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Nanoparticles (NPs) are promising candidates for different biomedical applications due to their excellent antimicrobial applications. However, the applications become limited due to the higher cost of NP synthesis. In his research work, Hydroxyapatite Nanoparticles (HANPs) have been synthesized in a cost-effective method to apply in biomedical applications. The synthesized HANPs have been characterized by different morphological and antimicrobial characterization methods. Ultraviolet–Visible (UV) spectroscopy was performed and a peak was obtained at 271nm which confirmed the formation of NPs and opened a new door for further analysis. Fourier Transformed Infrared Spectroscopy (FTIR) has been performed and the presence of functional groups such as hydroxides carbonates and phosphates have been identified. Transmission Electron Microscopy (TEM) analysis reveals the circular and smaller shape of the synthesized HANPs. The chemical elements of HA have been identified by EDS analysis. Sharp peaks identified by the X-Ray Diffraction (XRD) analysis confirm the formation of crystals in the synthesized HANPs. An excellent antimicrobial performance which is 99.99% has been obtained from the gram-positive and gram-negative bacterial strains. The obtained results suggest the potentiality of the synthesized HANPs in biomedical applications.

A molecular simulation study of the mesoscale self-assembly of tethered nanoparticles having a cubic geometry is presented. Minimal models of the tethered nanocubes are developed to represent a polyhedral oligomeric silsesquioxane (POSS) molecule with polymeric substituents. The models incorporate some of the essential structural features and interaction specificity of POSS molecules, and facilitate access to the long length and timescales pertinent to the assembly process while foregoing atomistic detail. The types of self-assembled nanostructures formed by the tethered nanocubes in solution are explored via Brownian dynamics simulations using these minimal models. The influence of various parameters, including the conditions of the surrounding medium, the molecular weight and chemical composition of the tether functionalities, and the number of tethers on the nanocube, on the formation of specific structures is demonstrated. The role of cubic nanoparticle geometry on self-assembly is also assessed by comparing the types of structures formed by tethered nanocubes and by their flexible coil triblock copolymer and tethered nanosphere counterparts. Morphological phase diagrams are proposed to describe the behavior of the tethered nanocubes.

The main aim of this paper is to examine the discharging process with insertion of wavy surface and changing shape of nanoparticles. Contours were presented in the form of contours and profiles of energy and temperatures. To get the acceptable accuracy, adaptive grid is employed and time steps for each iteration are variable. The outputs indicate that augmenting A and selection of platelet shape lead to a faster solidification. With augment of $A$, 14% reduction has been reported for ($m=3$). Such percentage augments with the rise of $m$ and 14.03% reduction were reported for ($m=5.7$). At $m=5.7$, augmenting $A$ from 0.1 to 0.3 makes the time to reduce from 44.16s to 37.96s. Lower level of energy was reported for platelet shapes, which means higher liquid fraction of domain. Temperature declines with augment of $A$ and $A=0.1$ prolongs process of about 14.03% in the existence of platelet shape.

To illustrate the role of Lorentz force on migration of nanopowders, CVFEM simulation has been reported in current research. The chamber contains hybrid nanomaterial and made up form porous media. Momentum equations have been modified for present paper with adding new source terms. The mentioned method works based on FEM in generation of mesh and calculation of gradient of scalars while it uses FVM approach for employing source terms. Testing with benchmark article shows the nice accuracy. Increase of permeability can enhance the speed of nanopowders and iso-temperature lines shapes become complicated. Impose of MHD creates new force against buoyancy and declines the velocity of the nanomaterial. Also, complication of isotherms declines with rise of Ha. With growth of Da, value of $\mathrm{\Psi }$ increases about 111% and 64.2% when $\mathrm{\text{Ha}}=0$ and 20, respectively. Also, augment of Ha results in reduction of velocity about 30% and 47.6% when $\mathrm{\text{Da}}=0.01$ and 100. Given $\mathrm{\text{Da}}=5\mathrm{\text{Ha}}=100$, Nu for $\mathrm{\text{Ra}}=\mathrm{\text{1e}}5$ is 6.83 times bigger than case with $log(\mathrm{\text{Ra}})=3$. Nu decreases to about 67.28% with increase of Ha when $\mathrm{\text{Da}}=100$, $\mathrm{\text{Ra}}=\mathrm{\text{1e}}5$. As Da increases, Nu rises about 62% when $\mathrm{\text{Ha}}=0$, $\mathrm{\text{Ra}}=\mathrm{\text{1e}}3$.

