Shell Nanocomposites Research Articles

Optical and electrical properties of Fe3O4@MoS2 nanocomposites and doped lead boron tellurite glass

Transition metal oxide core–shell-nanostructured Fe3O4@MoS2 is attractive in photocatalytic, optoelectronics and optical applications. Magnetic Fe3O4@MoS2 core–shell nanocomposites were synthesized by a facile hydrothermal method. Transmission electron microscopy (TEM) results show that the 80-nm-diameter nanoparticles were composed of Fe3O4 core and MoS2 shell. The presence of characteristic of Fe–O and Mo–O vibrations in Fe3O4@MoS2 FT-IR spectra indicate the Fe3O4 has been composited with MoS2 successfully. The optical UV–Vis spectra of Fe3O4@MoS2 composites exhibited a strong peak at 250–300 nm due to the strong absorption of MoS2. The photoluminescence spectra of Fe3O4@MoS2 showed two peaks at 670 and 625 nm corresponding to A1 and B1 excitons of MoS2. Glass-containing nanoparticles have promising multifunctional advantages such as the simultaneous existence of magnetic, optical and photoluminescence. Glasses containing different Fe3O4@MoS2 contents were fabricated in this study by melt-quenching method. Glass network was disordered by the doping, and as the doping content increasing, the coordination numbers were changed and more non-bridging oxygen numbers were produced, these modifications on glass structure induced changes of glass properties. Compared to spectra of base glass, the UV–Vis absorption spectra of doped glasses showed a red-shift in cutoff wavelength and an absorption peak around 680 nm due to the excitation of Mo5+ (4d1) ions. The photoluminescence spectra of Fe3O4@MoS2-doped glasses present one intense peak centered around 570 nm due to the charge transfer of O2−→Mo6+ ions in MoO42− units, and the intensity of this emission peak increased with doping contents. The conductivity of base glass gets increased from 1.59 × 10−7 to 2.08 × 10−6 S cm−1 when the doping content reaches to 5%. Such improvement is mainly caused by the non-adiabatic small polaron hopping at 473 K and non-bridging oxygens production. Glass doped with 5% Fe3O4@MoS2 exhibited promising photoluminescence, optical cutoff wavelength (526 nm) and high electrical conductivity (2.08 × 10−6 S cm−1) due to the charge transfer of Fe and Mo ions and high polarization property of Fe3O4@MoS2.

Zn@C Core–Shell Nanocomposite for Rechargeable Aqueous Zn//MnO2 Batteries with Long Lifetime

Rechargeable zinc‐based aqueous batteries are a promising candidate for next‐generation energy storage devices because of the high theoretical energy density of Zn as well as the availability, safety, and cheap price of Zn‐based aqueous batteries. A Zn@C core–shell composite is designed to overcome two problems of Zn anodes, that is, the formation of Zn dendrites and the corrosion/loss of Zn anode during the charge–discharge process, influencing the lifetime of Zn‐based aqueous batteries. The prepared Zn@C composite from ZnO@C with electrochemical reduction is robust as the anode for a Zn@C//MnO2 battery, and a 98.8% retention after 400 cycles is obtained at a discharge rate of 5 C. The specific capacitance of Zn@C//MnO2 battery can reach 135 mAh gZn−1 at 3 C, and the energy density of this battery can reach 75.9 Wh Kg−1. The coated carbon layer on Zn/ZnO plays a role in protecting Zn/ZnO from leaching or corrosion by KOH, so the structure of Zn@C is a key factor in improving the cycling lifetime of Zn‐based aqueous batteries.

Carbon-nanotube@graphene core–shell nanostructures as active material in flexible symmetrical supercapacitors

A carbon nanomaterial with core–shell structure was constructed from a composite of graphene and carbon nanotubes (CNT@G). A unique technology called polymer-assisted metal-catalyzed chemical vapor deposition (CVD) was used to first disperse a gold catalyst precursor, via the assistance of polyvinyl alcohol, on the CNT surface and then facilitate graphene growth by reducing the gold nanoparticles during CVD. A CNT@G/Ni electrode was then prepared from the CNT@G core–shell nanocomposite without using polymer bonding or annealing. The as-fabricated CNT@G/Ni electrode with mass loading of 3 mg cm−2 exhibited a high specific capacitance of 620.3 F g−1 at a scanning rate of 1 mV s−1 in the three-electrode configuration. When the mass loading of the electrode reached 5 mg cm−2, the areal capacitance was 781.2 mF cm−2 at a scanning rate of 1 mV s−1. Symmetric supercapacitors were constructed using these CNT@G/Ni electrodes and a gel electrolyte consisting of carboxymethyl cellulose and potassium hydroxide. The devices offered advantages of flexibility, high operating voltage (1.8 V), high specific capacitance (268.7 mF cm−2), and high cycling performance (120.4% capacity retention after 10000 cycles).

