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991.
Andrea Marino Dr. Pradip Chakraborty Dr. Marina Servol Dr. Maciej Lorenc Prof. Eric Collet Prof. Andreas Hauser 《Angewandte Chemie (International ed. in English)》2014,53(15):3863-3867
Light‐induced excited spin‐state trapping (LIESST) in iron(II) spin‐crossover compounds, that is, the light‐induced population of the high‐spin (S=2) state below the thermal transition temperature, was discovered thirty years ago. For irradiation into metal–ligand charge transfer (MLCT) bands of the low‐spin (S=0) species the acknowledged sequence takes the system from the initially excited 1MLCT to the high‐spin state via the 3MLCT state within ca. 150 fs, thereby bypassing low‐lying ligand‐field (LF) states. Nevertheless, these play a role, as borne out by the observation of LIESST and reverse‐LIESST on irradiation directly into the LF bands for systems with only high‐energy MLCT states. Herein we elucidate the ultrafast reverse‐LIESST pathway by identifying the lowest energy S=1 LF state as an intermediate state with a lifetime of 39 ps for the light‐induced high‐spin to low‐spin conversion on irradiation into the spin‐allowed LF transition of the high‐spin species in the NIR. 相似文献
992.
Ankur Maji;Ovender Singh;Sain Singh;Aurobinda Mohanty;Pradip K. Maji;Kaushik Ghosh; 《欧洲无机化学杂志》2020,2020(17):1596-1611
A series of new unsymmetrical (XYC–1 type) palladacycles (C1–C4) were designed and synthesized with simple anchoring ligands L1–4H (L1H = 2-((2-(4-methoxybenzylidene)-1-phenylhydrazinyl)methyl)pyridine, L2H = N,N-dimethyl-4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazono)methyl)aniline, L3H = N,N-diethyl-4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazono)methyl) aniline and L4H = 4-(4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazono) methyl)phenyl)morpholine H = dissociable proton). Molecular structure of catalysts (C1–C4) were further established by single X-ray crystallographic studies. The catalytic performance of palladacycles (C1–C4) was explored with the direct Csp2–H arylation of imidazoles with aryl halide derivatives. These palladacycles were also applied for investigating of Mizoroki–Heck reactions with aryl halides and acrylate derivatives. During catalytic cycle in situ generated Pd(0) nanoparticles were characterized by XPS, SEM and TEM analysis and possible reaction pathways were proposed. The catalyst was employed as a pre-catalyst for the gram-scale synthesis of octinoxate, which is utilized as a UV-B sunscreen agent. 相似文献
993.
Ajay Mandal Shranish Kar Sunil Kumar 《Journal of Dispersion Science and Technology》2016,37(9):1268-1276
The synergistic effect of a new combination of Tween 80 and sodium dodecylbenzenesulfonate (SDBS) surfactants has been studied for wettability alteration of a reservoir rock. The contact angle decreased substantially for the aqueous solution of the mixed surfactant on a crude oil aged quartz substrate when compared to water and individual surfactants viz. SDBS and Tween 80. This established synergism between anionic and non-ionic surfactants. The optimal salinity for reduction of the contact angle has been figured out. The rheological effect of the mixed surfactant solution on the wettability alteration has been investigated. Adsorption of crude components at the solid–fluid interfaces has been observed to visualize the activity at the micro scale. Quantification of adsorption for the mixed surfactant on sand has been studied to meet the economical aspect. Reaction aspects of the mixed surfactant–quartz–crude oil system have been interpreted from FTIR. Functional groups present in the system have also been enquired. 相似文献
994.
The physicomechanical properties of new polyurethanes (PUs) derived from toluene diisocyanate, poly(propylene glycol), and cured by third‐generation hyperbranched polyester polyol (HB3), trimethylolpropane (TMP), or glycerol and their nanocomposites have been investigated. An apparent microphase‐segregated morphology of PU nanocomposites cured by HB3 has been observed by transmission electron microscopy and atomic force microscopy. Morphological studies reveal regions of mostly exfoliated and some intercalated morphology in the case of the nanocomposites, which have been further ascertained by X‐ray diffraction analysis. The HB3‐cured PU nanocomposite containing 8 wt% of modified montmorillonite (Cloisite 30B) clay shows approximately 140% increase in tensile strength along with improvement in thermal and dynamic mechanical properties in comparison with the control hyperbranched PU. It has also been found from Fourier transform infrared spectroscopy analysis that the extent of tethering reactions between the polymer chains carrying residual –NCO groups and the reactive hydroxyl (?OH) groups of HB3 is significant, and the nanofiller has been found to preferentially react with the –NCO group of the prepolymer. Furthermore, the properties of HB3‐cured PU have been compared with the glycerol and TMP‐cured PUs and their nanocomposites. The physicomechanical and thermal properties for nanocomposites of HB3‐cured PUs are superior to those of the conventionally cured PUs. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
995.
