Mesoporous Spheres Research Articles

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.

Rapid Room-Temperature Synthesis of Mesoporous TiO2 Sub-Microspheres and Their Enhanced Light Harvesting in Dye-Sensitized Solar Cells.

Submicron sized mesoporous spheres of TiO2 have been a potential alternative to overcome the light scattering limitations of TiO2 nanoparticles in dye-sensitized solar cells (DSSCs). Currently available methods for the growth of mesoporous TiO2 sub-microspheres involve long and relatively high temperature multi-stage protocols. In this work, TiO2 mesoporous sub-microspheres composed of ~5 nm anatase nanocrystallites were successfully synthesized using a rapid one-pot room-temperature CTAB-based solvothermal synthesis. X-Ray Diffraction (XRD) showed that the grown structures have pure anatase phase. Transmission electron microscopy (TEM) revealed that by reducing the surfactant/precursor concentration ratio, the morphology could be tuned from monodispersed nanoparticles into sub-micron sized mesoporous beads with controllable sizes (50–200 nm) and with good monodispersity as well. The growth mechanism is explained in terms of the competition between homogeneous nucleation/growth events versus surface energy induced agglomeration in a non-micelle CTAB-based soft templating environment. Further, dye-sensitized solar cells (DSSCs) were fabricated using the synthesized samples and characterized for their current-voltage characteristics. Interestingly, the DSSC prepared with 200 nm TiO2 sub-microspheres, with reduced surface area, has shown close efficiency (5.65%) to that of DSSC based on monodispersed 20 nm nanoparticles (5.79%). The results show that light scattering caused by the agglomerated sub-micron spheres could compensate for the larger surface areas provided by monodispersed nanoparticles.

Mesoporous silica via self-assembly of nano zinc amino-tris-(methylenephosphonate) exhibiting reduced fire hazards and improved impact toughness in epoxy resin

Mesoporous silica@nano-zinc amino-tris-(methylenephosphonate) (m-SiO2@Zn-AMP) spheres were synthesized via a self-assembly process to integrate the outstanding flame retardancy, thermal stability, and mechanical properties of these materials. The results indicated that nano Zn-AMP particles were successfully deposited on the surface of m-SiO2 through electrostatic interactions. The prepared m-SiO2@Zn-AMP was utilized to improve the flame retardancy, smoke suppression, and mechanical properties of epoxy resin (EP). The storage modulus, impact, and tensile strengths of the EP with 1% m-SiO2@Zn-AMP (sample EP/1m-SiO2@Zn-AMP) were increased by 29.9, 50.0, and 23.5 %, respectively, relative to the values for untreated EP. The presence of multiple flame retardant elements (i.e. Si, P, N, and Zn) in the mesoporous spheres led to the formation of high yields of compact char residues and the release of inert substance during combustion, for high flame retardancy and efficient smoke suppression in the condensed and gaseous phase. The EP/5m-SiO2@Zn-AMP sample achieved a V0 rating in a vertical UL-94 test. Compared to untreated EP, the amount of total smoke released and the peak CO production rate of EP/5m-SiO2@Zn-AMP were reduced by 53.1 and 61.5 %, respectively. Additionally, the total heat release and peak heat release rate of EP/5m-SiO2@Zn-AMP were decreased by 45.2 and 57.8 %, respectively.

Realizing synergistic effect of electronic modulation and nanostructure engineering over graphitic carbon nitride for highly efficient visible-light H2 production coupled with benzyl alcohol oxidation

Photocatalytic H2 production based on g-C3N4 faces enormous challenging issues including limited visible-light absorption, poor separation and transfer abilities of photo-generated electron-hole pairs. Herein, we realize the synergistic effect of nanostructure engineering and electronic modulation with a supramolecular assembly mediated synthesis of heteroatom doped g-C3N4 hierarchical mesoporous spheres. The favorable doping site and possible effect on electronic structure are disclosed by DFT calculation with supporting experimental analysis. Impressively, S-doped g-C3N4 delivers a 13.2 times higher H2 production rate than bulk g-C3N4 under visible-light. More importantly, as the dual functional photocatalyst for H2 production and selective oxidation of benzyl alcohol, it can exhibit outstanding activity with a H2/benzaldehyde production rate of 3.76/3.87 μmol h−1, respectively. This work not only provide a new rationale for photocatalytic performance enhancement, but also shed new light on the highly efficient utilization of solar energy by coupling H2 generation with value added chemical production.

