Nanoscale Size Effects Research Articles

Two-Dimensional Ferroelectric Materials: Synthesis, Characterization and Applications

In recent years, the continuous advancements in microelectronics have driven the evolution of electronic devices towards miniaturization and integration. However, at the nanoscale level, surface and size effects become significant, imposing constraints on the use of conventional bulk ferroelectric materials in contemporary industry. As a result, in the field of materials research, two-dimensional (2D) ferroelectric materials with stable spontaneous polarization and minimal size effects have gained significant attention. These novel 2D ferroelectric materials have great potential for future nano-level ferroelectric applications, enabling high levels of device integration. To begin with, this paper divides 2D ferroelectric materials into two categories: intrinsic ferroelectrics and sliding ferroelectrics. It also discusses the features and current state of research on each of these categories. Next, typical 2D ferroelectric material preparation and characterization techniques are outlined. Additionally, 2D ferroelectric memory devices like ferroelectric diodes (FD), ferroelectric field effect transistors (FeFET), ferroelectric semiconductor field-effect transistors (FeSFET), and ferroelectric tunnel junctions (FTJ) are introduced. Finally, this review also presents expectations and potential challenges in the domain of 2D ferroelectric materials.

Harvesting nucleating structures in nanoparticle crystallization: The example of gold, silver, and iron.

The thermodynamics and kinetics of nanoparticle crystallization, as opposed to bulk phases, may be influenced by surface and size effects. We investigate the importance of such factors in the crystallization process of gold, silver, and iron nanodroplets using numerical simulations in the form of molecular dynamics combined with path sampling. This modeling strategy is targeted at obtaining representative ensembles of structures located at the transition state of the crystallization process. A structural analysis of the transition state ensembles reveals that both the average size and location of the critical nucleation cluster are influenced by surface and nanoscale size effects. Furthermore, we also show that transition state structures in smaller nanodroplets exhibit a more ordered liquid phase, and differentiating between a well-ordered critical cluster and its surrounding disordered liquid phase becomes less evident. All in all, these findings demonstrate that crystallization mechanisms in nanoparticles go beyond the assumptions of classical nucleation theory.

Bioactive chitosan/polydopamine nanospheres coating on carbon fiber towards strengthening epoxy composites

This paper initially examines the feasibility and effectiveness on interfacial adhesion of composites when grafting nanoparticle-structured polydopamine (PDA) and chitosan around carbon fiber periphery. The resulting interfacial shear strength was maximized as 92.3 MPa, delivering 50.1 % and 15.7–16.2 % gains over those of control fiber and only polydopamine nanospheres (PDANPs) or only chitosan modified fiber composites. Measuring surface morphology and thermal stability of fibers found that abundant PDANPs well adhered with the help of chitosan, highlighting nanoscale size effects and intrinsic adhesiveness of PDA. Under good wettability, rich and dense interfacial interactions (covalent and hydrogen bond, electrostatic interaction, and π conjugation) caused by PDANPs/chitosan coating provides impetus for effective stress transfer. Additionally, the stable “soft-rigid” combination of chitosan and PDANPs adds the efficiency of crack passivation. As such, it is hoped that this work could fully explore the possibility of PDA geometry in interphase engineering of fiber composites.

Revealing the percolation–agglomeration transition in polymer nanocomposites via MD-informed continuum RVEs with elastoplastic interphases

