Mapping plasmon-enhanced upconversion fluorescence of Er/Yb-doped nanocrystals near gold nanodisks

Abstract

Fluorescence enhancements near metallic nanostructures have been directly mapped with a single nanocrystal attached at the end of a tip.

TiO2 Nanocolumn Arrays for More Efficient and Stable Perovskite Solar Cells

“…measurements were performed by a homemade near-field optical microscope that uses a fluorescent nanocrystal as a near-field detector. 68,69 Excitation was performed with an internally modulated laser diode (l @ 650 nm, fmod = 320 Hz) in a transmission mode at normal incidence.…”

Direct imaging of fluorescence enhancement in the gap between two gold nanodisks

“…5), but it apparently comes from the lateral parts of the dimer. The fluorescence (and near-field) map for the touching dimer actually resembles that of a "big" lone disk 38 , and thus we can explain the disappearance of the fluorescence bright spot as caused by the presence of the conductive path between the two disks. Electrons do not oscillate anymore around each disk separately, they can go back and forth between the two disks, which shifts the resonance frequency of the system at another, larger, wavelength, far from the excitation source 28,50 .…”

“…Therefore, the nanocrystal has to be robust, durable, and should not present any evidence of photobleaching. Fluoride nanocrystals doped with Er 3+ and Yb 3+ ions nicely satisfy these conditions [38][39][40][41] . In this study, we use NaYF 4 :Er 3+ /Yb 3+ nanocrystals synthetized by hydrothermal route 42,43 .…”

“…This will be achieved by mapping the fluorescence intensity as a function of the position of the nanocrystal around the disks, for different separation distances between them. Although there are many experimental studies describing the influence of plasmonic structures on fluorescent molecules [19][20][21][22][23][24][25][26][27]37 , the direct mapping of the emission intensity or lifetime has only been achieved on simple structures like isolated metallic nanostructures 23,38 . For structures where coupling effects or interactions govern the optical response, many questions are still unanswered.…”

“…We characterized five structures of diameter 240 nm and separated, from edge to edge, by d = 385 nm, 195 nm, 95 nm, 55 nm and 0 nm respectively. The chosen diameter for each disk corresponds to that which has the largest local electromagnetic field intensity at the excitation wavelength 38 and the separation distances cover a wide range, from mid-field, where we expect a reduced (but not vanishing) influence of evanescent coupling, to near-field coupling and direct contact. The polarization of the incident light is parallel to the alignment of two nanodisks.…”