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.

Non-contact thermometry is essential in biomedical studies requiring thermal sensing and imaging with high thermal and spatial resolutions. In this work, we report the potential use of Er:Yb:NaYF4 and Er:Yb:NaY2F5O up-conversion nanoparticles as thermal sensors by means of lifetime based luminescent thermometry. We demonstrate how Er:Yb:NaY2F5O nanocrystals present a higher thermal sensitivity than the Er:Yb:NaYF4 ones and that their lifetime thermal coefficient is comparable to those corresponding to other nano-sized luminescent systems already used for high resolution lifetime fluorescence thermal sensing. We evaluate the potential use of Er:Yb:NaY2F5O nanoparticles as lifetime based thermal probes by providing the first experimental evidence on sub-tissue lifetime fluorescence thermal sensing by using up-conversion nanoparticles in an ex vivo experiment.

The development of lanthanide doped non-contact luminescent nanothermometers with accuracy, efficiency and as fast diagnostic tools attributed to their versatility, stability and narrow emission band profiles, have spurred the replacement...

Stable and self-starting mode-locking of a Tm:KLu(WO(4))(2) crystal laser is demonstrated using a transmission-type single-walled carbon nanotube (SWCNT) based saturable absorber (SA). These experiments in the 2 microm regime utilize the E11 transition of the SWCNTs for nonlinear saturable absorption. The recovery time of the SWCNT-SA is measured by pump-probe measurements as approximately 1.2 ps. The mode-locked laser delivers approximately 10 ps pulses near 1.95 microm with a maximum output power of up to 240 mW at 126 MHz repetition rate.

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We studied the temperature-dependent luminescence of GdVO4 nanoparticles co-doped with Er(3+) (1 mol %) and Yb(3+) (20 mol %) and determined their thermal sensing properties through the fluorescence intensity ratio (FIR) technique. We also analyzed how a silica coating, in a core-shell structure, affects the temperature sensing properties of this material. Spectra were recorded in the range of biological temperatures (298-343 K). The absolute sensitivity for temperature determination calculated for the core-shell nanoparticles is double the one calculated for bare nanoparticles, achieving a thermal resolution of 0.4 K. Moreover, silica-coated nanoparticles show good dispersibility in different solvents, such as water, DMSO, and methanol. Also, they show good luminescence stability without interactions with solvent molecules. Furthermore, we also observed that the silica coating shell prevents progressive heating of the nanoparticles during prolonged excitation periods with the 980 nm laser, preventing effects on their thermometric applications.

A thorough study of the RbTiOPO4 (RTP) crystallization in its self-flux and WO3-containing fluxes (10, 20, and 30 mol % WO3) has been performed. The composition regions and isotherms of crystallization were obtained, and most of the crystallized neighboring phases were identified. Afterward, the possibilities of doping and codoping RTP crystals with Er3+ and Nb5+ were studied. Adding Nb2O5 substituting TiO2 in the solution increases the distribution coefficient of Er3+ but changes the crystal morphology toward thin plates significantly. This means it is difficult to grow crystals of sufficient quality and size for research and applications. To optimize the crystal growth process, the conditions for growing doped and codoped RTP single crystals with Er3+ and Nb3+ by the top seeded solution growth technique (TSSG) were studied. For crystal growth from self-flux, stirring the solution with an immersed platinum turbine significantly increased the efficiency of the crystal growth process. These conditions allow achieving 0.65 × 1020 atom·cm-3 as an Er3+ dopant concentration in the crystal. The Judd−Ofelt parameters for Er3+ in RTP:Nb determined from the 300 K optical absorption spectra are Ω2 = 5.99 × 10-20, Ω4 = 0.54 × 10-20, and Ω6 = 0.37 × 10-20 cm2. Finally, the second harmonic generation (SHG) efficiency of RTP:Nb single crystals increased as the concentration of Nb increased up to a 4 atom % of Ti4+ substitution, after which the SHG efficiency decreased.

A luminescent thermometer changing from blue to red as temperature increases and based on Yb3+,Tm3+:GdVO4@SiO2 nanoparticles excited at 980 nm is presented.