Upconversion thermometry: a new tool to measure the thermal resistance of nanoparticles

Abstract

The rapid evolution in luminescence thermometry in the last few years gradually shifted the research from the fabrication of more sensitive nanoarchitectures towards the use of the technique as a tool for thermal bioimaging and for the unveiling of properties of the thermometers themselves and of their local surroundings, for example to evaluate heat transport at unprecedented small scales. In this work, we demonstrated that KLu(WO4)2:Ho3+,Tm3+ nanoparticles are able to combine controllable heat release and upconversion thermometry permitting to estimate its thermal resistance (in air), a key parameter to model the heat transfer at the nanoscale.

Lanthanide‐Based Thermometers: At the Cutting‐Edge of Luminescence Thermometry

“…Introducing Ce 3+ in the core the authors can tune S m between 0.7 and 4.4% K −1 via the efficient cross relaxation processes between Ce 3+ and Ho 3+ ( Figure ) . Recently Savchuk et al reported KLuWO 4 :Tm 3+ /Ho 3+ NPs as tunable multifunctional heater‐thermometer nanoplatforms under 808 nm excitation. The intensity ratio is defined using the intensity of the Tm 3+ 3 F 2,3 → 3 H 6 line (at 696 nm) and that of Ho 3+ 5 S 2 , 5 F 4 → 5 I 7 (at 755 nm) one, with S m = 2.8% K −1 and δT = 0.2 K (at 300 K).…”

“…Early tumor detection becomes possible by transient thermometry using near‐infrared (NIR) emitting Ag 2 S nanocrystals . Examples of the later approach are the analysis of heat flux assessment in heater‐thermometer nanoplatforms, the estimation of the absorption coefficient and of the thermal diffusivity of tissues, the quantification of the instantaneous ballistic velocity of Brownian nanocrystals suspended in aqueous and organic solvents, the determination of the thermal conductivity of porous silica and titania nanostructures, and the measurement of the thermal resistance of NPs (in air) . Among these recent examples, the present manuscript considers essentially those based on Ln 3+ ions, being a follow up of the two books and the review papers published since 2015 on Ln 3+ ‐based luminescent thermometers .…”

Ratiometric upconversion nanothermometry with dual emission at the same wavelength decoded via a time-resolved technique

“…L uminescent nanothermometry has attracted considerable interest as a novel type of sub-micrometric thermal reading due to its strong temperature-dependent luminescence in nanosize [1][2][3][4][5] . Benefitting greatly from its high resolution, high sensitivity, and noninvasiveness, it is widely applied in biology [6][7][8][9][10] , thermodynamics [11][12][13][14][15][16] , and nanomedicine [17][18][19][20][21] . Luminescent thermal reading can provide temperature measurements in inflamed regions in vivo via contactless and noninvasive luminescence bioimaging 22,23 .…”

“…Upconversion luminescence (UCL) bioimaging can reduce auto-fluorescence from biological systems owing to its anti-Stokes process [27][28][29] . To date, several ratiometric upconversion luminescent nanothermometers, which are based on lanthanide doped upconversion nanoparticles 16,30 (UCNPs) or triplet-triplet annihilation 31 , have been applied to monitor temperature in small animals. Unfortunately, the thermal sensitive signals of these upconversion luminescent nanothermometers are still located in the visible region, which limit their detection depth due to high absorption and scattering which originate from complex tissues.…”

NIR‐II/III Luminescence Ratiometric Nanothermometry with Phonon‐Tuned Sensitivity

“…Lanthanide‐based luminescence intensity ratio (LIR) thermometry is promising for temperature evaluation in complex environments, which is absent from the problems caused by changes in probe concentrations and variation of light excitation and detection efficiency. Typically, lanthanide‐based LIR thermometry utilizes two thermal‐coupled energy levels in one lanthanide ion, or temperature‐dependent energy transfer processes between two lanthanide ions (e.g., Eu 3+ and Tb 3+ ions), presenting the empirical exponential or linear growth equation for temperature evaluation . This type of thermometers have superior photostability, narrow band emissions for precise LIR determination, and null autofluorescence in time‐gated detection .…”