Gold Shell Research Articles

Numerical investigation of the refractive index sensitivity of Au/Ag core-shell nanostructures for sensing applications

The plasmonic properties of bimetallic (gold and silver) core-shell nanostructures were studied numerically by using the boundary element method implemented in MATLAB (MNPBEM toolbox). The dependence of the bulk refractive index sensitivity of the nanostructures on the core/shell thicknesses was investigated, and regions of enhanced sensitivities were identified for both Ag@Au and Au@Ag type of nanostructures. For Ag@Au nanoparticles, utilizing a 14 ± 2 nm silver core radius with 4 ± 2 nm gold shell thickness or a 22 ± 2 nm core radius with 6 ± 1 nm shell thickness can yield a 1.2–2.5× increase in sensitivity compared to a purely silver nanosphere with the same size. For Au@Ag structures, 20 ± 3 nm gold core size with 10 ± 3 nm silver shell thickness was found to be optimal, with sensitivity enhancements between 2 and 5× compared to pure gold nanoparticles with the same size. The increased sensitivity can always be attributed to the hybridization of the plasmon absorbance peaks corresponding to the silver and gold parts, which merging comes with increased peak width (and thus decreased figure of merit) as a tradeoff. The provided sensitivity maps can be helpful for the design and fabrication of plasmonic sensors utilizing core-shell nanostructures.

Dark Field and Coherent Anti-Stokes Raman (DF-CARS) Imaging of Cell Uptake of Core-Shell, Magnetic-Plasmonic Nanoparticles.

Magnetic-plasmonic, Fe3O4-Au, core-shell nanoparticles are popular in many applications, most notably in therapeutics and diagnostics, and thus, the imaging of these nanostructures in biological samples is of high importance. These nanostructures are typically imaged in biological material by dark field scatter imaging, which requires an even distribution of nanostructures in the sample and, therefore, high nanoparticle doses, potentially leading to toxicology issues. Herein, we explore the nonlinear optical properties of magnetic nanoparticles coated with various thicknesses of gold using the open aperture z-scan technique to determine the nonlinear optical properties and moreover, predict the efficacy of the nanostructures in nonlinear imaging. We find that the magnetic nanoparticles coated with gold nanoseeds and thinner gold shells (ca. 4 nm) show the largest nonlinear absorption coefficient β and imaginary part of the third-order susceptibility Im χ(3), suggesting that these nanostructures would be suitable contrast agents. Next, we combine laser dark field microscopy and epi-detected coherent anti-Stokes Raman (CARS) microscopy to image the uptake of magnetic-plasmonic nanoparticles in human pancreatic cancer cells. We show the epi-detected CARS technique is suitable for imaging of the magnetic-plasmonic nanoparticles without requiring a dense distribution of nanoparticles. This technique achieves superior nanoparticle contrasting over both epi-detected backscatter imaging and transmission dark field imaging, while also attaining label-free chemical contrasting of the cell. Lastly, we show the high biocompatibility of the Fe3O4 nanoparticles with ca. 4-nm thick Au shell at concentrations of 10–100 µg/mL.

Molecular Imaging of Infarcted Heart by Biofunctionalized Gold Nanoshells.

The unique combination of physical and optical properties of silica (core)/gold (shell) nanoparticles (gold nanoshells) makes them especially suitable for biomedicine. Gold nanoshells are used from high-resolution in vivo imaging to in vivo photothermal tumor treatment. Furthermore, their large scattering cross-section in the second biological window (1000-1700 nm) makes them also especially adequate for molecular optical coherence tomography (OCT). In this work, it is demonstrated that, after suitable functionalization, gold nanoshells in combination with clinical OCT systems are capable of imaging damage in the myocardium following an infarct. Since both inflammation and apoptosis are two of the main mechanisms underlying myocardial damage after ischemia, such damage imaging is achieved by endowing gold nanoshells with selective affinity for the inflammatory marker intercellular adhesion molecule 1 (ICAM-1), and the apoptotic marker phosphatidylserine. The results here presented constitute a first step toward a fast, safe, and accurate diagnosis of damaged tissue within infarcted hearts at the molecular level by means of the highly sensitive OCT interferometric technique.

