Narrow Results

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.

Carbon-encapsulated Fe nanoparticles were synthesized by a modified arc plasma method using methane and starch as carbon sources, respectively. The particles were characterized in detail by transmission electron microscope and X-ray powder diffraction. They are somewhat spherical in shape and the coating layers of the two sample types are composed of amorphous carbon. Magnetic measurements using a vibrating sample magnetometer demonstrate that the prepared composites have different magnetic properties.

Amino-modified Fe₃O₄ magnetic nanocomposite particles were prepared by one-step glycothermal method. The shape and morphology of Fe₃O₄ particles change when a small amount of water is added as a co-solvent in the glycothermal method. The morphology and structure of the sample were characterized and measured by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. TEM images show that the morphology of the samples is from irregular polyhedron to spherical particles. Average diameter of particles is approximately 70/40/10 nm and more evenly distributed. XRD results show that the samples are cubic spinel structure. FTIR results show that a chemical bonds combination exists between the amino and iron oxide, nano-iron oxide are modified by the amino.

The vibrational properties of nanoparticles coupled with surrounding media are of recent interest. These nanostructures can be modeled as nanoscale spherical solids. In this paper, new formulation based on the nonlocal elasticity theory is proposed to investigate radial vibrations of the nanoparticles immersed in fluid medium. The nanoparticles with size ranging from 1 nm to 10 nm are discussed. The nanoparticles are considered elastic, homogeneous and anisotropic. Along the contact surface between the nanoparticle and the fluid, the compatibility requirement is applied and the Bessel functions are used to obtain the complex frequency equation. Numerical results are evaluated, and their comparisons are performed to confirm the validity and accuracy of the proposed method. Furthermore, the model is used to elucidate the effect of small scale on the vibration of several nanoparticles. Our results show that the small scale is essential for the radial vibration of nanoparticles when the nanoparticle radius is smaller than 2 nm.

In this paper, we study the behavior of the particle in the paraelectric phase near the bulk critical temperature (a = 0) (in our units) and near the particle critical temperature (a_d) using the fluctuation–dissipation theorem through the power spectrum density S(ω) at zero frequency ω = 0 in the particle. This power spectrum density is found here to have three regimes as concerning the temperature dependence for a given particle diameter. The first one is above the bulk critical temperature, the second one is at the bulk critical temperature and the third is below the bulk critical temperature and above the particle critical temperature. Decreasing temperature fluctuations of the order parameter (polarization) change from the bulk-like to the particle-like due to particle form. Divergency of the bulk spectrum density S_b(0) at the bulk critical temperature a = 0 is compensated in the particle by the contribution ≈a² due to the particle form. The power spectrum density S(0) near the particle critical temperature diverges with the exponent 2, we obtain , where T_{c, d} is the particle critical temperature in the temperature variable T. Our results are new and are exact within the model used.

Using molecular dynamics simulation, we have studied the structural evolution of FeB nanoparticle under annealing and the physical properties of its polymorphs such as crystalline, amorphous and mixed samples. The main focus of present work is the crystallization mechanism and the local structure of polymorphs of FeB nanoparticle. The simulation result shows that the amorphous sample undergoes the crystallization via the nucleation mechanism. During the crystallization, B atoms move out the places where the Fe crystal locates, and diffuse to the boundary region of Fe crystal. The crystal growth proceeds when this boundary region attains specific properties which are defined by the fraction of B atoms and the energies of AB-atoms and CB-atoms. Further our study indicates that unlike amorphous sample, the crystalline and mixed samples consist of three distinct parts including Fe crystalline and two FeB amorphous parts (B-poor and B-rich amorphous part). The different polymorphs of FeB nanoparticle differ in the local structure, size of Fe crystal and energies of different type atoms.

Far-infrared functional nanocomposites were prepared by the co-precipitation method using natural tourmaline $({\mathrm{\text{XY}}}_3{\mathrm{\text{Z}}}_6{\mathrm{\text{Si}}}_6{\mathrm{\text{O}}}_{18}{({\mathrm{\text{BO}}}_3)}_3{\mathrm{\text{V}}}_3\mathrm{\text{W}}$, where $\mathrm{\text{X}}$ is ${\mathrm{\text{Na}}}^{+}$, ${\mathrm{\text{Ca}}}^{2+}$, ${\mathrm{\text{K}}}^{+}$, or vacancy; $\mathrm{\text{Y}}$ is ${\mathrm{\text{Mg}}}^{2+}$, ${\mathrm{\text{Fe}}}^{2+}$, ${\mathrm{\text{Mn}}}^{2+}$, ${\mathrm{\text{Al}}}^{3+}$, ${\mathrm{\text{Fe}}}^{3+}$, ${\mathrm{\text{Mn}}}^{3+}$, ${\mathrm{\text{Cr}}}^{3+}$, ${\mathrm{\text{Li}}}^{+}$, or ${\mathrm{\text{Ti}}}^{4+}$; $\mathrm{\text{Z}}$ is ${\mathrm{\text{Al}}}^{3+}$, ${\mathrm{\text{Mg}}}^{2+}$, ${\mathrm{\text{Cr}}}^{3+}$, or ${\mathrm{\text{V}}}^{3+}$; $\mathrm{\text{V}}$ is ${\mathrm{\text{O}}}^{2-}$, ${\mathrm{\text{OH}}}^{-}$; and $\mathrm{\text{W}}$ is ${\mathrm{\text{O}}}^{2-}$, ${\mathrm{\text{OH}}}^{-}$, or ${\mathrm{\text{F}}}^{-})$ powders, ammonium cerium(IV) nitrate and zirconium(IV) nitrate pentahydrate as raw materials. The reference sample, tourmaline modified with ammonium cerium(IV) nitrate alone was also prepared by a similar precipitation route. The results of Fourier transform infrared spectroscopy show that tourmaline modified with Ce and Zr has a better far-infrared emission property than tourmaline modified with Ce alone. Through characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), the mechanism for oxygen evolution during the heat process in the two composite materials was systematically studied. The XPS spectra show that ${\mathrm{\text{Fe}}}^{3+}$ ratio inside tourmaline modified with Ce alone can be raised by doping Zr. Moreover, it is showed that there is a higher ${\mathrm{\text{Ce}}}^{3+}$ ratio inside the tourmaline modified with Ce and Zr than tourmaline modified with Ce alone. In addition, XRD results indicate the formation of ${\mathrm{\text{CeO}}}_2$ and ${\mathrm{\text{Ce}}}_{1-x}{\mathrm{\text{Zr}}}_x{\mathrm{\text{O}}}_2$ crystallites during the heat treatment and further TEM observations show they exist as nanoparticles on the surface of tourmaline powders. Based on these results, we attribute the improved far-infrared emission properties of Ce–Zr doped tourmaline to the enhanced unit cell shrinkage of the tourmaline arisen from much more oxidation of ${\mathrm{\text{Fe}}}^{2+}$ to ${\mathrm{\text{Fe}}}^{3+}$ inside the tourmaline caused by the change in the catalyst redox properties of ${\mathrm{\text{CeO}}}_2$ brought about by doping with ${\mathrm{\text{Zr}}}^{4+}$. In all samples, tourmaline modified with 7.14 wt.% Ce and 1.86 wt.% Zr calcined at 800${}^{\circ }$C for 5 h has the best far-infrared emission property with the maximum emissivity value of 98%.

In this paper, the optical scattering from cylindrical plasmonic nanoparticles with a core–shell structure, while the core is dielectric coated by a metallic shell such as gold, is investigated by using an analytical solution in the framework of Mie theory. A closed-form (CF) formalism that determines the optical properties of cylindrical nanoparticles based on the series expansions of Bessel functions for the Mie scattering coefficients is introduced and presented. By using this formulation, we will show the optical response and the surface plasmon resonance of hybrid metal-based nanoparticles with cylindrical shape is dependent on the radius of nanoparticle, the refractive index of core and physical environment of nanoparticle. Also, the influence of interband transitions on the optical scattering by plasmonic nanoparticles is discussed and interpreted using the Drude–Lorentz model because the optical properties of metals arise from both the optical excitation of interband transitions and the free electron response.

In this paper, we have comparatively studied the “electron spin resonance” (ESR) of SiO₂ nanoparticles before and after neutron irradiation. From the comparative analysis of samples at the full sweep (sweep 5000 G at center field of 3300 G) in the same system, amount of defects were found to increase. At the field line around 3350 G, we found the free electron $g$ species $(g=2.002)$ and determined that this situation is more sustainable than the other observed cases (the cases existing in values 2.5–3 and 3–5 of $g$-factor). Moreover, expanded section near $g=2.002$ repeated with a sweep of 100 G and at two power due to microwave saturation effects has been studied.

The tendency to improve the properties of insulating materials by incorporating inorganic nanoparticles has become necessary in order to design new insulation systems. In this study, PVC/TiO₂-based nanocomposites with different loadings (3, 5 and 10 wt.%) of TiO₂ nanoparticles were prepared by the solution mixing method. The morphology of the prepared nanocomposites was studied by Atomic Force Microscope (AFM). Experimentally, it was found that as the concentration increases, the size of the surface structural elements and particle size increases. Photoluminescence (PL) analysis of samples shows improvement compared to the pristine polymer. Furthermore, PL intensity for nanocomposites increases depending on the concentration and saturation occurs at a certain amount of titanium dioxide nanoparticles. The increase in luminescence intensity till a certain nanoparticle content is due to the growth of the luminescent surface area. Further saturation is explained by the increase in particle size with no increase or a slight reduction in surface area. Dielectric properties of nanocomposites were studied. It was found that dielectric permittivity of the materials increases as the nanoparticle volume content increases and it reaches at its highest value for the nanocomposites with 3% nanoparticle content. The optical properties of the polymer and nanocomposite films were studied in the region 200 nm to 600 nm. It was found that the PVC/TiO₂ nanocomposites showed enhancement in the absorbance intensities which was more significant for the nanocomposites with higher nanoparticle content compared to the pristine polymer. Furthermore, absorption spectra were used to calculate the optical bandgap of the prepared nanocomposite films and redshift observed in the calculated values of bandgap for nanocomposites. Consequently, it was proved that by incorporating TiO₂ nanoparticles into the polymer matrix, the spectral region of the samples can be expanded resulting in broadened application of such systems in various fields of science and technology.

The crystal structure and atomic dynamics of Fe₃O₄ nanoparticles have been studied. The crystal structure of iron oxide nanoparticles was determined by X-ray diffraction. The analysis showed that the crystal structure of $d\approx$ 50–100 nm dimensional iron oxide corresponds to a high symmetry cubic crystal structure. Calculations have shown that there are four infrared active, five Raman active and seven hyper-Raman active modes in the space group Fd-3m with cubic symmetry. Four of these modes have been observed using Raman spectroscopy: 213, 271, 380 and 591 cm${}^{-1}$. The vibrational modes are interpreted by Gaussian function. It was found that these vibration modes correspond to the vibration of O–Fe–O bonds and iron-oxygen polyhedra.

In this work, the crystal and surface structures of Y₂O₃ nanoparticles were explored. The exploration of crystal structure was carried out by X-ray diffraction method at room temperature and under normal conditions. It was found that the crystal structure of the Y₂O₃ compound has a cubic symmetry with an Ia-3 space group. The lattice parameters have the values: $a=b=c=10.5958$ Å. The surface structure was studied at room temperature and under normal conditions on Scanning Electron Microscope (SEM) microscope. It was found that the nanoparticles of the Y₂O₃ compound being in the range 20–40 nm are of $d\approx 30$ nm size.

