Au/SiO2 nanoparticles in TiO2:Sm3+ films for improved fluorescence sensing of oxygen

Abstract

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.