Mesoporous Core Research Articles

Mesoporous Pd@Pt nanoparticle-linked immunosorbent assay for detection of atrazine

Atrazine is a widely used herbicide in the United States; however, the Environmental Protection Agency (EPA) has issued warnings about atrazine because of its reported potential harmful effects on animals and humans. Therefore, developing efficient ways to detect this herbicide’s residue are critically important. The competitive ELISA is a useful method for detecting chemicals for which antibodies exist due to its high sensitivity, specificity, and efficiency. However, the assay typically requires a separate application of a secondary antibody linked to an enzyme that catalyzes conversion of a non-colored organic to a detectable colored product.In this study, we used the recently developed peroxidase-like mesoporous core–shell palladium@platinum (Pd@Pt) nanoparticle which can easily be bound directly to primary antibody, thereby eliminating the need for a secondary antibody conjugate. We report a first instance in which this technique is applied for use in a competitive assay for small molecules, in this case the herbicide atrazine. Due to their high-surface area and mesoporous structure, Pd@Pt nanoparticles enable fast mass transfer for reaction with excellent catalytic activity. This leads to high sensitivity in our immunoassay with a limit of detection of 0.5 ng mL−1 defined by selecting an IC10 concentration, i.e., the analyte concentration at which 10% of the available Pd@Pt nanoparticle-labeled antibody is inhibited from binding to a plate coated with a bovine serum albumin-atrazine conjugate. We applied our method to well-water and pond water samples spiked with atrazine. Our tests at 5, 10, and 20 ng mL−1 yielded recoveries of 99 – 115%, offering strong supporting evidence that atrazine and other low molecular weight herbicides and pesticides can be detected using this immunoassay approach. Detection with this method is expected to lead to its use in a wide spectrum of applications in agriculture, medical, and biotechnology arenas.

Optimizing the electromagnetic wave absorption performances of designed Fe3O4@SiO2@MnO2 hybrids

Whereas growing numbers of strong-absorption materials have been synthesized in recent years, it is also necessary to design broad-bandwidth, low-thickness, high-intensity absorbers. The ternary Fe3O4@SiO2@MnO2 hybrids were fabricated via hydrothermal and hydrolysis processes, combined with typical core-shell structure characteristics and heterogeneous properties, further generating interfacial polarization behavior and enhancing anisotropy. Investigations of micromorphology manifested the hierarchical characteristic via the presence of inner mesoporous Fe3O4 cores, outer SiO2 layers (approximately 10 nm) and MnO2 nanosheets as the surface of the hybrids. On the basis of rational design, the optimized multi-layers absorber exhibited excellent absorption performance with optimal reflection loss (RLmin) of −50.2 dB at 13.9 GHz, and the effective absorption band (EAB) is up to 5.1 GHz from 11.5 GHz to 16.6 GHz with the thickness of 2.6 mm. Due to the large surfaces, high porosity as well as the synergistic effect derived from the magnetic Fe3O4 cores and dielectric SiO2@MnO2 layers, this effective strategy may be endowed with high potential to design high-efficient absorbers.

Synthesis of well-defined poly(n-vinylpyrrolidone)/n-TiO2 nanocomposites by xanthate-mediated radical polymerization

For the first time formation of well-defined poly n-vinylpyrrolidone/n-TiO2 nanocomposite by xanthate-mediated radical polymerization was accomplished. The synthesis of polymer nanocomposite materials has been intensively studied due to their extraordinary properties and wide-spread potential applications. For this purpose, first 2‐propionic acid-O-ethyl xanthate, as a RAFT agent, was synthesized by the reaction of 2-bromopropionic acid with potassium O-ethyl xanthate with acetone as the solvent. A carboxylic group in the RAFT agent was attached to the n-TiO2 surface by metalation reaction. Then, RAFT polymerization of n-vinylpyrrolidone (NVP) was subsequently conducted to graft poly(n-vinylpyrrolidone) (PNVP) onto the exterior surface of n-TiO2 nanoparticles, forming a novel core–shell nanostructure with a mesoporous core and a polymeric nanoshell. The viscosimetry data and 1H NMR spectra were used to calculate the molecular weight of the polymer. The obtained results showed a good agreement withthe methods used. A significant enhancement in the stability of the composites was obtained as demonstrated by the TGA results. The SEM and TEM results showed that the polymer was formed on the surface of the particles. The XRD pattern of the nanoparticles of n-TiO2 presented the amorphous structure of the crystal morphology of the composites. The FTIR and UV–visible spectroscopy results proved that the PNVP chains were grafted onto the n-TiO2 nanoparticles by surface RAFT polymerization.