Lightweight broadband microwave absorbers of core–shell (polypyrrole/NiZn ferrite) nanocomposites in the X-band: insights on interfacial polarization

Polypyrrole/Ni0.5Zn0.5Fe2O4 (PPy/NiZn ferrite) nanocomposites are prepared using the in-situ chemical oxidative polymerization method of pyrrole in the presence of the ferrite. The composites are characterized using scanning and transmission electron microscopies, vibrating sample magnetometry, thermal gravimetric analysis, X-ray diffractometry, Fourier transform infrared spectroscopy and UV–visible spectroscopy. The microwave absorption characteristics are performed by measuring the reflection loss in the X-band. The results indicate the presence of a maximum reflection loss of − 30.0 dB at 10.9 GHz with a matching thickness of 3.0 mm and a bandwidth of 3.6 GHz for a weight ratio PPy/NiZn ferrite of 2:1 and a loading not exceeding 7.5% w/w of nanocomposite in a host matrix of paraffin wax. The surface density of the absorber is only 2.74 kg/m2. The role of interfacial polarization in promoting microwave absorption characteristics is also highlighted.

Modified Thorium Oxide Polyaniline Core–Shell Nanocomposite and Its Application for the Efficient Removal of Cr(VI)

The core–shell ThO2-PANI nanocomposite was synthesized using polyaniline (PANI) as a favorable conducting polymer and used for the removal of Cr(VI) from water. Thorium dioxide (ThO2) nanoparticles were embedded by PANI via an in situ polymerization process. The formation of the material was investigated by XRD, FESEM, EDX, TEM, TGA-DTA, FTIR, Raman, XPS, and N2 sorption isotherm analysis. The FESEM and TEM analyses confirmed that PANI was successfully formed on the ThO2 surface. The ThO2-PANI nanocomposite could effectively adsorb Cr(VI) through electrostatic attractions, which were partially reduced to Cr(III) during the adsorption experiment, ensuring the proficient adsorption as well as better removal of Cr(VI) from water. The synthesized nanocomposite material exhibited a high uptake capacity toward Cr(VI) as compared to other reported materials. The adsorption kinetics data sufficiently defined the pseudo-second-order kinetic model. The Cr(VI) adsorption onto ThO2-PANI was greatly dependent on the s...

Investigations on structural, optical and electrical property of ZnO-CuO core–shell nano-composite

ZnO-CuO core–shell nano-composite was synthesized by two-stage assisted wet-chemical sol-gel method. The nano-composite investigated by X-ray diffraction, field effective scanning electron microscope, UV–visible spectroscopy and Electrical property at different frequency range 100 Hz to 2 MHz and at different temperature. The X-ray diffraction pattern shows poly-crystalline growth of sample, UV–visible spectrum shows higher absorption in ZnO-CuO nano-composite as compare ZnO, which can be understood in vicinity of morphology and heterojunction. The electrical conductivity of nano-composite has been increased with frequency and temperature due to defect available in the sample and thermal excitation of the charges in the sample respectively.

Design of hybrid protein-coated magnetic core-mesoporous silica shell nanocomposites for MRI and drug release assessed in a 3D tumor cell model

In this work, we describe the design and the use of a novel theranostic hybrid nanocomposite made of an iron oxide core and a mesoporous silica shell (IO@MS) of ca. 30 nm coated by human serum albumin (HSA) layer for magnetic resonance imaging and drug delivery applications. The porosity of IO@MS nanoparticles was loaded with an antitumoral drug, Doxorubicin (Dox) reaching a high drug loading capacity (DLC) of 34 w%. To entrap the drug, a tight HSA coating held via isobutyramide (IBAM) binders was deposited. We show that this protein nanoassembly entraps the drugs efficiently and behaves as an innovative enzyme-sensitive gatekeeper that is degraded upon protease action. Finally we assess the Dox release in a 3D cell model via confocal imaging and its cytotoxicity is shown by growth inhibition studies on liver cancer cell spheroids.

