Synthesis of Stable Aqueous Ceria Sols and Study of Their Toxicity

Cerium dioxide is a unique material which is promising for biomedical applications. The properties of ceria are definitely determined by synthesis procedure and further treatment conditions. The vast majority of currently existing methods of synthesis lead to formation of CeO2 in the form of nanopowders, but in some cases (e.g., in biological applications), such powders can not be used because they do not quite satisfy practical requirements. So, in this work we succeed in synthesis of ceria-stable sols with controlled small particle size (2-4 nm) using an inexpensive and facile method and investigated the effect of changing the concentrations and the molar ratio of initial reagents on particle size of CeO2. In this paper we also propose a method of evaluation of toxicity of ceria sols using bioluminescent microorganism Vibrio fischeri. According to the results obtained CeO2 sols of different concentrations (6.3*10-4 – 0,02M) are not toxic to Vibrio fischeri. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3495

Selenic acid anodizing of aluminium for preparation of 1D photonic crystals

Anodizing of aluminium under oscillating conditions is a reproducible, scalable, and low-cost method for the preparation of one-dimensional photonic crystals with photonic band gaps in the visible and near-infrared regions. For this purpose, sulfuric and oxalic acid electrolytes are used, because in such baths transparent anodic alumina films are formed. In the present study, selenic acid electrolyte is utilized for the fabrication of anodic alumina photonic crystals for the first time. The choice of a rational range of voltage/current modulation is performed on the basis of linear voltammetry. The dispersion of the effective refractive index and the porosity of prepared photonic crystals are measured. High transmittance of the anodic alumina obtained in selenic acid electrolyte makes this bath promising for the preparation of 1D photonic crystals with photonic band gaps from the ultraviolet to infrared regions. Keywords: Selenic acid, Anodization, Anodic alumina, One-dimensional photonic crystal, Q-factor, Refractive inde

First rare-earth phosphate aerogel: sol–gel synthesis of monolithic ceric hydrogen phosphate aerogel

Since the late 1960s, ceric hydrogen phosphates have attracted the attention of scientists due to remarkable ion exchange, sorption, proton-conduction and catalytic properties. In this work, through the application of various solvents, we, for the first time, have obtained monolithic aerogels based on ceric hydrogen phosphates with high porosity (~99%) and extremely low density (~10 μg/cm3). The composition and structure of aerogels were thoroughly studied with XRD, TEM, SEM, XPS, low temperature nitrogen adsorption methods, TGA/DSC, Fourier-transform infrared spectroscopy (FTIR) and small-angle neutron scattering (SANS). The aerogels were found to belong to the fibrous macroporous aerogels family

Аэрогели на основе SiO₂, модифицированные ковалентно связанными ароматическими кислотами, как потенциальные системы доставки лекарственных препаратов

Hybrid aerogels (AGs) containing NH2-group were acylated by benzoic and salicylic acids. The acylated AGs had the specific area value of 170-220m2/g and were not deacylated in H2O-iPrOH mixture at 37°С during 24h. In 0.5% HCl at 37°С hydrolysis takes place releasing free acids and giving the possibility to use aminoaerogels as drug delivery system.Гибридные аэрогели (АГ), полученные согелированием тетраметоксисилана (ТМОС) и 3-аминопропилтриметоксисилана (АПТМС) в мольном соотношении ТМОС:АПТМС=4:1, были модифицированы путём ацилирования аминогруппы остатками бензойной и салициловой кислот. Удельная площадь поверхности модифицированных образцов составила 170-220 м2/г. Показано, что выдерживание АГ в водно-изопропанольном растворе при 37°С в течение 24 ч не приводило к высвобождению свободных кислот в раствор, в то время как в 0.5% HCl при 37°С происходил гидролиз амидной связи с образованием свободных кислот. Данный результат позволяет предположить, что АГ, модифицированные остатками биологически активных органических кислот, могут быть использованы для медленного высвобождения лекарственных препаратов в организме

Superhydrophobic and luminescent highly porous nanostructured alumina monoliths modified with tris(8-hydroxyquinolinato)aluminium

International audienceA straightforward and facile procedure for the fabrication of superhydrophobic luminescent 3D nanomaterials was developed. Chemical modification of ultra-lightweight highly porous nanostructured aluminum oxyhydroxide (NOA) monoliths in 8-hydroxyquinoline vapors resulted in the formation of tris(8–hydroxyquinoline) aluminum on the surface of NOA nanofibrils. The original shape and size of the initial NOA monolith and its internal 3D nanostructure were completely preserved during the modification. Surface modified NOA samples demonstrated intense green luminescence as well as superhydrophobicity, the water contact angle being ~153°, the sliding angle ~6° and contact angle hysteresis ~8°. We believe that an unusual combination of properties inherent in the synthesized material will be advantageous for the design of water-proof self-cleaning photonic devices

The first amorphous and crystalline yttrium lactate: Synthesis and structural features

The synthesis and crystal structure of the first molecular yttrium lactate complex, Y(Lac)3(H2O)2, is reported, where the coordination sphere of yttrium is saturated with lactate ligands and water molecules, resulting in a neutral moiety. In Y(Lac)3(H2O)2, hydrogen bonding between α-hydroxy groups and water molecules allows for the formation of 2D layers. A subtle variation in synthetic conditions, i.e. a slight increase in pH (5.5 instead of 4.5) promoted the formation of a semi-amorphous fibrous material with a presumed chemical composition of Y4(OH)5(C3H5O3)7·6H2O. The flattened fibres in this material are responsible for its good flexibility and foldability

Unexpected Effects of Activator Molecules’ Polarity on the Electroreological Activity of Titanium Dioxide Nanopowders

Titanium dioxide nanoparticles, obtained using the sol–gel method and modified with organic solvents, such as acetone, acetonitrile, benzene, diethyl ether, dimethyl sulfoxide, toluene, and chloroform, were used as the filler of polydimethylsiloxane-based electrorheological fluids. The effect of electric field strength on the shear stress and yield stress of electrorheological fluids was investigated, as well as the spectra of their dielectric relaxation in the frequency range from 25 to 10⁶ Hz. Modification of titanium dioxide by polar molecules was found to enhance the electrorheological effect, as compared with unmodified TiO₂, in accordance with the widely accepted concept of polar molecule dominated electrorheological effect (PM-ER). The most unexpected result of this study was an increase in the electrorheological effect during the application of nonpolar solvents with zero or near-zero dipole moments as the modifiers. It is suggested that nonpolar solvents, besides providing additional polarization effects at the filler particles interface, alter the internal pressure in the gaps between the particles. As a result, the filler particles are attracted to one another, leading to an increase in their aggregation and the formation of a network of bonds between the particles through liquid bridge contacts. Such changes in the electrorheological fluid structure result in a significant increase in the mechanical strength of the structures that arise when an electric field is applied, and an increase in the observed electrorheological effect in comparison with the unmodified titanium dioxide