to prepare Fe3O4 , NH4 Fe(SO4) 2 ·12H2O (8.35 g) and (NH4)2Fe(SO4)2·6H2O(3.40
g) were dissolved in 400mL water at 50 °C to synthesize iron oxides under a N2 atmosphere. Then, the iron oxides were precipitated with 20 mL NH3·H2O
(8 mol/L). The mixed solution was sonicated (200W, 40kHz) for 10 min. After
that, the final mixture was adjusted to pH11. The reaction was allowed to
proceed at 50 °C and stirred for 1 h. The precipitate was separated by an
external magnetic field and washed with double-distilled water to pH7. Next,
1.7mL PVP (25.6 g/L) was added to the mixture that the obtained precipitate was
dispersed in 20 mL water. The mixture was stirred vigorously at room
temperature for 1 day. The Fe3O4 microspheres were
gathered by an external magnetic field, which were washed with water and
ethanol, respectively. The product was dried at 25 °C.
ethanol/water (4:1, v/v), 1.4g Fe3O4 microspheres were
dispersed and 5 mL NH3·H2O was stirred at30 °C for 15
min. Four-milliliter TEOS was added in the dispersion, and the mixture was
stirred at 25 °C for 8 h. The product was magnetically separated and rinsed
three times with ethanol. The obtained Fe3O4@SiO2 was dispersed in 140 mL isopropanol.
40-mL Fe3O4@SiO2 solution which was diluted
with 100 mL isopropanol, 0.2 mL APTES was added. The mixture was sonicated (200
W, 40 kHz) for 30 min under a N2 atmosphere and kept stirring at 70
°C for 6 h to obtain Fe3O4@SiO2-NH2.
Finally, the products were washed with water and ethanol, respectively, and
dried under vacuum.
mL of DMF, 0.2g GO was dispersed with the aid of ultrasonication. Then, 0.1g of
NHS and 0.2 g of EDC were added to the dispersion. The mixture was stirred
vigorously for 2 h at room temperature. Next, 0.5g Fe3O4@SiO2-NH2 was added to the mixture. The mixed solution was stirred overnight at room
temperature. The products were washed with water and air-dried for further use.Composite
materials of graphene oxide (GO) to Fe3O4@SiO2-NH2 (Fe3O4@SiO2@GO) were prepared .
synthesized by hydrazine reduction of the Fe3O4@SiO2@GO,
and 0.2 g Fe3O4@SiO2@GO was dissolved in 100
mL water. Then, 200 μL hydrazine (85 %) was added to the mixture, and the
reaction was churned for 2h at 95 °C. Finally, the polymers were washed
thoroughly with water and dried at 80 °C.