Core-shell Hollow Microspheres Research Articles

Unraveling hierarchical hollow NiCo2S4/MXene/N-doped carbon microspheres via dual templates for high-performance hybrid supercapacitors

A multi-step strategy was rationally designed to fabricate hierarchical hollow core–shell microspheres of NiCo2S4MXene/N-doped carbon (NiCo2S4/MXene/NC) using dual templates of the polyethylene microspheres and metal–organic framework material of ZIF-67. The integration of MXene and N-doped carbon significantly enhances the electronic conductivity of electrode, while the construction of hollow spherical structures effectively alleviates the instability of NiCo2S4/NC during the charge–discharge cycles, leading to the excellent charge storage performance with a high specific capacitance (1786 F g−1 at 1 A g–1) and impressive cycling stability (over 100 % capacitance retention after 10,000 cycles). A corresponding hybrid supercapacitor displays a high specific capacitance (190 F g−1 at 1 A g–1) with a maximum energy density (67 Wh kg−1 at 796 W kg−1) and great cycling stability (over 80 % capacitance retention after 10,000 cycles). The charge storage mechanism of NiCo2S4/MXene/NC is elucidated, revealing a combination of pseudocapacitive and battery-like behavior. Density functional theory (DFT) calculations indicate that the participation of MXene significantly increases the state density of NiCo2S4/MXene near the Fermi level compared to NiCo2S4, affirming its superior metallic conductivity. This work provides a facile route only with room-temperature stirring and high-temperature calcination to prepare well-defined metal sulfide composite microstructures with high electrochemical performance.

Rationally designed Mn2O3@ZnMn2O4/C core-shell hollow microspheres for aqueous zinc-ion batteries.

Manganese-based oxides are common cathode materials for aqueous zinc ion batteries (AZIBs) because of their great capacity and high working voltage. However, the sharp decline of capacity caused by the dissolution of manganese-based cathode materials and the low-rate performance restrict their development. To address these problems, unique core-shell structured Mn2O3@ZnMn2O4/C hollow microspheres are reported as an ideal cathode material for AZIBs. Benefiting from the hollow structure, the zeolitic imidazolate framework (ZIF)-derived carbon and ZnMn2O4. Its application in AZIBs as the cathode demonstrates its satisfactory rate performance, high cycle stability, and excellent reversibility. Its high reversible capacity is remarkable, which reaches its maximum of 289.9 mA h g-1 at 200 mA g-1 and maintains a capacity of 203.5 mA h g-1 after cycling for 700 times at 1000 mA g-1. These excellent performances indicate that this material is a potential cathode material of AZIBs.

Mechanism research of catalytic degradation of 1, 2-dichlorobenzene over highly efficient hollow calcium ferrite by in situ FTIR spectra

The hierarchical CaFe2O4 core-shell hollow microspheres are successfully fabricated by a facile solvothermal approach following heat treatment process. The hollow architecture exhibits high surface area and strong visible-light absorption capability. Meanwhile, the formation mechanism of hollow structure is proposed based on characterization results. Furthermore, the photocatalytic activity is tested by 1, 2-dichlorobenzene degradation under visible light irradiation, and the degradation ratio of CaFe2O4 core-shell hollow microspheres can reach 82.0% after 8 h. Moreover, relying on the in situ Fourier transform infrared technology, the catalytic oxidation process and degradation mechanism is clarified on CaFe2O4 surface, and the intermediate product (formate, acetate, maleate species, etc.) and the mineralized products (CO2 and H2O) are identified finally.

Sensitivity of whispering gallery modes with different physical parameters of hollow microspheres: a theoretical study

Herein, we report the theoretical investigation on whispering gallery modes (WGMs) of dielectric hollow microspheres (hollow core-shell microspheres) illuminated by plane wave and focused Gaussian beam (FGB). In the case of plane wave illumination, the wavelength sensitivity of the WGMs with different parameters of the hollow microspheres such as radii of the core and the shell, refractive indices of the core and the shell, and shell thickness is studied systematically. The variation in the electric field and quality factor of the WGMs with the above-mentioned parameters is also investigated. In the case of FGB illumination, the effect of beam waist on the characteristic parameters of the WGMs is studied. Later, the merits of the core-shell microspheres for the refractive index sensing applications over the solid microspheres are explained. Finally, the characteristic parameters of the WGMs of solid core-shell microspheres are studied.

Synthesis of ZnO core/shell hollow microspheres to boost light harvesting capability in quantum dots-sensitized solar cell

Although ZnO hollow microspheres (HMS) is beneficial to improving light scattering, this superiority is crippled by poor specific surface area of ZnO HMS. We designed ZnO core/shell hollow microspheres (CSHMS) by carbonaceous microspheres template method for application in QDSSC. In comparison to ZnO nanoparticles (NPs) and ZnO HMS, ZnO CSHMS increased QDs loadings and enhanced light scattering, leading to the boost of light harvesting capability and photovoltaic performance. As a result, the power conversion efficiency of QDSSC based on ZnO CSHMS is 76.22% and 21.74% higher than QDSSCs based on ZnO NPs and ZnO HMS, respectively.

