Transcript Biomedical Applications of Plasma Spectroscopy: A Preliminary Study Dr. Unnikrishnan V. K. Associate Professor Department of Atomic and Molecular Physics Manipal University.

Biomedical Applications of Plasma Spectroscopy:
A Preliminary Study
Dr. Unnikrishnan V. K.
Associate Professor
Department of Atomic and Molecular Physics
Manipal University
Out line
۩ Introduction.
۩ Laser Induced Breakdown Spectroscopy (LIBS) Technique –
A tool for trace element analysis.
۩ Objectives of the programme.
۩ Methodology.
۩ Preliminary studies on LIBS.
۩ References.
Laser-Matter Interaction
Laser Beam
Atoms
Ions
Free electrons
Laser pulse intensity > Binding Energy of the electron
Plasma characterization: Degree of Ionization
Weakly ionized plasma
Highly ionized plasma
< 10 %
very high
Laser Induced Breakdown Spectroscopy (LIBS)
- Spectroscopic analysis of elemental emission from a Plasma created using laser
from any sample.
- Developed rapidly as a versatile analytical tool over the past two decades.
- Appealing technique compared with many other types of elemental analysis
because of its simplicity.
- Fast Multi-elemental analysis in short time (few seconds).
- Spatial discrimination at few microns apart; Micro analysis.
- Analysis of the surface with out damage to body of the sample.
Department of Chemistry, Changwon University, Changwon, Kyungnam, Korea
LIBS spectrum of a molten glass
Jong-IL Yun et al, Vol 56, 437-448, Applied Spectroscopy, 2002
Importance of the Study
Well being of all living things  environmental factors, food habits, life style etc.
Society needs, technology development etc.
Control of individual beings
Essential for health at trace levels
Trace Elements
Harmful at larger concentrations
Que: Trace element detection ??
Ans: LIBS Technique
Methodology
Design and Development of proposed LIBS set-up.
The main components of a LIBS set-up are
(1) Pulsed laser : generates the powerful optical pulses to form plasma
(2) Light focusing system: mirrors, lenses etc. that directs and focuses the laser
pulse on the sample.
(3) Sample holder.
(4) Light collection system: lens, mirror, fiber optic etc. that collects the plasma
and transports to the detection system.
(5) Detector: will disperse and record the light.
(6) Computer: store the spectrum.
LIBS Schematic.
Optics: Focusing system
Sample
Pulsed Laser
Optics: Collecting system
Computer
Delay Generator
High resolution Detector
Laser: Nd-YAG 3rd harmonic 355nm.
Optics: Focus & Collection
Energy = 100mJ, Repetition Rate = 10 Hz,
Pulse width = 6 ns, Peak power = 16.7 MW
Lens, Prisms, Mirrors,
Optical fiber (50 µm).
Detector: Michelle Spectrograph-ICCD
High spectral resolution, Broad collection
range,
Sensitive,
Delay
generator
embedded.
Filters,
Iris,
Calibration of Detection System.
- ensure the measurement accuracy and ability to carry out meaningful analysis of
acquired spectra from samples.
Wavelength Calibration
National Institute of Standards and Technology (NIST) certified Mercury-Argon lamp
Intensity Calibration
National Institute of Standards and Technology (NIST) certified Deuterium-QuartzTungsten- Halogen lamp
Calibration over a wide range i.e. 200-975 nm
Timing considerations.
