Hybrid Hollow Microspheres Research Articles

Synthesis of Oxygen‐Deficient WO3−x Nanoplates and Hollow Microspheres Decorated on a Carbon Cloth for Supercapacitors

AbstractOxygen‐deficient CC−WO3−x nanoplates and hollow microspheres on carbon fabrics cloth were synthesized utilizing a simple solvent‐thermal route. The obtained CC−WO3−x possess an improved electronic conductivity because of the oxygen‐deficient effect and a higher specific surface area due to the unique nano‐structural features. The CC−WO3−x exhibits a high capacitance of 804 F g−1, excellent rate performance (>80 %) while the current density is enhanced five‐fold and superior cycling stability by retaining 109.5 % after 14000 cycles at 30 mV s−1. In addition, an asymmetric electrochemical capacitor (ASC) reveals a competitive energy storage performance (50.7 W h kg−1 at 1.3 KW kg−1). The reasons for its good electrochemical property are that the novel hybrid nanoplates and hollow microspheres structure with oxygen‐deficient and binder‐free, which is conducive to exposing more electroactive sites and enhancing electrical conductivity, therefore accelerating ion diffusion, facilitating charge transportation, and promoting the capacitive contribution for rapid charge‐discharge kinetics synchronously.The route is anticipated to reveal a new way to prepare hybrid nanostructure with oxygen‐deficient and binder‐free metal oxide‐based electrode material.

Fe3O4 Nanoparticle/N-Doped Carbon Hierarchically Hollow Microspheres for Broadband and High-Performance Microwave Absorption at an Ultralow Filler Loading.

Although the existing Fe3O4-based microwave absorbing materials (MAMs) have shown promising microwave absorbing (MA) capacity, it is highly desired but still remains a great challenge to achieve strong minimum reflection loss (RLmin) and broad effective frequency bandwidth (fe) at an ultralow filler loading. Herein, for the first time, by carbonizing hierarchical poly(urea-formaldehyde) microcapsules with Fe3O4 nanoparticle cores in a nitrogen atmosphere, Fe3O4 hybrid and N-doped hollow carbon microspheres (Fe3O4/CMs) with a hierarchical micro/nanostructure are prepared on a large scale and at a low cost to achieve extremely superior MA performances. Benefitting from their unique structure and diverse composition, which synergetically contribute to good impedance matching, strong dielectric/magnetic loss, and abundant multiscattering/reflection, Fe3O4/CM composites possessed a RLmin value reaching -60.3 dB and an fe of as broad as 6.4 GHz (7.2-13.6 GHz, covering the full X-band) at an ultralow filler loading of 10 wt % in paraffin wax, which are significantly superior to those of the previously reported state-of-the-art Fe3O4-based or hollow MAMs. Furthermore, the fe can be adjusted in the range of 4.5-18 GHz, covering 85% of the whole measured frequency range, via changing the thickness between 2.5 and 5.5 mm. This work offers new insights for developing advanced lightweight MAMs with strong absorption and a broad absorbing frequency range at a low filler loading.

In-situ preparation of hollow cellulose nanocrystals/zeolitic imidazolate framework hybrid microspheres derived from Pickering emulsion

In situ interfacial growth of nanoparticles induced by a Pickering emulsion is recognized as a practical method for the fabrication of hollow composites. Herein, hybrid hollow microspheres were prepared using cellulose nanocrystals (CNCs) emulsified water-dodecane system as a template. The hybrid microspheres were composed of zeolitic imidazolate framework-8 (ZIF-8) shells and CNCs surface-layers. ZIF-8 crystals formed and grew at the oil-water interface with a low ligand/metal ion molar ratio. The composite microspheres owned rich porous structure with a high surface area of 1240 m2 g−1 and performed obvious hydrophilicity owing to the role of CNCs layers. The two characters offered CNCs/ZIF-8 composite materials with very prominent adsorption capacity towards dyes (1060.2 mg g−1 for malachite green). Carbonization of CNCs/ZIF-8 composite materials afford ZIF-8 based materials more effective removal of methylene blue from water under sunlight, owing to the photocatalytic role of ZnO remained in carbonized product. This research paves the way to realize a variety of hollow CNCs/ZIFs hybrid materials for different application purposes.

Hierarchical MoS2/NiCo2S4@C urchin-like hollow microspheres for asymmetric supercapacitors

Metal sulfides are intensively studied as one of the most predominant materials for supercapacitors owing to such unique advantages as low-cost, low electronegativity and high electrochemical activity, and the appropriate architecture of hybrid metal sulfides is believed to be very effective for fully utilizing their material merits and breaking through their limits of the low-rate capability and inferior cycling stability in supercapacitor applications. Herein, a high-performance supercapacitor based on carbon-coated MoS2/NiCo2S4 urchin-like hollow hybrid microspheres (MoS2/NiCo2S4@C HMSs) is prepared by a facile self-template method. And the high specific capacity of 250 mAh g−1 at 2 A g−1 and ultra-high rate capability of 91.1% at 40 A g−1 achieved with the resultant MoS2/NiCo2S4@C HMSs due to their hierarchical hollow hybrid structure and the protection from the coated carbon thin layer. With the MoS2/NiCo2S4@C HMSs as the positive electrode and active carbon as the negative electrode, asymmetric supercapacitors (ASCs) have been assembled, which exhibit a high energy density of 53.01 Wh kg−1 at the power density of 4.20 kW kg−1, an energy density of 36.46 Wh kg−1 even at the ultra-high power density of 73.75 kW kg−1, and excellent cycling stability of 90.1% after 10 000 cycles of charge–discharge tests at the current density of 10 A g−1.

Nitrogen functionlized graphene quantum dots/3D bismuth oxyiodine hybrid hollow microspheres as remarkable photoelectrode for photoelectrochemical sensing of chlopyrifos

This work presents a selective and reliable visible-light driven photoelectrochemical (PEC) chlopyrifos sensor using nitrogen functionalized graphene quantum dots/3D bismuth oxyiodine (NFGQDs/3DBiOI) hybrid hollow microspheres (HHMs) as a remarkable photoelectrode. In this protocol, a facile one-pot solvothermal reaction was used for the synthesis of the new NFGQDs/3DBiOI HHMs, which achieved significant enhancement (ca. 18-fold) photocurrent generation compared to pure BiOI microspheres by virtue of the band gap narrowing and the electron transfer acceleration of such HHMs. In addition, the introduction of chlorpyrifos pesticide enabled the formation of Bi-chlorpyrifos complex which resulted in quenching the charge transfer efficiency, thus leading to a decrease in photocurrent intensity and selective PEC recording of chlorpyrifos level. This novel PEC sensor exerted predominant performance for chlorpyrifos detection including wide linear range (0.1–50 ng mL−1), low detection limit (0.03 ng mL−1), satisfactory selectivity and also good feasibility in real water sample analysis. The strategy presented here implying that a three-dimensional hollow nanostructure would play a crucial role in developing multifarious novel detection methodologies in PEC sensing fields.

Effect of hybrid hollow microspheres on thermal insulation performance and mechanical properties of silicone rubber composites

ABSTRACTHollow microspheres (HM) of ceramic, silica, and glass‐filled silicone rubber (SR) composites were prepared, and the effects of hybrid HM on thermal and mechanical properties of composites were investigated. The results indicate that hybrid HM can effectively improve the thermal insulation property of HM/SR composites. Especially, for sample 15S, the thermal conductivity and thermal degradation temperature reached 0.1273 W/m K and 521 °C (45 °C higher than that of neat SR), respectively. Besides, thermal insulation performance was improved, showing as a temperature of 103.2 °C after 15 min heating, which is 37.8 °C lower than that of SR. The tensile strength of composites was enhanced from 1.92 MPa at 11.56 vol % hollow silica microspheres (HSM) loading to 3.08 MPa at 21.88 vol % HSM loading. Moreover, the compressive strength was improved from 3.33 to 5.68 MPa by introducing more hollow ceramic microspheres into the matrix, in this case, from 7.79 to 15.33 vol %. Furthermore, the failure mechanism was analyzed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46025.

Self-templating synthesis of nitrogen doped graphene quantum dots/3D bismuth oxyiodine hybrid hollow microspheres with improved visible-light excited photocurrent generation: Simultaneous electron transfer acceleration and bandgap narrowing

This work presents a self-templating synthetic approach for the synthesis of nitrogen doped graphene quantum dots/3D bismuth oxyiodine (NGQDs/3DBiOI) hybrid hollow microspheres (HHMs) by a facile one-pot solvothermal reaction. In this protocol, the formation of NGQDs/3DBiOI hollow microstructure and the hybridization of NGQDs with BiOI semiconductor were achieved simultaneously in one-pot reaction using the NGQDs as template and dopant, which played a double-acting role in the reaction: (i) to modulate the morphology of BiOI microspheres with special hollow structure; (ii) to hybrid with BiOI for the formation of NGQDs/3DBiOI HHMs. Further investigations revealed that the resulted NGQDs/3DBiOI HHMs exhibit tunable visible-light driven photocurrent generation with varying the amount of NGQDs used in the reaction process, which was ascribed to the simultaneous electron transfer acceleration and bandgap narrowing of the NGQDs/3DBiOI HHMs. Moreover, when evaluated as a matrix for enzyme encapsulation, the resulting NGQDs/3DBiOI HHMs exhibited enhanced load capacity than pure BiOI microspheres by virtue of their particular nanostructure. The design of such three-dimensional NGQDs/3DBiOI HHMs with preferable performance facilitates further multifarious applications for enhanced photocatalysis, enzyme immobilization and biofuels.

