Plasmon-Enhanced Energy Transfer for Improved Upconversion
of Infrared Radiation in Doped-Lanthanide Nanocrystals
- Publication date
- Publisher
Abstract
Upconversion of infrared radiation
into visible light has been
investigated for applications in photovoltaics and biological imaging.
However, low conversion efficiency due to small absorption cross-section
for infrared light (Yb<sup>3+</sup>), and slow rate of energy transfer
(to Er<sup>3+</sup> states) has prevented application of upconversion
photoluminescence (UPL) for diffuse sunlight or imaging tissue samples.
Here, we utilize resonant surface plasmon polaritons (SPP) waves to
enhance UPL in doped-lanthanide nanocrystals. Our analysis indicates
that SPP waves not only enhance the electromagnetic field, and hence
weak Purcell effect, but also increase the rate of resonant energy
transfer from Yb<sup>3+</sup> to Er<sup>3+</sup> ions by 6 fold. While
we do observe strong metal mediated quenching (14-fold) of green fluorescence
on flat metal surfaces, the nanostructured metal is resonant in the
infrared and hence enhances the nanocrystal UPL. This strong Coulombic effect on energy transfer can have
important implications for other fluorescent and excitonic systems
too