Spectroscopic Identification of Charge Transfer of Thiolated Molecules on Gold Nanoparticles via Gold Nanoclusters.

Investigation of charge transfer needs analytical tools that could reveal this phenomenon, and enables understanding of its effect at the molecular level. Here, we show how the combination of using gold nanoclusters (AuNCs) and different spectroscopic techniques could be employed to investigate the charge transfer of thiolated molecules on gold nanoparticles (AuNP@Mol). It was found that the charge transfer effect in the thiolated molecule could be affected by AuNCs, evidenced by the amplification of surface-enhanced Raman scattering (SERS) signal of the molecule and changes in fluorescence lifetime of AuNCs. Density functional theory (DFT) calculations further revealed that AuNCs could amplify the charge transfer process at the molecular level by pumping electrons to the surface of AuNPs. Finite element method (FEM) simulations also showed that the electromagnetic enhancement mechanism along with chemical enhancement determines the SERS improvement in the thiolated molecule. This study provides a mechanistic insight into the investigation of charge transfer at the molecular level between organic and inorganic compounds, which is of great importance in designing new nanocomposite systems. Additionally, this work demonstrates the potential of SERS as a powerful analytical tool that could be used in nanochemistry, material science, energy, and biomedical fields.

Magnetic skyrmions and their manipulations in a 2D multiferroic CuCrP2Te6 monolayer.

Magnetic skyrmions and their effective manipulations are promising for the design of next-generation information storage and processing devices, due to their topologically protected chiral spin textures and low energy cost. They, therefore, have attracted significant interest from the communities of condensed matter physics and materials science. Herein, based on density functional theory (DFT) calculations and micromagnetic simulations, we report the spontaneous 2 nm-diameter magnetic skyrmions in the monolayer CuCrP2Te6 originating from the synergistic effect of broken inversion symmetry and strong Dzyaloshinskii-Moriya interactions (DMIs). The creation and annihilation of magnetic skyrmions can be achieved via the ferroelectric to anti-ferroelectric (FE-to-AFE) transition, due to the variation of the magnetic parameter D2/|KJ|. Moreover, we also found that the DMIs and Heisenberg isotropic exchange can be manipulated by bi-axial strain, to effectively enhance skyrmion stability. Our findings provide feasible approaches to manipulate the skyrmions, which can be used for the design of next-generation information storage devices.

Medial Scapular Body (MSB) Goutallier Classification - MRI based reliability and validity of evaluation of the Goutallier classification for grading fatty infiltration of the rotator cuff.

INTRODUCTION: The degree of atrophy and fatty infiltration of rotator cuff muscle belly is a key predictor for cuff repairability. Traditionally, Goutallier grading of fatty infiltration is assessed at sagittal scapular Y-view. Massive rotator cuff tears are associated with tendon retraction and medial retraction of cuff musculature, resulting in medialization of the muscle bulk. Thus, standard Y-view can misrepresent the region of interest and may misguide clinicians when assessing repairability. It is hypothesized that by assessing the muscle belly with multiple medial sagittal MRI sections at medial scapular body, the Medial Scapular Body - Goutallier Classification (MSB-GC) will improve reliability and repeatability giving a more representative approximation to the degree of fatty infiltration, as compared with original Y-view. METHODS: Fatty infiltration of the rotator cuff muscles were classified based on the Goutallier grade (0 to 4) at three defined sections section 1: original Y-view; section 2: level of suprascapular notch; section 3: three cm medial to suprascapular notch on MRI scans. Six sub-specialist fellowship trained shoulder surgeons, and three musculoskeletal radiologists independently evaluated deidentified MRI scans of included patients. RESULTS: Out of 80 scans, 78% (n=62) were massive cuff tears involving supraspinatus, infraspinatus and subscapularis tendon. Inter-observer reliability (consistency between observers) for Goutallier grade was excellent for all three predefined sections (range:0.87-0.95). Intra-observer reliability (repeatability) for Goutallier grade was excellent for all three sections and four rotator cuff muscles (range:0.83-0.97). There was a moderate to strong positive correlation of Goutallier grades between sections 1 and 3 and between sections 2 and 3 and these were statistically significant (p<0.001). There was a reduction in the severity of fatty infiltration on the Goutallier classification from sections 1 to 3 across all muscles. 42.5% of both supraspinatus and infraspinatus were downgraded by one, 20% of supraspinatus and 3.8% of infraspinatus were downgraded by 2 and 2.5% of supraspinatus were downgraded by 3. CONCLUSION: This study found that applying the Goutallier classification to more medial MRI sections (MSB-GC) resulted in assignment of lower grades for all rotator cuff muscles. Additionally, this method demonstrated excellent test-retest reliability and repeatability. Inclusion of a more medial view or whole scapula on MRI, especially in advanced levels of tear retraction, could be more reliable and representative for assessment of the degree of fatty infiltration within the muscle bulk that could help predict tear repairability and therefore improve clinical decision-making which should be studied further in clinical studies.

