Luminescent calcium carbonate micro ‘bow ties’

Calcium carbonate (CaCO3) is a ubiquitous material which has been studied for centuries due to its integral nature across various fields and its vast range of applications. Here we report, for the first time, a low temperature dry ice carbonation method for the production of unique rare earth-doped calcium carbonate ‘bow ties’. CaCO3 exhibits retrograde solubility, an interesting property in which its solubility increases with decreasing temperature. In this synthesis, dry ice acts not only as a CO2 source, but as a coolant, increasing the solubility of CaCO3 and CO2 and allowing specific growth to occur. The incorporation of trivalent lanthanide ions Eu3+ and Tb3+ into the CaCO3 synthesis results in the formation of these unique luminescent calcite ‘bow tie’ microstructures which cannot be produced using either standard gaseous CO2 carbonation, or chemical precipitation methods. This new method and materials might find potential applications including, but not limited to, radionuclide sequestration, imaging and photonics

Influence of Indifferent Electrolytes on Formation of Coagulative Structures in Aqueous Silica Dispersions

Effects of indifferent electrolytes (NaCl, KCl, LiCl, NaI, NaNO3, CaCl2, and MgCl2) on the electrical double layer (EDL), aggregation, gelling, and rheological properties of aqueous dispersions of nanosilica were investigated. All examined indifferent electrolytes enhance interactions between nanoparticles of fumed silica through the coagulation mechanism. The critical concentration of gelation and gelling time decrease in the presence of the electrolytes, while the effective viscosity of the dispersions and average size of aggregates (Def) increase in series of chlorides: Li+ < Na+ < K+ < Ca2+ < Mg2+. That corresponds to an increase in the cation radius and reduction of the hydration shell. The nature of anions and cations significantly affects the values of Def and viscosity. For sodium salts, the viscosity increases in series I- < NO3- < Cl- corresponding to an increase in the hydration shell

A Computational Method for Combustion in High Speed Flows

A two-dimensional time-accurate numerical model to simulate complex reacting flowfields in chemical non-equilibrium is presented. The aim of this studyis to develop a computational tool which permits the analysis and the easy implementation of combustion phenomena for high speed flows. To construct an efficient numerical tool, while maintaining a reasonable accuracy, a semi-implicit numerical method was selected and verified for a hydrogen-air mixture. The numerical approach is based on a time-dependent, finite-volume integration of the governing equations suitably modified for chemical non-equilibrium. The evaluation of the reacting constants based on Gibbs free energy and the Van't Hoff equation allows a very easy implementation of the chemical model used, regardless of its complexity. Calculations were performed with adeguate temporal and spatial resolution for modeling the physical process for pratical calculation. Comparisons with numerical results are used for a verification of the numerical procedur

Геометричне та механо-сорбційне модифікування високодисперсного кремнезему в умовах газового дисперсійного середовища

Methods of geometric and solvate-stymulated mechano-sorption-activated modification of fumed nanosilica in the gaseous dispersion media were developed and used to prepare functionalyzed nanofillers for polymeric systems. Non-volatile high- and low-molecular weight compounds (such as polymers, organic bioactive compounds, organic and inorganic salts) can be used as modifiers of nanofillers.Були описані геометричне та сольвато-стимульоване механосорбційне модифікування високодисперсного кремнезему в умовах газового дисперсійного середовища. Такі способи модифікування дозволяють одержувати функціоналізовані наповнювачі полімерних систем на основі нанорозмірного кремнезему. Для модифікування можна використовувати нелеткі високо- та низькомолекулярні органічні сполуки – полімери, біологічно активні сполуки, органічні солі, а також неорганічні солі

Photocatalytic Properties of Sn-doped TiO2

The synthesis of Sn-doped titania nanoparticles (Sn content of 0, 3, 6, and 12 at. %) was carried out using solgel chemical route based on the common acid hydrolysis of titanium and tin tetrachlorides. Phase composition, morphology, particle size, pore size distribution and photocatalytic performance of obtained materials were systematically studied by various analytical techniques (XRD, HR-TEM, low-temperature nitrogen adsorption porosimetry, UV-Vis spectroscopy). An increase in the Sn dopant concentration causes a gradual decrease in the relative content of the anatase phase from 100 mol. % for undoped titania to about 3 mol. % for material with maximal doping concentration. Materials with a Sn atomic content of 3 and 6 at. % have the maximum values of the specific surface area (about 280-290 m2/g) that corresponds to the smallest (approximately 2.5 nm) anatase crystallite. The photocatalytic activity of the synthesized Sn-doped TiO2 nanoparticles was analyzed by the method of methylene blue dye photodegradation in an aqueous solution under UV irradiation. The highest reaction rate constant and maximal methylene blue dye adsorption capacity were obtained for 3 at. % Sn-doped titania with the mixed anatase/rutile composition. The indirect optical transitions are characteristic for all synthesized materials. A decrease in the bandgap energy values with increasing Sn content from 3.21 eV for pure anatase to 2.82 eV for titania doped with 12 at. % of the Sn was observed. The growth in photocatalytic activity for the mixed-phase sample can be considered as a result of the increasing number of surface active centers due to the anatase-rutile phase transition

Multifactorial determinants that govern nanoparticle uptake by human endothelial cells under flow

Vascular endothelium is a potential target for therapeutic intervention in diverse pathological processes, including inflammation, atherosclerosis, and thrombosis. By virtue of their intravascular topography, endothelial cells are exposed to dynamically changing mechanical forces that are generated by blood flow. In the present study, we investigated the interactions of negatively charged 2.7 nm and 4.7 nm CdTe quantum dots and 50 nm silica particles with cultured endothelial cells under regulated shear stress (SS) conditions. Cultured cells within the engineered microfluidic channels were exposed to nanoparticles under static condition or under low, medium, and high SS rates (0.05, 0.1, and 0.5 Pa, respectively). Vascular inflammation and associated endothelial damage were simulated by treatment with tumor necrosis factor-α (TNF-α) or by compromising the cell membrane with the use of low Triton X-100 concentration. Our results demonstrate that SS is critical for nanoparticle uptake by endothelial cells. Maximal uptake was registered at the SS rate of 0.05 Pa. By contrast, endothelial exposure to mild detergents or TNF-α treatment had no significant effect on nanoparticle uptake. Atomic force microscopy demonstrated the increased formation of actin-based cytoskeletal structures, including stress fibers and membrane ruffles, which have been associated with nanoparticle endocytosis. In conclusion, the combinatorial effects of SS rates, vascular endothelial conditions, and nanoparticle physical and chemical properties must be taken into account for the successful design of nanoparticle–drug conjugates intended for parenteral delivery

Ecologically Friendly Polymer-Metal and Polymer-Metal Oxide Nanocomposites for Complex Water Treatment

Peer ReviewedPostprint (published version