6 research outputs found
Photoinduced Asymmetric Charge Trapping in a Symmetric Tetraazapyrene-Fused Bis(tetrathiafulvalene) Conjugate
Unveiling the origin of photo-induced enhancement of oxidation catalysis at Mo(VI) centres of Ru(II)–Mo(VI) dyads
Photo-induced oxidation-enhancement in biomimetic bridged Ru(II)–Mo(VI) photo-catalyst is unexpectedly photo-activated in ps timescales. One-photon absorption generates an excited state where both photo-oxidized and photo-reduced catalytic centres are activated simultaneously and independently
Two-dimensional ultrafast transient absorption spectrograph covering deep-ultraviolet to visible spectral region optimized for biomolecules
We report on the implementation of a multi-kHz single-shot referenced non-coherent two-dimensional UV spectrograph based on conventional pump-probe geometry. It has the capability to cover a broad spectral region in excitation from 270-to-380 nm and in the detection from 270-to-390 nm and 320-to-720 nm. Other setups features are: an unprecedented time resolution of 33 fs (standard deviation); signals are photometrically corrected; a single shot noise of <1 mOD. It has the capability to operate with sample volumes as small as few ÎĽl which is an accomplishment in studying biological or biomimetic systems. To show its performances and potentials, we report two preliminary studies on the photophysics of phenanthrenes hosted in a multichromophoric antenna system and of aromatic amino acids in a blue-copper azurin
Energy and charge transfer dynamics in DNA based light harvesting antennae
DNA can serve as a versatile scaffold for chromophore assemblies. For example, light-harvesting
antennae have been realized by incorporating phenanthrene and pyrene building blocks into DNA
strands. It was shown that by exciting at 320 nm (absorption of phenanthrene), an emission at
450 nm is observed which corresponds to a phenanthrene-pyrene exciplex. The more
phenanthrenes are added into the DNA duplex, the higher is the fluorescence intensity with no
significant change in quantum yield. This shows that phenanthrene acts as a donor and efficiently
transfers the excitation energy to the pyrene. Up to now, the mechanism of this energy transfer
and exciplex formation is not known. Therefore, we first aim at studying the photo-cycle of such
DNA assemblies through transient absorption spectroscopy. Based on the results, we will explore
ways to manipulate the energy transfer by application of intense THz fields. Ground as well as
excited state Stark effect dynamics will be investigated