Boiling intensifies the radiolytic conversion of diglyme since it stimulates the cleavage of the C–O bonds in the excited molecules and the primary radical cations, enhances the radical exchange reactions, and weakens the diglyme regeneration reactions. 相似文献
Studies on the separation of calcium and neodymium ions by using ethylenediaminetetraacetic acid (H4EDTA) as a complexing agent were performed. This research was undertaken due to the possibility of H4EDTA applying to isolate rare earth elements from the solution after acidic leaching of phosphogypsum, and because of the similarity of coordination properties of calcium and lanthanides ions. The experiment was carried out in model systems containing Ca2+ and Nd3+ ions in hydrochloric or sulphuric acid. The content of calcium and neodymium metals, phase composition and thermal behaviour of the obtained products were determined by ICP-OES, FTIR, XRD and TG/DTA techniques. During the separation process, the precipitates of a light pink colour were obtained. The obtained results show that the neodymium ethylenediaminetetraacetate has been successfully formed and that the isolation of neodymium ions was more efficient in chloride medium. The precipitate included 72.2 and 3.9% of the starting amount of neodymium and calcium used in the experiment, respectively. However, in sulphates medium, these amounts were equal to 73.8 and 53.5%, respectively. Moreover, the obtained powder was polluted with sulphates. The addition of the EDTA in an excess (15%) contributed only to an increase in calcium content in the complex.
Three alkylcarbonates of γ-cyclodextrin, i.e. hexyl, octyl and dodecylcarbonate, were synthesized and characterized, with
the goal of formulating solid nanoparticles. The series of alkylcarbonates showed amphiphilic properties and were capable
of forming micelles and nanoparticles. Blank and drug-loaded alkylcarbonate nanoparticles were prepared with each alkylcarbonate,
using the solvent injection technique. Progesterone was chosen as model drug. The sizes of both unloaded and loaded nanoparticles
were in the 80–200 nm range, with narrow size distribution and spherical shape, as shown by TEM analysis.
The zeta potentials of unloaded nanoparticles were in the −20 to −24.0 mV range, and were slightly decreased in loaded nanoparticles.
Drug-loading capacity was good; DSC analysis did not detect the progesterone melting peak, indicating the drug had interacted
with the cyclodextrin alkylcarbonates. In vitro release kinetics of progesterone from the three types of nanoparticles were
slow. These results indicate that γ-CD alkylcarbonate nanoparticles might be used as prolonged drug delivery system. 相似文献
Heterocoagulation of large cationic polypyrrole particles with small anionic polyacrylate beads followed by heat processing of the heterocoagulate units proved to be an efficient method in the preparation of core-shell particles with conductive cores and dielectric shells. Specific conditions required for producing monodispersed composite particles with uniform shells were examined in the stages of the synthesis of polypyrrole particles with controlled size, in "one-step" heterocoagulation of oppositely charged polypyrrole microbeads with small polyacrylic particles, and during shell formation by spreading of the acrylic polymer on the surface of polypyrrole cores. 相似文献
A new series of hybrid materials of type [Cp*2M][M'(dca)3] has been prepared by cation templation and structurally characterised (M = Fe(III), Co(III); M'= Mn(II), Fe(II), Co(II), Ni(II), Cd(II); dca-= N(CN)2-). The crystallographic analysis of [Cp*2Fe][Cd(dca)(3)] showed that the [Cd(dca)3]- anionic framework is of a symmetrical 3-D alpha-polonium type, containing octahedral Cd nodes and micro (1,5)-dca bridging ligands. The [Cp*2Fe]+ cations occupy the cube-like cavities within the framework. The cationic and anionic-framework sublattices remain magnetically independent and display susceptibilities, over the range 300 to 2 K, of a Curie-Weiss nature obtained by adding a S= 1/2 (Cp*2Fe+) or a S= 0 (Cp*2Co+) contribution to those of the weakly antiferromagnetically coupled frameworks of M'. These hybrid species do not show any intrinsic long-range magnetic order. The present [Cp*2Fe]M'(dca)3] series display the characteristic, unusually shaped [Cp*2Fe]+ Mossbauer line, in the range 295-5 K, assigned (below 101 K) as the sum of a narrow and a broad line. Relaxation effects were evident. The [Fe(dca)3]- compound showed superimposed low-spin Fe(III) and high-spin Fe(II) lines, the latter giving relaxation broadening effects. 相似文献
Infrared spectra of 1,3-dimethyl-2-imidazolidinone, 2-imidazolidinone, 1,1,3,3-tetramethylurea, 1,3-dimethylurea, and 1,1-dimethylurea have been collected in a variety of solvents. When the C=O stretching frequencies for the molecules in a common solvent were recorded, higher frequencies were found for the cyclic ureas as compared to the non-cyclic ureas. When data were analyzed within each class of urea derivatives, it was found that an increase in the number of methyl groups present on the nitrogen atoms contributed to a decrease in the C=O stretching frequency values. The frequencies of the C=O stretching modes have been correlated with the electron accepting ability of each solvent (represented by Gutmann electron acceptor numbers). The urea derivatives in the studied series exhibit similar behavior with respect to changing solvent environment despite the differences that exist among the ureas. These observations have been interpreted in terms of the structural characteristics of the ureas. 相似文献
Vibrational excitation and relaxation of five linear polyatomic molecules, OCS, OC3S, HC3N, HC5N, and SiC2S, have been studied by Fourier transform microwave spectroscopy in a supersonic expansion after the application of a low-current dc electric discharge. For each chain, the populations in bending and stretching modes have been characterized as a function of the applied discharge current; for stable OCS and HC3N, vibrational populations were studied as well in the absence of a discharge. With no discharge present the derived vibrational temperatures are slightly below T, the temperature of the gas before the supersonic expansion (i.e., 300 K). In the presence of the discharge, vibrational excitation occurs via inelastic collisions with the electrons and the vibrational temperatures rise as the applied current increases. Global vibrational relaxation is governed by rapid vibration-vibration (VV) energy transfer and slow vibration-translation (VT) energy transfer. The latter process is rate-determining and depends primarily on the wave number of the vibration. Vibrational modes with wave numbers near and below kT/hc (where T = 300 K and kT/hc-210 cm(-1)) are efficiently cooled by VT transfer because a sufficient number of collisions occur in the initial stages of the supersonic expansion. Vibrational modes with wave numbers around 450 cm(-l) appear to be inefficiently cooled in the molecular beam; at these energies VV and VT rates are probably comparable. For high-frequency vibrations, VV energy transfer dominates. For the longer chains OC3S and HC5N, higher-lying modes are generally not detectable and vibrational temperatures of most lower-lying modes were found to be lower than those of OCS and HC3N, suggesting that as the size of the molecules increases, intermode VV transfer becomes more efficient, plausibly due to the higher density of vibrational levels. New high resolution spectroscopic data have been obtained for several vibrationally excited states of OC3S, HC3N, and HC5N. Rotational lines of the 13C and 15N isotopic species of HC5N have been measured, yielding improved rotational and centrifugal distortion constants; 14N nitrogen quadrupole coupling constants for the isotopic species of HC5N with 13C have been determined for the first time. 相似文献