Control of polymorphism in coronene by the application of magnetic fields

Coronene, a polyaromatic hydrocarbon, has been crystallized for the first time in a different polymorph using a crystal growth method that utilizes magnetic fields to access a unit cell configuration that was hitherto unknown. Crystals grown in magnetic field of 1 T are larger, have a different appearance to those grown in zero field and retain their structure in ambient conditions. We identify the new form, beta-coronene, as the most stable at low temperatures. As a result of the new supramolecular configuration we report significantly altered electronic, optical and mechanical properties.Comment: 32 pages, 17 figure

Direct and Indirect Light Energy Harvesting with Films of Ambiently Deposited ZnO Nanoparticles

Indirect photoelectrochemical processes are possible when employing a palladium film to separate photochemical and electrochemical reactions. Here, an exploratory indirect photoelectrochemical system is developed based on ZnO or Pt@ZnO nanoparticle photocatalysts ambiently deposited onto platinum, glassy carbon, or palladium membrane electrodes and exposed to blue (385 nm) LED light in the presence of glucose hole quencher (in aqueous NaCl). It is demonstrated that under these conditions photo-excitation followed by charge transport of conduction band electrons via inter-grain conduction across ZnO particles triggers the photo-current responses. The conduction band electrons then trigger formation of interstitial hydrogen in a palladium membrane. Transport of the hydrogen across the palladium membrane into the electrochemical compartment occurs within 1–2 min of switching on the light. A proof-of-principle fuel cell with oxygen gas diffusion electrode (cathode) and indirect photo-anode is shown to operate with up to 28 μW cm −2 power output during illumination. Important power-limiting parameters and suggestions for future improvements are discussed. </p

Alkali metal-mediated Dehydrocoupling of Me₂NH.BH₃

Bis(trimethylsilyl)amide derivatives of the group 1 elements (Li, Na, K) are competent pre-catalysts for the dehydrocoupling of Me2NH·BH3via the formation of intermediates containing [H3BNMe2BH2Me2N]− anions.</p