mechanisms of fluorescence enhancement in rare earth sol ... filepai (post annealing immersion) re...
TRANSCRIPT
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: