G. Meshkov

Surface Relief Changes in Cholesteric Cyclosiloxane Oligomer Films at Different Temperatures.

The development of new approaches for the surface topography control is an important topic as the relief significantly affects physical and chemical properties of surfaces. We studied cholesteric cyclosiloxane oligomeric films on which surface focal conic domains with double-helix pattern were observed by means of AFM. In situ investigation of the dependence of the films topography on temperature showed that the surface relief formation can be effectively managed by varying conditions of thermal treatment. Obtained structures can be frozen by cooling the films below glass-transition temperature.

Direct Observation of Changes in Focal Conic Domains of Cholesteric Films Induced by Ultraviolet Irradiation

The helical supramolecular structure of cholesteric liquid crystalline (LC) films predetermines their outstanding optical properties and the unique nanostructure of their surface. The introduction of photochromic dopants in these films opens up an interesting possibility for creation of smart cholesteric materials with photocontrollable optical and photovariable surface properties. Using atomic force microscopy (AFM), we performed in situ measurements of the surface topography of cyclosiloxane LC cholesteric oligomer films during the cholesteric helix twisting caused by their preliminary ultraviolet (UV) irradiation. A chiral-photochromic isosorbide-based dopant was introduced in the films to control the cholesteric helix pitch by UV-irradiation. The initial films are characterized by planar texture with the presence of focal conic domains having the double-spiral relief on their surface. UV-irradiation of these films leads to the cholesteric helix twisting resulting in a decrease in the surface relief period, and the enlargement of defect areas between the domains. The detailed mechanisms of the rearrangement of the film surface structure due to the cholesteric helix twisting are suggested. They include the rotation and displacement of cholesteric layers in the bulk, and the nucleation of new ones at the surface in defect regions.

On the contrast of the terrace conductivity of graphite

The recently developed technique of scanning resistance microscopy (SRM) has recommended itself as a high-precision tool for the investigation of surface conductive properties. It is different from conventional atomic-force microscopy in its ability to obtain simultaneous data about both the topography and contact resistance of a probe and sample. This method was used for investigation of the conductive properties of highly oriented pyrolytic graphite (HOPG). A series of experimental facts testifies that the field of application of SRM during the performance of nanoobject research on graphite substrate is restricted by the surface of atomic plateau. This is connected with the fact that during crossing of atomic steps the state of contact of the probe and sample changes, which has a great influence on its conducting properties.

A novel tool for the local anodic oxidation of graphite

A novel probe for partial local anodic oxidation is presented, which allows bulging regions to be grown on the graphite surface. Based on the scanning probe microscopy observations, it was concluded that the bulging regions consist of graphite oxide. The partial oxidation occurs in two stages, which are related to the formation of C–O bonds on the graphite surface and the adsorbed water intercalation of the oxidized graphite. The bulging regions have low conductivity, therefore their formation is a promising method to be used in the production of nanoelectronic devices.

Nanoobjects of interpolymer complexes of polyaniline and PAMPSA in aqueous solutions

Nanoobjects of interpolymer complex of polyaniline (PAn) and polysulfonic acid have been synthesized. The matrix chemical synthesis of PAn was carried out in aqueous solution at room temperature in the presence of poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) as a matrix. The choice of PAMPSA was determined by its good solubility in water, perfect film-forming properties and high molecular weight (~ 2000000). The polymerization process of aniline on PAMPSA took place at pH ~ 2 on the polymer backbone at high rate, while aniline concentration was sufficiently low. The true solution of PAn-PAMPSA interpolymer complex was coated on mica substrates. We have studied PAn films surfaces using FEMTOSCAN atomic force microscope (AFM) in dependence on the solution concentrations and the presence of strong electrolyte (HCl).

Blister formation during graphite surface oxidation by Hummers’ method

Graphite oxide has a complex structure that can be modified in many ways to obtain materials for a wide range of applications. It is known that the graphite precursor has an important role in the synthesis of graphite oxide. In the present study, the basal-plane surface of highly annealed pyrolythic graphite (HAPG) was oxidized by Hummers’ method and investigated by Raman spectroscopy and atomic force microscopy. HAPG was used as a graphite precursor because its surface after cleavage contains well-ordered millimeter-sized regions. The treatment resulted in graphite intercalation by sulfuric acid and blister formation all over the surface. Surprisingly, the destruction of the sp2-lattice was not detected in the ordered regions. We suggest that the reagent diffusion under the basal plane surface occurred through the cleavage steps and dislocations with the Burgers vector parallel to the c-axis in graphite.

Biosensor for detection of viruses and bacteria in liquids

Раннее обнаружение вирусов и бактерий позволяет существенно снизить риск инфекционных заболеваний. Эта актуальная, социально значимая задача достаточно сложна и требует инновационных решений [1–4]. В настоящей статье приведено описание разработки компактного и недорогого биосенсора, предназначенного для использования в медицинской диагностике. Early detection of viruses and bacteria can significantly reduce the risk of infectious diseases. This topical, socially relevant task is complex and requires innovative solutions [1–4]. This paper describes the development of a compact and inexpensive biosensor intended for use in medical diagnostics.

Study of stages of electrochemical synthesis of graphite oxide using multifunctional scanning probe microscopy

Методами сканирующей зондовой микроскопии исследованы стадии окисления графита электрическим током в отсутствие интеркалирующего агента. Полученные результаты могут быть использованы при создании катализаторов и сенсорных элементов, а также представляют значительный интерес для дальнейшего развития методов зондовой литографии углеродных материалов. With the use of scanning probe microscopy the oxidation of graphite by electric current in the absence of intercalating agent is investigated. The obtained results can be used to create catalysts and sensory elements and are of considerable interest for further development of scanning probe lithography of carbon materials.

Cantilever biosensors for detection of viruses and bacteria

Кантилеверные биосенсоры являются многообещающей платформой для создания высокочувствительных и селективных сенсорных устройств. В первой части статьи рассмотрены история вопроса, свойства микрокантилеверов, технологии их производства и биофункционализации, а также способы детекции. Cantilever biosensors are a promising platform for development of highly sensitive and selective sensors. The first part of the paper describes the background of the problem, properties of microcantilevers, technologies of their production and biofunctionalisation, and also detection methods.