Preparation of Novel Oxygen Carriers Supported by Ti, Zr-Shelled γ-Alumina for Chemical Looping Combustion of Methane

Highly stabilized mesoporous core–shell-structured oxygen carriers (OCs) were fabricated by a repetitive coating process of alumina supports using the mesopore-forming surfactant assembly method. T...

Towards stable lithium-sulfur battery cathodes by combining physical and chemical confinement of polysulfides in core-shell structured nitrogen-doped carbons

Despite intensive research on porous carbon materials as hosts for sulfur in lithium-sulfur battery cathodes, it remains a problem to restrain the soluble lithium polysulfide intermediates for a long-term cycling stability without the use of metallic or metal-containing species. Here, we report the synthesis of nitrogen-doped carbon materials with hierarchical pore architecture and a core-shell-type particle design including an ordered mesoporous carbon core and a polar microporous carbon shell. The initial discharge capacity with a sulfur loading up to 72 wt% reaches over 900 mA h gsulfur−1 at a rate of C/2. Cycling performance measured at C/2 indicates ∼90% capacity retention over 250 cycles. In comparison to other carbon hosts, this architecture not only provides sufficient space for a high sulfur loading induced by the high-pore-volume particle core, but also enables a dual effect of physical and chemical confinement of the polysulfides to stabilize the cycle life by adsorbing the soluble intermediates in the polar microporous shell. This work elucidates a design principle for carbonaceous hosts that is capable to provide simultaneous physical-chemical confinement. This is necessary to overcome the shuttle effect towards stable lithium-sulfur battery cathodes, in the absence of additional membranes or inactive metal-based anchoring materials.

Mesoporous silica-encapsulated gold core–shell nanoparticles for active solvent-free benzyl alcohol oxidation

Silica-encapsulated gold core@shell nanoparticles (Au@SiO2 CSNPs) were synthesized via a tunable bottom-up procedure to catalyze the aerobic oxidation of benzyl alcohol.

Orally administered mesoporous silica capped with the cucurbit[8]uril complex to combat colitis and improve intestinal homeostasis by targeting the gut microbiota.

Inflammatory bowel diseases (IBDs) are still awaiting innovative treatments that can maximize the efficiency of site-specific drug release in the colon while enhancing intestinal homeostasis. Herein, we present multilayer-coated mesoporous silica (MSs) which release payload drugs specifically in the colon tract in the presence of azoreductase produced by the gut microbiota, and simultaneously rejuvenate the tryptophan metabolism of the microbiome to induce activation of the aryl hydrocarbon receptor (AHR) for increased anti-inflammatory effects. The MSs were prepared by using cucurbit[8]uril (CB[8]) as a supramolecular "handcuff" to assemble chitosan/hyaluronic acid multilayers on the periphery of a mesoporous silica core. Strikingly, although MSs remained fairly stable in both acidic and neutral pH, they exhibited excellent responsiveness towards dithionite, an azo-reducing agent employed as a substitute to mimic the specific azoreductase environment in vitro. In comparison with the drug in its free form, hydrocortisone-loaded MSs showed optimized accumulation of therapeutics in the colonic mucosa with minimized premature release in the upper gastrointestinal tract in in vivo imaging and biodistribution studies. The enhanced therapeutic effects of MSs were confirmed in dextran sodium sulfate-induced colitis in mice with promoted colonic epithelial barrier integrity, elevated level of AHR agonists and modulated production of inflammatory cytokines. Furthermore, 16S rRNA analysis showed that the disrupted gut homeostasis of colitic mice was partly corrected by MSs. This novel drug delivery system using self-assembly of tryptophan-functionalized chitosan, which was precomplexed with CB[8], and azobenzene-functionalized hyaluronic acid on the surface of mesoporous silica nanoparticles provides a synergistic gut microbiota-targeting approach for IBD therapy.

