Ultrafast proton-assisted tunneling through ZrO 2 in dye-sensitized SnO 2 -core/ZrO 2 -shell films
Exposing ZrO 2 to strong acid induces protonic defects that permit ultrafast electron transfer through at least 4 nm of ZrO 2 .
Chemistry↗
Engineering topics
Hedström, Svante
Publications and source records attributed to Hedström, Svante.
Thousandfold Enhancement of Photoreduction Lifetime in Re(bpy)(CO) 3 via Spin-Dependent Electron Transfer from a Perylenediimide Radical Anion Donor
Spin-dependent intramolecular electron transfer is revealed in the Re I (CO) 3 (py)(bpy-Ph)–perylenediimide radical anion (Re I -bpy–PDI –• ) dyad, a prototype model system for artificial photosynthesis. Quantum chemical calculations and ultrafast transient absorption spectroscopy experiments show that selective photoexcitation of Re I -bpy results in electron transfer from PDI –• to Re I -bpy, forming two distinct charge-shifted states. One is an overall doublet whose return to the ground state is spin-allowed. The other, high-spin quartet state, persists for 67 ns due to spin-forbidden back-electron transfer, constituting a more than thousandfold lifetime improvement compared to the low-spin state. Exploiting this spin dependency holds potential for artificial photosynthetic systems needing long-lived reduced states to perform multi-electron chemistry.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Robust resistive memory devices using solution-processable metal-coordinated azo aromatics
Non-volatile memories will play a decisive role in the next generation of digital technology. Flash memories are currently the key player in the field, yet they fail to meet the commercial demands of scalability and endurance. Resistive memory devices, and in particular memories based on low-cost, solution-processable and chemically tunable organic materials, are promising alternatives explored by the industry. However, to date, they have been lacking the performance and mechanistic understanding required for commercial translation. Here we report a resistive memory device based on a spin-coated active layer of a transition-metal complex, which shows high reproducibility (~350 devices), fast switching (≤30 ns), excellent endurance (~10 12 cycles), stability (>10 6 s) and scalability (down to ~60 nm 2 ). In situ Raman and ultraviolet–visible spectroscopy alongside spectroelectrochemistry and quantum chemical calculations demonstrate that the redox state of the ligands determines the switching states of the device whereas the counterions control the hysteresis. This insight may accelerate the technological deployment of organic resistive memories.
Goswami, Sreetosh↗
Stability and Effects of Subsurface Oxygen in Oxide-Derived Cu Catalyst for CO 2 Reduction
Here, oxide-derived copper (OD-Cu) catalysts are promising candidates for the electrochemical CO 2 reduction reaction (CO 2 RR) due to the enhanced selectivity toward ethylene over methane evolution, which has been linked to the presence of subsurface oxygen (O sb ). In this work, O sb is investigated with theoretical methods. Although O sb is unstable in slab models, it becomes stabilized within a “manually” reduced OD-Cu nanocube model which was calculated by self-consistent charge density functional tight binding (SCC-DFTB). The results obtained with SCC-DFTB for the full nanocube were confirmed with subcluster models extracted from the nanocube, calculated with both density functional theory (DFT) and SCC-DFTB. The higher stability of O sb in the nanocube is attributed to the disordered structure and greater flexibility. The adsorption strength of CO on Cu(100) is enhanced by O sb withdrawing electron density from the Cu atom, resulting in reduction of the σ-repulsion. Hence, the coverage of CO may be increased, facilitating its dimerization.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Linker Length-Dependent Electron-Injection Dynamics of Trimesitylporphyrins on SnO 2 Films
Electron-injection dynamics of dye-sensitized photoelectrochemical cells depend on the length of the linker connecting the molecular photosensitizer to the metal oxide electron acceptor. However, systematic studies of the effect of chromophore–oxide distance are scarce. In this work, we present the synthesis, characterization, spectroscopy, and computational modeling of electron-injection dynamics from free-base trimesitylporphyrins with varying linker lengths into tin(IV) oxide (SnO 2 ). In each system, the porphyrin core and metal oxide film remain the same while only the linker binding the porphyrin to the carboxylate anchor group is varied. A length range spanning 8.5–17.2 Å is studied by employing phenylene, biphenylene, terphenylene, and benzanilide groups as the linker. We find a clear correlation between linker length and injection rates, providing insights that will be exploited in the optimization of dye-sensitized photoelectrochemical cells.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