Fabrication of organized porphyrin-nanotube-attached heat-sensitive polyelectrolyte capsules

A facile method of connecting fluorescent meso-tetrakis(4-sulfonatophenyl)porphine tetranion nanotubes to polyclectrolyte capsules is developed. Heat-sensitive robust polyclectrolyte capsules consisting of poly(diallyldimethylammonium chloride) and poly(styrene sulfonate) multilayers have been fabricated using the conventional layer-by-layer technique. Supramolecular aggregation of porphyrin monomers to nanotubes is induced in the microenvironment of the capsules by sequential addition of salt and acid. Scanning electron microscopy, transmission electron microscopy, and atomic force microscopy images reveal satellite-like structures consisting of a central capsule core with porphyrin nanotubes emerging radially from the capsule walls. The growth and the distribution of the porphyrin units have been monitored by UV-vis spectroscopy, fluorescence spectroscopy, and confocal laser scanning microscopy. Changing the temperature alters the dimensions and the arrangement of the nanotubes on the capsule walls. Such an attachment of porphyrin tubes onto robust functional capsules should help in developing an artificial light-harvesting system.