We report the preparation and encapsulation properties of stimuli-responsive nanocapsules, self-assembled by the noncovalent interactions of cyclodextrinappended polymers (host) and complementary ferrocene or azobenzene carriers (guest). The encapsulation process was significantly accelerated by applying (electro) chemical or light stimulus, enabling the easier and faster diffusion of guest molecules through the polymer layers. The nanocapsules were characterized by dynamic light scattering, confocal microscopy, ESEM, AFM, UV–visible and fluorescence spectroscopy, and electrochemical techniques. The encapsulation and release properties of the nanocapsules were reversible and could be repeated several times, indicating that the prepared nanoassemblies are very stable.
Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles.However,metal-organic frameworks(MOFs)have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement,although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite.Here,we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework(ZIF)through chemical etching and regrowth,followed by quantitative analysis in the core dimension and curvature.We find the nanorod core shows template-effective behavior in its morphological transformation.In the etching event,the nanorod core is spherically carved from its tips.The regrowth on the spherically etched core inside the ZIF gives rise toformation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition.We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell,intercrystalline gaps in mult-domain ZIF shells,and local structural deformation from the acidic reaction conditions. 相似文献
For the first time, chitin microspheres woven from nanowires with multi-scale porous structures were used as an excellent support for a catalyst of ultra-small Pd clusters. The Pd species anchored on the precursor Pre-Pd@chitin were 0.6 nm in average size, while the reduced catalyst Red-Pd@chitin featured ultra-small particles of 1.3 nm in average size. X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) demonstrated that the Pd catalyst in both oxidative and reductive states retained good dispersity and ultra-small clusters. The catalyst was tested for the hydrogenation of p-nitroanisole, exhibiting an excellent initial rate (13× that of commercial Pd/C)and excellent turnover frequency reaching 52,000 h?1. Furthermore, the catalyst could be recycled and used more than 10 times with no decay of the catalytic activity, suggesting potential industrial applications.
Zinc-air batteries have recently attracted considerable interest owing to the larger storage capacity and lower cost compared to their lithium-ion counterparts. Electrode catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a critical role in the operation of rechargeable zinc-air batteries. Herein, we report a simple and scalable strategy to fabricate porous carbon polyhedra using Zn-doped Co-based zeolitic imidazolate frameworks (ZnCo-ZIFs) as precursors. Strikingly, Zn doping leads to smaller Co nanoparticles and higher nitrogen content, which in turn enhances the ORR and OER activities of the obtained porous carbon polyhedra. The synergistic effect of the N-doped carbon and cobalt nanoparticles in the composite, the improved conductivity resulting from the high graphitization of carbon, and the large surface area of the porous polyhedral structure resulted in porous carbon polyhedra with excellent ORR and OER electrocatalytic activity in alkaline media. More importantly, air cathodes based on the optimal porous carbon polyhedra further exhibited superior performance to Pt/C catalysts in primary and rechargeable zinc-air batteries.
Multidrug resistance(MDR)restricts chemotherapy efficacy due to P-glycoprotein(P-gp)mediated drug efflux,whereas current approaches to suppressing P-gp expression suffer from intrinsic challenges,such as low transfection,high toxicity and poor specificity.Here,hollow ferric-tannic acid complex nanocapsules(HFe-TA),which can be effectively degraded by the reaction with adenosine triphosphate(ATP),are synthesized for the delivery of glucose oxidase(GOx)and doxorubicin(DOX)for tumor treatment.The findings indicate that the intracellular ATP is significantly decreased due to the combined effect of HFe-TA degradation and GOx-mediated glucose consumption.Along with this ATP down-regulation,P-gp expression of tumor cells is suppressed remarkably,which in turn promotes the intracellular accumulation and anticancer efficacy of DOX.In addition,the production of?OH by Fe ions released from HFe-TA is promoted by the by-products of the oxidation of glucose process by GOx.In consequence,HFe-TA nanocapsules loaded with DOX and GOx enable significant inhibition effect to tumors both in vitro and in vivo due to the synergistic effect of cascade reactions.This study has therefore provided an alternative therapeutic platform for effective tumor inhibition with the potential in overcoming intrinsic MDR. 相似文献
In this work, the influences of dielectrics with light absorption on the photonic bandgaps (PBGs) of porous alumina photonic crystals (PCs) were studied. Transmittance spectra of porous alumina PCs adsorbing ethanol showed that all the PBGs positions red-shifted; however, the transmittance of the PBG bottom showed different trends when the PBGs were located in different wavelength regions. In the near infrared region, liquid ethanol has strong light absorption, and, with the increase in adsorption, the PBG bottom transmittance of porous alumina PCs first increased and then decreased. However, in the visible light region, liquid ethanol has little light absorption, and thus, with the increase in adsorption, the PBG bottom transmittance of porous alumina PCs increased gradually all the time. Simulated results were consistent with the experimental results. The capillary condensation of organic vapors in the pores of porous alumina accounted for the change in the PBG bottom transmittance. The nonnegligible light absorption of the organic vapors was the cause of the decrease in the transmittance. The results for porous alumina PC adsorbing methanol, acetone, and toluene further confirmed the influences of light absorption on the PBG bottomed transmittance.
