E. G. Glukhovskoy

Ab initio electron propagator calculations of transverse conduction through DNA nucleotide bases in 1-nm nanopore corroborate third generation sequencing.

BACKGROUND The conduction properties of DNA molecule, particularly its transverse conductance (electron transfer through nucleotide bridges), represent a point of interest for DNA chemistry community, especially for DNA sequencing. However, there is no fully developed first-principles theory for molecular conductance and current that allows one to analyze the transverse flow of electrical charge through a nucleotide base. METHODS We theoretically investigate the transverse electron transport through all four DNA nucleotide bases by implementing an unbiased ab initio theoretical approach, namely, the electron propagator theory. RESULTS The electrical conductance and current through DNA nucleobases (guanine [G], cytosine [C], adenine [A] and thymine [T]) inserted into a model 1-nm Ag-Ag nanogap are calculated. The magnitudes of the calculated conductance and current are ordered in the following hierarchies: gA>gG>gC>gT and IG>IA>IT>IC correspondingly. The new distinguishing parameter for the nucleobase identification is proposed, namely, the onset bias magnitude. Nucleobases exhibit the following hierarchy with respect to this parameter: Vonset(A)<Vonset(T)<Vonset(G)<Vonset(C). CONCLUSIONS The difference in current magnitudes and onset voltages implies the possibility of nucleobases electrical identification by virtue of DNA translocation through an electrode-equipped nanopore. GENERAL SIGNIFICANCE The results represent interest for the theorists and practitioners in the field of third generation sequencing techniques as well as in the field of DNA chemistry.

Purification non-aqueous solution of quantum dots CdSe- CdS-ZnS from excess organic substance-stabilizer by use PE- HD membrane

Recently, a new simple method for the purification of CdSe-CdS-ZnS quantum dots by using membrane filtration, the filtration process, successfully separated the oleic acid from quantum dots through membranes purification after synthesis; purification of quantum dots is a very significant part of post synthetical treatment that determines the properties of the material. We explore the possibilities of the Langmuir-Blodgett technique to make such layers, using quantum dots as a model system. The Langmuir monolayer of quantum dots were then investigated the surface pressure-area isotherm. From isotherm, we found the surface pressure monolayer changed with time.

Monitoring of copper nanoparticle penetration into dentin of human tooth in vitro

Study of the penetration depth of synthesized copper nanoparticles into cut samples of human dentin was conducted. The scanning electron microscopy was used to determine the elemental composition of fresh transverse cleavage of the dentin cut for determination of the copper nanoparticles penetration with an effective antiseptic effect. The morphology of the cut surface of the dentin of a human tooth was studied and the lower limit of the diffusion boundary was determined. It was found that copper nanoparticles penetrate into the dentin cut to a depth of ~ 1.8 μm with the diffusion coefficient of 1.8×10–11 cm2/s. Despite the rather small size of the synthesized copper nanoparticles (20-80 nm), a rather small penetration depth can be explained by the high aggregation ability of copper nanoparticles, as well as the ability of a micellar solution of sodium dodecyl sulfate, in which nanoparticles were stabilized, to form conglomerates in micelles of much larger sizes.

The depending of Langmuir monolayers of quantum dots and fatty acid mixture properties from their components ration

Langmuir monolayers of quantum dots could be used as a platform for creation of planar fluorescent sensors that widely used in biology during immunochemistry analysis. Interesting feature is a creation of matrix with separated quantum dots one from each other. The process of Langmuir monolayers of quantum dots and fatty acid mixtures with different component ratios formation was studied. The method of compression isotherm was used for Langmuir monolayer formation process characterization, atomic force microscopy was used for transferred films characterization. Volume component ratios of 1:1, 1:2. 2:1, 1:5 and 5:1 of arachidic acid and quantum dots were studied. Was shown that increasing of the arachidic acid concentration in the solution cause to decreasing the maximal monolayer area, changing in monolayers liquid phase extensions and type. Also the monolayer compressibility and compression module are changes and achieves a peak value at components ratio of 1:1. At the indicated component ratio the formed Langmuir monolayer of quantum dots and arachidic acid mixture was transferred on the glass substrate and studied by atomic force microscopy.

