Magnetic Core/Shell Nanocomposites

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Magnetic Core/Shell Nanocomposites
Mohamed Darwish Institute of Nanomaterials,
Advanced Technology and Innovation Technical
University of Liberec 23/4/2013
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Nanoencapsulation received considerable
increasing attention by providing the possibility
of combining the properties of different material
types (e.g., inorganic and organic) on the
nanometer scale having a spherical or irregular
shape.
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• Capsules can be divided into two parts, namely
  the core and the shell. The core contains the
  active ingredient, while the shell protects the
  core permanently or temporarily from the external
  environment.

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• The protective shell does not only serve to
  protect the magnetic nanoparticles against
  degradation but can also be used for further
  functionalization with specific components, such
  as catalytically active species, various drugs,
  specific binding sites, or other functional
  groups.
• Depending on applications, a wide variety of core
  materials can be encapsulated, including
  pigments, dyes, monomers, catalysts, curing
  agents, flame retardants, plasticizers and
  nanoparticles.
• When the diameter of metal oxide particle acting
  as magnetic core is less than 20 nm, the particle
  has superparamagnetism.

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• Applications of Magnetic Polymer Nanocomposite
• Water treatment application
• Catalysis
• Drug delivery

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• Magnetic polymer composite particles can be
  prepared using various methods.
• The separately performed synthesis of the
  magnetic particles and polymer materials and then
  mixing them.
• In situ precipitation of magnetic material in the
  presence of polymer.
• Monomer polymerization in the presence of the
  magnetite particles to form magnetic polymer
  composite particles.

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Synthesis of iron oxide nanoparticles (NPs)

• Co-precipitation from aqueous Fe (II)/ Fe (III)
  solutions.
• Thermal decomposition of organo-metallic
  compounds
• Hydrothermal synthesis basing on a
  solid-liquid-solution phase
• transfer strategy.
• Sonochemical synthesis

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Synthesis of polymer shell

• Emulsion polymerization
• Dispersion polymerization
• Suspension polymerization
• Microemulsion polymerization
• Miniemulsion polymerization

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Nanocapsules formation in miniemulsion
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Applied methods for magnetic nanocomposites
polymer particles with different functionalities

• Synthesis of magnetic core nanoparticles
• (inorganic reaction by co-precipitation
  process) Fe3O4 Magnetite
• Synthesis of magnetite polyvinylbenzyl chloride
  nanocomposites
• (miniemulsion polymerization )
  (-Cl) group
• Synthesis of bi-layered polymer magnetite by
  coating of magnetite polyvinylbenzyl chloride
  with a hydrophilic layer of polyethylene glycol,
  3-amino-1-propanol, hexamethylenediamine or
  butyl-l, 4-diamine
• (condensation polymerization)
  (-OH) group (-NH2 ) group

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Synthesis of magnetic core nanoparticles by a
co-precipitation process

• Formation step
• Stabilization Step
• By addition of oleic acid at room
  temperature or at higher temperature

Magnetic nanoparticles stabilize by oleate layer
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The average particles size is between 10 nm to 20
nm with superparamagnetic properties
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IR indicates that oleic acid is bonded with iron
oxide Bonding at higher temperature seems to be
stronger
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Prepared at room temperature
Prepared at higher temperature
Sample Magnetite content Fe3O4 Average particles size by TEM Resistance to HCl Dispersion
Magnetite (higher temperature) 60.3 10 nm Seconds hydrophobic properties
The magnetite content is (60) for the
preparation of magnetic nano particles by
co-precipitation process with supermagnetic
properties (10nm diameter) by addition of oleic
acid at higher temperature.
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Preparation of magnetic polyvinylbenzyl chloride
nanoparticles by miniemulsion polymerization
Direct process by formation of a homogeneous
mixture of magnetite, monomer and surfactant by
an US-sonotrode, then direct polymerization by
addition of potassium peroxodisulfate.
This preparation method leads to oleic acid
coated magnetite and a polymer shell with
(-Cl) as functional group
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Sample Magnetite content Fe3O4 Average particles size by TEM Resistance to HCl Dispersion
Magnetic Polyvinylbenzyl chloride nanoparticles 28.6 20 nm Hours hydrophobic properties
The core shell structure formed where the outer
shell is polymer with average particles diameter
ranges from 10 nm to 15 nm
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Polyvinylbenzylchloride coated magnetite
dispersed in acetone and after influence of a
magnetic bar after 3 seconds demonstrating easy
separation by magnetic force
Darwish, M. S., et al., J Poly Research, 2011,
18(1), 79-88
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Auger Electron Spectroscopy (AES) Is an
analytical technique that is used for performing
surface analysis and to determine elemental
composition as a function of depth of a sample.
Layer structure confirmed by auger electron
spectroscopy
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• Bonding situation study of oleic acid (co-monomer
  or mechanical entanglement) in the formation of
  magnetic polyvinylbenzyl chloride
• The bonding situation of oleic acid (co-monomer
  or mechanical entanglement) was studied by IR and
  1H-NMR.