Ferroelectric Domain and Switching Dynamics in Curved In2Se3: First-Principles and Deep Learning Molecular Dynamics Simulations.

Despite its prevalence in experiments, the influence of complex strain on material properties remains understudied due to the lack of effective simulation methods. Here, the effects of bending, rippling, and bubbling on the ferroelectric domains are investigated in an In2Se3 monolayer by density functional theory and deep learning molecular dynamics simulations. Since the ferroelectric switching barrier can be increased (decreased) by tensile (compressive) strain, automatic polarization reversal occurs in α-In2Se3 with a strain gradient when it is subjected to bending, rippling, or bubbling deformations to create localized ferroelectric domains with varying sizes. The switching dynamics depends on the magnitude of curvature and temperature, following an Arrhenius-style relationship. This study not only provides a promising solution for cross-scale studies using deep learning but also reveals the potential to manipulate local polarization in ferroelectric materials through strain engineering.

Nanoscale Diamane Spiral Spring for High Mechanical Energy Storage.

A compact, stable, sustainable, and high-energy density power supply system is crucial for the engineering deployment of mobile electromechanical devices/systems either at the small- or large-scale. This work proposes a spiral-based mechanical energy storage scheme utilizing the newly synthesized 2D diamane. Atomistic simulations show that diamane spiral can achieve a high theoretical gravimetric energy density of about 564 Wh kg-1 , about 14 500 times the steel spring. The interlayer friction between diamane is found to cause a strong stick-slip effect that results in local stress/strain concentration. As such, the energy storage capacity of the diamane spiral can be tuned by suppressing the influence from the interlayer friction. Simulations affirm that higher gravimetric energy density can be achieved by reducing the turn number or adopting a low friction contact pair. The fundamental principles that dominate the energy storage capacity of the spiral spring are theoretically analyzed, respectively. The obtained insights suggest that the 2D vdW solids can be promising candidates to construct spiral structures with a high gravimetric energy density. This work should be beneficial for the design of reliable, stable, and sustainable nanoscale mechanical energy storage schemes that can be used as an alternative low-carbon footage energy supplier for novel micro-/nanoscale devices or systems.

Exceptional Deformability of Wurtzite Zinc Oxide Nanowires with Growth Axial Stacking Faults.

To ensure reliability and facilitate the strain engineering of zinc oxide (ZnO) nanowires (NWs), it is significant to understand their flexibility thoroughly. In this study, single-crystalline ZnO NWs with rich axial pyramidal I (π1) and prismatic stacking faults (SFs) are synthesized by a metal oxidation method. Bending properties of the as-synthesized ZnO NWs are investigated at the atomic scale using an in situ high-resolution transmission electron microscopy (HRTEM) technique. It is revealed that the SF-rich structures can foster multiple inelastic deformation mechanisms near room temperature, including active axial SFs' migration, deformation twinning and detwinning process in the NWs with growth π1 SFs, and prevalent nucleation and slip of perfect dislocations with a continuous increased bending strain, leading to tremendous bending strains up to 20% of the NWs. Our results record ultralarge bending deformations and provide insights into the deformation mechanisms of single-crystalline ZnO NWs with rich axial SFs.

Machine learning-based modeling in food processing applications: State of the art.

