Excitation Laser Power and Temperature-Dependent Luminescence of Optically Trapped Upconversion Particles

Suresh Karmegam, Monisha Kolikkaje, Aseefhali Bankapur, Sajan D. George

Research output: Contribution to journalArticlepeer-review

Abstract

The routinely adopted ensemble luminescence spectroscopy of rare-earth-ion-doped upconversion micro-/nanoparticles does not provide insights into the role of shell passivation and plasmonic particle incorporation at a single-particle level. Herein, we compare the results of silica shell formation as well as further incorporation of plasmonic nanoparticles onto the green 1 (2H11/2 to 4I15/2 transition, λ─520 nm), green 2 (4S3/2 to 4I15/2, transition, λ─540 nm), and red (4F9/2 to 4I15/2 transition) upconversion luminescence of an optically trapped single upconversion particle. Analysis of the results at a single upconversion particle level illustrates that the core-shell particle exhibits a higher intensity for green as well as red emission, and the effect is further pronounced with attachment of plasmonic nanoparticles (NPs) onto the SiO2 shell. Trapping laser power-dependent studies of an optically trapped particle show a linear increasing behavior for green 1, green 2, and red emissions with a slope value near 1. On the other hand, laser power-dependent studies using the Yb resonant 980 nm laser with a laser power that is 2 orders of magnitude less than the trapping laser show two slope values (changing from less than 1 to more than 1) for the double-logarithmic plot of luminescence of the upconversion microparticle (UCMP) and UCMP@SiO2 trapped particles, whereas the signal intensity saturates with a single slope value for a UCMP@SiO2@Au particle. The temperature-dependent luminescence of the thermally coupled intensity ratio of emission green 1 (520 nm) and green 2 (540 nm) can be applied as a temperature sensor. The thermal sensitivity measurements within the biologically relevant temperature range (298-333 K), using optically trapped particles, reveal distinctions in thermal sensitivity among UCMP, UCMP@SiO2, and UCMP@SiO2@Au. The results from the present study can find applications in bioimaging, single-cell studies, optical thermometers, photothermal converters, etc.

Original languageEnglish
Pages (from-to)20385-20397
Number of pages13
JournalJournal of Physical Chemistry C
Volume127
Issue number41
DOIs
Publication statusPublished - 19-10-2023

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • General Energy
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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