Formation of CoS2Nanobubble Hollow Prisms for Highly Reversible Lithium Storage

Hollow Carbon-Based Nanoarchitectures Based on ZIF: Inward/Outward Contraction Mechanism and Beyond

Hollow carbon-based nanoarchitectures (HCAs) derived from zeolitic imidazolate frameworks (ZIFs), by virtue of their controllable morphology and dimension, high specific surface area and nitrogen content, richness of metal/metal compounds active sites, and hierarchical pore structure and easy exposure of active sites, have attracted great interests in many fields of applications, especially in heterogeneous catalysis, and electrochemical energy storage and conversion. Despite various approaches that have been developed to prepare ZIF-derived HCAs, the hollowing mechanism has not been clearly disclosed. Herein, a specialized overview of the recent progress of ZIF-derived HCAs is introduced to provide an insight into their preparation strategy and the corresponding hollowing mechanisms. Based on the fundamental understanding of the structural evolution of ZIF nanocrystals during the high-temperature pyrolysis process, the hollowing mechanisms of ZIF-derived HCAs are classified into four categories: i) inward contraction of core-shell template@ZIF composites or hollow ZIFs, ii) outward contraction of ZIF@shell composites, iii) special outward contraction of ZIF arrays, and iv) mechanism beyond inward/outward contraction of pure ZIF nanocrystals. Finally, an outlook on the development prospects and challenges of HCAs based on ZIF precursors, especially in terms of controlled synthesis and future electrochemical application, is further discussed.

Enhanced non-enzymatic glucose sensing based on porous ZIF-67 hollow nanoprisms

Porous ZIF-67 hollow nanoprisms based non-enzymatic glucose sensor was successfully prepared using Co₅(OH)₂(OAc)₈·2H₂O as a precursor by a diffusion-controlled strategy, which exhibited wide linear range and high sensitivity.

Hierarchical CoS2/N-Doped Carbon@MoS2 Nanosheets with Enhanced Sodium Storage Performance

We introduce a hierarchical nanostructure of CoS₂/N-doped carbon@MoS₂ comprising two transition-metal sulfides CoS₂ and MoS₂, with enhanced sodium storage performance in sodium-ion batteries. A micron-sized Co metal-organic framework (MOF) is transformed into a CoS₂/N-doped carbon composite, followed by a solvothermal growth of MoS₂ nanosheets on the surface. The resulting composite material offers several specific advantages for sodium storage: (i) accelerated sodium-ion diffusion kinetics due to its heterogeneous interface; (ii) shortened ion diffusion path and exposed active sites for sodium storage due to its hierarchical nanosheet architecture; and (iii) homogeneous nitrogen doping of the MOF-derived carbon, which is beneficial for electronic conductivity. Due to these merits, this composite exhibits excellent electrochemical performance with a specific capacity of 596 mAh g^-1 after 100 cycles at 0.1 A g^-1 and 395 mAh g^-1 at 5.0 A g^-1.

Topochemical synthesis of low-dimensional nanomaterials

Over the past several decades, nanomaterials have been extensively studied owing to having a series of unique physical and chemical properties that exceed those of conventional bulk materials. Researchers have developed a lot of strategies for the synthesis of low-dimensional nanomaterials. Among them, topochemical synthesis has attracted increasing attention because it can provide more new nanomaterials by improving and upgrading inexpensive and accessible nanomaterials. In this review, we summarize and analyze many existing topochemical synthesis methods, including selective etching, liquid phase reactions, high-temperature atmosphere reactions, electrochemically assisted methods, etc. The future direction of topochemical synthesis is also proposed.

Ultrathin Nanosheet-Assembled Co-Fe Hydroxide Nanotubes: Sacrificial Template Synthesis, Topotactic Transformation, and Their Application as Electrocatalysts for Efficient Oxygen Evolution Reaction

Hydrogen as a reliable, sustainable, and efficient energy carrier can effectively alleviate global environmental issues and energy crisis. However, the electrochemical splitting of water for large-scale hydrogen generation is still impeded by the sluggish kinetics of the oxygen evolution reaction (OER) at the anode. Considering the synergistic effect of Co and Fe on the improvement of OER catalytic activity, we prepared Co-Fe hydroxide nanotubes through a facile sacrificial template route. The resultant Co_0.8Fe_0.2 hydroxide nanotubes exhibited remarkable electrocatalytic performance for OER in 1.0 M KOH, with a small overpotential of about 246 mV at 10 mA cm^-2 and a Tafel slope of 53 mV dec^-1. The Co_0.8Fe_0.2P nanotubes were further prepared by a phosphidation treatment, exhibiting excellent OER catalytic performance with an overpotential as low as 240 mV at 10 mA cm^-2. Besides, the Co_0.8Fe_0.2P nanotubes supported on a Ni foam (Co_0.8Fe_0.2P/NF) used as both positive and negative poles in a two-electrode system achieved a cell voltage of about 1.67 V at 10 mA cm^-2 and exhibited outstanding stability. A water splitting system was constructed by Co_0.8Fe_0.2P/NF electrodes connected with a crystalline silicon solar cell, demonstrating the application as an electrocatalyst.