Synthesis of ZnO-Cu-C yolk-shell hybrid microspheres with enhanced electrochemical properties for lithium ion battery anodes

Zinc-copper citrate porous, yolk-shell and hollow microspheres are controllably produced via a facile electrostatic interplay between zinc citrate solid microspheres and copper sulphate solution with controllable concentration. By calcination of the firstly acquired zinc-copper citrate precursors in inert atmosphere, the corresponding ZnO-Cu-C porous, yolk-shell and hollow hybrid microspheres are synthesized. When adopted as the electrode materials for lithium ion batteries, the produced ZnO-Cu-C yolk-shell hybrid microspheres depict higher reversible capacity and better cycling stability than ZnO-Cu-C porous hybrid microspheres. After 500 cycles at 200mAg−1, yolk-shell hybrids deliver a reversible capacity of 769mAhg−1. Additionally, ZnO-Cu-C hollow hybrid microspheres exhibit best rate capability, which is due to their special three dimensional Cu conductive network.

Controlled Formation of Li4Ti5O12-C Hollow Hybrid Microspheres for an Improved Battery Performance in Lithium Ion Batteries

The In this contribution, we reported our progress on the construction and optimization of the hybrid structure of Li4Ti5O12-Carbon (LTO-C) for their application as an anode material in lithium ion batteries. By means of a template-free process, uniform hollow hybrid microspheres (HHMs) of LTO-C has been prepared with delicate control on the central cavity and the nanocomposite wall, which was composed of a crystalline LTO matrix with conductive carbon well dispersed inside. The synthesis protocol for LTO-C was very convenient, low-cost, environmentally benign, and suitable for large-scale production. We identified that the hollowing process is induced by the gradual crystallization of solid microspheres whose crystallinity was relatively low at the beginning. The high temperature treatment initiated a progressively-inward crystallization starting from the particle surface: Crystallization firstly happened on the surface, and then marched into the core as evidenced by a steady encroachment of the crystallization frontline towards the center, resulting in the formation of the central cavity due to the increased tension inside. We demonstrated that such a synthetic platform for hollow microspheres were versatile and could be readily applicable for the synthesis of different kinds of metal oxides HHMs. By using the LTO-C as an anode material, we confirmed the advantage of the HHMs structure for their application in lithium ion batteries as revealed by the much higher discharge capacity and much improved rate capability. Figure 1: a) SEM images of the TiO2-UF precursors which exist as uniform solid nanospheres. b) SEM image of the FIB-prepared cross section of the LTO-C HHMs sample, showing the hollow nature of the inner particles. c) The first charge/discharge curves at 0.1 C for different samples tested, showing the advantage of the LTO-C HHMs one as compared to those control samples with either no cavity or no carbon matrix. d) Cyclablity test results for different samples. Figure 1

General Synthetic Strategy for Hollow Hybrid Microspheres through a Progressive Inward Crystallization Process.

Hollow hybrid microspheres have found great potential in different areas, such as drug delivery, nanoreactors, photonics, and lithium-ion batteries. Here, we report a simple and scalable approach to construct high-quality hollow hybrid microspheres through a previously unexplored growth mechanism. Starting from uniform solid microspheres with low crystallinity, we identified that a hollowing process can happen through the progressive inward crystallization process initiated on the particle surface: the gradual encroachment of the crystallization frontline toward the core leads to the depletion of the center and forms the central cavity. We showed that such a synthetic platform was versatile and can be applicable for a large variety of materials. By using the production of Li4Ti5O12-carbon hollow hybrid microspheres as an example, we demonstrated that high-performance anode materials could be achieved through synthesis and structure control. We expect that our findings offer new perspectives in different areas ranging from materials chemistry, energy storage devices, catalysis, to drug delivery.

