The next nearest neighbor (NNN) interaction is sometimes non-negligible for the application of spintronic devices in magnetic materials. Thus, understanding the contribution of the NNN interaction has been a significant research target. Although numerous approaches have been explored to control the NNN interaction, few reports of the competition of the NNN interaction of heterogeneous bilayer films have been presented. In this work, the spin wave resonance frequency of ferromagnetic heterogeneous bilayer films with the NNN interaction has been investigated using the linear spin wave approximation and Green's function methods. To clarify the contribution of the NNN interaction, the effects of the characteristic parameters of the system, such as interface coupling, surface anisotropy, external magnetic field, film thicknesses and symmetry, on the spin wave resonance frequency have also been studied in detail. It is found that the spin wave resonance frequencies of three lower-frequency modes depend strongly on the thickness of film. The frequency gap between the two neighbor modes is broadened when the thickness of the film is decreased. Besides, the NNN interaction and the symmetry play an important role in increasing the spin wave resonance frequency. Moreover, it is worth noting that the spin wave resonance frequency of the lowest-frequency mode depends weakly on the NNN interaction, the interface coupling, and the symmetry. Considering these effects in an opportune way, the spin wave resonance frequency of ferromagnetic thin film system can be controlled.

The experimental knowledge of the AlSb monolayer with a double-layer honeycomb structure is largely based on a recent publication [Le Qin et al., ACS Nano 2021, 15, 8184]. In the present work, we aim to explore the effect of phosphorus alloying on the structural, electronic, and optical properties of the AlSb monolayer (AlSbxP1-x). Phonon dispersion curves and cohesive energies, along with the Born criterion, demonstrate the stability of these structures. Our results show that with increasing P-concentration (from 0.375 to 1.0), the bandgaps increase to 1.25 eV, PBE (1.15 eV, PBE + SOC) for the alloyed AlSb structure with 0.875 P content, and an increase of 0.95 eV (PBE) and 0.56 eV (PBE + SOC) compared to that of the pristine AlSb bandgap. The largest bandgap is calculated to be 1.7 eV, PBE (1.65, PBE + SOC) for the AlP monolayer. Interestingly, for all P-concentrations, the bandgaps are direct, signifying potential applications of the material in photovoltaic applications. For P-contents from P = 0 to 0.375, the bandgap initially slightly decreases. The adsorption spectra are also found to depend on the concentration of P-dopant, where low concentration is found to be better than the high concentration for adsorption in the visible light range, while high concentration is better than low concentration for ultraviolet radiation. The variation of the bandgap with P-dopant concentration suggests the potential of these monolayer alloys for tunable bandgap engineering and application in future nano-optoelectronic devices.

Natural purification of pollutants is highly recognized as regulating ecosystem services; however, the purification capacity of tidal flats remains largely unknown and/or unquantified. A 60-day mesocosm transplant experiment was conducted in situ to assess the purification capacity of natural tidal flats. We adopted the advanced sediment quality triad approach, monitoring 10 endpoints, including chemical reduction, toxicity changes, and community recoveries. The results indicated that contaminated sediments rapidly recovered over time, particularly > 50% within a day, then slowly recovered up to ∼ 70% in a given period (60 days). A significant early reduction of parent pollutants was evidenced across all treatments, primarily due to active bacterial decomposition. Notably, the presence of benthic fauna and vegetated halophytes in the treatments significantly enhanced the purification of pollutants in both efficacy and efficiency. A forecast linear modeling further suggested additive effects of biota on the natural purification of tidal flats, reducing a full recovery time from 500 to 300 days. Overall, the triad approach with machine learning practices successfully demonstrated quantitative insight into the integrated assessment of natural purification.

Metallic characteristics of the recently synthesized two-dimensional Mo atoms (referred to as molybdenene) [] promise significant potential for applications in molecular sensing, electron imaging, and scanning probe microscopy. In this work, the structural stability and electronic and optical properties of potential phases of a two-dimensional (2D) molybdenene monolayer have been investigated by employing comprehensive density functional theory. While the phonon dispersion spectra of possible molybdenene structures reveal dynamic and phase instability in free-standing, perfectly flat molybdenene sheets, our results identify two phases of molybdenene monolayers with energetic and dynamic stabilities: a buckled hexagonal structure and a zigzag-shaped structure. Further analysis of the electronic and optical properties of these predicted monolayer materials reveals that all of them exhibit a metallic nature. Additionally, we investigated the possible formation of two-dimensional double-layer molybdenene and found two highly stable structures derived from the zigzag structure and three from the buckled hexagonal structure, all of which are more favorable than the corresponding parent monolayer structures. Finally, the synthesizability of two-dimensional MoC monolayers, which have recently attracted significant attention due to their promising catalytic applications, has also been investigated. Our findings suggest that the bottom-up design is theoretically possible based on molybdenene and T-carbon structure as reactants.

