A. L. Tolstikhina

Interfacial nanofabrication strategies in development of new functional nanomaterials and planar supramolecular nanostructures for nanoelectronics and nanotechnology

Clusters, nanoparticles, nanowires, long molecules as nanotubes and polynucleotides, and functional supramolecular nanostructures are currently considered as potential building blocks for nanotechnology and nanoelectronic devices and circuits, and development and introduction of new methods to control effectively their structure, composition and nanoscale organization are necessary. Here we describe a number of new nanofabrication methods which are based on the monolayer techniques, biomimetic principles, interfacial reactions and interactions. The methods allowed to produce new stable reproducible planar one-dimensional and two-dimensional arrays of ligand-stabilized nanoclusters and nanoparticles on solid substrates, ultrathin polymeric nanoscale-ordered mono- and multilayer quasi-crystalline and nanocomposite films, planar polymeric complex films with integrated DNA and inorganic building blocks as semiconductor and iron oxide nanoparticle quasi-linear arrays and nanowires. Transmission electron microscopy, STM and AFM techniques were used to characterize the fabricated nanostructures. Effects related to discrete electron tunneling were observed in the monolayers of nanoclusters and small gold nanoparticles at room temperature using STM.

Ferroelectric microdomains and microdomain arrays recorded in strontium–barium niobate crystals in the field of atomic force microscope

Microdomains and various one-dimensional (1D)- and two-dimensional (2D)-microdomain arrays were formed under dc-voltages applied to the tip of an atomic force microscope (AFM) in ferroelectric SrxBa1−xNb2O6 crystals. Detailed studies of the characteristics of the AFM—recording and decay kinetics of the written arrays have shown that the crucial factors of the stability of a domain array are its dimensionality and discreteness (described by a distance Δ between the recorded point domains forming the array). The dependence of the stability on the discreteness of domain ensembles is analyzed. With decreasing Δ, the decay times of the domain ensembles increases. The stability of 2D arrays (domain squares, complex-shaped arrays composed of the domain ensembles of opposite polarity) by orders of magnitude exceeds that of 1D-arrays (domain chains and lines) provided all factors of recording being the same. As an illustration, the decay time of individual (spatially separated) domains and quasicontinuous domain l...

X-ray fluorescence methods for investigations of lipid/protein membrane models

The protective effect of the bisphosphonate drug xydiphone (K,Na-ethidronate) on membrane-bound enzyme damaged by lead ions has been studied. A protein/lipid film of Ca-ATPase/phosphatedylethanolamine deposited on a silicon substrate was used as a model system. The position of lead ions within the molecular film before and after the xydiphone treatment was determined using the total-reflection X-ray fluorescence method. This technique is based on the simultaneous measurement of the X-ray reflection and the yield of the fluorescence radiation excited by X-ray inelastic scattering. The possibility of directly locating lead ions is the main advantage of this approach. Xydiphone has been found to effectively eliminate lead ions that have been incorporated into Ca-ATPase molecules during a preliminary incubation in lead acetate solution. The lead ions that were bound at the sites of the Ca-ATPase attachment to the phospholipid monolayer have proved to be inaccessible for xydiphone. A preliminary incubation of Ca-ATPase in the xydiphone solution precluded the incorporation of lead ions into the protein.

Studies of nanoscale structural ordering in planar DNA complexes with amphiphilic mono- and polycations

Abstract Formation of DNA complexes with Langmuir monolayers of cationic lipid octadecylamine (ODA) and new amphiphilic polycation poly-4-vinylpyridine with 16% cetylpyridinium groups (PVP-16) on the surface of native DNA aqueous solution with low ionic strength has been studied. AFM topographic images of DNA/ODA and DNA/PVP-16 complex Langmuir–Blodgett films deposited on the mica substrates were obtained. The complex structures and individual DNA molecules on the amphiphile monolayer surface were observed. The characteristic extended net-like structures and quasi-circular toroidal condensed conformations of the planar DNA complexes were formed in dependence on the polycationic amphiphile monolayer state during the DNA binding. The data obtained give evidence for the effectiveness of monolayer techniques for investigation the mechanisms of DNA complexation with amphiphilic mono- and polycations and demonstrate its perspectives for creation of supramolecular planar DNA-based self-organized nanostructures with nanoscale structural ordering.

