Noncovalent porphyrin-graphene oxide nanohybrids: The pH-dependent behavior

Ewelina Gacka , Aleksandra Wójcik , Marta Mazurkiewicz-Pawlicka , Artur Małolepszy , Leszek Stobiński , Adam Kubas , Gordon L. Hug , Bronisław Marciniak , Anna Lewandowska-Andrałojć


Noncovalent nanohybrids between meso-(p-hydroxyphenyl)porphyrin (TPPH) and graphene oxide (GO) sheets were studied as a function of pH. The overall charge of the TPPH molecule changes between negative (−4), neutral, and positive (+2) depending on the pH of the solution. Results of Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis confirm successful noncovalent functionalization of GO sheets with TPPH. We applied a number of methods to probe the ground-state as well as the excited-state interaction between the components of the new material. The experimental results were additionally supported by theoretical calculations that included optimizations of the ground-state structures of TPPH and TPPH2+ and their complexes with a molecular model of GO. It was demonstrated that both TPPH and TPPH2+ molecules can be assembled onto the surface of GO, but it was clearly shown that the stronger interaction with GO occurs for TPPH2+. The stronger interaction in the acidic environment can be rationalized by the electrostatic attraction between positively charged TPPH2+ and negatively charged GO, whereas the interaction between TPPH4– and GO at basic pH was largely suppressed. Our comprehensive analysis of the emission quenching led to the conclusion that it was solely attributed to static quenching of the porphyrin by GO. Surprisingly, fluorescence was not detected for the nanohybrid, which indicates that a very fast deactivation process must take place. Ultrafast time-resolved transient absorption spectroscopy demonstrated that although the singlet excited-state lifetime of TPPH2+ adsorbed on the GO sheets was decreased in the presence of GO from 1.4 ns to 12 ps, no electron-transfer products were detected. It is highly plausible that electron transfer takes place and is followed by fast back electron transfer.
Author Ewelina Gacka
Ewelina Gacka,,
, Aleksandra Wójcik
Aleksandra Wójcik,,
, Marta Mazurkiewicz-Pawlicka (FCPE / DSP)
Marta Mazurkiewicz-Pawlicka,,
- Department of Separation Processes
, Artur Małolepszy (FCPE / DSP)
Artur Małolepszy,,
- Department of Separation Processes
, Leszek Stobiński (FCPE / GL)
Leszek Stobiński,,
- WUT Grafen Laboratory
, Adam Kubas
Adam Kubas,,
, Gordon L. Hug
Gordon L. Hug,,
, Bronisław Marciniak - Adam Mickiewicz University (UAM)
Bronisław Marciniak,,
, Anna Lewandowska-Andrałojć - Uniwersytet im. Adama Mickiewicza w Poznaniu (UAM)
Anna Lewandowska-Andrałojć,,
Journal seriesThe Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter, ISSN 1932-7447, (N/A 140 pkt)
Issue year2019
Publication size in sheets0.6
Keywords in Englishabsorption spectroscopy, electron transitions, Fourier transform infrared spectroscopy, graphene, ground state, molecules, nanostructured materials, porphyrins, quenching, thermogravimetric analysis
ASJC Classification2508 Surfaces, Coatings and Films; 1606 Physical and Theoretical Chemistry; 2100 General Energy; 2504 Electronic, Optical and Magnetic Materials
Languageen angielski
Score (nominal)140
Score sourcejournalList
ScoreMinisterial score = 140.0, 20-10-2019, ArticleFromJournal
Publication indicators WoS Citations = 0; Scopus SNIP (Source Normalised Impact per Paper): 2017 = 1.147; WoS Impact Factor: 2017 = 4.484 (2) - 2017=4.691 (5)
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UwagiThis research was financially supported by the National Science Centre (project no. 2015/19/D/ST5/00682). The document number is NDRL 5227 from the Notre Dame Radiation Laboratory. The authors are thankful to Dr. T. Pedzinski for his help in femtosecond transient absorption spectroscopy measurements. E.G. thanks the Director of the Notre Dame Radiation Laboratory for a stipend that supported part of this work. A.K. acknowledges Ministry for Science and Higher Education, Poland, for partial support via fellowship no. 093/STYP/11/2016. Access to high-performance computing resources was provided by the Interdisciplinary Centre for Mathematical and Computational Modelling in Warsaw, Poland, under grant no. G64-9.
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