In this research work, the effects on the structural and optical properties of e-beam irradiated Al nanoparticles (Al-NPs) by three field sizes, $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$, $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$ and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$ fluence were studied. As a result of systematic observations, it has been possible to study the effect of electron beam on X-ray diffraction (XRD), infrared (IR) spectroscopy and Raman band modifications and, consequently, on the crystal structure and atomic dynamics of Al-NPs. The XRD method determined that Al-NPs are combined with water molecules in the air to form aluminum hydroxide (Al(OH)₃) groups. The Al(OH)₃ formation was not observed in any of the samples irradiated with three different fluences, $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$, $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$ and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$, respectively. Confirmation of these results was also shown in the method of IR spectroscopy. While 12 vibrational modes were observed in the non-irradiated samples, only the vibrational modes corresponding to Al–Al bonds were observed in $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$, $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$, and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$ fluence irradiated samples. It was determined by the Raman spectroscopy method that a low concentration of Al(OH)₃ remains in the samples irradiated with $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$ fluence. Only $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$ and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$ fluence irradiated samples were found to correspond to the XRD and IR spectra, and Raman vibrational modes corresponding to Al–Al bonds were observed. In addition, electron irradiation is a suitable technique to increase the optical properties of nanoparticles by controlling the size of the particles.

FE-SEM and TEM images were used to identify the size of 3C–SiC nanoparticles. Simultaneously, HRTEM and Selected Area Electron Diffraction (SAED) analyses were conducted in order to determine the crystalline nature of the nanoparticles. Moreover, lattice parameters of 3C–SiC nanoparticles have been studied by SAED and XRD analyses. The possible existence of other modified polytypes of silicon carbide was investigated in the experimental sample. The 2$\theta$ angles were determined according to the lattice parameters. Lattice constants and lattice angles for nanocrystalline 3C–SiC particles were defined from the experiments.

To explore the strong coupling between the combined plasmonic mode supported by the metal nanoparticle and the anapole mode of the dielectric nanoparticle, a hybrid metal–dielectric nanoparticle consisting of the combination of silicon and silica together with the gold dimer is designed and analyzed by the finite element method (FEM). Theoretical simulation reveals that the enhanced electric field enhancement reaches 640 and unidirectional scattering with almost zero backscattering at multiple wavelengths is achieved in the far-field region. Moreover, the calculated Purcell factor of 12,193 and sensitivity of 610nm/RIU of the composite nanoparticle are much higher than those of the single-metal or dielectric nanoparticles. In the end, the impact of different structural parameters on the sensitivity, figure of merit and quality factor is analyzed and described, and the maximum sensitivity, Figure of merit and quality factor are found to be 2360nm/RIU, 18.4 RIU${}^{-1}$ and 19.8 RIU${}^{-1}$. The results reveal a new strategy to develop devices for surface-enhancement Raman scattering (SERS), quantum emitters, and sensors.

This study investigates analytically the stability analysis of a nonlinear convective boundary layer (BL) flow of the nanofluids GO-EG and GO-W on a shrinking surface in the presence of a magnetic field and viscous dissipation. We provide a second-order nonlinear ordinary differential equation (NODE) for temperature distribution (TD) and a third-order NODE for velocity profile (VP) coupling based on the thermophysical characteristics of the base fluid and nanofluid as well as similarity transformations (STs) in the fundamental governing equations of momentum and energy. The analytical method HAM is used to answer the equations that have been gathered. In many different industries, such as manufacturing, automotive, microelectronics, and defense, cooling of various types of equipment and devices has very important challenges. To fulfill the demands of the engineering and industrial industries, it is hoped that this issue would significantly improve the heat transformation ratio.

We investigate effects of Co dopant concentration on the structure, as well as optical and electrical transport properties in SrTi_1-xCo_xO₃ (x = 0.00, 0.10, 0.20, 0.30, 0.40, 0.50) nanoparticles prepared by sol–gel method with annealing temperature considerably lower than that employed conventionally. The dopant-induced changes are studied by XRD, Raman, Optical absorption and Impedance measurements. The results show an average particle size of about 30 nm, and decreasing lattice parameters. In the Raman spectra, a broad structure in the region 200–500 cm^-1 is almost absent and the peaks in the region 600–800 cm^-1 show different relative weights with respect to those from SrTiO₃, which is related to structural changes, decreasing gap with increasing dopant concentration in conjuction with increasing grain boundary contribution to the impedance. These results also demonstrate the feasibility of synthesizing the compound with low annealing temperature.

