Core-shell Composite Microspheres Research Articles

Preparation of chiral metal–organic framework l-his-MIL-53-NH2@SiO2 composite by in situ growth and chiral post-modification strategies for HPLC enantiomeric separation

l-his-MIL-53-NH2@SiO2 core–shell composite microspheres were prepared by in situ growth and chiral post-modification strategies for chiral separation.

Preparation of polystyrene@Ni@Cu core–shell microspheres by pickering emulsion polymerization and their autonomous motion in a magnetic field applied to anisotropic conductive films

AbstractSuccessfully designed and synthesized PS@Ni@Cu core–shell composite microspheres, which provide efficient electronic transmission for anisotropic conductive films for electronic packaging applications. Herein, a simple method for preparing core–shell composite microspheres using Pickering emulsion polymerization as a template, a dense nano‐nickel shell layer was coated on the surface of polystyrene to obtain PS@Ni microspheres, the microspheres have conductivity and magnetic properties. Then the microspheres were coated with nano‐copper layer by electroless plating to enhance the mobility of electrons in specific media. Finally, the microspheres are laminated in epoxy resin, which can realize directional (horizontal, inclined, and vertical) movement under magnetic field force to form anisotropic conductive film. The conductivity is 171.68 S cm−1, the adhesiveness and conductivity of the film can be changed by adjusting the content of microspheres. The film has excellent thermal stability, good adhesion, and can be anisotropic conductive. The difference in conductivity between the conductive direction and the insulating direction is about 108 orders of magnitude, and it can adapt to strong acids and alkalis and other more extreme environments. It is significance to the development of electronic packaging and is expected to be widely used in the field of electronic devices.

Design and fabrication of reusable core-shell composite microspheres based on nanodiamond for selective enrichment of phosphopeptides.

A kind of core-shell composite microsphere (CM) with nano-on-micro structure was synthesized via grafting amine-modified nanodiamonds onto the surface of monodisperse nonporous polymeric microsphere. In this way, the agglomeration of nanodiamond particles in the solutionwas avoided. After modification with pyrogallol groups, CM could chelate titanium ions (Ti4+) and thus be utilized as immobilized metal affinity chromatography (IMAC) sorbent to enrich phosphopeptides from biological samples. The resulting Ti4+-CM exhibited high enrichment efficiency and specificity to phosphopeptides. A total of 106 of unique phosphopeptides mapped to 29 phosphoproteins were clearly identified from 5 µL ofa milk digest after enrichment. Owing to the strong chelation between Ti4+ and pyrogallol ligands, the Ti4+is not releasedfrom thesorbent after completion of theenrichment process. As a result, the Ti4+-CM sorbent could be reused, and no significant loss of enrichment efficiency occurred even on the fourth run employing a β-casein digest as the sample. The strategy adopted presents a new way to prepare ahigh-performance reusable IMAC sorbent.

Visible light-driven Ag3PO4@resin core-shell microspheres for photocatalytic degradation of methylene blue

A facile approach for fabricating Ag3PO4@resin core–shell composite microspheres as a visible-light-driven photocatalyst has been successfully established. Results revealed that Ag3PO4@resin core–shell composite microspheres can be synthesized using simple anion-exchange reactions. The prepared composite microspheres exhibited a good potential of degrading 2.5 mg⋅L−1 methylene blue solution with a high decoloring efficiency of 99.2% under visible light irradiation for 150 min. Microcalorimetric analysis revealed that the microspheres can effectively degrade methylene blue and decrease its toxicities to soil microorganisms. HPLC analysis showed that the microspheres can degrade phenol at a rate of 99% in 4 h under visible light.

Facile fabrication of PS-CHO@CeO2 core-shell composite microspheres via in-situ chemical deposition and their photocatalytic application on oxidative degradation of MO

In this study, the modified polystyrene aldehyde microspheres (PS-CHO) were first prepared via the copolymerization of the styrene and the acrolein, and then PS-CHO@CeO2 composite microspheres were fabricated through in-situ chemical deposition of CeO2 nanoparticles. These composite microspheres were used to catalyze the oxidative degradation of methyl orange (MO) by H2O2. The morphology of the products was observed by transmission electron microscopy (TEM). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the chemical state and structure. Optical absorption and band energy properties were investigated by ultraviolet-visible/near-infrared diffuse reflectance spectra (UV-Vis-NIR). The degradation process was monitored with ultraviolet-visible spectrometer (UV-Vis). The results revealed that when the mass ratio of PS-CHO and cerium nitrate was 1:0.26, highly-uniformed and well-dispersibility PS-CHO@CeO2 composite microspheres were obtained at pH 8.5 and the concentration of Ce[Formula: see text] ions was significantly increased compared with commercial CeO2 NPs. Under ultraviolet light irradiation, the degradation efficiency of MO by PS-CHO@CeO2 composite microspheres was increased up to 93.03%, which was 1.44 times that of commercial CeO2 NPs in 120 min. The reiteratively tests further proved that the activity of the composite microspheres maintained unchanged after four cycles. The formation and photocatalytic mechanisms of PS-CHO@CeO2 composite microspheres were proposed.

