I. V. Taranov

ELECTRONICS OF MOLECULAR NANOCLUSTERS

The molecular nanoclusters proved to be very promising objects for applications in electronics not only because they have absolutely identical chemical structure and allow for bottom to top approach in constructing new electronic devices, but also for the possibility to design and create great variety of such clusters with specific properties. The formation and deposition of mixed Langmuir monolayers composed of inert amphiphile molecular matrix and guest ligand-stabilized metal-core nanoclusters are described. This approach allowed to obtain the ordered stable reproducible planar monolayer and multilayer nanocluster nanostructures on solid substrates. The use of novel polymeric Langmuir monolayers formed by amphiphilic polyelectrolytes and nanoclusters resulted in fabrication of ultimately thin monomolecular nanoscale-ordered stable planar polymeric nanocomposite films. The morphology and electron transport in fabricated nanostructures were studied experimentally using AFM and STM. The effects of single electron tunneling at room temperature through molecular cluster object containing finite number of localized states were theoretically investigated taking into account electron–electron Coulomb interaction. It is shown that tunnel current-bias voltage characteristic of such tunnel junction is characterized by a number of staircase steps equal to the number of clusters eigenlevels, however the fronts of each steps are asymptotically linear with finite inclination. The analytically obtained current–voltage characteristics are in agreement with experimental results for electron tunneling through molecular nanoclusters at room temperatures.

ORGANIZED SUPERSTRUCTURES AT NANOSCALE AND NEW FUNCTIONAL NANOMATERIALS

We report on a number of new effects of self-organization at nanoscale, leading to creation of new functional nanomaterials, including carbon and carbon–metal nanotoroids and nanodiscs and self-assembling of magnetic nanoparticles into helices and chains. We also extensively used a new approach of biopattern nanoengineering to create DNA-based complexes with metal or CdSe/ZnS core-shell nanorods (22 × 4.5 nm) which possess strong linearly polarized photoluminescence due to unidirectional orientation of nanorods along DNA filaments. Optical, electrical, and topological (geometrical) properties of such complexes were investigated. This work is a result of a coherent effort (since 1980s) of a consortium of Russian research groups in Nano-technology (INTC: Interdisciplinary Nanotechnology Consortium) aimed at creating molecular electronic devices based on individual and collective properties of specially designed and fabricated nanoclusters.

Decapsulation of polyelectrolyte nanocomposite microcapsules by pulsed microwave effect

A technology of remote activation of specially created polyelectrolyte nanocomposite microcapsules (PNMCs) by pulse microwave action is developed. The sensitivity of the synthesized PNMCs to the external microwave action is caused by the presence of layers of ferric oxide nanoparticles in their shells. A setup for remote pulse microwave action on the PNMC is constructed. The effect of decapsulation of polyelectrolyte nanocomposite microcapsules under the remote action of microwave pulse is detected. Destruction of the PNMC shell is recorded by the methods of the transmission electron microscopy.

Pulsed electric field-induced remote decapsulation of nanocomposite liposomes with implanted conducting nanoparticles

The results obtained in creating the new nanocomposite hybrid systems sensitive to external nonthermal electric-field pulses, which are created for the encapsulation, addressed delivery, and the controlled decapsulation of various substances in aqueous media, are presented. Such systems are based on liposomes containing electrically neutral biogenic lipids that are functionalized by conducting nanoparticles and polymers. The fabricated systems have been investigated using transmission electron microscopy, atomic-force microscopy, electron magnetic resonance, laser light scattering, electrophoresis, and conductometry. The systems constructed under the action of short (on the order of 8 ns) electric pulses with high intensities (up to 100 kV/m) are found to exhibit the remote decapsulation effect. The model describing the mechanism of interaction between nanostructured liposomes with surface conducting nanoparticles and an external electric field leading to substantial changes in liposome structure is proposed. The critical values of the external electric field stimulating the decapsulation of nanocomposite liposomes are estimated with the help of the constructed model.

