Shell Nanocomposites Research Articles

Preparation of multi‐walled carbon nanotubes/SiO 2 core–shell nanocomposites by a two‐step Stöber process

The surface modification and functionalisation of multi-walled carbon nanotubes (MWNTs) could provide enhanced properties to MWNTs for highly specific applications which often require solubilisation and dispersion, promotion of functionality, biocompatibility or lower toxicity of MWNTs. Herein, a novel nanocomposite consisting of MWNTs as a core and amorphous silica (SiO2) as a shell is developed. First, the functionalisation of MWNTs with carboxylic functional group (MWNTs-COOH) was obtained via oxidation using the concentrated sulphuric acid/nitric acid mixture (3:1 v/v) treatment. Second, a silica uniform layer was grown on MWNTs-COOH by a two-step Stober process. The core–shell nanostructure is characterised by Fourier-transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, and energy dispersive spectrometer. Experimental results show that a SiO2 shell was uniformly coated on the surface of MWNTs with a thickness of 5–10 nm. The results can have important implications for the preparation of carbon nanotube core–shell nanocomposites in general.

Enhanced photoluminescence of Fe3O4@Y2O3:Eu3+ bifunctional nanoparticles by the Gd3+ co-doping

In this paper, the Gd3+ codoped bifunctional coreshell nanoparticles, Fe3O4@(Y1-xGdx)2O3:Eu3+, were synthesized through a Urea Homogeneous Preci-pitation method. The microstructure, luminescence, and magnetic properties of the codoped samples were investigated and discussed with the help of various analytic techniques including X-ray diffraction, scanning electron microscope, photo-luminescence spectra, cathodelumincence mapping and vibrating sample magnetometer. The co-doped sample (x = 0.3), emitting at 612 nm dominantly under the 254 nm excitation, exhibited the photoluminescence intensity 2.7 times higher than the undoped one (x = 0), due to the efficient energy transfer between Gd3+ and Eu3+. The Fe3O4@(Y1-xGdx)2O3:Eu3+ core–shell nanoparticles were spherical and uniform, and had a particle size of about 180 nm in diameter. They also showed a saturation magnetization of 1.09 emu/g, a coercivity of 20 Oe and a remanence of 0.01emu/g. The enhanced photoluminescence and good magnetic properties of the title core–shell nanocomposites allow them to be used in biomedical applications.

HER2 Targeted Breast Cancer Therapy with Switchable “Off/On” Multifunctional “Smart” Magnetic Polymer Core–Shell Nanocomposites

Multifunctional magnetic polymer nanocombinations are gaining importance in cancer nanotheranostics due to their safety and their potential in delivering targeted functions. Herein, we report a novel multifunctional core-shell magnetic polymer therapeutic nanocomposites (NCs) exhibiting pH dependent "Off-On" release of drug against breast cancer cells. The NCs are intact in blood circulation ("Off" state), i.e., at physiological pH, whereas activated ("On" state) at intracellular acidic pH environment of the targeted breast cancer cells. The NCs are prepared by coating the cannonball (iron nanocore) with hydrophobic nanopockets of pH-responsive poly(d,l-lactic-co-glycolic acid) (PLGA) polymer nanoshell that allows efficient loading of therapeutics. Further, the nanocore-polymer shell is stabilized by poly(vinylpyrrolidone) (PVP) and functionalized with a targeting HER2 ligand. The prepared Her-Fe3O4@PLGA-PVP nanocomposites facilitate packing of anticancer drug (Tamoxifen) without premature release in the bloodstream, recognizing the target cells through binding of Herceptin antibody to HER2, a cell surface receptor expressed by breast cancer cells to promote HER2 receptor mediated endocytosis and finally releasing the drug at the intracellular site of tumor cells ("On" state) to induce apoptosis. The therapeutic efficiency of hemo/cytocompatible NCs drug delivery system (DDS) in terms of targeted delivery and sustained release of therapeutic agent against breast cancer cells was substantiated by in vitro and in vivo studies. The multifunctional properties of Her-Tam-Fe3O4@PLGA-PVP NCs may open up new avenues in cancer therapy through overcoming the limitations of conventional cancer therapy.