Food processing is a complex, multifaceted problem that requires substantial human interaction to optimize the various process parameters to minimize energy consumption and ensure better-quality products. The development of a machine learning (ML)-based approach to food processing applications is an exciting and innovative idea for optimizing process parameters and process kinetics to reduce energy consumption, processing time, and ensure better-quality products; however, developing such a novel approach requires significant scientific effort. This paper presents and evaluates ML-based approaches to various food processing operations such as drying, frying, baking, canning, extrusion, encapsulation, and fermentation to predict process kinetics. A step-by-step procedure to develop an ML-based model and its practical implementation is presented. The key challenges of neural network training and testing algorithms and their limitations are discussed to assist readers in selecting algorithms for solving problems specific to food processing. In addition, this paper presents the potential and challenges of applying ML-based techniques to hybrid food processing operations. The potential of physics-informed ML modeling techniques for food processing applications and their strategies is also discussed. It is expected that the potential information of this paper will be valuable in advancing the ML-based technology for food processing applications.

2D ferroelectric devices: working principles and research progress.

Two-dimensional (2D) ferroelectric materials are promising for use in high-performance nanoelectronic devices due to the non-volatility, high storage density, low energy cost and short response time originating from their bistable and switchable polarization states. In this mini review, we first discuss the mechanism and operation principles of ferroelectric devices to facilitate understanding of these novel nanoelectronics and then summarize the latest research progress of electronic devices based on 2D ferroelectrics. Finally, the perspectives for future research and development directions in various fields are provided. We expect this will provide an overview regarding the application of 2D ferroelectrics in electronic appliances.

Effect of hydroxylysine-O-glycosylation on the structure of type I collagen molecule: A computational study.

Collagen undergoes many types of post-translational modifications (PTMs), including intracellular modifications and extracellular modifications. Among these PTMs, glycosylation of hydroxylysine (Hyl) is the most complicated. Experimental studies demonstrated that this PTM ceases once the collagen triple helix is formed and that Hyl-O-glycosylation modulates collagen fibrillogenesis. However, the underlying atomic-level mechanisms of these phenomena remain unclear. In this study, we first adapted the force field parameters for O-linkages between Hyl and carbohydrates and then investigated the influence of Hyl-O-glycosylation on the structure of type I collagen molecule, by performing comprehensive molecular dynamic simulations in explicit solvent of collagen molecule segment with and without the glycosylation of Hyl. Data analysis demonstrated that (i) collagen triple helices remain in a triple-helical structure upon glycosylation of Hyl; (ii) glycosylation of Hyl modulates the peptide backbone conformation and their solvation environment in the vicinity and (iii) the attached sugars are arranged such that their hydrophilic faces are well exposed to the solvent, while their hydrophobic faces point towards the hydrophobic portions of collagen. The adapted force field parameters for O-linkages between Hyl and carbohydrates will aid future computational studies on proteins with Hyl-O-glycosylation. In addition, this work, for the first time, presents the detailed effect of Hyl-O-glycosylation on the structure of human type I collagen at the atomic level, which may provide insights into the design and manufacture of collagenous biomaterials and the development of biomedical therapies for collagen-related diseases.

In Situ Atomic-Scale Study on the Ultralarge Bending Behaviors of TiO2-B/Anatase Dual-Phase Nanowires.

It is challenging but important to understand the mechanical properties of one-dimensional (1D) nanomaterials for their design and integration into nanodevices. Generally, brittle ceramic nanowires (NWs) cannot withstand a large bending strain. Herein, in situ bending deformation of titanium dioxide (TiO2) NWs with a bronze/anatase dual-phase was carried out inside a transmission electron microscopy (TEM) system. An ultralarge bending strain up to 20.3% was observed on individual NWs. Through an in situ atomic-scale study, the large bending behavior for a dual-phase TiO2 NW was found to be related to a continuous crystalline-structure evolution including phase transition, small deformation twinning, and dislocation nucleation and movements. Additionally, no amorphization or crack occurred in the dual-phase TiO2 NW even under an ultralarge bending strain. These results revealed that an individual ceramic NW can undergo a large bending strain with rich defect activities.

Adsorption of Collagen-like Peptides onto Gold Nanosurfaces.

