Oxide Core Shell Nanoparticles Research Articles

Mesoporous Ag@WO3 core–shell, an investigation at different concentrated environment employing laser ablation in liquid

In this study, silver-tungsten oxide core–shell nanoparticles (Ag–WO3 NPs) were synthesized by pulsed laser ablation in liquid employing a (1.06 µm) Q-switched Nd:YAG laser, at different Ag colloidal concentration environment (different core concentration). The produced Ag–WO3 core–shell NPs were subjected to characterization using UV–visible spectrophotometry, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive spectroscopy, electrical analysis, and photoluminescence PL. The UV–visible spectra exhibited distinct absorption peaks at around 200 and 405 nm, which attributed to the occurrence of surface Plasmon resonance of Ag NPs and WO3 NPs, respectively. The absorbance values of the Ag–WO3 core–shell NPs increased as the core concentrations rose, while the band gap decreased by 2.73–2.5 eV, The (PL) results exhibited prominent peaks with a central wavelength of 456, 458, 458, 464, and 466 nm. Additionally, the PL intensity of the Ag–WO3-NP samples increased proportionally with the concentration of the core. Furthermore, the redshift seen at the peak of the PL emission band may be attributed to the quantum confinement effect. EDX analysis can verify the creation process of the Ag–WO3 core–shell nanostructure. XRD analysis confirms the presence of Ag and WO3 (NPs). The TEM images provided a good visualization of the core-spherical shell structure of the Ag–WO3 core–shell NPs. The average size of the particles ranged from 30.5 to 89 (nm). The electrical characteristics showed an increase in electrical conductivity from (5.89 × 10−4) (Ω cm)−1 to (9.91 × 10−4) (Ω cm)−1, with a drop in average activation energy values of (0.155 eV) and (0.084 eV) at a concentration of 1.6 μg/mL of silver.

Property Tuning through Fine Size Control and Hierarchical Nanostructuring of Metal Oxide Nanoparticles Supported in Porous Matrices: a Review

In the nanoscale, matter presents different properties compared to its bulk counterparts, owing to the considerable increase of the surface/bulk ratio, as well as the occurrence of quantum confinement effects. One method to fine control the growth of nanoparticles, their size and nanostructure is to use metalorganic deposition combined with a porous matrix as host, where pores act as nanoreactors for nanoparticle growth, resulting in chemically integrated systems. In this review, we look at the history and achievements of the chemical method of impregnation-decomposition cycles for the precise size control, property tuning and tailored synthesis of metal oxide nanoparticles. We give an overview of the various oxide nanoparticles and nanomaterials developed over the years, and how the method of impregnation-decomposition cycles allowed the synthesis of pure, doped and core-shell oxide nanoparticles, as well as the tuning of their properties through the combined fine control of nanoparticle size, nanostructure, and composition.

Interband- and Intraband-Induced Hot Electron Transfer in Plasmonic Gold–Cerium Oxide Core–Shell Nanoparticles

Interband- and Intraband-Induced Hot Electron Transfer in Plasmonic Gold–Cerium Oxide Core–Shell Nanoparticles

On the tribological behavior of cobalt-based nanocomposite coatings containing ZnO@Graphene oxide core-shell nanoparticles

A hybrid nanocrystalline cobalt-based coating was prepared by cathode plasma electrolytic deposition (CPED). Zinc oxide and graphene oxide (GO) nanoparticles were mixed to form a core-shell structure through electrostatic self-assembly by using (3-aminopropyl)triethoxysilane (APTES) modifier. ZnO@GO nanoparticles were used as additives to improve wear and friction properties of deposited coatings. The concentration effect of core-shell ZnO@GO addition (0.1, 0.2 and 0.3 %wt) on the friction, wear, coating thickness and mechanical properties was investigated. The composition and microstructure of deposited coatings were studied by scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy and energy dispersive spectroscopy (EDS). Reciprocating sliding wear tests using a ball-on-plate configuration were carried out on a PLINT TE67 tribometer. AISI 52100 steel was used as ball and the coating deposited onto a AISI 304 stainless steel substrate was used as plate. Coatings were dense, nanocrystalline and uniform with a FCC metastable cobalt structure. Core-shell concentration above to 0.2 %wt resulted in a decrease of grain size and an increase of hardness and wear resistances. Nanoparticles act as nucleation sites for grain formation, decreasing grain sizes. Samples using 0.3% ZnO@GO displayed the lowest wear and friction coefficients. ZnO@GO nanoparticles enables the formation of a protective layer consisting of oxide and exfoliated GO on the top of worn surfaces.