Core–Shell Nanocomposites Based on Gold Nanoparticle@Zinc–Iron-Embedded Porous Carbons Derived from Metal–Organic Frameworks as Efficient Dual Catalysts for Oxygen Reduction and Hydrogen Evolution Reactions

Core–shell nanocomposites based on Au nanoparticle@zinc–iron-embedded porous carbons (Au@Zn–Fe–C) derived from metal–organic frameworks were prepared as bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). A single Au nanoparticle of 50–100 nm in diameter was encapsulated within a porous carbon shell embedded with Zn–Fe compounds. The resulting Au@Zn–Fe–C hybrids exhibited apparent catalytic activity for ORR in 0.1 M KOH (with an onset potential of +0.94 V vs RHE, excellent stability and methanol tolerance) and for HER as well, which was evidenced by a low onset potential of −0.08 V vs RHE and a stable current density of 10 mA cm–2 at only −0.123 V vs RHE in 0.5 M H2SO4. The encapsulated Au nanoparticles played an important role in determining the electrocatalytic activity for ORR and HER by promoting electron transfer to the zinc–iron-embedded porous carbon layer, and the electrocatalytic activity was found to vary with both the loading of the gold...

One-step synthesis of magnetite core/zirconia shell nanocomposite for high efficiency removal of phosphate from water

A self-assembled magnetite core/zirconia shell (Fe3O4@ZrO2) nanoparticle material was fabricated by the one-step co-precipitation method to capture phosphate from water. Fe3O4@ZrO2 with different Fe/Zr molar ratios were obtained and characterized by XRD, TEM, BET surface area and magnetization. It was shown that, with the decreasing of Fe/Zr molar ratio, magnetization decreased whereas surface area and adsorption capacity of phosphate increased. Fe3O4@ZrO2 with the ratio of higher than 4:1 had satisfactory magnetization property (>23.65emu/g), enabling rapid magnetic separation from water and recycle of the spent adsorbent. The Langmuir adsorption capacity of Fe3O4@ZrO2 reached 27.93–69.44mg/g, and the adsorption was fast (90% of phosphate removal within 20min). The adsorption decreases with increasing pH, and higher ionic strength caused slight increase in adsorption at pH>about 5.5. The presence of chloride, nitrate and sulfate anions did not bring about significant changes in adsorption. As a result, Fe3O4@ZrO2 performed well to remove phosphate from real wastewater. These results were interpreted by the ligand exchange mechanism, i.e., the direct coordination of phosphate onto zirconium by replacement of hydroxyl groups. Results suggested that phosphate reacted mainly with surface hydroxyl groups but diffusion into interior of zirconia phase also contributed to adsorption. The adsorbed phosphate could be desorbed with a NaOH treatment and the regenerated Fe3O4@ZrO2 could be repeatedly used.

Evidence on the presence of Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction in CoFe2O4@Au nano structure

In this work, a straight forward method for preparing CoFe2O4/Au core shell nano composite is introduced. By this method, samples with different thickness of Au as shell were obtained. The crystal and micro structures of the prepared samples were studied using x-ray diffraction and TEM micrographs. The presence of plasmonic frequencies of gold nano particles was investigated by measuring absorbance spectra in the visible range. It was found that, the plasma frequency decreases with increasing the gold thickness. The effect of the gold thickness on the magnetization, nucleation field and magnetic loss were studied. The experimental measurements showed an oscillating behavior of the magnetic parameters with increasing gold thickness. These results could be explained in terms of the presence of Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction between the ferromagnetic components via the conduction electrons of the gold metal. The heating ability of the magnetic Co-Ferrite particles under high frequency magnetic field was enhanced by the presence of the gold as a shell.

Fabrication of Graphene and AuNP Core Polyaniline Shell Nanocomposites as Multifunctional Theranostic Platforms for SERS Real-time Monitoring and Chemo-photothermal Therapy.

