Hollow Mesoporous Microspheres Research Articles

The tune of shell numbers of multi-shell hollow mesoporous carbon microspheres for enhanced microwave absorption

The morphology of carbon nanomaterials plays significant effect on the complex permittivity and microwave absorption (MA) capability. Elaborate morphology design would bring about efficient MA performance. In this work, we develop a hollow mesoporous carbon microspheres with different shells (from single to quadruple shells) through a facile template method and layer-by-layer etching process. This multi-shell hollow mesoporous carbon microspheres (MS-HMCMs) can be regarded as a complex composite morphology consisting of hollow, mesoporous and yolk-shell structure, which presents the tunable number of shells for optimal impedance matching, multiple interfacial polarization and the extended microwave transmission path from internal spaces. Thus, the MS-HMCMs demonstrates wide effective absorption bandwidth (EAB) of 6.4 GHz and 5.96 GHz at the thicknesses of 2.5 mm and 3.0 mm. Besides, the complex permittivity and MA properties can be effectively tuned via regulating the shell numbers. This MS-HMCMs with controllable shells may be a promising wideband and lightweight microwave absorber.

Design of chlorella-inspired and smart-responsive bio-microspheres and their application in eco-friendly anti-biofouling coatings

Anti-biofouling coating materials have attracted much attention for their diverse functionality and extensive applications in various fields, such as marine facilities, biomedical apparatus, and so on. However, it is still a huge challenge for long-term anti-fouling coatings to improve the durability, safety, sustainability, eco-friendliness, and biodiversity. Herein, a novel biomimetic coating (Bio-OHMP coating) with eco-friendly and anti-biofouling performance was constructed on the basis of chlorella-inspired amino silicone oil (ASO)-core/polydopamine-shell bio-microspheres (Bio-OHMP microspheres). The Bio-OHMP microspheres were successfully fabricated through combining the hard/soft templates with high-stored hydrophobic substance. Similar to chlorella, great substance storage and delivery function were achieved for the Bio-OHMP microspheres, attributing to the larger central cavity structure of hollow mesoporous polydopamine microspheres (HMP microspheres) and the easy acquisition of NIR/Acid/Base smart-responsive self-healing properties of the Bio-OHMP microspheres. Superhydrophobic properties of the Bio-OHMP coating were originated from the hydrophobic and rough micro/nano-structured Bio-OHMP microspheres and nanoparticles. NIR/Acid/Base smart-responsive characteristics and long-termed superhydrophobic self-healing properties of the Bio-OHMP coating were gained due to the multiple-responsive Bio-OHMP microspheres, and the coating was endowed with high-efficient and large-scale healing abilities. Besides, great anti-biofouling abilities to typical biological or organic contaminants and long-period superhydrophobicity under harsh environments of the Bio-OHMP coating were all confirmed. This novel and multifunctional Bio-OHMP coating shows great prospects in anti-fouling, anti-adhesion, or other fields, while the chlorella-inspired Bio-OHMP microspheres have great potentials to be applied to other functionalized materials.

Preparation and properties of mesoporous SiO2/polyimide composite films

AbstractAlthough polyimide films have a low dielectric constant, with the advent of the 5G era, the dielectric properties of the material are required to be further improved. Therein, we prepared controlled hollow mesoporous SiO2 nanomicrospheres by the hard template method to make mesoporous low dielectric polyimide films. The composite membrane exhibits better thermal stability, mechanical properties, and hydrophobicity compared to the pure membrane. Hollow mesoporous SiO2 dispersed in polyimide can reduce the inhomogeneity of charge distribution between molecules and reduce the interaction between polar chemical bonds and aromatic rings, thus improving the dielectric properties of the whole film. The minimum dielectric constant of the composite films was 2.80 when the hollow mesoporous SiO2 was added at 1.0%. These results fully indicate that the addition of hollow mesoporous SiO2 is beneficial to the multifaceted performance of the polyimide films.Highlights Preparation of hollow mesoporous SiO2 microspheres by using different polystyrene microsphere solutions and TEOS ratios. Synthesis of composite films with different contents of hollow mesoporous SiO2 as functional fillers. The effect of hollow mesoporous SiO2 content on the mechanical properties and thermal stability of PI composite films was investigated. Addition of hollow mesoporous SiO2 reduces the dielectric constant of polyimide composite films.