Laccase immobilization on core-shell magnetic metal-organic framework microspheres for alkylphenol ethoxylate compound removal

An amino-functionalized magnetic core-shell structure metal-organic framework (MOF), Fe3O4-NH2@MIL-100 (Fe), has been successfully constructed by a step-by-step method. The composite microspheres exhibited excellent magnetic characteristics, large surface area, and pore size, which were employed for the Trametes versicolor laccase immobilization. The immobilized laccase exhibited high activity recovery (72.05%) and significantly improved stability. The reactive activity remained 75% of its initial activity after storage for 4 weeks. Additionally, when the ambient reached 80 °C, the good stability enabled the immobilization laccase to keep 33% residual activity even after 6 h storage. Application of the immobilized laccase for environmental pollutant alkylphenol polyethoxylate (APEO) removal was also investigated. The results showed the immobilized laccase can remove 100% octylphenol polyethoxylate (OPEO) and 98.16% nonylphenol polyethoxylate (NPEO) in 200 min, and can still achieve 63.42% and 46.17% removal efficiency for OPEO and NPEO after reusing four cycles, respectively. The novel MOF based core-shell magnetic composite microspheres introduced by this study showed promising applications as laccase immobilization support, and both the immobilized laccase and its support had great potential in wastewater treatment.

Preparation of core-shell silica-carbon composite microspheres stationary phase and application in saccharide separation

In this study, core-shell mesoporous silica-carbon composite microspheres (Sil@MC) were prepared by one-step coating of the phenol formaldehyde polymer (PF) on SiO2 surface and by carbonizing the PF polymer under nitrogen atmosphere. The morphology observation of the Sil@MC stationary phase showed that it had good monodispersity. Surface area (302 m2/g), mean pore diameter (9.5 nm), and pore volume (0.63 cm3/g) of Sil@MC materials were also measured by pore structure analysis. The results showed that the Sil@MC was successfully immobilized on the silica particles via copolymerization and carbonization. As a stationary phase of HPLC, the Sil@MC column was filled by a slurry method. The Sil@MC materials formed after calcination of SiO2 coated with phenolic resin could be used for the separation of four polar sugar compounds (D-(+)-glucosamine hydrochloride, glucose, D-(+)-trehalose dihydrat and raffinose) with the mobile phase of acetonitrile-water (containing 0.1% (v/v) formic acid). However, the material formed by calcinating SiO2 without coating phenolic resin could not separate these polar sugar compounds by HPLC-MS. Finally, the representative oligosaccharide isomers of raffinose, melezitose and stachyose, nystose, and human milk oligosaccharide isomers, such as 3'-sialyllactose, 6'-sialyllactose and lacto-N-newtetraose, lacto-N-tetraose, were successfully separated by the Sil@MC column with good peak shapes. The results demonstrates that silica-carbon composites derived from phenolic resin have potential application in polar compounds chromatographic separation.

Preparation of Silver-Coated Silica Microspheres with High Electrical Conductivity Through Pyrogallol-Fe(Ш) Coordinated Surface Functionalization

In this study, we report a facile method to fabricate silica-silver (SiO2/ PG-Fe3+/Ag) core–shell composite microspheres. The surface of SiO2 microspheres is functionalized with pyrogallol-ferric ions (PG-Fe3+) complexes, then Ag ions are reduced to Ag nanoparticles in situ onto the surface of SiO2 microspheres by electroless plating process. The Ag nanoparticles were uniformly coated on the surface of the SiO2 microspheres and formed a distinctive layer, which was confirmed by scanning electron microscopy characterization. The chemical compositions and microstructures of the microspheres were investigated by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The electrical conductivity of the prepared SiO2/ PG-Fe3+/Ag core–shell microspheres was about 1000 S/cm. When the microspheres were filled in methyl vinyl silicone rubber (MVQ), the obtained composites showed good mechanical and electrical properties, indicating their potential applications as conductive and electromagnetic shielding materials.

Construction of Magnetic Covalent Organic Frameworks with Inherent Hydrophilicity for Efficiently Enriching Endogenous Glycopeptides in Human Saliva.

