Core-shell Hollow Structure Research Articles

Room-temperature NH3-sensor: SnO2@PANI core-shell hollow spheres

A novel room-temperature NH3-sensing material (SnO2@PANI core-shell hollow nanospheres) was synthesized by coating various amounts of PANI on SnO2 hollow nanospheres using a simple in-situ chemical oxidation polymerization method. The morphology and nanostructures of the synthesized sensing materials were characterized using SEM, TEM, FTIR, and XRD. Gas-sensing tests demonstrate that SP-5 exhibits the highest response to NH3 at room temperature, with a response value (26.48 at 500 ppm) more than 6 times higher than that of pure PANI (4.35). This sensor displays excellent selectivity, with good anti-interference capability to CO and NO2. The improved sensing performance of the core-shell hollow structure is attributed to the unique structure and p-n heterojunction between PANI and SnO2, which is confirmed by EIS spectra.

Advanced core-shell hollow carbon nanofibers for ion and electron accessibility in sodium ion batteries.

One-dimensional core-shell hollow carbon nanofibers (HCNFs) have been synthesized by coaxial electrospinning, deacetylation and carbonization, which exhibit multi-surface properties that enhance electrolyte infiltration and facilitate ion/electron transport. The nitrogen-doped hard carbon outer shell compensates for the low conductivity of amorphous carbon, and the inner core carbon supports the stability of core-shell hollow structures. This unique structure ensures the accessibility of electrons/ions during electrochemical reactions and contributes to the superior rate performance of HCNFs. Ultimately, a high retention rate of 77% of the initial capacity value (0.1 A g-1) was demonstrated at a current density of 2 A g-1. The core-shell hollow structure designed in this work greatly optimizes the sodium transport dynamics.

SnO2 @ZnS core-shell hollow spheres with enhanced room-temperature gas-sensing performance

To detect flammable gases and lower energy consumption, room-temperature gas sensors with high sensitivity, selectivity and stability have attracted increasing attention. In this work, SnO2 @ZnS core-shell hollow spheres are prepared via a two-step hydrothermal method. The effects of morphology and composition on gas sensing performance were systematically investigated by adjusting the molar ratio of SnO2 to ZnS. Compared with pure SnO2 hollow spheres, the core-shell composites exhibit excellent enhanced sensing properties to n-butanol at room temperature. The SnO2 @ZnS (1:0.5) core-shell hollow spheres show the highest sensing response (12.6) to 100 ppm n-butanol at 25ºC, which was ∼4 times higher than that of the pristine SnO2 hollow spheres. The room-temperature sensing mechanism to n-butanol is proposed. The enhanced sensing mechanism of the core-shell structure is attributed to i) the uniform hollow structure, ii) the electron transfer to surface induced by SnO2 metallization and the formation of n-n heterojunction, and iii) high charge carrier density and fast charge transfer rate. This study provides a novel core-shell hollow structure for room-temperature detection of n-butanol.

Construction of KCu7S4@NiMoO4 three-dimensional core-shell hollow structure with high hole mobility and fast ion transport for high-performance hybrid supercapacitors

The rational construction of hierarchical three-dimensional nanostructures with multiple metallic elements is of great importance for improving electrochemical energy storage. KCu7S4 is a first-rate candidate for electrode materials of supercapacitors, due to its unique quasi one-dimensional K+ alkali metal ion channels and extremely low resistance property. However, the limited ion contacted sites and single metal element composition restrain the extra upgrade of its electrochemical performance. We thereof have effectively prepared KCu7S4@NiMoO4 nanocomposites with a three-dimensional core-shell hollow structure by anchoring NiMoO4 nanosheet arrays uniformly on KCu7S4 nanorods. The incorporation of NiMoO4 nanosheet arrays increases the active sites and electrochemical stability. Due to the synergistic effect of NiMoO4 nanosheet arrays with Cu atomic vacancies and quasi one-dimensional K+ alkali metal ion channels in KCu7S4 nanorods, the prepared electrode has outstanding capacitance (1194.6 F g−1 (165.91 mAh g−1), 1 A g−1), significant equivalent series resistance (0.614 Ω), and high capacitance retention (92.3% after 10,000 cycles). In addition, the KCu7S4@NiMoO4//AC ASC prepared with KCu7S4@NiMoO4 cathode and activated carbon (AC) anode exhibits excellent energy density (55.9 Wh kg−1, 750 W kg−1) and outstanding capacitance retention (91.3% after 10,000cycles). Therefore, the new three-dimensional core-shell hollow structure electrode materials with KCu7S4 nanorods as the cores and binary metal molybdates as the shell materials have a broad research potential.