With the increasing requirements of reliable and environmentally friendly energy resources, porous materials for sustainable energy conversion technologies have attracted intensive interest in the past decades. As an important block of porous materials, biomimetic smart nanochannels (BSN) have been developed rapidly into an attractive field for their well-tunable geometry and chemistry. With inspiration from nature, many works have been reported to utilize BSN to harvest clean energy. In this review, we summarize recent progress in the BSN for power harvesting from four parts of brief introduction of BSN, biological prototypes for power harvesting, BSN-based energy conversion, and conclusion and outlook. Overall, by learning from nature, exploiting new avenues and improving the performance of BSN, a number of exciting developments in the near future may be anticipated.
Despite the extensive application of porous nanostructures as oxygen electrocatalysts, it is challenging to synthesize single-metal state materials with porous structures, especially the ultrasmall ones due to the uniform diffusion of the same metal. Herein, we pioneer demonstrate a new size effect-based controllable synthesis strategy for the homogeneous Co nanokarstcaves assisted by Co-CN hybrids (CCHs). The preferential migration of cobalt atoms on the surface of small size zeolitic imidazolate framework (ZIF) with high surface energy during pyrolysis is the key factor for the formation of nanokarstcave structure. Furthermore, graphene can act as a diffusion barrier to prevent the agglomeration of nanoparticles in the synthesis process, which also plays an important role in the formation of porous nanostructures. In alkali media, CCHs achieve overpotential of 287 mV (@10 mA·cm−2) for oxygen evolution reaction (OER) and a half wave potential of 0.86 V (vs. RHE) for oxygen reduction reaction (ORR).
Iron sulfide is an attractive anode material for lithium-ion batteries (LIBs) due to its high specific capacity, environmental benignity, and abundant resources. However, its application is hindered by poor cyclability and rate performance, caused by a large volume variation and low conductivity. Herein, iron sulfide porous nanowires confined in an N-doped carbon matrix (FeS@N-C nanowires) are fabricated through a simple amine-assisted solvothermal reaction and subsequent calcination strategy. The as-obtained FeS@N-C nanowires, as an LIB anode, exhibit ultrahigh reversible capacity, superior rate capability, and long-term cycling performance. In particular, a high specific capacity of 1,061 mAh·g?1 can be achieved at 1 A·g?1 after 500 cycles. Most impressively, it exhibits a high specific capacity of 433 mAh·g?1 even at 5 A·g?1. The superior electrochemical performance is ascribed to the synergistic effect of the porous nanowire structure and the conductive N-doped carbon matrix. These results demonstrate that the synergistic strategy of combining porous nanowires with an N-doped carbon matrix holds great potential for energy storage.
We have studied the magnetic and electrical transport properties of epitaxial NiAs-type CrTe thin films grown on SrTiO3(111) substrates. Unlike rectangle hysteresis loops obtained from magnetic measurements, we have identified intriguing extra bump/dip features from anomalous Hall experiments on the films with thicknesses less than 12 nm. This observed Hall anomaly is phenomenologically consistent with the occurrence of a topological Hall effect(THE) in chiral magnets with a skyrmion phase. Furthermore, the THE contribution can be tuned by the film thickness, showing the key contribution of asymmetric interfaces in stabilizing Néel-type skyrmions. Our work demonstrates that a CrTe thin film on SrTiO3(111) substrates is a good material candidate for studying real-space topological transport.
