SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Phthalocyanine

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In contrast to pristine zinc phthalocyanine (1), zinc phthalocyanine based oPPV-oligomers (2-4) of different chain lengths interact tightly and reversibly with graphite, affording stable and finely dispersed suspensions of mono- to few-layer graphene-nanographene (NG)-that are photoactive. The p-type character of the oPPV backbones and the increasing length of the oPPV backbones facilitate the overall π-π interactions with the graphene layers. In NG/2, NG/3, and NG/4 hybrids, strong electronic coupling between the individual components gives rise to charge transfer from the photoexcited zinc phthalocyanines to NG to form hundreds of picoseconds lived charge transfer states. The resulting features, namely photo- and redoxactivity, serve as incentives to construct and to test novel solar cells. Solar cells made out of NG/4 feature stable and repeatable photocurrent generation during several ‘on-off’ cycles of illumination with monochromatic IPCE values of around 1%.

Concepts: Photoelectric effect, Cadmium, Solar cell, Photovoltaics, Length, Photovoltaic module, Band gap, Phthalocyanine

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A biosorbent was developed by simple dried Agaricus bisporus (SDAB) and effectively used for the biosorption of cationic dyes, Crystal Violet and Brilliant Green.

Concepts: Dye, Dyes, Pigment, Mushroom, Triarylmethane dyes, Agaricus bisporus, Phthalocyanine

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Purified laccase from Trametes polyzona WR710-1 was used as biocatalyst for bisphenol A biodegradation and decolorization of synthetic dyes. Degradation of bisphenol A by laccase with or without redox mediator, 1-hydroxybenzotriazole (HBT) was studied. The quantitative analysis by HPLC showed that bisphenol A rapidly oxidized by laccase with HBT. Bisphenol A was completely removed within 3 h and 4-isopropenylphenol was found as the oxidative degradation product from bisphenol A when identified by GC-MS. All synthetic dyes used in this experiment, Bromophenol Blue, Remazol Brilliant Blue R, Methyl Orange, Relative Black 5, Congo Red, and Acridine Orange were decolorized by Trametes laccase and the percentage of decolorization increased when 2 mM HBT was added in the reaction mixture. This is the first report showing that laccase from T. polyzona is an affective enzyme having high potential for environmental detoxification, bisphenol A degradation and synthetic dye decolorization.

Concepts: Enzyme, Redox, Nicotinamide adenine dinucleotide, Dye, Triarylmethane dyes, Azo dyes, Acridine, Phthalocyanine

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Porphyrins, phthalocyanines and subphthalocyanines are three attractive classes of chromophores with intriguing properties making them suitable for the design of artificial photosynthetic systems. The assembly of these components by a supramolecular approach is of particular interest as it provides a facile means to build multi-chromophoric arrays with various architectures and tuneable photophysical properties. In this paper, we show the formation of mixed host-guest supramolecular complexes that consist of a β-cyclodextrin-conjugated subphthalocyanine, a tetrasulfonated porphyrin and a series of silicon(iv) phthalocyanines substituted axially with two β-cyclodextrins via different spacers. We found that the three components form supramolecular complexes held by host-guest interactions in aqueous solution. Upon excitation of the subphthalocyanine part of the complex, the excitation energy is delivered to the phthalocyanine unit via excitation energy transfer and the porphyrin chromophore acts as an energy transfer bridge enabling this process. It was shown that photo-induced charge transfer also takes place. A sequential electron transfer process from the porphyrin unit to the phthalocyanine moiety and subsequently from the subphthalocyanine moiety to the porphyrin unit takes place, and the probability of this process is controlled by the linker between β-cyclodextrin and phthalocyanine. The lifetime of the charge-separated state was found to be 1.7 ns by transient absorption spectroscopy.

Concepts: Electron, Metabolism, Electromagnetic radiation, Chemistry, Supramolecular chemistry, Porphyrin, Macrocycle, Phthalocyanine

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Dye-sensitized solar cells (DSCs) are a promising source of renewable energy. However, power conversion efficiency (PCE) of devices has been limited largely by the difficulty of producing electricity using photons from the near-infrared (NIR) spectral region. Metal-free organic sensitizers frequently employ strong electron donating or withdrawing moieties to tune the optical band gap to allow the absorption of lower energy wavelengths in charge transfer systems while porphyrins and phthalocyanines use substituents to shift the Soret and Q bands toward lower energy absorption. Very few devices employing precious metal free dyes have been able to achieve panchromatic, NIR photon conversion for electricity generation at wavelengths >750 nm despite a tremendous number of sensitizers published over last 25 years. This minireview seeks to compile a summary of these sensitizers to encourage assimilation, analysis and development of efficient future NIR sensitizers. Herein, we discuss common synthetic strategies, optical properties and electronic properties of the most successful panchromatic organic sensitizers in this regard.