The molecular behavior of proteins in the presence of inorganic surfaces is of fundamental biological significance. Examples include extracellular matrix proteins interacting with gold nanoparticles and metallic implant biomaterials, such as titanium and stainless steels. Uncharged inorganic surfaces that interact strongly with the solution phase (hydrophilic surfaces) have been commonly used in disease treatments. A deep understanding of the molecular behavior of body proteins in the presence of hydrophilic surfaces is important in terms of clinical applications. However, the adsorption mechanism of proteins onto hydrophilic surfaces remains not fully understood. Here, comprehensive molecular dynamics simulations are carried out to study the molecular response of a human collagen molecule segment (CMS) to the presence of a planar gold surface (AuNS) in explicit solvent, aiming to unravel the adsorption mechanism of proteins onto hydrophilic surfaces. The results demonstrate that in the presence of AuNS, the CMS first biasedly diffuses toward AuNS, followed by anchoring to the gold surface, and finally adsorbs stepwise onto AuNS, where the protein adjusts its structure to maximize the interaction with AuNS. We conclude that adsorption of proteins onto hydrophilic surfaces adheres to three steps, namely, biased diffusion, anchoring, and stepwise adsorption accompanied by structural adaptation. The obtained adsorption mechanism provides insights into the development of inorganic surfaces for biomedical and therapeutic applications.

Interaction of gold nanosurfaces/nanoparticles with collagen-like peptides.

Nanotechnology has quickly emerged as a promising research field with potential effects in disease treatments. For example, gold nanoparticles (AuNPs) have been extensively used in diagnostics and therapeutics. When administrated into human tissues, AuNPs first encounter extracellular matrix (ECM) molecules. Amongst all the ECM components, collagen is the main tension-resisting constituent, whose biofunctional and mechanical properties are strongly dependent on its hierarchical structure. Therefore, an in-depth understanding of the structural response of collagen to the presence of gold nanosurfaces (AuNS) and AuNPs is crucial in terms of clinical applications of AuNPs. However, detailed understanding of the molecular-level and atomic-level interaction between AuNS/AuNPs and collagen in the ECM is elusive. In this study, comprehensive molecular dynamics (MD) simulations have been performed to investigate the molecular behaviour of a collagen molecule segment (CMS) in the presence of AuNS/AuNPs in explicit water, aiming to explore the interaction of AuNS/AuNPs with collagen triple helices at the molecular and atomic levels. The results show that the CMS forms a rapid association with AuNS/AuNPs and undergoes a severe unfolding upon adsorption on AuNS/AuNPs, indicating an unfolding propensity of gold surfaces. We conclude that collagen triple helices unfold readily on AuNS and bare AuNPs, due to the interaction of gold surfaces with the protein backbone. The revealed clear unfolding nature and the unravelled atomic-level unfolding mechanism of collagen triple helices onto AuNPs contribute to the development of AuNPs for biomedical and therapeutic applications, and the design of gold-binding proteins.

General existence of flexural mode doublets in nanowires targeting vectorial sensing applications.

Nanowires (NWs) are one of the fundamental building blocks for nanoscale devices, and have been frequently utilized as mechanical resonators. Earlier studies show that ultra-sensitive vectorial sensing toolkits can be fabricated by changing the flexural mode of NWs to oscillation doublets along two orthogonal directions. Based on in silico studies and the Timoshenko beam theory, this work finds that the dual orthogonal flexural mode of NWs can be effectively controlled through the proper selection of their growth direction. It is found that metallic NWs with a directional-independent shear modulus possess a single flexural mode. However, NWs with a directional-dependent shear modulus naturally exhibit flexural mode doublets, which do not disappear even with increasing slenderness ratio. Further studies show that such a feature generally exists in other NWs, such as Si NWs. Mimicking a pendulum configuration as used in NW-based scanning force microscopy, the cantilevered 110 Si NW demonstrates zeptogram mass resolution and a force sensitivity down to the order of 10-24 N Hz-1/2 (yN Hz-1/2) in both transverse directions. The findings in this work open up a new and facile avenue to fabricate 2D vectorial force sensors, which could enable ultra-sensitive and novel detection devices/systems for 2D effects, such as the anisotropy strength of atomic bonds.

