Probing transient photoinduced charge-transfer in Prussian Blue Analogues with time-resolved XANES and optical spectroscopy
Résumé
We study the transient electron transfer process in CsCoFe and RbMnFe Prussian Blue Analogues (PBA), by time-resolved X-ray Absorption Near Edge Structure (XANES) and by time-resolved optical spectroscopy. We performed time-resolved studies on CsCoFe nanocrystals dispersed in solution. The XANES results obtained at room temperature clearly evidence the Co III (LS)Fe II →Co II (HS)Fe III electron transfer between the metal centers, through the opposite spectral shifts at the Fe and Co edges. We also studied the Mn III (LS)Fe II →Mn II (HS)Fe III process in RbMnFe powder sample, at thermal equilibrium as well and under laser excitation. Optical spectroscopy reveals that the process occurs on the picosecond timescale, as already reported by Raman spectroscopy and that the lifetime of the photoinduced charge-transfer states is in the 1-10 µs range, depending on the sample and on temperature.
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