Hollow Interior Space Research Articles

Assembly of Metal-Phenolic Networks onto Microbubbles for One-Step Generation of Functional Microcapsules.

The one-step assembly of metal-phenolic networks (MPNs) onto particle templates can enable the facile, rapid, and robust construction of hollow microcapsules. However, the required template removal step may affect the refilling of functional species in the hollow interior space or the in situ encapsulation of guest molecules during the formation of the shells. Herein, a simple strategy for the one-step generation of functional MPNs microcapsules is proposed. This method uses bovine serum albumin microbubbles (BSA MBs) as soft templates and carriers, enabling the efficient pre-encapsulation of guest species by leveraging the coordination assembly of tannic acid (TA) and FeIII ions. The addition of TA and FeIII induces a change in the protein conformation of BSA MBs and produces semipermeable capsule shells, which allow gas to escape from the MBs without template removal. The MBs-templated strategy can produce highly biocompatible capsules with controllable structure and size, and it is applicable to produce other MPNs systems like BSA-TA-CuII and BSA-TA-NiII . Finally, those MBs-templated MPNs capsules can be further functionalized or modified for the loading of magnetic nanoparticles and the pre-encapsulation of model molecules through covalence or physical adsorption, exhibiting great promise in biomedical applications.

Self-sacrifice-template epitaxial growth of hierarchical MnO2@NiCo2O4 heterojunction electrode for high-performance asymmetric supercapacitor

Constructing three-dimensional (3D) hierarchical bimetallic pseudocapacitive materials with abundant opening channel and heterojunction structures is rather promising but still challenging for high-performance supercapacitors. Herein, a self-sacrifice-template epitaxial growth strategy was proposed for the first time to construct 3D hierarchical bimetallic pseudocapacitive material. By using this strategy, NiCo2O4 nanowires (NiCo2O4NW) arrayed randomly to form a porous shell via in-situ epitaxial growth fully enclosing a MnO2 tube core, forming multiple transport channels and nano-heterojunctions between MnO2 and NiCo2O4NW, which facilitates electron transfer, i.e. exhibiting high electronic conductivity than any single component. As a result of the self-sacrifice-template epitaxial growth method, special hollow tectorum-like 3D hierarchical structure with considerable inter-nanowire space and hollow interior space enables easy access of electrolyte to NiCo2O4NW surface and MnO2 core, thereby resulting in highly exposed redox active sites of MnO2 core and NiCo2O4NW shell for energy storage. Comprehensive evaluations confirmed MnO2@NiCo2O4NW was a supercapacitor electrode candidate, delivering a superior energy density of 106.37 Wh kg−1. Such performance can be ascribed to the synergistic coupling effect of 3D hierarchical tube and nano-heterojunction structures. The proposed self-sacrifice-template epitaxial growth strategy provides important guidance for designing high-performance energy storage materials.

CoCl2 encapsulated in nitrogen-doped carbon hollow cubic nanobox enabling long-life and high-rate lithium storage

The poor cycling stability and inferior rate performance impede the application of CoCl2 in lithium-ion batteries. Herein, Prussian blue analogs (Co3[Co(CN)6]2, Co-Co PBA) microcubes are coated by a layer of polydopamine (PDA). Through carbonization and chlorination, Co-Co PBA@PDA is decomposed into CoCl2 2H2O and CoCl2 6H2O encapsulated in nitrogen-doped carbon hollow cubic nanoboxes. The closed independent carbon nanobox, strong coupling effect between carbon nanobox and CoCl2, high electron-conductive and Li+-diffusive wall of the carbon nanoboxes, and large hollow interior space bring about superior lithium storage performance through their synergy. As an anode material for lithium-ion batteries, the composite can deliver considerable discharge capacity of 406 mAh g−1 at 2 A g−1 after 1500 cycles, presenting excellent cycling performance. The average discharge capacities at 0.1 and 10 A g−1 can reach 1282 and 123 mAh g−1, respectively, which exhibits high electrochemical activity and outstanding rate capability. Electrochemical kinetics analyses in combination with ex-situ material characterization demonstrate that a certain proportion of surface capacitive behavior occurs in electrochemical reaction. The diffusion of Li ions is rapid and stable. The reaction impedance is low. The composite is of good structural integrity during cycling. This work provides a significant exploration for development of high-performance transition metal chlorides in lithium-ion batteries.

Strong coke-resistivity of spherical hollow Ni/SiO2 catalysts with shell-confined high-content Ni nanoparticles for methane dry reforming with CO2

Hollow nanocatalysts, which are vehemently researched for their delimited cavity and enclosed shell, could manifest tunable focal properties besides well-defined active sites, thus enhancing the catalytic functionality. Herein, nickel-silicate hollow spheres (NHSs) with varied shell thickness and interior cavity size were commensurately designed. Distinction between various NHSs-derived Ni/SiO2 with identically mimicked morphologies was realized by examining their catalytic performance for methane dry reforming (DRM) reaction with sweeping pre- and post-reaction characterizations (TEM, XPS, XANES, in-situ DRIFTS). Besides facilitating the DRM reaction up to its thermodynamic limit, it was revealed that optimal NHS conformation is beneficial as a potential natural barrier against sintering and coking bottlenecks. Furthermore, a fine-tuned shell composition could endow improved Ni-sintering resistivity and enhanced reactivity to the NHS nanocatalysts. Our findings prove that the hollow interior space with a conducive shell thickness positively influences the reactant conversion and coking hindrance during the DRM reaction.

Simultaneously high mass-loading and volumetric energy density in Ag2O-intercalated MnO2-based supercapacitor with rapid electron/ion transport channels

High volumetric energy density (VED) is essential for supercapacitors’ practicality, but is extremely challengeable when high mass-loading is simultaneously demanded, because the high mass-loaded electrode always encounters the limited ions-diffusion accessibility and sluggish electron transferability. Herein, for the first time, Ag2O-intercalated hollow MnO2 (Ag2O-HMnO2) electrode with rapid ion/electron transport channels is rationally designed and fabricated by a facile in-suit growth & self-sacrificing template method. Ultrahigh mass-loading benefits from the randomly arrayed MnO2-nanosheets fully covered on silver-nanowire@polypyrrole (AgNW@PPy-template). Vast interior space in MnO2, which forms after the oxidative decomposition of AgNW@PPy-template, offers large electrode–electrolyte interfaces and huge open space channel for unimpeded ions transport. Such Ag2O-intercalated hierarchical hollow structure not only provides spacious “ion transport channel” (hollow interior space) and “reservoir” (much space between neighboring MnO2-nanosheets) for ions diffusion/storage, but also boosts electron transferability via the conductive Ag2O-particulate-based percolation networks. As a consequence, Ag2O-HMnO2 exhibits excellent electrochemistry performance and unprecedented MnO2 utilization efficiency. Ag2O-HMnO2-based supercapacitor exhibits a remarkably enhanced VED of 7.33 mWh cm−3, approximately sixfold improvement compared to that of pristine MnO2. The novel structure engineering strategy presented herein facilitates the excellent ion/electron transferability, which may open a new avenue for transition-metal-oxide/hydroxides-based supercapacitors to achieve high mass-loading and VED.

Synthesis of hollow TiO2 nanobox with enhanced electrorheological activity

TiO2 nanoboxes with a hollow interior space, derived from titanium oxydifluoride (TiOF2) nanocubes, were prepared using a two-step method, in which the TiOF2 nanocubes acting as the precursor were first synthesized using a typical hydrothermal route. Subsequently, a second hydrothermal step was developed to prepare the TiO2 nanoboxes. The clear phase transformation from the TiOF2 precursor to anatase TiO2 was confirmed using X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photo-electron spectroscopy analyses. The evolution of the morphology from a nanocube to nanobox was revealed by scanning electron microscopy and transmission electron microscopy observations. The influences of the phase and morphology on the electrorheological (ER) effect were investigated using an ER test. The ER results suggested that the ER efficiency was significantly enhanced after the second hydrothermal treatment, especially under a high external electric field strength. The enhancement in the ER efficiency was further studied using a dielectric spectrum analysis. It demonstrated that the faster response time and large permittivity difference obtained from the dielectric spectrum of TiO2 were responsible for the improvement in the ER effect.

Synthetic Multienzyme Complexes, Catalytic Nanomachineries for Cascade Biosynthesis In Vivo.

Multienzyme complexes, or metabolons, are assemblies or clusters of sequential enzymes that naturally exist in metabolic pathways. These nanomachineries catalyze the conversion of metabolites more effectively than the freely floating enzymes by minimizing the diffusion of intermediates in vivo. Bioengineers have devised synthetic versions of multienzyme complexes in cells to synergize heterologous biosynthesis, to improve intracellular metabolic flux, and to achieve higher titer of valuable chemical products. Here, we utilized orthogonal protein reactions (SpyCatcher/SpyTag and SnoopCatcher/SnoopTag pairs) to covalently assemble three key enzymes in the mevalonate biosynthesis pathway and showed 5-fold increase of lycopene and 2-fold increase of astaxanthin production in Escherichia coli. The multienzyme complexes are ellipsoidal nanostructures with hollow interior space and uniform thickness and shapes. Intracellular covalent enzyme assembly has yielded catalytic nanomachineries that drastically enlarged the flux of carotenoid biosynthesis in vivo. These studies also deepened our understanding on the complexity of hierarchical enzyme assembly in vivo.

