Dimensional Transition Research Articles

Chlorine vacancy−induced activation in two−dimensional transition metal dichlorides nanosheets for efficient CO electroreduction to C2+ products

Chlorine vacancy−induced activation in two−dimensional transition metal dichlorides nanosheets for efficient CO electroreduction to C2+ products

Chirality-Mediated 1D-to-2D Phase Transition in Hybrid Lead Halide Perovskites.

Dimensionality engineering plays a pivotal role in optimizing the performance, ensuring long-term stability, and expanding the versatile applications of lead halide perovskites (LHPs). Currently, the manipulation of LHP dimensions primarily occurs during the synthesis stage, a procedure hampered by constraints, including synthetic complexity and irreversibility. This investigation successfully achieved a transition from one-dimensional (1D) to two-dimensional (2D) structures in chiral LHPs by applying hydrostatic pressure. Remarkably, this pressure-induced transition in dimensionality is absent in the racemic analogue due to the staggered arrangement of inorganic chains and the elevated steric hindrance posed by the organic cations. Notably, the hydrogen bonding between organic cations and the inorganic framework adopts a symmetrical arrangement in the racemic system but a helical configuration along the 1D chain direction in the chiral counterparts. This distinct helical arrangement induces a consequential distortion in the inorganic moiety, resulting in the emergence of a spin-polarized Rashba-Dresselhaus texture that explains the chirality's electronic spin origin. Furthermore, both experimental and density functional theory calculation results demonstrate that the 1D-to-2D phase transition in chiral halide perovskites can induce significant modifications in the electronic structures and associated optical emissions. In summary, the findings unveil novel avenues for manipulating optoelectronic properties in chiral perovskites through dimensionality engineering.

Four-state Fano resonance electro-optical modulator and sensor based on double borophene-dielectric grating structure

In this paper, we propose a borophene-based double-dielectric-grating structure (BDDGS) to realize the Fano resonance electro-optical modulator and sensor. The Fano resonance originated from the coupling of two resonance modes excited by the upper borophene grating (UBG) and the lower borophene grating (LBG). The coupling mode theory (CMT) is utilized to fit the Fano transmission spectrum. The calculated result fits well with the simulated spectrum. We found the Fano resonance wavelengths exhibit a blue shift with increasing the carrier density of the borophene layer. Further, we utilize this property to achieve a Four-state Fano resonance electro-optical modulator. The working wavelengths of the ON-ON (11), ON–OFF (10), OFF–ON (01), and OFF-OFF (00) states are 1.321 μm and 1.676 μm, respectively. The asymmetric Fano spectra exhibit high sensing sensitivity S=21THz/RIU and figure of merit FOM=3.9RIU−1. Moreover, our proposed structure possesses a slow-fast light effect with the maximum group index are 57.84 and −332.3, respectively. Although several Fano resonance and electro-optical modulators based on two- dimensional (2D) material, like graphene, black phosphorus, and transition metal dichalcogenides (TMDs) are previously reported, this paper designed a borophene-based metamaterial to achieve Fano resonance electro-optical modulator and sensor, because borophene possesses a series of excellent physical and chemical properties, for example, mechanical compliance, high carrier mobility, and optical transparency. Therefore, the proposed borophene-based metamaterial will be beneficial in the fields of high-performance plasmonic sensors, slow light, and electro-optical modulators in the near future.

Bethe M-layer construction on the Ising model

In statistical physics, one of the standard methods to study second order phase transitions is the renormalization group that usually leads to an expansion around the corresponding fully connected solution. Unfortunately, often in disordered models, some important finite dimensional second-order phase transitions are qualitatively different or absent in the corresponding fully connected model: in such cases the standard expansion fails. Recently, a new method, the M-layer one, has been introduced that performs an expansion around a different soluble mean field model: the Bethe lattice one. This new method has been already used to compute the upper critical dimension DU of different disordered systems such as the Random Field Ising model or the Spin glass model with field. If then one wants to go beyond and construct an expansion around DU to understand how critical quantities get renormalized, the actual computation of all the numerical factors is needed. This next step has still not been performed, being technically more involved. In this paper we perform this computation for the ferromagnetic Ising model without quenched disorder, in finite dimensions: we show that, at one-loop order inside the M-layer approach, we recover the continuum quartic field theory and we are able to identify the coupling constant g and the other parameters of the theory, as a function of macroscopic and microscopic details of the model such as the lattice spacing, the physical lattice dimension and the temperature. This is a fundamental step that will help in applying in the future the same techniques to more complicated systems, for which the standard field theoretical approach is impracticable.