A synergistic optical strategy for enhanced deep-tumor penetration and therapy in the second near-infrared window

A mesoporous core–shell nanohybrid allows delivery of thermophilic enzymes for stromal depletion and high photothermal conversion efficiency for tumor therapy.

Mesoporous Core–Shell Nanostructures Bridging Metal and Biocatalyst for Highly Efficient Cascade Reactions

Mesoporous core–shell structured nanocatalysts with a PdPt bimetallic core and enzyme-immobilized polydopamine (PDA) shell were designed, in which the PDA shell worked as a barrier to position the ...

Comparative studies on structural, magnetic and adsorptive properties of fused Fe2O3@ SiO2and rattle shapedSiO2@Fe2O3nanospheres with reversal of core-shell

Synthesis of core-shell nanocomposites is an important domain due to their applications as nanoadsorbents for heavy metal ions. In the present work, rattle type SiO2@Fe2O3 core-shell nanospheres were synthesized by surfactant assisted direct precipitation of SiO2 on Fe2O3 nanoparticles. Whereas, fused magnetic nanospheres encapsulating mesoporous silica cores i.e. Fe2O3@SiO2 were formed by sonication method. Different techniques viz. SEM-EDX, TEM, XRD, BET and VSM were used for the confirmation of structure, crystallinity, surface morphology and magnetic properties of nanospheres. Effect of pH, contact time, adsorbent dose and temperature on Cd(II) adsorption was evaluated. The experimental data was fitted using Langmuir, Freundlich and D-R isotherm models. Monolayer adsorption efficiency (qm) for Fe2O3@SiO2 (769.0 mgg−1) was higher than SiO2@Fe2O3 (370.0 mgg−1) nanospheres, signifying better adsorption of Fe2O3@SiO2. The results confirmed that the reversal of core-shell can play an important role to effectively tune the properties of Fe2O3–SiO2 nanospheres for efficient removal of heavy metal ions.

Utilising the adsorptivity of mesoporous carbon nanotubes to prepare nanomaterials: A shape-controllable and catalyst-free preparation mechanism of tungsten nanowire and nanodots

Owing to its unique structure of mesoporous carbon shell and hollow tubular core, mesoporous carbon nanotubes (mCNT) are highly regarded as one of the most intrinsic adsorbing materials. Based on its significant property, a catalyst-free and shape-controllable reduction mechanism of ammonium metatungstate (AMT) in mCNT (AMT@mCNT) has been investigated. Reactions in mCNT are distinct because the mesoporous nanotubes can adsorb and release substances during the process. Using a field emission scanning electron microscope, X-ray diffraction, thermogravimetry and mass-spectrometric, the mechanism is determined. Finally, referring to the mechanism, tungsten nanowires and nanodots have undergone shape-controllable preparation via reduction of AMT@mCNT.

Performance of mesoporous HZSM-5 and Silicalite-1 coated mesoporous HZSM-5 catalysts for deoxygenation of straw fast pyrolysis vapors

