Hollow Mesoporous Spheres Research Articles

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.

Synthesis and Effective Thermal Conductivity Measurements of Hollow Mesoporous SiO2 Spheres for Heat‐Insulating Applications

Mesoporous silica hollow spheres are an excellent model system to investigate the thermal conductivity for an efficient heat‐insulating material with respect to its geometry. Four different monodisperse silica hollow spheres are synthesized via a three‐step synthesis consisting of emulsifier‐free emulsion polymerization, modified Stöber condensation process, and subsequent calcination. In this approach, cetyltrimethylammonium bromide (CTAB) is used as a structure directing component to produce a highly porous silica shell. The systematic investigations of the effective thermal conductivity (ETC) allow distinguishing the respective conduction pathways, such as solid conduction and gas conduction. The carried out thermal conductivity measurements reveal for all four samples promising low ETC values of ≈36 mW m−1 K−1 at 1013 mbar and 35 °C. In vacuum (0.03 mbar) all four samples showed, independent of shell thickness and inner diameter, a comparable reduced ETC of about 10 mW m−1 K−1. The comparison with previous studies on unstructured silica hollow spheres indicates that the solid state conductivity within the bulk is more dependent on the contact strengths and the number of contacts than on the thermal conductivity within the silica material, as the scattering probability of phonons is not influenced by an increased density of defects.

PEI grafted Fe3O4@SiO2@SBA-15 labeled FA as a pH-sensitive mesoporous magnetic and biocompatible nanocarrier for targeted delivery of doxorubicin to MCF-7 cell line

In this study, the synthesis and surface modification of mesoporous magnetite nanoparticles (Fe3O4@SiO2@SBA-15) using a cationic biodegradable and biocompatible copolymer have been reported. For this purpose firstly, the mesoporous magnetic nanoparticles (MMNPs) were synthesized by sol-gel methods on Fe3O4 nanoparticles. Then they were modified with TMVS and amino acid L-cysteine for preparing VMMNPs- L-cysteine. In another reaction, the PEI was modified with CM-β-CD and FA which was embedded into the CD cavity via host-guest interaction for preparing PEI/CM-β-CD/FA. Finally, the PEI/CM-β-CD/FA was successfully grafted onto VMMNPs- L-cysteine for the synthesis of a novel hollow mesoporous sphere as a nanocarrier. The structure and magnetic properties of the targeted MMNPs nanocarrier were confirmed by FT-IR, TGA, XRD, VSM, zeta potential analysis, SEM, and EDX analysis. The in-vitro drug release and drug loading capacity were measured using UV spectroscopy. Finally, to investigate the effect of this drug-nanocarrier on breast cancer cells, the MCF7 cells were cultured and the cell death rate was determined by MTT assay and drug IC50 after treatment with these drug nanocarriers (The concentration of each drug derivative that reduces cell growth by 50 % compared to control culture). Fluorescence microscopy was used to observe the morphology changes of the cancer cell nuclei.

Immobilized Lipase Based on Hollow Mesoporous Silicon Spheres for Efficient Enzymatic Synthesis of Resveratrol Ester Derivatives.

Enzymatic esterification of resveratrol is crucial for its potential application in lipophilic foods and drugs. However, the poor activity of the free enzyme hinders the reaction. In this work, the highly efficient enzymatic synthesis of resveratrol ester derivatives was achieved by immobilized lipase on hydrophobic modified hollow mesoporous silicon spheres (HMSS-C8). We preliminarily explored the use of Candida sp. 99-125 lipase (CSL) for the acylation of resveratrol, with a regioselectivity toward 3-OH- over 4'-OH-acylation. HMSS-C8 provided ideal accommodation for CSL with a loading capacity of up to 652 mg/g. The catalytic efficiency of CSL@HMSS-C8 was 15 times higher than that of free CSL, and the conversion of resveratrol reached 98.7% within only 2 h, which is the fastest value recorded in the current literature. After 10 cycles, the conversion remained up to 86.3%. Benefiting from better lipid solubility, the relative oxidation stability index values of oil containing monoester derivatives were 43.1%-68.8% and 23.9%-33.2% higher than that of refined oil and oil containing resveratrol, respectively. This research provides a new pathway for efficient enzymatic synthesis of resveratrol ester derivatives and demonstrates the potential application of resveratrol monoester derivatives as a group of excellent lipid-soluble antioxidants.