Hollow core-shell Z-scheme heterojunction on self-floating carbon fiber cloth with robust photocatalytic-photothermal performance

The combination of photothermal catalysis and photocatalysis is an effective method to remove Cr(VI) and degrade organic pollutants using solar energy. Herein, hollow flower-like W 18 O 49 @ZnIn 2 S 4 core-shell Z-type heterojunctions were prepared on carbon fiber cloth (CC) by two methods, hydrothermal method and solvent heat, which are easy to operate. The prepared photocatalysts showed very excellent photocatalytic degradation for the redox removal of Cr(VI) and degeneration of bisphenol A (BPA) under simulated sunlight, and the W 18 O 49 @Znln 2 S 4 /CC composites showed 95% and 100% removal of bisphenol A (BPA) and Cr(VI), respectively. The formation of Z-type heterojunctions promoted rapid carrier transfer, and the hollow structure improved light utilization, while the core-shell structure increased the interfacial area and number of active sites. In addition, the oxygen vacancies in W 18 O 49 have ligated unsaturated sites and unpaired electrons, which can lower the reaction energy barrier and promote molecular activation. The effects of different catalyst types, different pH values, and different initial concentrations of BPA on the photocatalytic performance were demonstrated. Furthermore, the W 18 O 49 @Znln 2 S 4 /CC composite exhibited excellent stability and reusability in 10 consecutive cycles of experiments. Its easy recovery and high stability imply potential practical applications, providing an effective strategy for the development of a new efficient catalyst for the treatment of wastewater and a sustainable environment. Hollow Core-Shell Z-Scheme Heterojunction on Self-Floating Carbon Fiber Cloth is synthesized by solvothermal and hydrothermal methods. It shows excellent visible light-driven photocatalytic pollutant removal efficiency due to the formation of Z-scheme heterojunctions promoting rapid charge carrier transfer, and the core-shell hollow structure improving light utilization and surface-active sites. • W 18 O 49 @ZnIn 2 S 4 /CC is synthesized as a self-floating photocatalyst. • The Z-scheme heterojunction has the advantage of promoting carrier transfer. • The hollow structure has a light reflection path and light collection capability. • It shows robust photothermal-photocatalytic performance. • W 18 O 49 @ZnIn 2 S 4 /CC can be easily recycled and reused.

Construction of Kcu7s4@Nimoo4 Three-Dimensional Core-Shell Hollow Structure with High Hole Mobility and Fast Ion Transport for High-Performance Hybrid Supercapacitors

Construction of Kcu7s4@Nimoo4 Three-Dimensional Core-Shell Hollow Structure with High Hole Mobility and Fast Ion Transport for High-Performance Hybrid Supercapacitors

Electrospun Core-Shell Hollow Structure Cocatalysts for Enhanced Photocatalytic Activity

The core-shell NaYF4/Yb/Tm/TiO2 hollow composite fibers were prepared by coaxial electrospinning and high-temperature calcination. The composite fibers exhibit excellent photocatalytic activity under the dual synergistic of regulating the core-shell hollow microstructure and the composition by doping nanoparticles. Compared with commercial P25 and hollow fiber without nanoparticles, the degradation efficiency of rhodamine B using the core-shell composite fiber was significantly improved up to 99%. Moreover, the nanoparticles in the composite fibers can exist stably and maintain good structure and photocatalytic activity after repeated use. Therefore, the composite fiber has a wide application prospect in photocatalytic degradation of organic pollutants.

Electrochemical performance enhancement by the partial reduction of NiFe2O4@g-C3N4 with core-shell hollow structure

Transition metal oxide NiFe2O4 has many advantages such as abundance in nature, easy availability, low toxicity and being environmentally friendly. However, it suffers from poor electrical conductivity which results in unsatisfactory electrochemical performance. In this work, the construction of NiFe2O4@g-C3N4 core-shell hollow spherical structure and the in-situ formation of Fe–Ni alloy have been achieved by facile hydrothermal method followed by annealing in 5%H2/95%Ar. The electrical conductivity of electrode has been greatly improved leading to a specific capacity of 85.3 mAh g−1 at 1 A g−1 and a 67.2% capacity retention at 20 A g−1. A hybrid device exhibits 19.5 Wh kg−1 in specific energy and 150.1 W kg−1 in specific power, and good cycling stability of 100% capacity retention after 10,000 cycles at 6 A g−1.

