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61.
Dr. Simon Pascal Léo Bucher Dr. Nicolas Desbois Dr. Christophe Bucher Dr. Chantal Andraud Prof. Dr. Claude P. Gros 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4971-4979
The synthesis of dyad and triad aza‐BODIPY‐porphyrin systems in two steps starting from an aryl‐substituted aza‐BODIPY chromophore is described. The properties of the resulting aza‐BODIPY‐porphyrin conjugates have been extensively investigated by means of electrochemistry, spectroelectrochemistry, and absorption/emission spectroscopy. Fluorescence measurements have revealed a dramatic loss of luminescence intensity, mainly due to competitive energy transfer and photoinduced electron transfer involving charge separation followed by recombination. 相似文献
62.
63.
Structure, kinetics of crystallization, and dielectric resonances of waste-derived glass-ceramic prepared via quench-heating route were studied as a function of dosage of iron ore tailing (IOT) within 20–40 wt% using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and vector network analyzer (VNA) measurements. The glass-ceramic mainly consisted of ferrite crystals embedded in borosilicate glass matrix. Crystallization kinetics and morphologies of ferrite crystals as well as coordination transformation of boron between [BO4] and [BO3] in glass network were adjustable by changing the amount of IOT. Dielectric resonances in 6–13 GHz were found to be dominated by oscillations of Ca2+ cations in glass network with [SiO4] units on their neighboring sites. Ni2+ ions made a small contribution to those resonances. Diopside formed when IOT exceeded 35 wt%, which led to weakening of the resonances. 相似文献
64.
The waste management of glass fiber reinforced polymer (GRP) materials, in particular those made with thermosetting resins, is a critical issue for the composites industry because these materials cannot be reprocessed. Therefore, most thermosetting GRP waste is presently sent to landfill, in spite of the significant environmental impact caused by their disposal in this way. The limited GRP waste recycling worldwide is mostly due to its intrinsic thermosetting properties, lack of characterization data and unavailability of viable recycling and recovery routes. One of the possibility for re-using GRP industrial by-product is in form of powder as a partial aggregate replacement or filler addition in cement based composites for applications in sustainable construction materials and technologies. However, the feasibility of this kind of reutilization strongly depends on the morphology and particle size distribution of a powder made up of polymer granules and glass fibers. In the present study, the use of image analysis method, based on scanning electron microscopy (SEM) and ImageJ processing program, is proposed in order to evaluate the morphology of the particles and measure the particle size and size distribution of fine GRP waste powder. The obtained results show a great potential of such a method in order to be considered as a standardized method of measurement and analysis in order to characterize the grain size and size distribution of GRP particles before exploiting any compatibility issue for its recycling management. 相似文献
65.
Experimental Charge Density Evidence for Pnicogen Bonding in a Crystal of Ammonium Chloride 下载免费PDF全文
Dr. Yulia V. Nelyubina Prof. Alexander A. Korlyukov Prof. Konstantin A. Lyssenko 《Chemphyschem》2015,16(3):676-681
Chemical binding in crystalline ammonium chloride, a simple inorganic salt with an unexpectedly complex bonding pattern, was studied by using a topological analysis of electron density function derived from high‐resolution X‐ray diffraction. Supported by periodic quantum chemical calculations, it provided experimental evidence for weak σ‐hole bonds (1.5 kcal mol?1) that involve ammonium cations in a crystal. Our results show this type of supramolecular interaction to be more numerous than has been found to date by using gas‐phase calculations or statistical analysis of CSD. 相似文献
66.
Unraveling the Degradation Mechanism of Purine Nucleotides Photosensitized by Pterins: The Role of Charge‐Transfer Steps 下载免费PDF全文
Mariana P. Serrano Dr. Carolina Lorente Dr. Claudio D. Borsarelli Dr. Andrés H. Thomas 《Chemphyschem》2015,16(10):2244-2252
Photosensitized reactions contribute to the development of skin cancer and are used in many applications. Photosensitizers can act through different mechanisms. It is currently accepted that if the photosensitizer generates singlet molecular oxygen (1O2) upon irradiation, the target molecule can undergo oxidation by this reactive oxygen species and the reaction needs dissolved O2 to proceed, therefore the reaction is classified as 1O2‐mediated oxidation (type II mechanism). However, this assumption is not always correct, and as an example, a study on the degradation of 2′‐deoxyguanosine 5′‐monophosphate photosensitized by pterin is presented. A general mechanism is proposed to explain how the degradation of biological targets, such as nucleotides, photosensitized by pterins, naturally occurring 1O2 photosensitizers, takes place through an electron‐transfer‐initiated process (type I mechanism), whereas the contribution of the 1O2‐mediated oxidation is almost negligible. 相似文献
67.
