Surfaces and Interfaces of Liquid Metal Core–Shell Nanoparticles under the Microscope

Eutectic gallium indium (EGaIn), a Ga-based liquid metal alloy holds great promise for designing next-generation core–shell nanoparticles (CSNs). A shearing-assisted ligand-stabilization method has shown promise as a synthetic method for these CSNs; however, determining the role of the ligand on stabilization demands an understanding of the surface chemistry of the ligand–nanoparticle interface. EGaIn CSNs are created and functionalized with aliphatic carboxylates of different chain length, allowing a fundamental investigation on ligand stabilization of EGaIn CSNs. Raman and diffuse reflectance Fourier transform spectroscopies (DRIFTS) confirm reaction of the ligand with the oxide shell of the EGaIn nanoparticles. Changing the length of the alkyl chain in the aliphatic carboxylates (C2–C18) may influence the size and structural stability of EGaIn CSNs, which is easily monitored using atomic force microscopy (AFM). No matter how large the carboxylate ligand, there is no obvious effect on the size of the EGaIn CSNs, except the particle size getting more uniform when coated with longer chain carboxylates. The AFM force–distance measurements are used to measure the stiffness of the carboxylate-coated EGaIn CSNs. In corroboration with DRIFTS analysis, the stiffness studies show that the alkyl chains undergo conformational changes upon compression.     

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...     

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...     

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...     

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.     

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).     

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.     

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.     

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.     

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...     

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...     

Synthesis and Stabilization of Fe–Nd–B Nanoparticles for Biomedical Applications

Stable composition of Iron Neodymium Boron nanoparticles are formed by a chemical method. Conventional borohydride reduction method was used. The particles are in the size range of 30–100 nm. Silica coating was applied to stabilize and prepare the particles for in vitro applications such as cell separation and diagnostics. Morphology of particles has been studied along with the structure and magnetic properties.     

Influence of Some Parameters on the Synthesis of ZrO2 Nanoparticles by Heating of Alcohol–aqueous Salt Solutions

Parameters that influence ZrO₂ (3-mol% Y₂O₃ stabilized) nanoparticles prepared by heating of alcohol–aqueous salt solutions were investigated. It revealed that the kind of alcohol used significantly affected the particle size and morphology of the as synthesized nano-ZrO₂ powders. The ratio of alcohol to water (R/H) was also important to conduct the gelation process. The dispersion and sintering behavior of the powder could be optimized via aging. By carefully controlling the process, weakly agglomerated ZrO₂ nanoparticles with an average particle size of 13-nm (TEM) were achieved. The classical DLVO theory was employed to clarify the effect of solvent on powder morphology, an aging mechanism was proposed as well.     

Insights into copper coordination in the EcoRI–DNA complex by ESR spectroscopy

The EcoRI restriction endonuclease requires one divalent metal ion in each of two symmetrical and identical catalytic sites to catalyse double-strand DNA cleavage. Recently, we showed that Cu²⁺ binds outside the catalytic sites to a pair of new sites at H114 in each sub-unit, and inhibits Mg²⁺-catalysed DNA cleavage. In order to provide more detailed structural information on this new metal ion binding site, we performed W-band (～94 GHz) and X-band (～9.5 GHz) electron spin resonance spectroscopic measurements on the EcoRI–DNA–(Cu²⁺)₂ complex. Cu²⁺ binding results in two distinct components with different g_zz and A_zz values. X-band electron spin echo envelope modulation results indicate that both components arise from a Cu²⁺ coordinated to histidine. This observation is further confirmed by the hyperfine sub-level correlation results. W-band electron nuclear double resonance spectra provide evidence for equatorial coordination of water molecules to the Cu²⁺ ions.     

Optical Properties of Core–Shell Fe3O4/CdSe/ZnS Nanocomposites

Optics and Spectroscopy - The luminescent and magnetooptical properties of nanocomposites consisting of a superparamagnetic Fe3O4 core coated with a luminescent CdSe semiconductor layer, which, in...     

Effect of Carbon Source with Different Graphitization Degrees on the Synthesis of Diamond

Using three kinds of graphites with different graphitization degrees as carbon source and Fe-Ni alloy powder as catalyst, the synthesis of diamond crystals is performed in a cubic anvil high-pressure and high-temperature apparatus （SPD-6 × 1200）. Diamond crystals with perfect hexoctahedron shape are successfully synthesized at pressure from 5.0 to 5.5GPa and at temperature from 1570 to 1770K. The synthetic conditions, nucleation, morphology, inclusion and granularity of diamond crystals are studied. The temperature and pressure increase with the increase of the graphitization degree of graphite. The quantity of nucleation and granularity ofdiamonds decreases with the increase of graphitization degree of graphite under the same synthesis conditions. Moreover, according to the results of the M6ssbauer spectrum, the composition of inclusions is mainly Fe3 C and Fe-Ni alloy phases in diamond crystals synthesized with three kinds of graphites.     

Synthesis, Characterization and Magnetic Property Measurements of Zn1－xMnxO Nanoparticles via Vapour Phase Growth

Nanosized Mn-doped ZnO particles were synthesized using a vapour phase growth method. The x-ray analysis revea/s a wurtzite ZnO structure with small expansion of the lattice constants due to the doping of Mn in ZnO. The TEM analysis shows that the nanoparticles have an average diameter around 37 nm, and energy dispersive spectroscopy detection on single nanoparticle indicates that the manganese concentration is around 3.5at.%. Magnetization measurements under field cooling conditions reveal that the as-grown Mn-doped ZnO nanoparticles show paramagnetic behaviour. This work demonstrates that Mn can be doped into nanosized ZnO structures via vapour phase growth, which represents an important step towards the synthesis of nanosized diluted magnetic semiconductors.