Magnetic Coupling in Cobalt-Doped Iron Oxide Core–Shell Nanoparticles: Exchange Pinning through Epitaxial Alignment

Tuning the core–shell morphology of bimagnetic nanoparticles and its associated exchange bias behavior is a promising way to overcome the superparamagnetic limit and stabilize the particle moment in extended time and temperature ranges. The intraparticle magnetization distribution and magnetic coupling between the two phases, however, is still unclear. We report a significant nonzero magnetization in the CoxFe(1–x)O core of native core–shell bimagnetic nanoparticles that is typically considered antiferro- or paramagnetic. Co0.14Fe0.86O@Co0.4Fe2.4O4 (6 nm@2 nm) and Co0.08Fe0.92O@Co0.58Fe2.28O4 (12 nm@2 nm) core–shell nanoparticles have been synthesized by thermal decomposition of a mixed cobalt–iron oleate with a similar Fe/Co distribution throughout the nanoparticle. We determine the exact phase composition and the magnetization distribution in the core and shell using a combination of X-ray and neutron small-angle scattering. Core and shell magnetization are traced separately with a varying magnetic field. Our results reveal that the magnetization of the core and the spinel-type shell phases are coupled at room temperature, i.e., rotating coherently with the magnetic field. This is a mandatory condition to observe a significant exchange bias effect at low temperatures. These findings highlight the enormous potential of finite size and exchange coupling in bimagnetic nanoparticles to control the magnetic properties via interface-induced magnetization.

Development of a General and Selective Nanostructured Cobalt Catalyst for the Hydrogenation of Benzofurans, Indoles and Benzothiophenes

AbstractThe selective hydrogenation of benzofurans in the presence of a heterogeneous non‐noble metal catalyst is reported. The developed optimal catalytic material consists of cobalt‐cobalt oxide core–shell nanoparticles supported on silica, which has been prepared by the immobilization and pyrolysis of cobalt‐DABCO‐citric acid complex on silica under argon at 800 °C. This novel catalyst allows for the selective hydrogenation of simple and functionalized benzofurans to 2,3‐dihydrobenzofurans as well as related heterocycles. The versatility of the reported protocol is showcased by the reduction of selected drugs and deuteration of heterocycles. Further, the stability, recycling, and reusability of the Co‐nanocatalyst are demonstrated.

Development of a general and selective nanostructured cobalt catalyst for the hydrogenation of benzofurans, indoles and benzothiophenes.

The first selective hydrogenation of benzofurans in the presence of a heterogeneous non-noble metal catalyst is reported. The developed optimal catalytic material consists of cobalt-cobalt oxide core-shell nanoparticles supported on silica, which has been prepared by the immobilization and pyrolysis of cobalt-DABCO-citric acid complex on silica under argon at 800 °C. This novel catalyst allows for the selective hydrogenation of simple and functionalized benzofurans to 2,3-dihydrobenzofurans as well as related heterocycles. The versatility of the reported protocol is showcased by the reduction of selected drugs and deuteration of heterocycles. Further, the stability, recycling, and reusability of the Co-nanocatalyst are demonstrated.

The effect of size, shape, coating and functionalization on nuclear relaxation properties in iron oxide core-shell nanoparticles: a brief review of the situation.

