Interactions Of Ba2 Research Articles

Recent Advances in the Preparation of Barium Sulfate Nanoparticles: A Mini-Review

The potential for barium sulphate nanoparticles to be used in a variety of important fields has sparked a lot of attention. Methods for obtaining this material by milling (top-down approach) are not very popular due to the difficulty of controlling the size and shape of particles, as well as changes in their physicochemical properties during milling. More promising is the bottom-up approach, which is the interaction of Ba2+ and SO42− ions in a liquid environment. Direct precipitation is the simplest method; however, it does not allow control of the particle size. Microemulsions, microreactors membrane dispersion, as well as spinning disc reactors are used to overcome drawbacks of direct precipitation and allow control of particle size and shape. This is ensured mainly by intensive controlled micromixing of the precursors with concentrations close to saturated ones. The present review focuses on recent advances in the production of barium sulfate nanoparticles using various approaches, as well as their advantages and limitations. The issues of scaling up the techniques are also considered, and promising methods for obtaining BaSO4 nanoparticles are also discussed.

Specific coordination phenomena of alkaline earth metal ions with aromatic sulfonate ions in alcohols and binary solvents of acetonitrile–alcohols

The specific interactions between alkaline earth metal (Mg2+, Ca2+, or Ba2+) and p-toluenesulfonate (L−), 1,5-naphthalenedisulfonate (L2−), or 1,3,6-naphthalenetrisulfonate (L3−) ions (from the tetraethylammonium salt of L−, L2−, or L3−) have been examined by means of UV–visible spectroscopy in primary alcohols (from methanol to hexanol) as well as in the binary acetonitrile–alcohols (MeCN–MeOH, MeCN–EtOH), ethanol–methanol (EtOH–MeOH) and methanol–water (MeOH–H2O) solvents. The precipitation of non-charged species (e.g. ML0) and the successive re-dissolution of the precipitates, with increasing concentration of M(ClO4)2, have revealed the formation of cationic charged species or “reverse coordinated” species, M2L2+, even in the protic media as well as in the aprotic solvent MeCN. The solubility products (Ksp) and the “reverse coordination” constants (2M2++L2−⇆M2L2+, K2(−2)=[M2L2+]/[M2+]2 [L2−]) have been evaluated. In ethanol, both phenomena of the precipitation of ML0 and the successive re-dissolution to produce M2L2+ are observed for Ca2+ or Ba2+, but not for Mg2+. In butanol, the interaction between Mg2+ and the L2− causes the complete precipitation of MgL0 (pKsp=10.39) and also the successive re-dissolution of Mg2L2+ (log K2(−2)=8.08). Even in methanol, the interaction between Ba2+ and L2− results in precipitation (log Ksp=8.28) and the “reverse coordinated” species, Ba2L2+ (log K2(−2)=5.58). The interaction of Ba2+ with L− or L3− causes no precipitation in methanol; however, in all the other alcohols, it results both in precipitation (BaL2 or Ba3L2) and the “reverse coordinated” species, BaL+ or Ba2L+. The formulation for the formation constants (K2(−3)) for M2+ and L3− is newly presented and the constants (2Ba2++L3−⇆Ba2L+, K2(−3)=[Ba2L+]/[Ba2+]2 [L3−]) are evaluated in ethanol and propanol as well as in the binary EtOH–MeOH solvents, up to 70% (v/v) MeOH. The donicities toward M2+ of the media have been related to the pKsp and “reverse coordination” constants for L−, L2− and L3−.

Anomalous x-ray reflectivity characterization of ion distribution at biomimetic membranes.

Anomalous x-ray reflectivity measurements provides detailed information on ion binding to biomembrane surfaces. Using a monochromatic beam tuned to various x-ray energies at the Argonne National Laboratory Advanced Photon Source and utilizing a newly commissioned x-ray liquid surfaces reflectometer, measurements at and away from ion absorption edges allow determination of the distribution of these ions as they accumulate near lipid membranes. As a model, the interaction of Ba2+ ions with DMPA- (1,2-dimyristoyl-sn-glycero-3-phosphatidic acid) monolayers at the aqueous surface is studied. We find an unexpectedly large concentration of barium at the interface, approximately 1.5 per DMPA-, forming a Stern layer of bound ions and a cloud of less densely bound ions near the lipid headgroups. This result can be understood only if one assumes that bound cations are partially speciated, e.g., as BaOH+.

Current-noise analysis of the basolateral route for K+ ions across a K+-secreting insect midgut epithelium (Manduca sexta)

The isolated midgut of a lepidopteran larva (Manduca sexta), 5th instar was investigated with voltage-clamp and fluctuation analysis techniques. With high K+ insect saline on both sides the outward-directed short-circuit current (Isc) was carried by K+ (IK) from serosal to mucosal compartment. IK could be blocked, in a dose-dependent manner by serosal Ba2+ ions. There was no current with serosal Na+. Noise analysis of IK revealed a Lorentzian component in the power spectrum when Ba2+ was present in the serosal solution. The Ba2+/receptor kinetics show pseudo-first order characteristics only at low [Ba2+]s. For [Ba2+]s greater than KBa, the apparent Ba2+ association rate decreases with a hyperbolic course as a function of serosal [Ba2+] which could indicate some "substrate-inhibition"-like interaction of Ba2+ at its receptor site. It is concluded that the serosal membranes of the K+-secreting intestinal cells contain the common type of Ba2+-blockable K+ channel which provides the serosal pathway for K+ during secretion which is ultimately driven by the mucosally-located electrogenic K+-ATPase.

The mechanism of action of Ba2+ and TEA on single Ca2+-activated K+ -channels in arterial and intestinal smooth muscle cell membranes.

The interaction of Ba2+ and TEA with Ca2+-activated K+ channels was studied in isolated membrane patches of cells from longitudinal jejunal smooth muscle of rabbit and from guinea-pig small mesenteric artery (100 micron external diameter). Ba2+ applied from the inside of the membrane did not reduce unit current, except at high concentrations, but channels failed to open for long periods (s). This effect became much stronger when the potential gradient was in a direction driving Ba2+ into the channel and was reduced by increasing K+ ion concentration on the outside of the membrane. These results are consistent with Ba2+ entering the open channel and blocking at a site most of the way through the channel bore. In contrast, TEA and procaine dose-dependently reduced unit current amplitude at all patch potentials and slightly increased mean open time. Their effects were not detectably voltage-dependent and could be explained by TEA and procaine blocking the open channel with a timecourse that was faster than the frequency response of the recording system. The lack of appreciable voltage-dependence suggests that TEA and procaine bind to a site near to the inner mouth of the channel.