This contribution builds the concluding step of a multiscale approach to effectively capture the mechanical behavior of polymer nanocomposites (PNCs), in this case, silica-modified polystyrene. By introducing continuum-based representative volume elements (RVEs) that employ previously identified elastoplastic property gradients for the interphases surrounding the fillers, the effects of particle size, particle volume fraction, and agglomeration on the mechanical performance are investigated. Uniaxial tension tests are simulated with the respective finite-element RVEs, and stress–strain curves are derived. The elastic and plastic material properties of the RVE can then be extracted and analyzed quantitatively by fitting the stress–strain curves with a Voce-type elastoplasticity formulation.At small degrees of agglomeration, i.e., good particle dispersion, in combination with sufficiently large particle volume fraction, percolation bands form, leading to improved elastic and plastic properties. Higher degrees of agglomeration or particle clusters behave like large single particles, which has an adverse effect, i.e., the nanoscale size effect is thereby neutralized. Therefore, the precise MD-informed elastoplastic interphase representation of our RVEs enables the investigation of the transition from beneficial percolation to unfavorable agglomeration. Ultimately, this contribution establishes a link between the effects of particle size, particle volume fraction, agglomeration, and percolation, which have so far only been discussed separately in the literature.Our methodology offers new insights into the structure–property relations of PNCs and their resulting mechanical behavior. The underlying multiscale approach with a systematic transition from molecular to microscopic scales is required to complement experimental observations and exploit the full potential of PNCs.

Nanoconfinement of ultra-small Bi2Te3 nanocrystals on reduced graphene oxide: a pathway to high-performance sodium-ion battery anodes.

Bismuth telluride (Bi2Te3) nanomaterials have attracted considerable attention owing to their intriguing physicochemical properties and wide-ranging potential applications arising from their distinctive layered structure and nanoscale size effects. However, synthesizing sub-100 nm ultra-small Bi2Te3 nanocrystals remains a formidable challenge. To date, there has been little investigation on the performance of these ultra-small Bi2Te3 nanocrystals in sodium-ion batteries (SIBs). This study presents a general strategy for synthesizing ultra-small Bi2Te3 nanocrystals on reduced graphene oxide (Bi2Te3/rGO) through a nanoconfinement approach. First-principles calculations and electrochemical kinetic studies confirm that the ultra-small Bi2Te3/rGO composite material can effectively mitigate volumetric expansion, preserve electrode integrity, and enhance electron transfer, Na-ion adsorption, and diffusion capacity. As a result, the Bi2Te3/rGO electrode demonstrates a remarkable initial specific capacity of 521 mA h g-1 at 0.1 A g-1, showcasing outstanding rate behaviour and long-lasting cycle life exceeding 800 cycles at 1 A g-1 while preserving exceptional rate properties. The function of the battery is indicated by ex situ TEM and XPS findings, which propose a conventional dual mechanism involving conversion and alloying. This work paves the way for rapid advancements in Bi2Te3-based SIB anodes while contributing to our understanding of sodium ion storage mechanisms.

Understanding How the Suppression of Insertion-Induced Phase Transitions Leads to Fast Charging in Nanoscale LixMoO2.

Fast-charging Li-ion batteries are technologically important for the electrification of transportation and the implementation of grid-scale storage, and additional fundamental understanding of high-rate insertion reactions is necessary to overcome current rate limitations. In particular, phase transformations during ion insertion have been hypothesized to slow charging. Nanoscale materials with modified transformation behavior often show much faster kinetics, but the mechanism for these changes and their specific contribution to fast-charging remain poorly understood. In this work, we combine operando synchrotron X-ray diffraction with electrochemical kinetics analyses to illustrate how nanoscale crystal size leads to suppression of first-order insertion-induced phase transitions and their negative kinetic effects in MoO2, a tunnel structure host material. In electrodes made with micrometer-scale particles, large first-order phase transitions during cycling lower capacity, slow charge storage, and decrease cycle life. In medium-sized nanoporous MoO2, the phase transitions remain first-order, but show a considerably smaller miscibility gap and shorter two-phase coexistence region. Finally, in small MoO2 nanocrystals, the structural evolution during lithiation becomes entirely single-phase/solid-solution. For all nanostructured materials, the changes to the phase transition dynamics lead to dramatic improvements in capacity, rate capability, and cycle life. This work highlights the continuous evolution from a kinetically hindered battery material in bulk form to a fast-charging, pseudocapacitive material through nanoscale size effects. As such, it provides key insight into how phase transitions can be effectively controlled using nanoscale size and emphasizes the importance of these structural dynamics to the fast rate capability observed in nanostructured electrode materials.

