2 research outputs found
Probing the Hydrogen-Bonded Water Network at the Active Site of a Water Oxidation Catalyst: [Ru(bpy)(tpy)(H<sub>2</sub>O)]<sup>2+</sup>·(H<sub>2</sub>O)<sub>0–4</sub>
The infrared spectra
of gas-phase mass-selected [RuÂ(bpy)Â(tpy)Â(H<sub>2</sub>O)]<sup>2+</sup>·(H<sub>2</sub>O)<sub>0–4</sub> clusters (bpy = 2,2′-bipyridine;
tpy = 2,2′:6,2″-terpyridine)
in the OH stretching region are reported. These species are formed
by bringing the homogeneous water oxidation catalyst [RuÂ(bpy)Â(tpy)Â(H<sub>2</sub>O]<sup>2+</sup> from solution into the gas phase via electrospray
ionization (ESI) and reconstructing the water network at the active
site by condensing additional water onto the complex in a cryogenic
ion trap. Infrared predissociation spectroscopy is used to probe the
structure of these clusters via their distinctive OH stretch frequencies,
which are sensitive to the shape and strength of the local hydrogen-bonding
network. The analysis of the spectra, aided by electronic structure
calculations, highlights the formation of strong hydrogen bonds between
the aqua ligand and the solvating water molecules in the first solvation
shell. These interactions are found to propagate through the subsequent
solvation shells and lead to the stabilization of asymmetric solvation
motifs. Electronic structure calculations show that these strong hydrogen
bonds are promoted by charge transfer from the H atom of the aqua
ligand to the Ru–OH<sub>2</sub> bond
Nonmetal to Metal Transition and Ultrafast Charge Carrier Dynamics of Zn Clusters on p‑Si(100) by fs-XUV Photoemission Spectroscopy
Understanding the electronic structure
and charge carrier dynamics
of supported clusters is important due to their many potential applications
in photochemistry and catalysis. In this investigation, photoemission
spectroscopy, in conjunction with femtosecond extreme ultraviolet
(XUV) laser pulses, is used to investigate the electronic structure
and ultrafast charge carrier dynamics at a Si(100) surface decorated
with Zn clusters. Static photoemission spectroscopy is used to investigate
the changes in the electronic structure as the dimensionality of the
Zn is increased from small clusters composed of a very few atoms to
metallic Zn particles. Furthermore, femtosecond optical-pump XUV-probe
photoemission spectroscopy is employed to induce a charge transfer
from the p-Si(100) substrate to the Zn clusters and to measure in
real time the charge trapping at the Zn cluster as well as the subsequent
charge relaxation. The ultrafast charge carrier dynamics are also
investigated for small clusters and metallic Zn particles. Significant
transient charging of the Zn clusters after excitation of the Si(100)
substrate by 800 nm light is observed for Zn coverages greater than
0.12 ML Zn, which coincides with the formation of a Schottky barrier
at the interface between the Zn particle and the p-Si(100) substrate.
The transient signals show that the charge trapping time at the Zn
cluster varies with the cluster size, which is rationalized based
on the electronic structure of the cluster as well as the band energy
alignment at the Zn cluster–Si(100) junction