Water requirements of floodplain rivers and fisheries: existing decision support tools and pathways for development

Fisheries / Rivers / Flood plains / Hydrology / Ecology / Models / Decision support tools / Environmental impact assessment / Methodology / Databases

Performance of lyotropic liquid crystal-based photoelectrochemical capacitors for solar-to- electrical energy conversion

Regenerative photoelectrochemical capacitors, adapted from a experimental system previously reported (J. E. Halls, J. D. Wadhawan, Energy Environ. Sci., 2012, 5, 6541) and based on the doping of a lamellar lyotropic liquid crystal with visible light sensitizer tris(2,2'-bipyridyl)ruthenium(II), N-methylphenothiazine, zinc(II) ions and potassium chloride (as electrolyte) are examined in this work. The two dye species, by virtue of similarity in redox potentials and difference in size and lipophilicity, allow for electron transfer cascades to occur under illumination, which can be harnessed in a power-generating device through the use of a sacrificial counter electrode. In operation as a solar cell, a maximum light-to-electrical power conversion efficiency is reported as being ~5.0% under green light (530 nm centreband, 30 nm bandwidth, 2.2 mW cm-2 intensity), which extrapolates to the opportunistic value of 1% under one Sun conditions. The electrical characteristics of the devices under illumination afford specific capacitances of ca. 0.5-1.0 F g-1 and have fill factors ~20% which are close to the 25% expected for a perfect photogalvanic cell. The time constants of the reported devices (~1.5 s) are consistent with the notion of electroporation of the surfactant lamellae. The advantages of these mid-ranging photoelectrochemical capacitors are suggested as being their low cost and versatility afforded by their flexible liquid framework that appears to realign itself under conditions of open circuit

Theory of Electric Field-Induced Photoluminescence Quenching in Disordered Molecular Solids

The dynamics of excitons in disordered molecular solids is studied theoretically, taking into account migration between different sites, recombination, and dissociation into free charge carriers in the presence of an electric field. The theory is applied to interpret the results of electric field-induced photoluminescence (PL) quenching experiments on molecularly doped polymers by Deussen et al. [Chem. Phys. 207, 147 (1996)]. Using an intermolecular dissociation mechanism, the dependence of the PL quenching on the electric field strength and the dopant concentration, and the time evolution of the transient PL quenching can be well described. The results constitute additional proof of the distinct exciton dissociation mechanisms in conjugated polymer blends and molecularly doped polymers.Comment: 4 pages RevTeX, 3 Postscript figure