br average diameter of nm Fe
average diameter of 10 nm. [email protected] nanoparticles were fabricated by reverse-phase microemulsion method. It is clearly that the core-shell structure nanoparticles consist of SiO2 layer with thickness of about 10 nm, as shown in Fig. 1c. Finally, the amino-modified [email protected] nanoparticles react with HAuCl4•4H2O to obtain FeSiAuO composite nanoparticles. From Fig. 1d, we can observe that Au2O3 nanoparticles dispersed evenly on the SiO2 shell, and FeSiAuO nanoparticles have good monodispersity and small particle size (only 20 nm), which is very beneficial for its application as biomedicine. The EDX test was further carried out. It can be seen from the inset of Fig.1d that FeSiAuO contain three elements of Au, Si and Gd, which also proves the successful synthesis of the core-shell structure. The formation process is schema-tically illustrated in Fig. 1e.
In order to further prove the successful synthesis of the samples, the Fourier transform infrared (FT-IR) spectra of each sample were tested. Fig. 2a shows the FT-IR spectrum of Fe3O4, [email protected], FeSiAuO, FeSiAuO-DOX and FeSiAuO-DOX-PEG. For the Fe3O4 sample, it can be observed that the characteristic Acarbose peak at 585 cm−1, which is derived from the vibration of Fe-O. The peaks at 2853 and 2920 cm−1 are originated from the stretching vibration of CH2 and CH3. The peaks at 1634 and 1409 cm−1 are corresponds to asymmetric vibrationand symmetrical vibration of COO- group, indicating that successful pre-paration of oleic acid coated Fe3O4. As for the sample of [email protected],
Fig. 2. (a) FT-IR spectra of Fe3O4, [email protected], FeSiAuO, FeSiAuO-DOX and FeSiAuO-DOX-PEG. (b) Zeta potentials of as-synthesized nanoparticles at diﬀerent steps, the inset shows colloidal stability of the FeSiAuO-DOX-PEG. (c) UV–Vis spectra of Fe3O4, [email protected] and FeSiAuO. (d) The revolution process of the dissolved O2 concentration in the solution containing FeSiAuO sample upon 560 nm (0.2 W/cm2) laser irradiation with diﬀerent time.
the obvious absorption peak at 1083 cm-1 can be contributed to asym-metric vibration of Si-O-Si, and the peaks at 793 and 464 cm−1 are from the symmetrical vibration of Si-O, demonstrating the success of the coating of SiO2 on the surface of Fe3O4. In addition, the broad ab-sorption peak at 3429 cm−1 is attributed to the −OH group, indicating that a large amount of −OH groups exist on the surface of [email protected] samples, which provide an important prerequisite for the loading of
drug molecules. For FeSiAuO in Fig. 2a, we can observe that the characteristic peak of -NH2 appeared at 1633 cm−1, indicating that the amino group was successfully modified to the surface of sample. After DOX loading, the absorption peaks at 1619 cm−1, 1441 cm−1 and 1211 cm−1 can be associated with the stretching vibration of diﬀerent quinone and ketone groups of DOX, and the absorption bonds at 2844 cm−1 and 2930 cm-1 can be assigned to the stretching vibration of
Fig. 4. (a) The magnetic hysteresis loops of Fe3O4, [email protected] and FeSiAuO, the inset shows separation process of the FeSiAuO nanoparticles by a magnet.
(b) N2 adsorption/desorption isotherm of FeSiAuO, and the pore size distribu-tion curve obtained from the adsorption data (inset).
light induced oxygen generation and aﬀecting the hypoxia micro-environment of the tumor cells for eliminating the drug resistance eﬀect.
the C–H group in DOX, confirming the successful loading of DOX mo-lecules into the FeSiAuO. For conjugation of PEG, compared with spectrum of FeSiAuO-DOX, the peaks at 2870 and 1450 cm−1 are cor-responds to the stretching vibration of C–H and C–O from PEG. The successful modification of Au2O3 can be concluded from the above TEM diagram. Zeta potentials of as-synthesized nanoparticles at diﬀerent steps were tested. As shown in Fig. 2b, the potential of Fe3O4 is + 2 mV. Because the Fe3O4 nanoparticles were stabilized by the oleic acid mo-lecule and the Fe-O band was formed. The COO- groups were faced to the nanoparticles and the alkyl chains were faced to outside. The Fe with stronger electron-withdrawing capacity than H can also induce electron cloud migration of the oleic acid molecule, which may induce the surface of the nanoparticles with alkyl chains to present slight electropositivity. After coating SiO2, the potential of [email protected] is reduced to −5 mV. The main reason for the negative charge is that the surface of the SiO2 contains a large amount of Si−OH groups. After loading Au2O3, the potential of FeSiAuO increases to +7 mV. After loading DOX and modification PEG, the potential of FeSiAuO-DOX-PEG was reduced to +2 mV, indicating that DOX and PEG were successfully modified on the surface of FeSiAuO. In addition, the investigation of colloid stability was also carried out. After FeSiAuO-DOX-PEG dissolved