In this work, we present a novel two-dimensional (2D) Si2BN structure (2D δ-Si2BN) predicted using density functional theory (DFT). The proposed structure exhibits a unique double quasi-planar layer interconnected by...

Recent exciting developments in synthesis and properties study of the germanane (GeH) mono-layer have inspired us to investigate the structural and electronic properties of the van der Waals heterostructures (HTS) of GeH/InSe and GeH/In2Se3 through a first-principles methodology. In this study, structural and electronic properties of the HTS are examined thoroughly. GeH/InSe and GeH/In2Se3 are determined as n-type Schottky with a Schottky barrier height (SBH) of 0.40 eV and n-type ohmic, respectively. GeH/InSe turns out as a semiconductor with a direct bandgap of 0.62 eV, while GeH/In2Se3 is seen to be a metal. The results show that changing of the bandgap and SBH in very small values. For GeH/In2Se3 the effects are even less substantial, as the metallic or n-type nature of the material does not change. The biaxial strain and electric field have more tangible effects on the characteristics of the HTS. A mixture of compressive and tensile strain is seen to have the capability of changing GeH/InSe into a metal and at the same time transform it to an n-type/p-type ohmic or p-type Schottky contact. The results given here can guide future research in the field of HTS and especially GeH-based devices.

Two-dimensional (2D) materials can be effectively functionalized by chemically modified using doping. Very recently, a flat AgSe monolayer was successfully prepared through direct selenization of the Ag(111) surface. Besides, the results indicate that the AgSe monolayer like CuSe, has a honeycomb lattice. Motivated by the experimental outcomes, in this work, employing first-principles calculations, we systematically investigate the electronic and optical properties of AgSe and CuSe monolayers, as well as the impact of alkali metals (Li, Na and K). Without functionalization, both the CuSe and AgSe monolayers exhibit metallic characteristics. The Li (Na)-CuSe and Na (K)-AgSe systems are dynamically stable while, the K- and Li-CuSe and Li-AgSe are dynamically unstable. Interestingly, the functionalized CuSe system with Li and Na atom as well as AgSe with K and Na atom, can open the band gaps, leading to the actualization of metal to semiconductor transitions. Our results show that, the electronic characteristics of the Na-CuSe/AgSe system can be modulated by adjusting the adsorption heights, which gives rise to the change in the electronic properties and the band gap may be controlled. Furthermore, from the optical properties we can find that the K-AgSe system is the best candidate monolayer to absorb infrared radiation and visible light. Consequently, our findings shed light on the functionalization of 2D materials based CuSe and AgSe monolayers and can potentially enhance and motivate studies in producing these monolayers for current nanodevices and future applications.

The experimental knowledge of two-dimensional penta-like PdPSe monolayer is largely based on a recent publication (Liet al2021Adv. Mater. 2102541). Therefore, the aim of our research is consequently to explore the effect of vacancy defects and substitutional doping on the electronic properties of the novel penta-PdPSe monolayer by using first-principles calculations. Penta-like PdPSe is a semiconductor with an indirect bandgap of 1.40 eV. We show that Pd and Se vacancy defected structures are semiconductors with band gaps of 1.10 eV and 0.95 eV respectively. While P single vacancy and double vacancy defected structures are metals. The doping with Ag (at Pd site) and Si (at P site) convert the PdPSe to nonmagnetic metallic monolayer while the doping with Rh (at Pd site), Se (at P site) and As (at site Se) convert it to diluted magnetic semiconductors with the magnetic moment of 1µB. The doping with Pt (at the Pd site), As (at the P site), S and Te (at Se site) are indirect semiconductors with a bandgap of ∼1.2 eV. We undertook this theoretical study to inspire many experimentalists to focus on penta-like PdPSe monolayer growth incorporating different impurities and by defect engineering to tune the novel two dimensional materials (PdPSe) properties for the advanced nanoelectronic application.

In this work, employing first-principles calculations, we systematically investigate the atomic structure and electronic and optical properties of the AgTe monolayer, as well as the impact of alkali metal (Li, Na, K) and alkaline earth metal (Be, Mg, Ca) atoms decoration. The AgTe monolayer exhibits metallic characteristics. When Li, Na, K, and Mg atoms are decorated on the AgTe monolayer, the decorated AgTe monolayers are dynamically stable. In contrast, with Be and Ca atoms, the decorated structures are found to be dynamically unstable. Interestingly, the decoration of Li, Na, and K atoms into the AgTe monolayer can open the band gaps in the decorated Li-, Na- and K-AgTe monolayers around the Fermi level, leading to the actualization of metal-to-semiconductor transitions. In contrast, the decorated Mg-AgTe monolayer maintains its metallic characteristic. The highest electron and hole mobilities are achieved in the Na-AgTe monolayer among the decorated structures, suggesting the applicability of this structure in photovoltaic applications. The optical study shows that Li-, Na- and K-decorated AgTe monolayers have improved light absorption in the visible light region. Consequently, our findings shed light on the decoration of these 2D material monolayers and can potentially enhance and motivate studies in producing these monolayers for current nanodevices and future applications.

