Chlorosomes are one of the most unique natural light-harvesting antennas and their supramolecular nanostructures are still under debate. Chlorosomes contain bacteriochlorophyll (BChl)-c, d and e molecules and these pigments self-aggregate under a hydrophobic environment inside a chlorosome. The self-aggregates are mainly constructed by the following three interactions: hydrogen bonding, coordination bonding and π-π stacking. Supramolecular nanostructures of self-aggregated BChls have been widely investigated by spectroscopic and microscopic techniques. Model compounds of such chlorosomal BChl molecules have been synthesized and the effects of esterified long alkyl chains at the 17-propionate residue for their self-aggregation have been studied. Structurally simple zinc chlorophyll derivatives possessing an oligomethylene chain as the esterifying group at the 17-propionate residue were prepared as chlorosomal BChl models. The synthetic zinc BChls self-aggregated in nonpolar organic solvents to give precipitates. The resulting insoluble self-aggregated solids were investigated on a variety of substrates, including hydrophobic, neutral and hydrophilic substrates, by visible absorption, circular dichroism and polarized light absorption spectroscopies, as well as atomic force, transmission electron and scanning electron microscopies. The self-aggregates of synthetic Zn-BChls formed rods with an approximately 5 nm diameter and wires with further elongated growth of the rods (aspect ratio >200). The diameter size was consistent with that estimated for natural chlorosomal rods in a filamentous anoxygenic phototroph, Chloroflexus aurantiacus. The supramolecular formation and stability of the rod on the examined substrates depended on the length of an oligomethylene chain at the 17-propionate residue as well as on the surface properties. Especially, the number of the 5 nm rods on the substrates increased with an elongation of the chain.

Macroporous (mp-)

This work focuses on the size effects of Au nanoparticles (AuNPs) on the TiO 2 crystalline phase of nanocomposite AuNPs-embedded TiO 2 (Au-TiO 2 ) thin films, their adsorption ability, and photocatalytic activity. Au-TiO 2 films were synthesized through a solÀgel method using polyvinylpyrrolidone-protected AuNPs (AuNPs@PVP). The mean diameters of AuNPs@PVP dispersed in a sol solution were 2.0 ( 0.7 or 7.9 ( 3.1 nm and the heat-treatment temperature of the films was 400À900 °C. XRD and Ti L 3,2 -edge X-ray absorption nearedge structure (XANES) analysis revealed that AuNPs doping could suppress an anatase to rutile phase transformation. In addition, the larger size of AuNPs doped in TiO 2 film tended to prevent the transformation more effectively. The film doped with the smaller AuNPs@PVP and annealed at 500 °C showed the highest photocatalytic activity among the obtained films because it had the wellcrystallized anatase phase and the high adsorption ability, which was attributed to the existence of a five-coordinated Ti site that was revealed from Ti K-edge XANES measurements.

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