Narrow range of zinc oxide core–shell hollow microspheres dopings for mechanical tensile promotion of 110KBPSCCO superconductor

Although substitutions on copper sites always inhibit superconducting properties, the present investigations were successfully promoted mechanical tensile averages for HTc-2223- BPSCCO superconductor with general formula BiPbSr2Ca2Cu3-x(Zn)xO10±δ where x = 0.02, 0.04,0.08 and 0.16 mol respectively in the investigated range without damaging its superconducting features. The study is focusing on the effect of core-shell zinc ions hollow microspheres dopings (x) on the copper sites, where 0 ≤ x ≤ 0.16 mol on the superconducting, mechanical tensile features of 110K-2223-BPSCCO superconductor. The structural and micro-structural features of pure and core shell Zn-doped BPSCCO superconductors samples were carefully investigated by x-ray diffraction (XRD) and scanning electron microscope (SEM). Mechanical tensile measurement indicated that doping ratio (x) with ~0.08 mol is the optimum doping ratio from core shell hollow zinc microspheres achieving maximum tensile average of 51.2 MPa with stroke~0.323 mm acheiving promotion ratio~63.57% in contrast with mechanical tensile measured for pure 2223- BPSCCO superconductor (31.3 MPa with stroke~0.172 mm).

SnO2 core-shell hollow microspheres co-modification with Au and NiO nanoparticles for acetone gas sensing

SnO2 core-shell hollow microspheres co-modified with Au and NiO nanoparticles (Au-NiO@SnO2) were successfully fabricated for use as an acetone gas sensor. The SnO2 core-shell hollow microspheres were prepared by a facile chemical precipitation method using tin tetrachloride pentahydrate (SnCl4·5H2O) and 4-methylimidazole as the primary raw materials. The co-modification with Au and NiO nanoparticles was carried out by a simple chemical reduction approach. Compared with Au@SnO2, NiO@SnO2, and pure SnO2, the Au-NiO@SnO2 core-shell hollow microspheres exhibited enhanced gas sensing properties toward acetone including high response, fast response-recovery speed, good selectivity, low detection limit, and work stability. The improved gas sensing performance was attributed to the unique SnO2 core-shell hollow microsphere structure, the p-n heterojunction between NiO and SnO2, and the catalytic action of Au nanoparticles.

Lychee-like ZnO/ZnFe2O4 core-shell hollow microsphere for improving acetone gas sensing performance

Uniformly lychee-like ZnO/ZnFe2O4 core-shell hollow microspheres with average size of 2.5 μm were successfully synthesized via one-step solvothermal self-assembly route. The core-shell hollow microspheres possessed mesoporous structure with a pore size of about 8.8 nm and the large specific surface area of approximately 54.0 m2/g. The effect of the Zn2+ concentration on the structure, morphology and gas-sensing property of the as-prepared samples were investigated by a series of testing techniques. The gas-sensing results demonstrated that the sensors based on core-shell ZnO/ZnFe2O4 hollow microspheres showed superior gas-sensing response, rapid response-recovery to low-ppm acetone. These excellent properties might be mainly owing to the unique core-shell structure, the large specific surface area, high concentration of oxygen vacancies and the synergetic effect between ZnO and ZnFe2O4. Hence, this material can be utilized as promising gas-sensing materials in the acetone detection.

VO2(D) hollow core–shell microspheres: synthesis, methylene blue dye adsorption and their transformation into C/VOxnanoparticles

Hollow core–shell VO2(D) microspheres were fabricated and they exhibited excellent MB adsorption ability; and the regenerated C/VOxnanoparticles showed enhanced adsorption performance and good reusability.

Urchin-like α-FeOOH@MnO2 core–shell hollow microspheres for high-performance supercapacitor electrode

This work details the design and synthesis of novel urchin-like α-FeOOH@MnO2 core–shell hollow microspheres for high-performance electrode materials for supercapacitors. The core–shell heterostructures were constructed by growing strip-like MnO2 nanostructures onto the urchin-like α-FeOOH hollow microspheres that were composed of nanorods. Based on the synergetic effects and multi-functionalities of both the MnO2 shell and urchin-like α-FeOOH hollow cores, the resulting urchin-like α-FeOOH@MnO2 core–shell hollow microspheres exhibited excellent electrochemical performance with a high specific capacitance of 597 F g−1 at 1 A g−1, good rate capability (capacitance retention of 74.2% at 10 A g−1), and remarkable cycling stability (capacitance retention of 97.1% after 2000 cycles). Moreover, an asymmetric supercapacitor fabricated using α-FeOOH@MnO2 as positive electrode and activated carbon as negative electrode was found to deliver a high energy density of 34.2 W h kg−1 and power density of 815 W kg−1. Urchin-like α-FeOOH@MnO2 hollow microspheres demonstrated a high specific capacitance, rate capability and cycling stability, suggesting its promising potential for high-performance supercapacitors.

