4 research outputs found
Signs of the legal regulation of bodies supporting enforcement of economic and other courts in the Soviet period
У статті визначено характерні ознаки правового регулювання діяльності органів, що забезпечували виконання рішень арбітражних та інших судів у радянський період. Названо основні нормативні акти радянського періоду. Виділено характеристики, що можна буде використати при модернізації сучасного українського законодавства.Typical signs of legal regulation of the authorities activities, which ensured enforcement of decisions arbitration and other courts in the Soviet period, have been identified in the article. The basic regulations acts of the Soviet period were identified. Characteristics, that can be used in modernization Ukrainian modern legislation, were allocated
Improved Stability of “Naked” Gold Nanoparticles Enabled by in Situ Coating with Mono and Multivalent Thiol PEG Ligands
Unprotected (“naked”)
gold nanoparticles with high
monodispersity (⟨<i>d</i>⟩, 5.5± 0.5
nm) were obtained in a facile and single-step microwave-assisted hydrolytic
decomposition of the molecular precursor [NMe<sub>4</sub>][Au(CF<sub>3</sub>)<sub>2</sub>]. Given their chloride-free surface chemistry,
the as-obtained gold nanoparticles were in situ functionalized with
mono-, di-, and trivalent thiolated PEG ligands in order to study
the influence of multivalent character of the ligands on the stability
of the colloidal solutions. For this purpose, a novel tridentate ligand
was synthesized and the previously reported syntheses of mono- and
divalent thiol ligands were improved. Owing to the pristine character
of the Au nanoparticles no ligand exchange was required, and the colloidal
and chemical stability of the mono- and multivalent functionalized
particles purely depended on the ligating ability of the thiolated
groups. In situ-functionalized Au nanoparticles showed a strikingly
(2 orders of magnitude higher) improved stability against small nucleophiles
such as sodium cyanide compared to gold nanoparticles coated with
citrate ligands and functionalized via a ligand-exchange reaction.
The monovalent thiol PEG ligand produced most stable colloids against
cyanide, which is explained by a strongly increased numerical ligand-density
on the surface. Gold colloids stabilized by di- and trivalent ligands
exhibited high stability in aqueous solutions with high NaCl concentrations
(2 M) in contrast to those functionalized with the monovalent PEG
ligand, which were only temporally stable in dilute NaCl solutions.
The beneficial effect of the multivalence of the ligands was further
demonstrated by the incorporation of an additional chelating ligand
(dithiothreitol) to the colloidal dispersions
Structural Characterization of Ordered, Non-Close-Packed Functionalized Silica Nanoparticles on Gold Surfaces
Nanostructured surfaces
play an important role in modern science
and technology. In particular, ordered arrangements of nonclose-packed
nanoparticles created by self-assembly offer a versatile route to
prepare systems, which can be used in various applications such as
sensing, plasmonic devices or antireflection coatings. Self-assembly
based systems are particularly appealing as preparation is rather
simple. The ability of nanoparticle systems to form nonclosed packed
monolayers by self-assembly depends on the balance of various energetic
contributions in particular the adsorption energy, the lateral barrier
for diffusion and the repulsion between particles. Even for simple
model systems such as the monodispersed silica particles adsorbed
on a bare gold surface investigated here, none of these quantities
is easy to determine experimentally. To this end, we will report on
a detailed characterization of the adsorption in particular with respect
to the structural properties of the above-mentioned model system.
Based on experimental results obtained by using quartz crystal microbalance
with dissipation monitoring (QCM-D) as well as scanning electron microscopy
(SEM) it is possible to determine the electrostatic pair potential
from the lateral arrangement of the nano particles in the limit of
low coverage
Local Magnetic and Electronic Structure of the Surface Region of Postsynthesis Oxidized Iron Oxide Nanoparticles for Magnetic Resonance Imaging
Iron
oxide nanoparticles (FeO<sub><i>x</i></sub>-NP) are applied
in medicine as contrast agents in magnetic resonance imaging (MRI)
where they reduce the spin–spin relaxation time (T<sub>2</sub>-time) of absorbing tissue. Hence, control of their magnetic properties
is essential for these applications. Magnetic properties strongly
depend on the particle size and shape as well as the surface functionalization
of the iron oxide nanoparticles. Especially, structural and magnetic
disorder in the region close to the surface (1–2 nm) lead usually
to a reduced magnetization compared to the corresponding bulk material.
Therefore, X-ray magnetic circular dichroism (XMCD) in the total electron
yield (TEY) mode is used to investigate local magnetic and electronic
properties of the surface region of monodisperse, spherical FeO<sub><i>x</i></sub>-NPs (Fe<sub>3</sub>O<sub>4</sub>/γ-Fe<sub>2</sub>O<sub>3</sub>) before and after the postsynthetic treatment
in oxygen-rich environment. Charge transfer multiplet calculations
of the XMCD spectra are performed to analyze the contributions of
Fe<sup>2+</sup> and Fe<sup>3+</sup> at different lattice sites, i.e.,
either in octahedral or tetrahedral environment. The analysis of the
XMCD data reveals that both, the magnetization of the nanoparticle
surface region as well as their maghemite to magnetite ratio, are
strongly increased after tempering in an oxidative environment, which
likely causes rearrangement of their crystalline order. The magnitude
and the kinetics of these variables depend strongly on the particle
size. In addition, after thermal annealing a reduced spin canting
is extrapolated from the lower magnetic coercivity, which confirms
that a structural rearrangement takes place