Modeling of polyethylene, poly(l-lactide), and CNT composites: a dissipative particle dynamics study

Dissipative particle dynamics (DPD), a mesoscopic simulation approach, is used to investigate the effect of volume fraction of polyethylene (PE) and poly(l-lactide) (PLLA) on the structural property of the immiscible PE/PLLA/carbon nanotube in a system. In this work, the interaction parameter in DPD simulation, related to the Flory-Huggins interaction parameter χ, is estimated by the calculation of mixing energy for each pair of components in molecular dynamics simulation. Volume fraction and mixing methods clearly affect the equilibrated structure. Even if the volume fraction is different, micro-structures are similar when the equilibrated structures are different. Unlike the blend system, where no relationship exists between the micro-structure and the equilibrated structure, in the di-block copolymer system, the micro-structure and equilibrated structure have specific relationships

Surface Morphological and Nanomechanical Properties of PLD-Derived ZnO Thin Films

This study reports the surface roughness and nanomechanical characteristics of ZnO thin films deposited on the various substrates, obtained by means of atomic force microscopy (AFM), nanoindentation and nanoscratch techniques. ZnO thin films are deposited on (a- and c-axis) sapphires and (0001) 6H-SiC substrates by using the pulsed-laser depositions (PLD) system. Continuous stiffness measurements (CSM) technique is used in the nanoindentation tests to determine the hardness and Young’s modulus of ZnO thin films. The importance of the ratio (H/Efilm) of elastic to plastic deformation during nanoindentation of ZnO thin films on their behaviors in contact-induced damage during fabrication of ZnO-based devices is considered. In addition, the friction coefficient of ZnO thin films is also presented here

Fibers and Conductive Films Using Silver Nanoparticles and Nanowires by Near-Field Electrospinning Process

The silver nanowires (AgNWs) and silver nanoparticles (AgNPs) were synthesized. With near-field electrospinning (NFES) process, fibers and thin films with AgNPs and AgNWs were fabricated. In the NFES process, 10 k voltage was applied and the AgNPs and AgNWs fibers can be directly orderly collected without breaking and bending. Then, the characteristics of the fibers were analyzed by four-point probe and EDS. The conductive film was analyzed. When the thickness of films with AgNWs and AgNPs was 1.6 µm, the sheet resistance of films was 0.032 Ω/sq which was superior to that of the commercial ITO. The transmissivity of films was analyzed. The transmissivity was inversely proportional to sheet resistance of the films. In the future, the fibers and films can be used as transparent conductive electrodes

Tuning the electronic properties of boron nitride nanotube by mechanical uni-axial deformation: a DFT study

The effect of uni-axial strain on the electronic properties of (8,0) zigzag and (5,5) armchair boron nitride nanotubes (BNNT) is addressed by density functional theory calculation. The stress-strain profiles indicate that these two BNNTS of differing types display very similar mechanical properties, but there are variations in HOMO-LUMO gaps at different strains, indicating that the electronic properties of BNNTs not only depend on uni-axial strain, but on BNNT type. The variations in nanotube geometries, partial density of states of B and N atoms, B and N charges are also discussed for (8,0) and (5,5) BNNTs at different strains

An Investigation into the Structural Features and Thermal Conductivity of Silicon Nanoparticles Using Molecular Dynamics Simulations

Abstract The structural features and thermal conductivity of silicon nanoparticles of diameter 2-12 nm are studied in a series of molecular dynamics simulations based on the Stilling-Weber (SW) potential model. The results show that the cohesive energy of the particles increases monotonically with an increasing particle size and is independent of the temperature. It is found that particles with a diameter of 2 nm have a heavily reconstructed geometry which generates lattice imperfections. The thermal conductivity of the nanoscale silicon particles increases linearly with their diameter and is two orders of magnitude lower than that of bulk silicon. The low thermal conductivity of the smallest nanoparticles is thought to be the result of particle boundary and lattice imperfections produced during fabrication, which reduce the phonon mean free path (MFP). Finally, it is found that the influence of the temperature on the thermal conductivity decreases significantly as the temperature increases. Again, this is thought to be the result of a reduced phonon MFP at elevated temperatures

Temperature dependent Young's modulus of ZnO nanowires

A thermal resonant method was developed to accurately determine the temperature-dependent Young's moduli of nanowires. In this method, the frequency spectra of a [0001]-oriented ZnO nanowire cantilever at elevated temperatures were measured using scanning laser Doppler vibrometry. The temperature-dependent Young's moduli were derived from the resonant frequencies using Euler-Bernoulli beam theory. It was found that the modulus of ZnO nanowires decreased linearly with the increase of temperature from 300 to 650 K, independent of the nanowire diameter ranged from 101 to 350 nm. The temperature coefficient that defines the linear relationship between the dimensionless modulus and temperature is -(1.087 ± 0.018) 10 K, which agrees with that of -(1.266 ± 0.549) × 10 K, being calculated using molecular dynamics with a partially charged rigid ion model

Unraveling the binding mechanisms of SARS-CoV-2 variants through molecular simulations

The emergence of SARS-CoV-2 variants like Delta (AY.29) and Omicron (EG.5) poses continued challenges for vaccines and therapeutics. Mutations in the viral spike protein are key in altering infectivity and immune evasion. This study uses computational modeling to investigate the molecular binding mechanisms between spike protein variants and the ACE2 host receptor. Using the MARTNI force field, coarse-grained molecular dynamics (CGMD) simulations and nudged elastic band (NEB) calculations explore spike-ACE2 interactions for the wild type, Delta variant, and Omicron variant. The simulations reveal Omicron has the strongest binding affinity at −128.35 ± 10.91 kcal/mol, followed by Delta and wild type. Key mutations in Delta and Omicron, like Q493R and Q498R, optimize electrostatic contacts, enhancing ACE2 interactions. The wild-type spike has the highest transition state energy barrier at 17.87 kcal/mol, while Delta has the lowest barrier at 9.21 kcal/mol. Despite slightly higher dual barriers, Omicron's increased binding energy lowers its overall barrier to rapidly bind ACE2. These findings provide residue-level insights into mutation effects on SARS-CoV-2 infectivity. The computational modeling elucidates mechanisms underlying spike-ACE2 binding kinetics, aiding the development of vaccines and therapies targeting emerging viral strains

CO Oxidation Mechanism on Tungsten Nanoparticle

CO oxidations on the surface of tungsten nanoparticle W₁₀ and on W(111) surface were investigated by density functional theory (DFT) calculations. The molecular structures and surface–adsorbate interaction energies of CO and O₂ on the W₁₀ and W(111) surfaces were predicted. Three CO oxidation reactions of CO + O₂ → CO₂ + O, CO + O + O → CO₂ + O, and CO + O → CO₂ were considered in Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) reaction mechanisms. The nudged elastic band (NEB) method was applied to locate transition states and minimum energy pathways (MEP) of CO oxidation on the W₁₀ and W(111) surfaces. All reaction barriers were predicted, implying the CO oxidations on both the W₁₀ nanoparticle and W(111) surfaces prefer the ER mechanism. The electronic density of states (DOS) was calculated to understand the interaction between adsorbates and surfaces for the CO oxidation process. In this study, we have demonstrated that the catalytic ability of W₁₀ nanoparticles is superior to that of the W(111) surface for CO oxidation