An Analysis of the Optical Properties of Homogeneous Metal and Oxide Nanoparticles along with Double–Layer Nanoparticles with a Metal Core and an Oxide Shell Aimed at Improving the Efficiency of Absorption of Solar Radiation

Optics and Spectroscopy - Problems related to using nanoparticles for absorption of solar radiation and photothermal nanotechnologies are now being actively studied. The efficiency of using...     

Microwave-Assisted Synthesis of Core–Shell Nanoparticles—Insights into the Growth of Different Geometries

Microwave irradiation is utilized for the rapid synthesis of gold–silver core–shell bimetallic nanoparticles (NPs) in a two-step process. A strategy of establishing a bilayer organic barrier around the core using citrate and ascorbic acid as capping agents, providing a means to achieve a well-defined boundary layer between the core and the shell material, is reported. These boundary layers are essential for synthesizing different core–shell morphologies and the approach results in tunable bimetallic NPs with defined core–shell structures, both for spherical as well as for triangular seed cores. In addition, theoretical calculations of the plasmonic characteristics based on the boundary element method of different classes of NPs are conducted. These investigations enable conclusions to be drawn on the influence of the core morphology on the tunability of their localized surface plasmon resonances.     

Luminescent Properties of Activated Nanocomposites Based on Core–Shell Nanoparticles

Physics of the Solid State - Formulas for the rates of spontaneous radiative decay of excitation of luminescent centers located in subwavelength spherical core–shell nanoparticles and in the...     

Five-Level Structural Hierarchy: Microfluidically Supported Synthesis of Core–Shell Microparticles Containing Nested Set of Dispersed Metal and Polymer Micro and Nanoparticles

This study presents the development of a hierarchical design concept for the synthesis of multi-scale polymer particles with up to five levels of organization. The synthesis of core–shell microparticles containing nested sets of dispersed metal and polymer micro- and nanoparticles is achieved through in situ photopolymerization using a double co-axial capillaries microfluidic device. The flow rates of the carrier, shell, and core phases are optimized to control particle size and result in stable core–shell particles with well-dispersed three-level composites in the shell matrix. The robustness and reversibility of these core–shell particles are demonstrated through five cycles of drying and re-swelling, showing that the size and structure of core–shell particles remain unchanged. Additionally, the permeability and mobility of dye molecules within the shell matrix are tested and showed that different molecular weight dyes have different penetration times. This study highlights the potential of microfluidics as a powerful tool for the controlled and precise synthesis of complex structured materials and demonstrates the versatility and potential of these core–shell particles for sensing applications as particle-based surface-enhanced Raman scattering (SERS).     

Gaseous Metal and the Problem of Vapor–Liquid (Insulator–Metal) Transition in Metal Vapors

Journal of Experimental and Theoretical Physics - We consider the main properties of a gaseous metal, viz., the state of metal vapor adjoining the vapor–fluid transition binodal. The gaseous...     

Why the Magnetite–Gold Core–Shell Nanoparticles Are Not Quite Good and How to Improve Them

Physics of the Solid State - The nature of the formation of a chemical bond at the magnetite–gold interface has been studied. The geometric structure and the electronic and magnetic...     

Synthesis and Magnetic Properties of the Core–Shell Fe3O4/CoFe2O4 Nanoparticles

Physics of the Solid State - The Fe3O4/CoFe2O4 nanoparticles with a core–shell structure with an average size of 5 nm have been obtained by codeposition from the iron and cobalt chloride...     

Determination of Particle Size,Core and Shell Size Distributions of Core–Shell Particles by Analytical Ultracentrifugation

In core–shell nanoparticle analysis, the determination of size distributions of the different particle parts is often complicated, especially in liquid media. Density matching is introduced as a method for analyzing core–shell nanoparticles using Analytical Ultracentrifugation (AUC), making it possible to obtain the core size distribution in liquid dispersions. For this approach, the density of the dispersion is adjusted to the density of the shell. Oil filled nanocapsules are utilized with component densities of around 1 g mL⁻¹ to demonstrate this technique. The shell size distribution is calculated supposing the particle size distribution as a convolution of the shell- and core size distributions. Finally, the distributions of core size, shell thickness, particle size, and particle density and thus particle composition are obtained. To clarify the effect of swelling, AUC measurements are combined with further size characterization methods like Particle Tracking Microscopy and Dynamic Light Scattering.     

Multipole Excitation of Localized Plasmon Resonance in Asymmetrically Coated Core–Shell Nanoparticles Using Optical Vortices

Plasmonic interactions between an asymmetrically coated core–shell (ACCS) nanoparticle and an optical vortex produce a novel engagement of the spin angular momentum (SAM) and the orbital angular momentum (OAM) of the input. Simulations based on a discrete dipole approximation (DDA) indicate that the SAM and the OAM of the incident beam determine the modal order of resonance, correctly identifying the peak wavelength, and both the direction and magnitude of optical torque exerted upon the excited, localized plasmon resonance in the ACCS particle. These simulations also indicate higher-order resonances, including hexapole and octupole modes, and a zero-order resonance (expressible as a monopole mode), can be excited by judicious selection of the SAM and OAM. A detailed symmetry analysis shows how the multipoles associated with eigenmode excitations connect to the radiation multipoles at the heart of the multipole expansion. It is also shown how additional, distorted resonance modes due to the asymmetricity of the structure are also exhibited. These specific plasmonic characteristics, which cannot be realized by plane wave excitation, become possible through the ACCS asymmetry engaging with the distinct optical vortex nature of the excitation.     

