Xiangjie Li

Synthesis of BSA/Fe3O4 magnetic composite microspheres for adsorption of antibiotics

BSA/Fe3O4 magnetic composite microspheres with high saturation magnetization and paramagnetic property were prepared via inverse emulsion technology at room temperature, bovine serum albumin (BSA, 60 KD), magnetic nanoparticles (Fe3O4) and glutaraldehyde as macromonomer, inorganic particles and cross-linking agent, respectively. Fourier transform infrared (FTIR), scanning electron microscope (SEM), metalloscope, and particle size analyzer were used to characterize morphology and structure of composite microspheres. Vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA) were used to test magnetic properties of the synthesized samples, adsorption capacity of microspheres was determined by ultraviolet spectrophotometer (UV). The results showed that BSA/Fe3O4 microspheres were 43 μm with relatively narrow particle size distribution, perfect sphere-shaped morphologies, superparamagnetism with a saturation magnetization of 11 emu/g, and high magnetic content with a value of 57.29%. The main factors influencing properties of microspheres including raw material ratio, the amount of emulsifier and cross-linking agent, agitation speed were investigated and optimized. Furthermore, these microspheres accompanying with high separable and reusable efficient may have great potential application in the field of separation, in particular, removal of antibiotics. Adsorption capacities of the microspheres of four different kinds of antibiotics (erythromycin, streptomycin, tetracycline and chloramphenicol) ranging from 69.35 mg/g to 147.83 mg/g were obtained, and Langmuir isotherm model coincided with equilibrium data than that of the Freundlich model.

Preparation of thermoresponsive Fe3O4/P(acrylic acid–methyl methacrylate–N-isopropylacrylamide) magnetic composite microspheres with controlled shell thickness and its releasing property for phenolphthalein

In this work, Fe3O4/P(acrylic acid-methyl methacrylate-N-isopropylacrylamide) (Fe3O4/P(AA-MMA-NIPAm)) thermoresponsive magnetic composite microspheres have been prepared by controlled radical polymerization in the presence of 1,1-diphenylethene (DPE). The shell thickness of thermosensitive polymer (PNIPAm), which was on the surface of the microspheres, can be controlled by using DPE method. The morphology and thermosensitive properties of the composite microspheres, polymerization mechanism of the shell were characterized by TEM, FTIR, VSM, Laser Particle Sizer, TGA, NMR, and GPC. The microspheres with narrow particle size distribution show high saturation magnetization and superparamagnetism. The thermosensitive properties of the composite microspheres can be adjusted indirectly via controlling the addition amount of monomer (NIPAm) in the second step during controlled radical polymerization. Phenolphthalein was chosen as a model drug to investigate drug release behavior of the thermoresponsive magnetic composite microspheres with different shell thickness. Controlled drug release testing reveals that the release behavior depends on the thickness of polymer on the surface of the microspheres.

Fabrication of PEI grafted Fe3O4/SiO2/P(GMA-co-EGDMA) nanoparticle anchored palladium nanocatalyst and its application in Sonogashira cross-coupling reactions

Novel magnetic Fe3O4/SiO2/P(GMA-co-EGDMA) composite nanoparticles grafted with hyperbranched/linear polyethylenimine ligands were fabricated. Subsequently, nano palladium was effectively anchored on this carrier through complexation between Pd2+ ions and multifunctional organic ligands, then a novel supported Pd nanoparticle catalyst with good dispersion and high loading of Pd nanoparticles was successfully prepared after the following reduction process. Afterwards, the as-prepared supported Pd nanoparticle catalyst was characterized by SEM, TEM, XRD, FTIR, TG and ICP-AES. Ultimately, the catalytic performance of the supported Pd nanoparticle catalyst was investigated by catalysing the Sonogashira cross-coupling reaction between aryl halides and arylacetylene. Research shows that the novel supported Pd nanoparticle catalyst exhibits very superior catalytic activity in catalysing the Sonogashira cross-coupling reaction between aryl halides and arylacetylene, even in the absence of the cocatalyst (CuI), and the side reaction producing the by-product (1,3-diyne) can be inhibited effectively. In addition, this supported Pd nanoparticle catalyst exhibits stable recovery and high catalytic activity, for it can be effectively reused 8 times without obvious loss of catalytic activity. Furthermore, the yields of the target products of the Sonogashira cross-coupling reaction between iodobenzene and phenylacetylene, 3-aminophenylacetylene and 4-(ethynyl)phthalic anhydride can reach approximately 79%, 78% and 95% after this novel supported Pd nanoparticle catalyst has been used eight times, respectively.