Sharp Spectral Variations of the Ultrafast Transient Light Extinction by Bimetallic Nanoparticles in the Near‐UV

AbstractNoble metal nanoparticles exhibit localized plasmon resonance modes that span the visible and near‐infrared spectral ranges and have many applications. Modifying the size, shape, and composition of the nanoparticles changes the number of modes and their properties. The characteristics of these modes are transiently affected when illuminating the nano‐objects with ultrashort laser pulses. Here, core–shell gold–silver nanocuboids are synthesized and their spectral signature in the stationary and ultrafast transient regimes are measured. Their dipolar transverse mode vanishes with increasing Ag‐shell thickness, while higher‐order modes grow in the near‐ultraviolet range where no plasmon resonance can be generated with single noble metal nanoparticles. These higher‐energy modes are associated with sharp spectral variations of the ultrafast transient light extinction by the bimetallic nanocuboids. By carrying out a theoretical investigation, the different contributions to this response are broken down and a physical interpretation of its spectral profile is provided. The transient optical signal is then shown to reveal resonance modes hidden in the stationary regime spectra.

Structural control and biomedical applications of plasmonic hollow gold nanospheres: A mini review.

Hollow gold nanospheres (HGNs) are core/shell structures with a dielectric material core, usually composed of solvent, and a gold metal shell. Such structures have two metal/dielectric interfaces to allow interaction between the gold metal with the interior and external dielectric environment. Upon illumination by light, HGNs exhibit unique surface plasmon resonance (SPR) properties compared to solid gold nanoparticles. Their SPR absorption/scattering can be tuned by changing their diameter, shell thicknesses, and surface morphologies. In addition to the low toxicity, easy functionalization, resistance to photobleaching, and sensitivity to changes in surrounding medium of gold, the enhanced surface-to-volume ratio and tunable SPR of HGNs make them highly attractive for different applications in the fields of sensing, therapy, and theranostics. In this article, we review recent progress on the synthesis and structural control of HGNs and applications of their SPR properties in biomedical sensing and theranostics. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > in vitro Nanoparticle-Based Sensing Diagnostic Tools > in vivo Nanodiagnostics and Imaging.

Core–Shell Gold Nanoparticle-Star Copolymer Composites with Gradient Transfer and Transport Properties: Toward Electro-Optical Sensors and Catalysis

A series of hybrid core–shell nanomaterials was prepared by solvent phase transfer methods with gold (Au) nanoparticles (NPs) as a core and star copolymers (h-PEI-b-PCL-Cbz) as a shell—consisting o...

Preparation of Vanillic Acid-Loaded Core-Shell Gold Nanospheres/Mesoporous Silica Nanoparticles for the Treatment of Orthopedic Infection.

Orthopedic infection is a serious complication in surgeries and remains a great challenge in clinics. Here, the natural antimicrobial compound vanillic acid-loaded gold nanospheres/mesoporous silica nanoparticles (VA@Au-MSNs) were fabricated for chemo-photothermal synergistic therapy to orthopedic infections. The shape and morphology of Au-MSN and VA@Au-MSN were observed by scanning electron microscopy and transmission electron microscopy. The properties of VA@Au-MSN or related components were characterized by dynamic light scattering, thermogravimetric analysis, Brunauer–Emmett–Teller (BET) analysis, and photothermal analysis. Vanillic acid released from VA@Au-MSN was detected in phosphate-buffered saline. A cytotoxicity test and an antibacterial assessment were performed to explore the biosafety and antibacterial activity of VA@Au-MSN, respectively. The results showed that Au-MSN possessed a high BET surface area (458 m2/g). After loading vanillic acid, the BET surface area reduced to 72 m2/g. The loading efficiency of Au-MSN was 18.56%. Under 808 nm laser irradiation, the temperature at the wound site injected with the Au-MSN solution in the mouse increased from 24 to 60 °C within about 12 s. Also, the high temperature could promote the release of vanillic acid from VA@Au-MSN. Additionally, VA@Au-MSN has no obvious cytotoxicity to MC3T3-E1 cells, but the generated local hyperthermia and the VA released from VA@Au-MSN had excellent antibacterial activity against Staphylococcus aureus in a synergistic way. In conclusion, the VA@Au-MSN with biosafety and excellent antibacterial performance might be applied for the treatment of orthopedic infection.

