A synthetic scheme allowing the preparation of nanostructured organosilicon luminophores of branched or dendritic structure with up to 18 bithiophenesilane donor fragments and one central acceptor ...fragment has been elaborated. This universal scheme has been successfully upscaled to 20 g of the product, and its efficiency has been verified by the synthesis of two earlier unknown bithiophenesilane dendrimers with dense molecular shell and the central acceptor fragment, 1,4-bis(5-phenylthienyl-2-yl)benzene. The synthesis of more branched dendrimers under the Suzuki reaction conditions has led to the formation of the side products with the rupture of the Si–C(thiophene) bond, not typical of the synthesis of analogous compounds with lower branching degree under the same conditions.
Samples of single-crystal plates of
p
-terphenyl (3
Р
) and its derivative with terminal substituents–Si(CH
3
)
3
(
TMS
-3
P
-
TMS
), up to 25–30 mm in size and 400 μm thick, have been obtained for ...the first time by the solvent–antisolvent growth method. The crystal structure at temperatures of 293 and 85 K is refined for 3
Р
and solved (for the first time) for
TMS
-3
P
-
TMS
using X-ray diffraction. The habit of crystals and their surface morphology are investigated by methods of optical and laser confocal microscopy. The influence of substituent terminal groups -Si(CH
3
)
3
on the growth and structure of
TMS
-3
P
-
TMS
crystals is analyzed based on experimental data. The optical absorption and photoluminescence spectra of solutions and crystalline samples are investigated.
We present the status of research and development of a new highly efficient liquid scintillator based on linear alkylbenzene and organosilicon scintillation fluor, so called NOL (Nanostructured ...Organosilicon Luminophore). The measurements of the emission kinetics under irradiation by gamma-quanta and alpha-particles were performed. The results of long term stability measurements are decribed.
The process of the ultrasonic dispersion of hydroxyapatite nanoparticles in solutions of sodium hyaluronate is studied by ultraviolet (UV) spectrophotometry, dynamic light scattering, and viscometry. ...The optimum parameters (concentration of hydroxyapatite nanoparticles and solution of sodium hyaluronate, ratio of the components) which provide the formation of stable dispersions are determined. Film materials are obtained by casting, and the uniformity of distribution of the filler in the polymer matrix is assessed by UV spectrophotometry and microscopy.
A study was carried out on the preparation and properties of film materials obtained from hydroxyethylcellulose filled with micro- and nanocrystalline cellulose, which may hold promise for use as ...nonpolluting biodegradable coatings or films. We studied the effect of size (micro- or nanocrystalline cellulose), means of dispersion (mechanical stirring or ultrasonic treatment), and filler concentration on the deformation-strength properties of filled hydroxyethylcellulose films. The effect of the means of dispersion on the structure and properties of the matrix derived from two different types of hydroxyethylcellulose and on the efficiency of dispersion of the filler was studied by viscosimetry, UV spectrophotometry, and optical microscopy. Independently of the type of hydroxyethylcellulose, ultrasonic treatments leads to a reduction in the viscosity of their solutions and increase in optical transparency but the effect of such treatment has significantly different effects on the deformationstrength properties of both unfilled films and the films filled with micro- and nanocrystalline cellulose.
Materials in the form of thermally crosslinked films and macroporous hydrogels based on graft copolymers of chitosan with lactide oligomers of various stereochemical compositions synthesized by ...solid-state reactive extrusion are obtained and studied. It is shown that the chemical structure of the copolymers and the molecular weight of the initial chitosan significantly affect the morphology and properties of the materials. The heterogeneous morphology of materials based on the semicrystalline lactide oligomer leads to a decrease in the efficiency of crosslinking of the materials during heat treatment and a higher degree of moisture absorption of macroporous hydrogels.
The kinetics of the addition of carbosilane thiols of various structures to a hyperbranched polyallylcarbosilane matrix in
n
-hexane solution under direct photoinitiation is studied. A kinetic scheme ...that makes it possible to describe the photoaddition reaction at the quantitative level is proposed. The reaction rate constants are determined, and the dependence of the differential quantum yield of the photochemical reaction on the kinetic parameters and the concentration of allyl groups in the polyallylcarbosilane matrix is obtained. The assignment of the absorption bands to the corresponding components of the reaction system is confirmed by the quantum-chemical calculations of transition energies and oscillator strengths of the chromophore groups of thiols and the resulting thioesters. It is shown that the lowest rate of thiol-ene addition is observed for thiol with the smallest length of a polymethylene spacer between sulfur and silicon atoms.
A new high light yield liquid scintillator based on linear alkylbenzene (LAB) as an organic solvent and a novel nanostructured organosilicon liminophore as a scintillation fluor has been developed ...for the next generation large-scale experiments in astroparticle physics. It is shown that the developed liquid scintillator has light yield almost two times higher than traditional LAB-based liquid scintillator with PPO fluor, when peak light yield values are compared, since the former peaks at 490 nm, while the latter peaks at 360 nm. At the same time light emission kinetics is characterized by about 10 ns decay time constant for its fastest component which contributes more than 80% to the total light yield of the scintillator.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The results of studying the growth and structure of crystalline films of
para
-quaterphenyl derivative with terminal
n
-hexyl substituents—di-
n
-hexyl-
para
-quaterphenyl—are reported for the first ...time. The structure of crystalline films has been investigated using X-ray diffraction. It is found that crystalline films of di-
n
-hexyl-
para
-quaterphenyl, as well as crystals of unsubstituted
para
-quaterphenyl, are prone to outgrowth on a liquid–air interface in the form of a stack of parallel monomolecular layers with a thickness
d
001
= 3.05 nm. The optical absorption and photoluminescence spectra of solutions in
n
-hexane, toluene, and tetrahydrofurane, as well as crystalline samples, have been studied.
Silica nanoparticles (SNPs) with a diameter of 100 nm and surface-modified by covalently linked dibenzoylmethanatoboron difluoride have been synthesized and characterized. Suspensions of SNPs in ...dichloroethane are used as ink suitable for the microvalve ink-jet printing of sensing layers. It is demonstrated that SNP-based thin films are sensitive for methylbenzene vapors and could be a good candidate as a printed sensor. Responses of sensing films to methylbenzene vapors are analyzed using multivariate nonlinear regression.
