Multiple-bilayered RGO-porphyrin films: from preparation to application in photoelectrochemical cells

In this study, multiple-bilayered reduced graphene oxide (RGO)-porphyrin films have been prepared via fabrication of multiple-bilayered graphene oxide (GO)-porphyrin films and succeeding vapour reduction of the GO-porphyrin films. The layer-by-layer method, which takes advantage of the pi-pi and electrostatic interactions between GO sheets and porphyrin molecules, has been used to prepare the multiple-bilayered GO-porphyrin films. Three porphyrins have been used: positively charged, neutral, and negatively charged porphyrins. The changes of the transparency of the films with the number of the bilayers show that the multiple-bilayered structures of the films formed with the positively charged porphyrin is better controlled as compared to the films formed with the neutral and the negatively charged porphyrins. UV-visible and photoluminescence (PL) spectra show that GO quenches the PL of porphyrins in the multiple-bilayered GO-porphyrin films, indicating photoinduced electron transfer from porphyrins to GO; meanwhile, photoinduced electron transfer also occurs from porphyrins to RGO in the multiple-bilayered RGO-porphyrin films. Photocurrent response has been measured using the multiple-bilayered RGO-porphyrin films prepared on indium-tin oxide glass substrates as working electrodes in photoelectrochemical cells. The multiple-bilayered RGO-porphyrin films show enhanced photocurrent with respect to that of the porphyrins alone due to the fact that RGO sheets function as electron acceptors and form transportation paths for electrons in the multiple-bilayered films.