The design, fabrication and characterization of controlled-morphology nanomaterials and functional planar molecular nanocluster-based nanostructures

Abstract New nanofabrication methods based on the monolayer techniques, biomimetic principles, interface reactions and interactions have been developed. The formation and deposition of the mixed Langmuir monolayers composed of inert amphiphile matrix and guest ligand-stabilized metal-core nanocluster molecules allowed to obtain ordered stable reproducible planar monomolecular nanocluster-based nanostructures on solid substrates. The decomposition of similar metal–organic precursor compounds in the mixed Langmuir monolayers at the gas–liquid interface resulted in the initiation of two-dimensional growth of inorganic nanoparticles in the plain of monolayer. Gold and iron-containing nanoparticles were synthesized and characterized by scanning probe microscopy and transmission electron microscopy techniques. Effect of external applied field on the shape of two-dimensionally grown magnetic nanoparticles was observed. Effects related to discrete electron tunneling were observed in the monolayer structures of nanocluster molecules and gold nanoparticles at room temperature using STM.

Multimode Atomic Force Microscopy of Triglycine Sulfate Crystal Domain Structure

The same crystal surface regions in a triglycine sulfate (TGS) ferroelectric crystal were probed by varied SPM methods, namely contact and intermitted-contact AFM, piezoresponce force microscopy (PFM), scanning Kelvin microscopy (SKM) and electrostatic force microscopy (EFM). Criteria for identification of real (dynamic) domains and morphologically similar domain “memory” regions are proposed. Inaccuracy in identification may result in further errors in estimating the parameters of the domain structure. The images of ferroelectric domains in the spreading-resistance mode that directly indicate a contribution from an enhanced conductivity in the vicinity of the domain walls have been obtained for the first time.

Synthesis of Ni-containing nanoparticles in Langmuiur–Blodgett films

Abstract Synthesis of Ni-containing anisotropic flatten nanoparticles was carried out in a mixed Ni stearate/stearic acid and Ni arachidate/arachidic acid LB films by borohydrid reduction under different reaction conditions. The structure and composition of the films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and atomic force microscopy. Ordered lamellar structure of LB films was not disrupted by nickel reduction procedure and the presence of oblate nanoparticles was observed by AFM.

Nanorelief of the natural cleavage surface of triglycine sulphate crystals with substitutional and interstitial impurities

Ferroelectric triglycine sulphate crystals (TGS) with substitutional (LADTGS+ADP, DTGS) and interstitial (Cr) impurities have been studied by atomic-force microscopy, X-ray diffraction, and X-ray fluorescence. The nanorelief parameters of the mirror cleavage TGS(010) surface have been measured with a high accuracy. A correlation between the crystal defect density in the bulk and the cleavage surface nanorelief is revealed at the submicrometer level.

Creation of Microdomains in an Atomic Force Microscope in Strontium-Barium Niobate Ferroelectric Crystals

Microdomains in SBN-0.61 polydomain crystals have been recorded by the atomic force microscopy method with the application of a dc voltage of 1–10 V applied to a probe. The domain areas have been obtained as functions of the voltage and exposition time. The kinetics of the decay of the domains after the shutdown of the field have been determined. The nonclassical characteristics observed in the dynamics of domain walls are attributed to the nonuniform spatial distribution of the atomic force microscope field. The kinetics of the decay of the microdomains are in qualitative agreement with the kinetics of the depolarization of the strontium-barium niobate solutions, which is observed by macroscopic methods.

Characterization of single-crystal sapphire substrates by X-ray methods and atomic force microscopy

The possibility of characterizing a number of practically important parameters of sapphire substrates by X-ray methods is substantiated. These parameters include wafer bending, traces of an incompletely removed damaged layer that formed as a result of mechanical treatment (scratches and marks), surface roughness, damaged layer thickness, and the specific features of the substrate real structure. The features of the real structure of single-crystal sapphire substrates were investigated by nondestructive methods of double-crystal X-ray diffraction and plane-wave X-ray topography. The surface relief of the substrates was investigated by atomic force microscopy and X-ray scattering. The use of supplementing analytical methods yields the most complete information about the structural inhomogeneities and state of crystal surface, which is extremely important for optimizing the technology of substrate preparation for epitaxy.