Real-time observation of ultrafast electron injection at graphene–Zn porphyrin interfaces

Abstract

We report on the ultrafast interfacial electron transfer (ET) between zinc(II) porphyrin (ZnTMPyP) and negatively charged graphene carboxylate (GC) using state-of-the-art femtosecond laser spectroscopy with broadband capabilities. The steady-state interaction between GC and ZnTMPyP results in a red-shifted absorption spectrum, providing a clear indication for the binding affinity between ZnTMPyP and GC via electrostatic and π-π stacking interactions. Ultrafast transient absorption (TA) spectra in the absence and presence of three different GC concentrations reveal (i) the ultrafast formation of singlet excited ZnTMPyP*, which partially relaxes into a long-lived triplet state, and (ii) ET from the singlet excited ZnTMPyP* to GC, forming ZnTMPyP˙(+) and GC˙(-), as indicated by a spectral feature at 650-750 nm, which is attributed to a ZnTMPyP radical cation resulting from the ET process.

Cationic Porphyrin‐Graphene Oxide Hybrid: Donor‐Acceptor Composite for Efficient Photoinduced Electron Transfer

“…Masih et al. reported that the ZnTMPyP radical ion and graphene carboxylate pairs recombined back to the initial state with a time constant of 20.18 ps, which is similar to the value measured in this study . Aly et al.…”

“…With the discovery of graphene oxide, the functionalization graphene oxide with porphyrin has become attractive strategy to enhance efficient charge separation and transport in photocatalytic H 2 production systems . To date, a few graphene‐based materials derived from cationic porphyrins have been reported –,–,,. Wojcik et al.…”

Graphene Oxide Functionalized with Cationic Porphyrins as Materials for the Photodegradation of Rhodamine B

“…This band has been assigned to the porphyrin radical cation ZnTMPyP +• by comparison to the spectra for the ZnTMPyP +• described previously in the literature. 51 , 72 The observation of the ZnTMPyP +• gives clear evidence for photoinduced ET from porphyrin to GO.…”

“…It was found previously that back ET within the ion pair of the ZnTMPyP +• and graphene carboxylate occurs with the time constant of 20 ps, which is in the same range as the value obtained it this work. 42 , 51 Aly et al and Larowska et al reported two time constants ranging from several to tens of picoseconds for the decay of the TMAP radical cation formed in the presence of graphene carboxylate and GO, respectively. 29 , 57 The authors proposed that the decay of the porphyrin radical cation with two time constants originates from various geometries of the porphyrin molecules in the nanohybrid material.…”

Graphene‐Based Nanohybrids for Advanced Electrochemical Sensing

“…With the abundant and highly pure functionalized graphene material readily available, its unique structure, and excellent electronic properties, we expect this organic solution‐processable functionalized graphene material to be a competitive entry in the realm of light harvesting and solar‐energy conversion materials for optoelectronic devices. Likewise, a surfactant‐sodium dodecyl benzene sulfonate 68, cationic 5,10,15,20‐tetrakis (1‐methyl‐4‐pyridinio) porphyrin 69, porphyrin/phthalocyanine 70–75, single stranded DNA 76, Congo red, 77 and IL‐NH 2 78 were decorated on graphene sheets.…”