Tracking the Dimensionality Transition from a Three Dimensional Single Crystal to a Two Dimensional Perovskite

AbstractThis work carefully studied the transition from 3D perovskite to 2D perovskite. Our system includes single crystals (SCs) of MAPbBr3, which were dipped in a solution of barrier molecules. Three monoammonium cations and one di‐ammonium cation were studied. Absorbance and cathodoluminescence were used to follow the formation of low‐dimensional perovskite on the SC surface. Quantitative nuclear magnetic resonance and scanning electron microscopy assist in quantitatively tracking the exchange process. We followed the barrier molecules′ concentration during the exchange process and their penetration depth into the 3D single crystal. The short aliphatic chain penetrates much farther into the crystal (ca. 450 μm) than the long aliphatic chain barrier molecule. In contrast, the process time is the opposite: the long aliphatic chain requires 5 days to achieve an equilibrium state compared with 15 days for the short aliphatic chain. Ab initio calculations indicate that the exchange process initiates due to the methylammonium vacancies on the surface, and the process is inhibited by the interactions between the −NH3 group and the PbBr2 planes. This work sheds light on the kinetics and thermodynamics of the transition from 3D to 2D perovskites, which is important for stabilizing the hybrid perovskites.

Inserting intermolecular hydrogen bonds to achieve dimensional regulation and phase transition temperature enhancement

Organic-inorganic hybrid materials have become potential candidates in fields of light emitting diodes (LEDs), mechanical switches, energy conversion due to their excellent magneto-opto-electronic properties. Further improving the performance of materials is a prerequisite for achieving their commercial application. Currently, many effective strategies have been proposed and validated to enhance the properties of materials, but both simultaneously realizing the improvement phase transition temperature and dimensional regulation of materials remains a huge challenge. Here, we successfully synthesized two hybrid materials, (pyrrolidinium)PbI3 (Com-1) and (3-hydroxypyrrolium)6Pb5I16 (Com-2). In this work, the strategy of inserting intermolecular hydrogen bonds cleverly achieves a significant increase in phase transition temperature (ΔT = 81 K) and dimensional regulation (1D to 2D). Moreover, semiconductor properties of two compounds are investigated to be direct bandgap semiconductor. In short, inserting intermolecular hydrogen bonds between molecules is an effective strategy to improve physical performance.

Ultimately Adaptive Fluid Interfacial Phospholipid Membranes Unveiled Unanticipated High Cellular Mechanical Work.

Living cells actively interact biochemically and mechanically with the surrounding extracellular matrices (ECMs) and undergo dramatic morphological and dimensional transitions, concomitantly remodeling ECMs. However, there is no suitable method to quantitatively discuss the contribution of mechanical interactions in such mutually adaptive processes. Herein, a highly deformable "living" cellular scaffold is developed to evaluate overall mechanical energy transfer between cell and ECMs. It is based on the water-perfluorocarbon interface decorated with phospholipids bearing a cell-adhesive ligand and fluorescent tag. The bioinert nature of the phospholipid membranes prevents the formation of solid-like protein nanofilms at the fluid interface, enabling to visualize and quantify cellular mechanical work against the ultimately adaptive model ECM. A new cellular wetting regime is identified, wherein interface deformation proceeds to cell flattening, followed by its eventual restoration. The cellular mechanical work during this adaptive wetting process is one order of magnitude higher than those reported withconventional elastic platforms. The behavior of viscous liquid drops at the air-water interface can simulate cellular adaptive wetting, suggesting that overall viscoelasticity of the cell body predominates the emergent wetting regime and regulates mechanical output. Cellular-force-driven high-energy states on the adaptive platform can be useful for cell fate manipulation.

