Core-shell Composites Research Articles

Piezoelectric core-shell fibrous scaffolds of PVDF-ZnO/PCL for bone regeneration

One promising approach to improve bone regeneration is the use of piezoelectric scaffolds, which can positively affect cell growth and proliferation. PVDF, as a piezoelectric polymer, is an attractive candidate for use as a bone scaffold. However, other components should be added to PVDF to improve wettability, biodegradability, biocompatibility, and other biological properties. In this research, PVDF containing ZnO-PCL core-shell fiber composites were fabricated by coaxial electrospinning. TEM images were used to determine the proper electrospinning parameters that can provide a homogenous core/shell structure. Afterward, the surface of the samples was corona-treated to improve wettability. FTIR spectroscopy was used to estimate the piezoelectric β phase fraction in the core PVDF fibers, which demonstrated that the highest β phase fraction was obtained in the presence of 0.5 wt% ZnO nanoparticles. The tensile test results revealed that by adding ZnO nanoparticles to the scaffolds, the ultimate tensile strength of samples decreased, yet the values were in the acceptable range. The water contact angle measurements showed that the corona treatment could successfully reduce the contact angle from about 130° to 60°. Based on the obtained results, the F-0.5Z sample was chosen as the optimum sample and was used for biological and piezoelectric assessments. It rendered the piezoelectric output of 6.5 pC/N. In vitro assessments showed that this sample is biodegradable and bioactive, could support cell attachment and proliferation and intensified calcium mineralization. The composite containing 0.5 wt% ZnO had the best result and could be used as a scaffold in bone regeneration and repair.

Biocompatible Upconverting Nanoprobes for Dual-Modal Imaging and Temperature Sensing.

The demand for multimodal nanomaterials has intensified in recent years driven by the need for ultrasensitive bioimaging probes and accurate temperature monitoring in biological objects. Among the different multimodal nanomaterials that have been extensively studied in the past decade, upconverting nanoparticles are among the most promising. In this paper, we report the synthesis of upconverting nanoparticles with complex core-shell compositions, capable of being excited by 808 or 980 nm laser irradiation and exhibiting a good MRI response. The synthesized nanoparticles also demonstrated high colloidal stability in both aqueous and biological media as well as temperature-sensing capabilities, including the physiological range. Furthermore, the upconversion nanoparticles exhibited significantly lower cytotoxicity for HEK293T cells than the commercially available MRI contrast agent Gd-DTPA.

Optimization and regulation of catalytic activity and stability: Pt–Ni diamond-shaped pearl nanochains with core-shell structure as high-efficient oxygen reduction reaction catalysts

The low utilization efficiency and poor stability of carbon-supported Pt nanoparticles (Pt/C) catalyst are two main problems of proton exchange membrane fuel cells (PEMFC), which can improve the catalytic performance by forming alloys and precisely regulating morphology and structures. Here, we introduced a simple and direct method for synthesizing Pt–Ni diamond-shaped pearl nanochains (Pt–Ni DP-NCs) as efficient electrocatalyst for oxygen reduction reaction (ORR). The alloying with Ni could enhance the catalytic activity, but because of leaching out of Ni during the cathodic reaction process, which causes a poor stability. To achieve the optimal point for both high activity and robust stability, a portion of Ni is selectively etched from Pt–Ni DP-NCs precursor in advance. During the process of de-alloying, Pt atoms with high catalytic activity are exposed to the surface of the nanochain after atomic rearrangement, thus obtaining Pt–Ni etched diamond-shaped pearl nanochains (Pt–Ni EDP-NCs) with 1D core-shell structure, which consisted of Pt–Ni as the core and Pt as the shell. Benefitting from the unique 1D core-shell structure and composition, Pt–Ni EDP-NCs-9 (etched for 9 h) exhibits high catalytic activity and robust stability for ORR. The mass activity of the sample Pt–Ni EDP-NCs-9 is 0.43 A/mgPt, which is 1.65 times higher than that of the Pt–Ni DP-NCs (0.26 A/mgPt), and 2.05 times higher than that of commercial Pt/C (0.21 A/mgPt). In addition, the 1D core-shell structure enables Pt–Ni EDP-NCs to be highly stable, which only lost by 8.6% of mass activity after 10,000 long cycles, whereas Pt–Ni DP-NCs suffers from a 34% loss under the same conditions. This work provides a strategic approach for designing efficient Pt-based catalysts that simultaneously modulate activity and stability.