Hierarchically Hollow and Porous NiO/NiCo2O4 Nanoprisms Encapsulated in Graphene Oxide for Lithium Storage

Engineering materials nanostructures is key for developing renewable energy technologies for lithium-ion batteries (LIBs) but remains a long-term research challenge. In this paper, heterostructured NiO/NiCo₂O₄ nanoprisms with a hierarchically hollow cavity and porous framework are rationally designed and further encapsulated in graphene oxide (NiO/NiCo₂O₄@GO) as a highly efficient anode nanomaterial for LIBs. Heterostructured NiO/NiCo₂O₄ hollow/porous nanoprisms are derived by the ionic exchange of Ni precursors with [Co(CN)₆]^3- (CoNi-metal-organic framework (MOF)) and then annealed under air. The encapsulation is achieved by fast assembly of GO and NiO/NiCo₂O₄. Thanks to hierarchically hollow and porous nanostructure, heterostructured NiO/NiCo₂O₄, and overcoated GO, the NiO/NiCo₂O₄ electrode shows excellent electrochemical performance toward lithium storage, disclosing a large rate capacity of 468 mA h g^-1 at 3.0 A g^-1 and a good capacity retention of 561 mA h g^-1 at 1 A g^-1 after 800 cycles. This work paves a facile ionic exchange method for the controllable construction of hierarchically hollow MOFs and their derived composite nanomaterials for various energy-related applications.

Boosting Transport Kinetics of Cobalt Sulfides Yolk-Shell Spheres by Anion Doping for Advanced Lithium and Sodium Storage

Cobalt sulfides have been popularly used in energy storage because of their high theoretical capacity and abundant redox reactions. However, poor reaction kinetics, rapid capacity decay, and severe polarization owing to volume changes during electrochemical reaction are still huge challenges for cobalt sulfides in practical applications. Herein, cobalt sulfide yolk-shell spheres were synthesized by phosphorus doping (P-CoS) to stabilize the structure of cobalt sulfides and improve their electronic/ion conductivity. Kinetic tests and density functional theory calculations confirm that the introduction of phosphorus into cobalt sulfides greatly reduces the diffusion barrier of Li⁺ in the intrinsic structure, thereby improving the reaction kinetics of electrode materials during the Li⁺ insertion/extraction process. In consequence, the P-CoS electrode delivers a high lithium storage capacity (781 mAh g^-1 after 100 cycles at 0.2 A g^-1 ), excellent rate capability (489 mAh g^-1 at 10 A g^-1 ), and outstanding cycling stability (no significant capacity decay over 4000 cycles at 5 A g^-1 ). Especially for sodium-ion battery application, the P-CoS electrode expresses a striking capacity of approximately 260 mAh g^-1 at 2 A g^-1 after 900 cycles.

Recent progress on hollow array architectures and their applications in electrochemical energy storage

The structural design of electrode materials is one of the most important factors that determines the electrochemical performance of energy storage devices. In recent years, hollow micro-/nanoarray structures have been widely explored for energy applications due to their unique structural advantages. Their complex hollow interior and shell arrays enable fast ion diffusion/transport, provide abundant active sites and accommodate volume changes. Moreover, the direct contact of hollow arrays with substrates enhances the mechanical stability during long-term cycling. To date, huge progress has been achieved in the rational design of various hollow array architectures. However, a review on this topic has been rarely reported. Herein, the multifunctional merits and typical synthetic strategies for hollow array structures are analyzed in detail. Furthermore, their applications in electrochemical energy storage (such as supercapacitors and batteries) are summarized. The development and challenges of hollow arrays in terms of substrates, technique improvement and material innovation are discussed. Finally, their applications for energy storage and conversion are prospected.

A computational exploration of the 1D TiS2(en) nanostructure for lithium ion batteries

First-principles investigations on 1D TiS₂(en) are performed to evaluate its potential as an electrode for lithium ion batteries. The intercalation of lithium ions into Li_xTiS₂(en) follows the Rüdorff model and the lithium ions are predicted to diffuse along the one-dimensional axis of the TiS₂(en) nanostructure with a small diffusion barrier of 0.27 eV.

