Mesoporous Hollow Research Articles

Facile Synthesis of Boron and Nitrogen Dual-Doped Hollow Mesoporous Carbons for Efficient Reduction of 4-Nitrophenol.

The development of heteroatom-doped carbons with fascinating hierarchical porosity is of great significance for the improvement of catalytic properties of carbon catalysts. In this work, we report a boron and nitrogen codoped hollow mesoporous carbon (denoted as BN/HMC) via a simple synthesis route by direct pyrolysis of phenylboronic acid/melamine/ZIF-8 precursors. Thanks to their high specific surface area, unique hollow mesoporous nanoarchitecture, rich defects, and boron and nitrogen codoping, the obtained BN/HMC-0.05 can be employed as a high-efficiency carbon-based catalyst for the reduction of 4-nitrophenol. Theoretical calculations reveal that the B and N codoping in a carbon matrix are essential for the adsorption and activation of 4-nitrophenol. The present work might pave a new way in construction of metal-free carbon catalysts with both heteroatom doping and hierarchical porosity for various applications.

Construction of a Mesoporous Ceria Hollow Sphere/Enzyme Nanoreactor for Enhanced Cascade Catalytic Antibacterial Therapy.

Nanozyme has been regarded as one of the antibacterial agents to kill bacteria via a Fenton-like reaction in the presence of H2O2. However, it still suffers drawbacks such as insufficient catalytic activity in near-neutral conditions and the requirement of high H2O2 levels, which would minimize the side effects to healthy tissues. Herein, a mesoporous ceria hollow sphere/enzyme nanoreactor is constructed by loading glucose oxidase in the mesoporous ceria hollow sphere nanozyme. Due to the mesoporous framework, large internal voids, and high specific surface area, the obtained nanoreactor can effectively convert the nontoxic glucose into highly toxic hydroxyl radicals via a cascade catalytic reaction. Moreover, the generated glucose acid can decrease the localized pH value, further boosting the peroxidase-like catalytic performance of mesoporous ceria. The generated hydroxyl radicals could damage severely the cell structure of the bacteria and prevent biofilm formation. Moreover, the in vivo experiments demonstrate that the nanoreactor can efficiently eliminate 99.9% of bacteria in the wound tissues and prevent persistent inflammation without damage to normal tissues in mice. This work provides a rational design of a nanoreactor with enhanced catalytic activity, which can covert glucose to hydroxyl radicals and exhibits potential applications in antibacterial therapy.

Ru complex and N, P-containing polymers confined within mesoporous hollow carbon spheres for hydrogenation of CO2 to formate

Ru complex and N, P-containing polymers confined within mesoporous hollow carbon spheres for hydrogenation of CO2 to formate

Hollow Mesoporous Silica by Ion Exchange-Induced Etching Strategy for High Temperature Proton Exchange Membrane

Hollow mesoporous silica (HMS) has attracted significant attention for fuel cell applications. The mesopores in the shell can accelerate proton transport and the void in the center of the particle is advantageous for proton storage. However, the conventional methods for HMS fabrication are complicated, which is not conducive to scaling up the fabrication of HMS. In this work, a new, simple strategy to synthesize HMS has been developed via OH− ion exchange-induced etching of mesoporous silica (mSiO2). The mSiO2 immersed in an alkaline Na2CO3 solution led to an exchange of the Br− ions in the surfactant with the OH− ions in the solution, resulting in a high concentration of OH− ions in the mesoporous channels of mSiO2 close to the core, and a low concentration of OH− ions close to the surface. This demonstrated that the etching of the core of mSiO2 was induced, which extended from the core to the surface of the nanoparticles. Furthermore, the success of the ion exchange-induced etching process was demonstrated by the gradient distribution of the Na+ ion in mesoporous silica microspheres through microscopy. In addition, the proton conductivity of the phosphoric acid-impregnated HMS membrane at 180°C under anhydrous conditions was found to be 0.025 S.cm−1. These results demonstrate the simplicity of the ion exchange-induced etching strategy for the fabrication of HMS microspheres and its promising application in high temperature proton exchange membrane fuel cells.

