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91.
Marialuigia MacChione Daniela Cupelli Giovanni De Filpo Fiore P. Nicoletta Giuseppe Chidichimo 《Liquid crystals》2013,40(10):1337-1341
We have investigated the morphology and electro-optical properties of reverse mode polymer dispersed liquid crystals as a function of liquid crystal loading. Reverse mode shutters have been obtained by a polymerization-induced phase separation of mixtures, consisting of a liquid crystalline monomer and a non-reactive nematic liquid crystal, placed between rough conductive surfaces. Such surfaces are able to keep the photopolymerizable mixtures homeotropically aligned without the use of any aligning polymer substrate. OFF state transmittances are always larger than 80% and the switching fields decrease if the non-reactive liquid crystal percentage is increased. Both rise and decay times are always lower than 10 ms. The electro-optical properties have been related to the sample morphology and a simple mode is proposed. 相似文献
92.
Giovanni De Filpo Marialuigia MacChione Fiore P. Nicoletta Daniela Cupelli Giuseppe Chidichimo 《Liquid crystals》2013,40(12):1569-1573
Elliptic droplets of nematic liquid crystal dispersed in a fluid organic monomer were obtained by phase separation from an isotropic mixture consisting of an organic monomer and a nematic liquid crystal contained in a poly(ethylene terephthalate) cell with inner surfaces treated with rubbed polyimide. The elliptic shape is a consequence of the constraint upon droplet growth along the direction perpendicular to the cell surfaces owing to the small thickness. Then, the resulting droplets will have a contact area with the inner surfaces of the cell treated with polyimide, which will impart a planar orientation on the liquid crystal in the droplet. By means of an optical microscope, using a simple pin hole of 5 μ m, we have selected single droplets for a series of samples having different contact areas. By polarized infrared spectroscopy we have also studied the liquid crystal orientation in selected areas of the droplets. We then report the dependence of the order parameter of the liquid crystal on different contact areas with the alignment surface of the cell. The good degree of planar alignment of the liquid crystal in the elliptic droplets allows the use of such a technique for realizing electro-optical films operating in the reverse mode. We report the electro-optical transmission of reverse mode films with different sizes of elliptic droplet. 相似文献
93.
Dr. Benjamin J. Coe Dr. Simon P. Foxon Dr. Madeleine Helliwell Dr. Daniela Rusanova Dr. Bruce S. Brunschwig Prof. Dr. Koen Clays Griet Depotter Dr. Marcin Nyk Prof. Dr. Marek Samoc Dominika Wawrzynczyk Prof. Dr. Javier Garín Dr. Jesús Orduna 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6613-6629
New complexes with six ferrocenyl (Fc) groups connected to ZnII or CdII tris(2,2′‐bipyridyl) cores are described. A thorough characterisation of their BPh4? salts includes two single‐crystal X‐ray structures, highly unusual for such species with multiple, extended substituents. Intense, visible d(FeII)→π* metal‐to‐ligand charge‐transfer (MLCT) bands accompany the π→π* intraligand charge‐transfer absorptions in the near UV region. Each complex shows a single, fully reversible FeIII/II wave when probed electrochemically. Molecular quadratic nonlinear optical (NLO) responses are determined by using hyper‐Rayleigh scattering and Stark spectroscopy. The latter gives static first hyperpolarisabilities β0 reaching as high as approximately 10?27 esu and generally increasing with π‐conjugation extension. Z‐scan cubic NLO measurements reveal high two‐photon absorption cross‐sections σ2 of up to 5400 GM in one case. DFT calculations reproduce the π‐conjugation dependence of β0, and TD‐DFT predicts three transitions close in energy contributing to the MLCT bands. The lowest energy transition has octupolar character, whereas the other two are degenerate and dipolar in nature. 相似文献
94.
Anca Mazare Mirela Dilea Daniela Ionita Ioana Demetrescu 《Surface and interface analysis : SIA》2014,46(3):186-192
The present study is focused on tailoring the morphology of TiO2 nanotubes obtained on Ti6Al7Nb alloy and evaluating their electrochemical behavior in simulated body fluid. The presence of the α and β phases on the Ti6Al7Nb alloy leads to a two‐scale organization of the nanotubes on the samples – which in turn affects the electrochemical stability. Furthermore, five different types of TiO2 nanotubes were obtained in various electrolytes (e.g. Generation I, a mixture of Generation II and Generation III, Generation III). Electrochemical behavior analysis of all obtained nanotubes morphologies was composed of Tafel plots, cyclic voltammetry and electrochemical impedance spectroscopy and was correlated with morphology data obtained from SEM (nanotubes diameters from top‐view and nanotube length from cross‐section view). The electrochemical results showed that morphological modifications of the Ti6Al7Nb alloy's surface by electrochemical anodizing have induced changes to the electrochemical behavior of the material, evident in the corrosion rates. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
95.