In this work, Silicon oxide (SiO₂) nanoparticles, graphene oxide nanosheet (GO) and GO–SiO₂ nanohybrid composites have been synthesized. The role of GO concentration in the starting solution was investigated and correlated to the morphological, structural and optical properties of the studied samples. The structural studies for nanohybrid composites showed that by increasing GO:weight ratio from 0.5 to 2.0, not only does the SiO₂ crystalline phase change from cubic to orthorhombic, but the structure of GO also transformed to RGO. The related FESEM images indicate that GO sheets are well-covered by SiO₂ nanoparticles with very small grain size and that the accumulation of nanoparticles on each sheet has a high density. Linear Optical measurements showed two optical band gaps of $\sim 3.2$eV and 5.3eV for SiO₂ nanoparticles, and band gap value of 4.15eV for GO nanosheets, which it reduces to 3.3eV after formation of the nanohybrid composite with GO: SiO₂ weight ratio of 2.0. The nonlinear optical properties of GO–SiO₂ with different weight ratio are measured using Z-scan technique. The results showed that the nonlinear refractive index of SiO₂ and GO nanoparticles and nanohybrid composite (0.5:1,1:1,2:1) ($\mathrm{\text{GO}}$–${\mathrm{\text{SiO}}}_2$) changed and has a negative sign. It was observed that the nonlinear refractive index changes in different ratios of compounds. Experimental results show that after the formation of the composite, the nonlinear refractive index shows a significant increase in the presence and effectiveness of the GO.

The paper discusses the synthesis and characterization of Cd${}_{1-x}$Mn${}_x$O nanoparticles using the precipitation method for potential optoelectronic applications. X-ray diffraction analysis revealed a cubic polycrystalline structure, with a decrease in crystallite size as Mn concentration increased. UV–Vis spectroscopy data showed changes in the band gap with varying Mn concentrations, with $E_g^{\mathrm{\text{opt.}}}$ decreasing from 2.523eV to 2.304eV as Mn content increased up to 3%. However, with further increases in Mn content, $E_g^{\mathrm{\text{opt.}}}$ increased to 2.332eV. The study also estimated various optical properties, providing valuable insights into the optical behavior of Cd${}_{1-x}$Mn${}_x$O nanoparticles. In addition to the aforementioned characterizations, the paper explores the influence of Mn content on dispersion parameters using Wemple Di-Domenico models. The dispersion energy ($E_d$) was found to increase from 13.502eV to 14.170eV, while the single oscillator energy ($E_o$) decreased from 3.483eV to 3.142eV with increasing Mn content. This suggests that the incorporation of Mn into CdO alters its optical properties significantly. Furthermore, the study calculated non-linear optical coefficients, such as the third-order non-linear susceptibility ($\chi$(3)) and non-linear refractive index ($n_2$), for CdO nanostructured powder doped with Mn. These findings indicate the potential suitability of Cd${}_{1-x}$Mn${}_x$O nanoparticles for applications in the fields of optics and electronic devices, highlighting their potential for use in advanced technologies requiring tailored optical properties and nonlinear behavior.

Recent intense interest in nanoparticle materials and nanoparticle-based contrast enhancement agents for biophysical applications gives new relevance to Mie scattering theory in its original context of application. The Mie theory still provides the most exact treatment of scattering from single nanoparticles of the noble metals. When recast in terms of modern electrodynamic formalism, the theory provides a concise closed-form representation for the scattered fields and also serves as a vehicle to elaborate the formal electrodynamic technique. The behavior of the Debye truncation condition for the multipole expansion is illustrated with numerical examples, clearly showing the features of the transition between the Rayleigh, dipole and higher order multipole approximations for the scattered fields. The classical Mie theory is an approximation in that only the transverse field components are included in the calculation. Extensions to the classical theory which include the effects of longitudinal fields are discussed and illustrated numerically. The example of scattering from multilayer composite particles is used to examine the feasibility of engineering spectral features of the scattering cross-section to target the requirements of specific applications.