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Magnetic fields generated by the nanosolenoids based on the (5, 3) and (10,7) gold nanotubes (AuNTs) 12–600 Å long with numbers of Au atoms 20–2000 are calculated. The electron energy levels of the finite length tubules were determined using the linearized augmented cylindrical waves method with Born–von Karman cyclic boundary conditions and on account of a helical symmetry of the AuNTs. Using these data, the numbers of conducting channels NF and the low-temperature ballistic electron currents in the finite AuNTs are determined, and finally, the magnetic fields B of the gold nanosolenoids are obtained. Due to the increase in the number of conduction channels with the increase in the length of the tubes, the internal magnetic field gradually increases from 1.6 T/V in a tubule with L = 12 Å up to 12 T/V in a tube with L = 600 Å, slowly approaching the magnetic field of 14 T/V of the infinite (5, 3) AuNT. At a distance of 5 Å from the ends of the tubes (near z = L/2 – 5 Å), this field decreases rapidly, halving at z = L/2 and almost zeroing near z = L/2 + 5 Å. The field from the outside of the tubes is weak but not zero as in the infinite tubule. It is minimal at z = 0 and reaches a maximum at the edge of the AuNTs, where it is about 3–4 times less than the internal field. These results pave the way for a more realistic design of the nanosolenoids.

This study was supported by the EC ERA.Net RUS Plus project No. 237 WATERSPLIT as well as Russian Basic Research Foundation No. 16-53-76019. S.K. and E.S. furthermore gratefully acknowledge computing time granted by the Center for Computational Sciences and Simulation (CCSS) of the Universitaẗ Duisburg-Essen and the supercomputer magnitUDE (DFG grants INST 20876/209-1 FUGG, INST 20876/243-1 FUGG) provided by the Zentrum für Informations-und Mediendienste (ZIM). E.S. is also grateful for support by the Cluster of Excellence RESOLV (EXC1069) funded by the Deutsche Forschungsgemeinschaft., One-dimensional tungsten disulfide (WS2) single-walled nanotubes (NTs) with either achiral, i.e., armchair (n, n) and zigzag-type (n, 0), or chiral (2n, n) configuration with diameters dNT > 1.9 nm have been found to be suitable for photocatalytic applications, since their band gaps correspond to the frequency range of visible light between red and violet (1.5 eV < Δϵgap < 2.6 eV). We have simulated the electronic structure of nanotubes with diameters up to 12.0 nm. The calculated top of the valence band and the bottom of the conduction band (ϵVB and ϵCB, respectively) have been properly aligned relatively to the oxidation (ϵO2/H2O) and reduction (ϵH2/H2O) potentials of water. Very narrow nanotubes (0.5 < dNT < 1.9 nm) are unsuitable for water splitting because the condition ϵVB < ϵO2/H2O < ϵH2/H2O < ϵCB does not hold. For nanotubes with dNT > 1.9 nm, the condition ϵVB < ϵO2/H2O < ϵH2/H2O < ϵCB is fulfilled. The values of ϵVB and ϵCB have been found to depend only on the diameter and not on the chirality index of the nanotube. The reported structural and electronic properties have been obtained from either hybrid density functional theory and Hartree-Fock linear combination of atomic orbitals calculations (using the HSE06 functional) or the linear augmented cylindrical waves density functional theory method. In addition to single-walled NTs, we have investigated a number of achiral double-walled (m, m)at(n, n) and (m, 0)at(n, 0) as well as triple-walled (l, l)at(m, m)at(n, n) and (l, 0)at(m, 0)at(n, 0) nanotubes. All multiwalled nanotubes show a common dependence of their band gap on the diameter of the inner nanotube, independent of chirality index and number of walls. This behavior of WS2 NTs allows the exploitation of the entire range of the visible spectrum by suitably tuning the band gap., Deutsche Forschungsgemeinschaft INST 20876/243-1 FUGG,INST 20876/209-1 FUGG,EXC1069; Russian Foundation for Basic Research 16-53-76019; EC ERA.Net RUS Plus project No. 237 WATERSPLIT; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

Thin films of organic semiconductors are intensively studied in view of their exploitation in modern electronic devices. Until now, few crystalline substrates have been used as clean surfaces for organic molecular beam epitaxy (OMBE). Among them, β-alanine crystals recently proved to be valuable substrates because of their cleavage along (010) surfaces. To increase the set of available substrates, we searched layered structures through the Cambridge Structural Database by means of the ToposPro program package. Also, we propose here an energy partitioning scheme with a new descriptor that allows one to determine the feasibility of cleaving a crystal along a given crystallographic plane. This procedure is based on the partition of cohesive energy among molecules in a given layer in the crystal structure and molecules found in adjacent layers. The experimental validation on 12 selected amino acid structures, selected among potentially suitable compounds for the OMBE trials, showed the reliability of the method proposed here.

The dynamic batch adsorption of methylene blue (MB), a widely used and toxic dye, onto nanocrystalline cellulose (NCC) and crushed powder of carbon monolith (CM) was investigated using the pseudo-first- and -second-order kinetics. CM outperformed NCC with a maximum capacity of 127 mg/g compared to 101 mg/g for NCC. The Langmuir isotherm model was applicable for describing the binding data for MB on CM and NCC, indicating the homogeneous surface of these two materials. The Gibbs free energy of -15.22 kJ/mol estimated for CM unravelled the spontaneous nature of this adsorbent for MB, appreciably faster than the use of NCC (-4.47 kJ/mol). Both pH and temperature exhibited only a modest effect on the adsorption of MB onto CM. The desorption of MB from CM using acetonitrile was very effective with more than 94 % of MB desorbed from CM within 10 min to allow the reusability of this porous carbon material. In contrast, acetonitrile was less effective than ethanol in desorbing MB from NCC. The two solvents were incapable of completely desorbing MB on commercial granular coal-derived activated carbon.