An Interesting Nanoparticle-Ligand Interaction Between Porphyrins and Gold Nanorods Leads to Luminescent Mesostructures

In this study, we aim to investigate the family of porphyrins from a novel perspective. In particular, we focus on their role in controlling the assembly of gold nanorods (AuNRs) through a synthetic approach. Using a seed-mediated growth method, AuNRs were first synthesized. Then, the surfaces of the AuNRs were functionalized with four different types of porphyrins to explore their unique influence on the assembly process. Two pairs of porphyrins were synthesized: the metal-free porphyrins 1 and 2 and the two corresponding zinc complexes Zn(1) and Zn(2). Compounds 1 and Zn(1) bind to the nanoparticle surface via an amine group, 2 and Zn(2) via a carbon-carbon triple bond. A careful photophysical and morphological characterization has been carried out on the different samples, and interestingly, we observed that metal-free porphyrins 1 and 2 promote nanoparticle assembly, forming luminescent mesostructures. Porphyrin 2 preferentially organizes nanorods by end-to-end assembly, whereas porphyrin 1 does not confer a preferential organization.