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Charge separation at the interface between CdSe and CdTe quantum dots was investigated by comparing the photoconductivity of films consisting of only CdSe or CdTe quantum dots to that of films with alternating layers of CdSe and CdTe quantum dots. The photoconductivity for alternating layers is three times higher than for the single component layers. Different possible mechanisms are discussed, and it is concluded that the dissociation of photoexcited excitons into spatially separated mobile charge carriers at the CdSe/CdTe QD interfaces is the most likely explanation. Given that the yield of charge carrier photogeneration in the multilayer sample is at most one, and under the assumption that the mobility of QD layers in unchanged, we conclude that the yield of charge carrier photogeneration in the single component samples is at most one-third. The thickness of the individual CdSe and CdTe layers was varied, resulting in different distances between the CdSe/CdTe interfaces. The photoconductivity increased with respect to films of only CdSe or CdTe when these interfaces were separated by only one or two quantum dot layers, which implies that exciton diffusion is inefficient.

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A PFSA‐stabilized Pt‐catalyst supported on a novel carbon material, carbon nano networks (CNNs), was synthesized. To benchmark its performance, it was compared to a commercial catalyst, supported on an amorphous carbon support, and to a PFSA stabilized Pt catalyst supported on commercial carbon nano tubes (CNTs). The PFSA‐Pt/CNNs exhibit improved performance compared to commercial catalysts in terms of ORR kinetic activity and durability. Even though PFSA‐Pt/CNTs should show comparable behavior to PFSA‐Pt/CNNs, our experimental results show a slightly superior performance. Optimization of the CNN synthesis route is expected to improve their properties as a carbon support. Since CNN mass production is expected to be cheaper than for CNTs because of the simplicity of the synthesis route, we conclude that CNNs are a promising material for the fuel cell market.

The freezing and melting behavior of water in poly hydroxy ethyl methacrylate (pHEMA) hydrogels of different cross-linker and water contents was investigated in relation to the glass transition temperature (Tg) of the gels. After prolonged cooling at -15 degrees C a constant amount of 1.7 mol water per monomeric unit did not freeze, regardless of both the cross-linker and the water content of the gels. At this water content and temperature, pHEMA gels were below their Tg, and the water molecules were prevented from diffusing to the ice crystals formed in the gel. Therefore, the inability of part of the water in pHEMA gels to freeze is not a thermodynamic phenomenon but is caused by kinetic factors.