The thin films of Co-doped and Co₃O₄-doped dielectric LaAlO₃ (LAO) by co-ablation of magnetic metal Co and dielectric LAO on Pt – Ti – SiO₂ – Si substrates have been prepared by pulsed laser deposition. A significant enhancement of dielectric constant of LAO upon doping of Co and cobalt oxide clusters is observed. Furthermore, modulation of the dielectric constant of the thin films by applying a magnetic field is verified, obviously due to the ferromagnetism of Co metal and Co oxide clusters embedded in the LAO thin films. A series of microstructural and dielectric characterizations on the as-prepared thin films have been performed and the mechanism underlying the dielectric enhancement upon the doping of Co and Co₃O₄ clusters is discussed.

The dielectric property of ZnFe₂O₄ – SiO₂ composite thin films deposited on Pt-Ti-SiO₂-Si substrates, prepared by sol-gel method, are investigated. It is observed that the thin films consist of ZnFe₂O₄ nanoparticles embedded in the matrix of SiO₂. Such a composite structure exhibits a significantly enhanced dielectric constant with respect to SiO₂ thin films without too large dielectric loss enhancement.

In this study, electrorheological (ER) behaviour of silica nanocomposite suspensions treated with urea and N, N – dimethylformamide (DMF) in DC electric field has been investigated. While the ER effect of the neat silica itself was very low, the modification of silica nanoparticles improved compatibility of the solid and liquid phase and increased considerably ER activity of the system. In contrast to maximum possible concentration about 5 wt.% of neat silica due to particle aggregation 20 wt.% suspension of treated particles with low field-off viscosity could be prepared. The dielectric measurements showed that with increasing amount of urea deposited on the silica particles both the difference between the limit values of the relative permittivities and the relaxation frequency increased. This indicates a great influence of both particle polarizability and the rate of rearrangement of the ER structure in the electric field on the ER intensity. After DMF addition the changes in dielectric properties reflected the higher ER activity. At higher particle loading (25 wt.%) mutual particle interaction increased and field-off viscosity steeply rose. The comparison of the behavior of 20 and 25 wt.% suspensions of modified particles showed that even if high yield stress at higher particle content under electric field application sets in, its relative increase indicating the ER efficiency due to high field-off value may be much lower than at lower suspension loading.

Nanosized zinc stannate Zn₂SnO₄ (ZTO) was synthesized via a simple hydrothermal method using sodium hydroxide NaOH as a mineralizer. Hydrothermally treated at 150, 200, and 250°C for 24 h and 48 h, the X-ray diffraction (XRD) pattern showed that highly crystalline ZTO nanostructures could be formed at 200 and 250°C. Transmission electron microscopy (TEM) images showed that ZTO nanocubes were formed at 250°C, and a sheet-like structure was found at 200°C. Raman spectra revealed that ZTO had a spinel structure and there were two Raman shift peaks at approximately 668 and 535 cm^-1, which were similar to the peaks of ZTO nanowires. Furthermore, the photocatalytic activity of the ZTO samples was assessed utilizing methylene blue (MB) under ultraviolet irradiation, and the UV-Visible light absorption spectra was investigated to interpret the relationship between photocatalytic properties and light absorptivity. The sheet-like ZTO nanostructures exhibited better photocatalytic activity due to their excellent light absorption properties.

The structure of Ru doped FePt nanoparticles using polyol process was studied. The particle size grown is around 5 nm, and a shell structure might be formed. By selecting the time and temperature of adding the Ru precursors into solution, three different processes to synthesize the FePtRu particles were studied resulting in different growing mechanics. The possible models during the reaction process are also discussed. The phase transition temperature for the as-grown FCC FePt nanoparticle to transform into L1₀FePt nanoparticle is about 823 K which is about the same as the one without doping Ru atoms. From the XAS study of each element, the possible scenario is that: although Ru atoms with the size close to the Pt, they do not totally replace the Pt sites in the FePt alloy. Instead, most of Ru formed a shell outside the FePt nanoparticles and Fe atoms are replaced.