Hydrangea-Like CuS with Irreversible Amorphization Transition for High-Performance Sodium-Ion Storage

Metal sulfides have been intensively investigated for efficient sodium-ion storage due to their high capacity. However, the mechanisms behind the reaction pathways and phase transformation are still unclear. Moreover, the effects of designed nanostructure on the electrochemical behaviors are rarely reported. Herein, a hydrangea-like CuS microsphere is prepared via a facile synthetic method and displays significantly enhanced rate and cycle performance. Unlike the traditional intercalation and conversion reactions, an irreversible amorphization process is evidenced and elucidated with the help of in situ high-resolution synchrotron radiation diffraction analyses, and transmission electron microscopy. The oriented (006) crystal plane growth of the primary CuS nanosheets provide more channels and adsorption sites for Na ions intercalation and the resultant low overpotential is beneficial for the amorphous Cu-S cluster, which is consistent with the density functional theory calculation. This study can offer new insights into the correlation between the atomic-scale phase transformation and macro-scale nanostructure design and open a new principle for the electrode materials' design.

Fabrication of Hierarchical Co9S8@ZnAgInS Heterostructured Cages for Highly Efficient Photocatalytic Hydrogen Generation and Pollutants Degradation

In the present study, a hierarchical Co₉S₈@ZnAgInS heterostructural cage was developed for the first time which can photocatalytically produce hydrogen and degrade organic pollutants with high efficiency. First, the Co₉S₈ dodecahedron was synthesized using a metal-organic framework (MOFs) material, ZIF-67, as a precursor, then two kinds of metal sulfide semiconductors were elaborately integrated into a hierarchical hollow heterostructural cage with coupled heterogeneous shells and 2D nanosheet subunits. The artfully designed hollow heterostructural composite exhibited remarkable photocatalytic activity without using any cocatalysts, with a 9395.3 μmol g^-1 h^-1 H₂ evolution rate and high degradation efficiency for RhB. The significantly enhanced photocatalytic activity can be attributed to the unique architecture and intimate-contact interface between Co₉S₈ and ZnAgInS, which promote the transfer and separation of the photogenerated charges, increase light absorption, and offer large surface area and active sites. This work presents a new strategy to design highly active semiconductor photocatalysts by using MOF materials as precursors and coupling of metal sulfide semiconductors to form hollow architecture dodecahedron cages with an intimate interface.

Optimized Metal Chalcogenides for Boosting Water Splitting

Electrocatalytic water splitting (2H2O → 2H2 + O2) is a very promising avenue to effectively and environmentally friendly produce highly pure hydrogen (H2) and oxygen (O2) at a large scale. Different materials have been developed to enhance the efficiency for water splitting. Among them, chalcogenides with unique atomic arrangement and high electronic transport show interesting catalytic properties in various electrochemical reactions, such as the hydrogen evolution reaction, oxygen evolution reaction, and overall water splitting, while the control of their morphology and structure is of vital importance to their catalytic performance. Herein, the general synthetic methods are summarized to prepare metal chalcogenides and different strategies are designed to improve their catalytic performance for water splitting. The remaining challenges in the research and development of metal chalcogenides and possible directions for future research are also summarized.

The Progress of Cobalt-Based Anode Materials for Lithium Ion Batteries and Sodium Ion Batteries

Limited by the development of energy storage technology, the utilization ratio of renewable energy is still at a low level. Lithium/sodium ion batteries (LIBs/SIBs) with high-performance electrochemical performances, such as large-scale energy storage, low costs and high security, are expected to improve the above situation. Currently, developing anode materials with better electrochemical performances is the main obstacle to the development of LIBs/SIBs. Recently, a variety of studies have focused on cobalt-based anode materials applied for LIBs/SIBs, owing to their high theoretical specific capacity. This review systematically summarizes the recent status of cobalt-based anode materials in LIBs/SIBs, including Li+/Na+ storage mechanisms, preparation methods, applications and strategies to improve the electrochemical performance of cobalt-based anode materials. Furthermore, the current challenges and prospects are also discussed in this review. Benefitting from these results, cobalt-based materials can be the next-generation anode for LIBs/SIBs.

Polypyrrole coated hollow S/Co-doped carbon nanocages excels for packaging high-performance lithium sulfur batteries

Although there are numerous virtues for lithium sulfur batteries, the notorious shuttle effect and insulated nature are impeding their practical application. To address these issues, here we report the design and synthesis of polypyrrole coated sulfur and cobalt co-doped carbon nanocages (PSCC). It demonstrates that both the performance and stability of the PSCC assisted Li-S batteries are improved. The hollow structure of PSCC bypassed the structural collapse effectively caused by volume expansion of sulfur during the reaction and physically suppressed shuttle effect of the intermediate product polysulfide lithium (LiPSs). Also, LiPSs was also trapped to inhibit the shuttle effect due to the strong adsorption of LiPSs via PSCC. In addition, PSCC can also provide an outstanding electronic conductivity, which will facilitate the next-step reaction of the absorbed LiPSs and enhance electrochemical reaction kinetics. Thus, the excellent rate performance was obtained with high specific discharge capacities of 1300 mAh g^-1 at 0.1 C and 1000 mAh g^-1 at 0.5 C. Such packaged high-performance positions our design for the ideal electrochemical energy storage devices.