High-rate and high conductivity mesoporous TiO2 nano hollow spheres: Synergetic effect of structure and oxygen vacancies

TiO2 is exceptionally useful anode material for Li-ion batteries, and the ability to modify TiO2 makes it a very attractive and challenging research object for use in different functional materials. In this paper, mesoporous TiO2 nano hollow spheres (dubbed TiO2-1 andTiO2-2) with moderate oxygen vacancies were successfully prepared. Structure and composition characterizations revealed that the spheres had a hollow structure, surface oxygen vacancies and an excellent Ti3+/Ti4+ molar ratio of 0.181. In addition, TiO2-2 demonstrated synergistic effects in terms of electron and lithium ion transportation, with impedances as low as 3.05 Ω, and its Li-ion diffusion coefficient (7.8 × 10−12 cm2 s−1) was at least a factor of 10 larger than that of TiO2-1(6.2 × 10−13 cm2 s−1). More importantly, experiments demonstrated that the well-balanced Li+/e− transportation arising from the synergetic effect between structure and Ti3+/oxygen vacancy in the optimal TiO2-2 sample had a high specific capacity of 233 mAh·g−1 at 0.1C, and 79.8% capacity retention after 100 cycles, as well as greatly enhanced rate performance and electrochemical reactivity and stability in comparison with the other TiO2. Our method for creating oxygen vacancies in TiO2 nano hollow spheres can be generalized to other electrochemical energy storage materials.

N-Doped Carbon Hollow Spheres for the Simultaneous Determination of Atorvastatin and Amlodipine by Synchronous Fluorescence Spectrofluorimetry

A green and sensitive analytical procedure by dispersive solid-phase nanoextraction (DSPNE) strategy based on mesoporous nitrogen-doped hollow carbon sphere as adsorbent is developed for the simultaneous determination of atorvastatin (AT) and amlodipine (AM) in spiked human plasma. The determination method was based on measuring the synchronous fluorescence intensity of the drugs at a constant wavelength difference (Δλ=40 nm). The different experimental parameters influencing the extraction efficiency of the two drugs were studied and optimized. The limits of detection were 3.24 and 0.406 ng. ml -1 and quantification limits were 10.8 and 1.36 ng. ml -1 for AT and AM, respectively. Validation assays indicated that the concentration ranges were linear in 11-120 for AT and 2-90 ng ml -1 for AM, with R 2 >0.993 for both drugs. Under optimum conditions, extraction recovery was 94% and 89% with RSD% 3.9 and 4.7 (n=4) for AT and AM, respectively. The developed method has been found to be simple, economical, and reproducible for the routine analysis of both drugs in biological fluids.

Hollow mesoporous organosilica nanospheres with multiple tiny silver nanoparticles: A polymer mediated growth approach and catalytic application

The fabrication of nanostructured catalysts based on noble metal nanoparticles has attracted much attention. In this study, multiple tiny Ag nanoparticles loaded hollow mesoporous organosilica spheres (MT-Ag@HMOS) were synthesized by a novel polymer mediated growth approach. During the preparation, polyacrylic acid@hollow mesoporous organosilica spheres (PAA@HMOS) were first produced formed by condensation of organosilica precursor on polyacrylic acid (PAA) colloids; subsequently, tiny Ag nanoparticles were in situ immobilized both in the cavity and on the shell of PAA@HMOS due to their abundant thioether groups and unique structure. The produced materials were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), N2 adsorption-desorption instruments, X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). The MT-Ag@HMOS exhibited a spherical morphology with an average diameter of about 120 nm, a high surface area of 76.5 m2·g−1, as well as high content of tiny Ag nanoparticles (approximately 3 nm). In addition, the catalytic activities of the MT-Ag@HMOS on 4-nitrophenol (4-NP), Congo red (CR), and Rhodamine B (RhB) reduction in the presence of NaBH4 in aqueous medium were investigated. Experimental results show MT-Ag@HMOS particles are promising candidates for the treatment of waste water supplemented contaminated by 4-NP and various dyes.

