Photon upconverting nanoparticles for luminescent sensing of temperature

Abstract

Photon upconverting nanoparticles convert near-infrared into visible light (anti-Stokes emission), which strongly reduces the background of autofluorescence and light scattering in biological materials. Hexagonal NaYF(4) nanocrystals doped with Yb(3+) as the sensitizer and Er(3+)/Ho(3+)/Tm(3+) as the activator display at least two emission lines that respond differently to temperature changes. The ratio of the main emission line intensities enables a self-referenced optical readout of the temperature in the physiologically relevant range from 20 to 45 °C. Upconverting nanoparticles of the type NaYF(4):Yb, Er covered by an inactive shell of NaYF(4) are bright and allow for resolving temperature differences of less than 0.5 °C in the physiological range. The optical readout of this nanoparticle-based thermometer offers many options for imaging the two-dimensional distribution of temperature.

Upconversion NaYF4:Yb:Er nanoparticles co-doped with Gd3+ and Nd3+ for thermometry on the nanoscale

“…An in-depth investigation of the potential of UCNP as nanothermometer was carried out by Woleis et al using different lanthanide combination and capping agents. 15 Here, the best results were found for NaYF 4 ) ions UCNP can be used for magnet resonance imaging or with the appropriate functionalization for optical imaging or assay applications. [16][17][18] Apart from the excitation at l ex ¼ 976 nm Han et al report on UCNP with additional Nd 3+ doping which could be excited at l ex ¼ 800 nm.…”

Photonen aufkonvertierende Nanopartikel zur optischen Codierung und zum Multiplexing von Zellen, Biomolekülen und Mikrosphären

“…Darüber hinaus sind der Energietransfermechanismus und die Emissionsintensitäten der UCNPs abhängig von der Temperatur, was für die Entwicklung von Nanothermometern genutzt wurde. [61][62][63] Eine dritte Art von Schwankungen in der Lumineszenzintensität der UCNPs wird durch Oberflächeneffekte verursacht. [64] [66] Die Herstellung kleinerer UCNPs führt normalerweise zu verstärkten Lçscheffekten auf der Oberfläche, da das Volumen stärker mit dem Radius abnimmt als die Oberfläche.…”

“…Tatsächlich ist ihr inertes Verhalten in vielen Situationen hochwillkommen. Die einzigen Parameter, die die Lumineszenz der UCNPs direkt beeinflussen, sind die Temperatur, [62,63,193,194] mit einigen Einschränkungen der pH-Wert [139] und einige Schwermetallionen. [66] Die Detektion von nahezu jedem anderen intrazellulären Analyten erfordert, dass die Oberfläche der UCNPs mit einem analytspezifischen organischen Farbstoff ausgestattet wird, der z.…”

Rare earth based nanostructured materials: synthesis, functionalization, properties and bioimaging and biosensing applications

“…The temperature dependence of many of the lanthanides' photophysical properties, including the emission intensity and the excited-state lifetime or rise time, is exploited in these systems. In particular, the dependence of the fluorescence intensities from two emitting levels of lanthanides [332] has been exploited for monitoring temperature changes in different cell models such as HeLa cervical cancer cells [333] and human embryo kidney cells [334], which allows the investigation of how thermal processes develop at cellular level, e.g. enzymatic reactions, cellular death and other physiological processes.…”