La2O3: Tm, Yb, Er upconverting nano-oxides for sub-tissue lifetime thermal sensing

Abstract

The importance of non-invasive thermometry based on lifetime fluorescence in biomedical applications imposes the research and development of new phosphors. In this work, sub-tissue lifetime thermal sensing of La2O3: Ln3+ nanomaterials (Ln=Tm, Er and Yb) has been studied. Two oxides are investigated: Er3+, Tm3+, Yb3+ tri-doped La2O3 and Tm3+, Yb3+ co-doped La2O3. We have focused on the lifetime of the 1G4→3H6 transition that corresponds to the blue emission of Tm3+ ion, recorded at 480nm. We prove that tri-doped oxide has remarkable higher thermal sensitivity than the co-doped one, with a temperature coefficient estimated to 6.7×10−3°C−1, which is comparable to that of nanomaterials oxides previously studied for luminescence thermometry and reported in literature. We have described the setup used to carry out the sub-tissue lifetime thermal sensing realized on biological tissue in the temperature range between 25°C and 60°C.