Upconverting Nanoparticles for Nanoscale Thermometry

Upconverting materials are capable of absorbing near-infrared light and converting it into short-wavelength luminescence. The efficiency of this remarkable effect is highly temperature dependent and thus can be used for temperature determination (thermometry) on a nanometer scale. All the upconverting materials discovered so far display several (mainly two) narrow emission bands, each of which has its own temperature dependence. The ratio of the intensity of two of these bands provides a referenced signal for optical sensing of temperature, for example inside cells. Cell fever: Lanthanoid-ion-doped upconverting nanoparticles (UCNPs) display a strongly temperature-dependent luminescence that can be used to sense temperature in sub-micrometer dimensions, for example in cells or nanofluidics. The picture showns how green- and red-emitting UCNPs can be used to measure the temperature in kidney cells. The intensity ratio of two of these bands provides a referenced signal. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.