Confinement-Induced Isosymmetric Metal-Insulator Transition in Ultrathin Epitaxial V2O3 Films.

Dimensional confinement has shown to be an effective strategy to tune competing degrees of freedom in complex oxides. Here, we achieved atomic layered growth of trigonal vanadium sesquioxide (V2O3) by means of oxygen-assisted molecular beam epitaxy. This led to a series of high-quality epitaxial ultrathin V2O3 films down to unit cell thickness, enabling the study of the intrinsic electron correlations upon confinement. By electrical and optical measurements, we demonstrate a dimensional confinement-induced metal-insulator transition in these ultrathin films. We shed light on the Mott-Hubbard nature of this transition, revealing a vanishing quasiparticle weight as demonstrated by photoemission spectroscopy. Furthermore, we prove that dimensional confinement acts as an effective out-of-plane stress. This highlights the structural component of correlated oxides in a confined architecture, while opening an avenue to control both in-plane and out-of-plane lattice components by epitaxial strain and confinement, respectively.

Order, chaos, and dimensionality transition in a system of swarmalators.

Similarly to sperm, where individuals self-organize in space while also striving for coherence in their tail swinging, several natural and engineered systems exhibit the emergence of swarming and synchronization. The arising and interplay of these phenomena have been captured by collectives of hypothetical particles named swarmalators, each possessing a position and a phase whose dynamics are affected reciprocally and also by the space-phase states of their neighbors. In this work, we introduce a solvable model of swarmalators able to move in two-dimensional spaces. We show that several static and active collective states can emerge and derive necessary conditions for each to show up as the model parameters are varied. These conditions elucidate, in some cases, the displaying of multistability among states. Notably, in the active regime, the system exhibits hyperchaos, maintaining spatial correlation under certain conditions and breaking it under others on what we interpret as a dimensionality transition.

Structural and optical properties of 1T-MoS2/MoO3 thin films prepared by spray pyrolysis method

Electrical properties of the devices based on two dimensional (2D) transition metal dichalcogenids thin films, is highly depended to their producing method and preparation conditions. In the present work structural and optical properties of MoS2/MoO3 nano-heterostructure films prepared by spray pyrolysis technique were studied. X-ray diffraction analysis revealed a phase transformation from hexagonal semiconducting 2H–MoS2 to octahedral metallic 1T-MoS2 phase by decreasing the molarity of ammonium molybdate as the precursor solution. The controllable phase transition provides a degree of freedom to pave the way for more novel devices. UV–Vis absorption spectra and photoluminescence (PL) spectroscopy confirm the presence of monolayer MoS2 with a direct band gap of ∼1.84 eV, related to a peak position at 674 nm in the composite. A change in the sample's band gap by annealing treatment on the hybrid films is, here reported. We found three different band gap of 1.7, 2.1 and 2.25 eV for the three composite samples and discussed the case. The highest PL quantum yield (QY) of the 1T-MoS2 based composite make it as a better candidate for photocatalysis applications. A brief discussion of the Raman spectra analysis from a prepared MoS2/MoO3 sample is also included. The present work illustrates the potential use of composite based heterostructures in electrical devises where higher conductivity of the metallic phase of MoS2 nanostructures is needed.

Evolutionary analysis of rainstorm momentum and non-stationary variating patterns in response to climatic changes across diverse terrains

