A. A. Bukharaev

The effect of substrate and air humidity on morphology of films of L-leucyl-L-leucine dipeptide

The effect of a substrate and air humidity on the morphology of a thin film of L-leucyl-L-leucine dipeptide was studied. For this purpose, conditions for obtaining a thin film of the dipeptide were determined by thermal analysis. The morphology of L-leucyl-L-leucine film deposited on the surface of highly oriented pyrolytic graphite (HOPG) and mica at different humidities was studied by atomic force microscopy. It was established that film was formed on the surface of HOPG and uniformly coated with nanostructures, the sizes and shapes of which depended on the film thickness. Crystallization of the dipeptide with the formation of complex crystalline nanosized objects occurs on the surface of mica. An increase in air humidity results in a decrease in the geometric dimensions of nanostructures on the surface of the dipeptide film in the case of HOPG and complication of crystal agglomerate structure when mica was used as a substrate.

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

Nickel nanoparticles and nanowires obtained by scanning probe lithography using point indentation technique

A lithographic method of obtaining metal nanowires and nanoparticles on solid substrates is proposed, which employs a polymer mask with windows for the metal deposition formed by indentation in an atomic force microscope. Using this method, Ni nanowires with a minimum width of 60 nm, thicknesses within 6–20 nm, and lengths up to 20 μm and Ni nanoparticles with a preset ordered arrangement have been obtained on a SiO2 surface. The domain structure in obtained nanoobjects has been studied by the magnetic force microscopy technique.

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.

Investigation of micromagnetism and magnetic reversal of Ni nanoparticles using a magnetic force microscope

Isolated Ni nanoparticles were studied in situ by atomic and magnetic force microscopy in the presence of an additional external field up to 300 Oe. By comparing topographic and magnetic images, and also by computer modeling of magnetic images, it was established that particles smaller than 100 nm are single-domain and easily undergo magnetic reversal in the direction of the applied external magnetic field. For large magnetic particles, the external magnetic field enhances the magnetization uniformity and the direction of total magnetization of these particles is determined by their shape anisotropy. Characteristics of the magnetic images and magnetic reversal of particles larger than 150 nm are attributed to the formation of a vortex magnetization structure in these particles.

Thermally induced diphenylalanine cyclization in solid phase

The reaction of cyclization of diphenylalanine in solid phase under heating was studied, which is a stage in formation of various nanostructures from this dipeptide. The temperature ranges of the reaction as well as of dehydration of clathrate of diphenylalanine with water were determined. Kinetic parameters of cyclization were estimated within the approaches of the non-isothermal kinetics (“model-free” kinetics and linear regression methods for detection of topochemical equation). The product of diphenylalanine cyclization was characterized by X-ray powder diffractometry, FTIR spectroscopy and TG/DSC analysis. Crystallization of diphenylalanine and cyclo(diphenylalanine) from methanol solutions was studied using atomic force microscopy. The results obtained may be useful for the design of new nanomaterials based on diphenylalanine at high temperatures.

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.

Fabrication of magnetic micro- and nanostructures by scanning probe lithography

Planar magnetic structures based on cobalt nanofilms have been obtained by scanning probe lithography. It has been shown that ferromagnetic nanoparticles with different domain structures can be formed by local oxidation of a cobalt film on a graphite substrate with the use of a conductive probe of an atomic force microscope (AFM). Using AFM nanoengraving of polymethylmethacrylate, masks were formed to obtain microcontact pads connected by cobalt nanowires with a width of 250–1400 nm and a thickness of 10–30 nm on the silicon dioxide surface. The topography and magnetization structure of the obtained samples were controlled by atomic and magnetic force microscopy.

Combined STM/AFM visualization of the local density of states in the InAs/GaAs quantum dots

Combined ultra-high vacuum scanning tunneling/atomic-force microscopy (STM/AFM) has been implemented for the first time for the tunneling spectroscopy of the size-quantized states in the InAs/GaAs(001) surface quantum dots (QDs). The tunneling spectra and current images, which reflect the energy and spatial distribution of the local density of the ground and excited states in the QDs have been obtained.