Porphyrin aggregates decorated MWCNT film for solar light harvesting: influence of J- and H-aggregation on the charge recombination resistance, photocatalysis, and photoinduced charge transfer kinetics

Abstract

J- and H-aggregates of zinc tetraphenylporphyrin (ZnTPP) on carbon nanotube films (CNTFs) were prepared using the mixed solvent method. This resulted in completely different structures, such as the four-leaf clover and flower, on the CNTF, which were observed by recording SEM images. Characteristic changes in the electronic spectra of the ZnTPP monomer appeared when it underwent J- and H-aggregation. The measured photocurrent significantly varied for the same molecule when it was aggregated in two different ways on ITO and ITO/CNTF. The electron recombination resistance of the two aggregates, which was investigated using electrochemical impedance spectroscopy, was also different. The photocatalytic efficiency of the J- and H-aggregates was examined by performing methylene blue dye decoloration studies. In addition, a scanning electrochemical microscope was used to investigate the photoinduced charge transfer kinetics of the J- and H-aggregates at the electrode/electrolyte interface as a fresh attempt. The heterogeneous charge transfer constants for the J- and H-aggregates in the presence of light at varied intensities were calculated. Thereby, striking differences in the photophysical, photocatalytic, and photoelectrochemical properties of the J- and H-aggregates were visualized throughout our studies.