Au/SiO2 nanoparticles in TiO2:Sm3+ films for improved fluorescence sensing of oxygen†
A strong increase in Sm3+ fluorescence intensity caused by oxygen gas is revealed for TiO2:Sm3+ films decorated with Au/SiO2 nanoparticles in spite of the general view of oxygen as a quenching agent. Microluminescence studies revealed that emission from Sm3+ ions excited by UV light is concentrated around Au/SiO2 nanoparticles, which implies its sensitization by gold. Periodic changes in the oxygen concentration in the O2:N2 gaseous mixture led to respective modulation of the intensity of Sm3+ fluorescence. The changes in fluorescence intensity were up to 10 times more pronounced for the samples decorated with Au/SiO2 nanoparticles in comparison with virgin TiO2:Sm3+ films. It is suggested that Sm3+ fluorescence is sensitized by energy transfer from gold clusters presented on the surface of the Au/SiO2 nanoparticles. The oxygen-sensing effect is explained by the model in which oxygen changes the state of energy accepting defects in the TiO2 lattice and in such a way prevents their participation in quenching of Sm3+ fluorescence.