Choice of parameters and stability of nonlinear vibration isolation device

Work of active vibration isolation devices with single-mass electromagnetic suspension taking into account of real characteristics of the voltage regulators is described. The analytical researches are carried out; the areas of stability of work of nonlinear vibration isolation device are defined

Impact of polyelectrolyte coating in fluorescent response of Eu(III)-containing nanoparticles on small chelating anions including nucleotides

© 2014 Elsevier B.V. The present work introduces a novel route to sense the permeability of the polyelectrolyte layer deposited onto luminescent core. The use of ternary Eu(III) complexes as the luminescent core enables to detect the permeability of the polyelectrolyte layers through the change of the Eu(III)-centered luminescence. The chelating anions, such as adenosine phosphates, glutamic acid and ethylenediaminetetraacetic acid disodium salt were used as substrates. The origin of the fluorescent response is the complex formation of the substrates with the Eu(III) complexes, which is greatly affected by the equilibrium concentration of the substrates at the surface of the core. The latter in turn is influenced by the permeability of the polyelectrolyte layer. The obtained results highlight the impact of the nature of the exterior layer in the penetration of the substrates through the negatively and positively charged polyelectrolyte layers

Solubilization and acidic and receptor properties of calix[4]resorcinarenes in aqueous solutions of oxyethylated dodecanol Brij-35

Solubilization of calix [4]resorcinarenes (Cn) with a varied length of hydrophobic substituents (R =Me, Pr, C5H11, C 7H15, C9H19, and C 11H23) in aqueous solutions of oxyethylated dodecanol Brij-35 was studied by the solubility method and 1D and 2D 1H NMR spectroscopy. The solubilization of Cn in micellar solutions of Brij-35 is caused by the formation of mixed Cn-Brij-35 aggregates and is weakened substantially with the elongation of R. It was shown by pH-metry and 1D 1H NMR spectroscopy that the receptor properties of the Cn anions toward the tetramethylammonium cations in the mixed aggregates differ substantially from those for the monomeric molecules in aqueous-organic and aqueous solutions. In particular, the binding of the tetramethylammonium cations does not result in screening of their N-Me fragments with the cyclophane cavity of the receptor. © 2005 Springer Science+Business Media, Inc

Interfacial interactions of hard polyelectrolyte-stabilized luminescent colloids with substrates

© 2015 Elsevier B.V.. The present work introduces an origin of sensing function of polyelectrolyte-coated colloids based on Tb(III) complexes with calix[4]resorcinarene cavitand bearing four 1,3-diketone groups at the upper rim. The Tb(III)-centered luminescence of the colloids remains unchanged at pH 3-9, although the Tb(III) complexes are highly pH-dependent in DMF solutions. Both colloidal and luminescent properties of the colloids are stable within one month at least, which reveals stability of complex-based hard nanotemplates and soft polyelectrolyte deposition. The chelating substrates (catechol, tetracycline and fluoroquinolone derivatives) induce quick and reproducible luminescent response of the complex-based colloids without any detectable changes of their colloidal properties. The ternary complex formation at the interface of the colloids is the reason for their luminescent response on the substrates in aqueous solutions. Both the insolubility of the Tb(III)-containing cores and the shielding and/or buffer effect of the polyelectrolyte coating affect the interfacial complex formation, which results in more selective luminescent response of the colloids on the tetracycline and fluoroquinolone antibiotics in comparison with the complexes in solutions

Determination of fluoroquinolone antibiotics through the fluorescent response of Eu(III) based nanoparticles fabricated by layer-by-layer technique

The present work introduces the determination of fluoroquinolone antibiotics (FQs) in aqueous solutions through the fluorescent response of Eu(TTA)3 and [Eu(TTA)31] (TTA- and 1 are thenoyltrifluoroacetonate and phosphine oxide derivative) complexes encapsulated into the polyelectrolyte capsules fabricated through layer-by-layer deposition of poly(sodium 4-styrenesulfonate) (PSS) and polyethyleneimine (PEI). The variation of luminescent core, polyelectrolyte deposition and concentration conditions reveals two modes of fluorescent response on FQs of diverse structure namely the sensitization and quenching of Eu(III) centered luminescence. The obtained regularities reveal the ternary complex formation and the ligand exchange occurring at the interface of polyelectrolyte coated [Eu(TTA)31] based colloids as the reasons of the diverse fluorescent response of Eu(III) centered luminescence on FQs. The factors affecting the fluorescent response have been revealed, which are: the content of luminescent core, the mode of polyelectrolyte deposition, concentration and structure of FQs. The discrimination of moxifloxacin and lomefloxacin from levofloxacin, ofloxacin, difloxacin, perfloxacin through the quenching of Eu(III) luminescence in PSS-[Eu(TTA)31] colloids has been revealed. © 2013 Elsevier B.V