In this work, novel theranostic platforms based on graphene oxide and AuNP core polyaniline shell (GO-Au@PANI) nanocomposites are fabricated for simultaneous SERS imaging and chemo-photothermal therapy. PANI, a new NIR photothermal therapy agent with strong NIR absorption, outstanding stability and low cytotoxicity is decorated on AuNPs by one-pot oxidative polymerization, then the Au@PANI core-shell nanoparticles are attached to the graphene oxide (GO) sheet via π-π stacking and electrostatic interaction. The obtained GO-Au@PANI nanohybirds exhibit excellent NIR photothermal transduction efficiency and ultrahigh drug-loading capacity. The nanocomposites can also serve as novel NIR SERS probes utilizing the intense SERS signals of PANI. Rapid SERS imaging of cancer cells is achieved using this ultrasensitive nanoprobe. GO-Au@PANI also reveals good capability of drug delivery with the DOX-loading efficiency of 189.2% and sensitive NIR/pH-responsive DOX release. The intracellular real-time drug release dynamics from the nanocomposites is monitored by SERS-fluorescence dual mode imaging. Finally, chemo-photothermal ablation of cancer cells is carried out in vitro and in vivo using GO-Au@PANI as high-performance chemo-photothermal therapeutic nanoagent. The theranostic applications of GO-Au@PANI endow it with great potential for personalized and precise cancer medicine.

Structure evolution of Prussian blue analogues to CoFe@C core–shell nanocomposites with good microwave absorbing performances

Novel uniform CoFe@C core–shell composite nanoparticles with good distribution have been fabricated through the combined self-assembly and controlled thermal decomposition of Co-based Prussian blue (PB) nanocubes..

Supported polymer magnets with high catalytic performance in the green reduction of nitroaromatic compounds

We exhibit the synthesis of magnetic core–shell nanocomposites as solid phase catalysts in the reduction of nitroaromatics.

A waxberry-like SiO2@MnSiO3 core–shell nanocomposite synthesized via a simple solvothermal self-template method and its potential in catalytic degradation and heavy metal ion removal

A novel waxberry-like SiO2@MnSiO3 core–shell nanocomposite was facilely fabricated via the simple one-step thermal treatment of SiO2 nanospheres, MnCl2·4H2O, ethylenediamine (EDA), and ethylene glycol (EG).

Development of a Fe3O4@SnO2:Er3+,Yb3+–APTES nanocarrier for microwave-triggered controllable drug release, and the study of the loading and release mechanisms using microcalorimetry

New multifunctional core–shell nanocomposites were synthesized and applied as an efficient microwave sensitive nanocarrier for on-command drug release.

Iron(ii)-triazole core-shell nanocomposites: toward multistep spin crossover materials.

The first SCO@SCO core-shell nanomaterials have been synthesized by the step-by-step microemulsion method. The observed gyroscopic core-shell nanocomposites exhibit three-step spin crossover behaviour with thermal hysteresis at around room temperature. This offers an efficient and novel strategy for the development of multistable SCO materials.

Ultrahigh performance supercapacitors utilizing core-shell nanoarchitectures from a metal-organic framework-derived nanoporous carbon and a conducting polymer.

Hitherto, many reports on composite materials for electrochemical applications are based on one-dimensional carbon nanotubes or two-dimensional graphene materials. However, these composite materials usually suffer from a stacking problem during electrochemical cycling. A smart nanoarchitectural design is needed for composite materials in order to overcome this problem. Recent research on electrochemical energy storage (EES) applications has focused on the development of three-dimensional (3-D) core-shell structures. The basis for high performance electrochemical energy storage is to control the efficient intercalation of ions in such a 3-D structure. Here, we demonstrate controlled synergy between the physicochemical properties of nanoporous carbon and conducting polyaniline polymer (carbon-PANI), which leads to some new interesting electrochemical properties. The time-dependent controlled optimization of the core-shell nanocomposites consisting of nanoporous carbon with a thin layer of PANI nanorod arrays gives useful control over supercapacitor performance. Furthermore, these carbon-PANI nanocomposites can electrochemically access ions with remarkable efficiency to achieve a capacitance value in the range of 300-1100 F g-1. When assembled in a two electrode cell configuration, the symmetric supercapacitor (SSC) based on carbon-PANI//carbon-PANI shows the highest specific energy of 21 W h kg-1 and the highest specific power of 12 kW kg-1. More interestingly, the SSC shows capacitance retention of 86% after 20 000 cycles, which is highly superior compared to previous research reports.

