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The phase behavior of hydrocarbon fluids confined in porous media has been reported to deviate significantly from that in the bulk environment due to the existence of sub-10 nm pores. Though experiments and simulations have measured the bubble/dew points and sorption isotherms of hydrocarbons confined in both natural and synthetic nanopores, the confinement effects in terms of the strength of fluid-pore interactions tuned by surface wettability and chemistry have received comparably less discussion. More importantly, the underlying physics of confinement-induced phenomena remain obfuscated. In this work, we studied the phase behavior and capillary condensation of n -hexane to understand the effects of confinement at the molecular level. To systematically investigate the pore effects, we constructed two types of wall confinements; one is a structureless virtual wall described by the Steele potential and the other one is an all-atom amorphous silica structure with surface modified by hydroxyl groups. Our numerical results demonstrated the importance of fluid-pore interaction, pore size, and pore morphology effects in mediating the pressure-volume-temperature (PVT) properties of hydrocarbons. The most remarkable finding of this work was that the saturation pressure predicted from the van der Waals-type adsorption isothermal loop could be elevated or suppressed relative to the bulk phase, as illustrated in the graphical abstract. As the surface energy (i.e., fluid-pore interaction) decreased, the isothermal vapor pressure increased, indicating a greater preference for the fluid to exist in the vapor state. Sufficient reduction of the fluid-pore interactions could even elevate the vapor pressure above that of the bulk fluid.

With structural miniaturization down to the nanoscale, some detectable parameters of materials no longer remain constant. For NiO nanoparticles example, Raman shift and Néel temperature increase while optical band gap decreases with increasing the nanoparticle size. Herein, we developed the analytic models to describe the size dependence of these above-mentioned seemingly uncorrelated parameters for NiO nanoparticles, based on the average coordination number-dependent cohesive energy model. Consistency between our theoretical predictions and the corresponding experimental results not only verified the accuracy of our developed models but also provided insight into the essentiality of cohesive energy in describing the effect of size on the materials properties of NiO nanoparticles.

The magnetism of hole doped 1T-MX 2 (M = Zr, Hf; X = S, Se) monolayers is systematically studied by using first principles density functional calculations. The pristine 1T-MX 2 monolayers are semiconductors with nonmagnetic ground states, which can be transformed to ferromagnetic states by the approach of hole doping. For the unstrained monolayers, the spontaneous magnetization appears once above the critical hole density (10 14 cm -2 ), where the p orbital of S or Se atoms contributes the most of the magnetic moment. As the tensile strains exceed 4%, the magnetic moments per hole of ZrS 2 and HfS 2 monolayers increase sharply to a saturated value with increasing hole density, implying obvious advantages over the unstrained monolayers. The phonon dispersion calculations for the strained ZrS 2 and HfS 2 monolayers indicate that they can keep the dynamical stability by hole doping. Furthermore, we propose that the fluorine atom modified ZrS 2 monolayer could obtain stable ferromagnetism. The magnetism in hole doped 1T-MX 2 (M = Zr, Hf; X = S, Se) monolayers has great potential for developing spintronic devices with desirable applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Bismuth triiodide, BiI 3 , is one of the promising 2D layered materials from the family of metal halides. The unique electronic structure and properties make it an attractive material for the room-temperature gamma/X-ray detectors, high-efficiency photovoltaic absorbers, and Bi-based organic-inorganic hybrid perovskites. Other possibilities including optoelectronic devices and optical circuits are envisioned but rarely experimentally confirmed yet. Here, we report the synthesis of vertical 2D BiI 3 nanoplates using the physical vapor deposition mechanism. The obtained products were found easy to be separated and transferred to other substrates. Photodetectors employing such 2D nanoplates on polyethylene terephthalate substrate are demonstrated to be quite sensitive to red light (635 nm) with good responsivity (2.8 A W -1 ), fast stable photoresponse (3/9 ms for raise/decay times), and remarkable specific detectivity (1.2 × 10 12 jones), which attest to high comparability of the assembled components with many latest 2D nanostructured light sensors. In addition, such photodetectors exhibit outstanding mechanical stability and durability under different bending strains within the theoretically affordable levels, suggesting a variety of potential applications of 2D BiI 3 for flexible devices.

