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91.
In aqueous solutions of sonicated egg-lecithin vesicles (5 weight-%) the 1H-NMR parameters line width, area, and chemical shift of the signal of the (CH3)3N+ group were determined in dependence on the dose of gamma radiation (0 … 12 kGy). The application of curopium ions made it possible, by means of a line shape analysis, to calculate these parameters for the inside as well as for the outside lipid layer. With increasing 60Co-radiation dose the line widths increase linearly. The line width for the outside lipid layer increases significantly more rapidly than for the inside layer. This fact allows us to conclude that there exists a preferred radiation damage of the outside lipid layer. The asymmetry may he a consequence of an indirect radiation action mediated by the radicals of the water radiolysis. From the temporal change of the NMR parameters information can be obtained about the radiation action on transport processes in the vesicles. Beginning at a threshold value (approx. 5 kGy) the permeation of the En+ ++ ions to the (CH3)3N+ head groups previously not accessible increases significantly. 相似文献
92.
H.-J. Dietze 《Isotopes in environmental and health studies》2013,49(2-3):46-51
Es wird ein Verfahren zur Isotopenverdünnungsanalyse mit stabilen Isotopen unter Verwendung einer Funkenionenquelle und einem doppelfokussierenden Massenspektrographen beschrieben, welches die gleichzeitige Analyse mehrerer Elemente in pulverförmigen Feststoffen erlaubt. Die Leistungsfähigkeit des Analysenverfahrens wild am Beispiel der Spurenanalyse geologischer Standardproben demonstriert. Das Analysenverfahren erlaubt die Bestimmung von Spurenkonzentrationen bis in den ppb-Bereich mit Standardabweichungen zwischen 2 und 10%. 相似文献
93.
A.E. Cordero-Borboa 《哲学杂志》2013,93(32):3891-3908
Large crystal growths of the Eu2+-doped spatially coherent [KBr0.097I0.903](0.348):[KBr0.459Cl0.511I0.030](0.652) composite were characterized by X-ray diffraction and then studied by epifluorescence optical microscopy. Doping Eu2+ ions were observed to prefer sites located at certain linear structural singularities of the composite matrix to be segregated at. These singularities (2.1?×?107?singularities?cm?2), identified as crystal lattice dislocations, were found to be distributed within the composite matrix so that they form periodic arrays of linear structural singularities (1.8?×?104?singularities?cm?1). These arrays, identified as grain sub-boundaries, were found to envelope individual structural domains (1–5?µm in size) of either KBr0.459Cl0.511I0.030:Eu2+ or KBr0.097I0.903:Eu2+. These domains were found to aggregate among themselves to form the whole composite building. Small misfit angles (e.g. 7′?±?1′ and 10′?±?1′) characterize homo-phase structural domains while large misfit angles are characteristic of hetero-phase structural domains. Crystal lattice dislocations, forming the grain sub-boundaries, were found to present, as structural features, kinks and bifurcation points. The spatial configurations adopted by two of these features are carefully described. 相似文献
94.
Doxycycline can coordinate with europium (III) to form europium (III)-doxycycline complex, which can emit the fluorescence characteristic peak of europium (III) at 617 nm in alkaline solution, and the experiment proved that the fluorescence intensity could be further enhanced in the presence of silver nanoparticles and surfactant alkylphenols polyoxyethylene. So this method was applied to detect doxycycline content in duck meat in this research. First, 390 and 617 nm were selected as the optimum excitation wavelength and optimum emission wavelength by three-dimensional fluorescence spectrometry, respectively. Second, the experimental conditions were optimized through single factor experiment. Lastly, the samples of doxycycline concentration range of 0.05–12 mg/L were analyzed under the optimum experimental conditions. A good linear relationship between the doxycycline concentration and the fluorescence intensity was obtained, and the determination coefficient and the root mean squared error of prediction were 0.9982 and 0.4363 mg/L, respectively. This research showed that it was feasible to achieve the rapid detection of doxycycline content in duck meat by using silver nanoparticles and alkylphenols polyoxyethylene enhanced the fluorescence of europium complex. 相似文献
95.
This study presents a sensitive voltammetric determination of terbutaline (TER) on a platform based on carbon nanotubes (CNTs) and europium oxide nanoparticles (Eu2O3NPs) coated glassy carbon electrodes (GCEs). An ultrasonic bath was performed for the preparation of composite material. The material was characterized by energy dispersive X‐ray spectroscopy (EDX), X‐ray diffraction method (XRD) and scanning electron microscopy (SEM). The Eu2O3NPs/CNTs/GCE system was assessed for the oxidation of terbutaline (TER). A broad oxidation peak was appeared at 0.71 V using a bare GCE. However, the voltammetry of TER has been improved at a GCE coated with CNTs and a well‐defined anodic peak exhibited at 0.61 V. Furthermore, the nanoparticles of Eu2O3 and CNTs coated GCE has greatly improved the electrochemical behaviour of TER and a sharp peak was appeared at 0.59 V. Cyclic voltammetry at Eu2O3NPs/CNTs/GCE also reveals a high catalytic effect for the oxidation of TER with an oxidation peak that is distinctly enhanced compared to GCE and CNTs/GCE. Eu2O3 nanoparticles were utilized to enhance the surface area of GCE and then improve the sensitivity of the procedure. The response of TER was linear over a concentration range of 2.0×10?8 M ?9.5×10?6 M with an LOD of 3.7×10?9 M. Square wave voltammetric analysis of tablets by Eu2O3NPs/CNTs/GCE yielded a recovery of 99.2 % with an RSD% of 3.2. The modified electrode (EuO2NPs/CNTs/GCE) provides accuracy and precision to the analysis of samples. 相似文献
96.
