Synthesis Of Silica-coated Magnetic Nanoparticles Research Articles

Green synthesis of silica-coated magnetic nanocarriers for simultaneous purification-immobilization of β-1,3-xylanase

Tailoring magnetic nanocarriers with tunable properties is of great significance for the development of multifunctional candidate materials in numerous fields. Herein, we report a one-pot biomimetic silicification-based method for the synthesis of silica-coated magnetic nanoparticles. The synthesis process was mild, low cost, and highly efficient, which took only about 21 min compared with 4.5–120 h in other literature. Then, the carriers had been characterized by VSM, SEM, TEM, XRD, FT-IR, and EDS to confirm their function. To evaluate the usefulness of the carriers, they were adopted to couple the purification and immobilization of β-1,3-xylanase from the cell lysate in a single step with high immobilization yield (92.8 %) and high activity recovery (82.4 %). The immobilized enzyme also retained 58.4 % of the initial activity after 10 cycles and displayed good storage properties, and improved thermal stability, which would be promising in algae biomass bioconversion as well as other diverse applications.

Novel synthesis of silica-coated magnetic nano-particles based on acidic ionic liquid, as a highly efficient catalyst for three component system leads to furans derivatives

In this work, thiocarbohydrazide doped iron nanoparticles as a novel, green, heterogeneous, and inexpensive catalyst is reported. This catalyzed the three components reaction of dialkylacetylenedicarboxylate with aromatic aldehydes and aromatic amines to yield the corresponding furan derivatives EtOH. An indispensable part of green chemistry is to be able to recover and reuse catalysts without any notable drop in catalytic activity. The analysis of catalyst and application of that for the synthesis of title compounds in high yields reveal this property. The formation, size of the metal ions present in the material is confirmed by powdered X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA).

Submicron silica shell–magnetic core preparation and characterization

The magnetic extraction, purification, labeling and detection of biomolecules and cells are widely applied recently. In addition, the synthesis of silica magnetic particles for biomedical applications has been developed. In this paper, the synthesis of silica-coated magnetic nanoparticles was performed through three steps. First, an organic ferrofluid was prepared by the coprecipitation technique. Then it was used to prepare the magnetic emulsion. Finally, the hydrophobic magnetic nanoparticles were coated by silica shell using the sol-gel process. The prepared particles during the three steps were characterized in term of morphology, chemical composition and magnetic behavior under magnetic field. The results confirmed the formation of silica-coated magnetic nanoparticles, which are superparamagnetic even after silica encapsulation. The particles size was adjusted in order that a magnetic field can easily separate the particles at the same time they are stable colloids. Obtained particles can be used to extract and purified the nucleic acids, immobilized the enzymes, proteins and antibodies or to label the bacteria cells.

Formulation of Laccase Nanobiocatalysts Based on Ionic and Covalent Interactions for the Enhanced Oxidation of Phenolic Compounds

Oxidative biocatalysis by laccase arises as a promising alternative in the development of advanced oxidation processes for the removal of xenobiotics. The aim of this work is to develop various types of nanobiocatalysts based on laccase immobilized on different superparamagnetic and non-magnetic nanoparticles to improve the stability of the biocatalysts. Several techniques of enzyme immobilization were evaluated based on ionic exchange and covalent bonding. The highest yields of laccase immobilization were achieved for the covalent laccase nanoconjugates of silica-coated magnetic nanoparticles (2.66 U mg−1 NPs), formed by the covalent attachment of the enzyme between the aldehyde groups of the glutaraldehyde-functionalized nanoparticle and the amino groups of the enzyme. Moreover, its application in the biotransformation of phenol as a model recalcitrant compound was tested at different pH and successfully achieved at pH 6 for 24 h. A sequential batch operation was carried out, with complete recovery of the nanobiocatalyst and minimal deactivation of the enzyme after four cycles of phenol oxidation. The major drawback associated with the use of the nanoparticles relies on the energy consumption required for their production and the use of chemicals, that account for a major contribution in the normalized index of 5.28 × 10−3. The reduction of cyclohexane (used in the synthesis of silica-coated magnetic nanoparticles) led to a significant lower index (3.62 × 10−3); however, the immobilization was negatively affected, which discouraged this alternative.

Synthesis of Silica-Coated Magnetic Nanoparticles Using Acid Catalysis

Synthesis of Silica-Coated Magnetic Nanoparticles Using Acid Catalysis

The synthesis of silica-coated magnetic nanoparticles and using as adsorbent

In this work, the silica-coated magnetic field-sensitive iron nanoparticles (Si-γFe2O3) were successfully prepared by sol–gel method and used as the adsorbent in the adsorption of methylene blue. The adsorption capacity was evaluated. Batch adsorption experiments were performed as a function of contact time, initial dye concentration (5–20 mg/L), solution pH (4.0–9.6) and temperature (298–328 K). The structure and the morphology of this material were characterized by the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The adsorption kinetic studies were achieved using pseudo-first order, and pseudo-second order kinetic models. The adsorption kinetic of methylene blue on Si-γFe2O3 is consistent with the pseudo-second order kinetic model. Thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) changes were evaluated and the results indicated that adsorption process was endothermic and spontaneous. The equilibrium isotherms for the adsorption of methylene blue on the adsorbent were described by the Freundlich and Langmuir isotherm models.

Synthesis of Silica-Coated Magnetic Nanoparticles and Application in the Detection of Pathogenic Viruses

Magnetic Fe3O4nanoparticles were prepared by coprecipitation and then coated with silica. These Fe3O4/SiO2nanoparticles consisted of a 10–15 nm magnetic core and a silica shell of 2–5 nm thickness. The superparamagnetic property of the Fe3O4/SiO2particles with the magnetization of 42.5 emu/g was confirmed by vibrating sample magnetometer (VSM). We further optimized buffers with these Fe3O4/SiO2nanoparticles to isolate genomic DNA of hepatitis virus type B (HBV) and of Epstein-Barr virus (EBV) for detection of the viruses based on polymerase chain reaction (PCR) amplification of a 434 bp fragment ofSgene specific for HBV and 250 bp fragment of nuclear antigen encoding gene specific for EBV. The purification efficiency of DNA of both HBV and EBV using obtained Fe3O4/SiO2nanoparticles was superior to that obtained with commercialized Fe3O4/SiO2microparticles, as indicated by (i) brighter PCR-amplified bands for both HBV and EBV and (ii) higher sensitivity in PCR-based detection of EBV load (copies/mL). The time required for DNA isolation using Fe3O4/SiO2nanoparticles was significantly reduced as the particles were attracted to magnets more quickly (15–20 s) than the commercialized microparticles (2-3 min).

Applications of magnetic targeting in diagnosis and therapy--possibilities and limitations: a mini-review.

Applications of magnetic targeting in diagnosis and therapy--possibilities and limitations: a mini-review.