Material properties are strongly dependent on material structure. The large diversity and complexity of material structures provide significant opportunities to improve the properties of the materials, expanding their applications. Here, we discuss the fabrication of a multifunctional silver film prepared by controlling the nucleation and growth of silver particles. Silver films with high hydrophobicity and antibacterial activity were fabricated by adopting an electrochemical approach. The dependence of the hydrophobic and antibacterial properties on the size and shape of the silver particles was first investigated. Small-sized silver particles exhibited a high antibacterial rate, while a porous silver film composed of dendritic particles showed a significant hydrophobic activity. By regulating the reaction time, current density, and silver salt concentration, a silver film with a contact angle of 150.9° and an antibacterial rate of 54.7% was synthesized. This study demonstrates that finding a compromise between different material structures is a suitable way to fabricate multifunctional devices.
Exploring lightweight microwave attenuation materials with strong and tunable wideband microwave absorption is highly desirable but remains a significant challenge. Herein, three-dimensional (3D) porous hybrid composites consisting of NiFe nanoparticles embedded within carbon nanocubes decorated on graphene oxide (GO) sheets (NiFe@C nanocubes@GO) as high-performance microwave attenuation materials have been rationally synthesized. The 3D porous hybrid composites are fabricated by a simple method, which involves one-step pyrolysis of NiFe Prussian blue analogue nanocubes in the presence of GO sheets. Benefiting from the unique structural features that exhibit good magnetic and dielectric losses as well as a proper impedance match, the resulting NiFe@C nanocubes@GO composites show excellent microwave attenuation ability. With a minimum reflection loss (RL) of–51 dB at 7.7 GHz at a thickness of 2.8 mm and maximum percentage bandwidth of 38.6% for RL <–10 dB at a thickness of 2.2 mm, the NiFe@C nanocubes@GO composites are superior to the previously reported state-of-the-art carbon-based microwave attenuation materials.
The present study explored a new method to improve the catalytic activity of non-precious metals, especially in electrochemical reactions. Highly ionized Fe plasma produced by arc discharge was uniformly deposited on a porous carbon substrate and formed atomic clusters on the carbon surface. The as-prepared FeOx/C material was tested as a cathode material in a rechargeable Li–O2 battery under different current rates. The results showed significant improvement in battery performance in terms of both cycle life and reaction rate. Furthermore, X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the as-prepared cathode material stabilized the cathode and reduced side reactions and that the current rate was a critical factor in the nucleation of the discharge products.
To commercialize fuel cells and metal-air batteries, cost-effective, highly active catalysts for the oxygen reduction reaction (ORR) must be developed. Herein, we describe the development of low-cost, heteroatom (N, P, Fe) ternary-doped, porous carbons (HDPC). These materials are prepared by one-step pyrolysis of natural tea leaves treated with an iron salt, without any chemical and physical activation. The natural structure of the tea leaves provide a 3D hierarchical porous structure after carbonization. Moreover, heteroatom containing organic compounds in tea leaves act as precursors to functionalize the resultant carbon frameworks. In addition, we found that the polyphenols present in tea leaves act as ligands, reacting with Fe ions to form coordination compounds; these complexes acted as the precursors for Fe and N active sites. After pyrolysis, the as-prepared HDPC electrocatalysts, especially HDPC-800 (pyrolyzed at 800 °C), had more positive onsets, half-wave potentials, and higher catalytic activities for the ORR, which proceeds via a direct four-electron reaction pathway in alkaline media, similar to commercial Pt/C catalysts. Furthermore, HDPC-X also showed enhanced durability and better tolerance to methanol crossover and CO poisoning effects in comparison to commercial Pt/C, making them promising alternatives for state-of-the-art ORR electrocatalysts for electrochemical energy conversion. The method used here provides valuable guidelines for the design of high-performance ORR electrocatalysts from natural sources at the industrial scale.
We developed a high-efficiency rotating triboelectric nanogenerator (R-TENG)-enhanced multilayered antibacterial polyimide (PI) nanofiber air filters for removing ultrafine particulate matter (PM) from ambient atmosphere. Compared to single-layered PI nanofiber filters, the multilayered nanofiber filter can completely remove all of the particles with diameters larger than 0.54 μm and shows enhanced removal efficiency for smaller PM particles. After connecting with aR-TENG, the removal efficiency of the filer for ultrafine particles is further enhanced. The highest removal efficiency for ultrafine particulate matter is 94.1% at the diameter of 53.3 nm and the average removal efficiency reached 89.9%. Despite an increase in the layer number, the thickness of each individual layer of the film decreased, and hence, the total pressure drop of the filter decreased instead of increasing. Moreover, the nanofiber film exhibited high antibacterial activity because of the addition of a small amount of silver nanoparticles. This technology with zero ozone release and low pressure drop is appropriate for cleaning air, haze treatment, and bacterial control.