Investigation of guided wave propagation in nanoscale layered periodic piezoelectric plates based on Eringen's nonlocal and strain gradient theory

This paper investigates the dynamic propagation behavior of guided waves in nanoscale media composed of alternating layers of piezoelectric phases. The study employs Eringen's nonlocal and strain gradient theories to derive equations for symmetric wave propagation and the scattering relations of guided waves perpendicular to these structures. Dispersion curves are calculated and plotted to compare these theories, considering the influence of nanoscale size-effect, volume ratio of constituent layers, and material length scale. Using the strain gradient theory, the paper explores the impact of length scale parameters on the propagation behavior of horizontally polarized guided waves in an alternating layer structure of nanoscale piezoelectric material, specifically nanoscale piezoelectric laminates. The analysis involves calculating localization factors and dispersion curves to analyze the effects of size-effect and length scale parameters on wave propagation and band structures. Additionally, the study plots and analyzes changes in mechanical displacement and electrical potential, followed by an investigation and discussion of nanoscale size effects and the effects of the material's length scale parameter on dispersion curves and conversion modes within specific regions. The results highlight that the length scale effect parameter significantly impacts the mode conversion zones and band gap structures, more so than the NLPE continuum theory suggests. As the strain gradient parameter increases, these zones shift towards higher wavenumbers and to the right . Furthermore, introducing the length scale factor results in a substantial decrease in both the formation of conversion zones and the density of dispersion curves.

A Concise Review on Magnetic Nanoparticles: Their Properties, Types, Synthetic Methods, and Current Trending Applications

Abstract: In recent years, there has been significant research on developing magnetic nanoparticles (MNPs) with multifunctional characteristics. This review focuses on the properties and various types of MNPs, methods of their synthesis, and biomedical, clinical, and other applications. These syntheses of MNPs were achieved by various methods, like precipitation, thermal, pyrolysis, vapor deposition, and sonochemical. MNPs are nano-sized materials with diameters ranging from 1 to 100 nm. The MNPs have been used for various applications in biomedical, cancer theranostic, imaging, drug delivery, biosensing, environment, and agriculture. MNPs have been extensively researched for molecular diagnosis, treatment, and therapeutic outcome monitoring in a range of illnesses. They are perfect for biological applications, including cancer therapy, thrombolysis, and molecular imaging, because of their nanoscale size, surface area, and absence of side effects. In particular, MNPs can be used to conjugate chemotherapeutic medicines (or) target ligands/proteins, making them beneficial for drug delivery. However, up until that time, some ongoing issues and developments in MNPs include toxicity and biocompatibility, targeting accuracy, regulation and safety, clinical translation, hyperthermia therapy, immunomodulatory effects, multifunctionality, and nanoparticle aggregation.

Nanoscale Size Effects on Push-Pull Fe-O Hybridization through the Multiferroic Transition of Perovskite ϵ-Fe2O3.

Multiferroics have tremendous potential to revolutionize logic and memory devices through new functionalities and energy efficiencies. To reach their optimal capabilities will require better understanding and enhancement of the ferroic orders and couplings. Herein, we use ϵ-Fe2O3 as a model system with a simplifying single magnetic ion. Using 15, 20, and 30 nm nanoparticles, we identify that a modified and size-dependent Fe-O hybridization changes the spin-orbit coupling and strengthens it via longer octahedra chains. Fe-O hybridization is modified through the incommensurate phase, with a unique two-step rearrangement of the electronic environment through this transition with attraction and then repulsion of electrons around tetrahedral Fe. Interestingly, size effects disappear in the high-temperature phase where the strongest Fe-O hybridization occurs. By manipulating this hybridization, we tune and control the multiferroic properties.

Colloidal Ternary Telluride Quantum Dots for Tunable Phase Change Optics in the Visible and Near-Infrared.

