Abstract: Motivated by the successful preparation of MoSi2N4 monolayers in the last year [Y.-L. Hong et al., Science, 2020, 369, 670-674], we investigate the structural, electronic and optical properties of the MoS2/MoSi2N4 heterostructure (HTS). The phonon dispersion and the binding energy calculations refer to the stability of the HTS. The heterostructure has an indirect bandgap of 1.26 (1.84) eV using PBE (HSE06) which is smaller than the corresponding value of MoSi2N4 and MoS2 monolayers. We find that the work function of the MoS2/MoSi2N4 HTS is smaller than the corresponding value of its individual monolayers. The heterostructure structure can enhance the absorption of light spectra not only in the ultraviolet region but also in the visible region as compared to MoSi2N4 and MoS2 monolayers. The refractive index behaviour of the HTS can be described as the cumulative effect which is well described in terms of a combination of the individual effects (the refractive index of MoSi2N4 and MoS2 monolayers).

Abstract: Photoactive layers based on aryl- and aryloxy-substituted naphthalocyanines and conductive polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) were prepared using the spin-coating technique and their conductivity was tested in dark and under illumination. For this purpose novel octa-2-naphthoxy-substituted naphthalocyanines were synthesized starting from 6,7-di(2-naphthoxy)naphthalene-2,3-dicarbonitrile. For those novel naphthalocyanine complexes, spectral and electrochemical data were measured and compared with corresponding ones for other aryl-substituted analogues. In comparison to the previously studied naphthalocyanines with alkyl- and phenyl- groups, the formal oxidation and reduction potentials were rather similar. All target complexes demonstrate intense near-infrared absorption at 760-790 nm, which is about 30 nm bathochromically shifted in thin films. The photo-resistive effect was found increasing from composites comprised of naphthoxy- to phenyl-substituted naphthalocyanines. This peculiarity was explained by using optical and atomic force microscopy in terms of different sizes of aggregates formed. The photo-response time for novel composited was approximately 3 s, which is about 20 times faster than measured previously for the films deposited via the drop-casting technique.

Abstract: A pulsed microwave surfaguide discharge operating at 2.45 GHz was used for the conversion of molecular nitrogen into valuable compounds in several gas mixtures: N2 :O2 , N2 :O2 :CO2 and N2 :CO2 . The ro-vibrational absorption bands of the molecular species were monitored by a Fourier transform infrared apparatus in the post-discharge region in order to evaluate the relative number density of species, specifically NO production. The effects of specific energy input, pulse frequency, gas flow fraction, gas admixture and gas flow rate were studied for better understanding and optimization of the NO production yield and the corresponding energy cost (EC). By both the experiment and modelling, a highest NO yield is obtained at N2 :O2 (1:1) gas ratio in N2 :O2 mixture. The NO yield reveals a small growth followed by saturation when pulse repetition frequency increases. The energy efficiency start decreasing after the energy input reaches about 5 eV/molec, whereas the NO yield rises steadily at the same time. The lowest EC of about 8 MJ mol−1 corresponding to the yield and the energy efficiency of about 7% and 1% are found, respectively, in an optimum discharge condition in our case.

Abstract: Increasing plastic recycling rates is crucial to tackle plastic pollution and reduce consumption of fossil resources. Recycling routes for post-consumer plastic fractions that are technologically and economically feasible remain a challenge. Profitable value chains for recycling mixed film and tray-like plastics have hardly been implemented today, in sharp contrast to recycling of relatively pure fractions such as polyethylene terephthalate and high-density polyethylene bottles. This study examines the economic feasibility of implementing mechanical recycling for plastic waste such as polypropylene, polystyrene, polyethylene films and mixed polyolefins. In most European countries these plastic fractions are usually incinerated or landfilled whilst in fact technologies exist to mechanically recycle them into regranulates or regrinds. Results show that the economic incentives for the recycling of plastic packaging depend predominantly on the product price and product yield. At current price levels, the most profitable plastic fraction to be recycled is PS rigids, with an internal rate of return of 14%, whereas the least profitable feed is a mixed polyolefin fraction with a negative internal rate of return in a scenario with steadily rising oil prices. Moreover, these values would be substantially reduced if oil prices, and therefore plastic product prices decrease. Considering a discount rate of 15% for a 15-year period, mechanical recycling is not profitable if no policy changes would be imposed by governments. Clearly low oil prices may jeopardize the mechanical recycling industry, inducing the need for policies that would increase the demand of recycled products such as imposing minimal recycled content targets.