Papain/Zn3(PO4)2 hybrid nanoflower: preparation, characterization and its enhanced catalytic activity as an immobilized enzyme

Flower-like papain/Zn3(PO4)2 hybrid materials are synthesized via a facile, rapid and low-cost method in this study. The growth process of the nanoflowers has been studied in detail and a four-step formation mechanism, including coordination, precipitation, self-assembly and size growth, has been clarified. The concentration of papain mainly affects the morphology of the products by regulating the assembly and crystal growth. The enzyme activity of papain/Zn3(PO4)2 hybrid nanoflowers, a novel immobilized enzyme, was calculated by monitoring the hydrolysis reaction of casein. The results show that the catalytic properties of papain immobilized on hybrid nanoflowers are enhanced compared with that of free papain. The as-prepared hybrid nanoflowers exhibited excellent reusability, high thermo stability and long storage life. The results indicate that the well-designed materials have great potential in industrial applications.

Fabrication of a Fe3O4@SiO2@mSiO2-HPG-COOH-Pd(0) supported catalyst and its performance in catalyzing the Suzuki cross-coupling reaction

In this paper, magnetic Fe3O4@SiO2@mSiO2 microspheres with core–shell structure were chosen as a catalyst support, then hyperbranched polyglycerol (HPG) was successfully grafted onto the exterior surface and mesopore wall of this material under the catalysis of isopropanol aluminum. Subsequently, the terminal hydroxyl groups of HPG were successfully transformed into carboxyl groups after modification with succinic anhydride. Ultimately, palladium nanoparticles (Pd NPs) were successfully anchored onto the surface of the aforementioned magnetic Fe3O4@SiO2@mSiO2 microspheres with high density carboxylic HPG, nanocrystallization by the complexation between Pd2+ ions and carboxyl groups and the subsequent reduction, a novel Fe3O4@SiO2@mSiO2-HPG-COOH-Pd(0) supported catalyst was successfully obtained. This novel supported Pd NP catalyst is very conducive to the transference and exchange of each component in the reaction system for the orderly mesoporous opening structure. Furthermore, the introduction of a magnetism nucleus can provide convenient magnetic separation. More importantly, the numerous terminal carboxyl groups on the surface of the magnetic Fe3O4@SiO2@mSiO2 microspheres can provide plenty of sufficient binding sites for Pd NPs, and the unique hyperbranched structure is very conducive to capture uniformly dispersed nanosized palladium and can effectively enhance the catalytic activity and stability. Research indicates that this novel supported Pd NP catalyst not only possesses extremely high Pd NPs loading capacity but also shows remarkable catalytic activity to the Suzuki cross-coupling reaction between aryl halides and phenylboronic acid. Simultaneously, the catalytic activity of this supported catalyst did not show evident loss after being used at least eight times.

Large‐Scale Fabrication of Polymer Microcavities with Adjustable Openings and Surface Roughness Regulated by the Polarity of both Seed Surface and Monomers

Polymer microcavities with adjustable openings and surface roughness are fabricated on a large scale via single-hole poly(glycidyl methacrylate) (PGMA) swelling seed particles. The size of openings of these microcavities can be adjusted by changing the amount of hydrophilic monomer, and the degree of surface roughness is easily regulated relying on the adjustment of the polarity of monomer. Furthermore, the morphology of PGMA/poly(styrene-methacrylic acid) (PGMA/P(S-MAA)) microparticles from microcavity to erythrocyte shape is controlled by the polarity of seed surface. From transmission electron microscopy images of PGMA/P(S-MAA) microparticles, a fresh polymer particle appears in the cavity. To confirm this phenomenon, thermal annealing process in dioxane/water solution is carried out. Considering the flexibility of polymers, the openings and closing of the prepared microparticles are regulated following the increase in volume ratio of dioxane/water. Ball-in-bowl-shaped PGMA/P(S-MAA) microparticles are further presented, which proves secondary nucleation of monomer in the polymerization stage.