Hierarchical three-dimensional nanoflower-like CuCo2O4@CuCo2S4@Co(OH)2 core-shell composites as supercapacitor electrode materials with ultrahigh specific capacitances

Here, we prepare three-dimensional nanoflower-shaped CuCo2O4@CuCo2S4@Co(OH)2 core–shell materials on nickel foam (NF). CuCo2O4 (CuC) nanowire arrays and CuCo2S4 (CuS) nanosheets are grown directly on NF as the core through routine hydrothermal and high-temperature calcination methods and Co(OH)2 (CH) small nanosheets deposited on CuC@CuS nanoflowers via the potentiostatic deposition for 15 mins. Due to its distinctive structure and the synergistic effect between multiple components of CuCo2O4@CuCo2S4@Co(OH)2, the electrode has a fantastic specific capacitance (Cs, 4075F/g) under the current density of 1 A/g and satisfying cyclic stability (88.4 % capacitance retention and 84.6 % coulomb efficiency after 10,000 cycles). Additionally, an asymmetric supercapacitor (ASC) device equipped with CuC@CuS@CH-15/NF as a positive and active carbon (AC) electrode as a negative electrode can work steadily at 0–1.6 V. The ASC device can offer an excellent energy density (E, Wh kg−1) of 232.02 Wh kg−1 at a high-power density of 2879.8 W kg−1 (P, W kg−1) and an unexpected cycle stability (84.2 % of the original Cs and 81.7 % of coulombic efficiency after 10,000 repeated GCD tests), which far surpasses other ASCs of the same type. These results guide to enhancement of the electrochemical properties of cobalt-based oxides/sulfides@Co(OH)2 as the positive electrode for supercapacitors.

In situ growth of ZIF-67 to construct core-shell mosaic structural composites for efficient extraction of benzoylurea insecticides.

A novel mosaic structure Silica@C/Co@ZIF-67 composite was synthesized by successfully embedding Co nanoparticles on the surface of silica spheres with the help of thermoplastic polyethyleneimine by carbon-reduction. The ZIF-67 half-shell layer structure was synthesized by the in-situ growth of ZIF-67 on the surface of silica spheres through the coordination of 2-methylimidazole with Co metal nodes. The composite was used as a magnetic solid-phase extraction adsorbent combined with high performance liquid chromatography-ultraviolet detector (HPLC-UV) for the extraction and determination of benzoylurea insecticides (BUs) in vegetables and tea. Based on the presence of π-π, hydrophobic and hydrogen bonding interactions between Silica@C/Co@ZIF-67 and BUs, the BUs were rapidly captured by the composites resulting in high adsorption performance. Under the optimal extraction parameters, the linear ranges were 0.3-200µg L-1 for diflubenzuron, 0.6-200µg L-1 for chlorbenzuron, and 1.0-200µg L-1 for triflumuron, teflubenzuron, and flufenoxuron, with correlation coefficients (R2) greater than 0.9991. The limits of detection (LODs) of the method were 0.1-0.3μg L-1, and the relative standard deviations (RSDs) were 1.2-3.0% for intra-day and 2.6-4.6% for inter-day. In the spiked recovery experiments of vegetables and tea, the recoveries of the five kinds of BUs ranged from 75.8 to 112.9%. In addition, after 10 repetitions using Silica@C/Co@ZIF-67, the recoveries of the five kinds of BUs were still as high as 78.4 to 83.9%.

Preparation of a core-shell magnetic potassium nickel copper hexacyanoferrate/zeolitic imidazolate framework composite for rubidium adsorption

Magnetic substrates are favorable for separating adsorption-saturated powder adsorbents from solutions. Here, a core-shell magnetic potassium nickel copper hexacyanoferrate composite (MKNiCuFC@ZIF-8) modified with zeolitic imidazolate frameworks was synthesized for selective extraction of rubidium (Rb) in solution. MKNiCuFC@ZIF-8 was analyzed in depth using N2 adsorption-desorption, SEM, XRD, FT-IR, XPS, etc. Batch experiments were employed to assess the adsorption properties of MKNiCuFC@ZIF-8 for Rb+. The adsorption behavior based on the exchange behaviors of Rb+ and K+ conforms to the pseudo-second-order kinetic model. Meanwhile, the adsorption data are well fitted through the Langmuir isotherm model and reached a maximum adsorption amount of 1030.69 mg g−1 at 45 °C. Furthermore, MKNiCuFC@ZIF-8 could be regenerated with 90.3 % of absorbed Rb+ being desorbed in 1 mol L−1 of KCl within 24 h.

