Types of Nanomaterials and Corresponding Methods of Synthesis - Nanomaterials for Medical Applications - page 53

acetylacetonate [Mn(acac) 2 ]; 1,2-distearoyl- sn -glycero-3-phosphoethanol-
amine- N -[biotinyl(polyethylene glycol)2000], DSPE-PEG(2000)Biotin.
(1) Under a flow of nitrogen gas, mix Fe(acac) 3 (2 mmol), 1,2-hexadecane-
diol (10 mmol), oleic acid (6 mmol), oleyl amine (6 mmol), and benzyl
ether (20 mL) with a magnetic stirrer.
(2) Heat to 200 °C for 2 h.
(3) Under a blanket of nitrogen, heat to reflux at 300 °C for 1 h. This will lead
to a blackish brown mixture.
(4) Remove from heat source and cool the mixture down to RT.
(5) At ambient conditions add 40 mL ethanol.
(6) Centrifuge to separate the black residue.
(7) Dissolve the black product in hexane in the presence of oleic acid
(~0.05 mL) and oleyl amine (~0.05 mL).
(8) Centrifuge at 6000 rpm for 10 min to remove any undispersed residue.
(9) Precipitate the NPs, 6 nm Fe 3 O 4 with ethanol.
(10) Centrifuge at 6000 rpm for 10 min to remove the solvent and re-disperse
in hexane.
The reaction of Fe(acac) 3 with surfactants at high temperature leads to mono-
disperse Fe 3 O 4 NPs. 112 The most important factor to monodispersity of the par-
ticles is to heat the mixture to 200 °C first for 2 h before raising the temperature
to reflux at 265 °C in phenyl ether, or at ~300 °C in benzyl ether, or 310 °C in
1-octadecene. Avoid directly heating the mixture to reflux from RT because this
would result in Fe 3 O 4 NPs with a wide size distribution from 4 to 20 nm, which
indicates that the formation of Fe-based nuclei at these reaction conditions is
not a fast process. 112 The 2 mmol Fe(acac) 3 with 6 mmol of oleic acid, 6 mmol
of oleylamine, and 10 mmol of 1,2-hexadecanediol reaction in 20 mL benzyl
ether produced 6 nm Fe 3 O 4 NPs while when phenyl ether (or 1-octadecene)
was used as a solvent, 4 nm (or ~12 nm) Fe 3 O 4 NPs were formed. Because
the boiling point of 1-octadecene (310 °C) or benzyl ether (298 °C) is higher
than that of phenyl ether (259 °C), the larger size of Fe 3 O 4 NPs obtained from
benzyl ether (or 1-octadecene) solution indicates that high reaction temperature
facilitates the formation of large particles.
2.2.6.1.2 Method for 5 nm CoFe 2 O 4 NP Synthesis 112
(1) Mix Co(acac) 2 (1 mmol), Fe(acac) 3 (2 mmol), 1,2-hexadecanediol
(10 mmol), oleic acid (6 mmol), oleyl amine (6 mmol), and benzyl ether
(20 mL) with a magnetic stirrer under a flow of nitrogen.
(2) Heat the mixture to 200 °C for 2 h.
(3) Under a blanket of nitrogen, heat to reflux at ~300 °C for 1 h.
(4) Remove from heat source and cool the black mixture down to RT.
(5) Repeat steps 5-10 in the methods for Fe 3 O 4 .
(6) A black-brown hexane dispersion of 5 nm CoFe 2 O 4 NPs is produced.