Highly pseudocapacitive metal-organic framework derived carbon skeleton supported Fe-Ti-O nanotablets as an anode material for efficient lithium storage

A facile and effective method to fabricate highly pseudocapacitive electrodes of Fe-Ti-O@C has been proposed here. In this strategy, FeOOH crystals were firstly grown uniformly on the surface of Ti-based MOF (MIL-125) tablet substrates through a solution immersion method, and then converted to uniform carbon supported Fe-Ti-O composites by calcination under argon. The obtained Fe-Ti-O@C composites were first utilized as an efficient anode for lithium ion batteries with a high reversible capacity of 988 mA h g^-1 after 160 cycles at 200 mA g^-1. Such a superior lithium storage performance may be due to the synergistic effect of the Fe₃O₄ nanoparticles with a high capacity, FeTiO₃ nanocomposites with a nearly stable structure during the Li⁺ insertion/removal process, and the conductive carbon skeleton with a large surface area and porous structure. This work represents an important step forward in the fabrication of MOF-derived hybrids and enables transition metal oxides (TMOs) to have potential applications in energy storage systems.

Metal-Organic Framework Derived CoS2 Wrapped with Nitrogen-Doped Carbon for Enhanced Lithium/Sodium Storage Performance

Transition metal sulfides are attractive electrode materials for both lithium-ion (LIBs) and sodium-ion batteries (SIBs). Starting from micron-sized Co(IPC)·H₂O (IPC: 4-(imidazole-1-yl) phthalic acid) and polydopamine as the metal-organic framework (MOF) precursor and carbon source, respectively, we produced a CoS₂/C/C composite constituting CoS₂ nanoparticles decorated with N-doped carbon layers and subjected to sulfurization. N-doped carbon layers provided a robust network for the CoS₂ nanoparticles, enhancing the structural integrity and electronic conductivity of the resulting CoS₂/C/C composite, which exhibited electrochemical performance superior to most existing CoS₂ composites, and was one of the best among all MOF derived CoS₂ anodes for LIBs and SIBs. The use of nanosized CoS₂ particles reduced the diffusion length for the transfer of Li⁺/Na⁺ ions, resulting in a high specific capacity at a higher current rate. N-doped carbon layers derived from the MOF precursor and polydopamine provided an electrically conductive network between the CoS₂ nanoparticles, thus preventing their aggregation and inhibiting adverse side reactions between the electrolyte and the surface of the electrode, and the high pseudocapacitive contribution resulted in the enhanced rate performance of the CoS₂/C/C electrodes.

An integrated electrode based on nanoflakes of MoS2 on carbon cloth for enhanced lithium storage

Due to its high specific capacity (in theory), molybdenum disulfide (MoS₂) has been recognized as a plausible substitute in lithium-ion batteries (LIBs). However, it suffers from an inferior electric conductivity and a substantial volume change during Li⁺ insertion/extraction. By using a facile hydrothermal method, a flexible free-standing MoS₂ electrode has here been fabricated onto a carbon cloth substrate. The grafting of ultrathin MoS₂ nanoflakes onto the carbon cloth framework (forming CC@MoS₂), was shown to facilitate an improved electron transport, as well as an enhanced Li⁺ transport. As expected, the as-obtained CC@MoS₂ electrode was observed to exhibit an excellent lithium storage performance. It delivers a high discharge specific capacity of 2.42 mA h cm^-2 at 0.7 mA cm^-2 (even after 100 cycles), which is an impressive result.

Nanostructured metal chalcogenides confined in hollow structures for promoting energy storage

The engineering of progressive nanostructures with subtle construction and abundant active sites is a key factor for the advance of highly efficient energy storage devices. Nanostructured metal chalcogenides confined in hollow structures possess abundant electroactive sites, more ions and electron pathways, and high local conductivity, as well as large interior free space in a quasi-closed structure, thus showing promising prospects for boosting energy-related applications. This review focuses on the most recent progress in the creation of diverse confined hollow metal chalcogenides (CHMCs), and their electrochemical applications. Particularly, by highlighting certain typical examples from these studies, a deep understanding of the formation mechanism of confined hollow structures and the decisive role of microstructure engineering in related performances are discussed and analyzed, aiming at prompting the nanoscale engineering and conceptual design of some advanced confined metal chalcogenide nanostructures. This will appeal to not only the chemistry-, energy-, and materials-related fields, but also environmental protection and nanotechnology, thus opening up new opportunities for applications of CHMCs in various fields, such as catalysis, adsorption and separation, and energy conversion and storage.

