Time-Resolved X-ray Absorption Spectroscopy in (Photo)Electrochemistry

This minireview aims at providing a complete survey concerning the use of X-ray absorption spectroscopy (XAS) for time-resolved studies of electrochemical and photoelectrochemical phenomena. We will see that time resolution can range from the femto-picosecond to the second (or more) scale and that this joins the valuable throughput typical of XAS, which allows for determining the oxidation state of the investigated element, together with its local structure. We will analyze four different techniques that use different approaches to exploit the in real time capabilities of XAS. These are quick-XAS, energy dispersive XAS, pump & probe XAS and fixed-energy X-ray absorption voltammetry. In the conclusions, we will analyze possible future perspectives for these techniques.

Excited state relaxation processes of H2-evolving Ru-Pd supramolecular photocatalysts containing a linear or non-linear bridge: a DFT and TDDFT study

In this study, the early-time excited state relaxation processes of bimetallic Ru-Pd supramolecular photocatalysts containing a linear 2,2':5',2''-terpyridine or a nonlinear 2,2':6',2''-terpyridine bridging ligand (BL) were investigated by density functional theory (DFT) and time-dependent DFT (TDDFT) approaches. The bridge based metal-to-ligand charge transfer triplet (³MLCT) state of the metal complex containing a linear bridging ligand was calculated to be the lowest energy triplet (T₁) state which is closely related to the photocatalytic H₂ production, while for that having a nonlinear bridging ligand, the T₁ state is a Ru metal-centered (MC) triplet (³MC_Ru) state that is short-lived and rapidly decays to the ground electronic state (S₀). Our simulation provides an alternative explanation for the smaller interligand electron transfer (ILET) rate in the Ru-Pd complex containing a linear bridge compared to the corresponding monometal Ru complex. Based on the calculation, we also suggest that the successive ³MLCT → ³MC_Ru → S₀ conversion is responsible for the inefficiency of the Ru-Pd complex containing nonlinear bridge as a photocatalyst for H₂ production. This study provides theoretical insights into the key steps of the photoinduced processes of the bimetallic H₂-evolving supramolecular photocatalyst.

Application of the boron center for the design of a covalently bonded closely spaced triad of porphyrin-fullerene mediated by dipyrromethane

Charge separation stabilization is achieved by placing porphyrin and C₆₀ at the two ends of central BODIPY.

Photochemistry of ruthenium(ii) complexes based on 1,4,5,8-tetraazaphenanthrene and 2,2′-bipyrazine: a comprehensive experimental and theoretical study

Comprehensive study of ruthenium complexes based on 2,2′-bipyrazine and 1,4,5,8-tetraazaphenanthrene, which can be used as photoreactive materials for biomedical applications.

Direct Experimental Evidence for Photoinduced Strong-Coupling Polarons in Organolead Halide Perovskite Nanoparticles

Echoing the roaring success of their bulk counterparts, nano-objects built from organolead halide perovskites (OLHP) present bright prospects for surpassing the performances of their conventional organic and inorganic analogues in photodriven technologies. Unraveling the photoinduced charge dynamics is essential for optimizing the optoelectronic functionalities. However, mapping the carrier-lattice interactions remains challenging, owing to their manifestations on multiple length scales and time scales. By correlating ultrafast time-resolved optical and X-ray absorption measurements, this work reveals the photoinduced formation of strong-coupling polarons in CH₃NH₃PbBr₃ nanoparticles. Such polarons originate from the self-trapping of electrons in the Coulombic field caused by the displaced inorganic nuclei and the oriented organic cations. The transient structural change detected at the Pb L₃ X-ray absorption edge is well-captured by a distortion with average bond elongation in the [PbBr₆]^2- motif. General implications for designing novel OLHP nanomaterials targeting the active utilization of these quasi-particles are outlined.