Fe2Mo3O8 nanoparticles self-assembling 3D mesoporous hollow spheres toward superior lithium storage properties

Unique self-assembled iron(II) molybdenum (IV) oxide (Fe2Mo3O8) mesoporous hollow spheres have been facilely constructed via the bubble-template-assisted hydrothermal synthesis method combined with simple calcination. The compact assembly of small nanoparticles on the surface of the hollow spheres not only provides more active sites for the Fe2Mo3O8, but also benefits the stability of the hollow structure, and thus improved the lithium storage properties of Fe2Mo3O8. The Fe2Mo3O8 mesoporous hollow spheres exhibit high initial discharge and charge capacities of 1189 and 997 mA·h·g−1 respectively, as well as good long-term cycling stability (866 mA · h · g−1 over 70 cycles) when used as a lithium-ion battery anode. This feasible material synthesis strategy will inspire the variation of structural design in other ternary metal molybdates.

Hybrid OER Electrocatalyst Combining Mesoporous Hollow Spheres of N, P-Doped Carbon with Ultrafine Co2NiOx

A heterostructure combining mesoporous hollow spheres of N, P-doped carbon (meso-NPC) with ultrafine Co2NiOx nanoparticles has been synthesized as a highly active electrocatalyst, named meso-NPC/Co2NiOx. The meso-NPC hollow spheres were first fabricated via a novel nanocasting method using mesoporous SiO2 as the "mold" and the atomic ratio of P in the meso-NPC can be tuned by controlling the amount of one of the filling organics, etidronic acid. Because of the large surface area and abundant surface hydroxyls, the meso-NPC formed strong bonding with the Co2NiOx nanoparticles (<2 nm in size) loaded on it. Serving as an OER electrocatalyst, the heterogeneous meso-NPC/Co2NiOx shows great working enhancement compared to its single-component counterparts. Through further mechanism study by X-ray photoelectron spectroscopy, a strong effect of electron transfer is found from the Co2NiOx to the meso-NPC, which leads to increases in the oxidation state of transition metals (TMs). Most importantly, we also reveal that the increase in the amount of the P dopant in the meso-NPC/Co2NiOx system can efficiently facilitate this metal-to-support charge transfer, which also implies that the biphasic interaction between the Co2NiOx nanoparticles and the meso-NPC hollow spheres generates active catalytic sites of both TM-N-C and TM-P-C surface species.

Fabrication of FeS2/SiO2 Double Mesoporous Hollow Spheres as an Artificial Peroxidase and Rapid Determination of H2O2 and Glutathione

Nanozymes as one of artificial enzymes show many advantages than natural enzymes. The high Michaelis-Menten constant (Km) to H2O2 is the drawback for nanozymes, which means a high H2O2 concentration to oxidize 3,3',5,5'-tetramethylbenzidine (TMB). For this problem, FeS2/SiO2 double mesoporous hollow spheres (DMHSs) were first synthesized as an artificial peroxidase through a solid reaction. The experimental results demonstrate that Fe3O4 vulcanization and DMHS formation were effective strategies to enhance affinity to H2O2 for the nanozyme. The Km of FeS2/SiO2 DMHSs (H2O2 as the substrate) is 18-fold smaller than that of FeS2 nanoparticles (NPs). The catalytic efficiency (Kcat/Km) of FeS2/SiO2 DMHSs is about 16 times higher than that of FeS2 NPs. FeS2/SiO2 DMHSs can be used as a nanozyme to sensitively and rapidly detect H2O2 and glutathione within 1 min at room temperature.

S, Na Co-Doped Graphitic Carbon Nitride/Reduced Graphene Oxide Hollow Mesoporous Spheres for Photoelectrochemical Catalysis Application

As an environmentally friendly visible-light-responsive and metal-free photocatalyst, the photoelectrochemical (PEC) performance of graphitic carbon nitride (CN) has still been limited by its large...

FeS2/SiO2 mesoporous hollow spheres formation and catalytic properties in the Fenton reaction

Transition metal sulfides (TMSs) show excellent catalytic activity in the Fenton reaction. However, the metal ion in TMSs always leached in solution during the reaction, which induced the second pollution. At present, mesoporous hollow spherical FeS2/SiO2 composite was synthesized, which the FeS2 particles were deposited at the inner wall of SiO2 hollow spheres. The composite exhibited higher adsorption capacity and catalytic activity for rhodamine B (RhB) degradation in the Fenton reaction than FeS2. The Fe ionic concentration leashed from the composite is smaller about 24-fold than the FeS2. This method provides a possible solution for the stable TMSs formation as catalysts in the Fenton reaction.

