Project

Discipline

time-resolved spectroscopy; pump-probe measurements; transient absorption; photoluminescence; electron transfer

Lead
In diesem Forschungsvorhaben geht es um die Untersuchung von photochemischen Prozessen, die auf einer Zeitskala von wenigen Milliardstel-Sekunden ablaufen. Solche Prozesse sind wichtig in der biologischen Photosynthese und deren Verständnis ist daher auch im Hinblick auf eine künstliche Umwandlung von Sonnenenergie in chemisch gespeicherte Energie bedeutsam.
Lay summary
Konkret geht es um lichtinduzierte Elektronentransfer- und um Energietransferprozesse. Das geförderte Gerät ermöglicht die Beobachtung von äusserst kurzlebigen Reaktionsprodukten, die nach Lichtanregung mit einem kurzen Laserpuls in verschiedenen chemischen Systemen entstehen. Dies beinhaltet sowohl rein künstliche Modellsysteme vom Typ „Donor-Brücke-Akzeptor“ wie auch natürliche Enzyme und Proteine, in denen photochemische Reaktionen ablaufen können. Es ist geplant, dass dieses Gerät von mindestens 5 verschiedenen Forschungsgruppen im Departement Chemie der Universität Basel benutzt wird, und zwar unter der Leitung der Gruppe von Prof. Oliver Wenger.

Direct link to Lay Summary

Last update: 10.11.2014

Number	Title	Start	Funding scheme

Many photophysical and photochemical processes which are relevant for light-to-chemical energy conversion occur on very rapid timescales. Time-resolved UV-Vis absorption spectroscopy has become an indispensable tool in modern photochemistry. Several ongoing Ph. D. theses and postdoctoral research projects in the main applicant’s group ask for a transient absorption spectrometer with picosecond time resolution and an appropriate laser source. Among these projects are for example the investigation of photoinduced multi-electron transfer reactions in order to spatially separate multiple electrons from multiple holes, which is of key importance for producing chemical fuels with sunlight as energy input (projects 1 and 2). Similarly, picosecond transient absorption spectrosocopy will permit mechanistic studies of photoinduced proton-coupled electron transfer (PCET) reactions which will greatly further our current fundamental understanding of this important class of reactions (project 3). The activation of small inert molecules such as H2O, CO2 or N2 will invariably rely on multi-electron, multi-proton chemistry hence the proposed photochemical studies are important in the greater context of solar energy conversion. In addition to the multi-electron transfer and PCET studies, the main applicant’s group aims to explore ultra-long-range (> 100 Å) triplet-triplet energy transfer reactions in suitably designed donor-bridge-acceptor molecules (project 4). This work is relevant for the funneling of excitation energy over great distances to a photochemical reaction center. Studies of controlling long-range electron transfer across organoboron “wires” by coordinating anions complement the portfolio of projects currently planned in the main applicant’s group (project 5).Among the planned projects with co-applicants are: (i) the investigation of photochemical hydrogen production in artificial metalloenzymes based on the biotin-streptavidin technology (with Prof. Thomas R. Ward); (ii) the exploration of the role of the potentially highly redox-active amino acid ergothioneine in peptides and proteins by studies of phototriggered long-range electron transfer (with Prof. Florian P. Seebeck); (iii) the exploration of the photophysics of copper(I) complexes in dye-sensitized solar cells (DSCs) and in light-emitting electrochemical cells (LECs) (with Profs. Edwin C. Constable, Catherine E. Housecroft)); and (iv) the investigation of solvent-mediated electron transfer with cyclophane-based donor-acceptor dyads (with Prof. Marcel Mayor).In each of the proposed projects there is a clear emphasis on understanding elementary reaction steps occurring after photoexcitation, and this experimental approach will ultimately permit the rational design of photochemically functional systems. Toward this end, transient absorption spectroscopy measurements with high temporal resolution (up to ca. 30 ps) are of vital importance. Funding for a transient absorption spectrometer with picosecond time resolution from Hamamatsu (TRASS system) and a picosecond Nd:YVO4/YAG laser from Ekspla (PL2251B-20-SH/TH/FH model) is therefore requested.