Concentration Measurements of Porphyrin Solutions using the Cavity Ring-Down in addition to

Concentration Measurements of Porphyrin Solutions using the Cavity Ring-Down in addition to www.phwiki.com

Concentration Measurements of Porphyrin Solutions using the Cavity Ring-Down in addition to

Dell’Oro, Tam, Founder, President, and Senior Analyst has reference to this Academic Journal, PHwiki organized this Journal Concentration Measurements of Porphyrin Solutions using the Cavity Ring-Down in addition to Integrated Cavity Output Spectroscopy Techniques Deirdre O’Leary PY4060 Final Year Project March 2005 Supervisor: Dr A.A. Ruth Outline Introduction Techniques Cavity Ring-Down Spectroscopy Integrated Cavity Output Spectroscopy The Experiment Results Conclusions Introduction Beer’s Law: Measurement of Concentration : Measure Io in addition to It Measure d Knowledge of e(l) Sample Io(l) It(l) d

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Conventional Techniques Measure difference in intensity between It in addition to Io Problem: Inherently Weak Absorptions Difficulty in measuring the difference between It in addition to Io Solution Returning to Beer’s Law: Long path lengths Multi-pass cells Optical Cavity Methods Cavity Ring-Down Spectroscopy Integrated Cavity Output Spectroscopy The Optical Cavity Empty Cavity R R Intensity Time d

The Optical Cavity L Empty Cavity Additional losses of L per pass R R R R Intensity Time Time Intensity d d Experimental Set-Up Pulsed laser Iris Iris Cuvette Oscilloscope Computer PM tube Cavity High Reflectivity Mirrors Cavity Ring-Down Spectroscopy (CRDS) Detector Cavity Laser beam d

CRDS Measurement Principle Measurement of the ‘Ring-Down time’ Empty Cuvette & Solvent Cuvette & Solution Integrated Cavity Output Spectroscopy (ICOS) . Measurement of the total transmitted intensity: Transmitted intensity (subject to losses L per pass): ICOS Measurement Principle Cavity d Laser beam time intensity Detector Empty Cavity

ICOS Measurement Principle Cavity d Laser beam Detector time intensity Cuvette in addition to Solvent ICOS Measurement Principle Cavity d Detector Laser beam intensity time Cuvette in addition to Solution Lambert-Beer Losses Knowledge of the losses L may be obtained from either technique thus enabling the calculation of concentration. For low losses: exp (-e(l) C d) = 1 – e(l) C d Applying Beer’s Law: It = Io (1 – L) = Io exp (-e(l) C d) = Io (1 -e(l) C d) C =

Platinum Octaethyl Porphyrin Absorption Spectrum of PtOEP (xx mM) 532 nm The Experiment The absorption of various porphyrin solutions was analysed at 532 nm CRD in addition to ICOS techniques were implemented to calculate the losses due to absorption This enabled the calculation of the concentration of each solution Intensity versus time plot 12 nMol Porphyrin Solution

Losses due to Cuvette & Solvent Solvent 103 L Consistency of Measurements Experiment per as long as med to establish the reproducibility of results Large variance in results Possible reason: Inexact alignment of beam along cavity optical axis in addition to cuvette alignment Trial No. Intensity The Cuvette Losses in the cuvette Cuvette consists of four interfaces between different media Reflections occur at each surface Two configurations as long as minimal reflection loss: Incident Beam normal to the surface Beam incident at Brewster’s angle In this experiment the incident beam was normal to the surface Cuvette alignment is critical in this configuration, huge losses otherwise Design of Cuvette holder to allow as long as fine adjustment of the position of the Cuvette in the beam of the laser

Other Difficulties Fluctuations in the laser intensity Renders the ICOS measurements inaccuate CRD data is not affected by fluctuations because CRD is intensity independent Experimental Conditions Optical Cavity is not closed off to surroundings Dust on mirror, scattering in open cavity etc. Experimental Methodology Systematic approach to recording the data Measurements as long as the reference, empty, in addition to sample per as long as med over a short time scale. Results Conclusions Successfully implemented CRD in addition to ICOS techniques Difficulties encountered Fluctuations in the laser intensity Cuvette losses!!!

Dell'Oro, Tam Dell'Oro Group Founder, President, and Senior Analyst www.phwiki.com

Outlook Many Possibilities . Investigation of the effect of dissolved oxygen on absorption: comparison between st in addition to ard in addition to de-gassed samples Obtain an absorption spectrum Simultaneous monitoring of absorption in addition to emission of PtOEP Acknowledgements I would like to thank the following people: Dr. A.A. Ruth Kieran Lynch All members of the Laser Spectroscopy group

Dell’Oro, Tam Founder, President, and Senior Analyst

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