Wen et al.
Preparation of a H PW O Deposited Chitosan Coated Iron Oxide Magnetic Nanocomposite
3 12 40
it can be easily separated due to its high saturation mag-
netization and recycled effectively.
2.3. Activity Test
To a round-bottom flask equipped with a water con-
denser, acetic anhydride (0.54 g, 5 mmol), anisole (1.08 g,
1
0 mmol) and nanocomposite (0.15 g) were added and
2
. EXPERIMENTAL DETAILS
ꢀ
the reaction mixture was stirred at 154 C for 4 h.
When the reaction was completed, the reaction mix-
ture was allowed to cool to room temperature and sep-
arated using a permanent magnet. The products were
analyzed by gas chromatography using a 30-m SE-54
capillary column, and their structures were identified by
gas chromatography–mass spectroscopy (GC-MS) on a
Thermo Finnigan Polaris-Q spectrometer.
2
.1. Preparation of Magnetic Core–Shell
Nanocomposites
Unless otherwise noted, all chemicals were of analyti-
cal reagent grade and used without further purification.
Fe O @CS@HPW was prepared by the following proce-
dure. In brief, CS (0.3 g) was dissolved in acetic acid
solution (0.05 M, 130 mL) under stirring for 30 min, fol-
lowed by adding Fe O nanoparticles (0.75 g). Aqueous
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4
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4
solution of NaOH (1.25 M, 8 mL) was then slowly added
and stirred for another 30 min at room temperature. After
separated by a magnet, the Fe O @CS so obtained was
3
. RESULTS AND DISCUSSION
Textural properties of the magnetic core–shell nanocom-
posites are summarized in Table I. It was found that
Fe O @CS exhibited the highest surface area and pore
volume in the nanocomposites studied. The surface area
and pore volume of Fe O @CS@HPW and Fe O @cl-
CS@HPW decreased markedly after the loading of HPW,
which could be attributed to the occupation of HPW on
the surface and in the pores of the chitosan shell. With
respect to tungsten content, both Fe O @CS@HPW and
Fe O @cl-CS@HPW possessed more tungsten element
compared with Fe O @HPW, which could be ascribed to
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washed with water and ethanol, and then 60 mL aqueous
solution containing HPW (2.0 g) was added, followed by
stirring for 2 h. Finally, Fe O @CS@HPW was collected
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ꢀ
by a magnet, heated at 250 C for 4 h. When HPW was
not used, the product was denoted as Fe O @CS.
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The nanocomposite with a chitosan-crosslinked shell
was prepared by the following procedure and denoted
as Fe O @cl-CS@HPW. CS (0.3 g) was dissolved in
2
6
3
4
3
4
acetic acid solution (0.05 M, 130 mL) under stirring
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for 30 min, followed by adding Fe O4 nanoparticles
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3
abundant complexation sites on the chitosan shell, suggest-
(
0.75 g). Subsequently, 3 mL of aqueous solution con-
IP: 185.46.84.218 On: Wedi ,n 0g 6t hJ eu np o 2s 0i t 1i v 8e 0e 7f f: e3 c4t : 4o f0 chitosan shell on HPW loading.
taining 1,5-pentanedial (0.115 g) was added, followed by
stirring at 60 C for 2 h. Then, HPW (2.0 g) was added
to the resulting mixture and stirred for 2 h. Finally, the
product was collected by a magnet, heated at 250
for 4 h.
ꢀ
Copyright: American S Mc i eo nr et oi f vi ce rP, Fu eb l iOs h @e r Cs S@HPW had a larger content of tung-
3 4
Delivered by Ingenta
sten element than Fe O @cl-CS@HPW, probably due to
the consumption of complexation sites for HPW during
the crosslinking process.
Figure 1 shows XRD patterns of the nanocomposites.
Compared curves d and e with a, the diffraction peaks of
HPW became broader and weaker in the chitosan coated
nanocomposites, indicating that the HPW was highly dis-
persed on the chitosan shell with an amorphous structure.
Furthermore, the characteristic diffractions of the Fe O -
contained nanocomposites (curves b, c, d and e) showed
peaks at 30.1 , 35.4 , 43.1 , 53.8 , 57.0 and 62.5 , which
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ꢀ
C
When Fe O was directly used as the support of HPW,
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the nanocomposite was prepared by the following proce-
dure and denoted as Fe O @HPW. To 25 mL of aqueous
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solution containing HPW (0.6 g), 1.4 g of Fe O nanopar-
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27
ticles was added and stirred for 4 h at room temperature.
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Finally, the product was collected by a magnet, heated at
ꢀ
2
50 C for 4 h.
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ꢀ
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ꢀ
ꢀ
ꢀ
2
8
could be assigned to Fe O cores, suggesting that Fe O
cores retained their magnetite crystalline structures after
the addition of HPW.
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2
.2. Characterization
Brunauer-Emmett-Teller (BET) surface area was estimated
on a Micromeritics Tristar II 3020 surface area and pore
analyzer. X-ray diffraction (XRD) patterns were collected
on a Bruker D8-ADVANCE X-ray diffractometer using Cu
In the FTIR spectrum of Fe O @CS, the character-
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istic peaks of chitosan (mainly at 3440, 2880, 1649,
−1
1
596, 1384, and 1079 cm ꢁ were weakened markedly
ꢀ
ꢀ
Ka radiation and a scan step of 0.02 at 20 C. Trans-
mission electron microscopy (TEM) images were obtained
with a FEI Tecnai G2 F20 S-Twin instrument at a volt-
age of 200 kV. Fourier transform infrared spectroscopy
Table I. Textural properties of the core–shell nanocomposites.
Tungsten
content (%)
Surface area
(m /g)
Pore
volume (cm /g)
a
2
3
Nanocomposite
Fe O @CS
Fe O @cl-CS@HPW
Fe O @CS@HPW
(
FTIR) was carried out on a Bruker Vertex 70 spec-
trophotometer (KBr pellet technique). Inductively coupled
plasma analysis (ICP) was measured on a Varian Vista-
MPX spectrometer. Magnetization curves were obtained
on a LDJ9600-1 Superconducting quantum interference
device.
–
10ꢂ0
1ꢂ7
2ꢂ1
4ꢂ0
0ꢂ022
0ꢂ007
0ꢂ007
0ꢂ011
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36ꢂ1
41ꢂ2
1ꢂ1
3
4
3
4
Fe O @HPW
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Notes: aBased on ICP results.
J. Nanosci. Nanotechnol. 18, 676–680, 2018
677