Tungsten carbide/porous carbon core–shell nanocomposites as a catalyst support for methanol oxidation

The Pt–WC@C demonstrates higher electrochemical activity, which could be attributed to the better dispersed Pt on WC which leads to the improved synergistic effect between WC and Pt.

Carbon Coated Metal Nanoparticles for Electrocatalysis

To promote the performance of nanoparticle electrocatalysts, a facile hydrothermal method is developed to generate core–shell nanocomposites with a metal catalyst core and a carbon shell. In this method, glucose serves as the reducing agent and carbon precursor while cetyltrimethylammonium surfactants serve as both pore structure-directing agents and nanoparticle capping agent. The accessibility of the metal catalyst core was examined by gas-phase ethylene hydrogenation and the electrocatalytic activity was tested by formic acid oxidation (FOR). The selection of halide counter ions used during the synthesis was found to be critical. The optimized sample of Pd-carbon nanocomposite exhibits a FOR current density of 2.55 mA/cm2, which is higher than that of un-coated Pd nanoparticles with no support (0.89 mA/cm2) and with carbon nanotube support (1.08 mA/cm2).

Design of Core-Pd/Shell-Ag Nanocomposite Catalyst for Selective Semihydrogenation of Alkynes

We designed core-Pd/shell-Ag nanocomposite catalyst (Pd@Ag) for highly selective semihydrogenation of alkynes. The construction of the core–shell nanocomposite enables a significant improvement in the low activity of Ag NPs for the selective semihydrogenation of alkynes because hydrogen is supplied from the core-Pd NPs to the shell-Ag NPs in a synergistic manner. Simultaneously, coating the core-Pd NPs with shell-Ag NPs results in efficient suppression of overhydrogenation of alkenes by the Pd NPs. This complementary action of core-Pd and shell-Ag provides high chemoselectivity toward a wide range of alkenes with high Z-selectivity under mild reaction conditions (room temperature and 1 atm H2). Moreover, Pd@Ag can be easily separated from the reaction mixture and is reusable without loss of catalytic activity or selectivity.

In-situ assembly of biocompatible core–shell hierarchical nanostructures sensitized immunosensor for microcystin-LR detection

Microcystin-LR (MC-LR) is a kind of hepatotoxin which can cause functional and structural disturbances of the liver, accumulate in aquatic organisms and transfer to higher trophic levels, a biocompatible electrochemical immunosensor was constructed to detect MC-LR sensitively and selectively. The three-dimensional villiform-like carbon nanotube/cobalt silicate (CNT@Co silicate) core–shell nanocomposites were synthesized and firstly used as the substrate to immobilize the antigen of MC-LR (Ag), while Fe3O4 nanoclusters/polydopamine/gold nanoparticles (Fe3O4@PDA–Au) core–shell magnetic nanocomposites were prepared as the label carrier of the immunosensor to conjugate the second antibody (Ab2) and horse radish peroxidase (HRP). Since the toxicity of nanomaterials is important in the construction of biosensors including the immobilization of antigen or antibody, the biocompatibility of such nanocomposites were investigated by monitoring the cell viability after culturing with Hela cells. Due to the excellent biocompatibility, the immunosensor can immobilize more antigens by the large surface area of the three-dimensional villiform-like structure in CNT@Co silicate, and provide high electrochemical signals by Fe3O4@PDA–Au labeled Ab2 and HRP. After investigation of the binding capability of biomolecules on nanomaterials and optimization of the conditions in the competitive immunoassay, the proposed electrochemical immunosensor shows a linear response to MC-LR in the range from 0.005μg/L to 50μg/L with a detection limit of 0.004μg/L. In addition, the specificity, reproducibility and stability of the immunosensor were also proved to be acceptable, indicating its potential application in environmental monitoring.