450000
400000
Intensity (Counts)
350000
300000
250000
200000
150000
Optical signal intensity
100000
50000
Laser pulse
0
260
310
360
410
460
510
560
610
660
710
760
810
Wwavelength (nm)
Detector
1 ns
10 ns
100 ns 1 µs 10 µsec 100 µsec
Decay time after pulse incident on the target
Goal of LIBS technique: to measure an optically thin plasma whose elemental
composition is the same as that of the sample
Setting up of a sensitive LIBS system
Nd-YAG
laser
(355nm)
Computer
Pellin Broca Prism
355 mirror
Optical Fiber
Signal Collector
Beam Dump
High resolution Spectrograph-ICCD system- Michelle
Beam Splitter 20/80
Motorized horizondal/verical translation stages
Lens
Neutral Density Filter
Sample
Vaccum Chamber
Vs
Spectrograph-ICCD system
Parameter
Old
New
Wavelength Range (nm)
200-450
200-975
Spectral resolution (nm)
0.4
0.05
Grating
Diffraction
Echelle
Focal Length (mm)
150
195
Slit width (µm)
100
10
Active pixels (horizontal x
vertical )
1024 x 128
1024 x 1024
Coupling
Lenses
Fiber optic cable
Vs
contd..
200000
180000
160000
Intensity (Counts)
New
450000
Intensity (Counts)
400000
350000
300000
435.8nm
250000
140000
120000
100000
80000
60000
200000
40000
150000
20000
100000
0
50000
0
260
435
310
360
410
460
510
560
610
660
710
760
435.2
435.4
435.6
435.8
436
436.2
436.4
436.6
436.8
437
436.8
437
Wavelength (nm)
810
Wwavelength (nm)
Spectral resolution = 0.06 nm
35000
33000
31000
35000
Intensity (Counts)
Old
435.8nm
Intensity (Counts)
33000
31000
29000
27000
29000
27000
25000
23000
21000
25000
23000
19000
21000
19000
17000
17000
15000
15000
377
435
427
477
527
577
435.2
435.4
435.6
435.8
436
436.2
436.4
436.6
Wavelength (nm)
Wavelength (nm)
Spectral resolution = 0.74 nm
Hard tissue
Osteotome
Region 1
Region 2
Region 3
14000
Intensity (Counts)
12000
10000
8000
Ca 422.672nm
Ca 430.252nm
Ca 445.477nm
P 558.834nm
P 547.767nm
6000
Mg 518.36nm
4000
Mg 517.268nm
2000
0
200
400
600
Wavelength (nm)
800
Region 1
Region 2
Region 3
Calcium
9000
7500
7000
431.86nm
Intensity (Counts)
Intensity (Counts)
8000
422.67nm
430.25nm
445.48nm
558.87nm
559.85nm
6000
5000
4000
3000
2000
6000
4500
3000
1500
1000
0
431.25
431.50
431.75
432.00
432.25
1.0
432.50
1.5
2.0
2.5
Region
Wavelength (nm)
Region 1
Region 2
Region 3
Magnesium
518.36nm
8000
Intensity (Counts)
Intensity (Counts)
Phosphorous
1650
1500
1350
1200
1050
900
750
600
450
300
150
0
3.0
558.83nm
Region 1
Region 2
Region 3
7000
6000
5000
4000
3000
2000
1000
518.250
518.325
518.400
Wavelength (nm)
518.475
558.6 558.7 558.8 558.9 559.0 559.1 559.2
Wavelength (nm)
Ca 518.88nm
2500
Intensity (Counts)
Region 1
Region 2
Region 3
2000
Mg 518.36nm
1500
Mg 517.268nm
1000
500
0
517.0
517.5
518.0
518.5
519.0
Wavelength (nm)
519.5
520.0
References
Handbook of Laser-Induced Breakdown Spectroscopy by David A. Cremers and Leon
J. Radziemski, 2006.
 D. R. Alexander et al, “Environmental monitoring of soil contaminated with heavy
metals using Laser-Induced Breakdown Spectroscopy ”, IEEE, 1994.
 Karen Y. Yamamoto et al, “Detection of metals in the environment using a portable
Laser-Induced Breakdown Spectroscopy instrument”, Applied Spectroscopy, 1996.
 Russell S. Harmon et al, “Laser-Induced Breakdown Spectroscopy- An emerging
chemical sensor technology for real-time field portable, geochemical, mineralogical and
environmental applications”, Applied Geochemistry, 2006.
Acknowledgement
This research work is supported by Board of Research in Nuclear Sciences (BRNS).