A structural change between amorphous and crystalline phase provides a basis for reliable and modular photonic and electronic devices, such as nonvolatile memory, beam steerers, solid-state reflective displays, or mid-IR antennas. In this paper, we leverage the benefits of liquid-based synthesis to access phase-change memory tellurides in the form of colloidally stable quantum dots. We report a library of ternary MxGe1-xTe colloids (where M is Sn, Bi, Pb, In, Co, Ag) and then showcase the phase, composition, and size tunability for Sn-Ge-Te quantum dots. Full chemical control of Sn-Ge-Te quantum dots permits a systematic study of structural and optical properties of this phase-change nanomaterial. Specifically, we report composition-dependent crystallization temperature for Sn-Ge-Te quantum dots, which is notably higher compared to bulk thin films. This gives the synergistic benefit of tailoring dopant and material dimension to combine the superior aging properties and ultrafast crystallization kinetics of bulk Sn-Ge-Te, while improving memory data retention due to nanoscale size effects. Furthermore, we discover a large reflectivity contrast between amorphous and crystalline Sn-Ge-Te thin films, exceeding 0.7 in the near-IR spectrum region. We utilize these excellent phase-change optical properties of Sn-Ge-Te quantum dots along with liquid-based processability for nonvolatile multicolor images and electro-optical phase-change devices. Our colloidal approach for phase-change applications offers higher customizability of materials, simpler fabrication, and further miniaturization to the sub-10 nm phase-change devices.

Electronic materials with nanoscale curved geometries

As the dimensions of a material shrink from an extended bulk solid to a nanoscale structure, size and quantum confinement effects become dominant, altering the properties of the material. Materials with nanoscale curved geometries, such as rolled-up nanomembranes and zigzag-shaped nanowires, have recently been found to exhibit a number of intriguing electronic and magnetic properties due to shape-driven modifications of charge motion or confinement effects. Local strain generated by curvature can also lead to changes in material properties due to electromechanical coupling. Here we review the development of electronic materials with nanoscale curved geometries. We examine the origin of shape-, confinement- and strain-induced effects and explore how to exploit these in electronic, spintronic and superconducting devices. We also consider the methods required to synthesize and characterize curvilinear nanostructures, and highlight key areas for the future development of curved electronics.

Influences of defects on the propagation of transverse waves in periodic piezoelectric laminate structure with nanoscaled layers

By the stiffness matrix method based on the nonlocal elastic continuum theory, the transmission spectra of the transverse elastic waves propagating normally in nanoscaled periodic piezoelectric laminates with defects are investigated in detail in this paper. Defect is introduced by replacing a constituent layer or inserting another layer in a unit-cell. The thicknesses of all sub-layers and defect layer are at the nanoscale. Simultaneously, complex band structures and localization factors are calculated and employed to verify the band structures described by the transmission spectra. The influences of the defect type, the defect material, the volume fraction of the defect layer in the unit-cell, the piezoelectric constants of the defect layer, and the nanoscale size-effect on the transmission spectra are analyzed and discussed in detail. The present study provides a theoretical guide for the design and applications of the nanoscaled acoustic filters or transducers with defects.

Triplet energy transfer between inorganic nanocrystals and organic molecules

Merging the light- harvesting and emitting capability of inorganic materials with the versatile excited-state properties of organic molecules leveraging triplet energy transfer (TET) has recently become an important design strategy for light-driven applications ranging from energy conversion, biomedicine, to photoredox catalysis, and understanding the rules that govern such phenomena is essential. Recent years have witnessed some breakthroughs of TET as well as significant advances for regulating this photochemical process, but it still needs more integrated research at the center. In particular, efficient TET between semiconductor nanocrystals (or quantum dots) and organic molecules, which combines nanoscale size effect of the former and molecular versatility of the latter, has been demonstrated as a promising enabler for breaking the Shockley-Queisser limit in solar energy conversion, controlling photon emission, and driving photochemical reactions in the years to come. Here we review the fundamentals of TET mechanism and some of its emerging applications, with special focus on recent progress towards the understanding and application of TET in nanocrystal-molecule hybrids and highlight some challenges for the field. Work is currently aimed at providing insights in controlling TET dynamics with a view to making the process as efficient as possible according to expected designs.