•Catalytic treating of biomass fast pyrolysis vapors offers a promising route to convert many different types of lignocellulosic biomass into biofuels. Considerable research efforts have focused on using zeolite catalysts, especially the microporous HZSM-5 zeolite. Unfortunately, the zeolite’s initial high activity in forming coke and light gases reduces the overall oil yield. In this contribution, we synthesized conventional HZSM-5 zeolite, mesoporous HZSM-5 zeolite, and a core-shell catalyst consisting of mesoporous HZSM-5 zeolite coated with a thin layer (<20 nm) of silicalite-1 zeolite. The catalysts were characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 and Ar physisorption, temperature programmed desorption of ammonia (NH3-TPD), diffuse reflectance infrared fourier transform spectroscopy (DRIFT) spectra, and 27Al nuclear magnetic resonance (NMR). The catalysts were tested in a tandem micro-pyrolyzer system for deoxygenation of wheat straw derived fast pyrolysis vapors in a downstream catalytic fixed bed reactor and the quantitative product analysis was performed with GC-MS/FID/TCD and TGA-MS. The change in yields of different product groups was monitored during catalyst deactivation for an increasing number of pyrolysis vapor pulses and the cumulative carbon recoveries of all product streams (char, vapors, gas, and coke) were compared at different biomass-to-catalyst ratios (∼4 and ∼1) for catalyst loadings of 2 and 8 mg, respectively. In addition, the yields were compared for the same number of zeolitic acid sites. Even though the coking propensity was highest for the mesoporous HZSM-5 (5.1% carbon recovery of fed biomass at B:C = 1), it showed improved conversion of oxygenates (wt% O of vapors = 15) and a higher tolerance towards deactivation by coking compared to the conventional HZSM-5 (wt% O of vapors = 20). Coating of mesoporous HZSM-5 with silicalite-1 reduced the number of acid sites per mass of catalyst by ∼20%, which is attributed to the addition of the inert silicalite-1 layer and passivation of the external acid sites of the mesoporous HZSM-5. Compared to mesoporous HZSM-5, the added silicalite-1 shell reduced the coke yield by 43% (from 5.1–2.9 wt% of fed biomass carbon) for the same catalyst mass and by 8% (4.7 wt% of fed biomass carbon) for the same total number of acid sites. Furthermore, the tolerance towards deactivation observed for the mesoporous HZSM-5 core was largely preserved—especially for conversion of small oxygenates like acids, alcohols and aldehydes, resulting in vapors with 14 wt% O.

Fractal evolution of dual pH- and temperature-responsive P(NIPAM-co-AA)@BMMs with bimodal mesoporous silica core and coated-copolymer shell during drug delivery procedure via SAXS characterization

The dual (pH- and temperature-) responsive core-shell structured mesoporous nanomaterial P@BMMs were prepared using bimodal mesoporous silica as a core and poly(N-isopropylacrylamide-co-acrylic acid) P(NIPAM-co-AA) copolymer as a shell. Ibuprofen (IBU) was used as a model drug, and the effects of copolymer-coated shell thickness on drug loading and controlled release behavior were investigated by means of N2 sorption isotherms, dynamic light scattering measurements, X-ray diffraction patterns, Fourier transform infrared spectra, scanning electron and transmission electron microscopy, thermogravimetric profiles, and elemental analysis techniques. Particularly, their fractal evolutions in the drug delivery durations were explored via small angle X-ray scattering methods, demonstrating that the resultant P@BMMs before IBU-loading and after releasing possess the typical fractal features with spherical morphology. Meanwhile, the estimation for shell thickness of P@BMMs coating in different time intervals indicated that the drug-loaded capacity was improved with the increasing shell thickness, but drug-released rate varies, strongly depending on both shell thickness and release conditions. The drug delivery mechanism was preliminarily explored, following the Korsmeyer-Peppas model. Finally, cytotoxicity in cell and pharmacokinetic of released-IBU from hybrid nanocomposite in mice via intravenously injection were preliminarily explored.

Hybrid Mesoporous Nanoparticles for pH-Actuated Controlled Release.

Among a variety of inorganic-based nanomaterials, mesoporous silica nanoparticles (MSNs) have several attractive features for application as a delivery system, due to their high surface areas, large pore volumes, uniform and tunable pore sizes, high mechanical stability, and a great diversity of surface functionalization options. We developed novel hybrid MSNs composed of a mesoporous silica nanostructure core and a pH-responsive polymer shell. The polymer shell was prepared by RAFT polymerization of 2-(diisopropylamino)ethyl methacrylate (pKa ~6.5), using a hybrid grafting approach. The hybrid nanoparticles have diameters of ca. 100 nm at pH < 6.5 and ca. 60 nm at pH > 6.5. An excellent control of cargo release is achieved by the combined effect of electrostatic interaction of the cargo with the charged silica and the extended cationic polymer chains at low pH, and the reduction of electrostatic attraction with a simultaneous collapse of the polymer chains to a globular conformation at higher pH. The system presents a very low (almost null) release rate at acidic pH values and a large release rate at basic pH, resulting from the squeezing-out effect of the coil-to-globule transition in the polymer shell.

