Laser refrigeration of hydrothermal nanocrystals in physiological media

Abstract

Coherent laser radiation has enabled many scientific and technological breakthroughs including Bose-Einstein condensates, ultrafast spectroscopy, superresolution optical microscopy, photothermal therapy, and long-distance telecommunications. However, it has remained a challenge to refrigerate liquid media (including physiological buffers) during laser illumination due to significant background solvent absorption and the rapid (∼ps) nonradiative vibrational relaxation of molecular electronic excited states. Here we demonstrate that single-beam laser trapping can be used to induce and quantify the local refrigeration of physiological media by >10°C following the emission of photoluminescence from upconverting yttrium lithium fluoride (YLF) nanocrystals. A simple, low-cost hydrothermal approach is used to synthesize polycrystalline particles with sizes ranging from <200 nm to >1 μm.

Impact of Lanthanide Nanomaterials on Photonic Devices and Smart Applications

“…The applicability of doped LiYF 4 nanocrystals to laser cooling has been recently demonstrated. In 2015, Roder et al realized laser refrigeration of LiYF 4 :Yb 3+ nanocrystals in D 2 O media . This achievement was gained benefiting from a home‐built laser trapping system ( Figure ).…”

“…The particle's temperature (Tp) and local temperature profile is then extracted using cold Brownian motion analysis. Reproduced with permission . Copyright 2012, Highwire Press PNAS.…”

Low temperature micro Raman and laser induced upconversion and downconversion spectra of europium doped silver tungstate Ag2−3xEuxWO4 nanorods

“…The influence of electron beam irradiation on structural and optical properties of this material has also been investigated [39]. A further interesting potential future application is in the field of laser refrigeration of nanocrystals [40,41].…”

Brownian Thermometry Beyond Equilibrium

“…The heat emanating from a hot Brownian particle spreads quickly through the fluid, establishing a comoving stationary temperature gradient (in the sense of a spatially varying local equilibrium) around the relatively slowly moving particle. Colloidal particles can also persistently be cooled relative to the surrounding solvent, although this is experimentally much more challenging . But theoretically, it just amounts to a sign change, so that such cold Brownian motion is implicitly included in our discussion.…”