The luminescence properties of Sm3+ in
sol–gel-made nanostructural TiO2 were shown to depend on surrounding
gas environment.
Both the intensity and lifetime of the luminescence
increased with increasing oxygen content varied between 0% and 100% in the O2/N2
mixture at normal pressure. The luminescence decay kinetics after pulsed
excitation at 355 nm followed the stretched exponential function with the
value of stretching exponent equal to 0.4–0.5.
The mechanism of oxygen sensitivity was interpreted
as resonant excitation energy transfer from Sm3+ to the acceptor
defects, the latter being switched on and off the resonance by electron
exchange with surface-adsorbed oxygen. Oxygen vacancy related defects were
proposed as most likely candidates of energy acceptors. The studied material
can be used for luminescence lifetime based optical oxygen sensor.
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