Coating mesoporous ZSM-5 by thin microporous Silicalite-1 shell: Formation of core/shell structure, improved hydrothermal stability and outstanding catalytic performance

Abstract Nanostructure control is an important improvement strategy for zeolite catalyst. A novel hierarchical core/shell zeolite structure with mesoporous core and thin microporous Silicalite-1 shell was prepared by secondary coating of mesoporous ZSM-5 in this paper. The zeolite structure was proved by the combination of broad characterization techniques especially electron microscopy from different length scales. The combination of focused ion beam scanning electron microscope (FIB-SEM) and scanning transmission electron microscopy (STEM) clearly proved the formation of desired core/shell structure. The as-prepared core-shell structured hierarchical MFI (Framework Type) zeolite showed a high hydrothermal stability, unique acidic property and outstanding catalytic performance in methanol to hydrocarbon reaction and biomass catalytic pyrolysis. The synthesis strategy could be extended to other zeolites and generated a family of novel hierarchical zeolites.

Facile development, characterization, and evaluation of novel bicalutamide loaded pH-sensitive mesoporous silica nanoparticles for enhanced prostate cancer therapy

It is a challenge to deliver therapeutics exclusively to cancer cells, while sparing the normal cells. However, pH-sensitive delivery systems have proved to be highly efficient in fulfilling this task due to their ability to provide on-demand and selective release of drug at acidic tumor sites. As a proof of concept, here pH responsive drug delivery system based on mesoporous core shell nanoparticles (NPs) surrounded with poly acrylic acid (PAA) layers were prepared employing a facile synthesis strategy. Bicalutamide (BIC) was encased into surface functionalized MCM-41 nanoparticles via electrostatic interactions. The synthesized NPs were characterized by nitrogen adsorption and desorption isotherms, SEM-EDS, TEM, LXRD, and WXRD. In vitro release studies demonstrated that BIC-MSN-PAA NPs exhibited a higher release in the acidic media which varied inversely with the increase in pH. Further, the results of cell cytotoxicity assay were evident that BICMSNs exhibited more potent killing of both PC-3 and LNCaP cells than free BIC. PAA-MSNs also exhibited an enhanced cellular uptake and prolonged circulation time in vivo. The results are suggestive of the fact that PAA functionalized MSNs can serve as an effective pH-responsive template and hold a great potential ahead in controlled release and effective cancer treatment.

Full filling of mesoporous carbon nanotubes by aqueous solution at room temperature

Carbon nanotubes (CNTs) have the ideal structure to be used as templates for nanomaterials, especially for nanowires, and the tungsten nanowire is an important nanomaterial that is used as a strengthening phase. Therefore, we have proposed to apply mesoporous CNT (mCNT) as a template to prepare tungsten nanowires. However, the tungsten precursor should fill the hollow tube of mCNT firstly, and very few related studies have been reported. In this paper, we have systematically studied the filling process of ammonium metatungstate (AMT) aqueous solution. The results reveal that owing to the mesopores in the mCNT sidewall, the AMT can be encapsulated into the tube at room temperature (RT) and we can fully fill it without destroying the structure. In addition, vibration and solute concentration are also important factors. Besides, the mesoporous sidewall and hollow tubular core structure of mCNT are prerequisites to realize full filling. Furthermore, tungsten nanowires have been obtained after reduction of AMT in mCNTs.