A General Approach to Direct Growth of Oriented Metal-Organic Framework Nanosheets on Reduced Graphene Oxides

Ultrathin metal-organic framework nanosheets (UMOFNs) deposited on graphene are highly attractive, however direct growth of UMOFNs on graphene with controlled orientations remains challenging. Here, a low-concentration-assisted heterogeneous nucleation strategy is reported for the direct growth of UMOFNs on reduced graphene oxides (rGO) surface with controllable orientations. This general strategy can be applied to construct various UMOFNs on rGO, including Co-ZIF, Ni-ZIF, Co, Cu-ZIF and Co, Fe-ZIF. When UMOFNs are mostly attached perpendicularly on rGO, a 3D foam-like hierarchical architecture (named UMOFNs@rGO-F) is formed with an open pore structure and excellent conductivity, showing excellent performance as electrode materials for Li-ion batteries and oxygen evolution. The contribution has provided a strategy for improving the electrochemical performance of MOFs in energy storage applications.

A 1D Honeycomb-Like Amorphous Zincic Vanadate for Stable and Fast Sodium-Ion Storage

Developing nanomaterials with synergistic effects of various structural merits is considered to be an effective strategy to improve the sluggish ion kinetics and severe structural degradation of sodium-ion battery (SIB) anodes. Herein, honeycomb-like amorphous Zn₂ V₂ O₇ (ZVO-AH) nanofibers as SIBs anode material with plentiful defective sites, complex cavities, and good mechanical flexibility are reported. The fabrication strategy relies on the expansive and volatile nature of the organic vanadium source, based on a simple electrospinning with subsequent calcination. Originating from the synergies of amorphous nature and honeycomb-like cavities, ZVO-AH shows increased electrochemical activity, accelerated Na-ion diffusion, and robust structure. Impressively, the ZVO-AH anode delivers superior cycle stability (112% retention at 5 A g^-1 after 5000 cycles) and high rate capability (150 mAh g^-1 at 10 A g^-1 ). The synthetic versatility is able to synergistically promote the practical application of more potential materials in sodium-ion storage.

Facile and reversible digestion and regeneration of zirconium-based metal-organic frameworks

The digestion/regeneration of metal-organic frameworks (MOFs) has important applications for catalysis, drug delivery, environmental decontamination, and energy storage, among other applications. However, research in this direction is limited and very challenging. Here, we develop a facile method to digest and regenerate a series of zirconium-based metal-organic frameworks (Zr-MOFs) by bicarbonate or carbonate salts. As an example, UiO-66 demonstrates well the mechanism of reversible digestion/regeneration processes. By analyzing the digested zirconium species via X-ray diffraction, Fourier transform infrared spectroscopy and Raman scattering spectroscopy, a digestion mechanism based on the formation of dissoluble complexes [Zr₂(OH)₂(CO₃)₄]^2- is proposed. Impressively, ultrafine Pd nanoparticles can be extracted from Pd@PCN-224 via this strategy. This work, thus, may provide new insight for the development of renewable MOFs and their practical applications.

Self-template formation of porous Co3O4 hollow nanoprisms for non-enzymatic glucose sensing in human serum

A novel type of porous Co₃O₄ hollow nanoprism (HNP) was successfully prepared using tetragonal cobalt acetate hydroxide [Co₅(OH)₂(OAc)₈·2H₂O] as precursor by a facile solvothermal process and a subsequent calcination treatment. The morphology and structure of the Co₃O₄ HNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and N₂ adsorption–desorption measurements. An enzyme-free glucose sensor was constructed based on the Co₃O₄ HNPs, and the electrochemical performance was tested by cyclic voltammetry (CV) and chronoamperometry. The as-prepared sensor exhibited a good electrocatalytic activity for glucose oxidation at the applied potential of 0.6 V in alkaline solution, with a high sensitivity of 19.83 μA mM⁻¹ cm⁻² and a high upper limit of 30 mM, which provide the potential for direct determination of blood glucose without any dilution pretreatment. The Co₃O₄ HNPs had a porous and tubular structure with a large amount of accessible active sites, which enhanced the mass diffusion and accelerated the electron transfer. Moreover, the sensor also demonstrated a desirable stability, selectivity and reproducibility, and could verify the non-enzymatic analysis of glucose in real samples.