General synthesis of metal oxide hollow core–shell microspheres as anode materials for lithium-ion batteries and as adsorbents for wastewater treatment

Hollow core–shell structures have many advantages, but their synthesis remains challenging. In this report, we demonstrate a general method for the preparation of a series of metal oxide hollow core–shell microspheres, including Co3O4, NiO and Mn2O3. The hollow core–shell microspheres were prepared via a coordination precipitation route followed by a calcination process. The morphology and microstructures of the metal oxide hollow core–shell microspheres could be controlled by optimizing the experimental conditions. A possible formation mechanism of the hollow core–shell structure was proposed. As anode materials for lithium ion cells, the Co3O4 hollow core–shell microspheres exhibited superior Li+ storage properties. When applied as adsorbents in water treatment, the NiO hollow core–shell microspheres showed an excellent ability to remove organic pollutants.

Nd1–xCaxFeO3 (x = 0, 0.3) Hollow Core–Shell Microspheres for Ethanol Gas Sensing

AbstractThe use of mesoporous and hollow structures is a promising strategy to enhance gas‐sensing properties. The framework of perovskite oxides has the ability to accommodate different cations, which endows it with rich oxygen deficiencies for preferable gas adsorption. Herein, we outline the fabrication of perovskite Nd1–xCaxFeO3 (x = 0, 0.3) hollow core–shell microspheres by using carbonaceous microspheres as templates. The gas‐sensing properties of Nd0.7Ca0.3FeO3 core–shell microspheres were systematically investigated. The response to 500 ppm ethanol was 17 at 140 °C, which is much higher than the response of Nd0.7Ca0.3FeO3 nanoparticles. Also, rapid response and recovery characteristics were achieved. Furthermore, after 50 cyclic tests and 10 testing days, the gas response of the Nd0.7Ca0.3FeO3 hollow core–shell microspheres to 500 ppm ethanol at 140 °C was nearly constant. The long‐term stability, good sensitivity, and rapid response and recovery times demonstrate the potential application of these hollow core–shell microspheres as a sensing material.

Synthesis of Fe3O4-NPs/SiO2 core-shell hollow microspheres and application in water treatment

Fe3O4-nanoparticles/polystyrene (Fe3O4-NPs/PS) composite microspheres were synthesized using a modified dispersion polymerization method. The distribution and content of Fe3O4-NPs in the microspheres were studied. Using the Fe3O4-NPs/PS microspheres as templates, Fe3O4-NPs/SiO2 core-shell hollow microspheres with excellent magnetic property and large cubage were synthesized facilely. The obtained Fe3O4-NPs/SiO2 core-shell hollow microspheres had a potential application in detoxification extraction and rapid waste removal with a very simple procedure.

Core-shell hollow microspheres of magnetic iron oxide@amorphous calcium phosphate: synthesis using adenosine 5'-triphosphate and application in pH-responsive drug delivery.

Drug nanocarriers with magnetic targeting and pH-responsive drug-release behavior are promising for applications in controlled drug delivery. Magnetic iron oxides show excellent magnetism, but their application in drug delivery is limited by low drug-loading capacity and poor control over drug release. Herein, core-shell hollow microspheres of magnetic iron oxide@amorphous calcium phosphate (MIO@ACP) were prepared and investigated as magnetic, pH-responsive drug nanocarriers. Hollow microspheres of magnetic iron oxide (HMIOs) were prepared by etching solid MIO microspheres in hydrochloric acid/ethanol solution. After loading a drug into the HMIOs, the drug-loaded HMIOs were coated with a protective layer of ACP by using adenosine 5'-triphosphate (ATP) disodium salt (Na2 ATP) as stabilizer, and drug-loaded core-shell hollow microspheres of MIO@ACP (HMIOs/drug/ACP) were obtained. The as-prepared HMIOs/drug/ACP drug-delivery system exhibits superparamagnetism and pH-responsive drug-release behavior. In a medium with pH 7.4, drug release was slow, but it was significantly accelerated at pH 4.5 due to dissolution of the ACP shell. Docetaxel-loaded core-shell hollow microspheres of MIO@ACP exhibited high anticancer activity.

Solvothermal synthesis of Co3O4/Al2O3 hollow core–shell microspheres for the catalytic oxidation of CO

Co3O4/Al2O3 hollow core–shell microspheres, which exhibit a large surface area, a mesoporous structure and an excellent CO catalytic performance, have been synthesized by a solvothermal process.

