A. P. Chuklanov

Interaction of l‐leucyl‐l‐leucyl‐l‐leucine thin film with water and organic vapors: receptor properties and related morphology

The ability of highly ordered tripeptide structures to keep or change their morphology in contact with organic vapors was studied. A thin film of tripeptide l‐leucyl‐l‐leucyl‐l‐leucine (LLL) was prepared having microcrystals and nanocrystals on its surface, which are stable upon vacuum drying but become objects of selective morphology change after a contact with vapors of organic solvents. Fine separate LLL crystals and their agglomerates of submicron and larger dimensions were observed by atomic force microscopy and scanning electron microscopy. After saturation with guest vapors, these crystals can remain intact or change their morphology with the increase in size or complete destruction depending on the guest molecular structure. The crystals completely lose their shape after the binding of pyridine vapors. The other studied guests produce much smaller transformations or have no effect on crystal morphology despite being sorbed by solid LLL, which was shown using quartz crystal microbalance sensor. The observed size‐exclusion effect for guest sorption by LLL was found to be broken by the same guests that can change the initial crystal shape. This helps to explain the morphology changes of LLL crystals after the guest sorption and release. Copyright

Formation of nanoislands on the surface of thin dipeptide films under the effect of vaporous organic compounds

Sorption properties of a thin L-alanyl-L-valine dipeptide film for vapors of organic compounds, i.e., methanol and toluene, were studied. Compositions of the inclusion compounds formed in the systems are determined using quartz microbalances. The surfaces morphology of of thin dipeptide films before and after the interaction with organic sorbate was studied with atomic force microscopy. The dipeptide was found to have a larger sorption capacity for methanol than for toluene. As a result of the interaction between a thin L-alanyl-L-valine dipeptide layer with toluene vapor, nanoislets appear on the film surface, and the receptor ability of dipeptide inactivated.

Measuring Young's Modulus of Biological Objects in a Liquid Medium Using an Atomic Force Microscope with a Special Probe

A special probe with a 5-μm-diameter ball fixed at the end is developed for an atomic force microscope (AFM), with the use of which it is possible to obtain more correct values of the Young’s moduli of biological objects in liquid media and eliminate the risk of damaging the sample surface. In particular, the AFM measurements with this probe in situ revealed an increase in the Young’s modulus of rat blood vessel under the action of chlorhexidine.

The effect of a substrate on the morphology of dipeptide (L-valyl-L-alanine) films before and after their interaction with pyridine vapor

The effect of a substrate on the morphology of a thin film of L-valyl-L-alanine dipeptide before and after its interaction with pyridine vapor was studied. For this purpose, images of a dipeptide film deposited on the surface of highly oriented pyrolytic graphite (HOPG), gold, and mica and images showing its surface after saturation with vaporous pyridine were obtained by atomic force microscopy. The morphology of the initial L-valyl-L-alanine film was found to be considerably dependent on the nature of the substrate used. Interaction with vaporous pyridine resulted in formation of nanostructures on its surface in the case in which HOPG or gold were used as a substrate. When mica was used as a substrate, nanostructures were present on the surface of the initial film and almost disappeared after interaction with pyridine.

Atomic force microscopy of cobalt nanoparticles with electro-catalytic properties

A method of controlled potential electrodeposition of the cobalt nanoparticles with sizes from 30 to 400 nm on the surface of highly oriented pyrolytic graphite has been developed. The images of nanoparticles were obtained with an atomic force microscope. A computer program was applied to obtain the size distribution of electrodeposited particles depending on the electrodeposition potential, electrolytic concentration, and deposition time. Using voltammetry it has been established that the cobalt nanoparticles with the diameter of about 50 nm show the maximal catalytic activity during electro-oxidation of ethanol.

Creation of lithographic masks using a scanning probe microscope

The experimental results on scanning probe lithography (SPL)—the formation of lithographic masks using scanning probe microscope—are presented. Polymethylmethacrylate (PMMA)-based masks prepared by the SPL method are used to form metal nanoparticles of the specified sizes and shape, as well as the metallic nanowires connecting the contact areas. The analysis of various SPL modes showed that the procedure of point indentation with the switched-on microscope feedback is optimal for the formation of round nanoparticles. When forming the rectangular particles, the procedure of multiple scanning of one region in the contact mode is optimal. The quality of lithographic masks can be substantially increased by the additional use of chemical etching to remove excess PMMA after the mask is formed. The topography and magnetization structure of the formed structures were monitored by atomic force microscopy and magnetic force microscopy.

Magnetic force microscopy investigation of the magnetization reversal of permalloy particles at high temperatures

The magnetization reversal of an array of permalloy particles formed by scanning probe lithography on the silicon dioxide surface has been investigated in the temperature range from room temperature to 800 K. Using scanning magnetic force microscopy and numerical calculations of the magnetic anisotropy field of a particle at different temperatures, it has been shown that an increase in the temperature leads to a decrease in the external magnetic field required to reverse the magnetization direction of the particle. From the obtained results, it has been concluded that the magnetization reversal of the studied particles is accompanied by the formation of an intermediate state with an inhomogeneous magnetization structure.

Atomic-force microscopy of nickel nanoparticles possessing electrocatalytic properties

Surface morphology of highly oriented pyrolytic graphite with electrodeposited nickel nanoparticles was studied by atomic-force microscopy in the presence and absence of ethanol. Voltammetric and atomic-force microscopic data and histograms of particle size distribution were used to evaluate the unit-area catalytic activity of the nanocatalyst in relation to conditions of its preparation.

AFM study of thin films of oligopeptide L-valyl-L-valine before and after interaction with vapors

The effect of the substrate type, ambient relative humidity, water vapor and vapors of organic compounds on the surface morphology of films based on dipeptide L-valyl-L-valine are studied using atomicforce microscopy. It is found that at a low relative humidity the dipeptide is crystallized on a hydrophobic substrate with the formation of pyramidal structures, while at a high relative humidity hollow truncated cones are observed. A dipeptide film coated with irregularly shaped objects is observed on hydrophilic substrates. After saturation of the L-valyl-L-valine film with the vapors of proton-donor solvents the formation of new objects on its surface or the destruction of initial objects can occur, while water vapor does not affect the surface morphology. For proton acceptors the major factor affecting the surface morphology of dipeptide film is their energy of the hydrogen bond with proton donors. It is shown that the effect of organic vapors on the film morphology depends on the substrate type.

Surface morphology and electrocatalytic properties of nickel nanoparticles formed in track pores

Structures, each of which is composed of a conducting substrate with a protective dielectric layer containing an array of equal-sized pores formed under the action of high-energy ions and chemical etching, are created. The created pores are electrochemically filled with nickel nanoparticles. With atomic-force microscopy (AFM), it is established that Ni nanoparticles are generated exclusively within ion tracks without film formation on the surface of a silicon-dioxide layer. Histograms illustrating the nanoparticle-diameter distribution are constructed, and areas of the nickel nanoparticles are calculated. The electrochemical and electrocatalytic properties of Ni nanoparticles inherent to ethanol-oxidation reactions are investigated. The catalytic activity per unit area of the nanocatalyst is estimated using voltammograms, AFM data, and histograms characterizing the particle size distribution.