148 research outputs found
Solid-state photochemistry of molecular photo-switchable species:the role of photocrystallographic techniques
Over the last 30 years, the single-crystal photocrystallographic technique has been developed to determine the three-dimensional crystal and molecular structures of metastable species which have been generated in the crystal photochemically. Transition-metal complexes that have been investigated using this methodology include complexes that contain nitrosyl, dinitrogen, sulfur dioxide and nitrite ligands, all of which form new linkage isomers in the solid state when photoactivated by light of the appropriate wavelength. Both steric and electronic factors determine the level of the conversion from the ground-state structure to the metastable isomeric structure, and both the `reaction cavity' size and the nature of the intermolecular interactions are shown to be among the key factors that influence the percentage conversion
Giving electrons a ride: nanomechanical electron shuttles
Nanomechanical shuttles transferring small groups of electrons or even
individual electrons from one electrode to another offer a novel approach to
the problem of controlled charge transport. Here, we report the fabrication of
shuttle-junctions consisting of a 20 nm diameter gold nanoparticle embedded
within the gap between two gold electrodes. The nanoparticle is attached to the
electrodes through a monolayer of flexible organic molecules which play the
role of springs so that when a sufficient voltage bias is applied, then
nanoparticle starts to oscillate transferring electrons from one electrode to
the other. Current-voltage characteristics for the fabricated devices have been
measured and compared with the results of our computer simulations.Comment: 11 pages, 4 figure
Expanding the tools available for direct ortho cupration - Targeting lithium phosphidocuprates
Effect of Benzoic Acids on Barite and Calcite Precipitation
The effect of various benzoic acids on the precipitation of barite (BaSO4) and calcite (CaCO3) was investigated. The acids varied in the number of carboxylate groups, from dibenzoic acids (phthalic, isophthalic, and terephthalic) through to the hexabenzoic acid (mellitic acid). It was found that the stereochemistry of the dibenzoic acids was important, as was the pH of the solution (trimesic acid was used as a test case and showed that greatest inhibition was achieved with all carboxylate groups deprotonated). Interestingly, for both the calcite and barite systems, mellitic acid was found to be both a potent inhibitor and a significant crystal growth modifier. In the case of barite, the presence of mellitic acid produced nanoparticles that agglomerated. The nanoparticles were found to be 20 nm in size from X-ray diffraction (XRD) line width analysis and 20-50 nm from transmission electron microscopy (TEM). Humic acid was also tested and found to form bundled fibers of barium sulfate
Use of vapochromic crystals to measure the concentration of a gaseous throughflow at the solid-fluid interface
Azetidinium lead iodide for perovskite solar cells
Azetidinium lead iodide has been prepared for the first time; it is a stable, bright orange material that can act as the absorber layer in solar cells.</p
Steady-state and pseudo-steady-state photocrystallographic studies on linkage isomers of [Ni(Et<sub>4</sub>dien)(η<sup>2</sup>-O,ON)(η<sup>1</sup>-NO<sub>2</sub>)]:Identification of a new linkage isomer
At temperatures below 150 K, the photoactivated metastable endo‐nitrito linkage isomer [Ni(Et4dien)(η2‐O,ON)(η1‐ONO)] (Et4dien=N,N,N′,N′‐tetraethyldiethylenetriamine) can be generated with 100 % conversion from the ground state nitro‐(η1‐NO2) isomer on irradiation with 500 nm light, in the single crystal by steady‐state photocrystallographic techniques. Kinetic studies show the system is no longer metastable above 150 K, decaying back to the ground state nitro‐(η1‐NO2) arrangement over several hours at 150 K. Variable‐temperature kinetic measurements in the range of 150–160 K show that the rate of endo‐nitrito decay is highly dependent on temperature, and an activation energy of Eact=+48.6(4) kJ mol−1 is calculated for the decay process. Pseudo‐steady‐state experiments, where the crystal is continually pumped by the light source for the duration of the X‐ray experiment, show the production of a previously unobserved, exo‐nitrito‐(η1‐ONO) linkage isomer only at temperatures close to the metastable limit (ca. 140–190 K). This exo isomer is considered to be a transient excited‐state species, as it is only observed in data collected by pseudo‐steady‐state methods
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