Role of titanium dioxide (TiO2) structural design/morphology in photocatalytic air purification

Seven TiO2 morphologies were synthesized and evaluated for photocatalytic oxidation (PCO) of methyl ethyl ketone (MEK) in air. Photocatalysts were fabricated via hydrothermal method and the preparation parameters were adjusted to keep the variations in photocatalysts’ crystallinity, crystal composition, and surface area in narrow ranges, thus, allowing a better understanding of the morphology-performance relationship. Based on the characterization results and data available in literature, possible morphological evolutions for different structures were put forward. MEK removal efficiency improved in the order of solid spheres < mesoporous spheres < nanotubes <3-D hierarchically porous <3-D sea urchin-like < hollow spheres < nanosheets. TiO2 nanosheets were distinctly superior to other morphologies and offered 71.3 % removal efficiency, roughly two times higher than commercial P25. Titania nanosheets excellent performance was attributed to high percentage of exposed [001] facets, synergistic effect of [001] and [101] facets, large number of terminal Ti-OH species, and surface fluorination.

Recent advances in the synthesis of hierarchically mesoporous TiO2 materials for energy and environmental applications.

Because of their low cost, natural abundance, environmental benignity, plentiful polymorphs, good chemical stability and excellent optical properties, TiO2 materials are of great importance in the areas of physics, chemistry and material science. Much effort has been devoted to the synthesis of TiO2 nanomaterials for various applications. Among them, mesoporous TiO2 materials, especially with hierarchically porous structures, show great potential owing to their extraordinarily high surface areas, large pore volumes, tunable pore structures and morphologies, and nanoscale effects. This review aims to provide an overview of the synthesis and applications of hierarchically mesoporous TiO2 materials. In the first section, the general synthetic strategies for hierarchically mesoporous TiO2 materials are reviewed. After that, we summarize the architectures of hierarchically mesoporous TiO2 materials, including nanofibers, nanosheets, microparticles, films, spheres, core-shell and multi-level structures. At the same time, the corresponding mechanisms and the key factors for the controllable synthesis are highlighted. Following this, the applications of hierarchically mesoporous TiO2 materials in terms of energy storage and environmental protection, including photocatalytic degradation of pollutants, photocatalytic fuel generation, photoelectrochemical water splitting, catalyst support, lithium-ion batteries and sodium-ion batteries, are discussed. Finally, we outline the challenges and future directions of research and development in this area.

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.

Mesoporous Metal-Metalloid Amorphous Alloys: The First Synthesis of Open 3D Mesoporous Ni-B Amorphous Alloy Spheres via a Dual Chemical Reduction Method.

Selective hydrogenation of nitriles is an industrially relevant synthetic route for the preparation of primary amines. Amorphous metal-boron alloys have a tunable, glass-like structure that generates a high concentration of unsaturated metal surface atoms that serve as active sites in hydrogenation reactions. Here, a method to create nanoparticles composed of mesoporous 3D networks of amorphous nickel-boron (Ni-B) alloy is reported. The hydrogenation of benzyl cyanide to β-phenylethylamine is used as a model reaction to assess catalytic performance. The mesoporous Ni-B alloy spheres have a turnover frequency value of 11.6 h-1 , which outperforms non-porous Ni-B spheres with the same composition. The bottom-up synthesis of mesoporous transition metal-metalloid alloys expands the possible reactions that these metal architectures can perform while simultaneously incorporating more Earth-abundant catalysts.

In-situ constructing of mesoporous Li4Ti5O12@rGO hybrid spheres as anode materials for lithium-ion batteries

The Li4Ti5O12@rGO (LTO@rGO) mesoporous hybrid spheres have been successfully synthesized by an in-situ conversion route in aqueous LiOH solution using TiO2 spheres as precursor, which was followed by annealing process in Ar atmosphere. The LTO@rGO composites possess a uniform mesoporous spherical structure with diameter of approximately 800 nm, which are assembled by many interconnected nanoparticles with a thin rGO conductive coating. Benefiting from the synergistic effects of the unique nanostructure hybrids, it is proved that the porous can offer large surface area which has high intrinsic interfacial reactivity with the electrolyte, extra space for the storage of Li+, and short transport distances for both e− and Li+. Meanwhile, the rGO coating could enhance effectively the interfacial contact between particles and create a three-dimensional conductive network to greatly facilitate fast transport of e− and Li+, which can improve the rate capacity. Compared with pure LTO, the as-prepared LTO@rGO mesoporous hybrid spheres deliver a higher reversible capacity of 260.1 mAh g−1 at 0.5 C after 500 cycles with highly stable capacity retention of even more than 100%, and the high rate discharge capacity reach 125.9 mAh g−1 at 10 C. Therefore, the LTO@rGO composites display superior high-rate property and ultralong cycling stability, which can provide a potential anode material for LIBs.

Engineering Nickel/Palladium Heterojunctions for Dehydrogenation of Ammonia Borane: Improving the Catalytic Performance with 3D Mesoporous Structures and External Nitrogen-Doped Carbon Layers.

