Influence of surface properties of the titanium dioxide porous films on the characteristics of solar cells

Porous films formed by cylindrical geometrically anisotropic fragments of TiO₂ have been produced by electrochemical anodization of titanium. The specific surface area and pore volume of the samples were determined by the BET method. It is shown that the samples have a bimodal pore-size distribution with maxima depending on the anodization voltage: by increase in voltage the inner diameter of the cylindrical pores grows, which leads to a decrease in the specific surface area. Dye sensitized solar cells were assembled on the basis of the obtained materials to study the effect of certain characteristics on the efficiency of solar energy conversion. The electrical transport properties of the films were studied by impedance spectroscopy.     

Functional copolymers with triazole and acetate fragments

New functional copolymers of different composition with triazole and acetate fragments in the macromolecules were synthesized by free radical copolymerization of 1-vinyl-1,2,4-triazole with vinyl acetate. The reactivity of the comonomers was studied and the monomer copolymerization constants were calculated. The structure and composition of the copolymers were determined by elemental analysis, IR and ¹H NMR spectroscopy.     

Fe-containing nanocomposites based on a biocompatible copolymer 1-vinyl-1,2,4-triazole with <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone

New polymer nanocomposites containing iron oxide nanoparticles stabilized with a biocompatible copolymer of 1-vinyl-1,2,4-triazole with N-vinylpyrrolidone were produced. The synthesis was conducted using the method of chemical reduction of iron ions with hydrazine hydrate in an aqueous medium in the presence of a polymer matrix. The ESR spectroscopy data showed that the core—shell type nanoparticles were obtained. The core generally consistsed of zero-valence iron coated with an oxide shell. According to the data of transmission electron microscopy, the obtained polymer nanocomposites consisted of nanoparticles of mainly spherical shape with a diameter from 1 to 14 nm. Aggregates formed from individual stabilized nanoparticles of up to 75 nm in size (in most cases) were also observed. These aggregated particles were found to self-organize and form branched chains. Nanocomposites were characterized by a different particle-size distribution, which was determined by the initial ratio of the copolymer and the precursor of iron nanoparticles.     

NO-donating and hemolytic activity of tetranitrosyl iron complexes with ligands of the 2-mercaptopyridine series

Russian Chemical Bulletin - The NO-donating and hemolytic activity of the binuclear tetranitrosyl iron complexes (TNIC) with thiolate ligands of the composition [Fe2(SR)2(NO)4], where R is...     

Regularities of oxygen and water thermal desorption from barium cerate doped by neodymium,samarium, and gadolinium

Processes of thermal desorption of oxygen molecules and water from BaCe_1–x M _x O_3–δ, where M= Nd, Sm, and Gd, presintered in air at the temperature of 650°C are studied. It is found that oxygen is desorbed only from neodymium–doped barium cerate and is almost not evolved from barium cerate doped by samarium and gadolinium. The amount of desorbed oxygen features a square dependence on cationic doping by neodymium. At similar degrees of cationic doping, the amount of water desorbed from neodymium–doped barium cerate is always lower than that from the cerate doped by samarium and gadolinium. The obtained experimental data on thermal desorption and analysis of literature data served as a basis for the conclusion as to the mixed valency of neodymium Nd(III)–Nd(IV) in BaCe_1–x Nd _x O_3–δ. In this case, at similar doping degrees x, the hydration degree of BaCe_1–x Nd _x O_3–δ is lower and the oxygen index is higher than in BaCe1_–x (Sm,Gd) _x O_3–δ. The differences become more pronounced at high degrees of cationic doping and must decrease at an increase in temperature.     

Chromatographic determination of nitrophenols in aqueous media after two-stage preconcentration using an N-vinylpyrrolidone-based polymer

Two-stage procedures for the preconcentration of nitrophenols (4-nitrophenol, 2,4- and 2,5-dinitrophenol, and 2,4,6-trinitrophenol) from aqueous solutions are proposed. At the first stage, the preconcentration and desorption of nitrophenols under dynamic conditions is carried out. At the second stage, depending on the nature of the desorption solution, the eluate is evaporated (acetonitrile) or saturated with ammonium sulfate and extracted with acetone (aqueous NH₃ solution). The concentration factors are 4000 and 910, respectively. Nitrophenols are determined in concentrates by thin layer chromatography and HPLC, the limits of detection are 1.0–1.8 and 0.25–0.45 μg/L, respectively. The duration of analysis is 200 min.     

Detection and quantification of chitosan aggregates by pressure-assisted capillary zone electrophoresis

An approach to the detection and determination of chitosan aggregates in acetic acid solutions is proposed using pressure-assisted capillary zone electrophoresis. Processes of chitosan aggregation are studied depending on the composition of dispersion medium and storage time. The presence of several species of positively charged chitosan aggregates is revealed for the first time. Particle sizes in the range 20–2500 nm are determined by scanning electron microscopy and static and dynamic light scattering. The dependence of the shape of electropherograms on particle size distribution obtained under the same conditions is found. A trend to changing electrophoretic mobility depending on the size of the aggregate is observed, which enables the approximate evaluation of the polydispersity of chitosan solutions. Chitosan is used for the effective dynamic modification of capillaries, which does not require the introduction of a modifier into the background electrolyte.     

Determination of the surface area of loose metal deposits by impedance spectroscopy

The surface area and fractal dimensions of the surface of loose copper and zinc deposits obtained within 30 and 300 s at direct current sixfold exceeding limiting diffusion current on a smooth electrode were in situ determined by impedance spectroscopy. Impedance measurements were performed in 0.5 M Na₂SO₄ solution. A constant phase element taking into account the distribution of double-layer capacitance over the fractal surface of the electrode was used in the equivalent impedance scheme. Specific surface calculated with regard to the weight of the released metal slightly varied within 300 s (from 6.16 to 6.55 and from 7.12 to 5.89 m²/g for copper and zinc deposits, respectively). Fractal dimensions estimated by chronopotentiometry were given for comparison. Fractal dimensions found by two methods for loose copper and zinc deposits agree with each other; their values (2.19–2.75) testify that the surface of the deposits densely fills the space.     

An electrochemical aptasensor for cytochrome C,based on pillar[5]arene modified with Neutral Red

An electrochemical aptasensor is developed for the highly sensitive determination of cytochrome C, using a change in the redox current of Neutral Red covalently bound to terminal carboxyl groups of decasubstituted pillar[5]arene as a signal. The inclusion of the analyte into the complex with an aptamer reduces peaks of redox current of the dye through the dissociation of electron transfer chain in the surface layer. The aptasensor enables the determination of 1 nM to 1.0 mM of cytochrome C in the presence of 1000-fold excesses of albumin, polyethylene glycol, and lysozyme as models of interfering components in biological fluids.     

A comparative study of the reactions of fluorinated oxi- and thiiranes with acyl chlorides

The CoCl₂-catalyzed reactions of fluorinated 1,2-oxi- and thiiranes with acyl chlorides were studied. It was found that a regioselective heterocycle opening reaction resulted in two isomers having normal and abnormal structure in a ratio predetermined by the substituents in both the starting heterocycles and acyl chlorides.