In this perspective article, we present a short selection of some of the most significant case studies on magnetic nanoparticles for potential applications in nanomedicine, mainly magnetic resonance. For almost 10 years, our research activity focused on the comprehension of the physical mechanisms on the basis of the nuclear relaxation of magnetic nanoparticles in the presence of magnetic fields; taking advantage of the insights gathered over this time span, we report on the dependence of the relaxation behaviour on the chemico-physical properties of magnetic nanoparticles and discuss them in full detail. In particular, a critical review is carried out on the correlations between their efficiency as contrast agents in magnetic resonance imaging and the magnetic core of magnetic nanoparticles (mainly iron oxides), their size and shape, and the coating and solvent used for making them biocompatible and well dispersible in physiological media. Finally, the heuristic model proposed by Roch and coworkers is presented, as it was extensively adopted to describe most of the experimental data sets. The large amount of data analyzed allowed us to highlight both the advantages and limitations of the model.

Interaction and mechanisms in the phosphate–binding of iron(oxyhydr)oxide core–shell nanoparticles

HypothesisThe high binding affinity of iron(oxyhydr)oxides for phosphate has recently been used in medicine to treat hyperphosphatemia, an abnormally elevated phosphate concentration in the blood. For iron(oxyhydr)oxide nanoparticles, the composition of the organic shell has a more significant influence on their interaction with phosphate than is often assumed. This study shows different mechanisms in phosphate binding, using the example of two similar new phosphate-binding agents. ExperimentsWe characterized the phosphate-binding behavior of two iron(oxyhydr)oxide-based nanomaterials with similar composition and particle properties and investigated their binding mechanisms by spectroscopic methods. FindingsFor the often prescribed Velphoro, we demonstrated a phosphate binding capacity of>210 mg/g. A similar active ingredient named C–PAM binds over 573 mg/g. Spectroscopic measurements highlighted differences in the binding mechanism. While Velphoro binds phosphate via surface complexation independent of pH and adsorbent concentration, C–PAM shows a strong concentration dependence. At low concentrations, phosphate is bound via complexation reactions. The iron(oxyhydr)oxide structure was dissolved at higher phosphate concentrations and formed various iron phosphate species. The substances behave differently upon interaction with phosphate, although being very similar in composition and crystal structure. Thus, we demonstrated a crucial influence of the ligands in the shell on the binding mechanism.

Overcoming Hypoxia-Induced Ferroptosis Resistance via a 19 F/1 H-MRI Traceable Core-Shell Nanostructure.

Lipid peroxides accumulation induced ferroptosis is an effective cell death pathway for cancer therapy. However, the hypoxic condition of tumor microenvironment significantly suppresses the efficacy of ferroptosis. Here, we design a novel nanoplatform to overcome hypoxia-induced ferroptosis resistance. Specifically, we synthesize a novel kind of perfluorocarbon (PFOB)@manganese oxide (MnOx) core-shell nanoparticles (PM-CS NPs). Owing to the good carrier of O2 as fuel, PM-CS NPs can induce higher level of ROS generation, lipid peroxidation and GSH depletion, as well as lower activity of GPX4, compared with MnOx NPs alone. Moreover, the supplement of O2 can relieve tumor hypoxia to break down the storage of intracellular lipid droplets and increase expression of ACSL4 (a symbol for ferroptosis sensitivity). Furthermore, upon stimulus of GSH or acidity, PM-CS NPs exhibit the "turn on" 19 F-MRI signal and activatable T1 /T2 -MRI contrast for correlating with the release of Mn. Finally, PM-CS NPs exert high cancer inhibition rate for ferroptosis based therapy via synergetic combination of O2 -mediated enhancement of key pathways of ferroptosis.