We propose a two-dimensional (2D) tetragonal material: an yttrium nitride (t-YN) monolayer, with a distinguished combination of mechanical and electronic properties based on first-principles calculations. We find that the t-YN monolayer is a low direct band gap semiconductor (0.55 eV) with strong anisotropic mechanical and electronic properties. We also identify that the t-YN monolayer to be a 2D ferroelastic material with a reversible strain of about 14.4%, indicating that the anisotropic properties of the t-YN monolayer can be switched by applying external stress. Furthermore, the moderate-switching barrier (33 meV/atom) of ferroelastic lattice rotation renders the switchable anisotropic properties accessible experimentally. These outstanding properties make the t-YN monolayer a promising switchable anisotropic 2D material for electronic and mechanical applications.

Using first-principles calculations, we designed a two-dimensional material, monolayer AgBiP 2 Se 6 , with the thickness of only 6 Å, which exhibited out-plane ferroelectricity. The ground state of the monolayer AgBiP 2 Se 6 was not purely ferroelectric since the out-plane ferroelectricity originated from the compensated ferrielectric state: the off-centering antiparallel displacements of Ag + and Bi 3+ ions. The compensated ferrielectric ordering has superiority on reducing the depolarization field to stabilize the ferroelectricity. Furthermore, together with strong visible-light adsorption and suitable band edge alignments, we proposed the monolayer AgBiP 2 Se 6 as a visible-light photocatalyst for water-splitting as the out-plane polarization could enhance the electron-hole separation. Our results offer a new way to overcome the critical thickness limitation of nanoscale ferroelectrics. The out-plane ferroelectricity in monolayer AgBiP 2 Se 6 has great potential for developing various devices with desirable applications.

By first-principles calculations, the magnetism of hole doped tin dichalcogenides SnX 2 (X = S, Se) monolayers is systematically studied. It is found that a phase transition from nonmagnetic to ferromagnetic ground state appears once above the critical hole density (~10 14  cm -2 ). The spin magnetic moment can maintain a magnitude of 1.0 μ B /hole with excellent stability of ferromagnetic state. Furthermore, we demonstrate that strain is very useful to modulate the DOS near the valence band, resulting in the reduction of the critical hole density to ~10 13  cm -2 when the strain reaches 4% (6%) in SnS 2 (SnSe 2 ), which can be realized in common field effect transistors. Moreover, the phonon dispersion calculations for the strained SnX 2 monolayers indicate that they can keep the dynamical stability under the hole doping. Therefore, the strain tunable magnetic transition in hole doped tin dichalcogenides indicates their potential promising applications in spintronic devices.

Ferroelectric tunnel junctions (FTJs) are quantum nanostructures that have great potential in the hardware basis for future neuromorphic applications. Among recently proposed possibilities, the artificial cognition has high hopes, where encoding, training, memory solidification and retrieval constitute a whole chain that is inseparable. However, it is yet envisioned but experimentally unconfirmed. The poor retention or short-term store of tunneling electroresistance, in particular the intermediate states, is still a key challenge in FTJs. Here we report the encoding, training and retrieval in BaTiO3 FTJs, emulating the key features of information processing in terms of cognitive neuroscience. This is implemented and exemplified through processing characters. Using training inputs that are validated by the evolution of both barrier profile and domain configuration, accurate recalling of encoded characters in the retrieval stage is demonstrated.

The structural and optical characterizations of titania incorporated with alumina nanocrystals have been presented in this paper and the films exhibit excellent properties like low current density, small hysteresis as well as high photoluminescence quantum yields of about 361 nm. These properties are promising for the applications in future electronic devices.