Dynamics of photon-induced degradation and fluorescence in riboflavin microparticles |
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| Authors: | Y.-L. Pan R.G. Pinnick S.C. Hill S. Niles S. Holler J.R. Bottiger J.-P. Wolf R.K. Chang |
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| Affiliation: | (1) Physical Sciences Laboratory, New Mexico State University, Las Cruces, NM 88003, USA, US;(2) US Army Research Laboratory, Adelphi, MD 20783-1197, USA, US;(3) Department of Applied Physics and Center for Laser Diagnostics, Yale University, New Haven, CT 06520, USA, US;(4) US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, ML 21010, USA, US;(5) LASIM (UMR5579), Université Claude Bernard Lyon 1, 43 bd du 11 Novembre, 69622 Villeurbanne Cedex, France, FR |
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| Abstract: | An unexpected blue-fluorescence band (around 420 nm) from both micrometer-sized dried particles and aqueous droplets of riboflavin [7,8-dimethyl-10-(D-1′-ribityl)-isoalloxazine] is observed when the microparticles are irradiated with a pulsed UV (355- or 351-nm) laser. The intensity of the band increases quadratically with input laser energy density (fluence) and is attributable to a one-photon-excited fluorescence of lumichrome (7,8-dimethyl-alloxazine) that is produced by photo-degradation of riboflavin. The well-known greenish-yellow fluorescence band (at 560 nm for dried particles and 535 nm for aqueous droplets) from riboflavin increases sublinearly with UV-laser fluence. With a laser input fluence above 5 J/cm2 the riboflavin fluorescence decays earlier and the lumichrome fluorescence reaches a maximum later than the peak of the input laser pulse. The temporal dynamics of the 420- and 535-nm fluorescence peaks are consistent with a rate-equation simulation of photon-induced conversion of riboflavin to lumichrome and the subsequent fluorescence of lumichrome. Received: 28 September 2000 / Revised version: 11 December 2000 / Published online: 21 February 2001 |
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| Keywords: | PACS: 42.62Be 82.50Fv 87.15Mi |
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