Electronic Coupling–Decoupling-Dependent Single-Molecule Interfacial Electron Transfer Dynamics in Electrostatically Attached Porphyrin on TiO2 Nanoparticles

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Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, United States
*E-mail: [email protected]. Tel.: 419-372-1840.
Cite this: J. Phys. Chem. C 2016, 120, 22, 12313–12324
Publication Date (Web):May 10, 2016
Copyright © 2016 American Chemical Society
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Factors controlling the interfacial electron-transfer (ET) dynamics in molecule–semiconductor systems have been intensively investigated in recent years. Here, we study dynamics of interfacial ET on Zn(II) meso-tetra (N-methyl-4-pyridyl) porphine tetrachloride (ZnTMPyP)–TiO2 nanoparticle (NP) system using single-molecule photon-stamping spectroscopy while electrostatically controlling the coupling between ZnTMPyP and TiO2 NP by changing the surface charge of the TiO2 NP. The single-molecule fluorescence trajectories show strong fluctuation and blinking between bright and dark states providing clear indication for the binding affinity between ZnTMPyP and the TiO2 NP via electrostatic interaction. By changing the surface charge on the TiO2 NP, positive or negative, we are able to change the coupling between ZnTMPyP and the TiO2 NP, which is revealed from the dominant dark states distribution in fluorescence trajectories and shorter fluorescence lifetime of ZnTMPyP attached on negatively charged TiO2 NP surface compared to positively charged TiO2 NP surface. The observed difference in fluorescence trajectories and lifetime of ZnTMPyP can be qualitatively accounted for by considering the change in purely electronic coupling factor caused by the positively or negatively charged TiO2 NP surface in electrostatically bound dye-sensitized TiO2 systems. Strong binding interaction between ZnTMPyP and negatively charged TiO2 NP is further observed by higher fluorescence anisotropy compared to ZnTMPyP on positively charged TiO2 NP.

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  • AFM images showing the topography of sample surface (PDF)

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Cited By

This article is cited by 3 publications.

  1. Vishal Govind Rao and H. Peter Lu . Inhomogeneous and Complex Interfacial Electron-Transfer Dynamics: A Single-Molecule Perspective. ACS Energy Letters 2016, 1 (4) , 773-791. https://doi.org/10.1021/acsenergylett.6b00237
  2. I. V. Loukhina, I. S. Khudyaeva, A. Yu. Bugaeva, B. N. Dudkin, D. V. Belykh. Modification of magnesium silicate with 15(2)-methyl ester of 13(1),17(3)-diamino-N,N′-bis(2-hydroxyethyl)-13(1),17(3)-dioxochlorin e 6. Russian Journal of General Chemistry 2017, 87 (5) , 912-917. https://doi.org/10.1134/S1070363217050036
  3. Bharat Dhital, Vishal Govind Rao, H. Peter Lu. Probing single-molecule electron–hole transfer dynamics at a molecule–NiO semiconductor nanocrystalline interface. Physical Chemistry Chemical Physics 2017, 19 (26) , 17216-17223. https://doi.org/10.1039/C7CP01476G