In this work, a magnetic covalent organic framework (COF) with inherent hydrophilicity (denoted mCTpBD) was synthesized through interface deposition of a hydrophilic COF shell on amino group-functionalized magnetite particles via the reaction between a carboxyl group-containing monomer and benzidine. Thanks to the superior hydrophilicity, appropriate porous structure, and easy magnetic separation, the resulting mCTpBD exhibited excellent performance in conveniently enriching glycopeptides from standard samples with a high sensitivity of 0.5 fmol μL-1 and strong size-exclusion effect of up to 1:1000 (w/w). Furthermore, by using the mCTpBD adsorbent, endogenous glycopeptides in saliva of healthy people and patients with inflammatory bowel disease were successfully enriched and identified by the combined liquid chromatography-mass spectrometry/mass spectrometry technology, which indicates a promising prospective of core-shell magnetic composite microspheres with a hydrophilic COF shell in glycoproteomics research.

Supercapacitive and ORR performances of nitrogen-doped hollow carbon spheres pyrolyzed from polystyrene@polypyrrole-polyaniline

Nitrogen-doped hollow carbon spheres (NHCSs) derived from polystyrene@polypyrrole-polyaniline (PS@PPY-PANI) core-shell composite microspheres of large surface area with improved electrochemistry performances have been effectively prepared and characterized systematically. NHCSs exhibited exceptional electrochemical properties with a maximum specific capacitance of 294.9 F g−1 at a 5 mVs−1 with good cycling stability of 95% after 5000 cycles at 0.5 A g−1. It also showed enhanced oxygen reduction reaction (ORR) activity with a high onset potential of 0.83 V vs. RHE at 1600 rpm via the more favorable four-electron pathway in an alkaline medium. Enhanced electrochemical and electrocatalytic performances could arise from the hollow porous spherical structure, high surface area, and considerable pyrrolic-pyridinic nitrogen contents. Pyrolysis commences the incorporation of nitrogen units together with the high degree of graphitization which contributes exceptionally to improve the ion/charge transfers. Significantly, the synergistic effect of pyrolysis and the proper concentration of PPY-PANI improve the overall electrochemistry performances of NHCSs. The excellent cyclic stability, high specific capacitance, and exceptional ORR activity indicate its perspective as an efficient electrode material for supercapacitors and fuel cells.

Construction of magnetic nanoflower biocatalytic system with enhanced enzymatic performance by biomineralization and its application for bisphenol A removal

This study first reported a magnetic nanoflower biocatalyst of the core-shell magnetic composite microspheres with a hierarchical flower-like surface structure, which was consist of the organic component (horseradish peroxidase, HRP) and the inorganic component (Fe3O4@PMG-IDA-Cu2+) through self-assembly in the phosphate buffered saline (PBS) solution. The structure, pattern and crystallization of the magnetic nanoflowers were confirmed through a series of characterization. The optimized results of the magnetic nanoflowers formation conditions demonstrated that their hierarchical structure could effectively enhance the enzyme activity. The magnetic nanoflowers exhibited enhanced durability, stability and reusability through the study of enzymatic properties. The magnetic nanoflowers were applied to remove the bisphenol A (BPA) from water and the removal efficiency reached about 92.1%, meanwhile the enzymatic activity of the magnetic nanoflowers was achieved 183% enhancement in comparison with free HRP. In addition, the magnetic nanoflowers showed outstanding reusability and reproducibility, which would have potential application in biocatalysis.

Preparation and Photocatalytic Activity of Ag2S/ZnS Core–Shell Composites

Ag2S/ZnS core–shell composite microspheres were successfully synthesized via a simple two-step hydrothermal process, in which Ag+ ions might replace Zn2+ ions on the surface of ZnS microspheres via an ion exchange, and subsequently form Ag2S nucleus on the surface of the microspheres. The effect of Ag2S content on the structure, morphology and optical properties of the material was studied in detail. We found that the photocatalytic efficiency of Ag2S/ZnS composites for the degradation of Rhodamine B (RhB) aqueous solution is much higher than that of pure ZnS or Ag2S under solar-simulated light irradiation, which is considered that the combination of a narrow band gap with a wide band gap semiconductor can timely transfer photogenerated electron–hole pairs and rapidly separate photogenerated electrons and holes. Moreover, the catalytic activities of the 4%Ag2S/ZnS sample for oxidation and decomposition of RhB with the assistance of hydrogen peroxide are enhanced with an increase of the degradation efficiency from 68.8 to 90.0% at room temperature.

