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961.
Amide-based polymer liquids are important for developing biological and optical colloids or nanofluids. Functionalized properties arise from specific molecular structures. In this investigation, we report model molecular configurations of a polymer liquid, 0.3 g/L poly(vinylidene fluoride) (PVF2) dissolved in liquid N,N-dimethylformamide (DMF), based on the characteristic IR vibration bands. Peculiarly, a ferroelectric β-PVF2 phase reorders on a linear configuration in support with the DMF molecules, showing a characteristic band 840 cm− 1 (CH2 rocking and CF2 asymmetric stretching) with the trans band at 1275 cm− 1. Four CO stretching bands ν10, ν11, ν12, and ν13 of 1650, 1675, 1725, and 1760 cm− 1 (bandwidth Δν½ = 180 cm− 1 in the four bands) arise in four major configurations of DMF-PVF2 pairs (or derivatives). Only one prominent ν10 band 1660 cm− 1 (Δν½ = 75 cm− 1) incurs with a shoulder ν11 of 1725 cm− 1 (Δν½ = 25 cm− 1) in two DMF configurations. A ferroelectric field cased in presence of β-PVF2 leads to enhance IR absorption by as much as an order of magnitude. It leads to converging non-bonding electron density on the amide moiety. 相似文献
962.
Anirban Bhandari Saikat Mishra Ram Chandra Maji Akhilesh Kumar Marilyn M. Olmstead Apurba K. Patra 《Angewandte Chemie (International ed. in English)》2020,59(23):9177-9185
According to the well‐accepted mechanism, methyl‐coenzyme M reductase (MCR) involves Ni‐mediated thiolate‐to‐disulfide conversion that sustains its catalytic cycle of methane formation in the energy saving pathways of methanotrophic microbes. Model complexes that illustrate Ni‐ion mediated reversible thiolate/disulfide transformation are unknown. In this paper we report the synthesis, crystal structure, spectroscopic properties and redox interconversions of a set of NiII complexes comprising a tridentate N2S donor thiol and its analogous N4S2 donor disulfide ligands. These complexes demonstrate reversible NiII‐thiolate/NiII‐disulfide (both bound and unbound disulfide‐S to NiII) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cycle. 相似文献
963.
Dr. Kaizheng Zhu Dr. Ramón Pamies Dr. Nodar Al-Manasir Dr. José Ginés Hernández Cifre Prof. José García de la Torre Prof. Bo Nyström Prof. Anna-Lena Kjøniksen 《Chemphyschem》2020,21(12):1258-1271
The thermoresponsive nature of aqueous solutions of poly(N-isopropylacrylamide) (PNIPAAM) star polymers containing 2, 3, 4, and 6 arms has been investigated by turbidity, dynamic light scattering, rheology, and rheo-SALS. Simulations of the thermosensitive nature of the single star polymers have also been conducted. Some of the samples form aggregates even at temperatures significantly below the lower critical solution temperature (LCST) of PNIPAAM. Increasing concentration and number of arms promotes associations at low temperatures. When the temperature is raised, there is a competition between size increase due to enhanced aggregation and a size reduction caused by contraction. Monte Carlo simulations show that the single stars contract with increasing temperature, and that this contraction is more pronounced when the number of arms is increased. Some samples exhibit a minimum in the turbidity data after the initial increase at the cloud point. The combined rheology and rheo-SALS data suggest that this is due to a fragmentation of the aggregates followed by re-aggregation at even higher temperatures. Although the 6-arm star polymer aggregates more than the other stars at low temperatures, the more compact structure renders it less prone to aggregation at temperatures above the cloud point. 相似文献
964.
E. Chigo Anota Gregorio H. Cocoletzi J. F. Sánchez Ramírez A. Bautista Hernández 《Structural chemistry》2014,25(3):895-901
We have investigated structural and electronic properties of single wall (5,5) boron nitride nanotubes functionalized on the surface and at the ends with paracetamol (C8H9NO2). Studies have been done within the density functional theory as implemented in DMol3 quantum chemistry code. The exchange and correlation energies have been treated according to the generalized gradient approximation with the Perdew–Burke–Ernzerhof parameterization and a basis function with double polarization. The geometry optimization of the (5,5) BNNT-Paracetamol system has been done using the criterion of minimum energy considering eight possible atomic interacting configurations. Simulation results show that the preferential interaction (physisorption) site of the paracetamol is on the nanotube surface in a parallel configuration and making an angle of 45° in the perpendicular direction to the nanotube. The BNNT-Paracetamol system experiences an increase in the polarity which favors the possible dispersion and solubility. As a result of the interaction, the functionalized nanotube chemical reactivity is increased. Provided the work function of the nondoped BNNT-Paracetamol structure decreases as compared with the pristine BNNT, the functionalized nanotubes yielded conditions to improve field emission properties consequently, they may be used as biosensors of paracetamol. Finally, the nanotube doped with carbon atoms induces chemisorption and an increase in the polarity, reactivity, and reduction in the work function. Taking into account, these results it may be suggested the use of the system in sensor devices and optoelectronic systems. 相似文献
965.