Dielectric relaxation of α-Fe2O3/Gd2O3 core-shell nanoparticle obtained through the polyol method

The design of core-shell nanostructures is a potential approach to obtaining advanced dielectric nanocomposites. The frequency-dependent dielectric dispersion of gadolinium oxide (Gd2O3) encapsulated iron oxide (Fe2O3) core-shell nanoparticles (Fe2O3/Gd2O3 CSNPs) synthesized by the polyol route is investigated in the temperature range from 303 K to 553 K and in the frequency range from 42 Hz to 1.1 MHz. The phase formation of the materials is evaluated by X-ray diffraction analysis. Synthesized Fe2O3/Gd2O3 CSNPs have multi-core nature are found by Transmission electron microscopy (TEM). Relaxation time corresponding to dielectric loss is found to obey Arrhenius law with an activation energy of 0.26 eV. Dielectric relaxation is analyzed in the electric modulus formalism. The frequency-dependent conductivity spectra follow the Jonscher power law.

Inducing Ectopic T Cell Clusters Using Stromal Vascular Fraction Spheroid-Based Immunotherapy to Enhance Anti-Tumor Immunity.

Tertiary lymphoid structures (TLSs) provide specialized niches for immune cells, resulting in improved prognoses for patients undergoing cancer immunotherapy. Shaping TLS‐like niches may improve anti‐cancer immunity and overcome the current limitations of immune cell‐based immunotherapy. Here, it is shown that stromal vascular fraction (SVF) from adipose tissues can enhance dendritic cell (DC)‐mediated T cell immunity by inducing ectopic T lymphocyte clusters. SVF cells expanded ex vivo have phenotypes and functions similar to those of fibroblastic reticular cells in a secondary lymphoid organ, and their properties can be modulated using three‐dimensional spheroid culture and coculture with DCs spiked with antigen‐loaded iron oxide–zinc oxide core‐shell nanoparticles. Thereby, the combination of SVF spheroids and mature DCs significantly augments T cell recruitment and retention at the injection site. This strategy elicits enhanced antigen‐specific immune response and anti‐tumoral immunity in mice, illustrating the potential for a novel immunotherapeutic design using SVF as a structural scaffold for TLS.

Synthesis of Liquid Gallium@Reduced Graphene Oxide Core-Shell Nanoparticles with Enhanced Photoacoustic and Photothermal Performance.

This report presents nanoparticles composed of a liquid gallium core with a reduced graphene oxide (RGO) shell (Ga@RGO) of tunable thickness. The particles are produced by a simple, one-pot nanoprobe sonication method. The high near-infrared absorption of RGO results in a photothermal energy conversion of light to heat of 42.4%. This efficient photothermal conversion, combined with the large intrinsic thermal expansion coefficient of liquid gallium, allows the particles to be used for photoacoustic imaging, that is, conversion of light into vibrations that are useful for imaging. The Ga@RGO results in fivefold and twofold enhancement in photoacoustic signals compared with bare gallium nanoparticles and gold nanorods (a commonly used photoacoustic contrast agent), respectively. A theoretical model further reveals the intrinsic factors that affect the photothermal and photoacoustic performance of Ga@RGO. These core-shell Ga@RGO nanoparticles not only can serve as photoacoustic imaging contrast agents but also pave a new way to rationally design liquid metal-based nanomaterials with specific multi-functionality for biomedical applications.

Retraction of "Predictions of Drug-Protein Interactions and Study of Magnetically Assisted Release Dynamics of 5-Fluorouracil from Soya Protein-Coated Iron Oxide Core-Shell Nanoparticles".

Retraction of "Predictions of Drug-Protein Interactions and Study of Magnetically Assisted Release Dynamics of 5-Fluorouracil from Soya Protein-Coated Iron Oxide Core-Shell Nanoparticles".

Enhanced Li-ion diffusion and electrochemical performance in strained-manganese-iron oxide core-shell nanoparticles.

