Luminescence dynamics

The advances in nanotechnology and synthesis methods have enabled nanomaterials to be produced in various shapes and structures. Coating of a luminescent layer activated by lanthanide ions on nanoparticles such as SiC>2 or AI2O3 is one of such approaches to develop new nanophosphors. In section 6, we review recent work on interesting spectroscopic features and luminescence dynamics of lanthanide ions in other novel low-dimensional nanostructures including core-shell, one-dimensional (ID) nanowires and nanotubes, two-dimensional (2D) nanofilms, hollow nanospheres, 2D nanosheet and nanodisk which have also attracted extensive attention. 

Although no quantum confinement should occur in the electronic energy level structure of lanthanides in nanoparticles because of the localized 4f electronic states, the optical spectrum and luminescence dynamics of an impurity ion in dielectric nanoparticles can be significantly modified through electron-phonon interaction. Confinement effects on electron-phonon interaction are primarily due to the effect that the phonon density of states (PDOS) in a nanocrystal is discrete and therefore the low-energy acoustic phonon modes are cut off. As a consequence of the PDOS modification, luminescence dynamics of optical centers in nanoparticles, particularly, the nonradiative relaxation of ions from the electronically excited states, are expected to behave differently from that in bulk materials. 

Following the introduction to size-dependent nanophenomena presented in the previous sections, we now focus our attention on the luminescence properties of lanthanide ions at additional sites or distorted structure existing in nanophases. Phenomena of prolonged luminescence lifetime, anomalous thermalization, upconversion luminescence, dynamics of long-range interaction with two-level-systems (TLS), and quantum efficiency are to be discussed. 

Note that the power-independent rate constant w etu (s" ) does not have the same units as Wexu cm ) in Eq. (10). Immediately following a short excitation pulse, the luminescence dynamics behave as described by Eq. (12) [22,23] ... 

Gryk W, Dujardin C, Joubert M-F, Ryba-Romanowski W, Malinowski M, Grinberg M (2006) Pressure effect on luminescence dynamics in Pr + 3 -doped LiNb03 and LiTa03 crystals. J Phys Cond Matter 18 117... 

Lin CC, Liu YP, Xiao ZR, Wang YK, Cheng BM, Liu RS (2014) All-in-one light-tunable borated phosphors with chemical and luminescence dynamical control resolution. ACS Appl Mater Interfaces 6 9160... 

S. Ivanova, F. Pelle, A. Tkachuk, M.-F. Joubert, Y. Guyot and V.P. Gapontzev, Upconversion luminescence dynamics of Er-doped fluoride crystals for optical converters, J. Lumin. 128,914 (2008). 

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