title: Impact of metal ions in porphyrin-based applied materials for visible-light photocatalysis: key information from ultrafast electronic spectroscopy.
abstract: Protoporphyrin IX-zinc oxide (PP-ZnO) nanohybrids have been synthesized for applications in photocatalytic devices. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and steady-state infrared, absorption, and emission spectroscopies have been used to analyze the structural details and optical properties of these nanohybrids. Time-resolved fluorescence and transient absorption techniques have been applied to study the ultrafast dynamic events that are key to photocatalytic activities. The photocatalytic efficiency under visible-light irradiation in the presence of naturally abundant iron(III) and copper(II) ions has been found to be significantly retarded in the former case, but enhanced in the latter case. More importantly, femtosecond (fs) transient absorption data have clearly demonstrated that the residence of photoexcited electrons from the sensitizer PP in the centrally located iron moiety hinders ground-state bleach recovery of the sensitizer, affecting the overall photocatalytic rate of the nanohybrid. The presence of copper(II) ions, on the other hand, offers additional stability against photobleaching and eventually enhances the efficiency of photocatalysis. In addition, we have also explored the role of UV light in the efficiency of photocatalysis and have rationalized our observations from femtosecond- to picosecond-resolved studies.
authors.affiliation: Department of Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, SaltLake, Kolkata 700 098 (India), Fax: (+033) 2335-3477.
authors.forename: Prasenjit
authors.initials: P
authors.lastname: Kar
authors.forename: Samim
authors.initials: S
authors.lastname: Sardar
authors.forename: Erkki
authors.initials: E
authors.lastname: Alarousu
authors.forename: Jingya
authors.initials: J
authors.lastname: Sun
authors.forename: Zaki S
authors.initials: ZS
authors.lastname: Seddigi
authors.forename: Saleh A
authors.initials: SA
authors.lastname: Ahmed
authors.forename: Ekram Y
authors.initials: EY
authors.lastname: Danish
authors.forename: Omar F
authors.initials: OF
authors.lastname: Mohammed
authors.forename: Samir Kumar
authors.initials: SK
authors.lastname: Pal
mesh_terms: D002384:Catalysis; D008027:Light; D008670:Metals / Q000737:chemistry*; D008751:Methylene Blue / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D010782:Photolysis; D011166:Porphyrins / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis; D014961:X-Ray Diffraction; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D008670:Metals; D011166:Porphyrins; D015034:Zinc Oxide; D008751:Methylene Blue
keywords: femtochemistry; femtosecond transient absorption spectroscopy; nanohybrids; porphyrinoids; protoporphyrin IX