Confined Heterojunction in Hollow-Structured TiO2 and Its Directed Effect in Photodriven Seawater Splitting.

The high salinity of seawater often strongly affects the activity and stability of photocatalysts utilized for photodriven seawater splitting. The current investigation is focused on the photocatalyst H-TiO2/Cu2O, comprised of hydroxyl-enriched hollow mesoporous TiO2 microspheres containing incorporated Cu2O nanoparticles. The design of H-TiO2/Cu2O is based on the hypothesis that the respective hollow and mesoporous structure and hydrophilic surfaces of TiO2 microspheres would stabilize Cu2O nanoparticles in seawater and provide efficient and selective proton adsorption. H-TiO2/Cu2O shows hydrogen production performances of 45.7 mmol/(g·h) in simulated seawater and 17.9 mmol/(g·h) in natural seawater, respectively. An apparent quantum yield (AQY) in hydrogen production of 18.8% in water (and 14.9% in natural seawater) was obtained at 365 nm. Moreover, H-TiO2/Cu2O displays high stability and can maintain more than 90% hydrogen evolution activity in natural seawater for 30 h. A direct mass- and energy- transfer mechanism is proposed to clarify the superior performance of H-TiO2/Cu2O in seawater splitting.

Regulating the kinetics of zinc-ion migration in spinel ZnMn2O4 through iron doping boosted aqueous zinc-ion storage performance

Spinel ZnMn2O4 with a three-dimensional channel structure is one of the important cathode materials for aqueous zinc ions batteries (AZIBs). However, like other manganese-based materials, spinel ZnMn2O4 also has problems such as poor conductivity, slow reaction kinetics and structural instability under long cycles. Herein, ZnMn2O4 mesoporous hollow microspheres with metal ion doping were prepared by a simple spray pyrolysis method and applied to the cathode of aqueous zinc ion battery. Cation doping not only introduces defects, changes the electronic structure of the material, improves its conductivity, structural stability, and reaction kinetics, but also weakens the dissolution of Mn2+. The optimized 0.1 % Fe-doped ZnMn2O4 (0.1% Fe-ZnMn2O4) has a capacity of 186.8 mAh g−1 after 250 charge-discharge cycles at 0.5 A g−1 and the discharge specific capacity reaches 121.5 mAh g−1 after 1200 long cycles at 1.0 A g−1. The theoretical calculation results show that doping causes the change of electronic state structure, accelerates the electron transfer rate, and improves the electrochemical performance and stability of the material.

Microparticles of Sericin-Dextran Conjugate for Improving the Solubility of Antiviral Drug.

A novel sericin-dextran conjugate (SDC) and self-assembled microparticles has been prepared for improving solubility of atazanavir. Microparticles of SDC were assembled by the reprecipitation method. The size and morphology of SDC microparticles could be adjusted by the concentration and solvents. Low concentration was conducive to the preparation of microspheres. Heterogeneous microspheres could be prepared in ethanol with the range of 85-390 nm, and hollow mesoporous microspheres in propanol with an average particle size of 2.5-22 µm. The aqueous solubility of atazanavir was improved to 2.22 mg/mL in buffer solutions at pH 2.0 and 1.65 mg/mL at pH 7.4 by SDC microspheres. In vitro release of atazanavir from hollow microspheres of SDC exhibited a slower release, had the lowest linear cumulative release in basic buffer (pH 8.0), and the most rapid double exponential diphase kinetic cumulative release in acid buffer (pH 2.0).

Construction of hollow mesoporous PPy microsphere nanostructures coated with MnO2 nanosheet as high-performance electrodes for supercapacitors

Construction of hollow mesoporous PPy microsphere nanostructures coated with MnO2 nanosheet as high-performance electrodes for supercapacitors

Snowball flower-like g-C3N4/ZnFe2O4 mesoporous hollow microspheres with enhanced triethylamine sensing properties

Herein, the snowball flower-like g-C3N4/ZnFe2O4 mesoporous hollow microspheres, in which two-dimensional (2D) g-C3N4 nanolayers were loaded onto the surface of ZnFe2O4 hollow microspheres, were constructed by a simple solid phase reaction. The effect of the g-C3N4 concentration on the structure, morphology and gas-sensing performance of the g-C3N4/ZnFe2O4 composites had been explored. On the basis of gas sensitivity test results, the composites owned lower working temperature (160 ℃) and better selectivity toward TEA in comparison with pure ZnFe2O4. Notably, the sensor based on the g-C3N4/ZnFe2O4-15 hollow microspheres (adding 15 ml of g-C3N4 aqueous solution) exhibited outstanding sensing properties, including superior response (18.3) toward 100 ppm TEA at optimum work temperature of 160 ℃, speedy response-recovery time (33, 30 s) and outstanding stability. And the sensor maintained high response of 4.3 to low concentration TEA (5 ppm). The improved gas-sensing performance of the composites could be attributed to the porous ZnFe2O4 hollow microspheres loaded by 2D g-C3N4 nanolayers with large specific surface area and the heterostructure formed between them. Hence, a potential application of the g-C3N4/ZnFe2O4 microspheres might be achieved in detecting TEA at a low optimum work temperature.

Synthesis of Dual-Response MnO2 Nanospheres as Multifunctional Drug Carriers

Recently, hollow structures have attracted much attention due to their high specific surface area, clear interior space, low density and good permeability. Among them, manganese dioxide (MnO2) hollow structure has also been widely studied for catalysis, drug delivery and energy storage. Based on the characteristics of low pH and high GSH concentration in tumor microenvironment, it is possible to develop an intelligent drug delivery system with pH/GSH response based on hollow mesoporous MnO2 nanospheres. In addition, the excellent physical and chemical properties of MnO2 nanomaterials provide conditions for its synergistic photothermal therapy. For example, Mn2+ released after manganese dioxide reacts with GSH can enhance T1-MAGNETIC resonance (MR) imaging. Meanwhile, manganese dioxide can also react with H2O2 in tumor microenvironment to release oxygen and alleviate tumor hypoxia. In order to prevent drug loss during delivery, a GSH-responsive hollow mesoporous manganese dioxide microsphere was selected as the drug carrier in this paper, and a series of studies were carried out on the performance of the carrier. Hollow mesoporous MnO2 nanospheres with particle size below 100 nm were prepared by hydrothermal method, and their response to tumor microenvironment was simulated in vitro. It has been proved that hollow mesoporous MnO2 nanospheres can be desorbed at low pH and GSH response, and can be used to deliver drugs or photothermal agents, as well as for collaborative cancer imaging and treatment.

Hollow Mesoporous Microspheres Coating for Super-Hydrophobicity Wood with High Thermostability and Abrasion Performance.

Super-hydrophobic phenomena generally exist in nature, and wood can also obtain hydrophobicity by specific processing on the surface, being like the construction of microscale rough surface or decoration with low surface energy materials. In this research, the formation of hydrophobic layers on wood surface was investigated without breaking the wood’s original structure. The core-shell structure particles were prepared by penetrating orthosilicate and polystyrene into the hollow mesoporous microsphere structure with tetrahydrofuran. A wood sample was coated with polydimethylsiloxane (PDMS) resin layer to enhance the adhesion of nano and micron hollow mesoporous microsphere on its surface. According to the surface structure of super-hydrophobic subjects in nature, the nano and micron hollow mesoporous microsphere were sprayed with different ratios several times to form a hydrophobic surface. The water contact angle could reach 150°, revealing that the hydrophobic behavior of the nano and micron hollow mesoporous microsphere coating was achieved. The microstructures of wood samples were examined by the scanning electron microscopy, and the chemical functional groups were investigated by the Fourier transform infrared; both verified that the hydrophobic surface was successfully coated. The thermogravimetric examination revealed the improved thermal stability of the hydrophobic wood. The scratch test was used to measure the abrasion resistance of the nano and micron hollow mesoporous microsphere coatings on wood surface. It was suggested that the nano and micron hollow mesoporous microsphere coating was an effective method to fabricate extremely hydrophobic wood products.

Hollow mesoporous CeO2 microspheres for efficient loading of Au single-atoms to catalyze the water-gas shift reaction

Abstract The atomically dispersed catalysts have aroused great attention in the recent decade. However, the preparation of atomically dispersed Au catalysts presents more challenge than other atomically dispersed catalysts such as Pt, Pd, etc. From the aspect of support, this work contributes a novel hollow mesoporous CeO2 microspheres (CeO2-hm) for efficient dispersion of single Au atoms (Au1). Contributed by the high specific surface area and mesoporous structure, CeO2-hm possesses much higher capacity for undertaking Au1, than commercial CeO2 particles (CeO2-c). Typically, with Au loading of 0.2 at%, CeO2-hm supported Au (Au1/CeO2-hm) presents atomic dispersion while CeO2-c supported Au (Au/CeO2-c) contains large amount of Au nanoparticles. Confirmed by catalyzing the water-gas shift (WGS) reaction, the obtained Au1/CeO2 catalysts exhibit notably higher performance than the Au-based catalysts supported by CeO2-c and CeO2 synthesized through co-precipitation and sol-gel strategies. For example, 0.2 at% Au1/CeO2-hm exhibits 9.1 times reactivity of equal Au loaded Au/CeO2-c catalyst. Besides, the CeO2-hm supported single-atom Au catalyst presents good tolerance under long-time WGS running.

Broad-Range Fast Response Vacuum Pressure Sensors Based on a Graphene Nanocomposite with Hollow α-Fe2O3 Microspheres

This paper demonstrates the application of a graphene–ferric oxide (hollow mesoporous α-Fe2O3 microspheres) nanocomposite for the measurement of vacuum pressure. Numerous research and industrial sy...

Facile fabrication of hollow carbon nitride microspheres with mesoporous structures: When ethanol meets cyanamide

A facile method for preparing hollow mesoporous carbon nitride microspheres (HMCNMs) has been developed. A cyanamide/ethanol solution was used as a precursor, with ethanol acting as both a solvent and a porogen, to prepare HMCNMs with a high surface area of 112 m2/g. It was demonstrated that the HMCNM microstructure and surface morphology can be controlled by adjusting the proportion of ethanol in the precursor solution. The resulting HMCNMs exhibited much higher visible light photocatalytic degradative activity toward methylene blue than bulk graphitic carbon nitride.

Aerosol-Assisted Synthesis of Tailor-Made Hollow Mesoporous Silica Microspheres for Controlled Release of Antibacterial and Anticancer Agents.

Hollow mesoporous silica microsphere (HMSM) particles are one of the most promising vehicles for efficient drug delivery owing to their large hollow interior cavity for drug loading and the permeable mesoporous shell for controlled drug release. Here, we report an easily controllable aerosol-based approach to produce HMSM particles by continuous spray-drying of colloidal silica nanoparticles and Eudragit/Triton X100 composite (EUT) nanospheres as templates, followed by template removal. Importantly, the internal structure of the hollow cavity and the external morphology and the porosity of the mesoporous shell can be tuned to a certain extent by adjusting the experimental conditions (i.e., silica to EUT mass ratio and particle size of silica nanoparticles) to optimize the drug loading capacity and the controlled-release properties. Then, the application of aerosol-synthesized HMSM particles in controlled drug delivery was investigated by loading amoxicillin as an antibiotic compound with high entrapment efficiency (up to 46%). Furthermore, to improve the biocompatibility of the amoxicillin-loaded HMSM particles, their surfaces were functionalized with poly(allylamine hydrochloride) and alginate as biocompatible polymers via the layer-by-layer assembly. The resulting particles were evaluated toward Escherichia coli (Gram-negative) bacteria and indicated the bacterial inhibition up to 90% in less than 2 h. Finally, we explored the versatility of HMSMs as drug carriers for pancreatic cancer treatment. Because the pH value of the extracellular medium in pancreatic tumors is lower than that of the healthy tissue, chitosan as a pH-sensitive gatekeeper was grafted to the HMSM surface and then loaded with a pro-apoptotic NCL antagonist agent (N6L) as an anticancer drug. The obtained particles exhibited pH-responsive drug releases and excellent anticancer activities with inhibition of cancer cell growth up to 60%.

Synthesis of hollow mesoporous HAp-Au/MTX and its application in drug delivery

A hollow mesoporous microspheres of hydroxyapatite-Au containing the anticancer agent of methotrexate (hmHAp-Au/MTX) were prepared here. Firstly, biocompatible hydroxyapatite nanoparticles (NPs) with a hollow core and mesoporous shell structure (hmHAp) were synthesized by a template method. Secondly, Au NPs were successfully conjugated onto the surface of hmHAp through the electrostatic attraction. The synthesized hmHAp-Au/MTX had high biocompatibility and pH responsive features. Moreover, the drug release of hmHAp-Au/MTX was pH-dependent because of the dissolution of HAp under acidic conditions. Furthermore, the combined treatment on the cancer cells by using hmHAp-Au/MTX for synergistic hyperthermia ablation and chemotherapy was demonstrated to exhibit higher therapeutic efficacy, presenting the great potential of the platform for cancer therapy.

Formaldehyde-Controlled Synthesis of Multishelled Hollow Mesoporous SiO2 Microspheres.

We developed a facile one-pot method to synthesize multishelled hollow mesoporous SiO2 microspheres (HMSs) with controllable interior structures including one-shell, double-shell, and yolk-shell. Single reagent formaldehyde could fully control the morphology of HMSs, in that formaldehyde was crucial to the SiO2 precursor's hydrolysis rate and the template pore size.

Carbon paper with attached hollow mesoporous nickel oxide microspheres as a sulfur-hosting material for rechargeable lithium-sulfur batteries

Hollow nickel hydroxide microspheres built of nanosheets could be obtained by hydrothermal synthesis in the presence of glycine. After heating to 400 °C in air, the hexagonal β-Ni(OH)2 was converted into cubic NiO which showed better electrical conductivity and greater surface area compared with other annealing temperatures. The surface morphology remained almost unchanged, while the Ni(OH)2 nanosheets with solid interior were changed into NiO nanosheets composed of interconnected nanoparticles and mesopores after annealing at 400 °C. The sulfur-filled hollow mesoporous NiO microspheres obtained after annealing at 400 °C was loaded into the carbon paper as cathode (NiO/S) for lithium-sulfur batteries. The NiO/S cathode could deliver a large specific capacity of 1300 mAh g−1 at 0.2C (335 mA g−1), much greater than bare sulfur loaded into the carbon paper (1000 mAh g−1). Moreover, the NiO/S cathode showed superior capacity recovery after C-rate test and coulombic efficiency during cycling test than S cathode. The improved performance for NiO/S could be attributed to the conductive NiO microspheres with mesoporous nanosheets that provided intimate electrical contact for boosting the charge-transfer reaction between lithium ions and sulfur materials, limited the polysulfide shuttle, and buffered volumetric expansion/contraction during charging and discharging.

Vesicular Li3V2(PO4)3/C hollow mesoporous microspheres as an efficient cathode material for lithium-ion batteries

Vesicular lithium vanadium phosphate/carbon hollow mesoporous microspheres were fabricated using a facile polyvinylpyrrolidone-assisted aerosol-spray-assisted method and subsequent heat-treatment. While changing the content of polyvinylpyrrolidone, we found that carbon content was adjustable on the surface of lithium vanadium phosphate. By optimizing the carbon content among the composites, the electrochemical performance can be enhanced significantly. The results of electrochemical performance tests suggested that the samples exhibited good cycle performance and high discharge capability in the voltages between 3.0–4.8 V. The observed excellent electrochemical performances could be attributed to the proper content of carbon coating and the vesicular hollow mesoporous microsphere structure, increasing the transmission rate of lithium ions and reducing the structural change during charging and discharging effectively.

Incorporation of cerium oxide in hollow mesoporous bioglass scaffolds for enhanced bone regeneration by activating the ERK signaling pathway

Hierarchically porous structures and bioactive compositions of artificial biomaterials play a positive role in bone defect healing and new bone regeneration. Herein, cerium oxide nanoparticles-modified bioglass (Ce-BG) scaffolds were firstly constructed by the incorporation of hollow mesoporous Ce-BG microspheres in CTS via a freeze-drying technology. The interconnected macropores in Ce-BG scaffolds facilitated the in-growth of bone cells/tissues from material surfaces into the interiors, while the hollow cores and mesopore shells in Ce-BG microspheres provides more active sites for bone mineralization. The cerium oxide nanoparticles in the scaffolds rapidly promoted the proliferation and osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs), as confirmed by the up-regulation of osteogenesis-related markers such as OCN, ALP and COL-1. The enhanced osteoinductivity of Ce-BG scaffolds was mainly related to the activated ERK pathway, and it was blocked by adding a selective ERK1/2 inhibitor (SCH772984). In vivo rat cranial defect models revealed that Ce-BG scaffolds accelerated collagen deposition, osteoblast formation and bone regeneration as compared to BG scaffolds. The exciting results demonstrated that the synergistic effects between hierarchically porous structures and cerium oxide nanoparticles contributed to osteogenic ability, and hollow mesoporous Ce-BG scaffolds would be a novel platform for bone regeneration.

Coordination Complex Transformation-Assisted Fabrication for Hollow Chestnut-Like Hierarchical ZnS with Enhanced Photocatalytic Hydrogen Evolution.

Hierarchical nanostructures (HNs) are possibly endowed with novel properties due to their complex three-dimensional (3D) structures. Here, we provide a novel stepwise growth strategy of Coordination Complex Transformation-Assisted Growth for fabricating HNs. By using this, we prepare a new wurtzite ZnS HNs-hollow chestnut-like hierarchical microspheres (HCHMs), which are mesoporous hollow microspheres with single crystalline nanorods arrayed densely and radially from the centre. The HCHMs formation depends on the stepwise decomposition of the two Zn2+ complexes ([Zn(en)m(H2O)2(3−m)]2+ and [Zn(en)m(NH3)2(3−m)]2+, natural number m < 3). As the reaction proceeds, [Zn2+] has been distinctly reduced due to the transformation from [Zn(en)m(H2O)2(3−m)]2+ to [Zn(en)m(NH3)2(3−m)]2+ with a high stability constant, leading to a low crystal growth rate to obtain single crystalline nanorods. Additionally, the generated bubbles (CO2, NH3) acting as a template can induce the generation of hollow structure. The as-prepared ZnS HCHMs show an enhanced photocatalytic hydrogen evolution activity due to the single crystalline wurtzite phase and the high surface area contributed by the hollow hierarchical structures, as well as the mesoporosity. The versatility of the coordination complex transformation-assisted growth strategy will open up new possibilities for fabricating HNs, especially for those transition metal ions with excellent complex capabilities.