Hollow Core-shell Structure Research Articles

Constructing a hollow core-shell structure of RuO2 wrapped by hierarchical porous carbon shell with Ru NPs loading for supercapacitor

Hollow core-shell structure nanomaterials have been broadly used in energy storage, catalysis, reactor, and other fields due to their unique characteristics, including the synergy between different materials, a large specific surface area, small density, large charge carrying capacity and so on. However, their synthesis processes were mostly complicated, and few researches reported one-step encapsulation of different valence states of precious metals in carbon-based materials. Hence, a novel hollow core-shell nanostructure electrode material, RuO2@Ru/HCs, with a lower mass of ruthenium to reduce costs was constructed by one-step hydrothermal method with hard template and co-assembled strategy, consisting of RuO2 core and ruthenium nanoparticles (Ru NPs) in carbon shell. The Ru NPs were uniformly assembled in the carbon layer, which not only improved the electronic conductivity but also provided more active centers to enhance the pseudocapacitance. The RuO2 core further enhanced the material's energy storage capacity. Excellent capacitance storage (318.5 F·g−1 at 0.5 A·g−1), rate performance (64.4%) from 0.5 A·g−1 to 20 A·g−1, and cycling stability (92.3% retention after 5000 cycles) were obtained by adjusting Ru loading to 0.92% (mass). It could be attributed to the wider pore size distribution in the micropores which increased the transfer of electrons and protons. The symmetrical supercapacitor device based on RuO2@Ru/HCs could successfully light up the LED lamp. Therefore, our work verified that interfacial modification of RuO2 and carbon could bring attractive insights into energy density for next-generation supercapacitors.

Construction, pH-responsive drug release and in vitro cytotoxicity of Ni@C nanotubes

Ni@C magnetic nanotubes surrounded by a carbon shell with thick of 10 nm were constructed using nickel nanotubes as core by glucose-solvothermal-method. The morphology, structure, composition, magnetic property, drug release behavior, in-vitro cytotoxicity and antitumor efficacy of the as-prepared Ni@C nanotubes were studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectrum, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, vibrating-sample magnetometer, UV–vis spectroscopy, CCK-8 assays and flow cytometry. The results indicated that the as-prepared Ni@C nanotubes had typical hollow core-shell structure, good magnetic property, pH-responsive drug-release functionality and better antitumor activity, compared with nickel nanotubes. It presented low in-vitro cytotoxicity originated in cell apoptosis by S-phase arrest, which made the magnetic Ni@C nanotubes potentially application in biomedicine.

Microelectronic structure changes electron utilization: Core-shell structure catalysts with electron library and quantum dots for photocatalytic hydrogen production

Photocatalysis is facing huge challenges especially the separation and efficient utilization of photocarriers. Herein, we report that a ternary hollow core–shell photocatalyst is synthesized by template and self-assembled method. The experimental results show that the electron separation efficiency and utilization efficiency are significantly improved, not only because the ternary hollow core–shell structure spatially separates the oxidation area MnOx from the reduction area Co-MOF, but also because lots of emergent electrons are stored in Co-MOF as an electronic library, contributing to the formation of surface polarization to support the requirement call from the CoP quantum dots (QDs) as active-sites. It’s the first report that the effectively separated electron-rich and electron-poor microelectronic states of the tunable Co-MOF promotes electron utilization by affecting the storage capacity of the electron library promoting photocatalytic hydrogen production. The tests show that Mn@Cd-CoP QDs/MCN (35.31 mmol/h/g), Mn@Cd-CoP QDs/BCN (23.69 mmol/h/g) and Mn@Cd-CoP QDs (11.08 mmol/h/g) have the better hydrogen production performances, which is about 38 times, 26 times and 12 times higher than CdS (0.9244 mmol/h/g), respectively. The pioneering exploration about the ternary hollow core–shell structure bonded with MOFs materials with abundant CoP QDs will open up a new perspective to design high-performance for solar-chemical energy conversion.