Single-Step Synthesis of SiO2–TiO2 Hydrophobic Core–Shell Nanocomposite by Hydrothermal Method

The objective of this work is the synthesis and characterization of an appropriate hydrophobic nanoparticle as a collector for flotation of hematit in Gol-E-Gohar Iron Mine Iran. In this investigation, SiO2–TiO2 nanocomposites have been successfully synthesized by hydrothermal process. The morphology, structure, and composition of the as-synthesized nanostructures have been investigated by scanning electron microscopy and transmission electron microscopy. The ability of SiO2–TiO2 nanocomposite to facilitate the froth flotation of pyrite was correlated to the hydrophobicity of the nanoparticles. Furthermore, the efficiency of the mineral flotation process was evaluated in terms of final recovery and grade of S in Gol-e Gohar Iron Ore Complex, Sirjan, Iran.

Integration of ZnO with g-C3N4 structures in core–shell approach via sintering process for rapid detoxification of water under visible irradiation

We integrated ZnO with g-C3N4 nanostructures via successful core–shell formation using single step simple sintering process for photocatalysis application. Analytical tools show that the g-C3N4 shell with an average thickness of 3 nm has been coated onto surface of ZnO nanoparticles. Additionally, few ZnO particles are sporadically distributed on g-C3N4 sheets forming their nanocomposites. Further, these core–shell nanocomposites are used as photocatalysts for the degradation of Rhodamine B (RhB) under visible irradiation. As a result of photocatalysis measurements, it was found that 0.75 wt% zinc source with g-C3N4 exhibited almost two times high kinetic rate constant (k = 6.87 × 10−3 min−1) as compared with that of pure g-C3N4 (k = 3.38 × 10−3 min−1) and ZnO (k = 1.03 × 10−3 min−1) nanostructures. This enhanced photocatalytic performance of core–shell nanocomposites was aroused from effective interfacial charge separation and transportation, resulted into rapid degradation of RhB molecules. Moreover, increased optical absorption in visible region of spectrum revealed the large number of generation of charge carriers. Fabricated ZnO/g-C3N4 core–shell nanocomposites are also stable upto four cycles, indicating its good stability. Therefore, present core–shell nanocomposites can be applied to water purification devices under visible irradiation.

The effect of varying the capping agent of magnetic/luminescent Fe3O4–InP/ZnSe core–shell nanocomposite

Magnetic–luminescent nanoparticles have shown great promise in various biomedical applications namely: contrast agents for magnetic resonance imaging, multifunctional drug carrier system, magnetic separation of cells, cell tracking, immunoassay, and magnetic bioseparation. This experiment describes the synthesis of a nanocomposite material, which is composed of an iron oxide (Fe3O4) superparamagnetic core and an indium phosphide/zinc selenide (InP/ZnSe) quantum dot shell. The magnetic nanoparticles (MNP’s) and quantum dots (QD’s) were synthesized separately before allowing them to conjugate. The MNP’s were functionalized with a thiol-group allowing the QD shell to bind to the surface of the MNP by the formation of a thiol–metal bond. The nanocomposite was capped with 3-mercaptopropionic acid, oleylamine, β-cyclodextrin and their influence on the photoluminescence investigated. The synthesized nanocomposite was characterized with high- resolution transmission electron microscopy (HR-TEM), energy-dispersive spectroscopy (EDS), selective electron area diffraction (SAED), scanning electron microscopy (SEM), superconducting quantum interference device (SQUID), and photoluminescence. These techniques yielded particle size, morphology, dispersion, and chemical composition including luminescence and florescence.