Co₃O₄ hollow nanoprisms based non-enzymatic glucose sensor were prepared by a self-template process, exhibiting wide linear range, good selectivity and stability, which can directly monitoring blood glucose without any dilution pretreatment.

Metal–organic framework-derived hollow structure CoS2/nitrogen-doped carbon spheres for high-performance lithium/sodium ion batteries

Hollow structure CoS₂/NC spheres derived from a porous Co-MOF precursor delivered long-term cycling stability as an anode for LIBs and SIBs.

ZIF-67-Derived CoSe/NC Composites as Anode Materials for Lithium-Ion Batteries

As a typical metal selenide, CoSe is a kind of foreground anode material for lithium-ion batteries (LIBs) because of its two-dimensional layer structure, good electrical conductivity, and high theoretical capacity. In this work, the original CoSe/N-doped carbon (CoSe/NC) composites were synthesized using ZIF-67 as a precursor, in which the CoSe nanoparticles are encapsulated in NC nanolayers and they are connected through C-Se bonds. The coating structure and strong chemical coupling make the NC nanolayers could better effectively enhance the lithium storage properties of CoSe/NC composites. As a consequence, the CoSe/NC composites deliver a reversible capacity of 310.11 mAh g^-1 after 500 cycles at 1.0 A g^-1. Besides, the CoSe/NC composites show a distinct incremental behavior of capacity.

Preparation Of Nanobubbles Modified With A Small-Molecule CXCR4 Antagonist For Targeted Drug Delivery To Tumors And Enhanced Ultrasound Molecular Imaging

Purpose

To construct nanobubbles (PTX-AMD070 NBs) for targeted delivery of paclitaxel (PTX) and AMD070, examine their performance in ultrasound molecular imaging of breast cancer and cervical cancer and their therapeutic effect combined with ultrasound targeted nanobubble destruction (UTND).

Materials and methods

PTX-AMD070 NBs were prepared via an amide reaction, and the particle size, zeta potential, encapsulation rate and drug loading efficiency were examined. Laser confocal microscopy and flow cytometry were used to analyze the targeted binding ability of PTX-AMD070 NBs to CXCR4⁺ MCF-7 cells and C33a cells. The effect of PTX-AMD070 NBs combined with UTND on cell proliferation inhibition and apoptosis induction was detected by CCK-8 assays and flow cytometry. The contrast-enhanced imaging features of PTX-AMD070 NBs and paclitaxel-loaded nanobubbles were compared in xenograft tumors. The penetration ability of PTX-AMD070 NBs in xenograft tissues was evaluated by immunofluorescence. The therapeutic effect of PTX-AMD070 NBs combined with UTND on xenograft tumors was assessed.

Results

PTX-AMD070 NBs showed a particle size of 494.3±61.2 nm, a zeta potential of −22.4±1.75 mV, an encapsulation rate with PTX of 53.73±7.87%, and a drug loading efficiency with PTX of 4.48±0.66%. PTX-AMD070 NBs displayed significantly higher targeted binding to MCF-7 cells and C33a cells than that of PTX NBs (P<0.05), and combined with UTND manifested a more pronounced effect in inhibiting cell proliferation and promoting apoptosis than other treatments. PTX-AMD070 NBs aggregated specifically in xenograft tumors in vivo, and significantly improved the image quality. Compared with other treatment groups, PTX-AMD070 NBs combined with UTND exhibited the smallest tumor volume and weight, and the highest degree of apoptosis and necrosis.

Conclusion

PTX-AMD070 NBs improved the ultrasound imaging effect in CXCR4⁺ xenograft tumors and facilitated targeted therapy combined with UTND. Therefore, this study provides an effective method for the integration of ultrasound molecular imaging and targeted therapy of malignant tumors.

Fabrication of an anode composed of a N, S co-doped carbon nanotube hollow architecture with CoS2 confined within: toward Li and Na storage

Over the years, transition metal chalcogenides (TMCs) have attracted ample attention from researchers on account of their high theoretical capacity, through which they show great potential for use in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Nevertheless, there are some serious obstacles (particle pulverization and large volume change) still in the way to achieving satisfactory cycling performance and rate property. Here, we report the preparation of a N, S co-doped carbon nanotube hollow architecture confining CoS₂ (CoS₂/NSCNHF) derived from bimetal-organic-frameworks. The rationally designed structure possesses excellent Li⁺/Na⁺ storage performances. Further investigation of the Li⁺/Na⁺ storage behavior indicated the presence of a partial pseudocapacitive contribution, facilitating the fast Li⁺/Na⁺ interaction/extraction process and thus giving it superb electrochemical property. This work may represent an important step forward in the fabrication of MOF-derived hierarchical hybrids combined with a hollow structure and TMCs to help such TMCs achieve their potential in energy storage systems.

