Svetlana Soloveva

Novel Highly Charged Silica-Coated Tb(III) Nanoparticles with Fluorescent Properties Sensitive to Ion Exchange and Energy Transfer Processes in Aqueous Dispersions

Novel silica-coated Tb(III) nanoparticles with high luminecsence were synthesized using the reverse microemulsion procedure. The quenching of luminescent properties of these nanoparticles can be achieved by ion exchange and energy transfer mechanisms. The quenching through the ion exchange of Tb(III) by H+ or La(III) is time dependent, indicating that the ion exchange is probably diffusion controlled. The quenching by Co(III) complex cations is achieved by the energy transfer mechanism and thus is not time dependent. The analysis of quenching data in Stern-Volmer cooordinates reveal the negative charge of the silica-coated Tb(III)-TCAS nanoparticles and several types of luminophoric species, located within the core and close to the surface of silica nanoparticles.

Solution behavior of mixed systems based on novel amphiphilic cyclophanes and Triton X100: Aggregation, cloud point phenomenon and cloud point extraction of lanthanide ions

Aggregation and cloud point (CP) behavior, as well as CP extraction of lanthanide ions have been studied for novel non-ionic cyclophanic surfactants with the varied length of polyoxyethylene and hydrophobic moieties (CnEm) based on calix[4]arene platform in their mixtures with Triton X100 (TX100). The dynamic light scattering data reveal the contribution of the large size lamellar or stack like mixed aggregates in CnEm-TX100 solutions. Aggregation and CP behavior of TX100-CnEm mixed solutions are quite different from those of conventional non-ionic surfactants. The effect of the hydrophobic substituents and polyoxyethylene chains length of CnEm on the CP extraction of La(III), Gd(III) and Lu(III) in the mixed TX100-CnEm micellar solutions is discussed in the correlation with their aggregation and cloud point behavior. The obtained data elucidate the cyclophanic structure of CnEm as the key reason of the formation of large lamellar-like aggregates with TX100, exhibiting the unusual CP behavior and CPE efficiency.

Tuning the non-covalent confinement of Gd(III) complexes in silica nanoparticles for high T1-weighted MR imaging capability

The present work introduces deliberate synthesis of Gd(III)-doped silica nanoparticles with high relaxivity at magnetic field strengths below 1.5T. Modified microemulsion water-in-oil procedure was used in order to achieve superficial localization of Gd(III) complexes within 40-55nm sized silica spheres. The relaxivities of the prepared nanoparticles were measured at 0.47, 1.41 and 1.5T with the use of both NMR analyzer and whole body NMR scanner. Longitudinal relaxivities of the obtained silica nanoparticles reveal significant dependence on the confinement mode, changing from 4.1 to 49.6mM-1s-1 at 0.47T when the localization of Gd(III) complexes changes from core to superficial zones of the silica spheres. The results highlight predominant contribution of the complexes located close to silica/water interface to the relaxivity of the nanoparticles. Low effect of blood proteins on the relaxivity in the aqueous colloids of the nanoparticles was exemplified by serum bovine albumin. T1- weighted MRI data indicate that the nanoparticles provide strong positive contrast at 1.5T, which along with low cytotoxicity effect make a good basis for their application as contrast agents.

Mannich Reaction as a Convenient Route to New Macrocyclic Compounds Containing an Uracil Fragment

Mannich reaction of 1,3-bis[4-(2-mercaptomethylphenoxy)butyl]-6-methyl-1,2,3,4-tetrahydropyrimidine-2,4-dione, formaldehyde, and N-benzylamine afforded a 24-membered macrocyclic compound containing an uracil fragment, 1,3-(11-benzyl-6,7:15,16-dibenzo-5,17-dioxa-9,13-dithia-11-aza-6,15-heneicosadiene-1,21-diyl)-6-methyl-1,2,3,4-tetrahydropyrimidine-2,4-dione.

Guest-induced conformation shift of p-sulphonatothiacalix[4]arene in the solid state and solution manipulated by [Zn(dipy)3]2+

The 1H NMR and X-ray analysis data reveal the guest-induced cone → partial cone and cone → 1,2-alternate conformational shift in aqueous methanol solutions and solid state for a p-sulphonatothiacalix[4]arene-[Zn(dipy)3]2+ host–guest system. The experimental data, together with DFT calculations, show that the guest-induced conformational shift of p-sulphonatothiacalix[4]arene is facilitated by the deprotonation of phenolic groups.