This study aims to analyze time-series measurements encompassing rainstorm events with over a century of datasets to identify rainstorm evolution and dimensional transitions in non-stationarity. Rainstorm events are identified using partial duration series (PDS) to extract changes in rainstorm characteristics, namely maximum intensity (MAXI), duration (D), total rainfall (TR), and average rainfall intensity (ARI), in response to climate change. Ensemble empirical mode decomposition is used for trend filtering and non-stationary identification to explore spatiotemporal insight patterns. Trend models for the first–second-order moments of rainstorm characteristics are used to formulate the identified mean–variance trends using combined multi-dimensional linear-parabolic regression. Best-fitting combinations of various distributions (probability density functions) and trend models for multiple characteristic series are identified based on the Akaike information criterion. We analyze the dimensional transition in rainfall non-stationarity based on sensitivity analysis using PDS to determine its natural geophysical causes. The integrated methodology was applied to the data retrieved from nine weather stations in Taiwan. Our findings reveal rainstorm characteristics of “short D but high rainfall intensity” or “lower MAXI but high TR” across multiple stations. The parabolic trend of the first-order moment (i.e., mean) of ARI, D, and TR appears at the endpoint of the mountain ranges. Areas receiving monsoons and those on the windward plain show a rising parabolic trend in the first- and second-order moments (i.e., mean–variance) characterizing MAXI, implying that the occurrence frequency and magnitude of extreme MAXI increases. Non-stationary transitions in MAXI appear for mountain ranges exposed to the monsoon co-movement effect on both windward and leeward sides. Stations in the plains and rift valleys show upgraded and downgraded transitions in the non-stationary dimensions for D, respectively.

A detailed study of the electronic and optical properties of germanium nanotubes.

We employed first-principles calculations to investigate the electronic and optical properties of germanene nanotubes (GeNTs). Significant multi-orbital hybridizations lead to metallic and semiconducting behaviors in small-sized armchair and zigzag GeNTs, respectively. The changes in band gaps and subband dispersions with increasing diameter have been thoroughly understood by analyzing spatial charge densities and projected density of states. The optical absorption spectra exhibit diameter-dependent anisotropy and suggest a dimensional transition beyond a critical diameter. This comprehensive study not only deepens our understanding of GeNTs but also reveals new possibilities for various nanotechnology applications.

Dimensional Transitions in Turbulence: The Effects of Rotation and Stratification

The transition from two-dimensional to three-dimensional turbulence is a fascinating problem which finds applications in the study of geophysical flows. This paper briefly reviews the research in this field with emphasis on the role of rotation and stratification, two important ingredients of geophysical flows at large scales. By means of direct numerical simulations of the Navier–Stokes equations, the conditions for the emergence of a split cascade, with a simultaneous cascade of energy to both the large and the small scales, are discussed.

CO2 Electrochemical reduction on the two dimensional transition metal coordinated by 2,3,6,7,10,11-triphenylenehexathiol and 2,3,6,7,10,11-triphenylenehexamine, a computational survey

ABSTRACT Electrochemical CO2 reduction reaction (CO2RR) provides a feasible technology for alleviating global warming, energy crisis and sustainable energy production. In this work, CO2RR reaction mechanism on TM-THTA (TM = Fe, Co, Ni, Ru, Rh, Pd, THTA is composed by two types of building blocks of 2,3,6,7,10,11-triphenylenehexathiol and 2,3,6,7,10,11-triphenylenehexamine) has been studied by using density functional method. Our study showed that the studied catalysts are stable both thermodynamically and electrochemically. Rh-THTA is a good CO2 reduction catalyst in producing CH4. Pd-THTA is a potential CO2 reduction catalyst in producing HCOOH. Solvent effect plays important role in reaction mechanism. The strong hydrogen evolution reaction in Rh-THTA and Pd-THTA can be refrained by adjusting the pH values of electrolyte. We hope this study could provide a useful way to develop 2D-MOF-based CO2RR electrocatalysts.

Fabrication of NiSe2 decorated graphene oxide nanocomposite modified electrode as a high performance electrochemical sensor for carbamazepine