Water-based epoxy coatings with pH-sensitive TiO2 containers for active corrosion protection of carbon steel

ABSTRACT Smart containers can be produced with polyelectrolyte multilayers that can release inhibitors in response to environmental changes at the coating defects. In this study, mesoporous TiO2 hollow spheres were adopted as carriers for the encapsulation of corrosion inhibitor. The inhibitor-loaded TiO2 containers were modified by polyelectrolyte shells using layer-by-layer self-assembly technology. The release behaviour of the encapsulated inhibitor was investigated using UV–visible spectroscopy. Corrosion protection performance of the epoxy coating with polyelectrolyte-modified TiO2 containers was studied using electrochemical impedance spectroscopy and scanning Kelvin probe (SKP) techniques. Epoxy coating with the polyelectrolyte-modified TiO2 containers provided better barrier properties than that of the blank coating. Waterborne epoxy coating impregnated with the polyelectrolyte-modified TiO2 containers presented a significant self-healing effect after immersion in 0.5 M NaCl solution from the SKP results.

Construction of mesoporous Li4Ti5O12 hollow spheres for high rate lithium ion batteries

In this study, a simple targeted etching approach was developed for the controlled fabrication of mesoporous Li4Ti5O12 (LTO) hollow spheres, which can be used as an advanced anode material in lithium-ion batteries. We investigated the controllable synthesis of mesoporous LTO hollow spheres with various hollow structures based on different compositions, such as yolk-shelled and hollow structures with porous shells. The as-prepared mesoporous LTO hollow spheres had several main structural advantages, including high intrinsic interfacial reactivity with the electrolyte due to a high specific surface area, extra space for the storage of lithium ions, and reduced transport path lengths for both e– and Li+, thereby leading to excellent rate performance. Moreover, the high reversible capacity of the mesoporous LTO hollow spheres was 229.2 mA h g−1 after 1000 cycles at 0.5C and the highest rate discharge capacity was 114.2 mA h g−1 at 10 C, thereby indicating the outstanding cycle stability and rate performance of LTO as an anode in lithium-ion batteries.

Size controllable synthesis and photocatalytic performance of mesoporous TiO2 hollow spheres

Hollow mesoporous TiO2 spheres (THs) were prepared via template-directed deposition of TiO2 nanoparticles on the surface of carbon spheres. The carbon spheres were used as hard templates. Their diameters were controlled by pH adjustment prior to a hydrothermal process. Physical properties, such as crystallinity, optical characteristics, microstructure and surface morphology of the samples were characterized. The results showed that the diameter of the carbon template could be well controlled in the range of 397–729 nm by adjusting the initial pH value of the dextrose solution from 3 to 10. Hollow TiO2 spheres with average diameters ranging from 171 to 668 nm and shell thicknesses ranging from 28 to 47 nm formed by heat treatment at 450 °C. The photocatalytic performance of hollow TiO2 spheres and TiO2 nanoparticles was examined under UVA irradiation using a methyl orange aqueous solution as an artificial dye. The study revealed that the THs synthesized using a dextrose solution at pH 7 had a higher photocatalytic activity compared to other samples since it had the lowest shell thickness and the proper optical band gap of 3.12 eV with the longest lifetime of electron-hole pair separation.

Step‐by‐step synthesis of copper(I) complex supported on platinum nanoparticle‐decorated mesoporous silica hollow spheres and its remarkable catalytic performance in Sonogashira coupling reaction

In this study, a step‐by‐step method for the synthesis of platinum nanoparticles and copper(I) complex supported on mesoporous silica hollow spheres (Pt‐MSHSs‐Cu) is introduced. Scanning electron microscopy, transmission electron microscopy, powder X‐ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption, energy‐dispersive X‐ray spectrometry, X‐ray photoelectron spectroscopy, and elemental and thermogravimetric analyses were applied for characterization of the surface, structure, size, phase composition, and morphology of the synthesized materials. The characterized material, Pt‐MSHSs‐Cu, was used as an efficient and heterogeneous catalyst in the Sonogashira coupling reaction under different reaction conditions. In comparison with MSHSs, Cu(I)‐functionalized MSHSs (MSHSs‐Cu), and Pt‐MSHSs samples, the Pt‐MSHSs‐Cu catalyst exhibited significantly increased catalytic performance with 91.50% yield. Therefore, the results obtained suggested a synergistic effect derived from platinum nanoparticles, MSHSs substrate, and copper(I) complex, which enhanced the rate of the Sonogashira coupling reaction.