Catalysts based on metallic NPs have shown high activities in heterogeneous catalysis, due to their high fractions of surface-active atoms, which, however, will lead to the sacrifices in stability and recycle of catalysts. In order to balance well the relationship between activity, stability, and recovery, in this paper, we have constructed a 3D mesoporous sphere structure assembled by N-doped carbon coated Ni/Pd NP heterojunctions (Ni/Pd@N-C). This obtained Ni/Pd@N-C has shown high catalytic activity, durability and recyclability for the hydrolytic dehydrogenation of ammonia borane (AB). Further investigations, including experimental and theoretical results, have shown that the unique structural features, the synergistic effect between Ni and Pd, and the coating of N-doped carbon layer are responsible for the good catalytic performance of Ni/Pd@N-C mesoporous spheres.

Metal and Metal Oxide Interaction in Hollow CuO/Pd Catalyst Boosting Ethanol Electrooxidation

A low Pd-loaded lychee-nut-like catalysts of CuO/Pd with hollow nanostructure are prepared by electrochemical displacement reaction, in which a Cu2O mesoporous sphere is as a sacrificial template in the presence of triblock copolymers Pluronic P123 (EO20PO70EO20). Furthermore, the feeding molar ratio of Cu2O and Na2PdCl4 is found to be critical factor for preparing well-defined hollow lychee-nut-like (HLN) CuO/Pd. Morphology, composition and crystal structure of the optimal HLN CuO/Pd catalysts are sufficiently characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The as-synthesized HLN CuO/Pd catalysts show high catalytic activity for ethanol oxidation in alkaline medium and the catalytic mass activity of the HLN CuO/Pd is 5.9-fold of commercial Pd/C and 10.8-fold of Pd black. In turn, HLN CuO/Pd catalysts possess outstanding stability and superior tolerance to CO species. The remarkably electrochemical catalysis performance of HLN CuO/Pd catalysts is attributed to the unique lychee-nut–like open nanostructures and the mutual interaction between Pd and CuO support, which optimizing the electronic structure.

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.

The synthesis and characterization of 3D mesoporous CeO2hollow spheres as a modifier for the simultaneous determination of amlodipine, hydrochlorothiazide and valsartan

Electrochemical sensor based on mesoporous CeO2hollow sphere modified glassy carbon electrode for simultaneous detecting amlodipine, hydrochlorothiazide and valsartan was fabricated.

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.

Controlled formation of porous CuCo2O4 nanorods with enhanced oxidase and catalase catalytic activities using bimetal-organic frameworks as templates

Porous structures with highly dispersed and active catalytic sites are vital to improve the catalytic activity and stability of artificial enzyme-related catalytic reactions. Herein, a novel nanorod-like bimetal-organic framework serving as porous support and supplier of Co2+ and Cu2+ was used to prepare a beneficial porous metal oxide. By optimizing the calcination temperature, the composition of calcined product can be controlled and the nanorods with isolated and highly active CuCo2O4 nanoparticles were obtained. The porous CuCo2O4 nanorods exhibit a pH-dependent catalytic property, that is, they behave as oxidase in acid conditions and catalase in alkaline conditions. The CuCo2O4 nanorods perform dual-enzyme catalytic activity superior to monometallic oxides. What’s more, compared with the reported Co3O4 nanoparticles, Co3O4/CuO hollow nanocage hybrids and NiCo2O4 mesoporous spheres, the porous CuCo2O4 nanorods show higher affinity to 3,3′,5,5′-tetramethylbenzidine with a lower Km value. The superior dual-enzyme catalytic activities of CuCo2O4 nanorods benefit from the high catalytic activity of binary metal oxides and structural stability. After incubating in a wide range of pHs, temperatures and ionic strengths, the catalytic activity of CuCo2O4 nanorods can be maintained. The oxidase activity of CuCo2O4 nanorods can be inhibited in the presence of ascorbic acid, which can be applied in effective detection of ascorbic acid. This study opens a new path to prepare stable and highly active porous artificial enzymes.

Modulating the Charge-Transfer Step of a p-n Heterojunction with Nitrogen-Doped Carbon: A Promising Strategy To Improve Photocatalytic Performance.