Nanosecond pulse laser-induced fabrication of gold and silver-integrated cinnamon shell structure: Tunable fluorescence dynamics and morphology

Various bio-compatible nanostructures with strong fluorescence and tailored physiochemical properties are desirable for the biomedicine and bioelectronics applications. Based on this fact, we prepared some gold/silver-integrated cinnamon shell structure (SS) using the nanosecond pulselaser ablation in liquid (PLAL) method and characterized systematically. The structure, morphology, color purity, absorption and fluorescence properties of these SS were tuned via the laser parameters variation to determine their practical applications feasibility. The HRTEM images of the produced SS showed the nucleation of the face centered cubic nanocrystallites with growth orientation along (111) and (200) lattice planes. The XRD and thermogravimetric analysis of the as-prepared samples confirmed their crystalline nature and thermal stability, respectively. The EDX spectra and maps of the studied SS revealed their corresponding atomic compositions and distributions. The FTIR and Raman spectra displayed the existence of bimolecular residues within the SS.These plasmonic SS demonstrated very strong UV–Vis absorbance, high fluorescence quantum yield (0.055) and blue emission color purity (CCT and CIE coordinate of 2454.93 K and 0.164, 0.1033) at room temperature. The lifetime decay analyses showed significant decrease of the donor in the presence of the luminescent SS (6.5 ± 5.46 ns), attributing to the interplay of radiative energy transfer andsubsequent emission of the photons at longer wavelengthin theSS. It is established that the PLAL fabricated SS may be useful for the antimicrobial drugs formulation and biophotonic applications.

Potential of a sonochemical approach to generate MRI-PPT theranostic agents for breast cancer.

The production of nanomaterials integrating diagnostic and therapeutic roles within one nanoplatform is important for medical applications. Such theranostics nanoplatforms could provide information on imaging, accurate diagnosis and, at the same time, could eradicate cancer cells. Fe3O4@Au core@shell nanoparticles (Fe3O4@AuNPs) have gained broad attention due to their unique innovations in magnetic resonance imaging (MRI) and photothermal therapy (PTT). Seed-mediated growth procedures were used to produce the Fe3O4@AuNPs. In these processes, complicated surface modifications, resulted in unsatisfactory properties. This work used the ability of the sonochemical approach to synthesize highly efficient theranostics agent Fe3O4@AuNPs with a size of approximately 22 nm in 5 min. The inner core of Fe3O4 acts as an MRI agent, whereas the photothermal effect stands accomplished by near-infrared absorption of the gold shell (Au shell), which results in the eradication of cancer cells. We have shown that Fe3O4@AuNPs have great biocompatibility and no major cytotoxicity has been identified. Relaxivity value (r2) of synthesized Fe3O4@Au NPs, measured at 233 mM-1s-1, is significantly higher than those reported previously. The as-synthesized NPs have shown substantial photothermal ablation ability on MCF-7 in vitro under near-infrared laser irradiation. Consequently, Fe3O4@AuNPs synthesized in this study have great potential as an ideal candidate for MR imaging and PTT.

