TY  - JOUR
A1  - Bastian, Philipp U.
A1  - Robel, Nathalie
A1  - Schmidt, Peter
A1  - Schrumpf, Tim
A1  - Günter, Christina
A1  - Roddatis, Vladimir
A1  - Kumke, Michael U.
T1  - Resonance energy transfer to track the motion of lanthanide ions
BT  - what drives the intermixing in core-shell upconverting nanoparticles?
JF  - Biosensors : open access journal
N2  - The imagination of clearly separated core-shell structures is already outdated by the fact, that the nanoparticle core-shell structures remain in terms of efficiency behind their respective bulk material due to intermixing between core and shell dopant ions. In order to optimize the photoluminescence of core-shell UCNP the intermixing should be as small as possible and therefore, key parameters of this process need to be identified. In the present work the Ln(III) ion migration in the host lattices NaYF4 and NaGdF4 was monitored. These investigations have been performed by laser spectroscopy with help of lanthanide resonance energy transfer (LRET) between Eu(III) as donor and Pr(III) or Nd(III) as acceptor. The LRET is evaluated based on the Forster theory. The findings corroborate the literature and point out the migration of ions in the host lattices. Based on the introduced LRET model, the acceptor concentration in the surrounding of one donor depends clearly on the design of the applied core-shell-shell nanoparticles. In general, thinner intermediate insulating shells lead to higher acceptor concentration, stronger quenching of the Eu(III) donor and subsequently stronger sensitization of the Pr(III) or the Nd(III) acceptors. The choice of the host lattice as well as of the synthesis temperature are parameters to be considered for the intermixing process.
KW  - upconversion nanoparticles
KW  - lanthanoid migration
KW  - lanthanides
KW  - core-shell
KW  - energy transfer
Y1  - 2021
U6  - https://doi.org/10.3390/bios11120515
SN  - 2079-6374
VL  - 11
IS  - 12
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Goetze, Jan P.
A1  - Kröner, Dominik
A1  - Banerjee, Shiladitya
A1  - Karasulu, Bora
A1  - Thiel, Walter
T1  - Carotenoids as a shortcut for chlorophyll Soret-to-Q band energy flow
JF  - ChemPhysChem : a European journal of chemical physics and physical chemistry
N2  - It is proposed that xanthophylls, and carotenoids in general, may assist in energy transfer from the chlorophyll Soret band to the Q band. Ground-state (1A(g)) and excited-state (1B(u)) optimizations of violaxanthin (Vx) and zeaxanthin (Zx) are performed in an environment mimicking the light-harvesting complex II (LHCII), including the closest chlorophyll b molecule (Chl). Time-dependent density functional theory (TD-DFT, CAM-B3LYP functional) is used in combination with a semi-empirical description to obtain the excited-state geometries, supported by additional DFT/multireference configuration interaction calculations, with and without point charges representing LHCII. In the ground state, Vx and Zx show similar properties. At the 1B(u) minimum, the energy of the Zx 1Bu state is below the Chl Q band, in contrast to Vx. Both Vx and Zx may act as acceptors of Soret-state energy; transfer to the Q band seems to be favored for Vx. These findings suggest that carotenoids may generally mediate Soret-to-Q energy flow in LHCII.
KW  - carotenoids
KW  - chlorophyll
KW  - density functional calculations
KW  - energy transfer
KW  - xanthophylls
Y1  - 2014
U6  - https://doi.org/10.1002/cphc.201402233
SN  - 1439-4235
SN  - 1439-7641
VL  - 15
IS  - 15
SP  - 3391
EP  - 3400
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
T1  - Determination of Pd2+ by fluorescence enhancement caused by an off-switching of an energy- and an electron transfer
JF  - ChemistrySelect
N2  - In this paper, we introduce a fluorescent dye 1, which is able to detect selectively Pd2+ by a clear fluorescence enhancement (FE) in THF. In the presence of eight Pd2+ equivalents, we observed a fluorescence enhancement factor (FEF) of 28.3. The high Pd2+ induced FEF can be explained by an off switching of multiple quenching processes within 1 by Pd2+. In the free dye 1 a photoinduced electron transfer (PET) and energy transfer (ET) takes place and quenches the anthracenic fluorescence. The coordination of eight Pd2+ units by the alkylthio-substituted porphyrazine receptor suppresses the PET and ET quenching process and the anthracenic fluorescence is switched on.
KW  - Palladium ion
KW  - electron transfer
KW  - energy transfer
KW  - fluorescence
KW  - porphyrazine
Y1  - 2021
U6  - https://doi.org/10.1002/slct.202003975
SN  - 2365-6549
VL  - 6
IS  - 3
SP  - 318
EP  - 322
PB  - Wiley-VCH
CY  - Weinheim
ER  -