T.V. Yurova

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.

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.

Effect of compression of a stearic acid monolayer on interfacial binding of copper ions and cluster formation

Abstract The effect of compression of a stearic acid Langmuir monolayer on the interaction of copper ions with the monolayer and on the formation of interface clusters has been studied as functions of pH and ionic content of the water subphase. Copper binding was estimated by direct electron paramagnetic resonance measurements of ion concentrations in the water subphase. A scanning tunnelling microscopy study of monolayer Langmuir-Blodgett films, deposited on graphite substrates, gave evidence for the formation of nanosized clusters on the monolayer surface. The data obtained showed that the interaction of the monolayer with copper ions and the accompaning cluster formation processes were determined by the arrangement, order and mobility of the stearic acid molecules in the monolayer and the electrostatics at the interface.

The design, fabrication and characterization of rare-earth containing multilayer supramolecular films with nanometer-scale controlled composition, structure and properties

Abstract We demonstrate the controlled formation of highly-ordered rare-earth stearate multilayer Langmuir–Blodgett films, novel supramolecular organized structures: hybrid polyanion/rare-earth metal cation/anionic surfactant metal–organic superlattice thin films with separating acidic amphiphile bilayers by highly rare-earth-doped polymeric interlayers and fabrication of closely packed, homogeneous and stable rare-earth metal cation/polyanion complex self-assembled multilayer films in which molecular polyelectrolyte building blocks are held together by complexed polyvalent metal cations. The design and fabrication strategies developed to construct those films are based on the surface and interface trivalent rare-earth metal cation complexation with consecutive formation of multilayer superstructures on the solid substrates. The structure and morphology of the built-up multilayer films were characterized by atomic force microscopy and X-ray diffraction.

Structural control of Langmuir–Blodgett films containing metal cations by ligands exchange

Abstract The structure of multilayer gadolinium stearate Langmuir–Blodgett (LB) films has been studied in dependence on the gadolinium salt nature and aqueous subphase composition used for the LB film preparation. Stearic acid Langmuir monolayers were formed on the surface of aqueous gadolinium acetate or gadolinium chloride solutions (10 −4 M) with different monovalent electrolyte concentrations at the same pH value (5.65) at which all monolayer stearic acid molecules were ionized and bound with Gd 3+ cations. The structure of the deposited films was characterised by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). It was found that Gd stearate LB films formed with the use of gadolinium acetate solution as a subphase had quasi-crystalline domain morphology with ordered layered structure, in contrast to the rather disordered structure of LB films formed using GdCl 3 solution as a subphase. The structure characteristic for the Gd stearate LB film formed with the use of Gd acetate solution as a subphase can be obtained using GdCl 3 solution with an excess of acetic acid (9×10 −4 M). The substantially different morphology of Gd stearate LB film characterized by the perfect layered and planar terrace structure was obtained in the presence of NaCl (10 −2 M) in Gd acetate or Gd chloride solutions used as subphases. The data obtained show that the formation of polyvalent metal cation complexes with Langmuir monolayer and bulk phase ligands along with ligands exchange and substitution interactions are substantial factors determining structural organization of the corresponding deposited metal-containing multilayer LB films.

Structural studies of Langmuir–Blodgett films containing rare-earth metal cations

Abstract Comparative structural study of gadolinium stearate Langmuir–Blodgett (LB) films formed by monolayer deposition from either aqueous gadolinium acetate or gadolinium chloride solutions have been carried out. Structure of the films was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, high-energy electron diffraction, atomic force microscopy and scanning electron microscopy. It was found that when subphase pH had a value at which all monolayer stearic acid molecules were ionized and bound with Gd 3+ cations (pH>5), the LB films deposited from gadolinium acetate and gadolinium chloride subphases had substantially different structure. The gadolinium stearate LB films formed with gadolinium acetate subphase were highly ordered and consisted of hexagonal layers with unit cell parameter a ≈4.8 A and interlayer spacing d ≈49 A. LB films formed with GdCl 3 subphase under the same conditions (salt concentration, pH) were characterized by a rather disordered structure where along with hexagonal phase, a monoclinic phase with the interlayer parameter d ≈40 A was present. The reason of this phenomenon is discussed. The data obtained indicate that the control of multivalent metal cations complexes formation in the subphase and at the monolayer surface can be an instrument for optimization, the conditions to form metal-containing LB film with regulated structure and properties.

X-ray diffraction study of gadolinium stearate Langmuir-Blodgett films

The comparative structural studies of gadolinium stearate Langmuir-Blodgett films prepared with the use of two different subphases (aqueous solutions of gadolinium chloride and gadolinium acetate) have been performed by the methods of X-ray diffractometry. The films were applied onto single-crystal silicon substrates coated with a native-oxide layer either with the use of buffer molecular stearic-acid layers or without such layers. It was established that the films obtained with the use of gadolinium acetate and the preliminarily formed buffer layers are, in fact, single-phase Y-type films with highly ordered molecular structure, and the thickness of the bimolecular layer d = (51.3 ± 0.5) Å.