Joining time-resolved thermometry and magnetic-induced heating in a single nanoparticle unveils intriguing thermal properties

Whereas efficient and sensitive nanoheaters and nanothermometers are demanding tools in modern bio- and nanomedicine, joining both features in a single nanoparticle still remains a real challenge, despite the recent progress achieved, most of it within the last year. Here we demonstrate a successful realization of this challenge. The heating is magnetically induced, the temperature readout is optical, and the ratiometric thermometric probes are dual-emissive Eu3+/Tb3+ lanthanide complexes. The low thermometer heat capacitance (0.021·K-1) and heater/thermometer resistance (1 K·W-1), the high temperature sensitivity (5.8%·K-1 at 296 K) and uncertainty (0.5 K), the physiological working temperature range (295-315 K), the readout reproducibility (>99.5%), and the fast time response (0.250 s) make the heater/thermometer nanoplatform proposed here unique. Cells were incubated with the nanoparticles, and fluorescence microscopy permits the mapping of the intracellular local temperature using the pixel-by-pixel ratio of the Eu3+/Tb3+ intensities. Time-resolved thermometry under an ac magnetic field evidences the failure of using macroscopic thermal parameters to describe heat diffusion at the nanoscale.This work was partially supported by the Spanish Ministry of Science and Innovation (MAT2011-259911) and in part developed in the scope of the project CICECO-Aveiro Institute of Materials (ref. FCT UID/CTM/50011/2013), financed by Portuguese funds through the FCT/MEC (RECI-CTM-CER-0336-2012, EXPL-CTM-NAN-0295-2012) and when applicable cofinanced by FEDER under the PT2020 Partnership Agreement. C.D.S.B. (SFRH/BPD/89003/2012) and N.J.O.S. acknowledge FCT for a postdoctoral grant and an IF 2013 contract, respectively. R.B. thanks ICMA-CSIC for a JAE-predoc grant.Peer Reviewe