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 Weakly ionized plasma Highly ionized plasma < 10 % very high Laser pulse intensity > Binding Energy of the electron Laser Beam Atoms Ions Free electrons Plasma characterization: Degree of Ionization

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, , 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 Trace Elements Essential for health at trace levels 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.

Laser: Nd-YAG 3 rd harmonic 355nm. Energy = 100mJ, Repetition Rate = 10 Hz, Pulse width = 6 ns, Peak power = 16.7 MW Pulsed Laser High resolution Detector Computer Delay Generator Optics: Focusing system Optics: Collecting system Sample Optics: Focus & Collection Lens, Prisms, Mirrors, Filters, Iris, Optical fiber (50 µm). Detector: Michelle Spectrograph-ICCD High spectral resolution, Broad collection range, Sensitive, Delay generator embedded. LIBS Schematic.

Calibration of Detection System. Wavelength Calibration Intensity Calibration National Institute of Standards and Technology (NIST) certified Mercury-Argon lamp National Institute of Standards and Technology (NIST) certified Deuterium-Quartz- Tungsten- Halogen lamp - ensure the measurement accuracy and ability to carry out meaningful analysis of acquired spectra from samples. Calibration over a wide range i.e nm

1 ns10 ns100 ns1 µs10 µsec100 µsec Laser pulse Optical signal intensity Decay time after pulse incident on the target Detector Plasma continuum Timing considerations. Goal of LIBS technique: to measure an optically thin plasma whose elemental composition is the same as that of the sample

Nd-YAG laser (355nm) Pellin Broca Prism 355 mirror Beam Splitter 20/80 Lens Neutral Density Filter Beam Dump Vaccum Chamber Optical Fiber Computer Sample High resolution Spectrograph-ICCD system- Michelle Signal Collector Motorized horizondal/verical translation stages Setting up of a sensitive LIBS system

Vs Parameter Spectrograph-ICCD system Old Wavelength Range (nm) Spectral resolution (nm)0.4 GratingDiffraction Focal Length (mm)150 Slit width (µm)100 Active pixels (horizontal x vertical ) 1024 x 128 CouplingLenses New Echelle x 1024 Fiber optic cable

435.8nm Spectral resolution = 0.06 nm Spectral resolution = 0.74 nm Vs contd..

Region 1 Region 2 Region 3 Hard tissue Osteotome

References  Handbook of Laser-Induced Breakdown Spectroscopy by David A. Cremers and Leon J. Radziemski,  D. R. Alexander et al, “Environmental monitoring of soil contaminated with heavy metals using Laser-Induced Breakdown Spectroscopy ”, IEEE,  Karen Y. Yamamoto et al, “Detection of metals in the environment using a portable Laser-Induced Breakdown Spectroscopy instrument”, Applied Spectroscopy,  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, Acknowledgement This research work is supported by Board of Research in Nuclear Sciences (BRNS).