Easy fabrication of poly(butyl acrylate)/silicon dioxide core-shell composite microspheres through ultrasonically initiated encapsulation emulsion polymerization

In this study, instead of using the usual chemical methods, poly(butyl acrylate)/silicon dioxide (PBA/SiO2) core-shell composite microspheres were prepared using a physical method-ultrasonically initiated encapsulation emulsion polymerization. The morphology and particle size of the PBA/SiO2 microspheres were analysed using transmission electron microscopy (TEM) and dynamic light scattering (DLS). The encapsulation state was determined using X-ray photoelectron spectroscopy (XPS). The composition and thermogravimetric behavior were characterized using Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The TEM and DLS results show that monodisperse PBA/SiO2 core-shell composite microspheres were successfully obtained. The diameter and shell thickness were 150 nm and 15 nm, respectively. The XPS and FTIR results show that there was no new chemical bond between the PBA shell and the SiO2 core. They were just combined by physical adsorption. The encapsulation efficiency of SiO2 microspheres by PBA is 8.2% through TGA. In addition, this article focuses on the formation mechanism of PBA/SiO2 core-shell microspheres prepared through ultrasonically initiated encapsulation emulsion polymerization. Intuitive observation and the results of TEM and DLS, especially the change in zeta potential, clearly indicate an encapsulation process. Thereinto, a bilayer-structure space established by appropriate amount of cetyltrimethyl ammonium bromide (CTAB) molecules is the key to realize ultrasonically initiated encapsulation emulsion polymerization.

Synthesis of anisotropic Janus composite particles based on poly(urushiol borate)

Urushiol, the main component of the natural product of raw lacquer, can react with ester easily owing to its two adjacent phenolic hydroxyls, and urushiol‐ester compounds can polymerize further attributing to its unsaturated side chain. In this work, poly(urushiol borate) (PUB) was coated on the surface of polystyrene (PS) microspheres by transesterification between urushiol and tributyl borate. Then, the core–shell composite microspheres of polystyrene@poly(urushiol borate) (PS@PUB) were obtained. Finally, we used a general method to synthesize anisotropic grenade‐like Janus composite particles of PUB/PS, that is, the core–shell composite microspheres of PS@PUB were swelled assisted protrusion in the emulsion of organic monomer and water. The morphologies of PUB/PS Janus composite particles could be tuned by changing the swelling time and the dosage of organic monomer. POLYM. ENG. SCI., 58:2304–2310, 2018. © 2018 Society of Plastics Engineers

Facile preparation of Fe3O4@MOF core-shell microspheres for lipase immobilization

In this article, a Fe3O4@MOF core-shell microsphere has been successfully prepared by growing MIL-100(Fe), three dimensional (3D) metal–organic frameworks (MOFs) onto Fe3O4 nanoparticles. The resultant composite microsphere exhibited both magnetic characteristics and large specific surface area, making them excellent candidates for enzyme immobilization. Candida rugosa lipase was immobilized as a model enzyme on core-shell microspheres. The results showed that the immobilized enzyme for hydrolysis of olive oil retained >65% of its initial activity at 65°C over 6h; and the residual activity still remained about 60% of the initial activity after the 10th catalysis run. Therefore, such MOF based core-shell magnetic composite microspheres showed promising applications as an enzyme immobilization support.

One-pot fabrication of core-shell fly ash@polypyrrole/Au composite microspheres and their performance for the reduction of nitrophenol

We reported a novel and simple strategy to construct core-shell composite microspheres with fly ash (FA) and Au nanoparticles embedded in polypyrrole (PPy) chains. In an acid medium, activation of FA microspheres, synthesization of Au nanoparticles, and polymerization of PPy were synergistically achieved in one-step green process. The physicochemical characteristics of the Au-PPy/FA composite microspheres were studied by SEM, TEM, FTIR, XRD, TGA and VSM. In the presence of NaBH4 as a reducing agent, the Au-PPy/FA composite microspheres exhibited highly catalytic efficiency in reduction of nitrophenol to aminophenol. The reaction rate constants were calculated through the pseudo-first-order kinetic equation by using the excess amount of NaBH4. For the two isomers of nitrophenol, the reduction rates were particularly investigated and followed the order: 4-nitrophenol>2-nitrophenol. The electronic interaction between Au nanoparticles and PPy chains plays an important role for the highly catalytic efficiency of the Au-PPy/FA. A possible reaction mechanism for the reduction process was also emphasized.

