14 research outputs found
Zinc PhthalocyanineâGraphene Hybrid Material for Energy Conversion: Synthesis, Characterization, Photophysics and Photoelectrochemical Cell Preparation
Graphene exfoliation upon tip sonication in o-ÂâDCB was accomplished. Then, covalent grafting of (2-Ââ aminoethoxy)(tri-Ââtert-Ââbutyl) zinc phthalocyanine (ZnPc), to exfoliated graphene sheets was achieved. The newly formed ZnPc-Ââgraphene hybrid material was found soluble in common organic solvents without any precipitation for several weeks. Application of diverse spectroscopic techniques verified the successful formation of ZnPc-Ââgraphene hybrid materi-Ââ al, while thermogravimetric analysis revealed the amount of ZnPc loading onto graphene. Microscopy analysis based on AFM and TEM was applied to probe the morphological characteristics and to investigate the exfoliation of graphene sheets. Efficient fluorescence quenching of ZnPc in the ZnPc-Ââgraphene hybrid material suggested that photoinduced events occur from the photoexcited ZnPc to exfoliated graphene. The dynamics of the photoinduced electron transfer was
evaluated by femtosecond transient absorption spectroscopy, thus, revealing the formation of transient species such as ZnPc+ yielding the charge-Ââseparated state ZnPcâą+âgrapheneâąâ. Finally, the ZnPc-Ââgraphene hybrid material was integrated into a photoactive electrode of an optical transparent electrode (OTE) cast with nanostructured SnO2 films (OTE/SnO2), which exhibited sta le and reproducible photocurrent responses and the incident photon-Ââto-Ââcurrent conversion efficien-Ââ cy was determine
Creation of superheterojunction polymers via direct polycondensation: segregated and bicontinuous donorâacceptor Ï-columnar arrays in covalent organic frameworks for long-lived charge separation
By developing metallophthalocyanines
and diimides as electron-donating
and -accepting building blocks, herein, we report the construction
of new electron donorâacceptor covalent organic frameworks
(COFs) with periodically ordered electron donor and acceptor Ï-columnar
arrays via direct polycondensation reactions. X-ray diffraction measurements
in conjunction with structural simulations resolved that the resulting
frameworks consist of metallophthalocyanine and diimide columns, which
are ordered in a segregated yet bicontinuous manner to form built-in
periodic Ï-arrays. In the frameworks, each metallophthalocyanine
donor and diimide acceptor units are exactly linked and interfaced,
leading to the generation of superheterojunctionsîža new type
of heterojunction machinery, for photoinduced electron transfer and
charge separation. We show that this polycondensation method is widely
applicable to various metallophthalocyanines and diimides as demonstrated
by the combination of copper, nickel, and zinc phthalocyanine donors
with pyrommellitic diimide, naphthalene diimide, and perylene diimide
acceptors. By using time-resolved transient absorption spectroscopy
and electron spin resonance, we demonstrated that the COFs enable
long-lived charge separation, whereas the metal species, the class
of acceptors, and the local geometry between donor and acceptor units
play roles in determining the photochemical dynamics. The results
provide insights into photoelectric COFs and demonstrate their enormous
potential for charge separation and photoenergy conversions
Hierarchical organization of perylene bisimides and polyoxometalates for photo-assisted water oxidation
The oxygen in Earth\u2019s atmosphere is there primarily because of water oxidation performed by photosynthetic organisms using solar light and one specialized protein complex, photosystem II (PSII). High-resolution imaging of the PSII \u2018core\u2019 complex shows the ideal co-localization of multi-chromophore light-harvesting antennas with the functional reaction centre. Man-made systems are still far from replicating the complexity of PSII, as the majority of PSII mimetics have been limited to photocatalytic dyads based on a 1:1 ratio of a light absorber, generally a Ru\u2013polypyridine complex, with a water oxidation catalyst. Here we report the self-assembly of multi-perylene-bisimide chromophores (PBI) shaped to function by interaction with a polyoxometalate water-oxidation catalyst (Ru4POM). The resulting [PBI]5Ru4POM complex shows a robust amphiphilic structure and dynamic aggregation into large two-dimensional paracrystalline domains, a redshifted light-harvesting efficiency of >40% and favourable exciton accumulation, with a peak quantum efficiency using \u2018green\u2019 photons (\u3bb > 500 nm). The modularity of the building blocks and the simplicity of the non-covalent chemistry offer opportunities for innovation in artificial photosynthesis
In-Silico Design of a DonorâAntennaâAcceptor Supramolecular Complex for Photoinduced Charge Separation
Solid state NMR/Biophysical Organic Chemistr