Plasmonic enhanced emissions from cubic NaYF4: Yb:Er/Tm nanophosphors

L. Sudheendra, Volkan Ortalan, Sanchita Dey, Nigel D. Browning, Ian M. Kennedy

Research output: Contribution to journalArticlepeer-review

115 Scopus citations


A metal shell was used in this study to provide significant enhancement of the up-converted emission from cubic NaYF4 nanoparticles, creating a valuable composite material for labeling in biology and other applications; use of the cubic form of the material obviates the need to undertake a high temperature transformation to the naturally more efficient hexagonal phase. The NaYF4 matrix contained ytterbium sensitizer and an Erbium (Er) or Thulium (Tm) activator. The particle sizes of the as-synthesized nanoparticles were in the range of 20-40 nm with a gold shell thickness of 4-8 nm. The gold shell was macroscopically amorphous. The synthesis method was based on a citrate chelation. In this approach, we exploited the ability of the citrate ion to act as a reductant and stabilizer. Confining the citrate ion reductant on the nanophosphor surface rather than in the solution was critical to the gold shell formation. The plasmonic shell enhanced the up-conversion emission of Tm from visible and near-infrared regions by up to a factor of 8, in addition to imparting a visible color arising from the plasmon absorption of the gold shell. The up-conversion enhancements observed with Tm and Er were different for similar gold coverages, with local crystal field changes as a possible route to enhance up-conversion emission from high symmetry structural hosts. These novel up-converting nanophosphor particles combine the phosphor and features of a gold shell, providing a unique platform for many biological imaging and labeling applications.

Original languageEnglish (US)
Pages (from-to)2987-2993
Number of pages7
JournalChemistry of Materials
Issue number11
StatePublished - Jun 14 2011


  • citrate method
  • Cubic-NaYF
  • gold coating
  • plasmonic enhancement
  • up-conversion emission
  • up-converting nanophosphor

ASJC Scopus subject areas

  • Materials Chemistry
  • Chemical Engineering(all)
  • Chemistry(all)


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