Energies and kinetic barriers associated with transition metal (Sc) clustering on a single-walled carbon nanotube (SWNT) and graphene were studied by the all-electron density functional method. The analysis shows that the binding energy of Sc atom on SWNT is highly sensitive to the tube diameter and chirality. The metal atoms clustering on common SWNT, with diameters ∼1-2 nm, is energetically favorable and kinetically permitted. Although well-separated, lone Sc atoms on SWNT can enhance the hydrogen storage capacity, their aggregation into clusters significantly reduces the hydrogen uptake; e.g., a Sc 4 cluster has the same hydrogen uptake as a single Sc atom. Our analysis shows that, although indeed light transition metal decorated SWNT present potential material for the hydrogen storage, utter care should be taken to avoid the metal clustering on support material, to achieve and maintain higher hydrogen capacity.

A new kind of carbon foam, which is based on the welding of single-walled carbon nanotubes, is built in a computer simulation. Its precisely defined architecture and all atomic positions allow one to perform detailed theoretical analysis of the properties. Such foam is as light as 19 of steel, while its stiffness is similar and nearly isotropic, and it represents a strong three-dimensional material with various possible applications. Furthermore, its nanoporous structure is accessible to molecular hydrogen and the potential surface analysis indicates that it should be an excellent hydrogen storage medium. Importantly, such foam is a feasible structure that can be produced based on the known tube/fullerene welding techniques.

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In this work, the sensor response of MPcFx (M = Cu, Co, Zn; x = 0, 4, 16) films toward gaseous NH3 (10–50 ppm) was studied by a chemiresistive method and compared to that of unsubstituted MPc films to reveal the effects of central metals and F-substituents on the sensing properties. A combination of atomic force microscopy and X-ray diffraction techniques have been used to elucidate the structural features of thin MPcFx films deposited by organic molecular beam deposition. It has been shown that the sensor response of MPcF4 films to ammonia is noticeably higher than that of MPc films, which is in good correlation with the values of binding energy between the metal phthalocyanine and NH3 molecules, as calculated by the density functional theory (DFT) method. At the same time, in contrast to the DFT calculations, MPcF16 demonstrated the lesser sensor response compared with MPcF4, which appeared to be connected with the different structure and morphology of their films. The ZnPcF4 films were shown to exhibit a sensitivity to ammonia up to concentrations as low as 0.1 ppm, and can be used for the selective detection of ammonia in the presence of some reducing gases and volatile organic compounds. Moreover, the ZnPcF4 films can be used for the detection of NH3 in the gas mixture simulating exhaled air (N2 76%, O2 16%, H2O 5%, and CO2 3%).

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In the present work, we study and compare the structure and sensing properties of thin films of unsubstituted palladium phthalocyanine (PdPc) and hexadecafluorosubstituted palladium phthalocyanine (PdPcF 16 ). Thin films of PdPc and PdPcF 16 were obtained by the method of organic molecular beam deposition and their structure was studied using UV-visible spectroscopy, X-ray diffraction and atomic force microscopy techniques. The electrical sensor response of PdPc films toward ammonia and hydrogen was investigated and compared with that of PdPcF 16 films. The nature of interaction between the phthalocyanines films and some gaseous analyte molecules has been clarified using Quantum chemical (DFT) calculations.

We study vibrationally-resolved resonant Auger (RAS) spectra of ammonia recorded in coincidence with the NH+2 fragment, which is produced in the course of dissociation either in the core-excited 1s−14a1 intermediate...