Control of Structure of Au@TiO2 Core–Shell Hollow Microspheres with Multiple Nanocores and Porous Shells

Abstract Au@TiO2 core–shell hollow microspheres with multiple nanocores and porous shells have been synthesized by a simple and effective hydrothermal method using TiF4 as TiO2 precursor. The size of microsphere can be controlled by changing synthetic conditions.

The preparation and high-frequency electromagnetic properties of ferrimagnetic bisphthalonitrile–Fe3O4 core–shell hollow microspheres

A novel kind of ferrimagnetic core–shell hollow microsphere was prepared by a two-step solvothermal method with bisphthalonitrile and FeCl3. Scanning electron microscope and transmission electron microscope images show that the diameter of hollow microsphere is about 320nm and the hollow microspheres are made of small Fe3O4 nanoparticles.Compared with traditional pure Fe3O4 nanoparticles, the hollow microspheres exhibited very strong magnetism due to their special structures. The saturation magnetization and coercivity of the ferrimagnetic hollow microspheres were 103.9emug−1 and 161.6Oe, respectively. The electromagnetic properties of hybrids showed cooperative nonlinear magnetic and dielectric resonance in Ku-band. Moreover, the hybrid hollow microspheres also showed electromagnetic shielding characteristics in Ku-band. Three nesting reflection loss peaks can be seen around 13.0, 16.0 and 17.3GHz. A minimum reflection loss of −38.5dB was reached at 17.3GHz with an absorber thickness of 4.2mm.

Preparation of core–shell poly(l-lactic) acid-nanocrystalline apatite hollow microspheres for bone repairing applications

In this paper, hybrid inorganic-organic core-shell hollow microspheres, made of poly(L-lactic acid) (PLLA) and biomimetic nano apatites (HA), were prepared from biodegradable and biocompatible substances, suitable for bone tissue applications. Preparation is started from Pickering emulsification, i.e., solid particle-stabilized emulsions in the absence of any molecular surfactant, where solid particles adsorbed to an oil-water interface. Stable oil-in-water emulsions were produced using biomimetic 20 nm sized HA nanocrystals as particulate emulsifier and a dichloromethane (CH(2)Cl(2)) solution of PLLA as oil phase. Hybrid hollow PLLA microspheres at three different HA nanocrystals surface coverage, ranging from 10 to 50 μm, were produced. The resulting materials were completely characterized with spectroscopic, calorimetric and microscopic techniques and the cytocompatibility was established by indirect contact tests with both fibroblasts and osteoblasts and direct contact with these latter. They displayed a high level of cytocompatibility and thus represent promising materials for drug delivery systems, cell carriers and scaffolds for regeneration of bone useful in the treatment of orthopaedic, maxillofacial and dental fields.

Room temperature synthesis of zinc hydroxystannate hollow core-shell microspheres and their hydrothermal growth of hollow core-shell polyhedral microcrystals

In this study, a room temperature NH3 bubble templating technique is developed to prepare zinc hydroxystannate [ZnSn(OH)6] hollow core-shell microspheres. Then, via a hydrothermal recrystallizing process, ZnSn(OH)6 hollow core-shell microcrystals with polyhedral morphology can be successfully obtained. It was found that the concentration of NH4F plays a crucial role in the morphology of the product. The optimal condition for the formation of hollow core-shell ZnSn(OH)6 microcrystals is that the concentration of NH4F is at 0.25 mol L−1 while the concentration of NaOH is fixed at 0.25 mol L−1. Reaction time has also a great influence on the morphology of the product. With the reaction time prolonged, hollow core-shell ZnSn(OH)6 microspheres would gradually crystallize into hollow core-shell ZnSn(OH)6 polyhedral microcrystals. The samples have been characterized by means of X-ray power diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectra (XPS), selected area electron diffraction (SAED) and transmission electron microscopy (TEM). The formation mechanism of the ZnSn(OH)6 hollow core-shell microcrystals with polyhedral morphology has been discussed based on the experimental results.

Zinc oxide core–shell hollow microspheres with multi-shelled architecture for gas sensor applications

A new type of spherically multilayered core–shell structure was prepared via a simple hard template strategy in the case of ZnO. The structure and morphology characteristics of the resultant product were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The ZnO microspheres with hollow interior and porous shells are multilayered structures with diameters ranging from 0.4 to 3.5 μm. Further investigation of the formation mechanism reveals that the preheating program is vital to the formation of the multishelled structures. To demonstrate the usage of such a multilayered nanomaterial, a chemical gas sensor has been fabricated and investigated for toluene detection. The sensor exhibits excellent sensing performances in terms of high response, low detection limit, rapid response-recovery, and superior selectivity.