Copper nanoparticles obtained by chemical reduction stabilized by micelles of various surfactants

We carried out the synthesis of copper nanoparticles via chemical reduction of micelles stabilized by various surfactants of different nature, such as cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTAB). We investigated the sustainability of the products of synthesis, i.e. copper nanoparticles stabilized by micelles of various surfactants, after the period of 50 days. Surface morphology and elemental composition of obtained copper nanoparticles were characterized by scanning electron microscopy (SEM).

The Formation of Quantum Dots - Liquid Crystal monolayers by Langmuir-Blodgett method

The article describes the features of the formation of CdSe/CdS/ZnS quantum dots - liquid crystal Langmuir monolayers on a water subphase surface by different temperature value. Monolayers structure was investigated by analyzing the compression isotherms and surface potential value. Films on the solid substrate (glass plates) were investigated by atomic force microscopy method for morphology, thickness and roughness. Film structure was studied as a function of the pressure at which the transfer was carried. It is shown that the structure of films obtained by a higher temperature of subphase is more perfect. The film is monolayered and uniform in thickness.

Ligands Exchange, Studying the Stability and Optical Properties of CdSe/CdS/ZnS Quantum Dots with Liquid Crystal

Liquid crystal (LC) ligands have the ability to control the dispersion and the homogeneity of quantum dots (QDs) in solution. LC phase transition can be used as a tool to control the assembly of dispersed QDs. Comparing the results before and after the ligands exchange (oleic acid to liquid crystal) highlights some important differences in optical and morphology properties of QDs. We have studied changes in optical properties and a shift in the spectral wavelength band of QDs with LC ligands. Application of LC ligands leads to quenching of the emission and excitation spectra intensity of CdSe/CdS/ZnS QDs. Such hybrid materials have interesting potential for usage in a variety of applications such as photonic materials or (bio) chemical sensors.

Electronic properties of A2B6 quantum dots incorporated into Langmuir–Blodgett films

An experimental and theoretical study is performed for features of the electronic spectrum of CdSe/CdS/ZnS quantum dots incorporated into Langmuir–Blodgett films. Analysis of the investigated samples assesses the state of the first three levels of the electron spectrum for a quantum object. Good qualitative and quantitative agreement is achieved between the experimental results and theoretical estimates. It is shown that the mechanism of the observed field emission current through a quantum dot is described satisfactorily by the Morgulis–Stratton theory under the considered experimental conditions.

The influence of redistribution ions in subphase at the properties Langmuir monolayer: physical and theoretical experiments

The formation of a monolayer and its structure depend on many factors. One of the least studied factors is the influence of the electric field. In this regard, the purpose of this study is to investigate the influence of the direction and magnitude of the electric field on the properties of monolayer, formed on the surface of water. The experiments have revealed: the electric field exerts a significant influence on the formation of monolayers, in particular, during liquid phase formation. The second part of the isotherm (corresponding liquid phase) were significantly stretched. We explain the liquid phase extension by the fact of the charge increasing (and change pH) of the surface region. To confirm this assumption also we made computer modelling of process monolayer formation.

Processes in suspensions of nanocomposite microcapsules exposed to external electric fields

Microcapsules with and without magnetite nanoparticles incorporated in the polyelectrolyte shell were prepared. The effect of external electric field on the nanocomposite polyelectrolyte microcapsules containing magnetite nanoparticles in the shell was studied in this work as a function of the electric field strength. Effect of electric fields on polyelectrolyte microcapsules and the control over integrity of polyelectrolyte microcapsules with and without inorganic nanoparticles by constant electric field has been investigated. Beads effect, aggregation and deformations of nanocomposite microcapsule shell in response to electric field were observed by confocal laser scanning microscopy (CLSM). Thus, a new approach for effect on the nanocomposite microcapsule, including opening microcapsule shell by an electric field, was demonstrated. These results can be used for creation of new systems for drug delivery systems with controllable release by external electric field.