Thermal enhancement of upconversion emission in nanocrystals: a comprehensive summary

Abstract

Luminescence thermal stability is a major figure of merit of lanthanide-doped nanoparticles playing an essential role in determining their potential applications in advanced optics. Unfortunately, considering the intensification of multiple...

Evaluation of relative beam–profile-compensated quantum yield of upconverting nanoparticles over a wide dynamic range of power densities

“…However, currently, there are no available commercial systems able to tackle all the important parameters shown to affect the UCNPs' QY (e.g. excitation beam profile, scattering, and temperature [21][22][23] ). Several groups have measured the QY absolutely using integrating spheres, [24][25][26] and other groups have performed relative measurements using a material with known QY as a reference.…”

Controlling the thermal switching in upconverting nanoparticles through surface chemistry

“…The important role of water adsorption on the quenching of upconversion luminescence was demonstrated in many recent reports. 10,11,25 The adsorbed moisture provides non-radiative relaxation pathways for the populated excited levels of the lanthanide ions by transferring their energy to the stretching vibration of water molecules (∼3500 cm −1 ). 27 Vibrational overtones of OH-stretching were also pointed out for non-radiative relaxation.…”

“…10 Based on carefully designed experiments and structural characterization by thermogravimetry (TGA) and Fourier-transform infrared spectroscopy (FTIR) the authors demonstrated that the intensity variations could be ascribed to the desorption of surface moisture at high temperatures (470 K), finding a 0.5% weight loss or gain on heating and cooling, respectively. Nevertheless, despite the extensive work on the subject, reviewed in a series of recent papers, [11][12][13] the real-time monitoring of the emissions during heating-cooling cycles has been disregarded. Only recently, Li and co-workers have briefly compared the thermally dependent UCL of oleic acid capped and uncapped UCNPs.…”

Inflection in size-dependence of thermally enhanced up-conversion luminescence of UCNPs

“…5 On the other hand, UCNPs suffer from the significant size-dependent luminescence efficiency decrease, 6 which compromises the functionality of UCNPs. Fortunately, the unique anomalous luminescence thermal enhancement recently discovered in UCNPs has been found to be size-dependent as well, 7–9 which initials great opportunities for applications such as optical thermal sensing and anti-counterfeiting. 10–15…”