时间分辨光谱在光催化和光反应动力学中的应用.pptxVIP

时间分辨光谱;Spectroscopy on the fs to ps time scale;Spectroscopy on the ns to μs time scale;Time resolved spectroscopy in photocatalysis UV/Vis absorption spectroscopy: More than just ε!;Negative solvatochromism of eosin Y (2′,4′,5′,7′-tetrabromo-fluorescin-dianion, left) and positive solvatochromism of riboflavin tetraacetate (right). The empiric values of the polarity of the solvents on the Reichardt scale are 1.00 for H2O, 0.65 for ethanol (EtOH), 0.46 for acetonitrile (MeCN), and 0.44 for dimethyl sulfoxide (DMSO) ;With regards to the investigation of photocatalytic processes, especially the following questions are of specific interest:– Which are the intermediate steps of the photocatalytic reaction?– Is the catalytic reaction singlet or triplet chemistry?– How does diffusion contribute to the reaction dynamics?– Are intramolecular charge transfer processes involved?– Are catalyst-substrate-complexes formed and which impact has the complex formation on the electronic properties of a molecule?;16.2 Time-Resolved spectroscopic methods from fs to μs toelucidate photocatalytic processes;UV/Vis absorption and fluorescence spectra of riboflavin tetraacetate (left). Difference spectrum of the S1 state of riboflavin tetraacetate (bottom) 1?ps after excitation at λ?=?480?nm.;Rate models and the determination of the species associated spectra of the intermediate states;Optical absorption spectra of ground state (a), excited singlet state (b) and lowest triplet state (c) of an example chromophore. Since the spectra ε(λ) describe the wavelength dependentabsorption properties of each state they are named species associates spectra (SAS).;Jablonski diagram of the example chromophore;Jablonski diagram of the reductive quenching of the S1 state of riboflavin tetraacetate(RFTA). The rate 1kET is controlled by diffusion of RFTA and methoxybenzyl alcohol (MBA).;Exponential fit applied to the transient signal of the stimulated emission. The main time range