New heater@luminescent thermometer nano-objects: Prussian blue core@silica shell loaded with a β-diketonate Tb3+/Eu3+ complex†

We report on the synthesis and investigation of new multifunctional Prussian blue (PB) nanoparticles coated by a mesoporous silica shell and loaded with a luminescent [(Tb/Eu)₉(acac)₁₆(μ₃-OH)₈(μ₄-O)(μ₄-OH)]·H₂O complex. These multifunctional nano-objects work as efficient photothermal nano-heaters able to provide macroscopic temperature rises remotely triggered by light irradiation at 808 nm (ΔT = 20.4 °C under irradiation for 3 min with a laser power of 1.83 W cm⁻²). Their specific heat capacity, the primary parameter influencing the heating properties of nanoparticles, was determined by using the photothermal properties and the measured heat capacity of PB nanoparticles, yielding a value of 1.13 ± 0.03 J g⁻¹ K⁻¹. This moderate value indicates that once heated, the nanoparticles can retain heat effectively, making them suitable for applications requiring sustained and controlled thermal effects. On the other hand, these multifunctional nanoparticles exhibit the characteristic temperature-dependent luminescence of Tb³⁺ and Eu³⁺ with improved Tb³⁺-to-Eu³⁺ energy transfer, making them efficient as luminescent ratiometric thermometers. These nanothermometers operate in the 20–80 °C range exhibiting a maximal relative thermal sensitivity of 0.75% °C⁻¹ at 20 °C.