Direct Fabrication of Reduced Graphene Oxide@SnO2 Hollow Nanofibers by Single-Capillary Electrospinning as Fast NO2 Gas Sensor

Single-capillary electrospinning has been exhibited to be a simple and scalable method for fabricating nanofibers. Construction of graphene/inorganic fibers with the core-shell hollow structure using graphene as skeleton has been rarely reported. Here, we show a facile approach to prepare electrospun reduced graphene oxide@SnO2 composite nanofibers with the hollow structure. The hollow core@shell structure is formed in a single-capillary electrospinning process including sintering, which is promising for the preparation of graphene/inorganic composite nanofibers. The reduction of as-synthesized graphene is realized by stannous ion. Resulting hollow and core-shell structure enables the reduced graphene oxide@SnO2 composite nanofibers to adsorb and desorb the target gas more easily, which is promising for future applications as fast NO2 gas sensor.

Construction of a Hierarchical Architecture of Covalent Organic Frameworks via a Postsynthetic Approach.

Covalent organic frameworks (COFs) represent an emerging class of crystalline porous materials that are constructed by the assembly of organic building blocks linked via covalent bonds. Several strategies have been developed for the construction of new COF structures; however, a facile approach to fabricate hierarchical COF architectures with controlled domain structures remains a significant challenge, and has not yet been achieved. In this study, a dynamic covalent chemistry (DCC)-based postsynthetic approach was employed at the solid-liquid interface to construct such structures. Two-dimensional imine-bonded COFs having different aromatic groups were prepared, and a homogeneously mixed-linker structure and a heterogeneously core-shell hollow structure were fabricated by controlling the reactivity of the postsynthetic reactions. Solid-state nuclear magnetic resonance (NMR) spectroscopy and transmission electron microscopy (TEM) confirmed the structures. COFs prepared by a postsynthetic approach exhibit several functional advantages compared with their parent phases. Their Brunauer-Emmett-Teller (BET) surface areas are 2-fold greater than those of their parent phases because of the higher crystallinity. In addition, the hydrophilicity of the material and the stepwise adsorption isotherms of H2O vapor in the hierarchical frameworks were precisely controlled, which was feasible because of the distribution of various domains of the two COFs by controlling the postsynthetic reaction. The approach opens new routes for constructing COF architectures with functionalities that are not possible in a single phase.

Hollow MnOx-CeO2 mixed oxides as highly efficient catalysts in NO oxidation

A series of hollow MnOx-CeO2 mixed oxide catalysts were prepared by employing carbon as hard templates. The activity tests reveal that the catalytic performance of MnOx-CeO2(CS) samples are more active than that of MnOx-CeO2(AC) sample, indicating carbon sphere (CS) as a more effective carbon template. Among these samples, MnOx-CeO2(CS1) sample exhibits the best activity, for which a maximal NO conversion (∼82%) could be attained at 220°C when GHSV=120,000h−1. In addition, the NO conversion could be further improved with lower NO initial concentration or higher O2 content. Under the simulated flue gas condition, the activity of MnOx-CeO2(CS1) sample is barely affected by the presence of CO2, but the influence of H2O and SO2 couldn’t be neglected. The characterization result proves that the core-shell hollow structure has been successfully synthesized over MnOx-CeO2 binary oxides. For the hollow MnOx-CeO2 sample, the mesopore structures are formed and the MnOx oxides are highly dispersed on CeO2 support. Among these samples, MnOx-CeO2(CS1) sample possesses the largest SBET and Vtotal values. The result of H2-TPR and oxygen pulse measurement indicates that MnOx-CeO2(CS) samples, especially MnOx-CeO2(CS1) exhibits the best redox property. Moreover, more amount of high valence Mn as redox active sites and more oxygen vacancies exist in MnOx-CeO2(CS1) proved by XPS technique. Overall, these properties may contribute to the excellent activity.

Controlled Drug Delivery System Based on Magnetic Hollow Spheres/Polyelectrolyte Multilayer Core–Shell Structure

A novel controlled drug delivery system was fabricated by coating chitosan/PAA multilayer onto magnetic hollow spheres via a "Layer-by-Layer" (LBL) assembly approach. Cefradine was used as a model drug to evaluate the drug release characteristics of this core-shell hollow structure and the results show that it exhibits a sustained release of the drug and the release rate can be regulated by the pH environment of release medium. It is believed that this core-shell hollow structure, which combines the advantage of controlled delivery as well as magnetic targeting, has commendable potential in drug delivery therapeutics.