Bowl-like double carbon layer architecture of hollow carbon@FePO4@reduced graphene oxide composite as high-performance cathodes for sodium and lithium ion batteries

The amorphous FePO4 are potential cathode materials for Li and Na ion batteries, due to its low costs, environmental benignity, satisfactory thermal stability and suitable voltage. Especially, its amorphous structure without apparent structure confinement is conducive to the isotropic ion transport. However, it suffers from the extremely low electronic conductivity, resulting in sluggish kinetics during cycling process. Herein, a novel bowl-like double carbon layer architecture is introduced to design and construct hollow carbon@FePO4@reduced graphene oxide composite, in which bowl-like hollow carbon covered with amorphous FePO4 nanoparticles acts as an internal skeleton as well as the reduced graphene oxide tight wrapped serves as an external framework. The bowl-like double carbon layer architecture greatly improves the electron transportation and decreases the excessive hollow interior space while reserving the general advantages of hollow structures. As a result, the as-synthesized composite as cathode materials exhibits excellent sodium and lithium storage properties in the aspect of high capacity, excellent rate capability, especially pre-eminent cycling stability. Kinetic analysis indicates that the charge storage in composite presents pseudocapacitive contribution, which is responsible for the improved electrochemical properties.

Theragnostic potentials of core/shell mesoporous silica nanostructures.

Theragnostics is considered as an emerging treatment strategy that integrates therapeutics and diagnostics thus allowing delivery of therapeutics and simultaneous monitoring of the progression of treatment. Among the different types of inorganic nanomaterials that are being used for nanomedicine, core shell mesoporous silica nanoparticles have emerged as promising multifunctional nanoplatform for theragnostic application. Research in the design of core/shell mesoporous silica nanoparticles is steadily diversifying owing to the various interesting properties of these nanomaterials that are advantageous for advanced biomedical applications. Core/shell mesoporous silica nanoparticles, have garnered substantial attention in recent years because of their exceptional properties including large surface area, low density, ease of functionalization, high loading capacity of drugs, control of the morphology, particle size, tunable hollow interior space and mesoporous shell and possibility of incorporating multifunctional interior core material. In the past decade researcher's demonstrated tremendous development in design of functionalized core/shell mesoporous silica nanoparticles with different inorganic functional nanomaterial incorporated into mesoporous nanosystem for simultaneous therapeutic and diagnostic (theragnostic) applications in cancer. In this review, we recapitulate the progress in commonly used synthetic strategies and theragnostic applications of core/shell mesoporous silica nanoparticles with special emphasis on therapeutic and diagnostic modalities. Finally, we discuss the challenges and some perspectives on the future research and development of theragnostic core/shell mesoporous silica nanoparticles.

Pistachio-Shuck-Like MoSe2 /C Core/Shell Nanostructures for High-Performance Potassium-Ion Storage.

Potassium-ion batteries (KIBs) have recently attracted intensive attention because of the abundant potassium resources and their low cost and high safety. However, the major challenge faced by KIBs lies in the lack of stable and high-capacity materials for the intercalation/deintercalation of large-size potassium ions. A unique pistachio-shuck-like MoSe2 /C core/shell nanostructure (PMC) is synthesized herein as an advanced anode for boosting the performance of KIBs. This PMC is featured with a few layers of molybdenum selenide as the core with an expanded interlayer spacing of ≈0.85 nm, facilitating the intercalation/deintercalation of K ions, and a thin amorphous carbon as the shell, which can confine the active molybdenum selenide nanosheets during cycling for maintaining the high structural stability. Most importantly, as a whole, the PMC has the advantages of reducing the surplus hollow interior space for improving its packing density and buffering the volume expansion during the K-ion intercalation for further enhancing the stability. As a consequence, the PMC shows a very high capacity of 322 mAh g-1 at 0.2 A g-1 over 100 cycles, and can still remain 226 mAh g-1 at 1.0 A g-1 for a long period of 1000 cycles, which is among the best-reported KIBs anodes.

Rational Integration of Inbuilt Aperture with Mesoporous Framework in Unusual Asymmetrical Yolk-Shell Structures for Energy Storage and Conversion.