A facile synthesis of palladium encased Ag nanowires and its effect on fluorescence and catalysis

A facile polyol synthetic route was designed to prepare an ultra thin Pd nano sheath over Ag nanowires (NWs) forming metal-metal core–shell nanocomposites. Here we report the one pot synthesis of Pd assembly onto growing Ag NWs. Pd salts were reduced over varied time intervals during the growth process of the Ag NWs. The Pd salt was introduced after 20, 30- and 40-minutes to the growing Ag NWs. The product was designated as Ag@Pd 20, 30, and 40 on basis of introducing interval. The morphology and constituents of each product was observed using SEM coupled with EDX. XRD was employed to characterize composite material. UV-Visible was used to determine the SPR of each material along with the pure Ag NWs and palladium nanoparticles. Similarly, fluorescence of each product was characterized using PL spectrophotometer, which was correlated with core and sheath. Finally, the catalytic reduction of nitrophenol into amino phenol by ultra thin sheet of Pd of each product was investigated and reaction order was ascertained.

Preparation and Characterization of Novel Magnetic ZnFe2O4–Hydroxyapatite Core–Shell Nanocomposite and Its Use as Fixed Bed Column System for Removal of Oil Residue in Oily Wastewater Samples

Using magnetic nanoparticles to remove the dispersed oil from produced water is a promising way to overcome the difficulties faced by current treatment technologies. Therefore, in this study, novel ZnFe2O4-hydroxyapatite core-shell nanocomposites (ZFHA) was prepared by precipitation method and investigated as an adsorbent to remove residual oil from produced wastewater. The prepared ZFHA nanocomposites were studied by FTIR, X-ray diffraction, HRTEM, SAED, and EDX. The results revealed that hydroxyapatite was coated on the ZnFe2O4 surface and formed a core-shell structure. The effect of various parameters on oil adsorption process like bed height (59, 118 and 178 mm), flow rate (1, 3 and 5 mL min−1), effect of temperature 25–77 °C, initial oil concentration (100, 500, 1000 and 10,000 ppm) and pH (2–10) were investigated. The experimental data showed that with increased column bed depth from 59 to 178 mm, breakpoint time (tb) increased from 30 to 48 min. The highest equilibrium adsorption capacity of oil at optimum conditions (77 °C, 10,000 ppm, 3 mL/min and 178 mm) were estimated to be 3500 mg L−1. The contact time decreased with the increase of bed height and flow rate. Adsorption kinetic was evaluated in a fixed bed column. Finally, the regeneration of the exhausted ZFHA adsorbent was assessed; which revealed satisfactory results for three times reusability after saturation. Therefore; ZFHA could be applied effectively for adsorption of residual oil from synthesis oily wastewater samples prepared from produced water of Egyptian fields of the petroleum industry.

Degradation of bentazon herbicide by heterogeneous catalytic ozonation with ZnO-scallop shell nanocomposite: kinetic, reaction pathways and mineralization

Degradation of bentazon herbicide by heterogeneous catalytic ozonation with ZnO-scallop shell nanocomposite: kinetic, reaction pathways and mineralization

An ultrasonic method for the synthesis, control and optimization of CdS/TiO2 core-shell nanocomposites.

In this study, an ultrasonic method was utilized in combination with microemulsion to synthesize CdS/TiO2 core–shell nanoparticles and control their particle size and ultimately optimize the influential parameters. Moreover, response surface methodology (RSM) was used to optimize the thickness of the shell. Herein, four parameters, i.e. temperature (67–79 °C), synthesis retention time (45–105 min), TiO2 : CdS ratio (1.5–7.5) and the power of ultrasound waves (37–53 watt), were optimized to synthesize nanoparticles with an average size of up to 10 nm. A correlation equation was introduced for the size range of 10–90 nm, which was then proven to have excellent predictions. To verify the proposed model, two different sets of combinations were selected to synthesize 10 nm composites, and consequently, nanocomposites with the sizes of 10.4 and 10.9 nm were successfully synthesized. The power of ultrasound waves and retention time had the most influence on the size of the particles. Further experiments proved that the optical absorption spectrum of the composite particles was extended to the visible region. Furthermore, the formation of CdS/TiO2 core–shell nanocomposites was confirmed by different characterization techniques including XRD, TEM, EDAX, UV-vis, FTIR and DLS.

SnSe@SnO2 core–shell nanocomposite for synchronous photothermal–photocatalytic production of clean water

Solar power-based synchronous photothermal evaporation and photodegradation show significant promise on water treatment.

Design of core-shell titania-heteropolyacid-metal nanocomposites for photocatalytic reduction of CO2 to CO at ambient temperature.