Simplest MOF Units for Effective Photodriven Hydrogen Evolution Reaction.

Metal-organic frameworks (MOFs) combining the merits of both organic and inorganic functional building structures are fundamentally important and can meet the requirement of vast scientific and technological applications. Intrigued from the fact that transition metals (TMs) are widely embedded in the carbon sp2 network or strongly interact with a bare graphene edge, the single transition metal atom may work as a linker to connect carbon chains to build nanoarchitectures. A new MOF building structure, [Metal-Carbon-(Benzene) i-Chain] n ring abbreviated as [M-CB iC] n (M = Ti, V, and Cr), with increasing carbon chain length i (= 0, 1, 2, ···), was proposed as carbon chains CB iC connected by a single transition metal atom M to form a ring structure with multiedges n (= 2-6), based on advanced computational methods. They are thermodynamically stable and chemically and physically versatile with ring shape, electronic structures, optical response, as well as hydrogen adsorption energy that vary by changing the length of the carbon chain, the edge number of rings, or the type of connecting metal atoms. The optical response to incoming light of [M-CB iC] n rings can be adjustable to cover the entire visible solar spectrum range and exhibit a red shift by either increasing the edge number n or filling the d bands in connecting transition metals. In combination with their ideal adsorption energy of hydrogen atoms, |Δ GH*|, the proposed [M-CB iC] n building structure is attractive for photocatalytic or photoelectrochemical hydrogen evolution applications when they are extended in space to build up 1D, 2D, and 3D MOF frameworks.

Two dimensional boron nanosheets: synthesis, properties and applications.

Two dimensional boron nanosheets have been proposed theoretically for a decade, but were not experimentally synthesized until very recently. Research into their fundamental properties and device applications has since seen exponential growth. In this perspective, we review recent research progress related to 2D boron sheets, touching upon the topics of fabrication, properties, and applications, as well as discussing challenges and future research directions. We highlight the intrinsic electronic and mechanical properties of boron sheets, resulting from their diverse structures. Their facile fabrication and novel properties have inspired the design and demonstration of new nanodevices; however, further progress relies on resolving technical obstructions, like non-scalable fabrication techniques. We also briefly describe some feasible schemes that can address the associated challenges. It is expected that this fascinating material will offer tremendous opportunities for research and development in the foreseeable future.

Investigation of red blood cell mechanical properties using AFM indentation and coarse-grained particle method.

BACKGROUND: Red blood cells (RBCs) deform significantly and repeatedly when passing through narrow capillaries and delivering dioxygen throughout the body. Deformability of RBCs is a key characteristic, largely governed by the mechanical properties of the cell membrane. This study investigated RBC mechanical properties using atomic force microscopy (AFM) with the aim to develop a coarse-grained particle method model to study for the first time RBC indentation in both 2D and 3D. This new model has the potential to be applied to further investigate the local deformability of RBCs, with accurate control over adhesion, probe geometry and position of applied force. RESULTS: The model considers the linear stretch capacity of the cytoskeleton, bending resistance and areal incompressibility of the bilayer, and volumetric incompressibility of the internal fluid. The model's performance was validated against force-deformation experiments performed on RBCs under spherical AFM indentation. The model was then used to investigate the mechanisms which absorbed energy through the indentation stroke, and the impact of varying stiffness coefficients on the measured deformability. This study found the membrane's bending stiffness was most influential in controlling RBC physical behaviour for indentations of up to 200 nm. CONCLUSIONS: As the bilayer provides bending resistance, this infers that structural changes within the bilayer are responsible for the deformability changes experienced by deteriorating RBCs. The numerical model presented here established a foundation for future investigations into changes within the membrane that cause differences in stiffness between healthy and deteriorating RBCs, which have already been measured experimentally with AFM.

Graphene-like Two-Dimensional Ionic Boron with Double Dirac Cones at Ambient Condition.