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Magnetic polyvinylbenzyl chloride nanoparticles
based on the performed characterization
Chemically
Mechanical entanglement
Two possible binding situations chemical or
mechanical binding with hydrophobic properties
Darwish, M. S., et al., Journal of Materials
Science, 2011, 46(7), 2123-34
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Bi-layered polymer magnetic core nanoparticles
Bi-layered polymer magnetic core was prepared by
coating of magnetic core hydrophobic polymer
shell composites with a hydrophilic layer of
butyl- l, 4-diamine , hexamethylenediamine or
3-amino-1-propanol by polycondensation
This preparation method leads to oleic acid
coated magnetite and bi-layered polymer shell
with (-OH or -NH2) group as functional group
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Magnetic (III)
Magnetic (II)
Magnetic (I)
The core shell structure formed where average
particles diameter ranges from 20 nm to 50 nm
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bi-layered polymer magnetic core of butyl-l,
4-diamine gives higher in thermal stability
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Dispersion of Bi-layered polymer magnetic core
/shell in water phase

Magnetic (III)
Magnetic (II)
Magnetic (I)

Hydrophilic properties of bi-layered polymer
magnetic core composites
Darwish, M. S., et al., Advanced Materials
Research, 2013, Vols. 622-623, 254-258
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• Magnetic polymer as nano-carriers for enzyme
  immobilization
• There are different property requirements and
  evaluation standards in accordance with different
  target substances and application system.
  Generally, certain parameters about magnetic
  carriers. should be taken into consideration
  magnetic response capability, surface functional
  groups, biocompatibility, the size and its
  distribution of particles.
• As a suitable enzyme for immobilization is
  alcohol dehydrogenase A (ADH-A) and covalent
  immobilization was carried out. The standard
  enzyme buffer is potassium-phosphate-buffer (0.1
  M, pH 7.0) the standard substrate is
  acetophenone, the reaction product is
  phenylethanol. Analysis was carried out using gas
  chromatography.

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• Solubility test of magnetic carriers in Ppb
  (Potassium-phosphate Buffer ) and Toluene
• Some pre-testing of the particles was done to
  make sure the particles are ready for use in the
  enzymatic environment.

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Reaction of the standard-substrate acetophenone
by ADH-A immobilised on magnetic polyvinylaniline
The particles of magnetic polyvinylaniline
with immobilized enzyme ADH-A have been tested
with the standard substrate acetophenone (80 mM)
dissolved in potassium-phosphate-buffer. During
the test the enzyme showed poor activity. The
product concentration didnt show any increase
for the first 50 minutes. However, the final
concentration is at about 18 mM after 270 minutes
which indicate that conversion has taken place
but rather slow.
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Reaction of 2,5-hexandione by ADH-A immobilised
on magnetic polyvinylaniline The concentration
of the substrate 2,5-Hexandione decreased
slightly from 40 mM to 38 mM while the
concentration of the product 2,5-hexandiol didnt
show any changes for the first 100 minutes of
incubation. Only at the end, the sample indicated
an increase of product up to 5mM. The
immobilization results show that immobilization
occurred but in a small extent.
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Batch test 10 mL of amino-linked ADH-A,
production of phenylethanol at 30 C
Batch test 10 mL of EDAC-linked ADH-A to
chloro-magnetic beads, production of
phenylethanol at 30 C
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• Catalytic application
• Metal nanoparticles have attracted a special
  attention due to their use in catalysis. The
  catalytic reactivity depends on size and shape of
  nanoparticles and therefore synthesis of
  controlled shapes and size of colloidal platinum
  particles could be critical for these
  applications. Pt nanoparticles show high activity
  as catalyst in organic synthesis.

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One of the most known methods used for preparing
nanostructred metal particles is the transition
metal salt reduction method. In most methods of
preparation two or four valence platinum are
reduced to zero valence metal atoms with reducing
agent e.g. sodium borohydride (NaBH4). The most
popular procedure is the reduction of H2PtCl6.
Catalytic activity is tried to be added on
polymer support of magnetic polyvinylbenzyl
chloride nanoparticles. Pt is used to form Pt-Fe
nanocomposites for using it as a catalyst for
organic synthesis
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• The polymer supported Pt-catalyst on magnetite
  polyvinylbenzyl chloride nanoparticles gives
  improved in thermal stability which indicates the
  lower amount of polymer included in the sample.
• Atomic absorption spectroscopy was used for the
  determination of Pt metal in the sample. Pt
  loading in polymer-supported Pt catalyst on
  magnetite poly-vinylbenzyl chloride nanoparticles
  was found to be 17 wt .

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Characterization of Pt _at_ magnetic core/shell
nanocomposite
Polymer supported Pt-catalysts on magnetic
core/shell were prepared with fine homogeneous
distribution with an average particle diameter of
5 nm
Darwish, M. S., et al., J. Appl. Polym. Sci.
2012, DOI 10.1002/APP.38864
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Catalysis in reduction reaction of cinnamaldehyde
to cinamylalcohol
The catalytic activity of the catalyst is
increased at high temperature and the reduction
reaction of cinnamaldehyde to cinnamon alcohol is
nearly finished in 15 min.
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• Conclusion and outlook
• Stable magnetic nanoparticles were prepared with
  superparamagnetic properties (lt20 nm) by a
  co-precipitation process.
• The magnetite nanoparticles prepared by addition
  of oleic acid at higher temperature resulted in
  higher stability and also in higher magnetite
  content compared to the samples prepared at room
  temperature.
• Miniemulsion polymerization was successfully used
  in the preparation of magnetic polymer core shell
  nanoparticles functionalized with (-Cl, -NH2 and
  -OH) groups with a diameter range of 20 nm - 50
  nm.
• Bi-layered magnetic core composites show better
  resistance against HCl than magnetite, which
  gives evidence that the magnetic composite has a
  core/shell-structure where the shell protects the
  core.
• The resulting nano-composite particles can be
  used for chemical engineering applications, water
  treatment and for binding enzymes on the
  functionalized surface sites.

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Thanks