Почему наночастицы магнетит/золото со структурой ядро-оболочка недостаточно хороши и как их улучшить

In this paper a short review of experimental and theoretical recent researches of magnetic core-shell nanoparticles with noble metals shell is given. Magnetic nanoparticles of Fe3O4 coated with a gold shell are in demand in many biomedical applications. However, there are practically no good nanoparticles completely and uniformly coated with gold. In this paper, we investigated the formation of a chemical bond at the magnetite/gold interface. In the framework of DFT-GGA calculations, the geometric structure, electronic and magnetic properties of flat layers consisting of Fe3O4 magnetite, titanium, and gold are studied. It is established that the specific energy and wetting parameters of the magnetite-gold interface are negative, while these values of the magnetite-titanium (for thin Ti layers) and magnetite-titanium-gold boundaries are positive. This allows us to hope that an intermediate thin layer of titanium at the boundary between the surface of the magnetite nanoparticle and the gold layer will stabilize this three-layer structure and allow obtaining magnetite nanoparticles coated with a solid gold coating.

Catalytically active and thermally stable core-shell gold-silica nanorods for CO oxidation.

Deactivation based on sintering phenomena is one of the most costly issues for the industrial application of metal nanoparticle catalysts. To address this drawback, mesoporous silica encapsulation is reported as a promising strategy to stabilize metallic nanoparticles towards use in high temperature catalytic applications. These protective shells provide significant structural support to the nanoparticles, while the mesoporosity allows for efficient transport of the reactants to the catalytically active surface of the metallic nanoparticle in the core. Here, we extend the use of gold nanorods with mesoporous silica shells by investigating their stability in the CO oxidation reaction as an example of high temperature gas phase catalysis. Gold nanorods were chosen as the model system due to the availability of a simple, high yield synthesis method for both the metallic nanorods and the mesoporous silica shells. We demonstrate the catalytic activity of gold nanorods with mesoporous silica shells at temperatures up to 350 °C over several cycles, as well as the thermal stability up to 500 °C, and compare these results to surfactant-stabilized gold nanorods of similar size, which degrade, and lose most of their catalytic activity, before reaching 150 °C. These results show that the gold nanorods protected by the mesoporous silica shells have a significantly higher thermal stability than surfactant-stabilized gold nanorods and that the mesoporous silica shell allows for stable catalytic activity with little degradation at high temperatures.

Fabrication of Bovine Serum Albumin@Au Particles for Colorimetric Detection of Glutathione.

Abnormal concentrations of glutathione (GSH) are important indicators of many human diseases such as cancers, liver damage, AIDS, and Alzheimer's disease. In this work, a kind of bovine serum albumin (BSA)@Au core-shell particles were fabricated using 110 nm BSA aggregates as a template, onto which gold shells composed of Au nanoparticles (NPs) were grown through a seeded growth approach. The morphology of the Au shells deposited on BSA aggregates was tuned from sparse to dense distribution of Au NPs by increasing the concentration of silver ions contained in the growth solutions. Surface plasmon resonance (SPR) peaks of BSA@Au particles were tunable in the range from 550 to 620 nm, corresponding to evolution in color from red to blue due to the enhanced plasmonic coupling among the Au NPs in the shell. The blue BSA@Au particles were qualified for colorimetric detection of GSH since GSH may act as a swelling agent for BSA@Au particles by breaking the intermolecular disulfide bonds in BSA aggregates. With an increased amount of GSH presented, the color of BSA@Au particles evolved from blue to red attributed to gradual swelling of BSA@Au particles and thus increased the distance among the Au NPs in the shell, which was readily recognized by naked eyes or recorded by ultraviolet-visible (UV-vis) spectroscopy. This colorimetric method exhibited good selectivity and anti-interference capability in the analysis of GSH in real samples. In addition, a solid sensing system for the detection of GSH was designed and fabricated by dispersing BSA@Au particles into an agarose hydrogel.

The Effects of a Varied Gold Shell Thickness on Iron Oxide Nanoparticle Cores in Magnetic Manipulation, T1 and T2 MRI Contrasting, and Magnetic Hyperthermia.