This work explores a mechanism behind hysteresis in CH3NH3PbI3 perovskite solar cells. The solar cells in this work employed either compact TiO2, mesoporous TiO2, or a combination of compact and mesoporous TiO2 as an electron transport layer. The solar cells using compact TiO2 layer displayed the most pronounced hysteresis compared to those which made use of mesoporous TiO2. Different hysteretic behavior is attributed to difference in the built–in electric fields present in the architecture of perovskite solar cell. The solar cells with a compact TiO2 layer have a built-in field which allows for iodide ions to migrate and accumulate near to the interface of indium-tin-oxide electrode, ultimately causing a reduction in the measured power conversion efficiency for forward bias scans. In case of the cells with a mesoporous TiO2 layer, they have the built–in fields configured in such a way that iodide ions are blocked from migrating on a large scale to the vicinity of the ITO electrode. This results in the reduced hysteresis in perovskite solar cells when a mesoporous TiO2 electron transport layer is employed.

Ligand-specific binding interactions of xenobiotics with receptor proteins form the basis of cytotoxicity-based hazard assessment. Computational approaches enable predictive hazard assessment for a large number of chemicals in a high-throughput manner, minimizing the use of animal testing. However, in silico models for predicting mechanisms of toxic actions and potencies are difficult to develop because toxicity datasets or comprehensive understanding of the complicated kinetic process of ligand-receptor interactions are needed for model development. In this study, a directional reactive binding factor (DRBF) model based on first principles was used to predict cytotoxicity potencies of agonists of the aryl hydrocarbon receptor (AhR) for 16 different polycyclic aromatic hydrocarbons (PAHs). Molecular dynamics were simulated by accounting for the directional configuration factor toward receptor protein and the factor of binding to the Per-Arnt-Sim (PAS) domain. When comparing the experimental results of toxic potencies from in vitro bioassays with the predictions among two different in silico models, including quantitative structure-activity relationship (QSAR) and molecular docking models, the DRBF model exhibited the highest model performance (R2 = 0.90 and p < 0.01). Our results showed that the DRBF model based on first principles and molecular and computational structural biology could serve as a novel framework to advance next generation hazard assessment for high-throughput screening of chemical substances.

Ecotoxicological effects of spilled oils are well documented, but study of recovery of marine benthic communities is limited. Long-term recovery of hard bottom communities during physical and biological remediations after a spill was monitored. A 60-day experiment was conducted using a mesocosm with monitoring of eight endpoints by use of the sediment quality triad (SQT). First, physical treatment of hot water + high pressure flushing maximally removed residual oils (max=93%), showing the greatest recovery among SQT variables (mean=72%). Physical cleanup generally involved adverse effects such as depression of the microphytobenthic community

Organic solar cells (OSCs) have received considerable attention as a promising clean energy-generating technology because of their low cost and great potential for large-scale commercial manufacturing. With significant advances in new charge-transport material design, interfacial engineering, and their operating conditions, power conversion efficiencies of OSCs have continued to increase. However, a fundamental understanding of charge carrier transport and especially how ionic moieties affect carrier transport is still lacking in OSCs. In this regard, photoelectron spectroscopy has provided valuable information about interfacial electronic structures. The interfacial electronic structure of OSC interlayers greatly impacts charge extraction and recombination, controls energy level alignment, guides active layer morphology, improves material’s compatibility, and plays a critical role in the resulting power conversion efficiency of OSCs. Interfacial engineering incorporating inorganic, organic, and hybrid materials can effectively enhance the performance of organic photovoltaic devices by reducing energy barriers for charge transport and injection while improving compatibility between metal oxides and donor–acceptor based active layers or transparent conducting electrodes. This article provides a review of recent developments in interfacial engineering underlying organic photovoltaic devices of donor–acceptor interfaces.