Abstract: The European automotive sector is faced with potentially disruptive challenges. In particular, the projected increase in the share of electric vehicles (EVs) and calls to prepare for the implementation of more circular economy (CE) strategies are increasingly demanding systemic adaptations. Given the goals of the CE, the adaptations should enable a maximal preservation of the function and value of products (e.g. extension of lifetime), components (e.g. reuse of parts) and materials (e.g., material recycling), thus saving on the energy, materials and effort that would be required to restore the lost functionalities. In this context, statistical entropy analysis (SEA) is proposed as a methodology to assess the effort needed for preserving and restoring functionality at different product, component and material life cycle stages. Effort is measured as changes in statistical entropy that are caused by concentration and dilution activities in the production – consumption – End-of-Life (EoL) system. SEA was applied to a generic model of the European automotive system, in combination with a stock-driven model and a material flow analysis (MFA), allowing statistical entropy changes to be projected over time. The paper demonstrates how SEA can facilitate decision making on the transition towards a more circular economy by quantifying the effects of particular CE strategies and their combinations. The results show that without any additional system adaptations, an increasing share of EVs towards the year 2050 will lead to substantially increased effort in production as well as end-of-life vehicle treatment.

Abstract: Boron neutron capture therapy (BNCT) is an extensively studied radiotherapeutic strategy for cancer treatment. BNCT is based on irradiation of malignant tumour cells with neutrons after uptake of a B-10 containing molecule. Alpha particles, locally produced by neutron irradiation kill the cancer cells. Important for ongoing research regarding cellular uptake and cytotoxicity of a large variety of B-10 containing molecules is the accurate determination of boron concentrations in cell cultures. In this work, the sample preparation for quantitative inductively coupled plasma mass spectrometry (ICP-MS) analysis on cell cultures was optimized. By making use of acid digestion combined with UV digestion, low detection limits (0.4 mu g L-1) and full recoveries of boron could be achieved while measurements were free of spectral and non-spectral interferences. Finally, cell-associated boron in the form of 4-borono-l-phenylalanine (l-BPA) in vascular endothelial cell cultures could be determined with ICP-MS as (1.26 +/- 0.10) x 10(9) boron atoms per cell. The developed method can prove its importance for further BNCT research and elemental analysis of cell cultures.

Abstract: Latest synthesis of ZnSb monolayer, encouraged us to conduct density functional theory (DFT) simulations in order to study the structural, magnetic, electronic/optical and mechanical features of the sp2-hybridized honeycomb ZnSb monolayer (ML-ZnSb) and bilayer (BL-ZnSb). Our structural optimizations reveal that ML-ZnSb is an anisotropic hexagonal structure while BL-ZnSb is composed of shifted ZnSb layers which are covalently binded. ML-ZnSb is found to be a ferromagnetic metal, in contrast BL-ZnSb has a non-magnetic indirect band gap semiconducting ground state. For the in-plane polarization, first absorption peak of ML-ZnSb and BL-ZnSb confirm the absorbance of the light within the infrared domain wand visible range, respectively. Moreover, our results reveal that the layer-layer chemical bonding in BL-ZnSb significantly enhances the mechanical response of ML-ZnSb whose in-plane stiness is the smallest among all 2D materials (2DM). Notably, the strong in-plane anisotropy of ML-ZnSb in its stiness reduces in BL-ZnSb.

Abstract: Three-dimensional topological insulators are exotic materials with unique properties. Tetradymite type binary chalcogenides of bismuth and antimony, as well as their mixed crystals, belong to prototypical TIs. Potential device applications of these materials require in-depth knowledge of their stability in the ambient atmosphere and other media maintained during their processing. Here we investigated the reactivity of mixed crystals with anion substitution, Bi-2(Se1-xTex)(3) and Sb2(Se1-xTex)(3), towards molecular oxygen using both in situ and ex situ X-ray photoelectron spectroscopy. The results indicate that, in contrast to cation substitution, partial substitution of tellurium by selenium atoms leads to anomalously high surface reactivity, which even exceeds that of the most reactive binary constituent. We attribute this effect to anion ordering that essentially modifies the bond geometry, especially the respective bond angles as modeled by DFT.