Fe3O4–Au core–shell magnetic-plasmonic nanoparticles are expected to combine both magnetic and light responsivity into a single nanosystem, facilitating combined optical and magnetic-based nanotheranostic (therapeutic and diagnostic) applications, for example, photothermal therapy in conjunction with magnetic resonance imaging (MRI) imaging. To date, the effects of a plasmonic gold shell on an iron oxide nanoparticle core in magnetic-based applications remains largely unexplored. For this study, we quantified the efficacy of magnetic iron oxide cores with various gold shell thicknesses in a number of popular magnetic-based nanotheranostic applications; these included magnetic sorting and targeting (quantifying magnetic manipulability and magnetophoresis), MRI contrasting (quantifying benchtop nuclear magnetic resonance (NMR)-based T1 and T2 relaxivity), and magnetic hyperthermia therapy (quantifying alternating magnetic-field heating). We observed a general decrease in magnetic response and efficacy with an increase of the gold shell thickness, and herein we discuss possible reasons for this reduction. The magnetophoresis speed of iron oxide nanoparticles coated with the thickest gold shell tested here (ca. 42 nm) was only ca. 1% of the non-coated bare magnetic nanoparticle, demonstrating reduced magnetic manipulability. The T1 relaxivity, r1, of the thick gold-shelled magnetic particle was ca. 22% of the purely magnetic counterpart, whereas the T2 relaxivity, r2, was 42%, indicating a reduced MRI contrasting. Lastly, the magnetic hyperthermia heating efficiency (intrinsic loss power parameter) was reduced to ca. 14% for the thickest gold shell. For all applications, the efficiency decayed exponentially with increased gold shell thickness; therefore, if the primary application of the nanostructure is magnetic-based, this work suggests that it is preferable to use a thinner gold shell or higher levels of stimuli to compensate for losses associated with the addition of the gold shell. Moreover, as thinner gold shells have better magnetic properties, have previously demonstrated superior optical properties, and are more economical than thick gold shells, it can be said that “less is more”.

Her2-Targeted Multifunctional Nano-Theranostic Platform Mediates Tumor Microenvironment Remodeling and Immune Activation for Breast Cancer Treatment.

PurposeThe treatment of breast cancer is often ineffective due to the protection of the tumor microenvironment and the low immunogenicity of tumor cells, leading to a poor therapeutic effect. In this study, we designed a nano-theranostic platform for these obstacles: a photothermal effect mediated by a gold shell could remodel the tumor microenvironment by decreasing cancer-associated fibroblasts (CAFs) and promote the release of doxorubicin (DOX) from nanoparticles. In addition, it could realize photoacoustic (PA)/MRI dual-model imaging for diagnose breast cancer and targeted identification of Her2-positive breast cancer.MethodsHer2-DOX-superparamagnetic iron oxide nanoparticles (SPIOs)@Poly (D, L-lactide-co-glycolide) acid (PLGA)@Au nanoparticles (Her2-DSG NPs) were prepared based on a single emulsion oil-in-water (O/W) solvent evaporation method, gold seed growing method, and carbon diimide method. The size distribution, morphology, PA/MRI imaging, drug loading capacity, and drug release were investigated. Cytotoxicity, antitumor effect, cellular uptake, immunogenic cell death (ICD) effect, and targeted performance on human Her2-positive BT474 cell line were investigated in vitro. BT474/Adr cells were constructed and the antitumor effect of NPs on it was evaluated in vitro. Moreover, chemical-photothermal therapy effect, PA/MRI dual-model imaging, ICD effect induced by NPs, and tumor microenvironment remodeling in human BT474 breast cancer nude mice model were also investigated.ResultsNanoparticles were spherical, uniform in size and covered with a gold shell. NPs had a photothermal effect, and can realize photothermal-controlled drug release in vitro. Chemical-photothermal therapy had a good antitumor effect on BT474/Adr cells and on BT474 cells in vitro. The targeting evaluation in vitro showed that Her2-DSG NPs could actively target and identify Her2-positive tumor cells. The PA/MRI imaging was successfully validated in vitro/vivo. Similarly, NPs could enhance the ICD effect in vitro/vivo, which could activate an immune response. Immunofluorescence results also proved that photothermal effect could decrease CAFs to remodel the tumor microenvironment and enhance the accessibility of NPs to tumor cells. According to the toxicity results, targeted drug delivery combined with photothermal-responsive drug release proved that NPs had good biosafety in vivo. Chemical-photothermal therapy of Her2-targeted NPs has a good antitumor effect in the BT474 nude mice model.ConclusionOur study showed that chemical-photothermal therapy combined with tumor microenvironment remodeling and immune activation based on the Her2-DSG NPs we developed are very promising for Her2-positive breast cancer.