Planar nanosystems on the basis of complexes formed by amphiphilic polyamine, magnetite nanoparticles, and DNA molecules

In the present paper the results of a study of new planar composite nanosystems on the basis of complexes formed by amphiphilic polyamine, magnetite nanoparticles, and DNA molecules are presented. Amphiphilic polyamine stearylspermine is synthesized and characterized by the FTIR spectroscopy technique. It is found that a Langmuir monolayer on an aqueous subphase surface can be formed by synthesized stearylspermine molecules. The stearylspermine Langmuir monolayer compression isotherm changes caused by the interaction of a monolayer with colloid magnetite nanoparticles and DNA molecules from the aqueous phase have been studied. The monolayer nanostructures on the surface of mica substrate-Langmuir-Blodgett films of complexes formed by stearylspermine, magnetite nanoparticles, and DNA molecules are formed. The structure of the obtained monolayer films was investigated using the AFM scanning probe technique. Possibilities for the formation of polycomplexes which comprise stearylspermine molecules, functional inorganic nanoparticles, and polymers have been discussed.

Effect of microwave irradiation on composite iron oxide nanoparticle/polymer microcapsules

Iron oxide nanoparticle/polymer microcapsules containing different number of layers of iron oxide nanoparticles have been made using the layer-by-layer alternating absorption technique. Nanoparticles as well as composite microcapsules have been characterized by TEM and SEM. The electronic paramagnetic resonance (EPR) spectra of water suspensions of iron oxide nanoparticles and microcapsules with iron oxide nanoparticles inside the capsule shell have been measured. Parameters of the EPR spectra are sensitivity to nanoparticle concentration in solution as well as to thermal and microwave microcapsules treatment. The shell permeability, as explored by confocal fluorescence microscopy, is decreased after temperature treatment of microcapsules but increased after microwave radiation. These results can find practical application in medicine and bioengineering for remote control over the permeability of microcapsule shells.

Effect of Gold Nanorods on the Remote Decapsulation of Liposomal Capsules Using Ultrashort Electric Pulses

Decapsulation of nanocomposite liposomal capsules due to the effect of ultrashort electric pulses is obtained when the liposomal sheaths of the capsules are bound to significantly anisotropic gold nanoparticles (nanorods). Destruction of the liposomal sheath is interpreted using the rotational displacement of gold nanorods in the presence of the pulsed electric field. Such an interpretation is used to derive an expression for the critical electric field that determines the threshold level of the effect. The calculated critical field is in agreement with the experimental results. It is shown that the decapsulation is related to the presence of the gold nanorods in the sheath of liposomal capsules and is not obtained in the absence of the nanorods.

Remote decapsulation of nanocomposite liposomal capsules containing gold nanorods by ultrashort electric pulses

The decapsulation effect of nanocomposite liposomal capsules containing anisotropic gold nanoparticles (nanorods), which is caused by the action of ultrashort electric pulses on these capsules, is discovered. The mechanism of destruction of liposomal shells of the capsules near poles of conducting gold nanorods under the pulse electric action is described. An expression for the critical intensity of the pulse electric field, which determines the threshold of initiation of this effect, is obtained. Its numerical value is in agreement with the obtained experimental data. It is shown experimentally that the discovered decapsulation effect is caused by the presence of gold nanorods connected to the liposomal shell of the capsules and does not arise in the absence of nanorods.

Investigation of absorption and reflection spectra of aqueous suspensions of nanoparticles in the X band of microwave bandwidth

Aqueous suspension of iron oxide nanoparticles stabilized by citric acid has been synthesized. Nanoparticles were characterized by transmission electron microscopy. Nanoparticles size distribution was estimated by dynamic laser light scattering method. Absorption spectra of nanoparticles suspensions at different concentrations were recorded in visible part of optical band. Zeta-potential of nanoparticles was measured. Absorption and reflection spectra of aqueous suspension of nanoparticles in 7.8 - 11.2 GHz frequency range have been obtained. A frequency ranges with maximal sensitivity of microwave spectra parameters to nanoparticles concentration were found.