97.
The photoluminescence (PL), electrochemical, and electroluminescence (EL) properties of EuIII complexes, [Eu(cppo)2(tta)3] ( 1 ) and [Eu(cpo)2(tta)3] ( 2 ; TTA=2‐thenoyltrifluoroacetonate) with two carbazole‐based phosphine oxide ligands, 9‐[4‐(diphenylphosphinoyl)phenyl]‐9H‐carbazole (CPPO) and 9‐(diphenylphosphoryl)‐9H‐carbazole (CPO), which have different bipolar structures, donor–π‐spacer–acceptor (D–π–A) or donor–acceptor (D–A) systems respectively, are investigated. The CPPO with D–π–A architecture has improved PL properties, such as higher PL efficiency and more efficient intramolecular energy transfer, than CPO with the D–A architecture. Gaussian simulation proved the bipolar structures and the double‐carrier injection ability of the ligands. The carrier injection abilities of triphenylphosphine oxide, CPO, and CPPO are gradually improved. Notably, the Gaussian and electrochemical investigations indicate that before and after coordination, the carrier injection ability of the ligands show remarkable changes because of the particularity of the D‐π–A and D–A systems. The electrochemical studies demonstrate that coordination induces the electron cloud to migrate from electron‐rich carbazole to electron‐poor diphenylphosphine oxide, and consequently increases the electron‐cloud density on diphenylphosphine oxide, which weakens its ability for electron affinity and induces the elevation of LUMO energy levels of the complexes. Significantly, the π‐spacer in the D–π–A system exhibits a distinct buffer effect on the variation of the electron‐cloud density distribution of the ligand, which is absent in the D–A system. It is demonstrated that the adaptability of the D–π–A systems, especially for coordination, is stronger than that of D–A systems, which facilitates the modification of the complexes by designing multifunctional ligands purposefully. 1 seems favorable as the most efficient electroluminescent EuIII complex with greater brightness, higher efficiencies, and more stable EL spectra than 2 . These investigations demonstrate that the phosphine oxide ligands with D–π–A architecture are more appropriate than those with D–A architecture to achieve multifunctional electroluminescent EuIII complexes. 相似文献
98.
通过高温熔融法在空气条件下制备了Eu2O3掺杂的BaO-B2O3-P2O5玻璃,发射光谱中400~550 nm的宽峰为Eu2+的5d→4f跃迁,即在非还原气氛条件下实现了Eu3+→Eu2+的转变。首先,Eu3+离子不等价取代玻璃基质中的Ba2+导致Eu2+的产生。同时,固体核磁共振谱数据表明当玻璃中的B主要以[BO4]的形式存在时,利于玻璃中的Eu以Eu2+价态存在。与ZnO-B2O3-P2O5∶Eu2+玻璃中Eu2+的发光相比,BaO-B2O3-P2O5玻璃中O2-所形成的Eu的配位场强于ZnO-B2O3-P2O5玻璃中O2-所形成的Eu配位场。Eu在BaO-B2O3-P2O5玻璃中产生的晶体场分裂能大,故d→f跃迁产生的光发射波长较长。 相似文献
99.
Oxidative Conversion of a Europium(II)‐Based T1 Agent into a Europium(III)‐Based paraCEST Agent that can be Detected In Vivo by Magnetic Resonance Imaging
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Dr. Alexander M. Funk Dr. Veronica Clavijo Jordan Prof. A. Dean Sherry Dr. S. James Ratnakar Prof. Zoltan Kovacs 《Angewandte Chemie (International ed. in English)》2016,55(16):5024-5027
The EuII complex of 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) tetra(glycinate) has a higher reduction potential than most EuII chelates reported to date. The reduced EuII form acts as an efficient water proton T1 relaxation reagent, while the EuIII form acts as a water‐based chemical exchange saturation transfer (CEST) agent. The complex has extremely fast water exchange rate. Oxidation to the corresponding EuIII complex yields a well‐defined signal from the paraCEST agent. The time course of oxidation was studied in vitro and in vivo by T1‐weighted and CEST imaging. 相似文献
100.
Use of Lanthanide‐Containing Polyoxometalates to Sensitise the Emission of Fluorescent Labelled Serum Albumin
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Dr. A. Sheila Holmes‐Smith Jacob Crisp Dr. Firasat Hussain Prof. Dr. Greta R. Patzke Dr. Graham Hungerford 《Chemphyschem》2016,17(3):418-424
Monitoring the interaction of biomolecules is important, and the use of energy transfer is a principal technique in elucidating nanoscale interactions. Lanthanide compounds are promising luminescent probes for biological samples as their emission is longer‐lived than any native autofluorescence. Polyoxometalates (POMs) are interesting structural motifs to incorporate lanthanides, offering low toxicity and a size pertinent for biological applications. Here, we employ iso‐structured POMs containing either terbium or europium and assess their interaction with serum albumin by sensitisation of a fluorescent tag on the protein via LRET (luminescence resonance energy transfer) by exciting the lanthanide. Time‐resolved measurements showed energy transfer with an efficiency of over 90 % for the POM–protein systems. The Tb–POM results were relatively straightforward, while those with the iso‐structured Eu–POM were complicated by the effect of protein shielding from the aqueous environment. 相似文献