Investigation of ordered mesoporous carbon@MnO core–shell nanospheres as anode material for lithium-ion batteries

Here, we present a design of core–shell structured carbon@MnO composite nanospheres and investigate its electrochemical performance as an anode material for lithium-ion batteries. The core–shell carbon@MnO composite nanospheres are obtained from the intermediate product of carbon@MnO2 nanospheres by coating a MnO2 layer over the surface of the mesoporous carbon cores, followed by thermal treatment in an inert atmosphere. The morphology and crystal phase of the obtained nanospheres are examined, and the electrochemical properties as a lithium-ion battery anode material are studied. The results demonstrate that the ordered mesoporous carbon@MnO electrode shows remarkable enhancements in lithium storage capacity, rate capability and cycling stability, delivering an average capacity of 572 mAh g−1 at 500 mA g−1 over 1000 charge/discharge cycles. The morphology and phase of the core–shell carbon@MnO electrode material after extended cycling are examined by transmission electron microscopy and X-ray diffraction, which indicate the nanocrystalline rather than amorphous property of the cycled electrode. As MnO is a conversion-type electrode material, the potential polarization of the carbon@MnO composite electrode is also investigated, which exhibits a unique evolution as cycling proceeds.

Synthesis and characterization of sulfonated mesoporous NiO-ICG core-shell solid sphere catalyst with superior capability for methyl ester production.

In the present research, a mesoporous NiO core–shell solid sphere was hydrothermally synthesized, using polyethylene glycol (PEG; 4000) as a surfactant and incomplete carbonized glucose (ICG) as a template. Then, thermal decomposition of ammonium sulphate was employed to convert the as-synthesized material to sulfonated mesoporous NiO–ICG catalyst, in order to accelerate conversion of waste cooking palm oil (WCPO) into ester. The structural, textural, morphological, and thermal characteristics of the synthesized sulfonated mesoporous NiO–ICG catalyst were evaluated using X-ray diffraction (XRD), Raman spectroscopy, temperature programed desorption (TPD), Brunauer–Emmet–Teller (BET), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). Furthermore, the effect of different reaction parameters against reaction time were investigated. Under the optimal transesterification conditions; catalyst loading of 1 wt%, methanol to WCPO ratio of 9 : 1, operation temperature of 100 °C and mixing intensity of 450 rpm, an optimum ester yield of 95.6% was achieved. Additionally, a recyclability study proved that the spent catalyst was highly potential to be reused for nine successive transesterification reactions without further treatment. Finally, the physicochemical characteristics of the produced WCPO methyl ester were evaluated which were highly in accordance with both European (EN; 14214) and American Standards for Testing Materials (ASTM; D6751) specifications.

Cancer cell membrane-cloaked mesoporous silica nanoparticles with a pH-sensitive gatekeeper for cancer treatment.

Nanoparticular drug delivery system (NDDS) has great potential for enhancing the efficacy of traditional chemotherapeutic drugs. However, it is still a great challenge to fabricate a biocompatible NDDS with simple structure capable of optimizing therapeutic efficacy, such as high tumor accumulation, suitable drug release profile (e.g. no premature drug leakage in normal physiological conditions while having a rapid release in cancer cells), low immunogenicity, as well as good biocompatibility. In this work, a simple core/shell structured nanoparticle was fabricated for prostate cancer treatment, in which a mesoporous silica nanoparticle core was applied as a container to high-efficiently encapsulate drugs (doxorubicin, DOX), CaCO3 interlayer was designed to act as sheddable pH-sensitive gatekeepers for controlling drug release, and cancer cell membrane wrapped outlayer could improve the colloid stability and tumor accumulation capacity. In vitro cell experiments demonstrated that the as-prepared nanovehicles (denoted as DOX/MSN@CaCO3@CM) could be efficiently uptaken by LNCaP-AI prostate cancer cells and even exhibited a better anti-tumor efficiency than free DOX. In addition, Live/Dead cell detection and apoptosis experiment demonstrated that MSN/DOX@CaCO3@CM could effectively induce apoptosis-related death in prostate cancer cells. In vivo antitumor results demonstrated that DOX/MSN@CaCO3@CM administration could remarkably suppress the tumor growth. Compared with other tedious approaches to optimize the therapeutic efficacy, this study provides an effective drug targeting system only using naturally biomaterials for the treatment of prostate cancer, which might have great potential in clinic usage.