A solvent annealing-induced structural reengineering approach is exploited to fabricate polymersomes from block copolymers that are hard to form vesicles through the traditional solution self-assembly route. More specifically, polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) particles with sphere-within-sphere structure (SS particles) are prepared by three-dimensional (3D) soft-confined assembly through emulsion-solvent evaporation, followed by 3D soft-confined solvent annealing upon the SS particles in aqueous dispersions for structural engineering. A water-miscible solvent (e.g., THF) is employed for annealing, which results in dramatic transitions of the assemblies, e.g., from SS particles to polymersomes. This approach works for PS-b-P4VP in a wide range of block ratios. Moreover, this method enables effective encapsulation/loading of cargoes such as fluorescent dyes and metal nanoparticles, which offers a new route to prepare polymersomes that could be applied for cargo release, diagnostic imaging, and nanoreactor, etc.
A facile approach for the heterogenization of transition metal catalysts using non-covalent interactions in hollow click-based porous organic polymers (H-CPPs) is presented. A catalytically active cationic species, [Ru(bpy)3]2+ (bpy = 2,2’-bipyridyl), was immobilized in H-CPPs via electrostatic interactions. The intrinsic properties of [Ru(bpy)3]2+ were well retained. The resulting Rucontaining hollow polymers exhibited excellent catalytic activity, enhanced stability, and good recyclability when used for the oxidative hydroxylation of 4-methoxyphenylboronic acid to 4-methoxyphenol under visible-light irradiation. The attractive catalytic performance mainly resulted from efficient mass transfer and the maintenance of the chemical properties of the cationic Ru complex in the H-CPPs.
Shaping crystalline porous materials such as metal organic frameworks (MOFs) and zeolites into two-dimensional (2D) nanosheet forms is highly desirable for developing high-performance molecular sieving membranes. However, conventional exfoliation–deposition is complex and challenging for the large-scale fabrication of nanosheet MOF tubular membranes. Here, for the first time, we report a direct growth technique by ZnO self-conversion and ammonia assistance to fabricate zeolitic imidazolate framework (ZIF) membranes consisting of 2D nanosheets on porous hollow fiber substrates; the membranes are suitable for large-scale industrial gas separation processes. The proposed fabrication process for ZIF nanosheet membranes is based on the localized self-conversion of a pre-deposited thin layer of ZnO in a ligand solution containing ammonium hydroxide as a modulator. The resulting ZIF 2D nanosheet tubular membrane is highly oriented and only 50 nm in thickness. It exhibits excellent molecular sieving performance, with high H2 permeance and selectivity for H2/CO2 separation. This technique shows great promise in MOF nanosheet membrane fabrication for large-scale molecular sieving applications.
Advances in metal-organic frameworks (MOFs) resulted in significant contributions to diverse applications such as carbon capture, gas storage, heat transformation and separation along with emerging applications toward catalysis, medical imaging, drug delivery, and sensing. The unique in situ and ex situ structural features of MOFs can be tailored by conceptual selection of the organic (e.g., ligand) and inorganic (e.g., metal) components. Here, we provide a comprehensive review on the synthesis and characterization of MOFs, particularly with respect to controlling their size and morphology. A better understanding of the specific size and morphological parameters of MOFs will help initiate a new era for their real-world applications. Most importantly, this assessment will help develop novel synthesis methods for MOFs and their hybrid/porous materials counterparts with considerably improved properties in targeted applications.
Finding inexpensive electrodes with high activity and stability is key to realize the practical application of fuel cells. Here, we report the fabrication of three-dimensional (3D) porous nickel nanoflower (3D-PNNF) electrodes via an in situ reduction method. The 3D-PNNF electrodes have a high surface area, show tight binding to the electroconductive substrate, and most importantly, have superaerophobic (bubble repellent) surfaces. Therefore, the electrocatalytic hydrazine oxidation performance of the 3D-PNNF electrodes was much higher than that of commercial Pt/C catalysts because of its ultra-weak gas-bubble adhesion and ultra-fast gas-bubble release. Furthermore, the 3D-PNNF electrodes showed ultra-high stability even under a high current density (260 mA/cm2), which makes it promising for practical applications. In addition, the construction of superaerophobic nanostructures could also be beneficial for other gas evolution processes (e.g., hydrogen evolution reaction).