Linear spin-wave approximation and Green's function were used to study the dependence of spin wave resonance (SWR) frequency in a ferromagnetic film considering the external magnetic field, surface anisotropy, number of atomic layers, nearest and next nearest neighbor interaction. A systematic study of the SWR frequency as a function of external magnetic field, surface anisotropy, and next nearest neighbor interaction was performed. It demonstrates that the next nearest neighbor interaction affects strongly on the SWR frequencies of energetically higher modes, as well as the gap of resonance frequency between the highest and lowest energy modes is broaden as the next nearest neighbor interaction increasing. Moreover, we show that SWR frequencies at two higher energy modes are coincided when the surface anisotropy increases. Finally, as the thickness of film decreases, SWR frequency of the lowest energy mode is shifted to higher value. Thus, considering these effects in an opportune way, we are able to control the SWR frequency of the system.

Understanding what and how physico-chemical factors of a ligand configure conditions for ligand-receptor binding is a key to accurate assessment of toxic potencies of environmental pollutants. We investigated influences of the dipole-driven orientation and resulting directional configuration of ligands on receptor binding activities. Using physico-chemical properties calculated by ab initio density functional theory, directional reactivity factors (DRF) were devised as main indicators of toxic potencies, linking molecular ligand-receptor binding to in vitro responses. The directional reactive model was applied to predict variation of aryl hydrocarbon receptor-mediated toxic potencies among homologues of chrysene with structural modifications such as the numbers of constituent benzene rings, methylation and hydroxylation. Results of predictive models were consistent with empirical potencies determined by use of the H4IIE-luc transactivation bioassay. The experiment-free approach based on first principles provides an analytical framework for estimating molecular bioactivity in silico and complements conventional empirical approaches to studying molecular initiating events in adverse outcome pathways.

The regulating services by natural tidal flats to purify organic pollutants are increasingly recognized, but a quantitative assessment is very limited. We developed a mesocosm system to determine removal efficiency of organic matters and nutrients by simulating a natural tidal condition. The tidal flat sediments significantly removed waterborne organic pollutants to background levels in ~2 and 6-7 days for COD and TP, respectively. This rapid removal of organic matters by natural sediments could be attributed to the microbe community degrading the corresponding pollutants. Temporal trend and degree of removal rates for COD and TP were similar between the bare tidal flat and the salt marsh. Meantime, the salt marsh environment removed waterborne DIP much quickly and also efficiently, implying a high affinity of halophytes on dissolved organic matters. Of note, sedimentary organic sink prevailed in defaunated condition under the smaller bioturbation effect. A mini-review on the purification capacity of natural and/or constructed coastal wetlands generally supported a high efficiency of vegetation to remove various sources of organic matters.

Multi-wall carbon nanotubes (MWCNT) filled with Fe nanorods were shown to have contracted and deformed under heavy ion irradiation. In this study, 120 MeV Ag and 80 MeV Ni ion irradiation was performed to study the deformation and defects induced in iron filled MWCNT under heavy ion irradiation. The structural modifications induced due to electronic excitation by ion irradiation were investigated employing high-resolution transmission electron microscopy, micro-Raman scattering experiments, and synchrotron-based X-ray absorption and emission spectroscopy. We understand that the ion irradiation causes modifications in the Fe nanorods which result in compressions and expansions of the nanotubes, and in turn leads to the buckling of MWCNT. The G band of the Raman spectra shifts slightly towards higher wavenumber and the shoulder G' band enhances with the increase of ion irradiation fluence, where the buckling wavelength depends on the radius 'r' of the nanotubes as exp[(r)(0.5)]. The intensity ratio of the D to G Raman modes initially decreases at the lowest fluence, and then it increases with the increase in ion fluence. The electron diffraction pattern and the high resolution images clearly show the presence of ion induced defects on the walls of the tube and encapsulated iron nanorods. Crown Copyright (C) 2017 Published by Elsevier B.V. All rights reserved.

We report the results of X-ray spectroscopy and Raman measurements of as-prepared graphene on a high quality copper surface and the same materials after 1.5 years under different conditions (ambient and low humidity). The obtained results were compared with density functional theory calculations of the formation energies and electronic structures of various structural defects in graphene/Cu interfaces. For evaluation of the stability of the carbon cover, we propose a two-step model. The first step is oxidation of the graphene, and the second is perforation of graphene with the removal of carbon atoms as part of the carbon dioxide molecule. Results of the modeling and experimental measurements provide evidence that graphene grown on high-quality copper substrate becomes robust and stable in time (1.5 years). However, the stability of this interface depends on the quality of the graphene and the number of native defects in the graphene and substrate. The effect of the presence of a metallic substrate with defects on the stability and electronic structure of graphene is also discussed.

A SnOx/Au/SnOx transparent conductive oxide (TCO) multilayered film was fabricated with a total thickness of 75 nm using both e-beam and thermal evaporation techniques.

p and n type SnOx thin films are successfully functionalized with optically active Nd3+ ions for efficient UV photon conversion.