Triple-Shelled Co-VSex Hollow Nanocages as Superior Bifunctional Electrode Materials for Efficient Pt-Free Dye-Sensitized Solar Cells and Hydrogen Evolution Reactions

Complex nanostructures with distinct spatial architectures and more active sites hold broad prospects in new energy conversion fields. Herein, a facile strategy was carried out to construct triple-shelled Co-VSe_x nanocages, starting with an ion-exchange process between Co-based zeolitic imidazolate framework-67 (ZIF-67) nanopolyhedrons and VO₃^- followed by the formation of triple-shelled Co-VSe_x hollow nanocages during the process of increasing the solvothermal temperature under the assistance of SeO₃^2-. Meanwhile, triple-shelled Co-VS_x and yolk-double shell Co-VO_x nanocages were fabricated as references by a similar process. Benefiting from the larger surface areas and more electrolyte adsorption sites, the triple-shelled Co-VSe_x nanocages exhibited excellent electrocatalytic performances when applied as the electrochemical catalysts for dye-sensitized solar cells (DSSC) and hydrogen evolution reactions (HER). More concretely, the DSSC based on the Co-VSe_x counter electrode showed outstanding power conversion efficiency of 9.68% when its Pt counterpart was 8.46%. Moreover, the Co-VSe_x electrocatalyst exhibited prominent HER performance with a low onset overpotential of 40 mV and a small Tafel slope of 39.1 mV dec^-1 in an acidic solution.

MOF-Derived CuS@Cu-BTC Composites as High-Performance Anodes for Lithium-Ion Batteries

The CuS(x wt%)@Cu-BTC (BTC = 1,3,5-benzenetricarboxylate; x = 3, 10, 33, 58, 70, 99.9) materials are synthesized by a facile sulfidation reaction. The composites are composed of octahedral Cu₃ (BTC)₂ ·(H₂ O)₃ (Cu-BTC) with a large specific surface area and CuS with a high conductivity. The as-prepared CuS@Cu-BTC products are first applied as the anodes of lithium-ion batteries (LIBs). The synergistic effect between Cu-BTC and CuS components can not only accommodate the volume change and stress relaxation of electrodes but also facilitate the fast transport of Li ions. Thus, it can greatly suppress the transformation process from Li₂ S to polysulfides by improving the reversibility of the conversion reaction. Benefiting from the unique structural features, the optimal CuS(70 wt%)@Cu-BTC sample exhibits a remarkably improved electrochemical performance, showing an over-theoretical capacity up to 1609 mAh g^-1 after 200 cycles (100 mA g^-1 ) with an excellent rate-capability of ≈490 mAh g^-1 at 1000 mA g^-1 . The outstanding LIB properties indicate that the CuS(70 wt%)@Cu-BTC sample is a highly desirable electrode material candidate for high-performance LIBs.

Defect-Enriched Nitrogen Doped-Graphene Quantum Dots Engineered NiCo2 S4 Nanoarray as High-Efficiency Bifunctional Catalyst for Flexible Zn-Air Battery

Flexible Zn-air batteries have recently emerged as one of the key energy storage systems of wearable/portable electronic devices, drawing enormous attention due to the high theoretical energy density, flat working voltage, low cost, and excellent safety. However, the majority of the previously reported flexible Zn-air batteries encounter problems such as sluggish oxygen reaction kinetics, inferior long-term durability, and poor flexibility induced by the rigid nature of the air cathode, all of which severely hinder their practical applications. Herein, a defect-enriched nitrogen doped-graphene quantum dots (N-GQDs) engineered 3D NiCo₂ S₄ nanoarray is developed by a facile chemical sulfuration and subsequent electrophoretic deposition process. The as-fabricated N-GQDs/NiCo₂ S₄ nanoarray grown on carbon cloth as a flexible air cathode exhibits superior electrocatalytic activities toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), outstanding cycle stability (200 h at 20 mA cm^-2 ), and excellent mechanical flexibility (without observable decay under various bending angles). These impressive enhancements in electrocatalytic performance are mainly attributed to bifunctional active sites within the N-GQDs/NiCo₂ S₄ catalyst and synergistic coupling effects between N-GQDs and NiCo₂ S₄ . Density functional theory analysis further reveals that stronger OOH* dissociation adsorption at the interface between N-GQDs and NiCo₂ S₄ lowers the overpotential of both ORR and OER.

