Effects of molecular aggregation on photostability of protoporphyrin-IX/halloysite nanotube composites

Abstract This article presents a successfully development of hybrid functional nanomaterials composed of Protoporphyrin-IX/Halloysite nanotubes (PpIX/HNTs), in which the PpIX molecules were adsorbed on the surface of the HNTs at different degree of aggregation. This article also presents a possible explanation for the PpIX adsorption by the HNTs surface and, moreover, the results show that the PpIX molecules adsorption on the HNTs surfaces, and its degree of aggregation, can be controlled by changing the ratio between PpIX and HNTs concentrations. Interestingly, from photodegradation experiments, it is observed that, after the photodegradadion of isolated monomers, the PL spectra and the photodegradation curves show that there is a ratio between the amount of residual monomers and dimers in which the PpIX/HNTs photodegradation decreases significantly, leading to a more photostable system. Therefore, these PpIX/HNTs systems can lead to the development of more efficient porphyrin-based devices and processes, and help to understand the processes of aggregation and formation of porphyrin supramolecular structures.