Structure-switchable mesoporous carbon hollow sphere framework toward sensitive microwave response

Mesoporous carbon hollow sphere (MCHS) is one of the most significant functional materials in various fields. Unfortunately, systematically regulating microstructure of MHCS has been rarely investigated so far. In this work, using one unique simultaneous-hydrolyzation-polymerization process, we are able to precisely control the morphology configurations of MCHS, including its shell thickness and integrate size, hollow void and mesopore in the shell. The shell thickness and integrate size are associated with the synergistic effect of hydrolyzation and polymerization reactions. The hollow void and mesopore are determined by the SiO2 template morphology. Thus, a series of MCHSs with controlled microstructure were achieved through elaborately tuning the precursor. More importantly, different types of MCHSs demonstrate significantly different dielectric and microwave absorbing properties due to the discrepancy of volume ratio between pores and carbon compositions. The typical sample could achieve a broad effective absorption bandwidth of 5.9 GHz and 6.5 GHz with a thickness of 2.35 mm and 2.65 mm, respectively, at a filling ratio of only 20 wt%. These encouraging results significantly promote a deeper understanding of the fundamental chemistry mechanism for constructing MCHS as well as using the material as potential candidate for solving microwave interference issue.

Au nanoparticle-embedded, nitrogen-deficient hollow mesoporous carbon nitride spheres for nitrogen photofixation

Gold-embedded, nitrogen-deficient hollow mesoporous carbon nitride spheres are constructed to give a solar-to-ammonia conversion efficiency of 0.032% for nitrogen photofixation.

Virus-mimicking mesoporous organosilica nanocapsules with soft framework and rough surface for enhanced cellular uptake and tumor penetration.

An enveloped virus with soft and rough shells has strong penetration ability for cells. Inspired by the unique structure of virus, we successfully constructed virus-mimicking mesoporous organosilica nanocapsules (denoted as VMONs) for the first time by decorating small-sized silica nanoparticles on soft mesoporous organosilica hollow spheres. TEM and SEM images reveal that the prepared VMONs display uniform diameters (240 nm), a soft framework, a rough surface, and excellent dispersity. Quantitative nanomechanical mapping further demonstrates that the VMONs possess an extremely low Young's modulus (36 MPa) and a scraggly surface. In view of the successful construction of the virus-mimicking nanocapsules, the VMONs are further modified with human serum albumin (HSA) and Cy5.5-maleimide (Mal-Cy5.5) to investigate their cell penetration ability. Flow cytometry analysis reveals that the internalization of VMONs@HSA-Cy5.5 increases 2.74-fold compared to that of the conventional mesoporous nanosphere. Confocal laser scanning microscopy images show that the VMONs@HSA-Cy5.5 diffuses deeper for multicellular spheroids compared to both hard and soft mesoporous organosilica nanospheres. The penetration ability of the VMONs and SMONs increases 18.49 and 6.13-fold compared to that of MONs at the depth of 60 μm. Thanks to the excellent cellular penetration ability, the virus-mimicking VMONs@HSA-Cy5.5 can effectively deliver the anticancer drug doxorubicin (Dox) into drug-resistant MCF-7/ADR human breast cancer cells and significantly enhance the chemotherapeutic efficacy. Taken together, the constructed virus-mimicking organosilica nanocapsules with a soft framework and a rough surface possess strong cellular internalization and tumor penetration abilities, providing a unique and effective nanoplatform for biomedical applications.

Atomic intercalation of magnesium in mesoporous silica hollow spheres and its effect for removal of dyes

“Atomic” intercalation of magnesium (Mg) in mesoporous silica hollow spheres which are composed of ultrathin nanosheets with several nanometers in width has been achieved through a one-pot hydrothermal synthesis process. The highly dispersed state of Mg in the silica hollow spheres leads to the creation of more complicated shell morphology with higher surface area and larger pore volume than the silica hollow spheres without Mg. With the Mg intercalation, the structure may provide not only suitable spaces but also surface functions for the adsorption of various organic pollutants. In the removal of dyes (cationic or anionic) in the water solution, the Mg intercalated silica spheres showed much higher adsorption capacity in contrast to the silica hollow spheres without Mg. The removal efficiency can also be well maintained for repeated usage after the recovery. The work presents a new strategy to obtain silica spheres with highly homogeneously dispersed Mg and also may further promote the potential applications of hybrid silica materials in catalysis, drug delivery, and biosensing etc.