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Ultrafast Dynamics in Co-sensitized Photocatalyst under Visible and NIR Light Irradiation


Co-sensitization to achieve broad absorption window is a widely accepted technique in light harvesting nanohybrid synthesis. Protoporphyrin (PPIX) and squarine (SQ2) are two organic sensitizers absorbing in the visible and NIR wavelengths of solar spectrum, respectively. In the present study, we have sensitized zinc oxide (ZnO) nanoparticle by PPIX and SQ2 simultaneously for their potential use in broad-band solar light harvesting in photocatalysis. Förster resonance energy transfer (FRET) from PPIX to SQ2 in the close proximity at the ZnO surface has been found to enhance visible light photocatalysis. In order to confirm the effect of intermolecular FRET in the photocatalysis, the exited state lifetime of the energy donor dye PPIX has been modulated by inserting d10 (ZnII) and d7 (CoII) metal ions in the central position of the dye (PP(Zn) and PP(Co)). In the case of PP(Co)-SQ2, extensive photo-induced ligand to metal charge transfer counteracts the FRET efficiency while efficient FRET has been observed for the PP(Zn)-SQ2 pair. This observation has been justified by the comparison of the visible light photocatalysis of the respective nanohybrids and several control studies. We have also investigated the NIR photocatalysis of the co-sensitized nanohybrids which reveal that reduced aggregation of SQ2 due to co-sensitization of PPIX increases the NIR photocatalysis. However, core-metalation of PPIX reduces the NIR photocatalytic efficacy, most probably due to excited state charge transfer from SQ2 to the metal centre of the PP(Co)/PP(Zn) through the conduction band of the host ZnO nanoparticles.

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Publication details

The article was received on 17 Dec 2017, accepted on 12 Mar 2018 and first published on 13 Mar 2018

Article type: Paper
DOI: 10.1039/C7CP08431E
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Ultrafast Dynamics in Co-sensitized Photocatalyst under Visible and NIR Light Irradiation

    J. Patwari, A. Chatterjee, S. Sardar, P. Lemmens and S. K. Pal, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C7CP08431E

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