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The University of Southampton

Photoelectrochemistry and Reversible H-J Interconversion of Porphyrin Nanostructures at an Electrified Soft Interface Seminar

19 November 2019

Event details

Micheál D. Scanlon,* Andrés F. Molina-Osorio and Ivan F. Robayo-Molina

Certain soft interfaces formed between aqueous and organic electrolyte solutions of low miscibility (e.g., trifluorotoluene) are electrochemically active in the sense that it is possible to precisely control the Galvani potential difference between the two adjacent liquids (i.e., to “polarise” or electrify the interface), and thus drive charge transfer reactions. Such interfaces are denoted interfaces between two immiscible electrolyte solutions (ITIES). The ITIES can be controllably electrified by application of a potential either externally through the use of electrodes immersed in both phases or through a common ion dissolved in the organic and aqueous phases.

Synthetic molecular assemblies at soft interfaces exhibit macroscale long-range order and so provide routes to biomimetic analogues that minimise concentration quenching. In this presentation, I will describe a new route to the facile assembly of free-standing layered crystalline films of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrin interfacial nanostructures. I will demonstrate the reversible structural rearrangement of these porphyrin supramolecular structures floating at the liquid-liquid interface from a H- to J-type configuration upon varying the interfacial Galvani potential difference. The latter structural changes were observed in situ by UV/vis and potential modulated fluorescence spectroscopies (both under total internal reflection at the electrified soft interface).

The porphyrin interfacial nanostructures exhibit significant photocurrents in situ at an electrified liquid | liquid interface, providing a new paradigm for realisation of light-harvesting antennae in artificial photosynthetic technologies. To explore this possibility, photo-induced electron transfer between organic electron donors, like ferrocene derivatives, and aqueous electron acceptors, like O2, is achieved by controllably modulating the voltage across the interface (see Fig. 1) [1].

Fig. 1 | Schematic of “soft-photoconversion”; converting light energy to chemical energy using dye-sensitised electrified liquid | liquid interfaces. The donor species (D) is decamethylferrocene and the acceptor species (A) is O2. Light energy is converted to chemical energy in the form of the oxidised donor (D+) and reduced acceptor (A–) spatially separated on either side of the liquid | liquid interface.

[1] A.F. Molina-Osorio et al., ChemRxiv. (2019)


Schematic of soft-photoconversion
Figure 1

Speaker information

Dr Micheál D. Scanlon, The Bernal Institute and Department of Chemical Sciences, School of Natural Sciences, University of Limerick, Ireland. Dr Micheál D. Scanlon is a physical chemist who specialises in electrochemistry. Currently he is a Lecturer in the Department of Chemical Sciences at the University of Limerick (UL) in Ireland. He was awarded a European Research Council (ERC) Starting Grant in 2016 and has established his new research group in the Bernal Institute at UL. Previously, through a Science Foundation Ireland Starting Investigator Research Grant (SFI SIRG), he began his independent research career in the Chemistry Department at University College Cork (UCC) in Ireland. Dr Scanlon was a postdoctoral researcher in the group of Prof. Hubert H. Girault at École Polytechnique de Lausanne (EPFL) in Switzerland and Prof. Edmond Magner at the University of Limerick (UL) in Ireland. He completed his PhD studies under the supervision of Prof. Damien W.M. Arrigan (now Curtin University, Perth, Australia) at the Tyndall National Institute in Cork and has a BSc. in Chemistry from UCC. Dr Scanlon’s current research focuses on using polarised liquid-liquid interfaces for novel approaches to energy conversion and storage, electrosynthesis, catalysis of energy related reactions, bioanalytical sensor and novel reflective mirror development. During his research career to date, Dr Scanlon has co-authored 39 journal articles, 6 review articles and 1 book-chapter. He has published in high-impact international peer-reviewed journals including Angewandte Chemie Int. Ed., Chemical Science (x 3), Energy & Environmental Science, ACS Nano (x 3), Advanced Functional Materials, Chemical Communications (x 2), Analytical Chemistry (x 2), Langmuir (x 2), Chemical Reviews and others. His papers are cited > 2700 times, with an H-index of 26.

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