Sher Alam Dr. Chokkalingam Anand Kripal Singh Lakhi Prof. Jin‐Ho Choy Wang Soo Cha Dr. Ahmed Elzhatry Prof. Salem S. Al‐deyab Prof. Yutaka Ohya Prof. Ajayan Vinu 《Chemphyschem》2014,15(16):3440-3443
The preparation of size‐controllable Fe2O3 nanoparticles grown in nanoporous carbon with tuneable pore diameters is reported. These hybrid materials exhibit strong non‐linear magnetic properties and a magnetic moment of approximately 229 emu g?1, which is the highest value ever reported for nanoporous hybrids, and can be attributed to the nanosieve effect and the strong interaction between the nanoparticles and the carbon walls. 相似文献
966.
Theoretical Vibrational Raman and Surface‐Enhanced Raman Scattering Spectra of Water Interacting with Silver Clusters 下载免费PDF全文
Marta Sanchéz‐Lozano Marcos Mandado Ignacio Pérez‐Juste Dr. Jose M. Hermida‐Ramón 《Chemphyschem》2014,15(18):4067-4076
In this study, we analyzed the Raman spectrum of a water molecule adsorbed on a cluster of 20 silver atoms, and the plasmonic electromagnetic effect of the silver surface was also considered to give a theoretical prediction of the surface‐enhanced Raman scattering spectrum. The calculations were performed at the density functional theory (DFT) level by using both frozen and unfrozen silver clusters. Two different models were used to consider the plasmonic enhancement; one of them was a modified classical (dipole) model and the other was the coupled perturbed Hartree–Fock method with excitation frequencies obtained from time‐dependent DFT calculations and with proper detuning of these frequencies. The importance of small geometrical distortions of the silver surface in the orientation of the adsorbed water was shown. Moreover, it was shown how the symmetry of the transition dipole moment and the symmetry of the vibrational modes influence the Raman intensities of the SERS spectrum. 相似文献
967.
J. Reyes Miranda A. García Murillo F. de J. Carrillo Romo J. Oliva Uc C. A. Flores Sandoval A. de J. Morales Ramírez S. Velumani E. de la Rosa Cruz V. Garibay Febles 《Journal of Sol-Gel Science and Technology》2014,72(3):435-442
BaTiO3:(5 %)Eu3+ nanoparticles and BaTiO3:(5 %)Eu3+@SiO2 composites were synthesized by the solvothermal method. The effects on the structure, morphology and luminescent properties were studied using samples with different molar ratios of BaTiO3:(5 %)Eu3+@SiO2: 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, 08:92, 6.5:93.5, 05:95, and 1.5:98.5. When the amount of silica in the composites was increased, the orange emission of Eu3+ increased, too; this was observed by exciting the charge transfer band centered at 283 nm. Furthermore, an increase in the intensity of the emission was obtained under excitation at 394 nm as a consequence of the improvement in the crystallinity of the samples. The presence of silica and the degree of crystallinity of the samples were determined through the Fourier transform infrared spectra and X-ray diffraction patterns. All of the results suggest that our ceramic material could be a good candidate for biomedical applications such as biolabeling, since the luminescence of BaTiO3:(5 %)Eu3+@SiO2 composites have an emission intensity higher than that of nanoparticles composed solely of BaTiO3:Eu3+. This work demonstrates that BaTiO3:Eu3+@SiO2 composites have an emission intensity higher than that of nanoparticles composed solely of BaTiO3:Eu3+. 相似文献
968.
Rembisz Żaneta Zakrzewski Robert Ciesielski Witold Skowron Monika Martínez-Máñez Ramón 《平面色谱法杂志一现代薄层色谱法》2014,27(4):240-244
JPC – Journal of Planar Chromatography – Modern TLC - A highly specific and sensitive chromatographic method for the determination of sulfide ions was developed. The procedure is based... 相似文献
969.
Cathepsin‐B Induced Controlled Release from Peptide‐Capped Mesoporous Silica Nanoparticles 下载免费PDF全文
Cristina de la Torre Laura Mondragón Carmen Coll Félix Sancenón María D. Marcos Ramón Martínez‐Máñez Pedro Amorós Mar Orzáez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15309-15314
New capped silica mesoporous nanoparticles for intracellular controlled cargo release within cathepsin B expressing cells are described. Nanometric mesoporous MCM‐41 supports loaded with safranin O ( S1‐P ) or doxorubicin ( S2‐P ) containing a molecular gate based on a cathepsin B target peptidic sequence were synthesized. Solids were designed to show “zero delivery” and to display cargo release in the presence of cathepsin B enzyme, which selectively hydrolyzed in vitro the capping peptide sequence. Controlled delivery in HeLa, MEFs WT, and MEFs lacking cathepsin B cell lines were also tested. Release of safranin O and doxorubicin in these cells took place when cathepsin B was active or present. Cells treated with S2‐P showed a fall in cell viability due to nanoparticles internalization, cathepsin B hydrolysis of the capping peptide, and cytotoxic agent delivery, proving the possible use of these nanodevices as new therapeutic tools for cancer treatment. 相似文献
970.
Cover Picture: From the Lindlar Catalyst to Supported Ligand‐Modified Palladium Nanoparticles: Selectivity Patterns and Accessibility Constraints in the Continuous‐Flow Three‐Phase Hydrogenation of Acetylenic Compounds (Chem. Eur. J. 20/2014) 下载免费PDF全文