Mechanisms of fluorescence enhancement in rare earth sol ... filePAI (Post Annealing Immersion) RE...
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Mechanisms of fluorescence enhancement in rare earth sol- gel glass containing Al 3+ A.J. Silversmith A. P. Beyler K.E. Arpino N.T.T. Nguyen Hamilton College Davidson College Whitman College D. M. Boye K. R. Hoffman
Transcript of Mechanisms of fluorescence enhancement in rare earth sol ... filePAI (Post Annealing Immersion) RE...
Mechanisms of fluorescenceenhancement in rare earth sol-
gel glass containing Al3+
A.J. SilversmithA. P. BeylerK.E. ArpinoN.T.T. Nguyen
Hamilton College
Davidson College
Whitman College
D. M. Boye
K. R. Hoffman
Mechanisms of fluorescenceenhancement in rare earth sol-
gel glass containing Al3+
A.J. SilversmithA. P. BeylerK.E. ArpinoN.T.T. Nguyen
Hamilton College
Davidson College
Whitman College
D. M. Boye
K. R. Hoffman
Sol-gel glass materials
SynthesisWater + TMOSRE3+ and Al3+ saltsAcid catalyst
PropertiesOptically clear monolithsDensity ~1.7g/cm3 (compared to 2.2g/cm3 for vitreous silica)Porous
gel drying………..dry
annealed
SiCH3
CH3
H3CH3C
RE’s in sol-gel silicate glass
• Dopant concentrations up to 5%
• Low fluorescence yield
• Today’s talkIncreased fluorescence yields with aluminum co-doping
• RE3+ associates preferentially with Al3+
• Local structure and vibrational energies altered
• Local symmetry depends on Al content
• Weaker coupling to host
Probe #1: Tb3+
• 5D3 sensitive to Al3+ content• 5D4 intensity unaffected
Ene
rgy
(100
0cm
-1)
414nm
7F6543
7F012
5D4
5D3
436nm
460nm
490nm
545nm
590nm
620nm
0
10
20
5D3 → 7FJ5D4 → 7FJ
0.02% Tb
4f8→4f75d
0.02% Tbλexc=250nm
1% Al0.02% Alno Al
RE3+ associates preferentially with Al3+
Effect of Al saturates above 10:1 Al:RE ratio
supports J. Lægsgaard, Phys. Rev. B, 65 (2002), 17411
5 D3:
5 D4 r
atio
0.02% Tb
Al:Tb is 10:1
Probe #2:Eu3+E
nerg
y (1
000c
m-1
)
7F0
12
5D0
620nm
0
10
20590nm
578nm
CT band
wavelength (nm)
fluor
esce
nce 5D0→7F0
5D0→7F1
5D0→7F2
5D0→7F1 is magnetic dipole allowed
Local structure and vibrational energies altered
5D0→7F2
0.1% Eu900oC, 6hr
0
Fully solvated REreturns to highersymmetry
0.1%Euλexc=250nm Low Al
concentrationlowers local RE sitesymmetry…..
no Al4% Al
0.1%Eu samples
Wavelength (nm)
Flu
ores
cenc
e (a
rb u
nits
)
Blue emission in sampleswith Al
λexc = 250nm
Tbexcitation,monitor542nm
wavelength (nm)
542n
m e
mis
sion
4f8→4f75d
transitions within 4f8
weaker coupling to hostwith Al co-dopant
PAI(Post Annealing Immersion)
RE dopantnear poresurface
RE dopant indensified material
K.E. Arpino et al. DPC2010 poster.
542n
m T
b3+ e
mis
sion
wavelength (nm)
no Al
1% Al
no Gd
Gd3+ absorptions
Low Al:RE ratio: site-symmetry is lowered. More admixtureof opposite parity wavefunctions and increased transitionprobabilities.
High Al:RE ratio: highest frequency phonons of lowerenergy. Nonradiative decay rates are reduced.
Clues from Europium study:
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 poresurfaces.
Conclusions
Thank you:
DPC organizers
NSF-MRI Grant #0959552Hamilton College
Supported by:
