Hierarchical Hollow Microspheres Research Articles

Fabrication of immobilized lipases from Candida rugosa on hierarchical mesoporous silica for enzymatic enrichment of ω-3 polyunsaturated fatty acids by selective hydrolysis

In this study, lipase from Candida rugosa was immobilized on hydrophobic hierarchical porous hollow silica microsphere (HPHSM-C3) via adsorption. The prepared biocatalyst HPHSM-C3@CRL exhibited higher activity, thermal and pH stability. HPHSM-C3@CRL remained 70.2% of initial activity after 30 days of storage at 24 °C and 50.4% of initial activity after 10 cycles. Moreover, HPHSM-C3@CRL was utilized in enzymatic enrichment of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) in glycerides, achieving ω-3 PUFAs content of 53.42% with the hydrolysis rate of 48.78% under optimal condition. The Km and Vmax value of HPHSM-C3@CRL was 42.2% lower and 63.5% higher than those of CRL, respectively. The 3D structure analysis of CRL, substrates and pore structure of HPHSM-C3 suggested that the hierarchical pore improved activity and selectivity of immobilized lipase. This result demonstrated that HPHSM-C3@CRL may be an effective biocatalyst for the enzymatic enrichment of ω-3 PUFAs in food industries.

Hierarchical porous hollow carbon microsphere/carbon nanotube heterostructures for high-performance supercapacitor

Constructing carbon nanotube (CNT)-based electrode materials is an effective strategy for the development of supercapacitors with high-rate capability. In this work, hierarchical porous hollow carbon microsphere (HCM)/CNT heterostructures were prepared by calcination of 3-aminophenol formaldehyde resin microspheres (AFSs) with the assistance of ethanolamine and Ni salts. This approach, which ingeniously combines the template and CVD methods, not only generates both HCMs and CNTs, but also achieves the growth of CNTs on HCMs. The length and dispersion of CNTs as well as the porous structure of HCMs could be easily controlled by adjusting the amount of ethanolamine and the size of AFS. Combining the advantages of the fascinating structure, i.e., abundant micro-, meso-, and macropores, high electrical conductivity, and good wettability induced by the presence of high-level N atoms, the optimal sample exhibited superior electrochemical performance, such as a high specific capacitance of 234.9 F g−1 at 2 A g−1, excellent cycling stability with the capacitance retention of 93.9 % after 10,000 cycles. More importantly, it possessed outstanding rate capability because its capacitance remained almost constant as the current density was increased above 5 A g−1. This research sheds light on an avenue to construct CNT-based carbon heterostructures for efficient energy storage.

Hyperactivation of lipase by oil-water interface in interfacial immobilization on hierarchical porous hollow silica microsphere: dynamics, mechanism and application

Lipases exhibit high activity at oil−water interfaces due to interfacial activation effect. In this work, the interfacial immobilization of lipase was developed based on Pickering emulsion through using lipase solution as the aqueous phase, n-hexane as oil phase, and stabilized by modified hierarchical porous hollow silica microsphere (HPHSM-C1). The prepared immobilized lipase HPHSM-C1@AY400-II achieved highest specific activity (6.4 IU/mg) with the amount of immobilized protein of 34.5 mg/g, surpassing traditional adsorptive immobilized lipase (HPHSM-C1@AY400) by 1.89-fold, and retained 70 % of residual activity after ten operational cycles. The conformational change of HPHSM-C1@AY400-II was confirmed by Fourier transform infrared. The interfacial adsorption at oil-water interface was influenced by intraparticle and surface diffusion, as evidenced by adsorption kinetic. Finally, the HPHSM-C1@AY400-II was applied in enzymatic enrichment of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) in glycerides, and the content of ω-3 PUFAs in the glyceride significantly increased from 32.35 % to 54.78 % after 3 h of selective hydrolysis. This study opens a promising avenue to improve lipase activity in immobilization process, contributing to enzymatic synthesis of functional lipids.

Reinforced electrochemical energy storage through controlled construction of hierarchical hollow β-Ni(OH)2 microspheres enriched with oxygen vacancies induced by functionalized MWCNTs

As promising electrode materials, hollow-structured metallic oxides/hydroxides have attracted extensive attention for their significantly enhanced catalyst and electrochemical performances. In practice, however, it is still challenging to construct well-dispersed hollow structures using facile and versatile template-free methods. And, as a result of the weak conductivity of most metallic oxides/hydroxides, it is a particularly effective means to integrate metallic oxides/hydroxides with carbon-based conductive substrates or introduce oxygen vacancies for further promoting reaction kinetics and achieving boosted electrochemical performance. Herein, a novel composite material consisting of oxygen-rich vacancy β-Ni(OH)2 coupled with oxidized multi-wall carbon nanotubes (Ov-Nβ/Cm) was synthesized using a one-step hydrothermal technique without the need for templates. The hierarchical hollow microsphere structure was achieved by utilizing oxidized multi-wall carbon nanotubes (MWCNTs) as an alternative to conventional surfactants or templates. The uniform distribution of multistage pores in the newly designed Ov-Nβ/Cm composite facilitates the transportation of electrolyte ions, thereby endowing it with outstanding electrochemical performance. A straightforward technique for producing high-quality Ni(OH)2-based electrode materials is presented in this investigation, along with fresh perspectives on the formation mechanism of hollow-structured composites. Developing MWCNT-based hollow nanostructured composites with oxygen vacancies-enriched will offer an essential novel avenue to exploit excellent electrode materials for supercapacitors and other energy storage systems.

Homologous Heterostructured NiS/NiS2 @C Hollow Ultrathin Microspheres with Interfacial Electron Redistribution for High-Performance Sodium Storage.

Nickel sulfides with high theoretical capacity are considered as promising anode materials for sodium-ion batteries (SIBs); however, their intrinsic poor electric conductivity, large volume change during charging/discharging, and easy sulfur dissolution result in inferior electrochemical performance for sodium storage. Herein, a hierarchical hollow microsphere is assembled from heterostructured NiS/NiS2 nanoparticles confined by in situ carbon layer (H-NiS/NiS2 @C) via regulating the sulfidation temperature of the precursor Ni-MOFs. The morphology of ultrathin hollow spherical shells and confinement of in situ carbon layer to active materials provide rich channels for ion/electron transfer and alleviate the effects of volume change and agglomeration of the material. Consequently, the as-prepared H-NiS/NiS2 @C exhibit superb electrochemical properties, satisfactory initial specific capacity of 953.0mA h g-1 at 0.1 A g-1 , excellent rate capability of 509.9mA h g-1 at 2 A g-1 , and superior longtime cycling life with 433.4mA h g-1 after 4500 cycles at 10 A g-1 . Density functional theory calculation shows that heterogenous interfaces with electron redistribution lead to charge transfer from NiS to NiS2 , and thus favor interfacial electron transport and reduce ion-diffusion barrier. This work provides an innovative idea for the synthesis of homologous heterostructures for high-efficiency SIB electrode materials.

Enhanced H2S Gas Sensing Properties of the Hierarchical CuO Hollow Microspheres

In present work, the hierarchical CuO hollow microspheres were synthesized through a facile hydrothermal method. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results show that the hierarchical CuO hollow microspheres with uniform size of 3 μm are self-assembled by hundreds of primary nanorods with diameters of about 20 nm. The wall thickness of the hollow microspheres is about 200 nm. The hierarchical CuO hollow microspheres exhibit good sensing performance in H2S detection. The optimal operating temperature is 180 °C. And, in a large range, the hierarchical CuO hollow microspheres display excellent linear sensing performance in ethanol detection. The detecting limit is lower to 1 ppm. Furthermore, the hierarchical CuO hollow microspheres demonstrate excellent selectivity in H2S detection. The sensing mechanism also has been discussed. It can be expected that the novel morphology of the hierarchical CuO hollow microspheres may bring amazing development for H2S detection.

Combinatorial Structural Engineering of Multichannel Hierarchical Hollow Microspheres Assembled from Centripetal Fe/C Nanosheets to Achieve Effective Integration of Sound Absorption and Microwave Absorption.

Electromagnetic radiation and noise pollution are two of the four major environmental pollution sources. Although various materials with excellent microwave absorption performances or sound absorption properties have been manufactured, it is still a great challenge to design materials with both microwave absorption and sound absorption abilities due to different energy consumption mechanisms. Herein, a combination strategy based on structural engineering was proposed to develop bi-functional hierarchical Fe/C hollow microspheres composed of centripetal Fe/C nanosheets. Both of the interconnected channels created by multiple gaps among the adjacent Fe/C nanosheets and the hollow structure have positive effects on the absorbing performances by promoting the penetration of microwaves and acoustic waves and prolonging action time between microwave energy and acoustic energy with materials. In addition, a polymer-protection strategy and a high-temperature reduction process were applied to keep this unique morphology and further improve the performances of the composite. As a result, the optimized hierarchical Fe/C-500 hollow composite exhibits a wide effective absorption bandwidth of 7.52 GHz (10.48-18.00 GHz) at only 1.75 mm. Furthermore, the Fe/C-500 composite can effectively absorb sound wave in the frequency of 1209-3307 Hz, basically including part of the low frequency range (<2000 Hz) and most of the medium frequency range (2000-3500 Hz), and has 90% absorption of sound at 1721-1962 Hz. This work puts new insight into the engineering and development of microwave absorption-sound absorption-integrated functional materials with promising applications.

Exploring novel p-n core/shell structure in single α-Fe2O3 nanorods of hierarchical hollow microspheres for ultrasensitive acetone gas sensor

Fabricating metal oxide sensors with super-sensitivity and good distinguishing properties for gases is a challenge due to the difficulties in controlling vacancy-type structural defects of nanomaterials and the data processing. In this paper, we reported the fabrication of hierarchical α-Fe2O3 hollow microsphere (HFHM)-based sensor using a facile and scalable method with uniform-micro spherical carbon templates, as well as the data analysis using artificial intelligence (AI). The shell of the unique hollow microspheres was built by connecting many α-Fe2O3 nanorods, so the superstructures have 0D, 1D, and 3D structural features. In these α-Fe2O3 nanorods, positron annihilation measurements revealed abundant oxygen-vacancy clusters (11 atoms), nanopores (0.53 nm) and p-n core/shell structure. The HFHM-based sensors, hence, exhibited an extremely high sensitivity toward acetone (Response = 320 (200 ppm), limited detection (DL) ∼ 250 ppt) and ethanol (Response = 300 (200 ppm), DL ∼ 500 ppt), as well as a super-fast response time (1–2 s). In particular, by using the Principal Component Analysis (PCA), an applied AI tool, we were able to significantly improve the distinguishing and selective abilities of acetone and ethanol (high-response gas groups) as well as H2, CO and NH3 (low-response gas groups).

In situ N-doped carbon nanotubes modified NiS2 hierarchical hollow microspheres for boosting sodium storage performance

Engineering novel electrode materials with distinctive architectures has a significant influence on tuning the structural/electrochemical properties for boosting the sodium storage performance. Herein, starting from metal-organic framework (MOF), we report an in situ catalytic method with chemical transformation strategy to fabricate NiS2 hierarchical hollow microspheres (HMs) with continuous N-doped carbon nanotubes (NCNTs) networks (NiS2@NCNTs HMs). Benefitting from the hierarchical hollow structure and three-dimensional (3D) NCNTs networks as well as the robust structural stability, the prepared NiS2@NCNTs HMs indicates excellent Na+ storage performance. More specifically, the composite shows a high reversible capacity of 626.6 mA h g−1 at 0.2 A g−1 for Na+ storage and retains 333.3 mA h g−1 at 5.0 A g−1, remarkably higher than those of the previously reported NiS2-based anode materials. In particular, it maintains a stable reversible capacity of 343.0 mA h g−1 even at 3.0 A g−1 over 3000 cycles. The in situ catalytic NCNTs on MOF precursors strategy for hierarchical structural composites can be extended to other novel electrodes for high performance energy storage devices.

Hierarchical MoS2 hollow microspheres with high piezoelectric catalytic performance prepared by the soft-template method

Hierarchical MoS2 hollow microspheres with high piezoelectric catalytic performance prepared by the soft-template method

Hierarchical dandelion-like CoS2 hollow microspheres: self-assembly and controllable microwave absorption performance.

The emerging electromagnetic radiation and interference problems have promoted the rapid development of microwave absorption materials (MAMs). However, it remains a severe challenge to construct high-performance microwave absorption materials with broadband, lightweight and corrosion resistance within low filling contents. Herein, hierarchical dandelion-like CoS2 hollow microspheres were reasonably constructed via a solvothermal-hydrothermal etching-in situ vulcanization process. The structure morphology, composition and electromagnetic performance of all samples have been thoroughly tested. The research results demonstrated that the structure morphology of the prepared samples with a volume ratio of 1 : 1 between ethanol and H2O remained intact without serious damage. Notably, the as-obtained hierarchical dandelion-like CoS2 hollow microspheres (25 wt%) exhibited excellent microwave absorption capacity with a minimum reflection loss (RLmin) of -47.3 dB and the corresponding effective absorption bandwidth (EAB) of 8.4 GHz at 3.3 mm. Moreover, the broadest effective absorption bandwidth (EAB, RL < -10 dB) reached 9.0 GHz (9.0-18.0 GHz) at the matching thickness of 3.2 mm. The unparalleled multiple features including hierarchical hollow structure, tunable complex permittivity as well as the enhanced impedance matching endowed CoS2 great promise as high-performance microwave absorbers for solving the problem of electromagnetic pollution.

S-modified NiFe-phosphate hierarchical hollow microspheres for efficient industrial-level seawater electrolysis

For sustained hydrogen generation from seawater electrolysis, an efficient and specialized catalyst must be designed to cope with the slow anode reaction and chloride ions (Cl-) corrosion. In this work, an S-modified NiFe-phosphate with hierarchical and hollow microspheres was grown on the NiFe foam skeleton (S-NiFe-Pi/NFF), acting as a bifunctional catalyst to enable industrial-scale seawater electrolysis. The introduction of S distorted the lattice of NiFe-phosphate and regulated the local electronic environment around Ni/Fe active metal, both of which enhanced the electrocatalytic activity. Additionally, the existence of phosphate groups repelled Cl- on the surface and enhanced corrosion resistance, enabling stable long-term operation in seawater. The double-electrode electrolyzer composed of the hollow-structured S-NiFe-Pi/NFF as both cathode and anode exhibited a potential of 1.68 V at 100 mA cm−2 for seawater electrolysis. Particularly, to achieve industrial requirements of 500 mA cm−2, it only required a low cell voltage of 1.8 V and demonstrated a consistent response over 100 h, which outperformed the pair of Pt/C || IrO2. This study provides a feasible idea for the preparation of electrocatalysts that are with both highly activity and corrosion resistance, which is crucial for the implementation of industrial-scale seawater electrolysis.

Hierarchical hollow monetite microspheres assembled with mesoporous nanosheets: Synthesis and applications in superior adsorbents for lead ions and pH-responsive release drug carrier

Hierarchical hollow monetite microspheres assembled with mesoporous nanosheets were firstly synthesized templating by both large and small micelles of mono-dodecyl phosphate. The obtained hollow monetite microspheres had a diameter of 10 ∼ 30 μm with a specific surface area of 86.76 m2 g−1 and a total pore volume of 0.466 cm3 g−1. The monetite nanosheets which were assembly units of the hollow microspheres possessed many mesopores with a pore size of about 25 nm. The mesoporous hollow monetite microspheres had adsorption capacity of lead ions and vancomycin as high as 1435.6 mg g−1 and 518 mg g−1, respectively. And the vancomycin loaded monetite microspheres exhibited a pH-responsive drug release behavior. The mesoporous hollow monetite microspheres have great potential in contaminants adsorbents and drug carriers.

CuO/WO3 hollow microsphere P-N heterojunction sensor for continuous cycle detection of H2S gas

Hydrogen sulfide (H2S) is an extremely flammable and toxic gas. In this work, we have synthesized WO3 and CuO/WO3 composites for H2S detection using a simple hydrothermal method. The morphology, structure, chemical composition, and gas-sensitive properties of the samples are comprehensively characterized. The results show that the WO3 structure comprises of hierarchical hollow microspheres self-assembled by nanoparticles, and the CuO/WO3 composite retains the hollow microspherical structure of the pure WO3. Furthermore, the gas sensing performance of the CuO/WO3 sensor is significantly improved compared with that of WO3, with a response value of 1297 for 10 ppm H2S at an optimum operating temperature of 70 ℃, which is nearly 103 times that of WO3 (12.5). It also exhibits a rapid response capability (13 s), lower detection limit (100 ppb), and excellent selectivity. In addition, the sensing mechanism of CuO/WO3 composites for H2S gas detection is analyzed in detail. The improved performance may be related to the morphological structure of the CuO/WO3 material and the formation of p-n heterojunction and CuS intermediates.

MoS2 nanocrystals embedded in hierarchical hollow carbon microspheres for efficient aerobic oxidative desulfurization

Aerobic oxidative desulfurization (AODS) is an emerging sustainable technology for deep desulfurization of petroleum fuels, which requires robust catalysts to boost the efficient aerobic oxidation of thiophenes. Here we report a self-assembly approach to anchor homogeneously dispersed MoS2 nanocrystals into hierarchical hollow carbon microspheres for the efficient AODS of thiophenic sulfides. We show that MoS2 nanocrystals are vertically embedded in carbon nanosheets with highly active edge sites exposed to the surface, which could activate the aerobic oxidation of dibenzothiophene at 100 °C, and achieves a turnover frequency of 7.53 h–1, higher than that of the reported metallic oxide catalysts. Through a combination of experimental research and theoretical calculations, we demonstrate that the Mo edge of MoS2 can effectively activate oxygen and strongly adsorb sulfides, which endows our catalyst with extraordinary performance. Moreover, the close coupling of MoS2 nanocrystals in carbon ensures their chemical stability, so that the catalyst maintains unattenuated activity and unchanged chemical structure over seven repeated uses. This work provides both fundamental and practical insights in the design of efficient and stable nanocrystal-based catalysts.

Molybdenum Oxynitride Atomic Nanoclusters Bonded in Nanosheets of N-Doped Carbon Hierarchical Microspheres for Efficient Sodium Storage

HighlightsMoO2.0N0.5 atomic nanoclusters bonded on nanosheets of N/C hierarchical hollow microsphere are synthesized via a facile self- templating strategy.Introduction of MoO2.0N0.5 atomic nanoclusters benefits the enhancement of electrochemical kinetic.Composite of MoO2.0N0.5/NC shows excellent electrochemical performance as an anode material for sodium-ion batteries.

Hierarchical polymeric hollow microspheres with size tunable single holes and their application as catalytic microreactor

Hierarchical polymeric hollow microspheres with size tunable single holes and their application as catalytic microreactor

Sn2+ reduction to synthesis of the Mo doped hollow hierarchical Bi/BiOBr microspheres for efficient ciprofloxacin degradation under visible light

In this study, the Mo-doped hollow hierarchical Bi/BiOBr microspheres are prepared by the solvothermal method with the Sn2+ as reductant. The prepared composites show a good degradation effect for ciprofloxacin (CIP) under visible light. Especially, the BSM-22 composite show the best photocatalytic activity, with the apparent rate constant k as high as 0.03014 min−1, which is 26.9 times that of the pure BiOBr. It is assumed that the introduction of Sn2+ facilitate the formation of hollow hierarchical microspheres structure of BiOBr microspheres and the appearance of metallic Bi on the surfaces. Therefore, the transfer and separation efficiency of photogenerated charges is increased in the composites. Impressive, benefit from the microtopography of the hollow structure, the specific surface area of the BSM-22 (53.476 m2/g) is 21.76 times than that of the BiOBr (2.458 m2/g). The doping of Mo reduces the band gap of BiOBr (exactly from 2.61 to 1.96 eV) and broaden the photoabsorption region. Therefore, the photocatalytic activity of the Mo-doped Bi/BiOBr microspheres are heavily improved in dealing with different kinds of antibiotic molecules. More importantly, these results show that the design strategies of heteroatom doping, metal bismuth production, and morphology control of the bismuth oxybromide composite can greatly improve the visible-light catalytic activity.

Bi2MoO6 hierarchical hollow microspheres with remarkable electrochemical performance

Hierarchical hollow architectures have demonstrated a remarkable electrochemical performance. In this contribution, Bi2MoO6 hierarchical hollow microspheres constructed by nanosheets are prepared by a facile hydrothermal method without any post-treatment, and investigated firstly as anode of lithium-ion batteries. The time-dependent experiments show the morphology evolution from solid microspheres to hierarchical hollow microspheres. Compared with the previous reports, the results manifest expectedly a superior lithium storage performance in terms of specific capacity, cycling stability, rate capability, active energy and Li+ diffusion kinetics.

Sorption-enhanced glycerol steam reforming over hierarchical hollow Ni-CaO-Ca12Al14O33 bi-functional catalyst derived from hydrotalcite-like compounds

Hydrogen production with in situ CO2 capture by the sorption-enhanced steam reforming (SESR) technology is a promising concept to reduce anthropogenic CO2 emissions. However, its practical applicability is limited by rapid, sintering-induced cyclic performance decay at high reaction rate and decarbonation temperatures. Here, we design a highly stable bi-functional catalyst with a surface spatial confinement strategy. The bi-functional catalyst has a hierarchical hollow microsphere structure, in which the shell is composed of layered metal oxides. The sintering resistance of Ca and Ni species is found to arise from the surface spatial confinement effect in which the aggregation and migration of Ni and CaO particles are suppressed by the layers. High stability for SESRG reaction with only 35% loss of sorption enhancement effect is observed after 20 cycles of repeated SESEG-decarbonation, during which H2 purity is maintained at 99%. The result shed light on the design of the stable bi-functional catalysts in the SESR reaction.