AbstractRecently, semiconductor nanomaterials have gained interest amongst researchers because of their good electrocatalytic properties. Two dimensional (2D) transition metal dichalcogenide materials, NiSe2 have good physical, chemical, and transport properties for sensing applications. The present work demonstrates the fabrication of NiSe2‐graphene oxide (NiSe2−GO) modified glassy carbon electrode for the determination of carbamazepine (CBZ). The prepared nanocomposite was characterized by XRD, SEM and FT‐IR spectral methods. CBZ exhibited an irreversible oxidation peak at 0.85 V on NiSe2−GO/GCE in phosphate buffer of pH 7.0. A 54‐fold enhancement in oxidation peak current was observed at NiSe2−GO/GCE when compared to that at bare GCE. Sensing performance of NiSe2−GO/GCE was optimized by varying peak current dependent parameters. Linear relationship between the peak current and concentration of CBZ was observed in the range of 4.50×10−8–3.22×10−5 mol L−1 for differential pulse voltammetric method and 2.32×10−8–4.79×10−5 mol L−1 for square wave voltammetric method. The practical utility of the proposed sensor, was demonstrated by determining CBZ in pharmaceutical formulations and spiked urine samples.

Ferroelectric Size Effects on Statics and Dynamics of Domain Wall.

Domain walls separating differently oriented polarization regions of ferroelectric materials are known to greatly impact nanoscale materials and device functionalities. Though the understanding of size effects in ferroelectric nanostructures has progressed, the effect of thickness downsizing on domain wall scaling behavior has remained unexplored. Using piezoresponse force microscopy, epitaxial BaTiO3 film thickness size (2-90nm) effects on the critical scaling universality of the domain wall dynamical creep and static roughness exponents including dimensionality is demonstrated. Independently estimated static roughness exponents ranging between 0.34 and 0.28 and dynamical creep exponents transition from 0.54 to 0.22 elucidate the domain wall dimensionality transition from two- to quasi-one-dimension in the thickness range of 10-25nm, which is later validated by evaluating effective dimensionality within the paradigm of random-bond universality. The observed interdimensional transition is further credenced to the compressive strain and long-range strain-dipolar interactions, as revealed by the structural analyses and additional measurements with modified substrate-induced strain. These results provide new insights into the understanding of size effects in nanoscale ferroelectricity, paving the way toward future nanodevices.

Origin of the quantum shape effect.

The quantum size and shape effects are often considered difficult to distinguish from each other because of their coexistence. Essentially, it is possible to separate them and focus solely on the shape effect by considering a size-invariant shape transformation, which changes the discrete energy spectra of strongly confined systems and causes the quantum shape effects. The size-invariant shape transformation is a geometric technique of transforming shapes by preserving the boundary curvature, topology, and the Lebesgue measure of a bounded domain. The quantum shape effect is a quite different phenomenon from quantum size effects, as it can have the opposite influence on the physical properties of nanoscale systems. While quantum size effects can usually be obtained via bounded continuum approximation, the quantum shape effect is a direct consequence of the energy quantization in specifically designed confined geometries. Here, we explore the origin of the quantum shape effect by theoretically investigating the simplest system that can produce the same physics: quantum particles in a one-dimensional box separated by a moving partition. The partition moves quasistatically from one end of the box to the other, allowing the system to remain in equilibrium with a reservoir throughout the process. The partition and the boundaries are impenetrable by particles, forming two effectively interconnected regions. The position of the partition becomes the shape variable. We investigate the quantum shape effect on the thermodynamic properties of confined particles considering their discrete spectrum. In addition, we applied an analytical model based on dimensional transitions to predict thermodynamic properties under the quantum shape effect accurately. A fundamental understanding of quantum shape effects could pave the way for employing them to engineer physical properties and design better materials at the nanoscale.

Exfoliation behavior and superior photothermal conversion performance of MXenes beyond Ti3C2Tx