One-step synthesis of cross-linked and hollow microporous organic-inorganic hybrid nanoreactors for selective redox reactions

Hollow microporous nanostructures (HMNs) are powerful platforms for multiple promising applications, including energy storage, drug/gene delivery, nanoreactors/catalysis, adsorption, and separation. Herein, we report a facile one-step method to synthesize highly cross-linked organic-inorganic hybrid poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) HMNs via a salt-induced liquid-liquid separation process. The size of inner cavities can be properly tuned by modulating the concentration of the NaOH solution. The regulation mechanism of the PZS HMNs was further confirmed by encapsulating water-dispersed Pt nanoclusters into the cavities. Interestingly, the resulting yolk-shell Pt@PZS serves as nanoreactors and exhibits excellent substrate selectivity and recyclability for the catalytic oxidation of 1,3,5-trimethylbenzene.

Shape-Defined Hollow Structural Co-MOF-74 and Metal Nanoparticles@Co-MOF-74 Composite through a Transformation Strategy for Enhanced Photocatalysis Performance

In recent years, metal-organic frameworks (MOFs) have received extensive interest because of the diversity of their composition, structure, and function. To promote the MOFs' function and performance, the construction of hollow structural metal-organic frameworks and nanoparticle-MOF composites is significantly effective but remains a considerable challenge. In this article, a transformation strategy is developed to synthesize hollow structural Co-MOF-74 by solvothermal transformation of ZIF-67. These Co-MOF-74 particles exhibit a double-layer hollow shell structure without remarkable shape change compared to original ZIF-67 particles. The formation of hollow structure stemmed from the density difference of Co between ZIF-67 and Co-MOF-74. By this strategy, hollow structural Co-MOF-74 with different sizes and shapes are obtained from corresponding ZIF-67, and metal nanoparticles@Co-MOF-74 is synthesized by corresponding nanoparticles@Co-ZIF-67. To verify the structural advantages of hollow structural Co-MOF-74 and Ag nanoparticles@Co-MOF-74, photocatalytic CO₂ reduction is used as a model reaction. Conventionally synthesized Co-MOF-74 (MOF-74-C), hollow structural Co-MOF-74 synthesized by transformation method (MOF-74-T) and Ag nanoparticles@Co-MOF-74 (AgNPs@MOF-74) are used as cocatalysts in this reaction. As a result, the cocatalytic activity of MOF-74-T and AgNPs@MOF-74 is 1.8 times and 3.8 times that of MOF-74-C, respectively.

High Capacity and Superior Rate Performances Coexisting in Carbon-Based Sodium-Ion Battery Anode

Amorphous carbon is considered as a prospective and serviceable anode for the storage of sodium. In this contribution, we illuminate the transformation rule of defect/void ratio and the restrictive relation between specific capacity and rate capability. Inspired by this mechanism, ratio of plateau/slope capacity is regulated via temperature-control pyrolysis. Moreover, pore-forming reaction is induced to create defects, open up the isolated voids, and build fast ion channels to further enhance the capacity and rate ability. Numerous fast ion channels, high ion-electron conductivity, and abundant defects lead the designed porous hard carbon/Co₃O₄ anode to realize a high specific capacity, prolonged circulation ability, and enhanced capacity at high rates. This research deepens the comprehension of sodium storage behavior and proposes a fabrication approach to achieve high performance carbonaceous anodes for sodium-ion batteries.

A facile sequential ion exchange strategy to synthesize CoSe2/FeSe2 double-shelled hollow nanocuboids for the highly active and stable oxygen evolution reaction

Transition metal-based nanostructures have been considered as promising substitutes for rare-earth metal oxide electrocatalysts toward the oxygen evolution reaction (OER). Herein, we report for the first time on a novel multicomponent metal selenide electrocatalyst based on CoSe2/FeSe2 double-shelled hollow nanocuboids (CoSe2/FeSe2 DS-HNCs) with the highly oxidative Co3+ species, which is synthesized via a facile sequential ion exchange strategy. The solid Co-precursor nanocuboids are first converted into the intermediate Co2[Fe(CN)6] with a mesoporous and double-shelled hollow structure produced through a facile ligand exchange at room temperature, and then the final CoSe2/FeSe2 DS-HNCs are obtained by a subsequent Se ion exchange reaction. The intermediate product of Co2[Fe(CN)6] plays an important role not only in constructing a double-shelled hollow structure but also in providing the Fe source for the growth of the final multicomponent metal selenides. Benefiting from the nanosized double-shelled hollow structure and mesoporous double-metal selenide shells with the highly oxidative Co3+ species, the as-prepared CoSe2/FeSe2 DS-HNCs exhibit superior OER performance to state-of-the-art metal selenides, including a small overpotential of 240 mV at a current density of 10 mA cm-2 and the excellent electrochemical durability over 50 h. This work opens up a new avenue towards developing highly active multicomponent noble-metal-free electrocatalysts.