0000000000240878
AUTHOR
Th. Basché
Scanning near-field optical microscopy using semiconductor nanocrystals as a local fluorescence and fluorescence resonance energy transfer source
Local 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…
Single-molecule optical switching of terrylene in p-terphenyl
The controlled manipulation and switching of single atoms and molecules raise the prospect of ultra-high-density data storage. Switching by motion of a single atom has been reported1, and techniques of single-molecule optical detection and spectroscopy2 in the condensed phase have been refined to a degree that allows the modification of the absorption properties of a single chromophore3. Light-induced jumps in single-molecule excitation frequencies have been reported3,4,5, but in none of these cases could the process be controlled: the jumps varied from molecule to molecule, they were interrupted by spontaneous jumps, and the new excitation frequencies could not be identified unambiguously.…
Single molecule spectroscopy of multichromophoric assemblies
We have investigated multichromophoric assemblies composed of a variable number of chromophores by single molecule spectroscopy. Specific spectral signatures have allowed to distinguish at the single molecule level between molecular dimers representing strong and weak electronic dipole-dipole coupling. By using fluorescence excitation spectroscopy at low temperature, the sharp purely electronic zero-phonon lines of single chromophores within a single dendrimer containing four chromophores could be isolated in the frequency domain.
Chapter 2 Single molecule spectroscopy of multichromophoric dendrimers at room and liquid helium temperatures
Publisher Summary This chapter discusses the single molecule spectroscopy of multichromophoric dendrimers at room and liquid helium temperatures. Single molecule spectroscopy has become an important tool for the optical study of the electronic interactions of proximate chromophores as the electronic interactions can be studied without averaging over the properties of an intrinsically heterogeneous ensemble. Single perylenemonoimide (PMI) chromophores are selectively addressed in the frequency domain within spatially isolated multichromophoric dendrimers, which are dispersed in a polymer film. Although the chromophores are interacting, they still can be addressed separately. This feature in …
Investigation of molecular dimers by ensemble and single molecule spectroscopy
International audience; We have investigated molecular dimers with different electronic coupling strengths by bulk and single molecule spectroscopy. In one of the dimers the two monomers (perylene-monoimide) are directly connected via a single bond while in the other one they are separated by the benzil motif. The close proximity of the monomers in the first case gives rise to excitonic band splitting which is clearly observable in the bulk absorption spectra. For the benzil structure the electronic interactions are governed by Förster-type energy hopping between the monomers. Fluorescence intensity trajectories at the single molecule level show one-step and two-step bleaching behaviour whi…
Confocal microscopy of single molecules of the green fluorescent protein
Single molecule detection has been extended into life sciences by use of strongly fluorescent labels. The green fluorescent protein (GFP) as a self-fluorescent biomolecule has attracted considerable attention. Here, single molecules of the GFP-mutant Glu222Gln are immobilized in a polyvinylalcohol matrix and detected by confocal fluorescence microscopy. Although this mutant stabilizes one of both conformers of the wild-type GFP, the investigation of its fluorescence dynamics reveals strong signal fluctuations. This fluorescence behaviour is—at least partly—caused by reversible photochemical changes of the protein framework, that can relax into the fluorescent state on different timescales. …
Kommentar zu: H. Mustroph, S. Ernst “Das Franck-Condon-Prinzip”
Die Zeitschrift “Chemie in unserer Zeit” wendet sich an ein breites Leserspektrum. Sie will zuverlassig uber neue Entwicklungen in der Chemie und verwandten Gebieten berichten sowie komplexe Sachverhalte auch fur den Nichtfachmann verstandlich aufbereiten. Mit grosem Bedauern kommen wir jedoch zu der Einschatzung, dass der Beitrag “Wer kennt es noch? Das Franck-Condon-Prinzip” von H. Mustroph und S. Ernst (im Folgenden als Ref. 1 bezeichnet) nach unserem Ermessen diesem Anspruch nicht gerecht wird. Der Beitrag enthalt einige erhebliche fachliche Fehler sowie sachlich unbegrundete und zum Teil irrefuhrende Kritik an Lehrbuchinhalten und wissenschaftlichen Arbeiten. Wir sehen es daher geboten…
Terrylene in p-terphenyl: single-molecule experiments at room temperature
Abstract This paper reports on fluorescence microscopy and spectroscopy of single terrylene molecules embedded in p -terphenyl at room temperature. The basic photophysical parameters of this crystalline host/guest system such as photostability, single-molecule emission rates and the properties of dispersed fluorescence spectra are reported. The stability of the single-molecule signals allowed the direct observation of singlet–triplet quantum jumps at room temperature, by means of which the underlying intersystem crossing rates can be investigated. The results of earlier investigations at liquid-helium temperatures are reviewed briefly where appropriate. The properties of terrylene in p -ter…
Frequency selective excitation of single chromophores within shape-persistent multichromophoric dendrimers
Isolated multichromophoric dendrimers containing four perylenemonoimide chromophores were investigated in a confocal microscope which allowed imaging of the same set of dendrimers over a wide temperature range. Emission spectra at low temperature (2 K) reveal narrow zero-phonon lines although the electron-phonon coupling is not negligible. By using fluorescence excitation spectroscopy, the sharp purely electronic zero-phonon lines of single chromophores within a single multichromophoric unit could be isolated in the frequency domain. Selective excitation into a higher energy chromophoric site is followed by rapid directional energy transfer into the lowest energy site from which emission th…