Remarkable fluorescence enhancement versus complex formation of cationic porphyrins on the surface of ZnO nanoparticles
Type
ArticleKAUST Department
Chemical Science ProgramKAUST Solar Center (KSC)
Physical Science and Engineering (PSE) Division
Ultrafast Laser Spectroscopy and Four-dimensional Electron Imaging Research Group
Date
2014-05-28Online Publication Date
2014-05-28Print Publication Date
2014-06-12Permanent link to this record
http://hdl.handle.net/10754/563597
Metadata
Show full item recordAbstract
Fluorescence enhancement of organic fluorophores shows tremendous potential to improve image contrast in fluorescence-based bioimaging. Here, we present an experimental study of the interaction of two cationic porphyrins, meso-tetrakis(1-methylpyridinium-4-yl)porphyrin chloride (TMPyP) and meso-tetrakis(4-N,N,N-trimethylanilinium)porphyrin chloride (TMAP), with cationic surfactant-stabilized zinc oxide nanoparticles (ZnO NPs) based on several steady-state and time-resolved techniques. We show the first experimental measurements demonstrating a clear transition from pronounced fluorescence enhancement to charge transfer (CT) complex formation by simply changing the nature and location of the positive charge of the meso substituent of the cationic porphyrins. For TMPyP, we observe a sixfold increase in the fluorescence intensity of TMPyP upon addition of ZnO NPs. Our experimental results indicate that the electrostatic binding of TMPyP with the surface of ZnO NPs increases the symmetry of the porphyrin macrocycle. This electronic communication hinders the rotational relaxation of the meso unit and/or decreases the intramolecular CT character between the cavity and the meso substituent of the porphyrin, resulting in the enhancement of the intensity of the fluorescence. For TMAP, on the other hand, the different type and nature of the positive charge resulting in the development of the CT band arise from the interaction with the surface of ZnO NPs. This observation is confirmed by the femtosecond transient absorption spectroscopy, which provides clear spectroscopic signatures of photoinduced electron transfer from TMAP to ZnO NPs. © 2014 American Chemical Society.Citation
Aly, S. M. B., Eita, M., Khan, J. I., Alarousu, E., & Mohammed, O. F. (2014). Remarkable Fluorescence Enhancement versus Complex Formation of Cationic Porphyrins on the Surface of ZnO Nanoparticles. The Journal of Physical Chemistry C, 118(23), 12154–12161. doi:10.1021/jp5030075Sponsors
S.M.B.A. is grateful for the postdoctoral fellowship provided by Saudi Basic Industries Corporation (SABIC). The research reported in this publication was supported by the King Abdullah University of Science and Technology.Publisher
American Chemical Society (ACS)ae974a485f413a2113503eed53cd6c53
10.1021/jp5030075