Photocatalytic Degradation of Malachite Green by Titanium Dioxide/Covalent Organic Framework Composite: Characterization, Performance and Mechanism.

In this paper, a titanium dioxide/covalent organic framework (TiO2/COF) composite was prepared and its photocatalytic removal of dye was investigated. Using tetrabutyl titanate as a titanium source, TiO2 nanomaterial was prepared by sol-gel method. In the presence of TiO2, TiO2/COF core-shell composite was prepared by solvothermal synthesis using melamine and 1,4-phthalaldehyde as ligands. The prepared materials are characterized by SEM, TEM, XPS, XRD, TG, FTIR, BET, EPR, PL, and UV-Vis-DRS techniques. Using malachite green as a model of dye wastewater, the photocatalytic degradation performance of TiO2/COF composites was investigated under the irradiation of ultraviolet light. The results show that the modification of COF significantly improves the photocatalytic efficiency of TiO2, the degradation rate increases from 69.77 % to 93.64 %, and the reaction rate constant of the first-order kinetic equation is increased from 0.0078 min-1 to 0.0192 min-1. Based on the free radical capture experiment, the photocatalytic degradation mechanism of TiO2/COF was discussed, and the feasibility of its photocatalytic degradation of malachite green was theoretically clarified. Accordingly, a simple and practical method for photocatalytic degradation of malachite green was constructed, which has potential application value in the degradation of dye wastewater.

Plasmonic silver and gold nanoparticles: shape- and structure-modulated plasmonic functionality for point-of-caring sensing, bio-imaging and medical therapy.

Silver and gold nanoparticles have found extensive biomedical applications due to their strong localized surface plasmon resonance (LSPR) and intriguing plasmonic properties. This review article focuses on the correlation among particle geometry, plasmon properties and biomedical applications. It discusses how particle shape and size are tailored via controllable synthetic approaches, and how plasmonic properties are tuned by particle shape and size, which are embodied by nanospheres, nanorods, nanocubes, nanocages, nanostars and core-shell composites. This article summarizes the design strategies for the use of silver and gold nanoparticles in plasmon-enhanced fluorescence, surface-enhanced Raman scattering (SERS), electroluminescence, and photoelectrochemistry. It especially discusses how to use plasmonic nanoparticles to construct optical probes including colorimetric, SERS and plasmonic fluorescence probes (labels/reporters). It also demonstrates the employment of Ag and Au nanoparticles in polymer- and paper-based microfluidic devices for point-of-care testing (POCT). In addition, this article highlights how to utilize plasmonic nanoparticles for in vitro and in vivo bio-imaging based on SERS, fluorescence, photoacoustic and dark-field models. Finally, this article shows perspectives in plasmon-enhanced photothermal and photodynamic therapy.

Urchin-like covalent organic frameworks templated Au@Ag composites for SERS detection of emerging contaminants.

Au@Ag core-shell composites were successfully fabricated on urchin-like covalent organic frameworks (COFs), providing a platform with numerous hot spots for the detection of two categories of emerging contaminants: sulfonamide antibiotics and nanoplastics, using surface-enhanced Raman spectroscopy (SERS). Au seeds (∼10 nm) were generated on the COFs, leveraging the reducing properties of the vinyl and imino groups within the framework. This ensured the growth of dense and uniformly distributed Ag nanoparticles. The COFs exceptionally large surface area (2324 m2 g-1) and high adsorption capacity, significantly contributed to the enrichment and detection of trace pollutants. As a result, using a portable Raman spectrometer, limits of detection of 0.008 μmol L-1 for sulfamethoxazole and 0.029 mg L-1 for polystyrene nanoplastics were achieved.

Construction of core-shell magnetic metal-organic framework composites Fe3O4@MIL-101(Fe, Co) for degradation of RhB by efficiently activating PMS.