Nanostructured and Spiky Gold Shell Growth on Magnetic Particles for SERS Applications.

Multifunctional micro- and nanoparticles have potential uses in advanced detection methods, such as the combined separation and detection of biomolecules. Combining multiple tasks is possible but requires the specific tailoring of these particles during synthesis or further functionalization. Here, we synthesized nanostructured gold shells on magnetic particle cores and demonstrated the use of them in surface-enhanced Raman scattering (SERS). To grow the gold shells, gold seeds were bound to silica-coated iron oxide aggregate particles. We explored different functional groups on the surface to achieve different interactions with gold seeds. Then, we used an aqueous cetyltrimethylammonium bromide (CTAB)-based strategy to grow the seeds into spikes. We investigated the influence of the surface chemistry on seed attachment and on further growth of spikes. We also explored different experimental conditions to achieve either spiky or bumpy plasmonic structures on the particles. We demonstrated that the particles showed SERS enhancement of a model Raman probe molecule, 2-mercaptopyrimidine, on the order of 104. We also investigated the impact of gold shell morphology—spiky or bumpy—on SERS enhancements and on particle stability over time. We found that spiky shells lead to greater enhancements, however their high aspect ratio structures are less stable and morphological changes occur more quickly than observed with bumpy shells.

Light scattering and plasmonic response of Au–Fe3O4 nanoparticles

Surface plasmon (SP) response of nanoparticles (NP) has an unique path in the field of sensing, with specific developments in instrumentation and having a wide range of applications. Here it is described the light scattering process of NPs formed by magnetite core and gold shell (Au– $$\hbox {Fe}_{3}\hbox {O}_{4}$$ ). Those were synthesized by the co-precipitation method, resulting in a quasi-spherical (icosahedral) shape of an average of 37.5 nm. It was found a plasmonic behaviour from UV-visible spectra, exhibiting a SP peak around 560 nm, this response is strongly dependent on NP size and shape. To describe its plasmonic response, it was employed the Rayleigh scattering and Mie theory for a metal-dielectric shell-core. The numerical solutions of these models confirms the SP response and that there is a correlation between the size and shape of NPs due to scattering of light from them.

Synthesis and optimization of the sonochemical method for functionalizing gold shell on Fe3O4 core nanoparticles using response surface methodology

This study reports the synthesis and optimization of the sonochemical method for the functionalization of iron oxide nanoparticles (Fe3O4NPs) with gold nanoparticles (AuNPs) shells using the surface response methodology (RSM). The Au shell is coated on Fe3O4 NPs using a Vibra-Cell ultrasonic solid horn with tip size, frequency and power output of ½ inch, 20 kHz and 750 w, respectively within 8 min. Using RSM, experimental runs of 14 different combinations of HAuCl4 concentration, sodium citrate (SC) concentration, and sonication amplitude (independent variables) were performed with two centered points to optimize the experimental conditions. Variance analysis (ANOVA) was applied to achieve the best optimum conditions for the experimental data. The targeted zeta potential of –46.125 mV was achieved under the optimum conditions of 10 ml of HAuCl4, 30 ml of SC and sonication amplitude of 40%, which is consistent (about 99.2%) with the actual average zeta potential (–45.8 mV). The stability and monodispersion of Fe3O4NPs improved following modification to Fe3O4@Au, as indicated by the increase in zeta potential from –24.2 mV to –45.8 mV. The saturation magnetization (Ms) value of Fe3O4 was 54 emu/g, while that of Fe3O4@Au NP is 38 emu/g. In general, the sonochemical method effectively synthesizes highly stable and monodisperse Fe3O4@Au NPs with an average size of about 20 nm within 8 min.