Aerosol synthesis of Graphene-Fe3O4 hollow hybrid microspheres for heterogeneous Fenton and electro-Fenton reaction

Fenton reaction has been widely used to treat wastewater containing dyes, herbicides, antibiotics, and landfill leachate because of its convenience and strong oxidation ability. The rational design and preparation of efficient and stable Fenton catalysts have been the focus of research. In this study, graphene-magnetite hollow hybrid microspheres were synthesized by a facile aerosolized spray drying route utilizing ferric ion and graphene oxide (GO) solution as the precursor. The results showed that uniform hybrid microspheres with possess hollow structure, high saturation magnetization and high Fenton catalytic activity with 30wt% graphene (30G-FeO) as catalyst. By the electrochemical analysis, a two-electron dominated process has been demonstrated to explain higher electrocatalytic activity. Accordingly, a novel electro-Fenton (EF) system with the 30G-FeO cathode was established working at acidic condition. The 30G-FeO cathode material possessed highly EF catalytic activity after prolonged cycling. Inspired by the wonderful intrinsic properties and the easy fabrication procedure, the as-prepared 30G-FeO could be promising candidates as potential cathodic materials for high-performance EF oxidation.

Magnetically separable and recyclable Fe3O4–polydopamine hybrid hollow microsphere for highly efficient peroxidase mimetic catalysts

Magnetic Fe3O4–polydopamine (PDA) hybrid hollow microspheres, in which Fe3O4 nanoparticles were firmly incorporated in the cross-linked PDA shell, have been prepared through the formation of core/shell PS/Fe3O4–PDA composites based on template-induced covalent assembly method, followed by core removal in a tetrahydrofuran solution. The morphology, composition, thermal property and magnetic property of the magnetic hybrid hollow microspheres were characterized by SEM, TEM, FT-IR, XRD, TGA, and vibrating sample magnetometer, respectively. Results revealed that the magnetic hybrid hollow microspheres had about 380nm of inner diameter and about 30nm of shell thickness, and 13.6emug−1 of magnetization saturation. More importantly, the Fe3O4–PDA hybrid hollow microspheres exhibited intrinsic peroxidase-like activity, as they could quickly catalyze the oxidation of typical substrates 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. Compared with PDA/Fe3O4 composites where Fe3O4 nanoparticles were loaded on the surface of PDA microspheres, the stability of Fe3O4–PDA hybrid hollow microspheres was greatly improved. As-prepared magnetic hollow microspheres might open up a new application field in biodetection, biocatalysis, and environmental monitoring.

Recyclable SERS substrates based on Fe2O3–Ag hybrid hollow microspheres with crumpled surfaces

Fe2O3–Ag hybrid hollow microspheres with crumpled surfaces were prepared as SERS recyclable substrates for 4-aminobenzenethiol (4-ABT) and toxin protein ricin.

Electrostatic Assembly of Sandwich-like Ag-C@ZnO-C@Ag-C Hybrid Hollow Microspheres with Excellent High-Rate Lithium Storage Properties.

Herein, we introduce a facile electrostatic attraction approach to produce zinc-silver citrate hollow microspheres, followed by thermal heating treatment in argon to ingeniously synthesize sandwich-like Ag-C@ZnO-C@Ag-C hybrid hollow microspheres. The 3D carbon conductive framework in the hybrids derives from the in situ carbonation of carboxylate acid groups in zinc-silver citrate hollow microspheres during heating treatment, and the continuous and homogeneous Ag nanoparticles on the outer and inner surfaces of hybrid hollow microspheres endow the shells with the sandwiched configuration (Ag-C@ZnO-C@Ag-C). When applied as the anode materials for lithium ion batteries, the fabricated hybrid hollow microspheres with sandwich-like shells reveal a very large reversible capacity of 1670 mAh g(-1) after 200 cycles at a current density of 0.2 A g(-1). Even at the very large current densities of 1.6 and 10.0 A g(-1), the high specific capacities of about 1063 and 526 mAh g(-1) can be retained, respectively. The greatly enhanced electrochemical properties of Ag-C@ZnO-C@Ag-C hybrid microspheres are attributed to their special structural features such as the hollow structures, the sandwich-like shells, and the nanometer-sized building blocks.

Layer-by-Layer Engineered Superparamagnetic Polyelectrolyte Hybrid Hollow Microspheres With High Magnetic Content as Drug Delivery System

Polyelectrolyte hybrid hollow microspheres with sandwich structure of about 450 nm have been accomplished by layer-by-layer self-assembling of two modified ferroferric oxide nanoparticles, lysine modified ferroferric oxide nanoparticles (Fe3O4-LYs) and citrate modified ferroferric oxide nanoparticles (Fe3O4-CA), as the main assembling materials via electrostatic interaction for the first time. They are superparamagnetic with saturation magnetization of 45.69 emu/g, revealing their high magnetic content of 70%. As drug delivery system, they also exhibited pH-stimuli responsive controlled release of an anticancer drug doxorubicin, following the Fickian diffusion model. Their unique structure and high magnetic content make them good candidate for targeted delivery.

