Ultrafast electron injection at the cationic porphyrin–graphene interface assisted by molecular flattening

Aly, Shawkat M.; Parida, Manas R.; Alarousu, Erkki; Mohammed, Omar F.

doi:10.1039/c4cc04985c

Cited by 76 publications

(112 citation statements)

References 36 publications

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“…[15][16][17][18] To further confirm the non-covalent association of ZnTMPyP with GC, the emission spectrum of a 5 mM aqueous solution of ZnTMPyP was measured after excitation at 563 nm in the presence of GC at different concentrations, as shown in Fig. The intensity of the Soret band shows a dramatic decrease upon addition of GC.…”

Section: Resultsmentioning

confidence: 99%

“…6,7 There have been a number of systems comprising noncovalent association of porphyrins with small molecules, 8,9 polymers, 10 DNA, 11 metallic nanoparticles, 12 and semiconductor quantum dots. 15 It has been demonstrated that fluorescence of the porphyrins was quenched upon interaction with GC due to electron or/and energy transfer. 15 It has been demonstrated that fluorescence of the porphyrins was quenched upon interaction with GC due to electron or/and energy transfer.…”

Section: Introductionmentioning

confidence: 99%

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

Masih

Aly

Usman

et al. 2015

Phys. Chem. Chem. Phys.

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Masih

Aly

Usman

et al. 2015

Phys. Chem. Chem. Phys.

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“…As there was no further interaction observed between CD and TMPyP after addition of 9 mM CD, we selected this concentration of CD for the further investigation with GC. 23 Hence, the estimated difference in efficiency can be related to the increased localization of electron density on the cavity of TMPyP and the ease of porphyrin oxidation in the TMPyP-b-CD complex compared to free TMPyP; this is evident from the change in oxidation potentials shown by the cyclic voltammetry measurements discussed below. As a result of complexation with b-CD, the observed spectral change in Soret band intensity can be attributed to the change in the local environment around the pyridinium unit.…”

Section: Introductionmentioning

confidence: 99%

To what extent can charge localization influence electron injection efficiency at graphene–porphyrin interfaces?

Parida

Aly

Alarousu

et al. 2015

Phys. Chem. Chem. Phys.

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Controlling the electron transfer process at donor-acceptor interfaces is a research direction that has not yet seen much progress. Here, with careful control of the charge localization on the porphyrin macrocycle using β-cyclodextrin as an external cage, we are able to improve the electron injection efficiency from cationic porphyrin to graphene carboxylate by 120%. The detailed reaction mechanism is also discussed.

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“…[67][68][69][70] Because the dynamics of ground-state bleach recovery are directly proportional to the exciton depopulation, they are used as a convenient probe to determine the excited state dynamics including electron trapping and charge separation and recombination at materials surfaces and interfaces. After 350 nm of optical excitation, which was above the bandgap excitation, a clear ground-state bleach of approximately 500 nm corresponding to steady-state absorption was observed for the materials with a slight change in spectral features, as shown in Figure S9.…”

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confidence: 99%

Dendritic Tip-on Polytriazine-Based Carbon Nitride Photocatalyst with High Hydrogen Evolution Activity

Bhunia¹,

Melissen

Parida³

et al. 2015

Chem. Mater.

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144

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Developing stable, ubiquitous and efficient water-splitting photocatalyst material that has extensive absorption in the visible-light range is desired for a sustainable solar energy-conversion device. We herein report a triazine-based carbon nitride (CN) material with different C/N ratios achieved by varying the monomer composition ratio between melamine (Mel) and 2,4,6-triaminopyrimidine (TAP). The CN material with a different C/N ratio was obtained through a two-step synthesis protocol: starting with the solution state dispersion of the monomers via hydrogen-bonding supramolecular aggregate, followed by a salt-melt high temperature polycondensation. This protocol ensures the production of a highly crystalline polytriazine imide (PTI) structure consisting of a copolymerized Mel-TAP network. The observed bandgap narrowing with an increasing TAP/Mel ratio is well simulated by density functional theory (DFT) calculations, revealing a negative shift in the valence band upon substitution of N with CH in the aromatic rings. Increasing the TAP amount could not maintain the crystalline PTI structure, consistent with DFT calculation showing the repulsion associated with additional C-H introduced in the aromatic rings. Due to the high exciton binding energy calculated by DFT for the obtained CN, the cocatalyst must be close to any portion of the material to assist the separation of excited charge carriers for an improved photocatalytic performance. The photocatalytic activity was improved by providing a dendritic tipon-like shape grown on a porous fibrous silica KCC-1 spheres, and highly dispersed Pt nanoparticles (<5 nm) were photodeposited to introduce heterojunction. As a result, the Pt/CN/KCC-1 photocatalyst exhibited an apparent quantum efficiency (AQE) as high as 22.1 ± 3% at 400 nm and the silica was also beneficial for improving photocatalytic stability. The results obtained by time-resolved transient absorption spectroscopy measurements were consistent with the improved photocatalytic activity with the slowest carrier recombination for the optimized CN photocatalyst.

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Ultrafast electron injection at the cationic porphyrin–graphene interface assisted by molecular flattening

Cited by 76 publications

References 36 publications

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

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

To what extent can charge localization influence electron injection efficiency at graphene–porphyrin interfaces?

Dendritic Tip-on Polytriazine-Based Carbon Nitride Photocatalyst with High Hydrogen Evolution Activity

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