Study of the retention behavior of iodinated X‐ray contrast agents in hydrophilic interaction liquid chromatography,comparing bare silica and zwitterionic stationary phases 下载免费PDF全文
Daniela Salas Francesc Borrull Rosa Maria Marcé Núria Fontanals 《Journal of separation science》2014,37(9-10):1111-1117
Iodinated X‐ray contrast media are the most widely used pharmaceuticals for intravascular administration in X‐ray diagnostic procedures. The increasing concern of the fate of these compounds into the environment has led to the development of analytical methods to determine them. However, these methods present problems due to the polar character of these analytes. In this paper, hydrophilic interaction LC is presented as an alternative technique. The retention of iodinated X‐ray contrast media was studied in two bare silica phases with different particle designs (i.e. porous and Fused Core?) and a zwitterionic sulfoalkylbetaine phase. The effect of the most important parameters of the mobile phase was studied for each stationary phase. It was observed that optimal mobile phase conditions included buffers with a high buffering capacity. Additionally, the retention mechanisms involved were studied in order to provide some insight into the possible occurring interactions. The contributions of partition and adsorption and the effect of the temperature on the retention of analytes were evaluated on all of the stationary phases. 相似文献
96.
Larissa Mueller Heike Traub Norbert Jakubowski Daniela Drescher Vladimir I. Baranov Janina Kneipp 《Analytical and bioanalytical chemistry》2014,406(27):6963-6977
The analysis of single cells is a growing research field in many disciplines such as toxicology, medical diagnosis, drug and cancer research or metallomics, and different methods based on microscopic, mass spectrometric, and spectroscopic techniques are under investigation. This review focuses on the most recent trends in which inductively coupled plasma mass spectrometry (ICP-MS) and ICP optical emission spectrometry (ICP-OES) are applied for single-cell analysis using metal atoms being intrinsically present in cells, taken up by cells (e.g., nanoparticles), or which are artificially bound to a cell. For the latter, especially element tagged antibodies are of high interest and are discussed in the review. The application of different sample introduction systems for liquid analysis (pneumatic nebulization, droplet generation) and elemental imaging by laser ablation ICP-MS (LA-ICP-MS) of single cells are highlighted. Because of the high complexity of biological systems and for a better understanding of processes and dynamics of biologically or medically relevant cells, the authors discuss the idea of “multimodal spectroscopies.” 相似文献
97.
98.
Dr. Alberto Lena Dr. Alessandra Benassi Michele Stasi Christine Saint-Pierre Prof. Mauro Freccero Dr. Didier Gasparutto Dr. Sophie Bombard Prof. Filippo Doria Dr. Daniela Verga 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(35):e202200734
Combining the selectivity of G-quadruplex (G4) ligands with the spatial and temporal control of photochemistry is an emerging strategy to elucidate the biological relevance of these structures. In this work, we developed six novel V-shaped G4 ligands that can, upon irradiation, form stable covalent adducts with G4 structures via the reactive intermediate, quinone methide (QM). We thoroughly investigated the photochemical properties of the ligands and their ability to generate QMs. Subsequently, we analyzed their specificity for various topologies of G4 and discovered a preferential binding towards the human telomeric sequence. Finally, we tested the ligand ability to act as photochemical alkylating agents, identifying the covalent adducts with G4 structures. This work introduces a novel molecular tool in the chemical biology toolkit for G4s. 相似文献
99.
Zeynep Güven Lars Denker Hadi Dolati Daniela Wullschläger Dr. Bartosz Trzaskowski Dr. René Frank 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(32):e202200673
Donor-acceptor cyclopropanes or cyclobutanes are dipolar reagents, which are widely used in the synthesis of complex organic (hetero)cycles in ring expansion reactions. Applying this concept to boron containing heterocycles, the four-membered borete cyclo-iPr2N-BC10H6 reacted with the carbon donor ligands 2,6-xylylisonitrile and the carbene IMes :C(NMesCH)2 with ring expansion and ring fusion, respectively. In particular, the tetracyclic structure formed with IMes displays zwitterionic character and absorption in the visible region. In contrast to the carbene IMes, the heavier carbenoids :Si(NDippCH)2 and :Ga(AmIm) with a two-coordinate donor atom afford spiro-type bicyclic compounds, which display four-coordinate geometry at silicon or gallium. (TD-)DFT calculations provide deeper insight into the mechanism of formation and the absorption properties of these new compounds. 相似文献
100.
Andrea Mosseri Dr. Maria Sancho-Albero Dr. Marilisa Leone Donatella Nava Dr. Francesco Secundo Prof. Daniela Maggioni Prof. Luisa De Cola Prof. Alessandra Romanelli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(37):e202200693
Self-assembly of biomolecules such as peptides, nucleic acids or their analogues affords supramolecular objects, exhibiting structures and physical properties dependent on the amino-acid or nucleobase composition. Conjugation of the peptide diphenylalanine (FF) to peptide nucleic acids triggers formation of self-assembled structures, mainly stabilized by interactions between FF. In this work we report formation of homogeneous chiral fibers upon self-assembly of the hybrid composed of the tetraphenylalanine peptide (4F) conjugated to the PNA dimer adenine-thymine (at). In this case nucleobases seem to play a key role in determining the morphology and chirality of the fibers. When the PNA “at” is replaced by guanine-cytosine dimer “gc”, disordered structures are observed. Spectroscopic characterization of the self-assembled hybrids, along with AFM and SEM studies is reported. Finally, a structural model consistent with the experimental evidence has also been obtained, showing how the building blocks of 4Fat arrange to give helical fibers. 相似文献