Engineering p-n heterojunctions among metal oxide semiconductors to provide a built-in electric field is an efficient strategy to facilitate the separation of photogenerated electrons and holes and improve their photocatalytic activities. However, the inherent poor conductivity of p-n heterojunctions still limits the charge-transfer step and thus hampers their practical application in photocatalysis. In this work, a nitrogen-doped carbon-coated NiO/TiO2 p-n (NCNT) heterojunction with hierarchical mesoporous sphere morphology was synthesized by in situ pyrolytic decomposition of nickel-titanium complexes. The NiO/TiO2 p-n heterojunction in NCNT was fully characterized by several techniques, supported by theoretical calculations and Mott-Schottky plots. On coating with a thin nitrogen-doped carbon layer, the electron transfer of the obtained p-n heterojunction could be significantly enhanced. On account of the favorable structural features of the p-n heterojunction with nitrogen-doped carbon coating and hierarchical mesoporous structure, NCNT exhibited excellent photocatalytic activity toward various reaction systems, including the hydrogen evolution reaction and the visible-light-induced hydroxylation of phenylboronic acids.

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.

Fabrication linalool-functionalized hollow mesoporous silica spheres nanoparticles for efficiently enhance bactericidal activity

To develop a novel food preservation technology for efficiently enhance bactericidal activity in a long term, hollow mesoporous silica spheres (HMSS) with regular nanostructures were applied to encapsulate natural organic antimicrobial agents. The chemical structures, morphologies and thermal stabilities of linalool, HMSS and linalool-functionalized hollow mesoporous silica spheres (L-HMSS) nanoparticles were evaluated by polarimeter, field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), fourier transform infrared (FT-IR), thermal gravimetric analyzer (TGA), nitrogen adsorption-desorption, zeta potential and small angle X-ray diffraction (SXRD). The results show that the linalool was successfully introduced into the cavities of HMSS, and the inorganic host exhibited a high loading capacity of about 1500 mg/g. In addition, after 48 h of incubation, the minimum bactericidal concentrations (MBC) of L-HMSS against Escherichia coli (E. coli), Salmonella enterica (S. enterica) and Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes) were decreased to be 4 (< 5) mg/mL and 8 (< 10) mg/mL, respectively. These results revealed linalool-functionalized hollow mesoporous spheres could efficiently improve the bactericidal activities of the organic component. Furthermore, SEM images clearly showed that L-HMSS indeed had an extremely inhibitory effect against gram-negative (E. coli) and gram-positive (S. aureus) by breaking the structure of the cell membrane. This research is of great significance in the application of linalool in nano-delivery system as well as food industry.

Constructing mesoporous hollow polysulfane spheres bonded with short-chain sulfurs (Sx, x≤3) as high-performance sulfur cathodes in both ether and ester electrolytes

Although organic polysulfanes are promising cathodes for high-performance lithium-sulfur batteries because of the covalently bonded sulfur to suppress the shuttle effect, those with linear polymer substrates tend to generate long-chain sulfurs (Sx, x ​= ​4–16) that is liable to yield soluble lithium polysulfides and thus could not effectively prevent the shuttle effect. Herein, novel mesoporous hollow sulfurized aminophenol-formaldehyde resin (polysulfane)/carbon nanotube (SAC) spheres with covalently linked short-chain sulfurs (Sx, x ​≤ ​3) are synthesized using a self-template polymerization reaction followed by dissolution and vulcanization processes. The three-dimensional network of aminophenol-formaldehyde resin, the mesoporous hollow structure, and the vulcanization temperature benefit the formation of the short-chain sulfurs (Sx, x ​≤ ​3), suppressing the shuttle effect efficiently. The ex-situ analyses confirm that the unlithiated part of C–S bond could boost the electrochemical kinetics of delithiated reaction. Therefore, the as-prepared SAC cathode exhibits excellent rate performances and high reversible capacities at varied densities, even obtaining a superior structure stability and a very stable cyclability with a loss as low as 0.022% per cycle within 1000 cycles at 2 ​C. Moreover, the SAC could perform stably both in ester and the ether electrolytes.

An efficient 3D ordered mesoporous Cu sphere array electrocatalyst for carbon dioxide electrochemical reduction

The electrochemical reduction of CO2 is a promising solution for sustainable energy research and carbon emissions. However, this solution has been challenged by the lack of active and selective catalysts. Here, we report a two-step synthesis of 3D ordered mesoporous Cu sphere arrays, which is fabricated by a dual template method using a poly methyl methacrylate (PMMA) inverse opal and the nonionic surfactant Brij 58 to template the mesostructure within the regular voids of a colloidal crystal. Therefore, the well-ordered 3D interconnected bi-continuous mesopores structure has advantages of abundant exposed catalytically active sites, efficient mass transport, and high electrical conductivity, which result in excellent electrocatalytic CO2RR performance. The prepared 3D ordered mesoporous Cu sphere array (3D-OMCuSA) exhibits a low onset potential of -0.4 V at a 1 mA cm−2 electrode current density, a low Tafel slope of 109.6 mV per decade and a long-term durability in 0.1 M potassium bicarbonate. These distinct features of 3D-OMCuSA render it a promising method for the further development of advanced electrocatalytic materials for CO2 reduction.