A.N. Sergeev-Cherenkov

STM study of morphology and electron transport features in cytochrome c and nanocluster molecule monolayers

The morphology and electron tunneling through single cytochrome c and nanocluster Pt(5)(CO)(7)[P(C(6)H(5))](4) molecules organized as monolayer Langmuir-Blodgett (LB) films on graphite substrate have been studied experimentally using scanning tunneling microscopy (STM) and spectroscopy techniques with sub-nanometer spatial resolution in a double barrier tunnel junction configuration STM tip-monomolecular film-conducting substrate at ambient conditions. STM images of the films revealed globular structures with characteristic diameters (approximately 3.5 nm for the protein molecule and approximately 1.2 nm for the nanocluster). The spectroscopic study by recording the tunneling current-bias voltage (I-V) curves revealed tunneling I-V characteristics with features as steps of different width and heights that are dependent on the STM tip position over the molecule in the monolayer, giving evidence for sequential discrete electron-tunneling effects with the combination of the single electron Coulomb-charging energy and the electronic energy level separation (molecular spectrum) in such immobilized metalloprotein and nanocluster structures that can be of interest for the development of bioelectronic and hybrid functional nanosystems.

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.

Molecular cluster based nanoelectronics

The use of molecular clusters as a basis of molecular single-electronic systems is considered experimentally and theoretically. The Langmuir-Blodgett formation and scanning tunneling microscope study of structures with chemically different cluster molecules is described. I-V curves and control curves of molecular single-electron transistors based on various single molecules were studied at room temperature. Comparison of experimental I-V curves with simulated ones allows us to identify a regime of slow energy relaxation of electrons in experimental transistors. Experimental study of electron transport through the planar molecular nanosystems has shown a correlated character of electron tunneling in such systems.

Structure and characteristics of the complexes between polyampholites and anionic liposomes

Polyampholites are synthesized by the alkylation of poly-4-vinylpyridine with ω-bromocarboxylic acids, and their interaction with the negatively charged bilayer lipid vesicles (liposomes) is studied. In the above polymers, quaternized pyridine units are zwitterion (betaine) groups, in which cationic and anionic groups are linked by the -(CH2) n -bridges. Via the methods of fluorescence, laser scattering, and DSC, the length of the ethylene spacer in the betaine group is shown to control the ability of the polymer to interact with anionic liposomes and induce structural rearrangements in the liposomal membrane. At n = 1, polybetaine is not linked to anionic liposomes. At n = 2, polybetaine is sorbed on the membrane, but it causes no dramatic structural rearrangements in the bilayer. At n = 3, the adsorption of polybetaine triggers the lateral segregation of lipids in the outer membrane layer. At n = 5, adsorption of polymer is accompanied by the lateral segregation and flip-flop of lipid molecules; as a result, all anionic membrane lipids are involved in the microphase separation. This evidence is of evident interest for the controlled design of polymers and related complexes and conjugates for biomedical applications.

ORGANIZED PLANAR NANOSTRUCTURES VIA INTERFACIAL SELF-ASSEMBLY AND DNA TEMPLATING

The methods are presented for fabrication of new nanoscale-organized planar inorganic nanostructures, ultrathin polymeric and nanocomposite films on solid substrates with incorporated nanosized functional and structural building blocks. The methods are based on interfacial synthesis and self-assembly, DNA templating and scaffolding. Ultimately thin monomolecular and multilayer ordered stable polymeric and nanocomposite films containing incorporated ligand-stabilized gold nanoclusters, interfacially in-film grown metallic (Au, Pd) nanoparticles and organized low-dimensional nanostructures were formed. N-alkylated derivatives of poly(4-vinilpyridine) were synthesized and used as water-insoluble amphiphilic polycations to form organized polymeric Langmuir monolayers and novel planar DNA/amphiphilic polycation complexes at the air–aqueous DNA solution interface. The extended net-like and quasi-circular toroidal condensed conformations of deposited planar DNA/amphiphilic polycation complexes were obtained in dependence on the amphiphilic polycation monolayer state during the DNA binding. Planar DNA/amphiphilic polycation complexes were used as nanotemplates for fabrication of organized planar bio-organic–inorganic hybrid nanostructures with ordered nanophase inorganic components (quasi-one-dimensional arrays of semiconductor (CdS) and iron oxide nanoparticles and nanorods) organized in planar matrix of deposited DNA/amphiphilic polycation complex film. The formed nanostructures were characterized by atomic force microscopy and transmission electron microscopy techniques.

Metal nanoelectrodes for molecular transistor and investigation of electron transport in molecular systems.

Gold nanoelectrodes with gaps of less than 10 nm were formed by conventional E-beam lithography on silicon substrates covered by Al2O3. Molecular films were deposited on the electrodes by Langmuir-Shaefer technique. The I-V curves of such systems show a suppressed conductance indicating a correlated electron tunnelling through the system. All measurements were made at room temperature.