Porphyrin J aggregates in nanostructured hybrid materials

The widespread interest into organic- inorganic hybrid nanocomposites takes advantage by the emergence of new optical properties and chemical behavior coming from the conjunction of chemically different building blocks. This class of materials have been extensively exploited in several scientific fields, as imaging, catalysis, photonics and optoelectronics. In this framework, due to their interesting spectroscopic properties and their ability to form self-assembled structures, porphyrins represent interesting candidates as organic building blocks to realize hybrids nanocomposites. In particular, tetrakis (4- sulphonatophenyl) porphyrin (TPPS4) is an intriguing compound due to its ability to form self- assembled J- aggregates with different shape and size dependent on the experimental conditions. Here, we focus on the TPPS4 aggregation process assisted and/or catalyzed by the presence of inorganic nanostructured materials such as gold nanostructures and carbon nanotubes (CNTs). Our goal is to build up new hybrids nanocomposites, whose properties merge the optical and photophysical properties of organic and inorganic nanostructures. Exploiting the class of metallic nanosized materials, we have chosen gold nanorods (Au NRs) and clusters composed of ten atoms (Au10). The presence of Au NRs prompts the formation of highly ordered structures of porphyrins in solution whereas Jaggregates trigger the interaction among Au NRs leading to the formation of a J-aggregates/ Au NRs nanohybrid material. Self- assembled structures can be also formed in the presence of Au10 clusters, obtaining nanohybrid materials composed of nanostructured gold and the aggregated porphyrin both in solution and on glass surface. Moreover, the aggregation process has also been examined in the presence of amine functionalized CNTs showing the importance of the alkyl chain length and the number of amine groups in promoting the porphyrin aggregation process. All the nanocomposites have been examined by a detailed spectroscopic and morphologic characterization in solution and on solid state.