A theoretical description is presented for the critical effect of decrease of average cluster size in solutions when diluting with water. This effect, found experimentally for C
60
solutions in ...N-methylpyrrolidone, consists in an abrupt decrease in the size of clusters, when the volume fraction of added water is greater than a certain threshold value. This phenomenon is studied in the framework of the previously developed model of confined cluster growth based on kinetic nucleation theory. In this paper, the dilution effect is considered in a general sense and is explained using the power dependence of the saturation concentration of the system.
The work presents the results of studying the structure of binary liquid nanocarbon systems obtained by mixing hydrosol of detonation nanodiamond and aqueous dispersions of single layer graphene ...oxide flakes. We studied size and space distribution of nanocarbon clusters formed upon interaction of the components in aqueous media by mutually complement methods of small-angle X-ray and neutron scattering. The formation of small secondary agglomerates of nanodiamond particles on the surface of graphene oxide flakes was concluded and supported by the data of transmission electron microscopy from dried samples. The observed effect can significantly modify the structure of nanocarbon composites formed of nanodiamond and graphene oxide. The structural features of binary dispersions detonation nanodiamond–graphene oxide should be taken into account at the preparation of the conductive composites of reduced graphene oxide for energy storage systems.
Display omitted
•Structure of graphene oxide and nanodiamond dispersions as well as their mixtures were obtained by scattering techniques.•A two-dimensional structure of the single graphene oxide sheets in water was confirmed.•Binding nanodiamonds together with their homogeneous and random distribution along the graphene planes has been concluded.
The reaction of
N
-substituted amides of 3-amino-4,6-diarylthieno2,3-
b
pyridine-2-carboxylic acids with ninhydrin in the presence of catalytic amounts of sulfuric acid gave ...1′-spiroindene-2,2′-pyrido3′,2′:4,5thieno3,2-
d
pyrimidine-1,3,4′(3′
H
)-triones. Structure of a number of key compounds was studied using 2D NMR spectroscopy; the bioavailability parameters of the obtained compounds
in silico
were calculated. In a laboratory experiment, a moderate antidote effect was revealed with respect to the 2,4-D herbicide for one compound.
Crystal Structure of Magnesium Comenate Ivashchenko, L. I.; Kozin, S. V.; Vasil’eva, L. V. ...
Russian journal of coordination chemistry,
07/2023, Letnik:
49, Številka:
7
Journal Article
Recenzirano
The coordination compound Mg(HCom)
2
(H
2
O)
6
·2H
2
O (
I
) was obtained by the reaction of comenic acid (H
2
Com) with magnesium acetate in water. The formation of a new phase was confirmed by ...powder X-ray diffraction. The molecular formula of the compound was determined from energy dispersive X-ray fluorescence and thermogravimetry data. The thermo-oxidative stability of magnesium comenate was studied by simultaneous thermal analysis in air. The molecular structure of the complex was discussed on the basis of spectral data (NMR, IR, and UV spectroscopy) and studied in detail using X-ray diffraction (CCDC no. 2 207 835). Magnesium comenate crystallizes in the triclinic system, space group
P
the structure is stabilized by intra- and intermolecular hydrogen bonds between the coordinated water molecules, acid anions, and Mg(H
2
O)
6
2+
.
The reaction of 2,6-dichloro-4-methylnicotinonitrile with malononitrile dimer in the presence of triethylamine leads to regioselective nucleophilic substitution of the chlorine atom at position 6 ...with the formation of triethylammonium 2-amino-3-(6-chloro-5-cyano-4-methyl-pyridin-2-yl)-1,1,3-tricyanoprop-2-en-1-ide. The structure of the product was confirmed by spectral methods and X-ray diffraction analysis.
The reaction of 3-pentylpentane-2,4-dione with cyanothioacetamide afforded 4,6-dimethyl-5-pentyl-2-thioxo-1,2-dihydropyridine-3-carbonitrile. Alkylation of the latter led to the formation of ...2-alkylsulfanyl-4,6-dimethyl-5-pentylpyridine-3-carbonitriles or 3-amino-4,6-dimethyl-5-pentylthieno2,3-
b
pyridines, depending on the alkylating agent and reaction conditions. The structures of the key compounds were proved by 2D NMR spectroscopy and X-ray analysis. Biological activity of the synthesized compounds was evaluated
in silico
. Some compounds were experimentally found to stimulate growth of sunflower seedlings.
Highly stable and reproducible molecular-colloidal water solutions of C60 fullerenes (FWS) obtained by transferring fullerenes from an organic solution into an aqueous phase with the help of ...ultrasonic treatment are investigated by means of small-angle neutron scattering (SANS). A polydispersity in the size of detected particles up to 84 nm is revealed. These particles are slightly anisotropic and have a characteristic size of ∼70 nm. Along with it, there are some indications that a significant part of fullerenes composes particles with the size of the order of 1 nm. The contrast variation based on mixtures of light and heavy water shows that the mean scattering length density of the particles is close to that of the packed fullerene associates as well as that the characteristic size of possible fluctuations of the scattering length density within the particles does not exceed 2 nm. A smooth surface resulting in the Porod law for the scattering is detected. A number of models discussed in the literature are considered with respect to the SANS data.
Results of experiments on small-angle neutron scattering from ferrofluids on polar carriers (pentanol, water, methyl-ethyl-ketone), with double-layer sterical stabilization of magnetic nanoparticles, ...are reported. Several types of spatial structural organization are observed. The structure of highly stable pentanol-based samples is similar to that of stable ferrofluids based on organic non-polar carriers (e.g., benzene) with mono-layer covered magnetic nanoparticles. At the same time, the effect of the interparticle interaction on the scattering is stronger in polar ferrofluids because of the structural difference in the surfactant shell. The structure of the studied methyl-ethyl-ketone- and water-based ferrofluids essentially different from the previous case. The formation of large (>100 nm in size) elongated or fractal aggregates, respectively, is detected even in the absence of external magnetic field, which corresponds to weaker stability of these types of ferrofluids. The structure of the fractal aggregates in water-based ferrofluids does not depend on the particle concentration, but it is sensitive to temperature. A temperature increase results in a decrease in their fractal dimension reflecting destruction of the aggregates. In addition, in water-based ferrofluids these aggregates consist of small (radius ∼10 nm) and temperature-stable primary aggregates.
Small-angle neutron scattering is applied to study particle structure and interaction in ferrofluids on polar carriers such as pentanol (figure), water and methyl-ethyl-ketone.
A new time-of-flight neutron reflectometer GRAINS with a horizontal sample plane (vertical scattering plane) has recently been put into operation at the pulsed reactor IBR-2 (JINR, Dubna). The ...scattering geometry applied makes it possible to carry out complex studies of nanostructured interfaces in solid and liquid states by measuring the specular reflectivity and the intensity of diffuse scattering of thermal neutrons from open surfaces and hidden interlayer boundaries, including solid-liquid interfaces, over a wide momentum transfer range. The classical analysis of specular reflectivity allows one to determine the scattering length density profile in the object under study in a direction perpendicular to the interface for a thickness of ~100 nm with a resolution of 1 nm. The analysis of off-specular (diffuse) neutron scattering makes it possible to characterize lateral correlations on surfaces and interlayer boundaries. The paper summarizes the first experience in the operation of the GRAINS reflectometer. The instrument characteristics are presented together with the possibilities for experiments with solid and liquid samples illustrated with simple systems. Further steps for the development of the reflectometer are discussed.
