Batch versus flow photochemistry: a revealing comparison of yield and productivity.

The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20% lower than that of batch, whereas three-layer reactors were 20% more productive. Finally, the utility of flow chemistry was demonstrated in the scale-up of the ring-opening reaction of a potentially explosive [1.1.1] propellane with butane-2,3-dione.

Artificial photosynthesis for solar fuels.

This contribution was presented as the closing lecture at the Faraday Discussion 155 on artificial photosynthesis, held in Edinburgh Scotland, September 5-7 2011. The world needs new, environmentally friendly and renewable fuels to exchange for fossil fuels. The fuel must be made from cheap and "endless" resources that are available everywhere. The new research area of solar fuels aims to meet this demand. This paper discusses why we need a solar fuel and why electricity is not enough; it proposes solar energy as the major renewable energy source to feed from. The scientific field concerning artificial photosynthesis expands rapidly and most of the different scientific visions for solar fuels are briefly overviewed. Research strategies and the development of artificial photosynthesis research to produce solar fuels are overviewed. Some conceptual aspects of research for artificial photosynthesis are discussed in closer detail.

Design and study of a cost-effective solar photoreactor for pesticide removal from water.

In order to remove pesticides from water, a basic photoreactor has been built. We evaluated the performance of this photoreactor using two commercial photocatalytic materials from Ahlstrom group and from Saint-Gobain, with solar and artificial UV-lamps. We compared the kinetics of photocatalytic degradation and mineralization of Diuron in the same reactor with of both photocatalyst supports. We showed that Diuron is easily degraded under solar or artificial irradiation, while the kinetics of mineralization in the same condition are very slow. The behaviour of these commercial materials has been studied after several uses in the same conditions. We showed the effectiveness of this basic and cheap photoreactor for the elimination of pesticide in water.

Expert assessments of future photovoltaic technologies.

Subjective probabilistic judgments about future module prices of 26 current and emerging photovoltaic (PV) technologies were obtained from 18 PV technology experts. Fourteen experts provided detailed assessments, including likely future efficiencies and prices under four policy scenarios. While there is considerable dispersion among the judgments, the results suggest a high likelihood that some PV technology will achieve a price of $1.20/Wp by 2030. Only 7 of 18 experts assess a better-than-even chance that any PV technology will achieve $0.30/Wp by 2030; 10 of 18 experts give this assessment by 2050. Given these odds, and the wide dispersion in results, we conclude that PV may have difficulty becoming economically competitive with other options for large-scale, low-carbon bulk electricity in the next 40 years. If $0.30/Wp is not reached, then PV will likely continue to expand in markets other than bulk power. In assessing different policy mechanisms, a majority of experts judged that R&D would most increase efficiency, while deployment incentives would most decrease price. This implies a possible disconnect between research and policy goals. Governments should be cautious about large subsidies for deployment of present PV technology while continuing to invest in R&D to lower cost and reduce uncertainty.

[Photoexcitation mechanism of photoconductive device by organic/inorganic thin-film heteropairing].

Photoconductive devices with organic (polyvinylcarbazole-PVK)/inorganic (zinc-sulfide--ZnS) thin-film heteropairing were fabricated. In external field, the excitation profile of the steady-state photoconductivity and the primary photoexcitation process of hybrid devices were presented and discussed. Comparison of photoconductivity of the devices and absorption spectra of PVK and ZnS implied that both layers absorption contributes to the photocurrent, but the effective part is at the interface of PVK and ZnS. The dependence of maximum photocurrent on the applied voltage and the dark and illuminated current spectra indicates the ultrafast charge transfer at the interface.

Film processing and the environment. Reducing pollution, water consumption, and costs.

PURPOSE: X-ray film processing is associated with pollution from photo chemicals and from the water used to rinse the film. We tested a new processing system that was aimed at reducing both environmental pollution and costs through the use of solid photo chemicals and recirculation of the rinsing water. MATERIAL AND METHODS: Before and after the installation of new mixers for the solid chemicals and a system for recirculating the rinsing water, we measured: water consumption, processor function quality, image quality, archivability, and the waste-silver content in the rinsing water. RESULTS: After the installation of a simple system for recirculating the rinsing water, there was an 88% reduction in water and film consumption as shown in the amount of water/m2 film that was used. At the same time, the release of silver-contaminated rinsing water directly into the sewers was stopped. Image quality remained unchanged. Archivability was assessed at more than 100 years. The solid photo chemicals and specially designed mixers proved efficient and provided a stable image quality of high standard. It was thus possible to reduce the risk of pollution from the transportation, storage and handling of liquid chemicals. CONCLUSION: A simple recirculation system for the rinsing water would significantly reduce water consumption and eliminate contamination of the environment by silver. The on-site preparation of photo chemicals proved viable and reduced the costs of film processing.