Peter Scharff

Molecular dynamics simulation of mechanical, vibrational and electronic properties of carbon nanotubes

A theoretical investigation of the mechanical, vibrational and electronic properties of single walled carbon nanotubes (SWCNTs) with the armchair (5,5) and zigzag (10,0) geometry is carried out in detail. The Poisson ratio, Young modulus and Raman active frequencies for these types of SWCNTs are calculated within a simple vibrational model. The electronic spectra of the SWCNTs are obtained using a tight-binding calculation. The theoretical results are compared with the available experimental ones.

Retraction: Magnetic carbon.

This corrects the article DOI: 10.1038/35099527

Structure and Thermophysical Properties of Fullerene C60 Aqueous Solutions

The structure and thermophysical properties of fullerene C60aqueous solutions were investigated both experimentally and theoretically. The aggregation kinetics results indicated that the structure of fullerene C60aggregates in water could be described as a fractal system. The IR and electronic absorption spectra obtained confirm the presence of the crystalline phase in aqueous solution. The numerical values of thermodynamic coefficientsαP,βT,βS,cP, andcV, and sound velocity were determined from the measured (P–V–T) data. The vibrational spectrum of the crystalline structure (Thsymmetry group) formed from the hydrated single fullerene C60molecules in aqueous solutions was calculated using the molecular dynamics approach.

Structure of fullerene C60 in aqueous solution

The structure of fullerene C60 in aqueous solution was investigated both experimentally and theoretically. The fullerene C60 was found to aggregate rapidly at room temperature. The aggregation kinetics results indicated that the structure of C60 aggregates in water could be described as a fractal system. The optical absorption spectra obtained testify to the crystalline character of absorption. The formation in water of fractal structures and a crystalline phase from highly stable hydrated fullerene (C60)13 clusters (Ih symmetry group) was predicted using the molecular dynamics approach.

DNA nanotechnology of carbon nanotube cells: physico-chemical models of self-organization and properties

Abstract We report UV and IR spectroscopic studies of partially unwrapped double helix DNA molecules with carbon nanotubes of “bundles”-type mixtures, which are spontaneously self-assembled into a coupled blocks of DNA molecule that has the chaotic ball structure with carbon nanotube. The shift of the absorption peak from 279.3 to 285.4 nm for the DNA/nanotube layer in comparison with that for DNA layer may be caused by the hydrogen bonds changing under DNA and nanotube interaction. This fact is confirmed by decrease of the wave number of N–H…N, N–H…O groups on 12 cm−1, the absence of C–CH3 group vibration mode at 1440 cm−1 in IR transmittance spectra from DNA/nanotubes layer, indicative of their self-assembled formation. The results of cell investigations: the maximal photoresponse in the ranges of 515–600 and 950–1070 nm is observed at the light excitation of 500–1100 nm, and change of the applied voltage. The models of electronic and photoelectronic processes in heterostructures are developed and experimentally confirmed.

Self-organization C60 nanoparticles in toluene solution

The structure of fullerene C60 in toluene solution was investigated both experimentally and theoretically in detail. C60 was found to aggregate slowly even in fairly dilute solution concentrations ranging from 0.18 to 0.78 g/l at room temperature. The electronic absorption spectra obtained testify to the mainly molecular character of absorption. The aggregation kinetics results indicated that the structure of C60 aggregates could be described as a fractal system. The numerical calculations predicted the formation of stable fullerene (C60)N clusters in toluene solution with sizes >1.2 nm and aggregation number N≥3.

Biophysical studies of fullerene-based composite for bio-nanotechnology

Abstract The UV absorption and fluorescence spectra of biological samples and the DNA structural state in cells under X-ray irradiation in the presence of the fullerene-containing composite, synthesized on the basis of aminopropylaerosil, were investigated and analysed in detail. The significant pro-oxidant effect of the fullerene-containing composite at the low concentration of fullerene C60 (10−5 M) was revealed.

Electrical properties of two-dimensional fullerene matrices

The electrical properties of two-dimensionally polymerized C60 fullerenes were studied. Fullerene matrices consisting of randomly oriented domains are compared to the highly-oriented rhombohedral phase. The conductivity of the randomly oriented polymers obeys the Arrhenius law and can be described in a multiple trapping model. The oriented phase of polymeric C60 shows a distinct anisotropy in the electrical properties with a metallic-like in-plane conductivity at high temperatures.

Electrical and Thermal Conductivity of Polymer-Nanocarbon Composites

Thermal and electrical conductivities in composites (CMs) based on various types of polymer matrix – epoxy resin (epoxy) and polyethylene oxide (PEO) have been investigated in the temperature range 150–300 K. A few types of carbon materials have been used as a filler in CMs: thermoexfoliated graphite (TEG) (TEG content was 0.5–10 wt.%), TEG dispersed in an ultrasonic disperser (nano-TEG) (content – 1–2 wt.%),and multiwalled carbon nanotubes (MWCNTs) (content – 1–10 wt.%). It was shown that the ultrasonic dispersion of TEG in the epoxy matrix leads to a shift of the percolation transition in the electrical conductivity to higher values of the graphite content and decreases the thermal conductivity of these CMs. This occurs due to the break down of the worm-like structure of TEG particles, i.e., the already formed fragments of TEG clusters. It is revealed also that the use of epoxy as a polymer matrix and a nondispersed thermoexfoliated graphite as a filler gives the greatest values of the thermal and electrical conductivities of composites in the comparison with others.

Self-organizing DNA/carbon nanotube molecular films

Abstract We have studied the effects of the electronic structure self-formation and charge transfer for the planar system of layers from DNA unwrapped double helix, DNA double helix, DNA unwrapped double helix with carbon nanotubes (CNT) in the separated sections with common bounds on the silicon substrate—DNA chip on Si. The electronic structure of (DNA/CNT) layer are formed as a result of changes of electron levels in adenine, cytozine, guanine and thymine which were directly revealed by UV, IR spectroscopy. The transport properties of such systems are determined by the charge transfer through the barriers in the DNA double helix/unwrapped double helix and in the DNA unwrapped double helix/CNT heterostructures that were proved by tunneling spectroscopy investigations.