Facile fabrication of Fe3O4@PS/PGMA magnetic Janus particles via organic–inorganic dual phase separation

In this study, a facile strategy is developed to fabricate Fe3O4@polystyrene/poly (glycidyl methacrylate) (Fe3O4@PS/PGMA) magnetic Janus particles (MJPs) by solvent evaporation-induced organic–inorganic dual phase separation. The Fe3O4 nanoparticles (MNPs) are selectively dispersed on one side of the particles. The experimental factors on the morphology of Fe3O4@PS/PGMA MJPs, including the addition of MNPs, the ratios of polymer precursors, concentrations of surfactant and emulsification speed, are systematically investigated. The particle size, magnetic content, magnetic performance and morphology of prepared MJPs are determined by laser particle size analyzer, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and microscope. Furthermore, the dual phase separation mechanism of the formation of Fe3O4@PS/PGMA magnetic Janus particles is also explored. Further, the method introduced here supports a simple, controlled procedure to prepare large amounts of magnetic Janus particles under mild conditions.

Micron-sized flower-like Fe3O4@GMA magnetic porous microspheres for lipase immobilization

Flower-like Fe3O4 microspheres prepared by a fast solvothermal method were selected to fabricate micron-sized Fe3O4@glycidyl methacrylate (GMA) magnetic porous microspheres. The magnetic porous microspheres were endowed with appropriate specific surface area (39.54 m2 g−1) and appropriate pore diameter (16 nm), and could serve as a carrier for immobilized lipase. Meanwhile, the prepared magnetic microspheres with high saturation magnetization could realize rapid separations. After those microspheres were aminated and activated, the obtained immobilized lipase possessed high efficiency of immobilization and catalytic activity, with the optimum pH and temperature of 8.0 and 40 °C, respectively. The thermal stability of immobilized lipase was obviously exceeding free lipase.

Bovine serum albumin surface imprinted polymer fabricated by surface grafting copolymerization on zinc oxide rods and its application for protein recognition

A novel bovine serum albumin (BSA) surface imprinted polymer based on ZnO rods was synthesized by surface grafting copolymerization. It exhibited an excellent recognition performance to bovine serum albumin. The adsorption capacity and imprinting factor of bovine serum albumin could reach 89.27 mg/g and 2.35, respectively. Furthermore, the fluorescence property of ZnO was used for tracing the process of protein imprinting and it implied the excellent optical sensing property of this material. More importantly, the hypothesis that the surface charge of carrier could affect the imprinting process was confirmed. That is, ZnO with positive surface charge could not only improve the recognition specificity of binding sites to template proteins (pI < 7), but also deteriorate the bindings between sites and non-template proteins (pI > 7). It was also important that the reusability of ZnO@BSA molecularly imprinted polymers was satisfactory. This implied that the poor mechanical/chemical stability of traditional zinc oxide sensors could be solved by the introduction of surface grafting copolymerization. These results revealed that the ZnO@BSA molecularly imprinted polymers are a promising optical/electrochemical sensor element.

Time-dependent control of phase and morphology transformation of porous ZnO hollow microspheres by a facile one-step solution route

Porous ZnO hollow microspheres with a ZnO crystalline phase of PDF # 21-1486 have been prepared by a simple one-step solution route using the trisodium citrate as a shape-directing agent. FESEM, FT-IR, TEM and XRD were used to characterize the samples. Series of experiments showed the reaction time has a prominent impact on the phase and morphology transformation. At a point of the controlling growth time, porous ZnO hollow microspheres with average diameter of 2–3 μm and hole-opening diameter of ∼0.5 μm were obtained which exhibited a high surface area (117.36 m2 g−1) and a large pore volume (0.50 cm3 g−1). On the basis of experiment results, a possible growth mechanism of as-synthesized porous ZnO hollow microspheres was concluded to be a two-step process: the zinc citrate complexion was preferentially formed, and then the dissolution of zinc citrate complexion and the formation of ZnO crystal occurred simultaneously, which associated with the special role of the citrate anion on oriented growth.