Preparation and Application of Functional Inorganic/Polymer Hollow Microspheres Via Double In Situ Mini-Emulsion Polymerization

Silica/polymer hollow microspheres were prepared via double in situ mini-emulsion polymerization by taking advantage of phase separation between the growing polymer and inorganic TEOS phase. Then hybrid hollow microspheres were surface modified by the addition of GMA during the process of polymerization. The obtained surface–functional hybrid hollow microspheres were applied as a filler in polysulfide sealant system. The inorganic/polymer hollow microspheres were characterized by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric/derivative thermal gravimetric analysis (TGA/DTG), and thixotropic experiment, respectively. The results showed that the as-prepared inorganic/polymer microspheres had a hollow structure and the size was in the range of 200–600 nm. The thixotropy and heat resistance properties of polysulfide sealant were improved after the addition of hybrid hollow microspheres.

Synthesis of ZnO–ZnCo2O4 hybrid hollow microspheres with excellent lithium storage properties

ZnO–ZnCo2O4 hybrid hollow microspheres are successfully produced via an annealing process of the pre-fabricated zinc–cobalt citrate hollow microspheres in air. ZnO and ZnCo2O4 have homogeneous distribution within the whole hollow microspheres. The gained hybrid hollow microspheres deliver outstanding lithium storage properties when utilized as the anode material in lithium ion batteries. A high reversible capacity of 1199mAhg−1 can be retained after 200 cycles. The exceptional electrochemical properties of the hybrid hollow microspheres are ascribed to the synergetic effect between ZnO and ZnCo2O4 nanoparticles, the catalytic effect of Co nanocrystals, the favorable hollow structures together with the nanometer-sized building blocks of hybrid microspheres.

Preparation of Silica Hollow Composite Particles

A facile and effective approach has been developed to prepare hybrid hollow microspheres, via consecutive processes of pickering mini-emulsion polymerization for core-shell formation, and calcination of the sacrificial core. The resulting hollow composite particles have mono-layered shells. The morphology and size characteristics of synthesized composite particles were investigated, using dynamic light scattering (DLS) and scanning electron microscopy (SEM) measurements.

Novel biocompatible pH-stimuli responsive superparamagnetic hybrid hollow microspheres as tumor-specific drug delivery system

Novel biocompatible pH-stimuli responsive superparamagnetic hybrid hollow microspheres have been designed via the layer-by-layer (LbL) self-assembly technique via the electrostatic interaction between the poly(ethylene glycol) grafted chitosan (CS-g-PEG) as polycation and the citrate modified ferroferric oxide nanoparticles (Fe3O4–CA) as hybrid anion onto the uniform polystyrene sulfonate (PSS) microsphere templates. The well-defined hybrid hollow microspheres ((CS-g-PEG/Fe3O4–CA)4/CS-g-PEG) were obtained after etching the templates by washing with DMF. They possessed superparamagnetic characteristics with a saturation magnetization of 37.23emu/g, and exhibited excellent stability in high ion-strength media and pH dependent DOX release. Their unique structure and outstanding performance make them potential platform for tumor-specific delivery in the tumor diagnostic and therapy.

Template synthesis of graphene/polyaniline hybrid hollow microspheres as electrode materials for high-performance supercapacitor

Graphene/polyaniline hybrid hollow microspheres are prepared via combining layer-by-layer assembly technique with in situ chemical oxidative polymerization after etching the templates for high-performance supercapacitor application. The hollow structure is characterized by transmission electron microscopy indicating that the inner diameter of the hollow microspheres is about 2.0 µm. The electrochemical tests show that the specific capacitance of the graphene/polyaniline hybrid hollow microsphere electrode materials can reach about 633 F g−1 in a 1.0 M H2SO4 electrolyte. It is higher than that of polyaniline hollow microspheres (389 F g−1), pure polyaniline particles (152 F g−1), and graphene/sodium alginate hollow microspheres (16 F g−1). The high specific capacitance might be attributed to the unique hollow structure and the synergistic effect of the hybrid shell. Their unique structure provides an enhanced surface-to-volume ratio and reduced transport lengths for both mass and charge transport. Furthermore, graphene/polyaniline hybrid hollow microsphere electrode materials display good cycle stability with 92 % of its original specific capacitance after 1,000 cycles by continuous cyclic voltammetric scans at 80 mV s−1.