Effect of nanosize metal overlayer on C₆₀ thin film optical parameters near fundamental absorption edge

The effect of nanosize metal overlayer, both evaporated on C₆₀ films (Bi, In) and attached as nanoparticles of (Ag, Au), on the optical parameters of C₆₀ films near the fundamental absorption edge has been studied. The values of direct band gap (Eg), the optical gap (E₀) in the framework of Tauc model and the Urbach tail parameter (EU) were determined from the absorption coefficient (α) spectra plotted in coordinates (αhν)², (αhν)¹/² ln(α) vs hν, respectively. Parameters obtained testify diminishing the structural disorder in C₆₀ thin films with nanosize metal overlayer at optimal ratio of C₆₀ to metal layer thicknesses

Optical and photoluminescent properties of nanostructured hybrid films based on functional fullerenes and metal nanoparticles

The chemically cross-linked C₆₀ thin films, capable of binding Ag or Au nanoparticles, were prepared by the gas-phase treatment with diamine for one set of samples and dithiol for another one and decoration with Ag or Au nanoparticles, respectively. The optical and photoluminescent properties of the obtained nanostructured hybrid films in comparison with the undecorated films were studied. The low temperature photoluminescence (PL) spectra demonstrate significant changes of the band intensity and appearance of fine structure for bands connected with radiative transitions of self-trapped and localized excitons. The decoration of pristine and treated C₆₀ films with Ag nanoparticles leads to a decrease of PL intensity and to slight bandgap reduction. These phenomena can be explained by the increase of the surface recombination velocity at the fullerene-nanoparticle interface. At the same time, the nanoparticles insignificantly decrease the transmittance of light into the fullerene and Si layers, and have almost no influence on photoelectric properties of metal/fullerene/Si barrier structures

Bundling up carbon nanotubes through Wigner defects

We show, using ab initio total energy density functional theory, that the so-called Wigner defects, an interstitial carbon atom right besides a vacancy, which are present in irradiated graphite can also exist in bundles of carbon nanotubes. Due to the geometrical structure of a nanotube, however, this defect has a rather low formation energy, lower than the vacancy itself, suggesting that it may be one of the most important defects that are created after electron or ion irradiation. Moreover, they form a strong link between the nanotubes in bundles, increasing their shear modulus by a sizeable amount, clearly indicating its importance for the mechanical properties of nanotube bundles.Comment: 5 pages and 4 figure

OH-functionalized open-ended armchair single-wall carbon nanotubes (SWCNT) studied by density functional theory

The structures of ideal armchair (5,5) single-wall carbon nanotubes (SWCNTs) of different lengths (3.7, 8.8, and 16.0 Å for C40H20, C80H20, and C140H20) and with 1–10 hydroxyl groups at the end of the nanotube were fully optimized at the B3LYP/3-21G level, and in some cases at the B3LYP/6-31G* level, and the energy associated with the attachment of the OH substituent was determined. The OH-group attachment energy was compared with the OH functionalization of phenanthrene and picene models and with previous results for zigzag (9.0) SWCNT systems. In comparison to zigzag SWCNTs, the armchair form is more (by about 5 to 10 kcal mol−1) reactive toward hydroxylation

Zinc Phthalocyanine−Graphene Hybrid Material for Energy Conversion: Synthesis, Characterization, Photophysics and Photoelectrochemical Cell Preparation

Graphene exfoliation upon tip sonication in o-­‐DCB was accomplished. Then, covalent grafting of (2-­‐ aminoethoxy)(tri-­‐tert-­‐butyl) zinc phthalocyanine (ZnPc), to exfoliated graphene sheets was achieved. The newly formed ZnPc-­‐graphene hybrid material was found soluble in common organic solvents without any precipitation for several weeks. Application of diverse spectroscopic techniques verified the successful formation of ZnPc-­‐graphene hybrid materi-­‐ al, while thermogravimetric analysis revealed the amount of ZnPc loading onto graphene. Microscopy analysis based on AFM and TEM was applied to probe the morphological characteristics and to investigate the exfoliation of graphene sheets. Efficient fluorescence quenching of ZnPc in the ZnPc-­‐graphene hybrid material suggested that photoinduced events occur from the photoexcited ZnPc to exfoliated graphene. The dynamics of the photoinduced electron transfer was evaluated by femtosecond transient absorption spectroscopy, thus, revealing the formation of transient species such as ZnPc+ yielding the charge-­‐separated state ZnPc•+–graphene•–. Finally, the ZnPc-­‐graphene hybrid material was integrated into a photoactive electrode of an optical transparent electrode (OTE) cast with nanostructured SnO2 films (OTE/SnO2), which exhibited sta le and reproducible photocurrent responses and the incident photon-­‐to-­‐current conversion efficien-­‐ cy was determine

Measurements of DT alpha particle loss near the outer midplane of TFTR

Measurements of DT alpha particle loss to the outer midplane region of TFTR have been made using a radially movable scintillator detector. The conclusion from this data is that mechanisms determining the DT alpha loss to the outer midplane are not substantially different from those for DD fusion products. Some of these results are compared with a simplified theoretical model for TF ripple-induced alpha loss, which is expected to be the dominant classical alpha loss mechanism near the outer midplane. An example of plasma-driven MHD-induced alpha particle loss is shown, but no signs of any ``collective`` alpha instability-induced alpha loss have yet been observed