Low catalytic efficiency and catalyst recovery are the key factors limiting the practical application of advanced oxidation processes. In this work, a core-shell magnetic nanostructure Fe3O4@MIL-101(Fe, Co) was prepared via a simple solvothermal method. The core-shell structure and magnetic recovery performance were characterized by various technologies. The results of dye degradation experiments proved that within 10 minutes, the Fe3O4@MIL-101(Fe, Co)/PMS system can degrade more than 95% of 10 mg per L Rhodamine (RhB) at an initial pH of 7, which possesses higher catalytic activity than the Fe3O4/PMS system and the MIL-101(Fe, Co)/PMS system. The effects of initial solution pH and coexisting anions in water on the degradation of RhB were further discussed. The results showed that Fe3O4@MIL-101(Fe, Co) displayed excellent degradation efficiency in a wide pH range of 3-11 and capability of resisting coexisting anions. It is worth mentioning that after five cycles, the RhB removal rate can still be maintained at over 90% after 10 minutes of reaction. Free radical quenching experiments were further studied, confirming that ˙OH and SO4-˙ were involved in the degradation of RhB, while the dominating active free radical was SO4-˙. The possible reaction mechanism of the RhB degradation process was also inferred.

Green synthesis of 3D core-shell SnS2/SnS-Cd0.5Zn0.5S multi-heterojunction for efficient photocatalytic H2 evolution.

Low charge carrier separation efficiency is one of the key factors restricting photocatalytic hydrogen evolution performance. It is an effective strategy to build heterojunctions to steer charge migration. Herein, a series of x-SnS2/SnS-Cd0.5Zn0.5S (x-SS-CZS) nanosphere composites with varying mass ratios of SnS2/SnS (SS) were prepared through in situ hydrothermal synthesis. Moreover, XRD, TEM, and XPS were used to characterize the 3D core-shell SS-CZS multi-heterojunction composite. The 5-SS-CZS heterojunction composite with 5 wt% content of SS exhibits a remarkable hydrogen evolution rate of 168.85 mmol g-1 h-1, which is 5.4 times higher than that of pristine twin CZS (31.08 mmol g-1 h-1) and 1.9 times higher than that of 5-SnS2-CZS (88.21 mmol g-1 h-1). Furthermore, the composite catalyst showed excellent photostability after four cycles of reactions under visible light illumination. The apparent quantum yield at λ = 420 nm could reach up to 24.78%. The excellent hydrogen evolution performance of 5-SS-CZS nanospheres is ascribed to the following factors: (1) a core-shell catalyst with broad spectral absorption improves light utilization efficiency, (2) hybrid material with large surface area provides more active sites and shows the highest H2 activity, (3) a multi-heterojunction composite extends the lifetime of photoinduced carriers and accelerates charge separation and migration, and (4) SS as a hole trapping agent enhances the photocatalytic stability performance. This work proposes a possible photocatalytic mechanism, while also providing a novel approach for the synthesis of highly active and stable photocatalysts.

Rational design of versatile 1D Ti-O-based core-shell nanostructures for efficient pollutant removal and solar fuel production

The rational design of Ti-O-based nanocomposites is of great importance for achieving efficient solar energy conversion and storage. Herein, novel one-dimensional (1D) K2Ti6O13/TiO2 core-shell nanobelt composites were fabricated by a...

Improved ZnWO4@NiCo2O4 core-shell nanosheet arrays with regulatory interfaces and electronic redistribution.

ZnWO4@NiCo2O4 core-shell nanosheet array composites are synthesized on nickel foam via a two-step hydrothermal method. The optimal conditions, including a Ni(NO3)2·6H2O to Co(NO3)2·6H2O molar ratio of 2 : 1, 12 hours reaction time, and 120 °C temperature, yield a specific capacitance of 875 C g-1 at 1 A g-1. The electrode also maintains 81.1% capacitance after 10 000 cycles. The material's performance is attributed to its core-shell structure, which enhances ion diffusion and electron transport. This study presents a viable approach for high-performance supercapacitor electrodes.

SnO2/Sn with core-shell structure Schottky heterojunctions loaded in graphene to promote electrochemical reaction kinetics and enable efficient lithium-ion storage.