Abstract: The two dimensional MoSi2N4 (MSN) monolayer exhibiting rich physical and chemical properties was synthesized for the first time last year. We have used the spin-polarized density functional theory to study the effect of different types of point defects on the structural, electronic, and magnetic properties of the MSN monolayer. Adsorbed, substitutionally doped (at different lattice sites), and some kind of vacancies have been considered as point defects. The computational results show all defects studied decrease the MSN monolayer band gap. We found out the H-, O-, and P-doped MSN are n-type conductors. The arsenic-doped MSN, and MSN with vacancy defects have a magnetic moment. The MSN with a Si vacancy defect is a half-metallic which is favorable for spintronic applications, while the MSN with a single N vacancy or double vacancy (N + S) defects are metallic, i. e., beneficial as spin filters and chemical sensors.

Abstract: In this Letter, we explore the lattice, dynamical stability, and electronic and magnetic properties of FeTe bulk and FeX (X=S, Se, Te) monolayers using the density functional calculations. The phonon dispersion relation, elastic stability criteria, and cohesive energy results show the stability of studied FeX monolayers. The mechanical properties reveal that all FeX monolayers have a brittle nature. Furthermore, these structures are stable as we move down the 6A group in the periodic table, i.e., from S, Se, and Te. The stability and work function decrease as the electronegativity decreases. The spin-polarized electronic structures demonstrate that the FeTe monolayer has a total magnetization of 3.8 mu (B), which is smaller than the magnetization of FeTe bulk (4.7 mu (B)). However, FeSe and FeS are nonmagnetic monolayers. The FeTe monolayer can be a good candidate material for spin filter applications due to its electronic and magnetic properties. This study highlights the bright prospect for the application of FeX monolayers in electronic structures.

Abstract: Duplexed aptamers (DAs) are widespread aptasensor formats that simultaneously recognize and signal the concentration of target molecules. They are composed of an aptamer and aptamer complementary element (ACE) which consists of a short oligonucleotide that partially inhibits the aptamer sequence. Although the design principles to engineer DAs are straightforward, the tailored development of DAs for a particular target is currently based on trial and error due to limited knowledge of how the ACE sequence affects the final performance of DA biosensors. Therefore, we have established a thermodynamic model describing the influence of the ACE on the performance of DAs applied in equilibrium assays and demonstrated that this relationship can be described by the binding strength between the aptamer and ACE. To validate our theoretical findings, the model was applied to the 29-mer anti-thrombin aptamer as a case study, and an experimental relation between the aptamer-ACE binding strength and performance of DAs was established. The obtained results indicated that our proposed model could accurately describe the effect of the ACE sequence on the performance of the established DAs for thrombin detection, applied for equilibrium assays. Furthermore, to characterize the binding strength between the aptamer and ACEs evaluated in this work, a set of fitting equations was derived which enables thermodynamic characterization of DNA-based interactions through thermal denaturation experiments, thereby overcoming the limitations of current predictive software and chemical denaturation experiments. Altogether, this work encourages the development, characterization, and use of DAs in the field of biosensing.

Abstract: Three-dimensional topological insulator (3D TI) nanowires display remarkable magnetotransport properties that can be attributed to their spin-momentum-locked surface states such as quasiballistic transport and Aharonov-Bohm oscillations. Here, we focus on the transport properties of a 3D TI nanowire with a gated section that forms an electronic Fabry-Perot (FP) interferometer that can be tuned to act as a surface-state filter or energy barrier. By tuning the carrier density and length of the gated section of the wire, the interference pattern can be controlled and the nanowire can become fully transparent for certain topological surface-state input modes while completely filtering out others. We also consider the interplay of FP interference with an external magnetic field, with which Klein tunneling can be induced, and transverse asymmetry of the gated section, e.g. due to a top-gated structure, which displays an interesting analogy with Rashba nanowires. Due to its rich conductance phenomenology, we propose a 3D TI nanowire with gated section as an ideal setup for a detailed transport-based characterization of 3D TI nanowire surface states near the Dirac point, which could be useful towards realizing 3D TI nanowire-based topological superconductivity and Majorana bound states.