Two dimensional transition metal carbides (MXenes) have attracted significant interest due to their unique layer structure, chemical diversity and superior physiochemical performances. However, most studies have focused on Ti3C2Tx, and the synthesis process and photothermal conversion capability of other MXenes remain unclear. In this work, we have systematically investigated the exfoliation behavior of six different MXenes, including mono-transition-metal (Ti3C2Tx, V2CTx, and Nb2CTx) and double-transition-metal (TiVCTx, TiNbCTx, and NbVCTx) MXenes derived from MAX phases, integrated with their photothermal conversion performance by combining experimental and theoretical studies. The phase, morphology, composition and surface groups of the different MXenes have been analyzed using XRD, SEM, XPS, and HRTEM techniques. Our results indicate a systematic variation in etching difficulty from difficult to easy, as Nb2AlC > NbVAlC > V2AlC > TiNbAlC > TiVAlC > Ti3AlC2, which correlates with the chemical composition and etching duration. Furthermore, the exfoliation factor m from density functional theory calculations reveals that the bond energies of M−A bonds are much weaker than M−X bonds in MAX phases, which agrees well with the experimental results. Interestingly that, all the obtained MXenes exhibit remarkable photothermal conversion performance with fast response, where the MXenes beyond Ti3C2Tx, such as V2CTx, NbVCTx, Nb2CTx, TiVCTx, and TiNbCTx, display higher saturation temperature of 95, 88, 81, 78, and 71 °C, respectively, than that of Ti3C2Tx (65 °C). These findings could potentially facilitate the efficient design and development of diverse MXene materials with outstanding photothermal conversion performance for applications in wearable devices, biomedical technology and solar water desalination.

Hierarchical Porous N‐doped Carbon Encapsulated Fluorine‐free MXene with Tunable Coordination Chemistry by One‐pot Etching Strategy for Lithium–Sulfur Batteries

AbstractContinuous and considerable exploration of two–dimensional transition metal carbides and nitrides (MXenes)toward interlayer spacing expansion, surface termination modification and composition architecture construction has aroused significant interest in energy storage fields. Nevertheless, their employment remains severely impeded by a fundamental lack of comprehension of the coordination chemistry of MXenes. Herein, hierarchical porous N‐doped carbon encapsulated fluorine‐free Ti3C2Tx with tunable coordination chemistry is fabricated by a novel one‐pot etching strategy. The Ti coordinated with N manipulated by phase reconstruction is identified by high‐angle annular dark‐field scanning transmission electron microscopy and X‐ray photoelectron spectroscopy. Moreover, hierarchical porous nitrogen‐doped carbons (HPNC) are distinctly observed that result in a multifold increase in material surface area derived from a substantial increment of micro‐ and mesoporosity. The structural synergistic effect of Ti coordinated with N, and HPNC heighten binding energy and reduce energy barriers that accelerate redox kinetics, and boosts physical immobilization of lithium polysulfides. The aforementioned MXenes modified separators endow lithium–sulfur batteries with a reversible capacity of 889.5 mA h g−1 with capacity retention of 79.5% after 100 cycles at 0.5 A g−1. Overall, this work affords a novel and universal etching strategy in terms of directly synthesizing fluoride‐free MXene with tunable coordination chemistry toward exploring the correlation between structural and electrochemical properties.

Designed two dimensional transition metal borides (TM2B12): Robust ferromagnetic half metal and antiferromagnetic semiconductor

Two dimensional transition metal borides have been attracting broad interest due to its rich electronic and magnetic properties. Here, using first-principles calculations, we predict two transition metal boride monolayers, Cr2B12 and Mn2B12, composed of B12 icosahedra and transition metal atoms. It is found that both structures are thermodynamically stable with large cohesive energies and small formation energies. The Cr2B12 monolayer is a ferromagnetic (FM) quasi-half metal, and the Mn2B12 monolayer is an antiferromagnetic (AFM) semiconductor with a bandgap of 0.41 eV. The critical temperature is found to be 145 and 135 K for the Cr2B12 monolayer and the Mn2B12 monolayer, respectively. Moreover, the electronic and magnetic properties of both systems can be tuned by applying external strains. Upon applying biaxial tensile/compressive strain, the (half metallic) bandgap of both systems increases/decreases, and a quasi-half metal to half metal transition is found for the Cr2B12 monolayer under 5% tensile and 4% compressive strain. Furthermore, the critical temperatures of both systems are found to increase with compressive strain and decrease with tensile strain, which reaches 165 and 510 K for the Cr2B12 monolayer and the Mn2B12 monolayer under 5% compressive strain, respectively. The results provide a strategy for designing 2D transition metal borides with potential applications in electronic and spintronic devices.