TY  - INPR
A1  - Fersch, Daniel
A1  - Malý, Pavel
A1  - Rühe, Jessica
A1  - Lisinetskii, Victor
A1  - Hensen, Matthias
A1  - Würthner, Frank
A1  - Brixner, Tobias
T1  - Single-Molecule Ultrafast Fluorescence-Detected Pump–Probe Microscopy
N2  - We introduce fluorescence-detected pump–probe microscopy by combining a wavelength-tunable ultrafast laser with a confocal scanning fluorescence microscope, enabling access to the femtosecond time scale on the micrometer spatial scale. In addition, we obtain spectral information from Fourier transformation over excitation pulse-pair time delays. We demonstrate this new approach on a model system of a terrylene bisimide (TBI) dye embedded in a PMMA matrix and acquire the linear excitation spectrum as well as time-dependent pump–probe spectra simultaneously. We then push the technique towards single TBI molecules and analyze the statistical distribution of their excitation spectra. Furthermore, we demonstrate the ultrafast transient evolution of several individual molecules, highlighting their different behavior in contrast to the ensemble due to their individual local environment. By correlating the linear and nonlinear spectra, we assess the effect of the molecular environment on the excited-state energy.
KW  - Fluoreszenz
KW  - Ultrafast spectroscopy
KW  - Single-molecule microscopy
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-313485
ER  - 
TY  - INPR
A1  - Dietzsch, Julia
A1  - Jayachandran, Ajay
A1  - Mueller, Stefan
A1  - Höbartner, Claudia
A1  - Brixner, Tobias
T1  - Excitonic coupling of RNA-templated merocyanine dimer studied by higher-order transient absorption spectroscopy
T2  - Chemical Communications
N2  - We report the synthesis and spectroscopic analysis of RNA containing the barbituric acid merocyanine rBAM2 as a nucleobase surrogate. Incorporation into RNA strands by solid-phase synthesis leads to fluorescence enhancement compared to the free chromophore. In addition, linear absorption studies show the formation of an excitonically coupled H-type dimer in the hybridized duplex. Ultrafast third- and fifth-order transient absorption spectroscopy of this non-fluorescent dimer suggests immediate (sub-200 fs) exciton transfer and annihilation due to the proximity of the rBAM2 units.
KW  - Barbituric Acid Merocyanines
KW  - Nucleobase Surrogate Incorporation
KW  - Higher-order Transient Absorption Spectroscopy
KW  - rBAM2-labeled RNA strands
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-327772
ET  - submitted version
ER  - 
TY  - INPR
A1  - Lambert, Christoph
A1  - Völker, Sebastian F.
A1  - Koch, Federico
A1  - Schmiedel, Alexander
A1  - Holzapfel, Marco
A1  - Humeniuk, Alexander
A1  - Röhr, Merle I. S.
A1  - Mitric, Roland
A1  - Brixner, Tobias
T1  - Energy Transfer Between Squaraine Polymer Sections: From helix to zig-zag and All the Way Back
T2  - Journal of the American Chemical Society
N2  - Joint experimental and theoretical study of the absorption spectra of squaraine polymers in solution provide evidence that two different conformations are present in solution: a helix and a zig-zag structure. This unique situation allows investigating ultrafast energy transfer processes between different structural segments within a single polymer chain in solution. The understanding of the underlying dynamics is of fundamental importance for the development of novel materials for light-harvesting and optoelectronic applications. We combine here femtosecond transient absorption spectroscopy with time-resolved 2D electronic spectroscopy showing that ultrafast energy transfer within the squaraine polymer chains proceeds from initially excited helix segments to zig-zag segments or vice versa, depending on the solvent as well as on the excitation wavenumber. These observations contrast other conjugated polymers such as MEH-PPV where much slower intrachain energy transfer was reported. The reason for the very fast energy transfer in squaraine polymers is most likely a close matching of the density of states between donor and acceptor polymer segments because of very small reorganization energy in these cyanine-like chromophores.
KW  - energy transfer dynamics
KW  - squaraine polymer
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159607
UR  - http://dx.doi.org/10.1021/jacs.5b03644
N1  - This document is the unedited Author's version of a Submitted Work that war subsequently accepted for publication in Journal of the American Chemical Society, copyright American Chemical Society after peer review. To access the final edited and published work see doi:10.1021/jacs.5b03644.
ER  -