Fabrication of the novel core-shell MCM-41@mTiO2 composite microspheres with large specific surface area for enhanced photocatalytic degradation of dinitro butyl phenol (DNBP)

The mesoporous MCM-41@mTiO2 core-shell composite microspheres were synthesized successfully by combining sol-gel and simple hydrothermal treatment. The morphology and microstructure characteristics of the synthesized materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption measurements, X-ray powder diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis/DRS) and Fourier transform infrared spectroscopy (FT-IR). The results indicate that the composite material possesses obvious core/shell structure, a pure mesoporous and well-crystallized TiO2 layer (mTiO2), high specific surface area (316.8m2/g), large pore volume (0.42cm3/g) and two different pore sizes (2.6nm and 11.0nm). The photocatalytic activity of the novel MCM-41@mTiO2 composite was evaluated by degrading 2-sec-butyl-4,6-dinitrophenol (DNBP) in aqueous suspension under UV and visible light irradiation. The results were compared with commercial anatase TiO2 and Degussa P25 and the enhanced degradation were obtained with the synthesized MCM-41@mTiO2 composite under the same conditions, which meant that this material can serve as an efficient photocatalyst for the degradation of hazardous organic pollutants in wastewaters.

Development of novel anisotropic Janus composite particles based on Urushiol-iron/polystyrene polymer

Abstract The main component of raw lacquer is urushiol (U) which can react with metal compounds. In this paper, we focused on the application of raw lacquer in the synthesis of anisotropic Janus composite particles based on urushiol-iron/polystyrene polymer. The surface of polystyrene (PS) microspheres formed rich sulfonic groups after being sulfonated with concentrated sulfuric acid, which easily absorb Fe3+. Urushiol reacted with Fe3+ forming the urushiol-iron (UFe) coordination compound, and then generated UFe/PS core–shell composite microspheres. After swelling polymerization with 2-propenoic acid, 2-methyl-, 3-(trimethoxysilyl) propyl ester (MPS), the asymmetric Janus composite particles of UFe–PMPS were obtained. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), infrared spectroscopy (IR), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) were used to explore the structure and composition of the UFe/PS core–shell composite microspheres and the UFe–PMPS Janus composite particles. Results showed that UFe/PS core–shell composite microspheres with different thickness of UFe shell could be obtained by adjusting the sulfonated time. After UFe/PS with appropriate thickness of UFe shell swelled with MPS and was polymerized, dumbbell-like UFe–PMPS Janus composite particles were prepared successfully. The UFe–PMPS Janus composite particles were compartmentalized two parts with different morphology. The anisotropic Janus composite particles of UFe–PMPS will be expected to have application in functional materials or oriental coatings.

Study on Preparation and Property of Phenolic-SiO2 Core-shell Composite Hollow Microspheres

The great advantage of hollow SiO2 microspheres is low density and high-temperature resistance, however, the toughness and wear-resisting property is poor, so it can’t be used in the condition of mechanical friction and high-speed shearing. Therefore, phenolic-SiO2 core-shell composite hollow microspheres were prepared by spray coating process, and the properties were measured. The results indicate that the core-shell composite hollow microspheres not only have low density and high-temperature resistance, but also have good toughness and wear-resisting property. The compressive strength was 50MPa. The density was 0.54-0.65g/cm3. Temperature resistance was 120 oC. Grain diameter was 2∼300μm and the percentage of damage on the condition of grinding for 16h was very low. Phenolic-SiO2 core-shell composite hollow microspheres have good prospect in the field of the development of oil gas and spaceflight.

Gel-assisted synthesis of oleate-modified Fe3O4@Ag composite microspheres as magnetic SERS probe for thiram detection

Fast detection and identification of thiram, a kind of well-known pesticide, presents a great challenge to environmental researchers. This work developed a kind of oleate-modified Fe3O4@Ag core@shell composite microsphere as a magnetic separable SERS substrate for quick selective sensing of thiram. In the synthesis procedure, the bulk gel containing oleate was used as the reaction system, which not only avoided the aggregation of Fe3O4 microspheres by fixing them during silver coating, but also modified the silver shell with oleate groups simultaneously. Through serial experiments, the silver seeds on the surface of the Fe3O4 microspheres were found to influence the shell growth strongly, and the Fe3O4@Ag core@shell composite microspheres could only be obtained when the Fe3O4 microspheres with dense silver seeds were used as the template. The surface capped oleate groups and the inner magnetic core made the as-obtained Fe3O4@Ag core shell composite microsphere a highly efficient SERS substrate for fast and selective monitoring of thiram in solution, and the well-coated Fe3O4@Ag core@shell composite microspheres exhibited excellent selective probing performance for thiram with a detection limit as low as 10−8 M.