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Mechanisms of fluorescence enhancement in rare earth sol-gel glass containing Al 3+

Mechanisms of fluorescence enhancement in rare earth sol-gel glass containing Al 3+. Hamilton College. D. M. Boye. Davidson College. K. R. Hoffman. Whitman College. A.J. Silversmith A. P. Beyler K.E. Arpino N.T.T. Nguyen.

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Mechanisms of fluorescence enhancement in rare earth sol-gel glass containing Al 3+

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  1. Mechanisms of fluorescence enhancement in rare earth sol-gel glass containing Al3+ Hamilton College D. M. Boye Davidson College K. R. Hoffman Whitman College A.J. Silversmith A. P. Beyler K.E. Arpino N.T.T. Nguyen

  2. Mechanisms of fluorescence enhancement in rare earth sol-gel glass containing Al3+ Hamilton College D. M. Boye Davidson College K. R. Hoffman Whitman College A.J. Silversmith A. P. Beyler K.E. Arpino N.T.T. Nguyen

  3. Sol-gel glass materials CH3 Si H3C CH3 H3C • Synthesis • Water + TMOS • RE3+ and Al3+ salts • Acid catalyst • Properties • Optically clear monoliths • Density ~1.7g/cm3 (compared to 2.2g/cm3 for vitreous silica) • Porous gel drying………..dry annealed

  4. RE’s in sol-gel silicate glass • RE3+ associates preferentially with Al3+ • Local structure and vibrational energies altered • Local symmetry depends on Al content • Weaker coupling to host • Dopant concentrations up to 5% • Low fluorescence yield • Today’s talk Increased fluorescence yields with aluminum co-doping

  5. Probe #1: Tb3+ 5D3  7FJ 5D4  7FJ 0.02% Tb 4f84f75d 5D3 5D4 20 414nm Energy (1000cm-1) 620nm 545nm 590nm 490nm 436nm 460nm 10 7F0 1 2 3 • 5D3 sensitive to Al3+ content • 5D4 intensity unaffected 4 5 7F6 0

  6. 0.02% Tb exc=250nm 1% Al 0.02% Al no Al RE3+ associates preferentially with Al3+

  7. Effect of Al saturates above 10:1 Al:RE ratio Al:Tb is 10:1 5D3:5D4 ratio 0.02% Tb supports J. Lægsgaard, Phys. Rev. B, 65 (2002), 17411

  8. Probe #2:Eu3+ CT band 5D07F2 5D07F1 20 5D07F0 fluorescence 5D0 Energy (1000cm-1) 578nm 590nm 620nm 10 wavelength (nm) 2 1 5D07F1 is magnetic dipole allowed 0 7F0

  9. Local structure and vibrational energies altered 5D07F2 0.1% Eu 900oC, 6hr 0

  10. 0.1%Eu exc=250nm Low Al concentration lowers local RE site symmetry….. Fully solvated RE returns to higher symmetry

  11. 4% Al no Al 0.1%Eu samples Blue emission in samples with Al exc = 250nm Fluorescence (arb units) Wavelength (nm)

  12. Tb excitation, monitor 542nm 4f84f75d 542nm emission transitions within 4f8 wavelength (nm) weaker coupling to host with Al co-dopant

  13. PAI(Post Annealing Immersion) RE dopant in densified material RE dopant near pore surface K.E. Arpino et al. DPC2010 poster.

  14. Gd3+ absorptions 542nm Tb3+ emission no Al 1% Al no Gd wavelength (nm)

  15. Conclusions Clues from Europium study: Low Al:RE ratio: site-symmetry is lowered. More admixture of opposite parity wavefunctions and increased transition probabilities. High Al:RE ratio: highest frequency phonons of lower energy. Nonradiative decay rates are reduced. Clues from Terbium study: RE ions associate preferentially with Al. Al decreases the coupling between RE electrons and host. Al may modify the location of RE dopants relative to pore surfaces.

  16. Thank you: DPC organizers Supported by: NSF-MRI Grant #0959552 Hamilton College

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