Concepts: Photon, Energy, Quantum mechanics, Light, Electromagnetic radiation, Solar cell, Porphyrin, Phthalocyanine

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Co-sensitization in dye sensitized solar cells (DSSCs) received significant attention for improving the efficiency and stability of renewable energy resources. In this context, ruthenium metal and porphyrin dyes based DSSCs achieved increment in power conversion efficiency (PCE) from 8 - 11% to 11-14% after addition of additives, co-adsorbents and co-sensitizers by reducing the aggregation and charge recombination. Among the three supporting materials, co-sensitizers played major role to enhance the performance and stability of DSSCs which assist in commercialization. In this review, we highlighted the importance of co-sensitizers in photovoltaic performance of ruthenium metal and porphyrin dye based solar cells. Consequently, co-sensitizers are rather important to modulate the PCE of DSSCs and find realistic future practical applications.

Concepts: Energy, Solar cell, Photovoltaics, Energy conversion, Energy conversion efficiency, Renewable energy, Wind power, Phthalocyanine

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Three regioregular phthalocyanines (1-3) were synthesized selectively by the cyclic tetramerization of phthalonitriles bearing a bulky diarylamine substituent at the next position of nitrile. The steric repulsion at the tetramerization of bulky phthalonitriles allowed for the selective formation of regioregular phthalocyanines as confirmed by NMR and single crystal X-ray structural analyses. The absorption spectrum of 1 substituted with di(4-tert-buthylphenyl)amine groups at the non-peripheral positions showed a non-split Q band at 764 nm, which was red-shifted by 83 nm compared with that of metal free phthalocyanine (H2Pc). The TD-DFT calculation and electrochemical studies prove that the substitution of diarylamine groups at the α positions effectively destabilizes the HOMO energy level, which causes a large red-shift of the Q band. Moreover, 1 can generate a one-electron oxidation specie through chemical oxidation. The Q band position of 2 bearing 4,4'-dimetoxyphenylamine units was further shifted by 10 nm compared with that of 1. In addition, 3 having carbazole units showed a small red-shift of the Q band relative to H2Pc. The hole-mobility of 2 in thin film was determined to be 1.1 × 10-5 cm V-1 s-1 by using a space charge limited current method. A perovskite solar cell employing 2 as a hole-transporting layer gave an efficiency of 5.1 % under standard global 100 W cm-2 AM 1.5 G illumination.

Concepts: Hydrogen, Redox, Electrochemistry, Solar cell, Absorption, Electrochemical cell, Electrolysis, Phthalocyanine

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A ytterbium(iii) acetate complex with a BODIPY and a porphyrin as co-sensitizers emits strongly at 978 nm over a broader excitation window between 450-560 nm.

Concepts: Acetic acid, Phthalocyanine

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Phthalocyanine and porphyrin were among the first organic compounds investigated by means of electronic spectroscopy in superfluid helium nanodroplets. Superfluid helium nanodroplets serve as a very gentle host system for preparing cold and isolated molecules. The uniqueness of helium nanodroplets is with respect to the superfluid phase which warrants the vanishing viscosity and, thus, minimal perturbation of the dopant species at a temperature as low as 0.37 K. These are ideal conditions for the study of molecular spectra in order to analyze structures as well as dynamic processes. Besides the investigation of the dopant species itself, molecular spectroscopy in helium droplets provides information on the helium droplet and in particular on microsolvation. This article, as part of a special issue on phthalocyanines and porphyrins, reviews electronic spectroscopy of phthalocyanine and porphyrin compounds in superfluid helium nanodroplets. In addition to the wide variety of medical as well as technical and synthetical aspects, this article discusses electronic spectroscopy of phthalocyanines and porphyrins in helium droplets in order to learn about both the dopant and the helium environment.

Concepts: Fundamental physics concepts, Molecule, Atom, Liquid, Porphyrin, Superfluid, Macrocycle, Phthalocyanine

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Bacteriochlorin-based dyes, having a push-pull type of configuration similar to the YD2 dye, were theoretically designed based on the modification of the macrocycle and π-conjugated bridge for use in dye-sensitized solar cells. Various parameters were assessed to determine its structure-property relationships, such as the absorption profile based on time-dependent density functional theory, non-linear optical properties from (hyper)polarizability data, ground- and excited-state oxidation potentials, and the electronic properties of the free and adsorbed dyes. Based on the results, the most appropriate macrocycle would be 7,7,17,17-tetramethyl-7H,8H,17H,18H-porphyrin and for its π-conjugated bridge were either thieno[3,2-b]thiophene, dithieno[3,2-b:2',3'-d]thiophene, or 4,4-diisopropyl-4H-cyclopenta[2,1-b:3,4-b']dithiophene. These newly designed dyes produced an absorption spectra having a range of 300 to 800 nm which could likely increase the light harvesting efficiency. It has better nonlinear properties than the reference thereby ensuring higher charge-transfer properties. And the dye regeneration efficiency is within the optimized value of 0.2 eV which could minimize the excessive loss of voltage. This shows that through theoretical approach we can deductively design analogues before synthesis to streamline the process in the design of dyes to produce an efficient dye sensitized solar cells.

Concepts: Scientific method, Density functional theory, Solar cell, Absorption, Photovoltaics, Dye-sensitized solar cell, Theory, Phthalocyanine