Visible and NIR Upconverting Er3+–Yb3+ Luminescent Nanorattles and Other Hybrid PMO‐Inorganic Structures for In Vivo Nanothermometry

Abstract Lanthanide‐doped luminescent nanoparticles are an appealing system for nanothermometry with biomedical applications due to their sensitivity, reliability, and minimal invasive thermal sensing properties. Here, four unique hybrid organic–inorganic materials prepared by combining β‐NaGdF 4 and PMOs (periodic mesoporous organosilica) or mSiO 2 (mesoporous silica) are proposed. PMO/mSiO 2 materials are excellent candidates for biological/biomedical applications as they show high biocompatibility with the human body. On the other hand, the β‐NaGdF 4 matrix is an excellent host for doping lanthanide ions, even at very low concentrations with yet very efficient luminescence properties. A new type of Er 3+ –Yb 3+ upconversion luminescence nanothermometers operating both in the visible and near infrared regime is proposed. Both spectral ranges permit promising thermometry performance even in aqueous environment. It is additionally confirmed that these hybrid materials are non‐toxic to cells, which makes them very promising candidates for real biomedical thermometry applications. In several of these materials, the presence of additional voids leaves space for future theranostic or combined thermometry and drug delivery applications in the hybrid nanostructures.