Despite the attractive benefits of hollow structures as electrodes for advanced energy storage-conversion capabilities, one prevailing shortcoming is their compromised structural integrity and volumetric energy density due to the introduction of an ultrathin shell with an excessively underutilized large hollow cavity. Herein, we report a facile and template-free synthetic route to realize unusual asymmetrical yolk-shell (AYs) structures composed of mixed-valence NiCo2O4 material. Explicitly, this work highlights the unusual off-central core, an AYs structure that encompasses a hemispherical hollow interior, and a mesoporous solid counterpart. As such, it retains desirable hollow structural characteristics while favorably precludes the excessive unexploited hollow interior space for increased active material packing. Unlike the conventional symmetrical yolk-shell (SYs) which is composed of a porous shell framework radially throughout the structure, the mesoporous solid constitution of the AYs structure offers an inbuilt reinforced framework to support the partial porous shell and concurrently leaves sufficient void for volumetric buffering. Another unique structural feature of the AYs structure is the formation of a submicron aperture or opening on the shell that enhances accessibility of electrolyte diffusion. All of these synergistic structural features of NiCo2O4 AYs structures enhance the pseudocapacitive and electrocatalytic properties.

SnO2@N‐Doped Carbon Hollow Nanoclusters for Advanced Lithium‐Ion Battery Anodes

AbstractA facile method to synthesize novel monodispersed SnO2@N‐doped carbon hollow nanoclusters as a high‐performance anode material for lithium‐ion batteries was explored. The uniqueness of this structure results from the large amount of ultrafine small SnO2 nanoparticles, the hollow interior space, and the continuous N‐doped carbon shells, which successfully buffer problems associated with huge volume changes and guarantee electrical connectivity. All of these features make the nanocomposite well fitted for lithium storage. As a result, the electrochemical performance of monodispersed SnO2@N‐doped carbon hollow nanoclusters as an anode in lithium‐ion batteries is significantly improved, as it shows high initial discharge and charge capacities of 1572 and 1003 mA h g–1, respectively. Importantly, nearly 100 % discharge/charge efficiency is maintained during 100 consecutive cycles with a specific capacity above 910 mA h g–1.

In vitro controlled release of cisplatin from gold-carbon nanobottles via cleavable linkages.

Carbon nanotubes’ (CNTs) hollow interior space has been explored for biomedical applications, such as drug repository against undesirable inactivation. To further devise CNTs as smart material for controlled release of cargo molecules, we propose the concept of “gold-carbon nanobottles”. After encapsulating cis-diammineplatinum(II) dichloride (cisplatin, CDDP) in CNTs, we covalently attached gold nanoparticles (AuNPs) at the open-tips of CNTs via different cleavable linkages, namely hydrazine, ester, and disulfide-containing linkages. Compared with our previous study in which more than 80% of CDDP leaked from CNTs in 2 hours, AuNPs were found to significantly decrease such spontaneous release to <40%. In addition, CDDP release from AuNP-capped CNTs via disulfide linkage was selectively enhanced by twofolds in reducing conditions (namely with 1 mM dithiothreitol [DTT]), which mimic the intracellular environment. We treated human colon adenocarcinoma cells HCT116 with our CDDP-loaded gold-carbon nanobottles and examined the cell viability using lactate dehydrogenase assay. Interestingly, we found that our nanobottles with cleavable disulfide linkage exerted stronger cytotoxic effect in HCT116 compared with normal human fetal lung fibroblast cells IMR-90. Therefore, we infer that our nanobottles strategy with inbuilt disulfide linkage could attain selective release of payload in highly reductive tumor tissues while avoiding collateral damage to normal tissues.

Bowl‐like SnO2@Carbon Hollow Particles as an Advanced Anode Material for Lithium‐Ion Batteries

AbstractDespite the great advantages of hollow structures as electrodes for lithium‐ion batteries, one apparent common drawback which is often criticized is their compromised volumetric energy density due to the introduced hollow interior. Here, we design and synthesize bowl‐like SnO2@carbon hollow particles to reduce the excessive hollow interior space while retaining the general advantages of hollow structures. As a result, the tap density can be increased about 30 %. The as‐prepared bowl‐like SnO2@carbon hollow particles with conformal carbon support exhibit excellent lithium storage properties in terms of high capacity, stable cyclability and excellent rate capability.

Bowl-like SnO2 @carbon hollow particles as an advanced anode material for lithium-ion batteries.

