CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

Appearance of a broad host excitation peak ~ 360 nm in the excitation spectrum by
monitoring Eu 3+ emission around 615 nm suggests that Eu 3+ emission can be observed by
exciting the host at 360 nm. This is possible only when excited charge carriers in GaOOH
host transfers its energy to Eu 3+ ions. In other words, energy transfer occurs from host
GaOOH nanorods to Eu 3+ species. Similar results were also observed with GaOOH:Tb 3+ and
GaOOH:Dy 3+ samples. Representative emission and excitation spectra from GaOOH:Dy 3+ (1
at % Dy 3+ ) are shown in Fig.28.
Intensity
1000
750
500
250
4 F 9/2
6 H 15/2
4 F 9/2
6 H 13/2
Intensity
1000 4 K 17/2
6 P 7/2 6 P 5/2
750
500
6 H 15/2
0
400 450 500 550 600 650
Wavelength (nm)
(a)
(b)
250
200 250 300 350 400
Wavelength (nm)
Fig.28. (a) Emission spectrum obtained by exciting the samples at 280 nm and (b) excitation
spectrum for the emission at 575 nm from GaOOH nanorods prepared in the presence
of 1 at % Dy 3+ ions.
Energy transfer efficiency (η) has been calculated from the emission spectrum of
GaOOH and GaOOH:Dy 3+ nanorods based on the equation, η= 1-I d /I d0 , where I d and I d0 are
intensity of emission in presence and absence of Dy 3+ ions, respectively [56]. The efficiency
is ~32% for GaOOH:Dy 3+ . Generally, high values of energy transfer efficiency (of the order
of 90%) are observed for lanthanide ions when incorporated in hosts like Ga 2 O 3 . Such a low
value of energy transfer efficiency indicates that the lanthanide ions are not incorporated in
GaOOH host, but forms a separate Ln 3+ species, which is intimately mixed with the GaOOH/
amorphous gallium hydroxide phase. Due to this intimate mixing there can be some Ln 3+
species close to the surface of GaOOH and this leads to the weak energy transfer.
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