The stannic oxide (SnO2) anode expands in volume during cycling causing a decrease in reversible capacity. In this work, we generated a spherical SnO2/Sn heterojunction with core-shell structure composites encapsulated by graphene (SnO2/Sn/G) in situ using a simple one-step hydrothermal and subsequent annealing process. SnO2/Sn heterojunction nanospheres dispersed in a porous graphene framework accelerate the diffusion kinetics of electrons and ions. In addition, the structure plays a key role in mitigating large volume changes and nanostructure agglomeration. As a result, SnO2/Sn/G exhibits excellent performance as an anode material for lithium-ion batteries (LIBs), maintaining a reversible specific capacity of 720.6 mA h g-1 even after 600 cycles at a current density of 0.5 A g-1.

Activities of Na0.5Bi0.5TiO3@C core-shell composites in piezo-photocatalytic degradation of tetracycline antibiotic

The Na0.5Bi0.5TiO3 and Na0.5Bi0.5TiO3@C core-shell catalysts were synthesized successfully using the solvothermal method. A few of Ti4+ was reduced to Ti3+ with the help of glucose in the solvothermal process, which results in the formation of oxygen vacancies in the NBT@C catalysts. Meanwhile, the excessive glucose was carbonized, which accumulated on the surface of Na0.5Bi0.5TiO3 and formed Na0.5Bi0.5TiO3@C core-shell composites. The phase, microstructure, optical and piezoelectric properties, as well as the catalytic activities of the synthesized catalysts were characterized. The Na0.5Bi0.5TiO3@C core-shell composites show higher photocatalytic activity that of pure Na0.5Bi0.5TiO3 on account of more visible light absorbance. And the piezo-photocatalytic activities to tetracycline of the synthesized catalysts are highest due to the synergetic effects of photocatalysis and piezocatalysis.

Development of barium hexaferrite core–shell composites as high-performance microwave absorption by optimizing hydrothermal synthesis

In conjunction with the enhancement of societal living standards and the rapid development of information technology, an extensive variety of high-capacity electronic devices are being introduced to the market. The heightened demands result in the generation of electromagnetic wave radiation, which poses a potential risk to human well-being. Barium hexaferrite (BHF) is one of the radar-absorbing materials (RAMs) that can absorb electromagnetic waves because it has a high anisotropic field. However, its drawbacks are narrow absorption and less stability. Molybdenum disulfide (MoS2), is the best candidate for the reinforcement of BHF. The study investigated the impact of increasing the thiourea, temperature, hydrothermal holding time, and sample thickness on reflection loss. This study used a two-step molten salt and hydrothermal synthesis to make a BaFe12O19@MoS2 core-cell composite. Two-step molten salt and hydrothermal synthesis methods created single-phase BaFe12O19@MoS2 core-cell composites that worked well. The results showed that adding MoS2 to BHF changed BHF's magnetic properties from hard to soft. Increasing the hydrothermal temperature up to 220 °C effectively reduced the reflection loss of BaFe12O19@MoS2. On a 2 mm thick sample containing 100 mmol thiourea, the study achieved an electromagnetic wave absorption of 99.97 % with a reflection loss of –35.41 dB (17.37 GHz). The results of this research can be applied to protect electronic devices vulnerable to signal interference from satellite radar systems at frequencies of 12–18 GHz

Synthesis of SiC nanowires wrapped in trimetallic layered double hydroxide nanosheets with core-shell structure via self-assembly growth approach for effective electromagnetic wave absorption

The optimization of microstructure and composition is an important strategy to obtain high-performance electromagnetic wave absorption (EMA) materials. In this study, several fungus-like two-dimensional (2D) trimetallic layered double hydroxide (LDH) nanosheets have been synthesized with tunable metallic ions of Ni2+, Co2+, and Zn2+ by using a compositional genetic strategy from MOF. Thereafter, a series of core-shell composites have been fabricated at room temperature by the self-assembly growth approach, constructed from 2D trimetallic LDH nanosheets wrapped on 1D SiC nanowires. The composition and structure of the samples can be preserved by varying the Co and Zn ratios. The EMA materials were prepared by performing a thermal treatment approach in the air atmosphere based on the synthesized composites described above. A reasonable integration of dielectric and magnetic components and an opportune core-shell structure provide better impedance matching, multiple reflections and scattering, polarization loss, enhancing conduction loss, and magnetic loss. The results show that NiCo2Zn1-LC@SiC exhibits superior EMA performance with the minimum reflection loss (RLmin) of −44.73 dB at a thickness of 1.86 mm and the maximum effective absorption band (EABmax) of 6.12 GHz at 2.12 mm. This work proves the influence of the structure and composition on absorbers and provides ideas for the design and development of high-performance EMA materials in a facile approach.

