Magnetic nanomaterials in catalysis: advanced catalysts for magnetic separation and beyond

The simultaneous entrapment of biological macromolecules and nanostructured silica-coated magnetite in sol-gel materials using a reverse-micelle technique leads to a bioactive, mechanically stable, nanometer-sized, and magnetically separable particles. These spherical particles have a typical diameter of 53 +/- 4 nm, a large surface area of 330 m(2)/g, an average pore diameter of 1.5 nm, a total pore volume of 1.427 cm(3)/g and a saturated magnetization (M(S)) of 3.2 emu/g. Peroxidase entrapped in these particles shows Michaelis-Mentan kinetics and high activity. The catalytic reaction will take place immediately after adding these particles to the reaction solution. These enzyme entrapping particles catalysts can be easily separated from the reaction mixture by simply using an external magnetic field. Experiments have proved that these catalysts have a long-term stability toward temperature and pH change, as compared to free enzyme molecules. To further prove the application of this novel magnetic biomaterial in analytical chemistry, a magnetic-separation immunoassay system was also developed for the quantitative determination of gentamicin. The calibration for gentamicin has a working range of 200-4000 ng/mL, with a detection limit of 160 ng/mL, which is close to that of the fluorescent polarization immunoassay (FPIA) using the same reactants.

Magnetite-containing spherical silica nanoparticles for biocatalysis and bioseparations （vol 76, pg 1316, 2004）

Microreactors offer excellent mass and heat transfer performance for extraction and multiphase reactions. They provide a powerful tool for process intensification and micro scale processing. This paper reviews the structures of microreactors and units, and their applications on the synthesis of nanoparticles, organics, polymers and biosubstances. The structural evolution and properties of the commercialized and lab-made microreactors are introduced in detail. Recent developments of the fabrication, structures and applications of micro-structured reactors are highlighted. The promising direction in science and technology for future microreaction technology is also discussed.

Review of the applications of microreactors

A dual function magnetic nanomaterial modified with lysine for removal of organic dyes from water solution

Growth of poly(2-hydroxyethyl methacrylate) brushes on magnetic nanoparticles and subsequent brush functionalization with nitrilotriacetate-Ni2+ yield magnetic beads that selectively capture polyhistidine-tagged (His-tagged) protein directly from cell extracts. Transmission electron microscopy, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis, and magnetization measurements confirm and quantify the formation of the brushes on magnetic particles, and multilayer protein adsorption to these brushes results in binding capacities (220 mg BSA/g of beads and 245 mg His-tagged ubiquitin/g of beads) that are an order of magnitude greater than those of commercial magnetic beads. Moreover, the functionalized beads selectively capture His-tagged protein within 5 min. The high binding capacity and protein purity along with efficient protein capture in a short incubation time make brush-modified particles attractive for purification of recombinant proteins.

Polymer Brush-Modified Magnetic Nanoparticles for His-Tagged Protein Purification

Immobilized-metal affinity chromatography adsorbent with paramagnetism and its application in purification of histidine-tagged proteins

Nano-magnetic particles as multifunctional microreactor for deep desulfurization.

Polyacrylamide (PAM) microhydrogels supported with hexadecyltrimethylammonium (CTAB)–peroxotungstophosphate (PTP) complexes were synthesized and characterized using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), energy-dispersive X-ray spectrophotometer (EDX), and element-distribution map (EDM). The results indicate that a CTAB–PTP/PAM composite microsphere with surface-wrinkle morphology and a PAM microgel core/CTAB–PTP shell structure were obtained. The surface-wrinkle structure changed with the amount of CTAB–PTP supported on the PAM microgels. The CTAB–PTP/PAM composite microspheres may find applications as reused catalytic material in diphase catalysis based on the oxidation of dibenzothiophene (DBT) with hydrogen peroxide, and the composite microspheres can be recycled three times with a small decrease in activity.

Microhydrogel surface-supported quaternary ammonium peroxotungstophosphate as reusable catalytic materials for oxidation of DBT

Surfmer [3-(acryloylamino)propyl]dodecyldimethyl ammonium bromide (APDDAB) was synthesized and characterized. On the basis of the reverse emulsion polymerization technique, poly[acrylamide-co-3-(acryloylamino)propyldodecyldimethylammonium bromide] [P(AM-co-APDDAB)] copolymer microgels were obtained with the copolymerization of acrylamide and APDDAB. The P(AM-co-APDDAB)/polyoxotungstates composite microspheres were prepared with the ion-exchange reaction of the P(AM-co-APDDAB) microgels with phosphotungstic acid (H3PW12O40). The morphologies and components of the composite microspheres were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The results indicate that the P(AM-co-APDDAB)/PW12O40 composite microspheres all had a core–shell structure. For the composite microspheres, the hydrogel P(AM-co-APDDAB) was dominantly located in the core, and the complexes of PW12O403− with APDDAB were mainly located in the surface; these features made the composite microspheres amphiphilic and provided for potential catalysis in a two-phase reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Preparation and characterization of poly[acrylamide-co-3-(acryloylamino)propyldodecyldimethylammonium bromide]/polyoxometalate composite microspheres

The invention provides a method for preparing core-shell microgel composite microspheres by adopting a polymerizable surfactant, which comprises the process steps as follows: preparing an oil phase, preparing a homogeneously dispersed oil phase, preparing a water phase, preparing a microgel, preparing a swollen microgel, preparing a porous microgel, preparing a porous microgel containing a polymerizable surfactant acrylamide-propyl-dodecyl-dimethyl-ammonium bromide, and preparing the microgel composite microspheres. The method has the advantages of reasonable design, feasible process, simple operation, reaction under the normal temperature, etc. The microgel composite microspheres prepared by adopting the method is characterized by core-shell structure, larger size which facilitates separation, large specific surface, reversible swelling and deswelling, and has phosphotungstic acid on the surface, thus the core-shell microgel composite microspheres can be popularized and applied in the fields of structural catalyst preparation, rapid enrichment, separation, etc.

Xinai Cui

Papers

Immobilized-metal affinity chromatography adsorbent with paramagnetism and its application in purification of histidine-tagged proteins

Nano-magnetic particles as multifunctional microreactor for deep desulfurization.

Microhydrogel surface-supported quaternary ammonium peroxotungstophosphate as reusable catalytic materials for oxidation of DBT

Preparation and characterization of poly[acrylamide-co-3-(acryloylamino)propyldodecyldimethylammonium bromide]/polyoxometalate composite microspheres

Method for preparing nucleocapsid type microgel composite microsphere using polymerisable surfactant