The photocatalytic conversion of CO2 not only reduces the greenhouse effect, but also provides value-added solar fuels and chemicals. Herein, we report the design of new efficient core–shell nanocomposites for selective photocatalytic CO2 to CO conversion, which occurs at ambient temperature. A combination of characterization techniques (TEM, STEM-EDX, XPS, XRD, FTIR photoluminescence) indicates that the CO2 reduction occurs over zinc species highly dispersed on the heteropolyacid/titania core–shell nanocomposites. These core–shell structures create a semiconductor heterojunction, which increases charge separation and the lifetime of charge carriers' and leads to higher electron flux. In situ FTIR investigation of the reaction mechanism revealed that the reaction involved surface zinc bicarbonates as key reaction intermediates. In a series of catalysts containing noble and transition metals, zinc phosphotungstic acid–titania nanocomposites exhibit high activity reaching 50 μmol CO g−1 h−1 and selectivity (73%) in the CO2 photocatalytic reduction to CO at ambient temperature. The competitive water splitting reaction has been significantly suppressed over the Zn sites in the presence of CO2.

Study of synergistic effect between CuO and CeO2 over CuO@CeO2 core–shell nanocomposites for NH3-SCO

CuO@CeO2 core–shell nanocomposites were fabricated and applied in NH3-SCO. Synergistic effect of CuO–CeO2 promotes the formation of the Cu–O–Ce structure, which is beneficial to N2 selectivity.

Preparation of core-shell structured metal-organic framework@PANI nanocomposite and its electrorheological properties.

A novel core–shell-type electrorheological (ER) composite material was fabricated via using polyaniline as an insulating layer to the outer surface of the core conductive metal–organic framework (MIL-125) with controlled size and morphology. MIL-125 was firstly synthesized by a solvothermal method, and then polyaniline was synthesized in a polar solvent and a tight coating was successfully achieved to form a MIL-125@PANI core–shell nanocomposite. This core–shell structure greatly enhances the polarization ability of dispersed particles, thereby improving their rheological properties. The morphology of pure MIL-125 and MIL-125@PANI has been characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Their structure was characterized by X-ray powder diffraction. Moreover, the ER activity of MIL-125-based and MIL-125@PANI-based ER fluids by dispersing the particles into silicone oil was studied using a rotational rheometer. The results show that the MIL-125@PANI composite particles have higher ER properties.

Synthesis of Au@TiO2 core-shell nanoparticles with tunable structures for plasmon-enhanced photocatalysis.

Plasmonic metal–semiconductor nanocomposites, especially those with core–shell nanostructures, have received extensive attention as they can efficiently expand light absorption and accelerate electron–hole separation thus improving the photocatalytic efficiency. However, controlled synthesis and structure manipulation of plasmonic metal–semiconductor nanocomposites still remain a significant challenge. Herein, a simple and universal method has been developed for the preparation of plasmonic Au@TiO2 core–shell nanoparticles. Using such a method, uniform TiO2 shells are successfully coated on Au nanoparticles with various morphologies including nanorods, nanocubes, and nanospheres, and the thickness and crystallinity of the TiO2 shell can be simply tuned by adjusting the pH value and thermal treatment, respectively. Furthermore, the influence of the morphology of the Au core and the thickness and crystallinity of the TiO2 shell on the photocatalytic performance of Au@TiO2 towards the photodegradation of methylene blue is systematically explored. It is found that Au@TiO2 NPs with nanorod morphology and crystalline TiO2 shells display the best performance, which is 5 times higher than that of bare Au nanoparticles. This work provides a facile strategy for the fabrication of plasmonic core–shell nanostructures that show excellent performance in plasmon-enhanced photocatalysis.

Electrical and dielectrical properties of some novel polyaniline nanocomposites

Novel polyaniline/silver (PANI/Ag) and polyaniline/silver/cupper (PANI/Ag/Cu) core–shell nanocomposites have been successfully prepared. The morphology and the structure of the prepared nanocomposites have been characterized and elucidated. The AC conductivity measurements in the frequency range from 1MHz to 1GHz at different temperatures for the prepared nanocomposites have been investigated. The results showed very high conductivities and dielectric constants. The ac conductivities of the prepared nanocomposites are frequency dependent and follow up hopping conduction mechanism in general. The enhanced electrical properties of the prepared nanocomposites may be attributed to the superior core shell structure and the presence of the core Ag, Ag/Co and Ag/Cu nanoparticles.