Self-healing effect of epoxy coating containing mesoporous polyaniline hollow spheres loaded with benzotriazole

Recently, people pay more attention to the application of mesoporous nanomaterials in organic coatings owing to their high corrosion inhibitor loading rate, which could strongly improve organic coatings anticorrosion performance. However, traditional nanomaterials were used only as the hosts for corrosion inhibitors because they do not have corrosion inhibition function, which restricted the further improvement of the anticorrosion performance of organic coatings. If the mesoporous materials have corrosion inhibition function, it will be inferred to further improve the coating performance.To address this problem, a novel mesoporous nanomaterial: mesoporous polyaniline hollow spheres (MPHS) were synthesized using mesoporous carbon hollow spheres (MCHS) as the hard template and PS100-b-PEO114 as the soft template. MPHS loaded with benzotriazole (MPHS@BTA) was introduced into epoxy coating as an anticorrosion pigment, and then the anticorrosion properties of epoxy coatings were systematically investigated.The BET surface area, total pore volume and average pore diameter of MPHS were 568 cm2 g−1, 1.3 cm3 g−1 and 8.9 nm, respectively. Due to high specific area and high pore volume, the loading rate of BTA in MPHS was up to 27 wt%. Epoxy coating blended with 2 wt% MPHS@BTA presented the best anticorrosion and self-healing properties, which was ascribed to the synergistic effect of the passivation function of PANI and the corrosion inhibition effect of BTA.

Synthesis of Mesoporous CuO Hollow Sphere Nanozyme for Paper-Based Hydrogen Peroxide Sensor.

Point-of-care monitoring of hydrogen peroxide is important due to its wide usage in biomedicine, the household and industry. Herein, a paper sensor is developed for sensitive, visual and selective detection of H2O2 using a mesoporous metal oxide hollow sphere as a nanozyme. The mesoporous CuO hollow sphere is synthesized by direct decomposition of copper–polyphenol colloidal spheres. The obtained mesoporous CuO hollow sphere shows a large specific surface area (58.77 m2/g), pore volume (0.56 cm3/g), accessible mesopores (5.8 nm), a hollow structure and a uniform diameter (~100 nm). Furthermore, they are proven to show excellent peroxidase-like activities with Km and Vmax values of 120 mM and 1.396 × 10−5 M·s−1, respectively. Such mesoporous CuO hollow spheres are then loaded on the low-cost and disposable filter paper test strip. The obtained paper sensor can be effectively used for detection of H2O2 in the range of 2.4–150 μM. This work provides a new kind of paper sensor fabricated from a mesoporous metal oxide hollow sphere nanozyme. These sensors could be potentially used in bioanalysis, food security and environmental protection.

Combination of Selective Etching and Impregnation toward Hollow Mesoporous Bioactive Glass Nanoparticles.

In this study, binary SiO2-CaO hollow mesoporous bioactive glass nanoparticles (HMBGNs) are prepared by combing selective etching and impregnation strategies. Spherical silica particles (SiO2 NPs) are used as hard cores to assemble cetyltrimethylammonium bromide (CTAB)/silica shells, which are later removed by selective etching to generate a hollow structure. After the removal of CTAB by calcination, the mesoporous shell of particles is formed. Calcium (Ca) is incorporated into the particles using impregnation by soaking the etched SiO2 NPs in calcium nitrate aqueous solution. The amount of incorporated Ca is tailorable by controlling the ratio of SiO2 NPs:calcium nitrate in the soaking solution. The produced HMBGNs are bioactive, as indicated by the rapid formation of hydroxyapatite on their surfaces after immersion in simulated body fluid. In a direct culture with MC3T3-E1 cells, HMBGNs were shown to exhibit concentration-dependent cytotoxicity and can stimulate osteogenic differentiation of MC3T3-E1 cells at concentrations of 1, 0.5, and 0.25 mg/mL. Our results indicate that the combination of selective etching and impregnation is a feasible approach to produce hierarchical HMBGNs. The produced hollow particles have potential in drug delivery and bone tissue regeneration applications, and should be further investigated in detailed in vitro and in vivo studies.