Forming‐Free Resistive Switching of Electrochemical Titanium Oxide Localized Nanostructures: Anodization, Chemical Composition, Nanoscale Size Effects, and Memristive Storage

AbstractElectrochemical anodization is a powerful method for the preparation of oxide thin films with controlled thickness, structure, and composition and proves as a promising approach to be applied to memristive devices. Here, experimental studies on titanium oxide nanoscale structures produced by local anodic oxidation and the influence of the thickness on the memristive properties are presented. Controllable preparation of forming‐free memristive cells with switching voltages less than 3 V are demonstrated. The chemical composition and oxidation state of the elements in the TiOxnanostructures are analyzed by means of X‐ray photoelectron spectroscopy, which reveals the formation of TiO2(458.4 eV), Ti2O3(456.6 eV), and TiO (454.8 eV). The increasing thickness of the devices from 4.5 ± 0.7 to 7.9 ± 0.3 nm leads to a decrease in the OFF to ON resistance ratio from 250 to 10.7, respectively. The mechanism of formation and resistive switching in the anodic devices is also discussed. The results can be applied to the design and development of technological processes for memristive structure manufacturing based on electrochemical oxidation.

Mercury goes Solid at room temperature at nanoscale and a potential Hg waste storage

While room temperature bulk mercury is liquid, it is solid in its nano-configuration (Ønano-Hg ≤ 2.5 nm). Conjugating the nano-scale size effect and the Laplace driven surface excess pressure, Hg nanoparticles of Ønano-Hg ≤ 2.4 nm embedded in a 2-D turbostratic Boron Nitride (BN) host matrix exhibited a net crystallization at room temperature via the experimentally observed (101) and (003) diffraction Bragg peaks of the solid Hg rhombohedral α-phase. The observed crystallization is correlated to a surface atomic ordering of 7 to 8 reticular atomic plans of the rhombohedral α-phase. Such a novelty of size effect on phase transition phenomena in Hg is conjugated to a potential Hg waste storage technology. Considering the vapor pressure of bulk Hg, Room Temperature (RT) Solid nano-Hg confinement could represent a potential green approach of Hg waste storage derived from modern halogen efficient light technology.

Nonlocal and magneto effects on dispersion characteristics of Love-type waves in piezomagnetic media

Attributions of intrinsic nanoscale dimension in piezomagnetic structures, the small scale effects on the propagating wave are undeniable in their piezotronic applications. In this work, based on the nonlocal constitutive relations, the nanoscale size effects on the Love-type wave propagating in piezomagnetic structure are investigated. Dispersion equations are derived for magnetically open and short circuit cases. Particular results are deduced and validated with the existing results. Variation of phase velocity and group velocity versus the penetration depth has been distinctly marked. Influence of various parameters like nonlocal parameter, magneto parameters, magnetomechanical coupling coefficient associated with piezomagnetic media etc. on the dispersion characteristics for first three modes has been demonstrated graphically. This research shows that small scale effects have substantial effect on the phase velocity of the propagating wave. The results find its enormous possible applications in smart devices especially, nanoscale devices using wave propagation phenomena owing to representing outstanding magnetic and mechanical coupling performances.

Advanced bioactive nanomaterials for biomedical applications.

Bioactive materials are a kind of materials with unique bioactivities, which can change the cellular behaviors and elicit biological responses from living tissues. Bioactive materials came into the spotlight in the late 1960s when the researchers found that the materials such as bioglass could react with surrounding bone tissue for bone regeneration. In the following decades, advances in nanotechnology brought the new development opportunities to bioactive nanomaterials. Bioactive nanomaterials are not a simple miniaturization of macroscopic materials. They exhibit unique bioactivities due to their nanoscale size effect, high specific surface area, and precise nanostructure, which can significantly influence the interactions with biological systems. Nowadays, bioactive nanomaterials have represented an important and exciting area of research. Current and future applications ensure that bioactive nanomaterials have a high academic and clinical importance. This review summaries the recent advances in the field of bioactive nanomaterials, and evaluate the influence factors of bioactivities. Then, a range of bioactive nanomaterials and their potential biomedical applications are discussed. Furthermore, the limitations, challenges, and future opportunities of bioactive nanomaterials are also discussed.

