5 research outputs found
Synthesis of an AcceptorāDonorāAcceptor Multichromophore Consisting of Terrylene and Perylene Diimides for Multistep Energy Transfer Studies
Motivated by the results obtained
from the investigation of singletāsinglet
annihilation in a linear multichromophore comprising terrylene diimides
(TDI) and perylene diimide (PDI) in 2010, we report the detailed process
toward the successful synthesis of a TDIāPDIāTDI dyad.
Ineffective synthetic pathways, which were necessary for the understanding
of the step-by-step construction of the complex multichromophore,
are described, leading toward a universal synthetic plan for multicomponent
systems containing rylene diimides separated by rigid oligophenylene
spacers
Bio Serves Nano: Biological Light-Harvesting Complex as Energy Donor for Semiconductor Quantum Dots
Light-harvesting complex (LHCII) of the photosynthetic
apparatus
in plants is attached to type-II coreāshell CdTe/CdSe/ZnS nanocrystals
(quantum dots, QD) exhibiting an absorption band at 710 nm and carrying
a dihydrolipoic acid coating for water solubility. LHCII stays functional
upon binding to the QD surface and enhances the light utilization
of the QDs significantly, similar to its light-harvesting function
in photosynthesis. Electronic excitation energy transfer of about
50% efficiency is shown by donor (LHCII) fluorescence quenching as
well as sensitized acceptor (QD) emission and corroborated by time-resolved
fluorescence measurements. The energy transfer efficiency is commensurable
with the expected efficiency calculated according to FoĢrster
theory on the basis of the estimated donorāacceptor separation.
Light harvesting is particularly efficient in the red spectral domain
where QD absorption is relatively low. Excitation over the entire
visible spectrum is further improved by complementing the biological
pigments in LHCII with a dye attached to the apoprotein; the dye has
been chosen to absorb in the āgreen gapā of the LHCII
absorption spectrum and transfers its excitation energy ultimately
to QD. This is the first report of a biological light-harvesting complex
serving an inorganic semiconductor nanocrystal. Due to the charge
separation between the core and the shell in type-II QDs the presented
LHCIIāQD hybrid complexes are potentially interesting for sensitized
charge-transfer and photovoltaic applications
Single Semiconductor Nanocrystals under Compressive Stress: Reversible Tuning of the Emission Energy
The
photoluminescence of individual CdSe/CdS/ZnS core/shell nanocrystals
has been investigated under external forces. After mutual alignment
of a correlative atomic force and confocal microscope, individual
particles were colocalized and exposed to a series of force cycles
by using the tip of the AFM cantilever as a nanoscale piston. Thus,
force-dependent changes of photophysical properties could be tracked
on a single particle level. Remarkably, individual nanocrystals either
shifted to higher or to lower emission energies with no indications
of multiple emission lines under applied force. The direction and
magnitude of these reversible spectral shifts depend on the orientation
of nanocrystal axes relative to the external anisotropic force. Maximum
pressures derived from the applied forces within a simple contact-mechanical
model lie in the GPa range, comparable to values typically emerging
in diamond anvil cells. Average spectral shift parameters of ā3.5
meV/GPa and 3.0 meV/GPa are found for red- and blue-shifting species,
respectively. Our results clearly demonstrate that the emission energy
of single nanocrystals can be reversibly tuned over an appreciable
wavelength range without degradation of their performance which appears
as a promising feature with respect to tunable single photon sources
or the creation of coherently coupled particle dimers
Emergence of Coherence through Variation of Intermolecular Distances in a Series of Molecular Dimers
Quantum
coherences between electronically excited molecules are
a signature of entanglement and play an important role for energy
transport in molecular assemblies. Here we monitor and analyze for
a homologous series of molecular dimers embedded in a solid host the
emergence of coherence with decreasing intermolecular distance by
single-molecule spectroscopy and quantum chemistry. Coherent signatures
appear as an enhancement of the purely electronic transitions in the
dimers which is reflected by changes of fluorescence spectra and lifetimes.
Effects that destroy the coherence are the coupling to the surroundings
and to vibrational excitations. Complementary information is provided
by excitation spectra from which the electronic coupling strengths
were extracted and found to be in good agreement with calculated values.
By revealing various signatures of intermolecular coherence, our results
pave the way for the rational design of molecular systems with entangled
states
Near-Infrared Perylenecarboximide Fluorophores for Live-Cell Super-Resolution Imaging
Organic near-infrared
(NIR) photoblinking fluorophores are highly
desirable for live-cell super-resolution imaging based on single-molecule
localization microscopy (SMLM). Herein we introduce a novel small
chromophore, PMIP, through the fusion of perylenecarboximide
with 2,2-dimetheylpyrimidine. PMIP exhibits an emission
maximum at 732 nm with a high fluorescence quantum yield of 60% in
the wavelength range of 700ā1000 nm and excellent photoblinking
without any additives. With resorcinol-functionalized PMIP (PMIP-OH), NIR SMLM imaging of lysosomes is demonstrated
for the first time in living mammalian cells under physiological conditions.
Moreover, metabolically labeled nascent DNA is site-specifically detected
using azido-functionalized PMIP (PMIP-N3) via click chemistry, thereby enabling the super-resolution
imaging of nascent DNA in phosphate-buffered saline with a 9-fold
improvement in spatial resolution. These results indicate the potential
of PMIP-based NIR blinking fluorophores for biological
applications of SMLM