The third-order nonlinearity susceptibility is obtained as a function of wavelength for ZnS/CdSe/ZnS structure. Numerical calculations show that the nonlinear susceptibility of this structure depends on parameters such as structure size, relaxation time and pump photon energy. The intensity and position of third-order nonlinear susceptibility peaks depend on shell thicknesses; smaller thicknesses have peak susceptibility at shorter wavelength.

Annealing study of amorphous bulk and nanoparticle iron at temperatures from 500 K to 1000 K has been carried out using molecular dynamics (MD) simulations. The simulation is performed for models containing 10⁴ particles Fe at both crystalline and amorphous states. We determine changes of the potential energy, pair radial distribution function (PRDF) and distribution of coordination number (DCN) as a function of annealing time. The calculation shows that the aging slightly reduces the potential energy of system. This result evidences that the amorphous sample undergoes different quasi-equilibrated states during annealing. Similar trend is observed for nanoparticles sample. When the samples are annealed at high temperatures we observe the crystallization in both bulk and nanoparticle. In particular, the system undergoes three stages. At first stage the relaxation proceeds slowly so that the energy of system slightly decreases and the samples structure remains amorphous. Within second stage a structural transformation occurs which significantly changes PRDF and DCN for the relatively short time. The energy of the system is dropped considerably and the amorphous structure transforms into the crystalline. Finally, the crystalline sample undergoes the slow relaxation which reduces the energy of system and eliminates structural defects in crystal lattices.

Fe nanoparticles have been investigated by means of molecular dynamics simulation. The nucleation and crystal growth is analyzed through the potential energy and number of different types of atoms. The simulation shows that when the amorphous sample is annealed at 900 K, it is crystallized into bcc phase. We found that as the crystal cluster has a size larger than some critical value, the mean potential energy of different types of atoms decreases in following orders: amorphous-atom → surface-crystal atom → crystal-atom. As a result, the crystal cluster is stable and tends to have a nearly spherical shape. Further, it was shown that small nuclei form frequently in the core and rarely in the surface area. After a long annealing time a cluster expands and reaches the critical radius. Then this cluster grows exponentially with times. The fully crystallized sample consists of the core with crystalline structure and surface shell with amorphous porous structure. The Fe nanoparticle has a number of polymorphs which are stable upon annealing at 300 K. We have analyzed the pair radial distribution function (PRDF) for obtained polymorphs. We found that as the fraction of crystal-atoms is less than 0.18, the PRDF is like those of amorphous metal. However, the left sub-peak is higher than right sub-peak when the fraction of crystal-atoms is less than 0.05.

An explicit calculation of the quantum nonlocal (QNL) polarizability of a metallic nanoparticle is presented, where two quantum longitudinal plasma waves are excited. The QNL generalization of the classical Clausius–Mossotti factor of the system is derived, by means of the quantum hydrodynamic theory in conjunction with the Poisson equation and applying the appropriate additional quantum boundary conditions.

The coalescence, the initial stage of sintering, of two contacted Cu nanoparticles is investigated under different heating rates of 700, 350 and 233 K/ns. The nanoparticles coalesced rapidly at the initial stage when the temperature of the system is low. Then, the nanoparticles collided softly in an equilibrium period. After the system was increased to a high temperature, the shrinkage ratio, gyration radius and atoms’ diffusion started to change dramatically. The lower heating rate can result in smaller shrinkage ratio, larger gyration radius and diffusion of atoms. However, the growth of sintering neck is hardly influenced by the heating rate. The results provide a theoretical guidance for the fundamental understanding and potential application regarding nanoparticle sintering.

Iron (Fe)-based nanoparticles are extremely valuable in biomedical applications owing to their low toxicity and high magnetization values at room temperature. In this study, we synthesized nearly monodisperse iron oxide (Fe₃O₄) and Fe@Fe₃O₄ (core: Fe, shell: Fe₃O${}_4)$ nanoparticles in aqueous medium under argon flow and then, coated them with various biocompatible ligands and silica. In this study, eight types of surface-modified nanoparticles were investigated, namely, Fe₃O₄@PAA (PAA = polyacrylic acid; $M_w$ of PAA = 5100 amu and 15,000 amu), Fe₃O₄@PAA–FA (FA = folic acid; $M_w$ of PAA = 5100 amu and 15,000 amu), Fe₃O₄@PEI–fluorescein (PEI = polyethylenimine; $M_w$ of PEI = 1300 amu), Fe@Fe₃O₄@PEI ($M_w$ of PEI = 10,000 amu), Fe₃O₄@SiO₂ and Fe@Fe₃O₄@SiO₂ nanoparticles. We characterized the prepared surface-modified nanoparticles using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) absorption spectroscopy, a superconducting quantum interference device (SQUID), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and confocal microscopy. Finally, we measured the cytotoxicity of the samples. The results indicate that the surface-modified nanoparticles are biocompatible and are potential candidates for various biomedical applications.