Vertical strain tuning and perpendicular magnetic anisotropy in La0.5Ca0.5MnO3 vertically aligned nanostructured thin films by the application of high magnetic fields

Epitaxial La0.5Ca0.5MnO3 (LCMO) thin films with vertically aligned nanostructures (VANs) have been achieved with the application of high magnetic fields in pulsed laser deposition processing. More interestingly, the microstructures, vertical strain, and perpendicular magnetic anisotropy (PMA) in the LCMO VAN films can be systematically manipulated by changing the applied high magnetic field strength. With increasing the high magnetic field, an increase in growth rate and a decrease in nanocolumn dimension are observed in the LCMO VAN films, which can be attributed to the enhanced suppression effect on adatom mobility and surface diffusion. Different from the LCMO planar-structured films, the intrinsic stress behaviors associated with vertical interfaces and grain boundaries instead of substrate strain in the LCMO VAN films are dominant in vertical strain evolution, indicating an out-of-plane compressive state, which is highly correlated with the growth rate and nanocolumn dimension. A core-shell model based on phase separation is proposed to understand the nanoscale size effect on magnetic properties in the LCMO VAN films. A tunable and enhanced PMA effect in the LCMO VAN films is also demonstrated. The results suggest that the application of a high magnetic field in pulsed laser deposition processing is a practicable route to achieve tunable VANs, and manipulate physical properties in manganite films.

Size-Dependent Alloying Ability of Immiscible W-Cu Bimetallic Nanoparticles: A Theoretical and Experimental Study.

The preparation of alloyed bimetallic nanoparticles (BNPs) between immiscible elements is always a huge challenge due to the lack of thermodynamic driving forces. W–Cu is a typical immiscible binary system, and it is difficult to alloy them under conventional circumstances. Here, we used the bond energy model (BEM) to calculate the effect of size on the alloying ability of W–Cu systems. The prediction results show that reducing the synthesis size (the original size of W and Cu) to less than 10 nm can obtain alloyed W–Cu BNPs. Moreover, we prepared alloyed W50Cu50 BNPs with a face-centered-cubic (FCC) crystalline structure via the nano in situ composite method. Energy-dispersive X-ray spectroscopy (EDS) coupled with scan transmission electron microscopy (STEM) confirmed that W and Cu are well mixed in a single-phase particle, instead of a phase segregation into a core-shell or other heterostructures. The present results suggest that the nanoscale size effect can overcome the immiscibility in immiscible binary systems. In the meantime, this work provided a high-yield and universal method for preparing alloyed BNPs between immiscible elements.

Buckling Analysis of CNTRC Curved Sandwich Nanobeams in Thermal Environment

This paper presents a mathematical continuum model to investigate the static stability buckling of cross-ply single-walled (SW) carbon nanotube reinforced composite (CNTRC) curved sandwich nanobeams in thermal environment, based on a novel quasi-3D higher-order shear deformation theory. The study considers possible nano-scale size effects in agreement with a nonlocal strain gradient theory, including a higher-order nonlocal parameter (material scale) and gradient length scale (size scale), to account for size-dependent properties. Several types of reinforcement material distributions are assumed, namely a uniform distribution (UD) as well as X- and O- functionally graded (FG) distributions. The material properties are also assumed to be temperature-dependent in agreement with the Touloukian principle. The problem is solved in closed form by applying the Galerkin method, where a numerical study is performed systematically to validate the proposed model, and check for the effects of several factors on the buckling response of CNTRC curved sandwich nanobeams, including the reinforcement material distributions, boundary conditions, length scale and nonlocal parameters, together with some geometry properties, such as the opening angle and slenderness ratio. The proposed model is verified to be an effective theoretical tool to treat the thermal buckling response of curved CNTRC sandwich nanobeams, ranging from macroscale to nanoscale, whose examples could be of great interest for the design of many nanostructural components in different engineering applications.