adam deep ultraviolet raman microspectroscopy...
TRANSCRIPT
1
Christian Vogel, Manfred Ramsteiner and Christian Adam
Deep Ultraviolet Raman Microspectroscopy – Novel Technique
for the Characterization of Phosphorus in Soil
BAM Federal Institute for Materials Research and Testing, Berlin, Germany
Paul-Drude-Institut, Berlin, Germany
2
Introduction
• Deep ultraviolet (DUV) Raman microspectroscopy
• Detection of P-Phases in soil
• Advantages and Disadvantages of DUV Raman microspectroscopy
• Outlook
• Conclusions
3
Deep Ultraviolet (DUV) Raman Microspectroscopy - Theory
The electronic resonance enhancement effect can increase the intensity of the scattered light by a factor of 106.
from Asher, Analytical Chemistry, 1993, 65(2), 59A-66A
4
UV/VIS
Guanosine-5´-monophosphate
from Dietzek et al., Chapter 2 in Confocal Raman Microscopy (Springer 2010)
Deep Ultraviolet (DUV) Raman Microspectroscopy – Enhancement Effect
5
Deep Ultraviolet (DUV) Raman Microspectroscopy - Fluorescence
from www.semrock.com/uv-raman-spectroscopy.aspx
6
DUV Raman Microspectroscopy of an Alluvial Soil
Alluvial Soil: pH(H2O) = 7.4; P = 0.36 wt.%
Instrument: HORIBA LabRam HR Evolution; Laser: 244 nm (Ar-Ion); Lateral Resolution: 1 µm; Spectral Resolution: 8 cm-1; Time: approx. 1h; Imaged Area: 15 x 15 µm2
7
DUV Raman Spectra of Different Phosphates
AlPO4 (Berlinite)
Hydroxyapatite
Ca-Phytate
Fe-Phytate
Na-Phytate
500 1000 1500 2000Wavenumber (cm-1)
8
Advantages and Disadvantages of DUV Raman Microspectroscopy
Advantages:
• Detection of organic and inorganic
phosphates
• High lateral resolution
(theoretical down to 150 nm)
• Almost no samples preparation required
• No fluorescence appears
Disadvantage:
• Localization of P-phases
9
Outlook
Problem of P Localization Combination with laboratory micro X-ray
fluorescence (µ-XRF)
µ-XRF Mapping of the Alluvial soil
Instrument: HORIBA XGT 7200; Area: 512 x 512 µm2; Lateral Resolution: 10 µm; Time: 5 min
P Kα1 Ca Kα1 Si Kα1
10
Conclusions
• Chemical state of inorganic and organic phosphates is detectable
by DUV Raman Microspectroscopy
• Almost no sample pre-treatment is required
• Combination with µ-XRF make it easier to localize P-phases