Efficient fluorescence quenching of ZnPc in the ZnPc—graphene hybrid material was observed and the deactivation pathway was evaluated by using femtosecond transient absorption spectroscopy. An electrode of the ZnPc—graphene hybrid material was prepared and its photoelectrochemical properties were examined. It was found to exhibit stable and reproducible photocurrent responses, and the incident-photon-to-current conversion efficiency was determined to be 2. These results highlight the important role of the covalent grafting of ZnPc onto the graphene sheet for enhancing the photo-induced electron-transfer phenomena and achieving higher IPCE values as compared to non-covalently interacting ZnPc  , or ZnPc-functionalized phenylene vinylene oligomers .
Figure 5: Covalent grafting of 2-aminoethoxy tri- tert -butyl phthalocyanine zinc to exfoliated graphene sheets via direct nucleophilic addition of primary amines . Figure 5: Covalent grafting of 2-aminoethoxy tri- tert -butyl phthalocyanine zinc to exfoliated graphene shee In the second strategy followed for the realization of a Pc—graphene hybrid, few-layered graphene, obtained by exfoliating graphite through sonication, was utilized.
The exfoliated graphene sheets were then reacted with excess N -methylglycine and 4-formylbenzoic acid to yield functionalized graphene that carries pyrrolidine rings with pendant phenylcarboxylic acid units. Photoexcitation of Pc—graphene and evaluation of the species by pump-probe femtosecond transient absorption spectroscopy revealed the formation of the radical anion of graphene through a broad band in the NIR region. Based on multi-wavelength analysis, a short-lived and a long-lived component with lifetimes of 3.
Figure 6: Phthalocyanine—graphene hybrid material, prepared upon condensation of mono-OH-derivatized phthalocyanine with pendant phenylcarboxylic acid units present as substituents of pyrrolidine rings on pre-modified graphene sheets . Figure 6: Phthalocyanine—graphene hybrid material, prepared upon condensation of mono-OH-derivatized phthaloc Interestingly, due to the strong electron-withdrawing effect of the sulfonyl units, the particular phthalocyanine component acts as electron acceptor in the graphene—ZnPc hybrid material .
Complementary electrochemical measurements and photophysical assays, based on fluorescence emission and transient absorption spectroscopy, verified that electron transfer occurs from graphene to ZnPc.
The new exTTF-graphene material was fully characterized by spectroscopic, thermal, and microscopy means. Importantly, the electrochemical properties of exTTF-graphene were studied by cyclic voltammetry which allowed identification of the formation of a radical ion pair that includes one-electron oxidation of exTTF and one electron reduction of graphene. Figure 8: Extended tetrathiafulvalene units covalently attached to exfoliated graphene via Bingel cycloaddition reaction . Figure 8: Extended tetrathiafulvalene units covalently attached to exfoliated graphene via Bingel cycloadditi A slow recombination of the photoexcited charges was identified and demonstrates the high potential of the hybrid material for immediate applications in photocatalysis as well as in solar energy conversion schemes .
The Ru bpy 2 py Cl—graphene hybrid material highlights the importance of the covalent binding and the chemistry chosen for the particular functionalization methodology for the enhancement of photo-induced electron transfer. Figure 9: Graphene sheets covalently functionalized with a Ru-bipyridine complex .
Table 1: Some photophysical properties for selected graphene-based hybrid materials. Although in early stages oxidation was the method of choice for the functionalizing graphene, the introduction of numerous lattice defects that significantly alter the electronic properties of graphene, required the development of new routes for obtaining graphene sheets that preserve to a large extent the high conductivity of the material. Therefore, graphene-based hybrid materials are formed by exfoliating graphite and a subsequent chemical functionalization. Such graphene-based donor—acceptor hybrid materials were found to possess interesting optical and photophysical properties.
Charge-transfer phenomena mainly from the photoexcited organic chromophore units to the graphene layers were observed. Although the potential of these materials to be applied in solar and photoelectrochemical cells is great, there is surely a need for the preparation and the evaluation of more graphene-based materials in order to fully understand and describe the electronic interaction processes of these systems.crysnuemari.tk
Babak B. Naghshine and Amirkianoosh Kiani. Twitter: BeilsteinInst. Beilstein J.
Chemical functionalization toward the formation of donor—acceptor hybrids A plethora of soluble and easy-to-handle graphene-based materials have been prepared and methodologies for the functionalization of graphene have already been reviewed [12,]. When azomethine ylides are added to graphene, a fused pyrrolidine ring is formed at the junction between two six-membered rings of the graphene lattice.
Theory of chemical reactions in condensed media and its applications to biological processes
In general, the addition takes place on double bonds between two six-membered rings present on graphene, yielding methano-modified graphene-based materials. Moreover, modifications of the original Bingel reaction exist, utilizing i carbanionic precursors to methano-modified graphene other than malonates, and ii alternative pathways generating the reactive monohalomalonate intermediate in situ; Addition of in situ generated aryl diazonium salts, proceeding via the release of dinitrogen . The reaction mechanism involves an electron transfer from graphene to the diazonium salt, resulting in the formation of a radical aryl unit, which subsequently adds to the sp 2 -carbon lattice of graphene; Addition of azides forming aziridine adducts onto graphene .
The particular functionalization proceeds via nitrenes as generated upon the thermal or photochemical decomposition of azides and the liberation of dinitrogen. Jump to Scheme 1. Jump to Figure 1. Jump to Figure 2. Jump to Figure 3. Jump to Scheme 2. Jump to Scheme 3.
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Jump to Figure 4. Jump to Figure 5. Jump to Figure 6. Jump to Figure 7. Jump to Figure 8. Jump to Figure 9. Science , , — Nature , , — Nanotechnology , 21, Nanoscale , 4, — Acta , 56, — Functionalization of Graphene.
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B , , — Carbon , 48, — B , 2, — C , , — Small , 9, — Reference Reference 1. References 5,6.
References Reference 3. References 3,4. Reference 2.
Reference 9. References 7,8. References 31, References 27, References 29, References 12, All Thematic Issues All volumes Article is part of the thematic issue Atomic scale interface design and characterisation.
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Keep informed. Subscribe Email Notification Register and get informed about new articles. How To Cite. The development of new experimental techniques and detection systems at LEAF is an integral part of our effort to produce ground-breaking science. The long-term storage of solar energy as fuels or valuable chemicals requires efficient coupling of light absorption and chemical transformations. Mechanistic studies of transition-metal complexes and metal clusters which couple photo-induced electron transfer processes to the bond-forming reactions required in the photogeneration of dihydrogen and the photoreduction of carbon dioxide to carbon monoxide or methanol are a major focus.
Since M-H bond cleavage is a requisite step in both catalytic and stoichiometric reactions of metal hydrides, a goal is an improved understanding of the factors that influence the rates and mechanisms for rupture of M-H bonds. This information contributes to the rational design of new homogeneous catalysts and catalytic reactions that are environmentally friendly, through use of alternative renewable feedstocks, readily recycled catalysts, aqueous solvents, or solvent-free processes.
Department of Energy. One of ten national laboratories overseen and primarily funded by the Office of Science of the U. Department of Energy DOE , Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security.
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