Yuri N. Osin

Methylviologen mediated electrosynthesis of gold nanoparticles in the solution bulk

Electrosynthesis of gold nanoparticles (AuNp) was carried out by methylviologen mediated reduction of Au(I) at potentials of the MV2+/MV˙+ redox couple in water/0.1 M NaCl medium, in the absence and in the presence of stabilizers. In all the cases, AuNp are formed in the solution bulk and are not deposited on the cathode. In the absence of stabilizers, AuNp (14–100 nm) coalesce to give aggregates of various shapes that eventually form a deposit. Sonication reversibly destructs the deposit into nanoparticles. In the presence of alkylamino-modified silicate nanoparticles (SiO2–NHR, 120–160 nm), spherical AuNp (≤20 nm) are bound as inclusions in the SiO2–NHR surface layer. Polyvinylpyrrolidone (40 000 D) stabilizes spherical AuNp with a mean diameter of 5–14 nm. All the particles were characterized by electron microscopy methods (SEM, STEM) and X-ray powder diffraction (XRPD).

Novel amphiphilic conjugates of p-tert-butylthiacalix[4]arene with 10,12-pentacosadiynoic acid in 1,3-alternate stereoisomeric form. Synthesis and chromatic properties in the presence of metal ions

For the first time amphiphilic receptors based on the 1,3-alternate stereoisomeric form of thiacalix[4]arene, bearing carboxyl/sulphonate polar headgroups on one side and 10,12-pentacosadiynoic acid (PCDA) residues on another side of the macrocyclic plane, were synthesized. It was shown that embedding of synthesized macrocycles in PCDA vesicles results in stable colloids with a size around 300 nm. The temperature of ultrasonication before UV irradiation has a critical impact on the packing of vesicles for better polymerization. The increase of calixarene content in PCDA vesicles causes a decrease in the degree of PCDA polymerization. Nevertheless, calixarene additives dramatically change the colorimetric response of photopolymerized PCDA vesicles toward metal ions. Vesicles with 10 mol% content of calixarene have significant colorimetric response toward lanthanide ions with a detection limit up to 8 μM. The colorimetric response in the series of lanthanide ions depends on the ionic radius, and the greatest response was found for the largest La(III) ion. It was found that binding of calixarene–PCDA vesicles with lanthanide ions results in the formation of large 1 μm aggregates followed by sedimentation. Thus, the mechanism of colorimetric response of calixarene-decorated polydiacetylene vesicles toward lanthanide ions includes the distortion of the calixarene cavity provoking perturbation of the PDA backbone accompanied by metal-induced aggregation of functionalized vesicles with sedimentation of particles. Therefore, calixarene–PCDA vesicles have great potential for the future design of bifunctional colloids with sensor and separation applications.

Investigation of DNA binding abilities of solid lipid nanoparticles based on p-tert-butylthiacalix[4]arene platform

An amphiphilic thiacalix[4]arene derivative functionalized with guanidinium groups forms stable solid lipid nanoparticles (SLNs) with high ζ-potential in water. Applying gel electrophoresis and fluorescent spectroscopy methods shows that the SLNs have high binding affinity to double-stranded DNA, but despite this fact, we have not observed any significant transfection activity toward three different mammalian cell lines. A UV-spectroscopic study reveals that interaction between the SLNs and the polynucleotide leads to partial denaturation of the DNA located on the surface of the nanoparticles that can hinder transfection.

p-tert-Butylthiacalix[4]arenes equipped with guanidinium fragments: aggregation, cytotoxicity, and DNA binding abilities

Mono-, di- and tetracationic thiacalix[4]arenes in a 1,3-alternate conformation functionalized with guanidinium groups showed a strong dependence of the aggregation properties with the ratio of guanidinium/n-decyl fragments attached to phenolic groups. Increasing the amount of guanidinium fragments improved the macrocycles solubility in water as well as the sorption capacity towards polynucleotide molecules. The synthesized thiacalixarenes showed relatively high toxicity comparable with that for similar receptors based on the classical calixarene.

Heavy oil oxidation in the nano-porous medium of synthetic opal

Increasing interest to study hydrocarbon behavior in fine porous media, awakened by the shale revolution, requires the application of suitable model porous media. In the current study we prepared nano-porous synthetic opal, profoundly investigated its morphological and textural properties, and studied the kinetics of combustion of heavy oil impregnated into nanopores. Comparison of kinetic parameters of the oil oxidation process for nano-porous and coarse-porous media revealed that nanoconfinement affects the reactivity of oil.

Self-assembly of chiral fluorescent nanoparticles based on water-soluble L-tryptophan derivatives of p-tert-butylthiacalix[4]arene

New water-soluble tetra-substituted derivatives of p-tert-butylthiacalix[4]arene containing fragments of L-tryptophan in cone and 1,3-alternate conformations were obtained. It was shown that the resulting compounds form stable, positively charged aggregates of 86–134 nm in diameter in water at a concentration of 1 × 10−4 M as confirmed by dynamic light scattering, scanning electron microscopy and transmission electron microscopy. It was established that these aggregates are fluorescently active and chiral. A distinctive feature of the compounds is the pronounced dependence of their spectral (emission and chiroptical) properties on the polarity of the solvent and the length of the linker between the macrocyclic and fluorophore parts of the molecule.