Controllable Charge-Transfer Mechanism at Push–Pull Porphyrin/Nanocarbon Interfaces
2019
Arpaçay, Pınar | Maity, Partha | El-Zohry, Ahmed M. | Meindl, Alina | Akca, Sevilay | Plunkett, Shane | Senge, Mathias O. | Blau, Werner J. | Mohammed, Omar F.
Push–pull porphyrins are made of an electron donor (D), an electron acceptor (A), and a conjugated bridge connecting the D and A units. The tunability of their highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap can modulate their inter- and intramolecular charge-transfer (CT) and charge-separation (CS) characteristics and their reaction mechanism. Here, ultrafast charge transfer at the interfaces between 5,15-donor–acceptor push–pull porphyrins (Por-tBu and Por-OC8) and nanocarbon materials in the form of fullerene (C₆₀) and graphene carboxylate (GC) are investigated using steady-state and pump–probe spectroscopic techniques. The strong photoluminescence (PL) quenching of the porphyrin indicates an electron transfer from the photoexcited porphyrin to the nanocarbon materials. The results of steady-state and time-resolved experiments reveal that a static and both static and dynamic electron transfer are dominant in the presence of GC and C₆₀, respectively. This work provides new physical insights into the electron-transfer process and its driving force in donor–acceptor systems that include nanocarbon materials.
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