Kar M Pauline M Sharma K Kumaraswamy G Gupta SS 《Langmuir : the ACS journal of surfaces and colloids》2011,27(19):12124-12133
Polypeptide-coated silica nanoparticles represent an interesting class of organic-inorganic hybrids since the ordered secondary structure of the polypeptide grafts imparts functional properties to these nanoparticles. The synthesis of a poly-l-glutamic acid (PLGA) silica nanoparticle hybrid by employing N-carboxyanhydride (NCA) polymerization to synthesize the polypeptide chains and Cu catalyzed azide alkyne cycloaddition reaction to graft these chains onto the silica surface is reported. This methodology enables the synthesis of well-defined polypeptide chains that are attached onto the silica surface at high surface densities. The PLGA-silica conjugate particles are well dispersed in water, and have been thoroughly characterized using multinuclear ((13)C, (29)Si) solid state NMR, thermogravimetric analysis, Fourier transform infrared, dynamic light scattering, and transmission electron microscopy. The pH-dependent reversible aggregation of the PLGA-silica particles, driven by the change in PLGA structure, has also been studied. Preliminary results on the use of aqueous dispersions of silica-PLGA for the preparation of three-dimensional macroporous structures with oriented pores by ice templating methodology are also demonstrated. These macroporous materials, comprising a biocompatible polymer shell covalently attached to rigid inorganic cores, adopts an interesting lamellar structure with fishbone-type architecture. 相似文献
996.
Asad Rezaee Kenneth Kar Ho Wong Touraj Manifar Silvia Mittler 《Surface and interface analysis : SIA》2009,41(7):615-623
One application of octadecyltrichlorosilane (OTS) self‐assembled monolayers (SAMs) is its use as thin film resists. In this work, we demonstrated that OTS SAMs can be reliable resists for organo‐metallic chemical vapor deposition (OMCVD) grown gold nanoparticles (Au NPs). In optical sensing applications based on Au NPs, one candidate system consists of patterned OTS SAMs and precisely grown OMCVD Au NPs for achieving a high sensitivity. As an initial step, the OTS SAMs need to perfectly resist the OMCVD Au NP growth. Hence the optimized formation of the OTS SAMs affected by different assembly times and baking temperatures was studied by contact angle, ellipsometry, XPS, SEM, and atomic force microscopy (AFM). To demonstrate the ability of the OTS SAMs to resist OMCVD Au NP growth, the OMCVD process was carried out on two sets of samples: OTS SAMs fabricated under optimized conditions on one set and the other set without OTS SAMs. High‐resolution XPS, RBS, SEM, and ultraviolet‐visible (UV‐Vis) spectroscopy were applied to study the growth of Au NPs on the samples with and without OTS SAM resists. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
997.
Ultraviolet (UV)-mediated DNA damage in various tissues has been well documented. However, research on the damaging effect of UV irradiation on the DNA of corneal epithelium is scarce, even though this is of interest because the cornea is directly exposed to damaging solar (UV) radiation. In this study, we developed a corneal epithelium Comet assay model to assess the background DNA damage (as strand breaks) in cells retrieved from different layers of the porcine corneal epithelium, and to investigate the effect of UV irradiation on DNA damage in corneal epithelial cells. Results show that the background DNA strand breaks decreased significantly (P < 0.001) toward deeper layers of the epithelium. Exposure to the same intensity (0.216 J/cm2) of UVA, UVB and UVC caused a significant (P < 0.001) increase in DNA strand breaks of deeper-layer cells: mean +/- SD %DNA scores (10 gels per treatment, with 100 irradiated cells scored per gel) were 10.2% +/- 1.4% for UVA, 27.4% +/- 4.6% for UVB, and 14.7% +/- 1.8% for UVC compared with 4.2% +/- 0.5% for controls (ambient room light). This study has shown for the first time that the Comet assay for DNA strand breaks can be used successfully with corneal epithelial cells. This report will support future studies investigating environmental influences on corneal health and the assessment of possible protective strategies, and in applying DNA lesion-specific versions of the Comet assay in this corneal epithelial cell model. 相似文献
998.
Szundi I Rose MJ Sen I Eroy-Reveles AA Mascharak PK Einarsdóttir O 《Photochemistry and photobiology》2006,82(5):1377-1384
Nitric oxide (NO) is recognized as one of the major players in various biochemical processes, including blood pressure, neurotransmission and immune responses. However, experimental studies involving NO are often limited by difficulties associated with the use of NO gas, including its toxicity and precise control over NO concentration. Moreover, the reactions of NO with biological molecules, which frequently occur on time scales of microseconds or faster, are limited by the millisecond time scale of conventional stopped-flow techniques. Here we present a new approach for studying rapid biological reactions involving NO. The method is based on designed ruthenium and manganese nitrosyls, [Ru(PaPy3)(NO)](BF4)2 and [Mn(PaPy3)(NO)](ClO4) (PaPy3H = N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide), which upon photolysis produce NO on a fast time scale. The kinetics of the binding of the photogenerated NO to reduced cytochrome c oxidase (CcO) and myoglobin (Mb) was investigated using time-resolved optical absorption spectroscopy. The NO was found to bind to reduced CcO with an apparent lifetime of 77 micros using the [Mn(PaPy3)(NO)]+ complex; the corresponding rate is 10-20 times faster than can be detected by conventional stopped-flow methods. Second-order rate constants of approximately 1 x 10(8) M(-1) s(-1) and approximately 3 x 10(7) M(-1) s(-1) were determined for NO binding to reduced CcO and Mb, respectively. The generation of NO by photolysis of these complexes circumvents the rate limitation of stopped-flow techniques and offers a novel alternative to study other fast biological reactions involving NO. 相似文献
999.
1000.