Water transverse relaxation rates in aqueous dispersions of superparamagnetic iron oxide nanoclusters with diverse hydrophilic coating

The article introduces transverse relaxation rates of water protons in the aqueous hydrophilic colloids synthesized on the basis of the oleate-coated iron oxide nanoparticles (17. nm) with non-ionic and cationic surfactants, triblock copolymers, polyethyleneimine (PEI) and 4,5-dihydroxybenzene-1,3-disulfoacid disodium salt (Tiron) as hydrophilic components. The IR spectroscopy, atomic force and transmission electron microscopy, along with dynamic light scattering data were obtained to evaluate the content of the hydrophilic coating, the clustering of iron oxide nanoparticles within the hydrophilic covering and the aggregation of hydrophilic nanoclusters. The analysis of the obtained results together with transverse relaxation rates under various concentration, counter-ion and temperature conditions reveals the particular importance of the water molecules diffusion in the outer hydrophilic layer versus the nearest to the iron oxide core layer. The obtained results reveal the counter ion binding with the charged hydrophilic iron oxide colloids as a route to affect the water transverse relaxation rates by biorelevant anionic substrates such as adenosine triphosphates. © 2013 Elsevier B.V

New calix[4]arene-based amides - Their synthesis, conformation, complexation

New chiral calix[4]arene-based diol-diamides 1a, 1b, tetraamides 2a, 2b and 7 as well as achiral diamide 3 and tetraamides 4-6 were prepared. The conformation of 1 has been studied in solution by NMR and in solid state by X-ray crystallography. The pinched-cone conformation of the calix[4]arene skeleton in 1 was found to be stabilized by a circular array of hydrogen bonds formed by two phenolic O-H and two amidic N-H bonds at lower rim. Whereas no significant complexation of Na+ was observed in solution for diamides 1 and 3, tetraamides 2, 4, 5, and 6 give strong complexes with Na+ as confirmed by NMR titrations of 2 and 4. The influence of anions and the solvents used on complexation ability of 2 towards Na+ is negligible

The effect of the core morphology of Eu(III)-doped nanoparticles on the ion exchange versus energy transfer between Eu(III) in the core and Cu(II) ions at the interface

The report represents the comparative analysis of luminescent properties of Eu(III) complex in colloids of silica-coated and layer-by-layer-fabricated nanoparticles. The diverse morphologies of these nanoparticles greatly affect their photophysical properties. The interfacial binding with d-ions exemplified by Cu(II) and the contributions of the ion exchange and energy transfer processes between Eu(III) ions confined within polymeric coating and Cu(II) ions at the interface of nanoparticles also depend on their morphology. The silica coating of Eu(III) complex does not prevent it from the efficient ion displacement by the interfacial Cu(II) ions, which results in the irreversible quenching of Eu(III)-centered luminescence. The lack of the ion exchange and the predominant energy transfer between Eu(III) ions in the core and interfacial Cu(II) ions are revealed in the colloids of Eu(III) complex reprecipitated from organic to aqueous solution and coated by the layer-by-layer-fabricated polyelectrolyte multilayer. The obtained results represent the synthetic route of the insertion of Cu(II) ions into the polyelectrolyte multilayer fabricated onto Eu(III) complex. © 2012 Springer Science+Business Media B.V

Tuning the non-covalent confinement of Gd(III) complexes in silica nanoparticles for high T<inf>1</inf>-weighted MR imaging capability

© 2016 Elsevier B.V.The present work introduces deliberate synthesis of Gd(III)-doped silica nanoparticles with high relaxivity at magnetic field strengths below 1.5 T. Modified microemulsion water-in-oil procedure was used in order to achieve superficial localization of Gd(III) complexes within 40–55 nm sized silica spheres. The relaxivities of the prepared nanoparticles were measured at 0.47, 1.41 and 1.5 T 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 49.6 mM−1 s−1 at 0.47 T 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 1.5 T, which along with low cytotoxicity effect make a good basis for their application as contrast agents