Strong,Thermally Superinsulating Biopolymer–Silica Aerogel Hybrids by Cogelation of Silicic Acid with Pectin 下载免费PDF全文
Dr. Shanyu Zhao Dr. Wim J. Malfait Dr. Arnaud Demilecamps Dr. Yucheng Zhang Dr. Samuel Brunner Lukas Huber Dr. Philippe Tingaut Dr. Arnaud Rigacci Dr. Tatiana Budtova Dr. Matthias M. Koebel 《Angewandte Chemie (International ed. in English)》2015,54(48):14282-14286
Silica aerogels are excellent thermal insulators, but their brittle nature has prevented widespread application. To overcome these mechanical limitations, silica–biopolymer hybrids are a promising alternative. A one‐pot process to monolithic, superinsulating pectin–silica hybrid aerogels is presented. Their structural and physical properties can be tuned by adjusting the gelation pH and pectin concentration. Hybrid aerogels made at pH 1.5 exhibit minimal dust release and vastly improved mechanical properties while remaining excellent thermal insulators. The change in the mechanical properties is directly linked to the observed “neck‐free” nanoscale network structure with thicker struts. Such a design is superior to “neck‐limited”, classical inorganic aerogels. This new class of materials opens up new perspectives for novel silica–biopolymer nanocomposite aerogels. 相似文献
68.
Dong‐Gyu Lee Ohhun Gwon Han‐Saem Park Su Hwan Kim Juchan Yang Prof. Sang Kyu Kwak Prof. Guntae Kim Prof. Hyun‐Kon Song 《Angewandte Chemie (International ed. in English)》2015,54(52):15730-15733
The electric conductivity‐dependence of the number of electrons transferred during the oxygen reduction reaction is presented. Intensive properties, such as the number of electrons transferred, are difficult to be considered conductivity‐dependent. Four different perovskite oxide catalysts of different conductivities were investigated with varying carbon contents. More conductive environments surrounding active sites, achieved by more conductive catalysts (providing internal electric pathways) or higher carbon content (providing external electric pathways), resulted in higher number of electrons transferred toward more complete 4e reduction of oxygen, and also changed the rate‐determining steps from two‐step 2e process to a single‐step 1e process. Experimental evidence of the conductivity dependency was described by a microscopic ohmic polarization model based on effective potential localized nearby the active sites. 相似文献
69.
Acceleration of Long‐Range Photoinduced Electron Transfer through DNA by Hydroxyquinolines as Artificial Base Pairs 下载免费PDF全文
Dr. Effi Bätzner Dr. Yu Liang Caroline Schweigert Dr. Andreas‐Neil Unterreiner Prof. Dr. Hans‐Achim Wagenknecht 《Chemphyschem》2015,16(8):1607-1612
The C‐nucleoside based on the hydroxyquinoline ligand (Hq) is complementary to itself and forms stable Hq–Hq pairs in double‐stranded DNA. These artificial Hq–Hq pairs may serve as artificial electron carriers for long‐range photoinduced electron transfer in DNA, as elucidated by a combination of gel electrophoretic analysis of irradiated samples and time‐resolved transient absorption spectroscopy. For this study, the Hq–Hq pair was combined with a DNA‐based donor–acceptor system consisting of 6‐N,N‐dimethylaminopyrene conjugated to 2′‐deoxyuridine as photoinducible electron donor, and methyl viologen attached to the 2′‐position of uridine as electron acceptor. The Hq radical anion was identified in the time‐resolved measurements and strand cleavage products support its role as an intermediate charge carrier. Hence, the Hq–Hq pair significantly enhances the electron hopping capability of DNA compared to natural DNA bases over long distances while keeping the self‐assembly properties as the most attractive feature of DNA as a supramolecular architecture. 相似文献
70.
Dr. Alessandra Alberti Dr. Ioannis Deretzis Dr. Giovanna Pellegrino Dr. Corrado Bongiorno Dr. Emanuele Smecca Dr. Giovanni Mannino Dr. Filippo Giannazzo Prof. Guglielmo Guido Condorelli Dr. Nobuya Sakai Prof. Tsutomu Miyasaka Dr. Corrado Spinella Dr. Antonino La Magna 《Chemphyschem》2015,16(14):3064-3071
We investigate the degradation path of MAPbI3 (MA=methylammonium) films over flat TiO2 substrates at room temperature by means of X‐ray diffraction, spectroscopic ellipsometry, X‐ray photoelectron spectroscopy, and high‐resolution transmission electron microscopy. The degradation dynamics is found to be similar in air and under vacuum conditions, which leads to the conclusion that the occurrence of intrinsic thermodynamic mechanisms is not necessarily linked to humidity. The process has an early stage, which drives the starting tetragonal lattice in the direction of a cubic atomic arrangement. This early stage is followed by a phase change towards PbI2. We describe how this degradation product is structurally coupled with the original MAPbI3 lattice through the orientation of its constituent PbI6 octahedra. Our results suggest a slight octahedral rearrangement after volatilization of HI+CH3NH2 or MAI, with a relatively low energy cost. Our experiments also clarify why reducing the interfaces and internal defects in the perovskite lattice enhances the stability of the material. 相似文献