Construction of core-shell TiNb2O7/Li4Ti5O12 composites with improved lithium storage for lithium-ion batteries

In this study, the (TiNb2O7) TNO and modified (Li4Ti5O12) LTO composites with the core–shell (CS) structures have been designed and prepared by the spry-dried method. In the structural composite, the modified LTO core can stabilize the dimensional stability with excellent rate capability, and the TNO shell can offer a larger capacity, leading to high-performance anode materials. Our results indicate that the CS composites without the TNO nanoparticles (NPs) aggregation reveal a more negligible electrochemical polarization (EP) with improved kinetics than traditional composites. The optimal TNO content in the CS composite is 30 wt%, which can show a larger capacity than that of bare LTO, with the C-rate ranging between 17.5 and 3500 mA g−1. It delivers a capacity of 164.9 mA h g−1 at 1050 mA g−1, higher than bare LTO (157.6 mA h g−1) and traditional composite (154.6 mA h g−1). Furthermore, the full lithium-ion battery (LIB) is fabricated using the CS composite as the anode and LiNi0.5Mn1.5O4 (LNMO) as the cathode. The designed LIB shows an improved energy density of 122.0 W h kg−1 with remarkable cycling stability.

Influence of preparation method on the structure, morphology, and conducting property of poly(m‐aminophenol)/silver nanocomposite

AbstractThe aim is to create a nanocomposite with well‐defined morphology having enhanced electronic characteristics, suitable for a diverse range of applications including sensors, supercapacitors, and electrode materials, among others. A composite consisting of the functional conjugated polymer, such as poly(m‐aminophenol), combined with silver nanoparticles, can be fabricated by meticulously regulating its structure, morphology, and properties. In the current research, three different morphologies, viz., nanoparticles distributed, nanofibrous, and core–shell were obtained following three different methods of preparation. The nanocomposite with a uniform distribution of 5.15 wt% small silver nanoparticles exhibited the highest average DC conductivity of 1.3 × 10−4 S cm−1. However, the nanofibrous composite with 2.79 wt% silver loading and core–shell nanocomposite with 5.59 wt% silver loading were found to have poor conductivities in order of 10−7 S cm−1. The electronic conduction of the nanocomposites prepared in three different methods was correlated with the structural features of the polymer matrix and the interfacial interaction between the components. This suggests that the nanocomposites with uniform distribution of small silver nanoparticles hold high potential as electronic material for a wide range of applications.Highlights Optimization of preparation of poly(m‐aminophenol)/silver nanocomposite. Investigation of structure and morphologies of the composites. Morphologies—nanocomposites, nanofiber composite, and core–shell composite. Highest average DC‐conductivity of nanocomposite obtained as 1.3 × 10−4 S cm−1. Conductivity in order of 10−7 S cm−1 was observed for the other two nanocomposites.

Fabrication of porous X-shaped Fe3O4@C core-shell structures for tunable microwave absorption

Designing porous materials with low density and high specific surface area is one of the strategies to obtain excellent wave absorbing properties. In this study, the carbon-coated porous X-shaped Fe3O4 composites used as microwave absorption materials were prepared by heat treatment of FeOOH@Polydopamine (PDA) core-shell precursors. It revealed that the X-shaped Fe3O4 core showed improved magnetic loss in GHz band due to its special shape anisotropy and large specific surface area. In addition, the modification of carbon enabled the Fe3O4 absorbers to have stronger polarization and higher electrical conductivity. The composites exhibited great freedom in performance tunability, allowing for strong absorption (RL<−40 dB) at different frequencies. For composites with thick carbon shell, the reflection loss reached the optimal value of − 64.92 dB at 15.04 GHz at the thickness of 1.75 mm, and the effective bandwidth was up to 4.64 GHz (13.04–17.68 GHz). The impressive performance of the as-prepared Fe3O4 @C core-shell composites was mainly attributed to the complementary behaviors of strong dielectric loss and magnetic loss.