3. Results and discussion
3.1. Synthesis and characterization of Au-Fe3O4 NPs
The dumbbell-shaped Au-Fe3O4 NPs were synthesized according
to a previously published study [25], and are shown in Fig.
S1 with the diameter of Fe3O4 at around 9 ± 1.7 nm and Au at
13 ± 2.3 nm, respectively. The X-ray diffraction (XRD) patterns
show that the Au and Fe3O4 were preserved in the synthesizing
process (Fig. S2), and the chemical composition (Au and Fe)
were verified by EDX (Fig. S3). The Au-Fe3O4 NPs were modified
by ETC and mPEG-SH to improve the selectivity and dispersity of
Au-Fe3O4 NPs, which was confirmed by FIT-IR (Fig. S4). A new
stretching vibration peak of C O, and C N , located at 1723,
and 1339 cm−1 were the characteristic peaks of ETC and the stretching
vibration peaks of CH2 , C O C were the characteristic
peaks of mPEG-SH, located at 2924 cm−1 and 1090 cm−1. The transmission
electron microscopy (TEM) image showed ETC-Au-Fe3O4
NPs have good property of dispersity (Fig. 1a, inset) with a diameter
of 12.5 ± 2.0 nm for Au NPs. This was also confirmed by dynamic
light scattering (DLS) and the hydrodynamic diameter of ETC-AuFe3O4
NPs is ∼78 nm (Fig. 1a).
The maximum absorbance of ETC-Au-Fe3O4 NPs was observed
at 565 nm, showing a red-shift compared with Au NPs of the same
diameter which showed absorption at ∼524 nm (Fig. 1b). This was due to the charge variation of Au NPs in dumbbell-like structure.
Electric deficiency on the Au particles can shiftthe plasmon absorption
to longer wavelength [26]. The transverse relaxivity (r2) was
calculated as shown in Fig. 1c. The r2 value of ETC-Au-Fe3O4 was
∼105 mM−1 s−1 suggesting that ETC-Au-Fe3O4 could be used as a
T2-shortening agent.
3. Results and discussion3.1. Synthesis and characterization of Au-Fe3O4 NPsThe dumbbell-shaped Au-Fe3O4 NPs were synthesized accordingto a previously published study [25], and are shown in Fig.S1 with the diameter of Fe3O4 at around 9 ± 1.7 nm and Au at13 ± 2.3 nm, respectively. The X-ray diffraction (XRD) patternsshow that the Au and Fe3O4 were preserved in the synthesizingprocess (Fig. S2), and the chemical composition (Au and Fe)were verified by EDX (Fig. S3). The Au-Fe3O4 NPs were modifiedby ETC and mPEG-SH to improve the selectivity and dispersity ofAu-Fe3O4 NPs, which was confirmed by FIT-IR (Fig. S4). A newstretching vibration peak of C O, and C N , located at 1723,and 1339 cm−1 were the characteristic peaks of ETC and the stretchingvibration peaks of CH2 , C O C were the characteristicpeaks of mPEG-SH, located at 2924 cm−1 and 1090 cm−1. The transmissionelectron microscopy (TEM) image showed ETC-Au-Fe3O4NPs have good property of dispersity (Fig. 1a, inset) with a diameterof 12.5 ± 2.0 nm for Au NPs. This was also confirmed by dynamiclight scattering (DLS) and the hydrodynamic diameter of ETC-AuFe3O4NPs is ∼78 nm (Fig. 1a).The maximum absorbance of ETC-Au-Fe3O4 NPs was observedat 565 nm, showing a red-shift compared with Au NPs of the samediameter which showed absorption at ∼524 nm (Fig. 1b). This was due to the charge variation of Au NPs in dumbbell-like structure.Electric deficiency on the Au particles can shiftthe plasmon absorption
to longer wavelength [26]. The transverse relaxivity (r2) was
calculated as shown in Fig. 1c. The r2 value of ETC-Au-Fe3O4 was
∼105 mM−1 s−1 suggesting that ETC-Au-Fe3O4 could be used as a
T2-shortening agent.
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