Towards development of colorimetric test-systems for phenols detection based on computationally-designed molecularly imprinted polymer membranes

Colorimetric test-system for the express-control of phenols content in water was developed. The system consisted of free-standing molecularly imprinted polymer (MIP) membranes which contained synthetic binding sites capable of phenol binding. The MIP membranes were obtained by co-polymerisation of a functional monomer (e.g. itaconic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, acrylamide or methacrylic acid) with triethyleneglycoldimethacrylate and oligourethaneacrylate. Rational choice of the functional monomers was based on the results of computational modelling. The phenol-selective MIP membranes were used as a basis for the colorimetric test-system for measuring phenol in aqueous samples. Phenol molecules were selectively adsorbed by the MIP membranes and quantified using color reaction with 4-aminoantipyrine. The intensity of the membranes' staining was proportional to the phenol concentration in the analysed sample. The optimised colorimetric test-system based on MIP membranes demonstrated a low detection limit (50 nM), a wide working range — 50 nM–0.5 mM and an excellent storage stability at room temperature (12 months). As compared to the traditional methods of phenols detection the developed test-system is superior because of simplicity of operation, small size and low cost.     

The structure and electrical properties of lithium doped pyrochlore Gd2Zr2O7

The lithium-doped phases Gd_1.7Li_0.3Zr₂O_6.7 and Gd₂Zr_1.7Li_0.3O_6.55 with a pyrochlore structure were prepared by the modified Pechini method using citric acid and glycerol. Monitoring of the lithium content by using a nuclear microanalysis showed that a significant loss of lithium occurred after heat treatment above 1200 °C. Dense ceramics with a stoichiometric lithium content can be prepared by a low temperature microwave sintering (1100 °C). The introduction of lithium in the Gd-sublattice was accompanied by a decrease in the unit cell parameter (a = 10.5208 (1) Å vs 10.5346 (2) Å for Gd₂Zr₂O₇) and during doping at the Zr-sites with lithium, the cell parameter increased (10.5720 (1) Å). The doping in both cases led to an increase in the free cell volume. The impedance spectroscopy results showed that the bulk conductivity can be enhanced by the Li⁺-doping at the Gd³⁺-site by almost an order of magnitude. The sample Gd₂Zr_1.7Li_0.3O_6.55 had a conductivity lower than that of Gd_1.7Li_0.3Zr₂O_6.7 due to the possible trapping of oxygen vacancies by a high-charged acceptor defect LiZr???. The conductivity?pO₂ measurements showed that the Li-containing phase was a pure oxide-ion conductor at T < 800 °C.     

Corrosion Protection of Carbon Steel by a Composition Based on Natural Polysaccharide

Materials Science - It is shown that xanthan gum inhibits corrosion processes in carbon steel placed in chloride-containing media by the mechanism of adsorption. Potassium-sodium tartrate improves...     

Influence of the Dispersion Hardening with Nanooxides on the Corrosion Resistance of High-Entropy Alloys of the Cr–Fe–Mn–Ni System in Lead Melts

Materials Science - We study the corrosion resistance of high-entropy alloys of the Cr–Fe–Mn–Ni system in lead melts at 480°С in testing for up to 1000 h. It is shown...