Efforts to improve energy storage depend greatly on the development of efficient electrode materials. Recently, strain has been employed as an alternate approach to improve ion mobility. While lattice strain has been well-researched in catalytic applications, its effects on electrochemical energy storage are largely limited to computational studies due to complexities associated with strain control in nanomaterials as well as loss of strain due to the phase change of the active material during charging-discharging. In this work, we overcome these challenges and investigate the effects of strain on supercapacitor performance in Li-ion-based energy devices. We synthesize epitaxial Fe3O4@MnFe2O4 (core@shell) nanoparticles with varying shell thickness to control the lattice strain. A narrow voltage window for electrochemical testing is used to limit the storage mechanism to lithiation-delithiation, preventing a phase change and maintaining structural strain. Cyclic voltammetry reveals a pseudocapacitive behavior and similar levels of surface charge storage in both strained- and unstrained-MnFe2O4 samples; however, diffusive charge storage in the strained sample is twice as high as the unstrained sample. The strained-MnFe2O4 electrode exceeds the performance of the unstrained-MnFe2O4 electrode in energy density by ∼33%, power density by ∼28%, and specific capacitance by ∼48%. Density functional theory shows lower formation energies for Li-intercalation and lower activation barrier for Li-diffusion in strained-MnFe2O4, corresponding to a threefold increase in the diffusion coefficient. The enhanced Li-ion diffusion rate in the strained-electrodes is further confirmed using the galvanostatic intermittent titration technique. This work provides a starting pointto using strain engineering as a novel approach for designing high performance energy storage devices.

Ru/Nb co-doped perovskite anode: Achieving good coking resistance in hydrocarbon fuels via core-shell nanocatalysts exsolution

Ru/Nb co-doped (Pr0.5Sr0.5)0.9Fe0.8Ru0.1Nb0.1O3-δ (PSFRN) cubic perovskite oxide was fabricated and used as the solid oxide fuel cell (SOFC) anode material. After treated in wet H2 at 900 °C for 2 h, the PSFRN was partially transformed into Ruddlesden-Popper (RP) layered perovskite PrSrFe0.8Ru0.1Nb0.1O4+δ (RP-PSFRN), and Fe0.7Ru0.3 alloy-FeOx oxide (FRA@FO) core-shell nanoparticles were in-situ exsolved on the reduced-PSFRN (R-PSFRN) substrate surface. The phase transition and the exsolution of the nanoparticles were investigated using X-ray diffraction, transmission electron microscope and X-ray photoelectron spectroscopy. Modified by the in-situ exsolved FRA@FO core-shell nanoparticles, the R-PSFRN anode material showed high catalytic activity for hydrogen and hydrocarbon fuels. The power density of SOFC reached 0.683 and 0.537 W cm−2 with wet H2 and C3H8 as fuel at 800 °C, respectively. Moreover, the SOFC showed a stable output under a constant current load of 0.15 A cm−2 in C3H8, demonstrating a high resistance to carbon deposition and coking.

A comprehensive study of synthesis and applications of core/shell nanoparticles

When we consider matter at nanoscale, one of the most important aspects to be considered is that due to the small size of the particles, these have increased surface area to volume ratio. The large value of this ratio increases the dominance of the surface atoms of the nanoparticles in relation to those in its interior. A special category of materials at nanoscale level has gained popularity in the recent times due to their interesting properties and applications. When classified on the basis of structure, the types of core/shell particles can have a large variety. Each of this structural classification has its own importance, method of synthesis and application. The core/shell nanoparticles have some distinct features that is responsible for their importance. The properties of Core/shell nanoparticles are highly modified from that of their simple pure nanomaterials, thus they usually called highly functional materials. The introduction of a different crust layer over the core particle has many reasons, such as it helps in implementing surface modification, increases functionality, stability and dispersibility, control on the release of the core, lowering the consumption of precious materials, and so on. These nanostructures can have a number of combinations in close interaction, depending upon the selection of material used, which highly influences the end application. This paper has an overview of the present methods involved in synthesis and tunable factors responsible for their end applications. The development of metal/metal oxide core-shell nanoparticles has become popular nowadays due to their widespread use in catalysis and other environmental remedial applications.