Hierarchical mesoporous hollow Ce-MOF nanosphere as oxidase mimic for highly sensitive colorimetric detection of ascorbic acid

In this work, we firstly developed a new method for the synthesis of hierarchical mesoporous hollow Ce-MOF nanosphere templated by diblock copolymer. The hierarchical hollow mesoporous Ce-MOF nanosphere as the oxidase mimic shows highly catalytic chromogenic activity toward 3,3,5,5-tetramethylbenzidine (TMB) without the presence of H2O2, and it can be used as a substitute for peroxidase mimics and H2O2 system in the colorimetric reaction. Herein, we provide a new highly sensitive and selective colorimetric method for the detection of Ascorbic acid (AA). At the optimal pH (3.5), temperature (the room temperature), time (5 min) and TMB concentration (280 μM), the limit of detection (LOD) was 0.03 µM, the range of the detection was 8 to 56 µM.

A Comprehensive Study of Drug Loading in Hollow Mesoporous Silica Nanoparticles: Impacting Factors and Loading Efficiency.

Although hollow mesoporous silica nanoparticles (HMSNs) have been intensively studied as nanocarriers, selecting the right HMSNs for specific drugs still remains challenging due to the enormous diversity in so far reported HMSNs and drugs. To this end, we herein made a comprehensive study on drug loading in HMSNs from the viewpoint of impacting factors and loading efficiency. Specifically, two types of HMSNs with negative and positive zeta potential were delicately constructed, and three categories of drugs were selected as delivery targets: highly hydrophobic and lipophobic (oily), hydrophobic, and hydrophilic. The results indicated that (i) oily drugs could be efficiently loaded into both of the two HMSNs, (ii) HMSNs were not good carriers for hydrophobic drugs, especially for planar drugs, (iii) HMSNs had high loading efficiency towards oppositely charged hydrophilic drugs, i.e., negatively charged HMSNs for cationic molecules and vice versa, (iv) entrapped drugs would alter zeta potential of drug-loaded HMSNs. This work may provide general guidelines about designing high-payload HMSNs by reference to the physicochemical property of drugs.

Hollow-Shell-Structured Mesoporous Silica-Supported Palladium Catalyst for an Efficient Suzuki-Miyaura Cross-Coupling Reaction

The construction of a high stability heterogeneous catalyst for privileged common catalysis is a benefit in regard to reuse and separation. Herein, a palladium diphenylphosphine-based hollow-shell-structured mesoporous catalyst (HS@PdPPh2@MSN) was prepared by immobilizing bis((diphenylphosphino)ethyltriethoxysilane)palladium acetate onto the inner wall of a mesoporous organicsilicane hollow shell, whose surface was protected by a –Si(Me)3 group. Electron microscopies confirmed its hollow-shell-structure, and structural analyses and characterizations revealed its well-defined single-site active species within the silicate network. As presented in this study, the newly constructed HS@PdPPh2@MSN enabled an efficient Suzuki-Miyaura cross-coupling reaction for varieties of substrates with up to 95% yield in mild conditions. Meanwhile, it could be reused at least five times with good activity, indicating its excellent stability and recyclability. Furthermore, the cost-effective and easily synthesized HS@PdPPh2@MSN made it a good candidate for employment in fine chemical engineering.

Biotemplated Hollow Mesoporous Silica Particles as Efficient Carriers for Drug Delivery.