Recently, partially ionic boron (γ-B28) has been predicted and observed in pure boron, in bulk phase and controlled by pressure [ Nature 2009 , 457 , 863 ]. By using ab initio evolutionary structure search, we report the prediction of ionic boron at a reduced dimension and ambient pressure, namely, the two-dimensional (2D) ionic boron. This 2D boron structure consists of graphene-like plane and B2 atom pairs with the P6/mmm space group and six atoms in the unit cell and has lower energy than the previously reported α-sheet structure and its analogues. Its dynamical and thermal stability are confirmed by the phonon-spectrum and ab initio molecular dynamics simulation. In addition, this phase exhibits double Dirac cones with massless Dirac Fermions due to the significant charge transfer between the graphene-like plane and B2 pair that enhances the energetic stability of the P6/mmm boron. A Fermi velocity (vf) as high as 2.3 × 10(6) m/s, which is even higher than that of graphene (0.82 × 10(6) m/s), is predicted for the P6/mmm boron. The present work is the first report of the 2D ionic boron at atmospheric pressure. The unique electronic structure renders the 2D ionic boron a promising 2D material for applications in nanoelectronics.

SPH-DEM approach to numerically simulate the deformation of three-dimensional RBCs in non-uniform capillaries.

BACKGROUND: Blood continuously flows through the blood vessels in the human body. When blood flows through the smallest blood vessels, red blood cells (RBCs) in the blood exhibit various types of motion and deformed shapes. Computational modelling techniques can be used to successfully predict the behaviour of the RBCs in capillaries. In this study, we report the application of a meshfree particle approach to model and predict the motion and deformation of three-dimensional RBCs in capillaries. METHODS: An elastic spring network based on the discrete element method (DEM) is employed to model the three-dimensional RBC membrane. The haemoglobin in the RBC and the plasma in the blood are modelled as smoothed particle hydrodynamics (SPH) particles. For validation purposes, the behaviour of a single RBC in a simple shear flow is examined and compared against experimental results. Then simulations are carried out to predict the behaviour of RBCs in a capillary; (i) the motion of five identical RBCs in a uniform capillary, (ii) the motion of five identical RBCs with different bending stiffness (K b ) values in a stenosed capillary, (iii) the motion of three RBCs in a narrow capillary. Finally five identical RBCs are employed to determine the critical diameter of a stenosed capillary. RESULTS: Validation results showed a good agreement with less than 10% difference. From the above simulations, the following results are obtained; (i) RBCs exhibit different deformation behaviours due to the hydrodynamic interaction between them. (ii) Asymmetrical deformation behaviours of the RBCs are clearly observed when the bending stiffness (K b ) of the RBCs is changed. (iii) The model predicts the ability of the RBCs to squeeze through smaller blood vessels. Finally, from the simulations, the critical diameter of the stenosed section to stop the motion of blood flow is predicted. CONCLUSIONS: A three-dimensional spring network model based on DEM in combination with the SPH method is successfully used to model the motion and deformation of RBCs in capillaries. Simulation results reveal that the condition of blood flow stopping depends on the pressure gradient of the capillary and the severity of stenosis of the capillary. In addition, this model is capable of predicting the critical diameter which prevents motion of RBCs for different blood pressures.

Tuning the resonance properties of 2D carbon nanotube networks towards a mechanical resonator.

The capabilities of the mechanical resonator-based nanosensors in detecting ultra-small mass or force shifts have driven a continuing exploration of the palette of nanomaterials for such application purposes. Based on large-scale molecular dynamics simulations, we have assessed the applicability of a new class of carbon nanomaterials for nanoresonator usage, i.e. the single-wall carbon nanotube (SWNT) network. It is found that SWNT networks inherit excellent mechanical properties from the constituent SWNTs, possessing a high natural frequency. However, although a high quality factor is suggested from the simulation results, it is hard to obtain an unambiguous Q-factor due to the existence of vibration modes in addition to the dominant mode. The nonlinearities resulting from these extra vibration modes are found to exist uniformly under various testing conditions including different initial actuations and temperatures. Further testing shows that these modes can be effectively suppressed through the introduction of axial strain, leading to an extremely high quality factor in the order of 10(9) estimated from the SWNT network with 2% tensile strain. Additional studies indicate that the carbon rings connecting the SWNTs can also be used to alter the vibrational properties of the resulting network. This study suggests that the SWNT network can be a good candidate for applications as nanoresonators.