Abstract: Biomass fast pyrolysis has been considered one of the best alternatives for the thermal conversion of biomass into bio-oil. This work introduces a new reactor technology for biomass fast pyrolysis, the Gas-Solid Vortex Reactor (GSVR), to obtain high bio-oil yields. The GSVR was designed to decrease the residence time of the pyrolysis vapors; thus, the secondary cracking reactions are reduced, to enhance the segregation of the char and the unreacted biomass and to improve the heat transfer rate. Biomass fast pyrolysis experiments have been carried out for the first time in a Gas-Solid Vortex Reactor (GSVR) at 773 K, using softwood (pine) and hardwood (poplar) as feedstock. Char yields as low as 10 wt. % in the GSVR were comparable to those reported for the same feedstocks processed in conventional fluidized bed reactors. The yields of non-condensable gases in the range of 15–17 wt. % were significantly lower than those reported for other commonly used biomass fast pyrolysis reactors. Two-dimensional gas chromatography (GC × GC) revealed noticeable differences at the molecular level between the bio-oils from the GSVR and bio-oils from other reactors. The aromatics in the pine bio-oil consist almost entirely (85 wt. %) of guaiacols. For poplar bio-oils no predominant group of aromatics was found, but phenolics, syringols, and catechols were the most pronounced. The experimental results highlight the advantages of the GSVR for biomass pyrolysis, reaching stable operation in around 60 s, removing the formed char selectively during operation, and enabling fast entrainment of pyrolysis vapors. Results indicate a great potential for increasing yield and selectivity towards guaiacols in softwood (e.g., pine) bio-oil. Likewise, decreasing pyrolysis temperature could increase the yield of guaiacols and syringols in hardwood (e.g., poplar) bio-oil.

Abstract: We report on cooperative grain rotation accompanied by a strong Bauschinger effect in nanocrystalline (nc) palladium thin film. A thin film of nc Pd was subjected to cyclic loading-unloading using in situ TEM nanomechanics, and the evolving microstructural characteristics were investigated with ADF-STEM imaging and quantitative ACOM-STEM analysis. ADF-STEM imaging revealed a partially reversible rotation of nanosized grains with a strong out-of-plane component during cyclic loading-unloading experiments. Sets of neighboring grains were shown to rotate cooperatively, one after the other, with increasing/decreasing strain. ACOM-STEM in conjunction with these experiments provided information on the crystallographic orientation of the rotating grains at different strain levels. Local Nye tensor analysis showed significantly different geometrically necessary dislocation (GND) density evolution within grains in close proximity, confirming a locally heterogeneous deformation response. The GND density analysis revealed the formation of dislocation pile-ups at grain boundaries (GBs), indicating the generation of back stresses during unloading. A statistical analysis of the orientation changes of individual grains showed the rotation of most grains without global texture development, which fits to both dislocation- and GB sliding-based mechanisms. Overall, our quantitative in situ experimental approach explores the roles of these different deformation mechanisms operating in nanocrystalline metals during cyclic loading.

Abstract: We report morpho-structural properties and charge conduction mechanisms of a foamy “graphene sponge ”, having a density as low as & AP;0.07 kg/m3 and a carbon to oxygen ratio C:O & SIME; 13:1. The spongy texture analysed by scanning electron microscopy is made of irregularly-shaped millimetres-sized small flakes, containing small crystallites with a typical size of & SIME;16.3 nm. A defect density as high as & SIME;2.6 x 1011 cm-2 has been estimated by the Raman intensity of D and G peaks, dominating the spectrum from room temperature down to & SIME;153 K. Despite the high C:O ratio, the graphene sponge exhibits an insulating electrical behavior, with a raise of the resistance value at & SIME;6 K up to 5 orders of magnitude with respect to the room temperature value. A variable range hopping (VRH) conduction, with a strong 2D character, dominates the charge carriers transport, from 300 K down to 20 K. At T < 20 K, graphene sponge resistance tends to saturate, suggesting a temperature-independent quantum tunnelling. The 2D-VRH conduction originates from structural disorder and is consistent with hopping of charge carriers between sp2 defects in the plane, where sp3 clusters related to oxygen functional groups act as potential barriers.</p>