We designed three types of hollow-shaped porous silica materials via a three-step biotemplate-directed method: porous hollow silica nanorods, hollow dendritic fibrous nanostructured silica (DFNS), and ultraporous sponge-like DFNS. The first step was making a biotemplate, for which we used cellulose nanocrystals (CNCs), consisting of rod-shaped nanoparticles synthesized by conventional acid hydrolysis of cellulose fibers. In a second step, core-shell samples were prepared using CNC particles as hard template by two procedures. In the first one, core-shell CNC-silica nanoparticles were synthesized by a polycondensation reaction, which exclusively took place at the surface of the CNCs. In the second procedure, a typical synthesis of DFNS was conducted in a bicontinuous microemulsion with the assistance of additives. DFNS was assembled on the surface of the CNCs, giving rise to core-shell CNC-DFNS structures. Finally, all of the silica-coated CNC composites were calcined, during which the CNC was removed from the core and hollow structures were formed. These materials are very lightweight and highly porous. All three structures were tested as nanocarriers for drug delivery and absorbents for dye removal applications. Dye removal results showed that they can adsorb methylene blue efficiently, with ultraporous sponge-like DFNS showing the highest adsorption capacity, followed by hollow DFNS and hollow silica nanorods. Furthermore, breast cancer cells show a lower cell viability when exposed to doxorubicin-loaded hollow silica nanorods compared with control or doxorubicin cultures, suggesting that the loaded nanorod has a greater anticancer effect than free doxorubicin.

Construction of remarkable electromagnetic wave absorber from heterogeneous structure of Co-CoFe2O4@mesoporous hollow carbon spheres

• Controlling the load of Co-CoFe 2 O 4 can receive exceptional impedance matching. • The minimum reflection loss is −65.31 dB at 2.1 mm. • The maximum effective absorption bandwidth is 8.48 GHz at 2.4 mm. Carbon nanomaterials have attracted a great deal of attention in various fields especially in electromagnetic wave absorption due to unique physical and chemical properties. Herein, a novel Co-CoFe 2 O 4 @mesoporous hollow carbon spheres (PCHMs) nanocomposites were prepared by two-facile steps, which included synthesizing three-dimensional mesoporous hollow carbon nanospheres (3D PCHMs) by hard template method, pyrolysis and etching process and in-situ growth of ultra-small Co-CoFe 2 O 4 nanoparticles on PCHMs. The microscopic morphology and electromagnetic wave absorption mechanisms were discussed in depth. The synthesized Co-CoFe 2 O 4 @PCHMs maintained a stable hollow and mesoporous structure and the Co-CoFe 2 O 4 nanoparticles are uniformly distributed on the PCHMs. The complex permittivity and complex permeability could be effortlessly controlled by the content of Co-CoFe 2 O 4 nanoparticles. Benefitting from the remarkable impedance matching under the influence of moderate complex permittivity and complex permeability, the minimum reflection loss ( RL min ) of S2 exhibited −65.31 dB at 2.1 mm. The maximum effective absorption bandwidth (EAB) reached up to 8.48 GHz. The Co-CoFe 2 O 4 @PCHMs nanocomposites will have great potential application in electromagnetic wave absorption.

Antisolvent Route to Ultrathin Hollow Spheres of Cerium Oxide for Enhanced CO Oxidation.

Cerium(IV) oxide (CeO2), or ceria, is one of the most abundant rare-earth materials that has been extensively investigated for its catalytic properties over the past two decades. However, due to the global scarcity and increasing cost of rare-earth materials, efficient utilization of this class of materials poses a challenging issue for the materials research community. Thus, this work is directed toward an exploration of making ultrathin hollow ceria or other rare-earth metal oxides and mixed rare-earth oxides in general. Such a hollow morphology appears to be attractive, especially when the thickness is trimmed to its limit, so that it can be viewed as a two-dimensional sheet of organized nanoscale crystallites, while remaining three-dimensional spatially. This ensures that both inner and outer shell surfaces can be better utilized in catalytic reactions if the polycrystalline sphere is further endowed with mesoporosity. Herein, we have devised our novel synthetic protocol for making ultrathin mesoporous hollow spheres of ceria or other desired rare-earth oxides with a tunable shell thickness in the region of 10 to 40 nm. Our ceria ultrathin hollow spheres are catalytically active and outperform other reported similar nanostructured ceria for the oxidation reaction of carbon monoxide in terms of fuller utilization of cerium. The versatility of this approach has also been extended to fabricating singular or multicomponent rare-earth metal oxides with the same ultrathin hollow morphology and structural uniformity. Therefore, this approach holds good promise for better utilization of rare-earth metal elements across their various technological applications, not ignoring nano-safety considerations.

