Abstract

In this work, we report the synthesis and characterisation of holmium-doped lanthanum indium oxide as a promising luminescent material for biomedical applications. Samples were prepared via the Pechini sol-gel method and structurally confirmed to crystallise in an orthorhombic perovskite phase (Pnma), with minor In2O3 impurities. Morphological analysis revealed irregular micrometric agglomerates with homogeneous elemental distribution. Optical studies demonstrated efficient absorption at 890 nm (the first biological window) and emission centred at similar to 1200 nm (the second biological window), attributed to the I-5(6) -> I-5(8) transition of Ho3+. The sample doped with 1.0 mol% Ho3+ exhibited the highest emission intensity. Luminescence tests confirmed detectable luminescence through up to 4 mm of blood, highlighting the material's potential for deep-tissue imaging. These results position LaInO3:Ho3+ as a viable candidate for infrared bioimaging working in the first and the second biological windows simultaneously.