Enhancement of the upconversion radiation in Y2O3:Er3+ nanocrystals by codoping with Li+ ions

Abstract

We report on an innovative route to increase the upconversion (UC) green radiation by two orders of magnitude in Y2O3:Er3+ nanocrystals through tailoring Er3+ ions’ local environment with Li+ ions under diode laser excitation of 970nm. Theoretical investigations based on the steady-state rate equations indicate that such enhancement arises from a combining effect of the tailored lifetime of the intermediate I11∕24(Er) state, the suppressed cross relaxation H11∕22(Er)+I15∕24(Er)→I9∕24(Er)+I13∕24(Er) process, and the enlarged nanocrystal size induced by the Li+ ions. The proposed route here may constitute a promising step to solve the low efficiency problem in UC materials.

A General Strategy to Enhance Upconversion luminescence in Rare-Earth-Ion-Doped Oxide Nanocrystals

“…The Li + ions around rare-earth ions in the lattice, particularly that occupy the interstitial cites, can impose a columbic field on rare earth ions, which thereby can modify the local environment to increase the UCL. Based on this hypothesis, we have demonstrated that the UCL from Y 2 O 3 :Er 3+ nanocrystals can be significantly increased via codoping with Li + ions (Chen et al, 2008a). Bai et al (2008) reported on a similar observation in parallel.…”

Investigation of up-conversion luminescence properties of RE/Yb co-doped Y2O3 transparent ceramic (RE=Er, Ho, Pr, and Tm)

“…Host materials with low phonon energy can reduce nonradiative loss due to the multiphonon relaxation and thus realize efficient up-conversion luminescence [3,4]. Although various materials, including crystal, glass and nanocrystalse have been investigated [5][6][7], relatively little research has been done on up-conversion luminescence properties of RE doped transparent ceramic, which not only has numerous advantages over single crystal and glass [8], but can also be used in devices (such as lasers and converters) more conveniently. Y 2 O 3 transparent ceramic has received great attention for its potential application in IR windows, domes and lasers [9,10].…”

Fluorescence diffuse optical tomography using upconverting nanoparticles

“…The use of upconverting nanoparticles in deep diffuse tissue imaging has, for some time, been limited by the low quantum efficiency. However, recent advances in technology have greatly enhanced the quantum efficiency of the nanoparticles, 10,11 which have enabled them to be imaged in deep diffuse materials under conservative excitation intensities. 12,13 All work concerning nanoparticles for biomedical applications on the macroscopic scale to date has been focused on imaging only.…”