Hollow Mesoporous Nanoreactors with Encaged PtSn Alloy Nanoparticles for Selective Hydrogenation of Furfural to Furfuryl Alcohol

Hollow mesoporous nanoreactors with encaged functional nanoparticles are promising heterogeneous catalysts due to the advantages related to their hollow cavities. In this study, we employ metal ion...

Advanced Asymmetric Supercapacitor Based on Graphene/Single-Walled Carbon Nanotube and Mesoporous Hollow NiCo2S4 Sub-microsphere Electrodes with High Energy Density

Supercapacitors (SCs) are drawing considerable attention because of their remarkable power density, long cycling stability, quick charging/discharging, and environmentally friendly characteristics. They are currently applied in electronic devices and wearable energy storage systems. Recently, the use of asymmetric supercapacitors (ASCs) has been acknowledged as a valid strategy to improve energy density of SCs due to the combination of electric double-layered anodes and redox-schemed cathodes. Here, mesoporous hollow NiCo2S4 sub-microspheres and porous graphene/single-walled carbon nanotubes are synthesized by a simple and elegant method without any use of templates. The as-synthesized products exhibit improved capacitive performance and extraordinary stability. An assembled asymmetric supercapacitor with graphene/single-walled carbon nanotubes and NiCo2S4 as its negative and positive electrodes, respectively, delivers a maximum energy density of 45.3 W h kg−1 (at 800 W kg−1) and an outstanding cycling life (87.5% over 20,000 cycles). This suggests that the obtained products possess huge potential to become the next generation of electrode materials for future energy storage devices.

Ultrafine RhNi Nanocatalysts Confined in Hollow Mesoporous Carbons for a Highly Efficient Hydrogen Production from Ammonia Borane.

Ammonia borane (AB) has received growing research interest as one of the most promising hydrogen-storage carrier materials. However, fast dehydrogenation of AB is still limited by sluggish catalytic kinetics over current catalysts. Herein, highly uniform and ultrafine bimetallic RhNi alloy nanoclusters encapsulated within nitrogen-functionalized hollow mesoporous carbons (defined as RhNi@NHMCs) are developed as highly active, durable, and selective nanocatalysts for fast hydrolysis of AB under mild conditions. Remarkable activity with a high turnover frequency (TOF) of 1294 molH2 molRh-1 min-1 and low activation energy (Ea) of 18.6 kJ mol-1 is observed at room temperature, surpassing the previous Rh-based catalysts. The detailed mechanism studies reveal that when catalyzed by RhNi@NHMCs, a covalently stable O-H bond by H2O first cleaves in electropositive H* and further attacks B-H bond of AB to stoichiometrically produce 3 equiv of H2, whose catalytic kinetics is restricted by the oxidation cleavage of the O-H bond. Compositional and structural features of RhNi@NHMCs result in synergic electronic, functional, and support add-in advantages, kinetically accelerating the cleavage of the attacked H2O (O-H bond) and remarkably promoting the catalytic hydrolysis of AB accordingly. This present work represents a new and effective strategy for exploring high-performance supported metal-based alloy nanoclusters for (electro)catalysis.

Rational construction of well-defined hollow double shell SnO2/mesoporous carbon spheres heterostructure for supercapacitors

The selection of proper electrode materials and the design of rational structure are two efficient approaches to improve the electrochemical performance of supercapacitors. Carbonaceous materials have become an important choice of electrode materials due to their good electrical conductivity and accommodation for volume expansion of metal oxides. In this contribution, hollow double-shell structured H-SnO2/MesCHS (mesoporous carbon hollow spheres) heterostructure is successfully achieved by silica template and in-situ polymerization methods. The H-SnO2/MesCHS composites demonstrate a specific surface area of 747.7 m2 g-1 and an average pore size of ca. 4.9 nm in the mesoporous carbon shell, where the outer layer of mesoporous hollow carbon layer act as a buffer to confine the volume expansion of the inner hollow tin oxide sphere. As consequence, hollow double-shell H-SnO2/MesCHS heterostructure demonstrates an excellent electrochemical performance with a high specific capacitance of 470 F g-1, exceptional cycling stability (88.4% retention of capacitance over 4000 cycles) and outstanding coulombic efficiency of 86.5% at high current density of 20 A g−1. The work provides an alternative route for the preparation of spherical hollow heterostructures materials with tunable double shell architectures, which may potentially be used as electrode materials for high-performance of energy storage.