Molecular dynamics simulations were employed to investigate the aggregation of monocrystal and polycrystal nanoparticles. The lattice structure, displacement vector, potential energy, shrinkage ratio, relative gyration radius and mean square displacement of the two systems are compared. The results indicate that the aggregation of polycrystal nanoparticles is more drastic than that of monocrystal nanoparticles. Besides, the polycrystal nanoparticles are found contacted and melted at lower-temperature than that of monocrystal nanoparticles. The reason for all these phenomena is that there is additional surface energy in the grain boundary of polycrystal nanoparticles.

In this paper, crystallization pathway and dynamical heterogeneity (DH) in iron nanoparticle (NP) have been investigated in detail for spherical samples containing 5000 atoms, which were obtained by the molecular dynamics simulation based on Pak–Doyama potential. The crystallization was analyzed through pair radial distribution function, angle distribution, parameter $〈$F${}_{\mathrm{\text{bcc}}}〉$ and transition to different x-types, where x is the bcc, fcc-hcp, ico, 14 or 12. We found that transitions to bcc-type do not happen arbitrarily at any location in NP, but instead they are concentrated in a nonequilibrium region. The crystallization pathway comprises of intermediate states between amorphous and crystalline ones. At the early stage, a large cluster of Cryst-atom formed is located in a middle layer of NP. Then, this cluster grows up and the parameter $〈$F${}_{\mathrm{\text{bcc}}}〉$ for it increases rapidly. At the final stage, the cluster of Cryst-atom is located in a well-equilibrium region covering a major part of NP. It is found that the structure of amorphous and crystalline NPs is strongly heterogeneous and consists of separate regions with different local microstructure. This indicates the DH in NP. We also found that there is a connection between local structures and DH in NP.

Using the Monte Carlo simulation method based on the Metropolis algorithm, we present some results regarding the magnetic and heating properties of three-dimensional nanoparticles composed of a ferromagnetic core surrounded by an antiferromagnetic shell. We investigate the variation of the exchange bias effect and its dependence on the particle shell thickness, as well as on the temperature. In terms of the stochastic dynamics, we applied a time-dependent alternating magnetic field on the system, and calculated the dynamic-order parameters, response functions and the hysteresis loop area from the AC hysteresis curves from which we have also quantified the specific absorption rate (SAR) of the particle over a wide range of field frequencies. A number of interesting results have been found regarding the variation of the heating properties of the system as a function of the antiferromagnetic shell thickness and the period of the alternating field.

Particle coalescence has wide applications in nature and industry. In this study, molecular dynamics (MDs) simulations were employed to examine the sintering of Cu and Au nanoparticles, as well as two other systems, namely, Cu nanoparticles and Au nanoparticles. The results suggested that, the Au atoms diffused through the outer area of the sintering neck before the nanoparticles were fused into one sphere. The possible reason was that the Au atoms resembled fluid, which could be ascribed to the local thermal energy at the contact area. Typically, the change in energy per atom from 300 K to the contact temperature denoted that less energy was required for the atoms in the pure Cu system to contact with each other than those in the other two systems.

Two-dimensional material-based photodetectors (PDs) show great potential owing to unique optoelectronic characteristics and attract much attention in research. However, poor absorption of two-dimensional material remains a vital restriction. Responsivity improvement by applying Au nanoparticles (NPs) through surface plasmon (SP) is studied both in theory and simulation. The effect of size and NPs distribution density is analyzed concerning absorption promotion and fabrication feasibility. Both absorption spectrum and inner electric field are studied. A novel face-to-face PD is proposed that performs better in visible range. The results can be helpful in two-dimensional material PD design and fabrication where high responsivity is required.