Synthesis of daisy-shaped core–shell nanocomposites of chiral poly[(±)-2-(sec-butyl)aniline] in the solid state

A green and simple procedure is reported on the synthesis of a daisy-like core–shell nanocomposite of chiral poly[(±)-2-(sec-butyl)aniline]/nanosilica. This morphology is related to the use of nanosilica and a mechanism based on intermolecular interactions between particles of nanosilica and the polymer. The morphology of the samples and their coating were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), SEM-map and energy-dispersive X-ray spectroscopy (EDX). The outstanding feature of this study is that it presents the first report of an in situ formation of daisy-like morphology for polyaniline nanocomposites through one-pot route without using pre-functionalized nanosilica and any other template under the solid-state condition; while this polymer has displayed no specific morphology under most conditions. According to XPS and CHNS analysis, the nigraniline oxidation state was confirmed as well as fully doping of composites (around 75%) in contrast with partial doping of poly[(±)-2-(sec-butyl)aniline].HCl salt. The structure of nanosilica was studied by 29Si NMR. The sample showed a conductivity around 5.2 × 10−2 S/cm, consistent with the XPS results which revealed the doping level. In addition, the TLM measurement was applied to determine the contact resistance. In this study, a chiral conductive nanocomposite was prepared under a solid-state condition in compliance with the green chemistry principles. Moreover, it was found that the nanocomposite is in delocalized polaron structure using solid acid as a dopant. Additionally, from the industrial point of view, the processability has been improved due to the introduction of the 2-sec-butyl group within the polymer backbone.

Polydopamine-Inspired Design and Synthesis of Visible-Light-Driven Ag NPs@C@elongated TiO2 NTs Core–Shell Nanocomposites for Sustainable Hydrogen Generation

The primary challenge of photocatalytic hydrogen generation is to exploit a catalyst with good durability and low cost. Here, we designed a facile and efficient process of loading silver nanoparticles (Ag NPs) in situ on the core–shell nanocomposite of the elongated titanium dioxide nanotubes with a carbon layer (C@TiO2 NTs) by polydopamine (PDA) without addition of any binder. The combination of C@TiO2 NTs with Ag NPs has excellent performance toward photocatalytic hydrogen production and degradation of rhodamine B (RhB) under visible light irradiation. The characterizations (SEM, TAM, XRD, XPS, etc.) showed that the carbon layer on nanotubes could conformably cover the whole of TiO2 NTs to form the core–shell structure, which not only prevented Ag NPs from aggregating but also acted as the electronic transport channel. Meanwhile, Ag NPs were uniformly distributed on the surface of C@TiO2 NTs. In conclusion, under the synergistic effect of Ag nanoparticles and the outer-carbon layer, the utilization efficiency of visible light has been enhanced, and the recombination of electrons/holes has been suppressed for Ag@C@TiO2 NTs nanocomposites. Therefore, the degradation efficiency of RhB and hydrogen generation rate are 2.5 times and 4.8 times higher than those of the pure TiO2 NTs, respectively. This work may provide fruitful experience for developing a novel strategy into the design and fabrication of stable and highly active visible-light catalysts with noble metal modification toward sustainable hydrogen production in the energy filed.

Core-Shell Nanostructured Fe3O4-Poly(styrene-co-vinylbenzyl chloride) Grafted PPI Dendrimers Stabilized with AuNPs/PdNPs for Efficient Nuclease Activity.

Four different novel magnetic core–shell nanocomposites stabilized with Au/Pd nanoparticles (NPs) were prepared by a simple procedure and demonstrated their catalytic activity for effective cleavage of pBR322 DNA. Initially, the Fe3O4–poly(styrene-divinylbenzene-vinylbenzyl chloride) (ST-DVB-VBC) matrix functionalized with 3-aminobenzoic acid was prepared and grafted with PPI-G(2) and PPI-G(3) dendrimers. Each core–shell matrix was immobilized with AuNPs and PdNPs separately. The resulting composites were characterized by FT-IR, UV–vis, SEM, TEM, XRD, VSM, XPS, Raman, and TGA. The magnetic core–shell nanocomposites at concentrations from 30 to 50 μM were employed separately to study DNA cleavage by agarose gel electrophoresis. Among the four magnetic core–shell nanocomposites, Fe3O4–poly(ST-DVB-VBC)–PPI-G(3)–AuNPs showed higher activity than others for DNA cleavage, and formed Form-II and -III DNA. When the concentration of Fe3O4–poly(ST-DVB-VBC)–PPI-G(3)–AuNPs was increased from 40 to 45 and 45 to 50 μM, Form-III (linear) DNA was observed with 10 and 22%, respectively, in addition to Form-II. This observation suggests formation of linear DNA from the supercoiled DNA via nicked DNA-intermediated consecutive cleaving process. The magnetic core–shell nanocomposites were stable and monodispersed, and exhibited rapid magnetic response. These properties are crucial for their application in biomolecular separations and targeted drug-delivery in the future.