Absorbent cotton derived mesoporous CeO2 hollow tubule for enhanced detection of p-xylene at low energy consumption

Ultra-sensitive detection of flammable and carcinogenic p-xylene gas at relatively low energy consumption through metal oxide-based sensors remains a great challenge due to its high stability. Herein, mesoporous CeO2 hollow microtubules with cubic fluorite structure were simply prepared by immersing absorbent cotton into cerium salt and subsequent calcination. The effect of calcination temperature on the microstructure and gas-sensing performance was also studied. The CeO2-500 hierarchical structure calcinated at 500 °C is composed of cross-linked nanoparticles with small size (12 nm), which possesses relatively large specific surface area (60.8 m2·g−1), well-distributed mesopores (15.0 nm) and abundant oxygen vacancy defects. At a relatively low operating temperature of 133 °C, CeO2-500 sensor shows a fast response to 100 ppm p-xylene (Tres = 5.4 s) and detection limit of 100 ppb, which represents the lowest value in reported CeO2-based sensors. Such excellent gas-sensing performance is highly related to the intrinsic structural properties of mesoporous CeO2-500 hollow microtubule, surface adsorbed oxygen and oxygen vacancy defects caused by Ce3+ ions.

Pt Single Atoms Supported on N-Doped Mesoporous Hollow Carbon Spheres with Enhanced Electrocatalytic H2 -Evolution Activity.

The electronic metal-support interaction (EMSI) plays a crucial role in catalysis as it can induce electron transfer between metal and support, modulate the electronic state of the supported metal, and optimize the reduction of intermediate species. In this work, the tailoring of electronic structure of Pt single atoms supported on N-doped mesoporous hollow carbon spheres (Pt1 /NMHCS) via strong EMSI engineering is reported. The Pt1 /NMHCS composite is much more active and stable than the nanoparticle (PtNP ) counterpart and commercial 20wt% Pt/C for catalyzing the electrocatalytic hydrogen evolution reaction (HER), exhibiting a low overpotential of 40mV at a current density of 10mA cm-2 , a high mass activity of 2.07 A mg-1 Pt at 50mV overpotential, a large turnover frequency of 20.18 s-1 at 300mV overpotential, and outstanding durability in acidic electrolyte. Detailed spectroscopic characterizations and theoretical simulations reveal that the strong EMSI effect in a unique N1 -Pt1 -C2 coordination structure significantly tailors the electronic structure of Pt 5d states, resulting in promoted reduction of adsorbed proton, facilitated H-H coupling, and thus Pt-like HER activity. This work provides a constructive route for precisely designing single-Pt-atom-based robust electrocatalysts with high HER activity and durability.

A versatile ligand-assisted cooperative template method to synthesize multi-shelled mesoporous hollow metal hydroxide and oxide nanospheres as catalytic reactors

Nowadays, multi-shelled mesoporous hollow metal oxide nanospheres have drawn a lot of attention due to their large internal space, nanometer scaled shell thickness, high specific surface area and well-defined mesopores, of which unique nanostructure endows metallic oxides with enhanced properties. In this thesis, we have studied and proposed a versatile ligand-assisted cooperative template method to synthesize multi-shelled mesoporous hollow metal hydroxides and oxides nanospheres, in which silica nanospheres act as sacrificial templates and the coordination interaction between metal ions and surfactant can be cooperatively amplified by using chelating ligand (ascorbic acid) as a co-template. The synthesized metal hydroxides and oxides nanospheres possess stable hollow structure, uniform spherical morphology and tunable diameter from 270 to 690 nm. All the multi-shelled mesoporous hollow metal hydroxide and metal oxide nanospheres exhibit high surface areas (up to 640 m2/g). The obtained Au nanoparticles loaded composited nanospheres exhibit excellent reactivity for solvent-free aerobic oxidation of ethylbenzene with high activity (28.2%) and selectivity (87%).