A high active sites exposed hollow Co@SiO2 nanoreactor for high performance fischer–tropsch synthesis

Optimizing catalyst geometry to break current limitations of Fischer-Tropsch synthesis (FTS) activity and the selectivity of long-chain hydrocarbons is a promising and challenging subject. Herein, a hollow Co@SiO2 catalyst with high dispersion of cobalt species anchored inside mesoporous hollow silica shell was successfully synthesized with the help of Co-metal organic framework materials, which displayed a surprisingly high C5+ hydrocarbons selectivity of 93.3% with a low methane selectivity of 3.4% at a remarkable high activity (CTY = 5.1 × 10-5 molCO gCo-1 s−1). The catalyst remained excellent stability for 200 h under industrially relevant conditions. The hollow core–shell structure provided an internal cavity environment that shortened the diffusion distance and contact area between Co metal and support, and improved exposed active cobalt sites and residence time of intermediates, inducing the growth of the catalytic activity and long-chain hydrocarbons selectivity. Protection of silica shell prevented the aggregation of active cobalt nanoparticles, further promoting the catalyst stability. This work provides a new insight into the design of high efficient and stable catalysts for FTS reaction.

Zeolitic imidazolate frameworks-derived hollow Co/N-doped CNTs as oxidase-mimic for colorimetric-fluorescence immunoassay of ochratoxin A

The rational design of high-performance nanozyme is of great significance in biosensors. Here, using zeolitic imidazolate framework-8 (ZIF-8) as the precursor, the Co nanoparticle/N-doped carbon nanotubes (Co/NCNT) with hollow core-shell structure were prepared by high temperature pyrolysis of ZIF-8@zeolitic imidazolate framework-67 (ZIF-8@ZIF-67), where ZIF-8@ZIF-67 was not only functionalized as the source of N and C for growth of NCNTs but also provided the template to form the hollow structures. Encapsulation of Co nanoparticles (NPs) in NCNT can effectively anchor active sites and avoid self-agglomeration. The synergistic effect of Co NPs and NCNT is beneficial to increasing the oxidase-mimicking activity significantly, while the hollow structure promotes the binding of the active sites with the substrate to increase the reaction rates. Hence, the Co/NCNT possessed oxidase-mimicking activity to catalyze colorless 3,3′,5,5′-tetramethylbenzidine (TMB) without H2O2, while the blue TMB+ can also quench the fluorescence of AuAg nanoclusters (NCs) by the internal filter effect. A colorimetric-fluorescence dual-mode immunosensor was established to achieve sensitive detection of ochratoxin A (OTA) in a linear detection range from 0.001 to 10 μg/L with a low detection limit of 0.21 ng/L (colorimetric) and 0.17 ng/L (fluorescence), respectively. Due to the independence and mutual corroboration of the signals, the dual-mode immunoassay is more accurate and reliable than the single-mode immunoassay for OTA. Significantly, the strategy lays a solid foundation for the design of MOF-based nanozymes and innovative inspiration in food visual analysis.

Size-and-thickness-dependent fracture patterns of hollow core–shell electrodes during lithiation

Conventional materials for lithium-based rechargeable batteries are reaching their limit. Material failure is also a huge barrier to fully exploit the potential. Novel design of nanomaterials provides possible solutions for these problems. However, the mechanism of material failure during lithiation/delithiation cycling is still not well understood. Here we develop a concurrently coupled chemo-mechanical model based on peridynamics to study the fracture-pattern formation of hollow core–shell structures during lithiation. We show that the geometric parameters of the nanostructures may profoundly influence the behaviors of dynamic fracture, i.e., different coating thicknesses and sizes of the nanotubes lead the cracks to branch in different directions, making them grow into different patterns. We investigate the stress state to explore the reason for the differentiation. A phase diagram for fracture patterns is constructed to have a systematic view. The results in this work provide a basis of designing the nanostructures of the electrode materials in the future.

Preparation of hollow mesoporous prussian blue coated with mesoporous silica shell nanocubes for photothermal therapy and drug carrier

The nanocubes with hollow mesoporous Prussian blue core and mesoporous silica shell (HMPB@mSiO2) were prepared. According to the SEM and TEM, the material showed a regular hollow core-shell cubic structure. Up to 879 m2/g of the surface area and 4.2 nm of average pore size were measured by N2 adsorption-desorption. The nanocubes exhibited excellent photothermal conversion efficiency under 808 nm NIR. The UV–vis spectrophotometry showed that the drug loading content of the materials were 868.27 μg/mg (drug/carrier) and which can accelerate the release of DOX under acidic and NIR conditions.

Preparation of Hollow Core-Shell Fe3O4/Nitrogen-Doped Carbon Nanocomposites for Lithium-Ion Batteries.

Iron oxides are potential electrode materials for lithium-ion batteries because of their high theoretical capacities, low cost, rich resources, and their non-polluting properties. However, iron oxides demonstrate large volume expansion during the lithium intercalation process, resulting in the electrode material being crushed, which always results in poor cycle performance. In this paper, to solve the above problem, iron oxide/carbon nanocomposites with a hollow core–shell structure were designed. Firstly, an Fe2O3@polydopamine nanocomposite was prepared using an Fe2O3 nanocube and dopamine hydrochloride as precursors. Secondly, an Fe3O4@N-doped C composite was obtained by means of further carbonization treatment. Finally, Fe3O4@void@N-Doped C-x composites with core–shell structures with different void sizes were obtained by means of Fe3O4 etching. The effect of the etching time on the void size was studied. The electrochemical properties of the composites when used as lithium-ion battery materials were studied in more detail. The results showed that the sample that was obtained via etching for 5 h using 2 mol L−1 HCl solution at 30 °C demonstrated better electrochemical performance. The discharge capacity of the Fe3O4@void@N-Doped C-5 was able to reach up to 1222 mA g h−1 under 200 mA g−1 after 100 cycles.

Synthesis of hollow core-shell ZnFe2O4@C nanospheres with excellent microwave absorption properties.

The special hollow core–shell structure and excellent dielectric-magnetic loss synergy of composite materials are two crucial factors that have an important influence on the microwave absorption properties. In this study, hollow ZnFe2O4 nanospheres were successfully synthesized by a solvothermal precipitation method firstly; based on this, a C shell precursor phenolic resin was coated on the ZnFe2O4 hollow nanospheres' surface by an in situ oxidative polymerization method, and then ZnFe2O4@C was obtained by high-temperature calcination. Samples were characterized by SEM, TEM, XRD, XPS, BET, VSM, VNA. The results show that the maximum reflection loss (RLmax) reaches −50.97 dB at 8.0 GHz, and the effective bandwidth (EAB) of hollow core–shell structure ZnFe2O4@C is 3.2 GHz (6.16–9.36 GHz) with a coating thickness of 3.5 mm. This work provides a useful method for the design of lightweight and high-efficiency microwave absorbers.

Highly Active of Nanostick-Assembled Hollow Core-Shell Structure Tio2@Mnox for Photothermocatalysis Ethyl Acetate and No with Free-Ammonia at Low Temperature

Highly Active of Nanostick-Assembled Hollow Core-Shell Structure Tio2@Mnox for Photothermocatalysis Ethyl Acetate and No with Free-Ammonia at Low Temperature

Highly Active of Nanostick-Assembled Hollow Core-Shell Structure Tio2@Mnox for Photothermocatalysis Ethyl Acetate and No with Free-Ammonia at Low Temperature: Resistence, Key Reaction Step and Mechanism

Highly Active of Nanostick-Assembled Hollow Core-Shell Structure Tio2@Mnox for Photothermocatalysis Ethyl Acetate and No with Free-Ammonia at Low Temperature: Resistence, Key Reaction Step and Mechanism

Synthesis of CuCo2S4 nanoparticles assembled in micro-sized hollow spheres composed with polyaniline: An effective electrode material for supercapacitors

CuCo2S4 is a well-studied promising electrode material for energy storage devices. In this work we describe a method to further increase its electrochemical performance by forming hollow core–shell structures of CuCo2S4 and polyaniline. CuCo2S4 nanoparticles are synthesized in micro-sized hollow sphere assemblies through facile solvothermal method. They exhibit high capacitive behavior with specific capacitance of about 839F g−1 at current density of 1 A g−1 in three-electrode configuration. Oxidative polymerization of aniline on surface of these micro-sized hollow spheres leads to form an electrochemically improved nanocomposite and the specific capacitance is increased to about 1120F g−1 at current density of 1 A g−1. This superior capacitive performance can be attributed to the hollow core–shell structure of the obtained nanocomposite. The assembled symmetric supercapacitor device based on as-prepared CuCo2S4/PAni nanocomposite exhibits a wide working potential of 2 V in 1 M Na2SO4 which can reach a high energy density and power density of 44.16 Wh kg−1 and 1 kW kg−1, respectively.

Synthesis and photocatalytic activity of Cu2O hollow nanospheres/TiO2 nanosheets by an in-situ water-bath method

In this work, a simple in-situ water-bath method is used to load Cu2O hollow nanospheres (named as H-Cu2O) on TiO2 nanosheets (named as TiO2-NS). H-Cu2O of 160–250 nm in diameter is uniformly supported on the surface of TiO2-NS. H-Cu2O has a novel hollow core-shell structure with a double shell. Specifically, the diameters of inner hollow spheres are 80–90 nm and the thickness of the outer shell and inner shell are about 40 nm and 25 nm, respectively. It is conjectured that the outer and inner shells of H-Cu2O can both provide adsorption and reaction sites, favoring the photocatalytic reaction. The UV–visible diffused reflectance spectra show that compared with TiO2-NS, the H-Cu2O/TiO2-2 sample with adding 80 mg of TiO2-NS shows a stronger visible light absorption. Furthermore, the steady-state photoluminescence (PL) and photocurrent spectra show that H-Cu2O/TiO2-2 has a weaker PL intensity at about 370 nm and 6 times higher photocurrent intensity than TiO2-NS, demonstrating that H-Cu2O/TiO2-2 has higher charge separation efficiency. Compared with TiO2-NS, the photocatalytic activity of H-Cu2O/TiO2-2 under UV light (λ ≤ 400 nm) increase by 6.3 times for the degradation of methyl orange. The improved photocatalytic activity can be attributed to the enlarged BET areas (6.1 m2 g-1/H-Cu2O/TiO2-2 vs. 3.8 m2 g-1/TiO2-NS), the enhanced light adsorption, and the improved charge separation efficiency. The reported in-situ water-bath method is simple, mild, and general, which could be extended to other novel composite materials.

Cascade Release Nanocarriers for the Triple-Negative Breast Cancer Near-Infrared Imaging and Photothermal-Chemo Synergistic Therapy.

Triple-negative breast cancer (TNBC) has inadequate treatment approaches and a poor prognosis. It is urgent to develop new treatment approaches for TNBC. The combination of photothermal therapy (PTT) and chemotherapy is a very effective potential therapy for TNBC. However, asynchronous accumulation, unclear efficacy, and toxic side effects hinder the further promotion of this method. Therefore, we designed and constructed a new type of nanocarriers, the cascade release near-infrared imaging (NIFI) & thermal-chemo combination nanoparticles (CNC NPs), that can release drugs through the cascade of ultrasound triggering and pH responding to achieve the synchronous tumor accumulation, monitoring and synergistic treatment of two functional molecules. The key material of CNC NPs is the polydopamine (PDA), which, through self-assembling, forms a rigid shell that contains doxorubicin (DOX) and NIF fluorescent dye IR780 on the surface of the perfluorohexane (PFH) microbubbles. The results show that CNC NPs have a hollow core-shell structure with an average particle size of 97.3 ± 27.2 nm and have exceptional colloidal stability and photothermal conversion efficiency. The NPs can effectively perform cascade drug release through ultrasound triggering and pH responding. CNC NPs have good in vivo biological safety and excellent fluorescence imaging, drug delivery, and therapeutic abilities in the TNBC models. These results provide an experimental basis for the development of new clinical treatment methods for TNBC.

Oxygen‐Vacancies‐Induced Enhancement in Photocatalystic Performance of Sea Urchin‐Like Fe3O4@ZnO Hollow Core–Shell Structures

A novel sea urchin‐like Fe3O4@ZnO (S‐FZ) hollow core–shell photocatalyst is developed, which achieves about fourfold higher photocatalystic degradation efficiency (84.4%) than the waxberry‐type Fe3O4@ZnO (W‐FZ) photocatalyst due to its larger specific surface area. After postannealing at different temperatures under argon atmosphere, the photocatalystic degradation efficiency of S‐FZ is effectively improved. When the annealing temperature is 500 °C, the degradation efficiency of S‐FZ hollow core–shell structures is further improved to 99%, which is related to the synergistic effect of high density of oxygen vacancies. Such S‐FZ catalysts are easily separated with a magnet and reused with only 2% loss in photocatalystic degradation efficiency after five circles. Herein, a practical approach toward high‐efficient and recyclable photocatalysts is provided.

Synthesis of hollow spherical MoS2@Fe3O4-GNs ternary composites with enhanced microwave absorption performance

To solve the problem of poor electromagnetic wave (EMW) absorbing performance caused by scarcely magnetic loss of pure graphene, the combination of graphene and magnetic materials becomes the main measures to enhance EMW absorbing properties. In this study, a primitive two-step hydrothermal and solvothermal method was employed to fabricate the hollow spherical MoS2@Fe3O4-GNs ternary composites, which avoids the complex process of template removal. When the thickness is 2.6 mm, the composite has the optimal reflection loss (RLmin) at 10.08 GHz, and the optimal reflection loss value is up to − 48.1 dB, and the effective absorbing bandwidth (EAB) can reach 4.08 GHz at 1.7 mm thickness. The composite materials not only have gratifying impedance matching performance, but also realize the effective coordination of magnetic loss and dielectric loss, showing the overall excellent absorbing performance benefits from the successful combination of the hollow core–shell structure of MoS2@Fe3O4 and GNs. Therefore, it has a broad prospect as an attractive alternative of lightweight absorbing materials with wideband.

The Pt-free 1T/2H-MoS2/CdS/MnOx hollow core-shell nanocomposites toward overall water splitting via HER/OER synergy of 1T-MoS2/MnOx

Hydrogen evolution reaction/Oxygen evolution reaction (HER/OER) synergy would be the most important issue for overall water splitting. The Pt-free 1T/2H-MoS2/CdS/MnOx hollow core–shell nanocomposites are fabricated via a continuous hydrothermal–chemical method; therefore, the OER co-catalysts MnOx and CdS shell are deposited on the surface of SiO2 nanosphere templates continuously via hydrothermal–chemical method. Subsequently, the SiO2 templates are etched via chemical method and the 2H-MoS2/CdS hollow core–shell heterojunction and 1T-MoS2 HER co-catalyst are introduced via one-step hydrothermal method. Evaluated by photocatalytic performance, the 1T/2H-MoS2/CdS/MnOx exhibits an enhanced HER performance of about ~50 folds than that of single CdS hollow nanosphere, and achieves a decent overall water splitting performance of about ~1668.00(H2)/824.61(O2) μmol/g∙h, which can be mainly ascribed to the well HER/OER synergy and formation of hollow core–shell structure. Therefore, the 1T-MoS2 with quick electron transport and decent solid/liquid interface can promote the photogenerated electron diffusing, the MnOx with mixed Mn3+/Mn4+ ions can activate the hole-related species for OH− oxidation and promote H2O2 decomposition, the 2H–MoS2/CdS heterojunction can separate the charge carrier and meet the potential to achieve overall water splitting. Additionally, the 1T/2H-MoS2 with decent lattice matching can improve the charge carrier transport, the 1T-MoS2 with sufficient specific surface areas can increase active sites and the hollow core–shell structure can increase solar efficiency which is also beneficial for enhancing the overall water splitting performance and stability.

Synthesis of a hollow-structured flower-like Fe3O4@MoS2 composite and its microwave-absorption properties.

In order to realize the characteristics of new types of wave-absorbing materials, such as strong absorption, broad bandwidth, low weight and small thickness, a hollow-structured flower-like Fe3O4@MoS2 composite was successfully prepared by simple solvothermal and hydrothermal methods in this paper. The structural properties were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Besides, the microwave properties and magnetic properties were measured using a vector network analyzer and via a hysteresis loop. SEM and TEM images revealed that MoS2 nanosheets grew on the surface of hollow nanospheres. The results showed that the composite exhibited excellent absorbing property. When the molar ratio of Fe3O4 and MoS2 was 1 : 18, the minimum reflection loss value reached −49.6 dB at 13.2 GHz with a thickness of 2.0 mm and the effective absorption bandwidth was 4.24 GHz (11.68–15.92 GHz). Meanwhile, the effective absorption in the entire X-band (8–12 GHz) and part of the C-band (4–8 GHz) and Ku-band (12–18 GHz) could be achieved by designing the sample thickness. In addition, the hollow structure effectively reduced the density of the material, which was in line with the current development trend of absorption materials. It could be predicted that the hollow core–shell structure composite has a potential application prospect in the field of microwave absorption.

Self-template and in-situ polymerization strategy to lightweight hollow MnO2@polyaniline core-shell heterojunction with excellent microwave absorption properties

Nowadays, high-frequency electromagnetic pollution makes the lightweight and high-efficiency absorption materials become the research hotspot. In this paper, the hollow structure MnO2@PANI microsphere composite was reasonably synthesized by self-template strategy and in-situ polymerization. Coating conductive polyaniline (PANI) on the modified surfaces of MnO2 microsphere not only can improve the impedance matching and microwave absorption ability, but also solve the drawback of low loss intensity as well as narrow absorption band of pure MnO2. The conductive polymer PANI conductance loss, MnO2-PANI multiple interfacial polarization and multiple reflection loss synergy endows hollow MnO2@PANI microsphere excellent microwave absorption performance. The RLmin of hollow MnO2@PANI microsphere is −52.06 dB at 8.48 GHz and has a wide absorption of 4.56 GHz. Those positive results show that the pure dielectric MnO2@PANI microsphere material with a multi-interface hollow core-shell structure prepared from a template is a lightweight and efficient absorbent.

One-step green fabrication of hierarchically porous hollow carbon nanospheres (HCNSs) from raw biomass: Formation mechanisms and supercapacitor applications

Hierarchical porous hollow carbon nanospheres (HCNSs) were fabricated directly from raw biomass via a one-step method, in which HCNSs were obtained by thermal treatment of raw biomass in the presence of polytetrafluoroethylene (PTFE). The HCNSs possess coupling merits of uniformly distributed hollow spherical architectures, and high specific surface area, abundant accessible/open micropores and reasonable mesopores, the HCNS-based electrodes deliver high electrochemical capacitance. The formation mechanisms of pores and hollow core-shell structures were explored thoroughly, it is found that the key to the formation of hollow core-shell structure is the onset-pyrolysis temperature difference between raw biomass and PTFE. Moreover, the content of silica had significant effects on the textures of HCNSs, and HCNS with the largest SSA of 1984 m2/g was obtained. Accordingly, a possible mechanism of HCNSs formation was proposed here, where PTFE acted as the pore creation and nucleation agents and raw biomasses were the primary carbon precursors.