Despite the great advantages of hollow structures as electrodes for lithium-ion batteries, one apparent common drawback which is often criticized is their compromised volumetric energy density due to the introduced hollow interior. Here, we design and synthesize bowl-like SnO2 @carbon hollow particles to reduce the excessive hollow interior space while retaining the general advantages of hollow structures. As a result, the tap density can be increased about 30 %. The as-prepared bowl-like SnO2 @carbon hollow particles with conformal carbon support exhibit excellent lithium storage properties in terms of high capacity, stable cyclability and excellent rate capability.

Magneto-plasmonic nanoparticles as theranostic platforms for magnetic resonance imaging, drug delivery and NIR hyperthermia applications.

PEGylated magneto-plasmonic nanoparticles with a hollow or semi-hollow interior have been successfully synthesized and their physico-chemical characteristics have been investigated. The hollow interior space can be used to store drugs or other molecules of interest whereas magnetic characterization shows their potential as contrast agents in magnetic resonance imaging (MRI) applications. In addition, their plasmonic characteristics in the near infrared (NIR) region make them efficient in photothermal applications producing high temperature gradients after short irradiation times. We show that by controlling the etching conditions the inner silica shell can be selectively dissolved to achieve a hollow or semi-hollow interior without compromising the magnetic or plasmonic characteristics of the resulting nanoparticles. Magnetic measurements and transmission electron microscopy observations have been used to demonstrate the precise control during the etching process and to select an optimal concentration of the etching reagent and contact time to preserve the inner superparamagnetic iron oxide-based nanoparticles and the plasmonic properties of the constructs. Drug loading capabilities were also evaluated for both semi-hollow and as-synthesized nanoparticles using Rhodamine B isothiocyanate as a model compound. The nanoparticles produced could be potentially used as "theranostic" nanoparticles with both imaging capabilities and a dual therapeutic function (drug delivery and hyperthermia).

One-pot preparation and enhanced photocatalytic and electrocatalytic activities of ultralarge Ag/ZnO hollow coupled structures

Inorganic nanostructures with hollow interior space have aroused great research interests in recent years. However, most reported works so far possess relatively small particle sizes since the hollow materials with large interior cavities and thin walls are low in mechanical strength and prone to collapse. In this work, we report an ultralarge-sized Ag/ZnO hollow coupled structure, which has a diameter as large as 3–4 μm and length reaching 6–8 μm. In particular, the coupled structure is built from two identical single-crystal truncated pyramids which show highly uniform morphologies with good and complete shells, indicating strong enough structures and well preserved hollow interior spaces. On the basis of our investigations, the time-dependent hollowing can be well attributed to the Ostwald ripening process. The photocatalytic degradation of Rhodamine B shows that the obtained Ag/ZnO hollow-structured composite exhibits higher photodegradation efficiency than that of the ZnO product. The Ag/ZnO hollow nanostructures modified electrode also displays excellent electrocatalytic response for the detection of hydrogen peroxide (H2O2), exhibiting about 18 times higher sensitivity than the bare electrode. The approach of one-pot preparation provides a potential method to fabricate other oxide or metal/oxide hollow structures.

Zinc phthalocyanine hierarchical nanostructure with hollow interior space: Solvent–thermal synthesis and high visible photocatalytic property

A novel zinc phthalocyanine (ZnPc) hierarchical nanostructure with hollow interior space has been successfully obtained by a facile ethylene glycol solvent–thermal synthetic route. The as-obtained products were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), IR spectrum, UV–vis spectrum, Brunauer–Emmett–Teller analysis and contact angle measurement. It was indicated that the ZnPc micro-rectangular tubes with hollow interior space were built from densely nanosheets with a thickness of about 20 nm. The obtained ZnPc showed high visible photocatalytic property to degrade rhodamine B (RB), which could be ascribed to the contribution of hierarchical nanostructure, high crystallinity and super-hydrophobic property.

Rapid room-temperature fabrication of Cu2O–Au core–shell nanospheres

A facile, template-free method is reported to prepare Cu2O/Au core–shell nanospheres in aqueous medium at room temperature. In this synthesis, Cu2O nanospheres with definite diameter were first synthesized via the reduction reaction between Cu(NO3)2 and hydrazine (N2H4). Then, the as-prepared Cu2O nanospheres were employed as nucleation centers for deposition of Au shell, resulting in the formation of core–shell nanospheres. The samples obtained at various stages after the addition of the HAuCl4 were studied by TEM observation. These TEM images revealed that the formation hollow interior space between the core and the shell. In addition, UV–vis spectra results indicated that the optical property of the Cu2O/Au core–shell nanospheres was influenced by the size of the hollow interior spaces between the cores and the shells.