Charge transfer channels of silver @ cuprous oxide heterostructure core-shell nanoparticles strengthen high photocatalytic antibacterial activity

Marine biological fouling has always been a hot research topic. In this study, silver @ cuprous oxide (Ag@Cu2O) core-shell nanoparticles were synthesized via in-situ synthesis method and developed an outstanding antibacterial activity. The bacteriostasis efficiency of Ag@Cu2O reached to 99% and 98% against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. The minimum inhibitory concentration of Ag@Cu2O decreased from 113.6 μg/mL to 56.8 μg/mL compared with Cu2O. Ag@Cu2O had better antibacterial activity than Cu2O with lower content of Cu2O and was more environment friendly. The heterostructure formed at the interface between Ag and Cu2O promoted the separation and diffusion of photogenerated electron-hole pairs through the charge transfer channel and promoted the generation of reactive oxygen species. The outstanding antibacterial activity of Ag@Cu2O was strongly depended on the generation of the reactive oxygen species. Density functional theory and finite element method calculations demonstrated that the structure of core-shell improved photocatalytic efficiency. Additionally, synergetic effect of released Ag+ and Cu2+ also enhanced the bacteriostasis rate and the long-term antifouling performance in 60 days. Hence, the synthesized core-shell Ag@Cu2O can be applied as novel antifoulants in the marine field.

Efficient Dye Degradation via Catalytic Persulfate Activation using Iron Oxide-Manganese Oxide Core-Shell Particle Doped with Transition Metal Ions

Organic-pollutants released into water bodies pose serious concerns because of its detrimental effects in aquatic biota, environment and economy. Water remediation using persulfate based advanced oxidation process is one of the emerging techniques. In this study, we have developed iron oxide-manganese oxide core–shell nanoparticles doped with transition metal ions for the efficient degradation of bromophenol blue dye, for the first time. Here, the transition metal ion doped MnOx shell enables efficient persulfate activation while the magnetic core facilitate in the effective recovery of used particles. The synthesized particles were characterized by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and vibrating sample magnetometer. The presence of dopants is found to significantly change the ratio of Mn3+ to Mn4+, reactivity and mobility of lattice oxygen in doped samples. Silver ion doped MnOx showed the highest dye degradation efficiency of ~91% with 1.8 wt% nanoparticles, due to the enhanced reactivity and mobility of lattice oxygen activity of the core–shell nanoparticle in presence of Ag ions in persulfate activation. From the experimental results, the mechanism of activation of persulfate by nanoparticles is elucidated. Our findings provide a new platform for efficient water remediation using dual functional core shell magnetic nanoparticles.

Mechanical and curing behavior of epoxy composites reinforced with polystyrene-graphene oxide (PS-GO) core-shell particles

Epoxy is a high performance yet brittle thermosetting resin. To deem epoxy fit for aircraft applications, its mechanical properties, especially fracture toughness, must be improved. In this work, epoxy resin was reinforced with 0.1, 0.5 and 1.0 wt.% polystyrene-graphene oxide (PS-GO) core-shell nano-particles to enhance its fracture toughness. Styrene monomer (oil phase) was polymerized in situ using aqueous GO dispersion (water phase) to obtain PS-GO core-shell nano-particles, which appeared as wrinkled spheres under the electron microscope, confirming that the PS particles were wrapped by the GO sheets. The effect of PS-GO and GO on the curing of epoxy resin was studied and compared. The fracture tests of the cured composites revealed 28% and 26% improvements in the fracture toughness (KIC) and fracture energy (GIC) values for the 1.0 wt.% PS-GO epoxy composite, respectively. Toughening in the composites majorly occurred due to filler debonding accompanied by void formation, crack deflection and blunting and strong filler matrix interaction. The compressive strength and strain at failure improved by 25% and 52% for the 0.1 wt.% PS-GO epoxy composite, respectively. Dynamic mechanical analysis (DMA) revealed that epoxy's stiffness improved slightly after PS-GO addition while the Tg remained almost constant. Finally, the FTIR analysis of cured epoxy composites in agreement with the curing studies ascertained that, irrespective of the filler loading, the amount of hardener used was adequate to achieve complete curing of the epoxy.