Carbon Heterostructures Research Articles

Electronic states in zigzag carbon nanotube quantum dots

Local electronic properties of quantum dot nanotubes modeled by connecting pure semiconducting and metallic nanotubes via appropriate junctions are studied following a single $\ensuremath{\pi}$-band tight-binding Hamiltonian. The junctions are formed by introducing pair defects composed of heptagons and pentagons along the axial direction of pure nanotubes. We investigate the dependence of the confined electronic states with the characteristic sizes of the quantum dots taking into account different nanotube-based heterostructures. Quantum-well-like and interface states are characterized by investigating the spatial dependence of the local density of states of the discrete levels. We follow the Green's function formalism and adopt real-space renormalization techniques to calculate local density of states. The conductance of metal/semiconductor(metal)/metal carbon heterostructures is also investigated and we found exponentially the decay and oscillatory behaviors that may be associated with the electronic structure of the tube constituents and the details of the junctions.

2P1-C4 Nanoassembly of carbon nanotubes and heterostructures by nanorobotic manipulation

2P1-C4 Nanoassembly of carbon nanotubes and heterostructures by nanorobotic manipulation

Electronic properties of diamond/nondiamond carbon heterostructures

In this paper the properties of diamond/amorphous carbon heterostructures are studied using photoelectron spectroscopy in the ultraviolet (UPS) and x-ray (XPS) regime. The nondiamond carbon films are deposited on a p-doped polycrystalline diamond substrate, and produced by first, electron beam evaporation of graphite forming hydrogen-free amorphous carbon $(a\ensuremath{-}\mathrm{C}:\mathrm{H})$ films. The overlayer formation is monitored step-by-step, and the changes in band bending in the diamond substrate and the valence band discontinuities are deduced from the UPS and XPS spectra. In the $\mathrm{diamond}/a$-C structure a downward band bending in diamond evolves continuously with overlayer thickness and a final value of about 1.1 eV is obtained, resulting in a band offset of $1.5\ifmmode\pm\else\textpm\fi{}0.1\mathrm{eV}.$ In the $\mathrm{diamond}/a\ensuremath{-}\mathrm{C}:\mathrm{H}$ structure a downward band bending of 1.4 eV is observed after only a brief deposition time, when the estimated overlayer thickness is still less than a monolayer. The ion energies employed for the film deposition were 200 and 600 eV and although the resulting overlayers exhibit characteristic structural differences, the band bending and band offset $(1.4\ifmmode\pm\else\textpm\fi{}0.15\mathrm{eV})$ are not noticeably influenced. It appears likely that in this case the defects formed in the diamond lattice through the energetic ions used for the overlayer deposition, are responsible for a pinning of the Fermi level at the surface. In an additional experiment the diamond substrate was irradiated with ${\mathrm{Ar}}^{+}$ ions (3 keV) and the resulting band bending, induced through the creation of a defect-rich surface layer, amounts to about 1.3 eV. The introduction of dangling bonds and/or \ensuremath{\pi}-bonded regions, which are energetically located in the gap of diamond, leads to the observed increase in downward band bending in the p-doped diamond.

1041 The origin, cell migration and nuclear formation in the development of the mouse amygdala

This work addresses current direction of the nanoparticles-based systems intended for cancer therapy by developing a newly-formulated innovative chemically-engineered anti-tumor composite consisting in a magnetic, fluorescent, lipophilic, and biologically-active carbon heterostructure capable by itself or through coupling with a chemotherapeutic agent to selectively induce tumor cell death. The anti-tumor compound was synthesized through a modified sol-gel method by addition of a low-cost molecule with recently proven anti-tumor properties which was combusted and flash-cooled along with magnetic iron oxides precursors at 250 °C. The synthesized compound consisted in carbon dots, graphene and hematite nanoparticles which endowed the composite with unique simultaneous fluorescence, magnetic and anti-tumor properties. The in-vitro cytotoxicity performed on tumor cells (human osteosarcoma) and normal cells (fibroblasts) showed a selective cytotoxic effect induced after 24 h of treatment by the drug-free composite, leading to a cell death of 37%, for a composite concentration of 0.01 mg/mL per 104 tumor cells, whereas the composite loaded with an antitumor drug (mitoxantrone) boosted the cell death effect to 47% for similar exposure conditions. The method shows high potential as it boosts drug transfer within tumor cells. Different antitumor drugs already in clinical use can be used following their separate or in-cocktail controlled combustion.