On−Off Blinking and Multiple Bright States of Single Europium Ions in Eu3+:Y2O3 Nanocrystals

TLDR: In this paper, a pump-intensity dependent duty factor and quantum jumps between three well-defined luminescence intensity levels (bright states) from individual nanoparticles were observed, with a modulation rate that is dependent on pump-laser intensity.

Abstract: We show that continuously illuminated single europium ions incorporated in yttrium oxide (Eu3+:Y2O3) nanocrystals (5−15 nm diameter) undergo on−off blinking on a variable time scale ranging from hundreds of milliseconds to several seconds. We observe both a pump-intensity dependent “duty factor” (on-time as a percentage of total measurement time), and quantum jumps between at least three well-defined luminescence intensity levels (bright states) from individual nanoparticles. Interesting switching or oscillation between different bright levels was also observed with a modulation rate that is dependent on pump-laser intensity. These features of single-ion luminescence are not observed for larger particles with multiple chromophores. We propose that these effects derive from pump laser-induced fluctuations between different quasi-stable Eu3+ symmetry sites that effectively modulate the electric dipole transition moment.