Microdischarges Near Metal–Insulator Interfaces

Some statistical features of microdischarges running near the metal-insulator interfaces have been discussed. The study has verified an exponential character of statistical distributions of the time intervals between microdischarge pulses, power-law distribution of voltage peaks of these pulses (height of pulses) and very weak correlation effects among pulses, i.e. weak time-height correlation, time autocorrelation and height autocorrelation. A statistical parameter of the power law distribution of the heights of microdischarge pulses proved to be sensitive to the voltage load of the insulating interface metal-insulator.     

In Vitro Studies of Fe3O4-ZIF-8 Core–Shell Nanoparticles Designed as Potential Theragnostics

Theragnostics represent a combination of therapy and diagnosis within one system. Herein, Fe₃O₄-ZIF-8 core–shell nanoparticles are developed and suggested as candidates for theragnostic applications in cancer treatment. A drug loaded metal–organic framework ZIF-8 (zeolitic imidazolate framework-8) represents the therapeutic tool, while the Fe₃O₄ core is included to enable the material visualization by magnetic resonance imaging (MRI). A reliable synthesis of Fe₃O₄-ZIF-8 core–shell nanoparticles of an average size below 100 nm is reported. The nanoparticles are characterized by FT-IR, TGA, XRPD, TEM, STEM-EDS, DLS, ICP-OES, CHN-elemental analysis, SQUID measurements, and MRI. Moreover, their chemical stability and in vitro cytotoxicity against fibroblast and selected cancer cell lines are evaluated. As a model drug, arsenic trioxide—a promising anticancer drug—is used. The drug release can be triggered by a pH change from 7.4 to 6.0 and the nanoparticles can be visualized by MRI in vitro, thus a potential theragnostic agent for cancer treatment is developed.     

Synthesis and Characterization of CdS/CISe Quantum Dots with Core–Shell Structure

Quantum dots have received great interest due to their excellent optoelectronic properties. However, the surface defects of quantum dots affect the carrier transport and ultimately reduce the photovoltaic efficiency. In this paper, a core–shell quantum dot by hot-injection method is prepared to grow a narrow-band semiconductor layer (CuInSe₂ (CISe) quantumdot) on the surface of a broad-band core material (cadmium sulfide (CdS) nanocrystal). The composition, structure, optical properties, and decay lifetime of CdS/CISe core–shells are investigated in more detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), UV–vis spectrophotometry, and fluorescence spectroscopy. The CdS/CISe core–shell structure has a broadened absorption range and still shows CISe-related quantum effects. The increased size of the core–shell and the smaller specific surface area of the CISe shell layer lead to a lower carrier complexation chance, which improves the carrier lifetime.     

Temperature Dependence of Optical Properties of Two-Layered Metal–Dielectric Spherical Nanoparticles

Journal of Applied Spectroscopy - The dependences of the radiation absorption efficiency factors by spherical nanoparticles of a core–shell system of gold–quartz and quartz–gold...     

Systems of Vortices in a Binary Core–Shell Bose–Einstein Condensate

JETP Letters - A trapped Bose–Einstein-condensed mixture of two types of cold atoms with significantly different masses has been simulated numerically within the coupled...     

Effect of Confinement Strength on the Conversion Efficiency of Strained Core–Shell Quantum Dot Solar Cell

Optics and Spectroscopy - The conversion efficiency (CE) of core–shell quantum dot (CSQD) solar cell is investigated within weak and strong confinements strength, using detailed balance...     

Analysis of Thermodynamics of Liquid d— and f—Shell Metals with the Variational Approach

We use reently proposed potential to calculate internal energy (enthalpy), entropy and Helmholtz free energy of liquid d- and f-shell metals with the variational approach. The parameter of the potential is determined with the standard zero pressure condition along with well established Taylor screening function for exchange and correlation effects to the liquid d- and f-shell metals. Here we clearly mention that the parameter of the potential is independent of any fitting procedure either with any experimental data or any theoretical values of any physical properties. The structure factor derived by Percus-Yevick solution for hard sphere fluids, which is characterized by hard sphere diameter, is used. A good agreement between theoretical investigations and experimental findings has confirmed the ability of the model potential to the liquid d- and f-shell metals.     

Rigidity of Interfaces in the Falicov–Kimball Model

We analyze the thermodynamic properties of interfaces in the three-dimensional Falicov–Kimball model, which can be viewed as a primitive quantum lattice model of crystalline matter. In the strong coupling limit, the ionic subsystem of this model is governed by the Hamiltonian of an effective classical spin model whose leading part is the Ising Hamiltonian. We prove that the 100 interface in this model, at half-filling, is rigid, as in the three-dimensional Ising model. However, despite the above similarities with the Ising model, the thermodynamic properties of its 111 interface are very different. We prove that even though this interface is expected to be unstable for the Ising model, it is stable for the Falicov–Kimball model at sufficiently low temperatures. This rigidity results from a phenomenon of ground-state selection and is a consequence of the Fermi statistics of the electrons in the model.     

Recurrence Spectra of the Rydberg Hydrogen Atom near Two Parallel Metal Surfaces

Using closed orbit theory, we study the influence of the two parallel metal surfaces on the recurrence spectra of a hydrogen atom placed in the region between the two surfaces. The results show that the metal surfaces have significant effect on the photoabsorption process. Each resonance peak in the recurrence spectra is associated with one electronic closed orbit. In our work, we put the first metal surface at the critical value dc and vary the second metal surface. The results show that when the distances between the hydrogen atom and the two metal surfaces are close to the critical valuedc, the number of the closed orbits is the greatest and there are more peaks in the recurrence spectra. When the distance between the atom and the second metal surface is larger or smaller than dc, the number of the closed orbits decreases and there are fewer peaks in the recurrence spectra. The agreement between the semiclassical calculation spectra and the quantum calculation spectra suggests that our analysis is correct.