Interfacial Control of the Synthesis of Cellulose Nanocrystal Gold Nanoshells.

Cellulose nanocrystal (CNC) gold nanoshell was prepared using a polymer-coated CNC as a template. A seed-mediated shell growth approach (ex situ) was employed, gold nanoparticles (AuNPs) of two sizes were prepared, and the effect of the size of AuNP on the shell quality (smoothness, evenness, and continuity) was elucidated. Additionally, a novel one-pot synthesis approach (in situ) was evaluated for the preparation of the gold nanoshell, where polymer-coated CNCs with adsorbed ascorbic acid were used to reduce Au ions to form a metallic gold shell on CNC. The surface coverage was manipulated by adding different amounts of plating solutions. The formation and morphology of gold nanoshells were evaluated by zeta potential measurements, dynamic light scattering, UV-vis spectroscopy, and transmission electron microscopy (TEM). The catalytic performance of the CNC-gold nanostructures for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was governed by the surface area of gold shells.

Synthesis and Characterization of Core–Shell Magnetic Nanoparticles NiFe2O4@Au

In this study, NiFe2O4@Au core–shell nanoparticles were prepared by the direct reduction of gold on the magnetic surface using amino acid methionine as a reducer and a stabilizing agent simultaneously. The obtained nanoparticles after three steps of gold deposition had an average size of about 120 nm. The analysis of particles was performed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis spectroscopy techniques. The results indicate successful synthesis of core–shell particles with the magnetic core, which consists of a few agglomerated nickel ferrite crystals with an average size 25.2 ± 2.0 nm, and the thick gold shell consists of fused Au0 nanoparticles (NPs). Magnetic properties of the obtained nanoparticles were examined with magnetic circular dichroism. It was shown that the magnetic behavior of NiFe2O4@Au NPs is typical for superparamagnetic NPs and corresponds to that for NiFe2O4 NPs without a gold shell. The results indicate the successful synthesis of core–shell particles with the magnetic nickel ferrite core and thick gold shell, and open the potential for the application of the investigated hybrid nanoparticles in hyperthermia, targeted drug delivery, magnetic resonance imaging, or cell separation. The developed synthesis strategy can be extended to other metal ferrites and iron oxides.

MXene core-shell nanostructures with enhanced conductivity and stability

MXene, a novel two-dimensional material, can be used in a broad range of photoelectricity applications, such as electrooptic modulators, photodetectors and ironic batteries, and the conductivity and stability of MXene are both critical in these applications. However, The enhanced properties can be achieved via MXene modification, such as inserted irons into the interlayer of MXene, or formed complex materials by taking advantage of the active group on the surface of MXene. In this work, a core-shell nanostructure composed of Ti3C2 (MXene) and gold nanoparticles was obtained with a simple and controllable method, and the increase in conductivity and stability were both investigated. The optical measurement results suggested that the photoelectric interaction between the gold nanoparticles and Ti3C2 materials was fully utilized when assembled together in a core-shell nanostructure. Additionally, the electric measurement results showed that the resistance of the Ti3C2 material was distinctly reduced after the formation of the [email protected] core-shell nanostructure, with the maximum 20% decrease in resistance being achieved when the core-shell nanostructures were around 107 nm with gold shell of 7 nm, excited by a voltage of 2 V. In addition, compared with the pure Ti3C2 materials, the [email protected] core-shell nanostructures showed good long-term stability due to the antioxidation effect of the gold shell nanostructure. Therefore, this study paves the way toward the use of MXene-based materials in optoelectrical applications.