Scanning near‐field optical microscopy using semiconductor nanocrystals as a local fluorescence and fluorescence resonance energy transfer source

Abstract

SummaryLocal fluorescence probes based on CdSe semiconductor nanocrystals were prepared and tested by recording scanning near-field optical microscopy (SNOM) images of calibration samples and fluorescence resonance energy transfer SNOM (FRET SNOM) images of acceptor dye molecules inhomogeneously deposited onto a glass substrate. Thousands of nanocrystals contribute to the signal when this probe is used as a local fluorescence source while only tens of those (the most apical) are involved in imaging for the FRET SNOM operation mode. The dip-coating method used to make the probe enables diminishing the number of active fluorescent nanocrystals easily. Prospects to realize FRET SNOM based on a single fluorescence centre using such an approach are briefly described.

Subwavelength-size local fluorescent sources based on color centers in LiF for scanning near-field optical microscopy

“…Experimental details are similar to those reported in Ref. [5,6]. Noticeable change in the fluorescence spectrum of 30-nm-thick LiF:F 2 layer after spin coating deposition of the dye monolayer did occur, and we attributed such a change to the FRET phenomenon.…”

“…Another advantage is the easier interpretation of the SNOM data because of the well-defined and controllable shape of the excitation source [2]. Local fluorescence probes based on dye molecules [3][4][5], semiconductor nanocrystals [6][7][8], and luminescent rare-earth ions [9] have been realized up to now. Using of luminescent defects (color centers) in dielectric crystals, such as, say, N-centers in diamond or F-aggregate centers in lithium fluoride, seems especially promising due to their excellent fluorescence yield, high photostability and relative ease to engineer the necessary probes.…”

Controlling molecular organization at the nanoscale for localized second harmonic generation

“…An interesting alternative consists in developing localized light source : to this end, different results recently appeared using so-called active tips i.e. tips which are not only used to scatter light but can directly produce light through the attachment of fluorescent nanoobjects [13] (single molecule [14], color centers rare-earth doped nanoparticles [15], or semi-conductor nanocrystals [16,17,18] …)…”

Probing light-matter interactions at the nanoscale with a deterministically positioned single quantum dot

“…Specifically, these artificial atoms can be used as nanoscale near-field probes for studying properties of nanophotonic 1-3 and plasmonic 4,5 structures for the purpose of understanding and engineering of quantum information processors 6 and nanoscale electronic circuits 7 . In addition, QDs play an important role in the study of Förster resonance energy transfer 8 and have broad range of applicability in biological sensing 9 .…”