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Facile synthesis of a novel dendritic nanostructure of Fe3O4-Au nanorods
Materials Science and Engineering B 175 (2010) 172–175
Contents lists available at ScienceDirect
Materials Science and Engineering B journal homepage: www.elsevier.com/locate/mseb
Facile synthesis of a novel dendritic nanostructure of Fe3 O4 -Au nanorods Sui-Yi Zhu, Lei-Lei Zhang, Qi Yu, Tian-Zhu Wang, Jing Chen, Ming-Xin Huo ∗ Department of Environmental Science and Engineering, Northeast Normal University, Changchun 130024, China
a r t i c l e
i n f o
Article history: Received 12 April 2010 Received in revised form 2 July 2010 Accepted 9 July 2010 Keywords: Gold Iron oxide Nanostructure Near-infrared Superparamagnetism
a b s t r a c t A novel dendritic nanostructure of Fe3 O4 -Au nanorods (SPIONs-AuNRs) has been fabricated by a facile route. The dendritic SPIONs-AuNRs show a mean particle size of 35 nm, the intense near-infrared (NIR) absorbance at 754 nm and the strong superparamagnetism, implying the potential applications in the fields of the optical/magnetic-resonance bimodal imaging and the photothermal/magnetothermal combined therapy, the low temperature catalysis and the magnetic separation. © 2010 Published by Elsevier B.V.
1. Introduction Bimodal imaging and multifunctional therapy with optical/magnetic nanostructure materials have received increasing attention [1–8]. The superparamagnetic iron oxide nanoparticles (SPIONs) with the particle size of about 12 nm have been proved to be of the optimal mass magnetization values [9,10]. Multifunctional SPIONs have been designed as magnetic-resonance imaging contrast agents to detect cancer cells and tissues [9–12]. In addition, new opportunities in both cellular optical imaging and therapy in intact tissues have been spawned by nanoparticles, such as gold nanoshells, nanorods, nanocages and so on, with absorbances 106 -fold more than that of organic dyes [2,4,7,13]. For these nanoparticle geometries, the surface plasmon resonance (SPR) peak of gold shifts to the near-infrared (NIR) region (700–850 nm) where the absorbances of soft tissue, hemoglobin and water absorb are weak, compared with spherical solid gold nanoparticles. Furthermore, combining SPIONs with gold nanorods (AuNRs), an optical/magnetic bimodal imaging would further provide richer anatomic information at the multi-levels of molecule, cell and tissue, and the photothermal/magnetothermal multifunction would favor advancing the therapy strategy [1,2,8]. Moreover, the conjoint nanostructure of SPIONs and AuNRs could catalyze the oxidation of CO and VOCs at the relatively low temperature, and could be easily separated via the magnetic field [14,15].
∗ Corresponding author at: Department of Environmental Science and Engineering, Northeast Normal University, 5268 Ren-Min Street, Changchun 130024, China. Tel.: +86 0431 85099169; fax: +86 0431 85099169. E-mail address: [email protected] (M.-X. Huo). 0921-5107/$ – see front matter © 2010 Published by Elsevier B.V. doi:10.1016/j.mseb.2010.07.024
However, a major challenge is how to fabricate the nanostructure of smaller than 50 nm integrating SPIONs with AuNRs and simultaneously maintain excellent multifunctional features of NIR absorbance and superparamagnetism. Herein, we demonstrate a novel dendritic nanostructure of Fe3 O4 -Au nanorods (SPIONsAuNRs) and their self-assembly route. As far as we know, this novel dendritic nanostructure of SPIONs-AuNRs with the particle size of 35 nm was rarely reported. 2. Material and methods 2.1. Synthesis and amine modification of SPIONs The SPIONs were synthesized following the procedure proposed by Hyeon and co-workers [16,17]. In a typical experiment for ∼12 nm SPIONs, iron-oleate (5.4 g, 6 mmol) was dissolved in 1octadecene (40 mL) together with oleic acid (12 mmol). The mixture was first heated to 80 ◦ C to accelerate the dissolution of solid ironoleate, and then heated to 120 ◦ C under a nitrogen atmosphere and maintained at this temperature for 2 h to get rid of air and water in the system. The reaction mixture was directly heated to 320 ◦ C and kept for 2 h. The obtained black-brown suspension was cooled to room temperature, washed with hexane and ethanol, and collected by the magnetic separation. The final product could be easily re-dispersed into toluene or other non-polar solvents. To provide heterogeneous nucleation positions for AuNRs, the SPIONs were modified with amine groups. In a typical experiment, the SPIONs were dispersed into water-free toluene followed by refluxing. Then the methanol solution of N-[N -(2aminoethyl)aminoethyl]-3-aminopropyl-methyldimethoxysilane (DETA-MDMS) was added dropwise under vigorously stirring. After
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173
Fig. 1. Low-magnification and high-magnification TEM images of SPIONs (a) and (b), and SPIONs-NH2 (c) and (d).
24 h, the amine-modified SPIONs (SPIONs-NH2 ) were collected by centrifuge at 20,000 rpm for 10 min on a GL-23 M high-speed refrigerated centrifuge (XiangYi Centrifuge Instrument Co., Ltd.), washed for several times with excessive ethanol, and re-dispersed into water by ultrasonic dispersion.
powder form by evaporating the water from the solution. The background magnetic moments from the sample capsules (container) were found to be negligible (∼10−5 emu). UV–vis–NIR absorbance spectrum of SPIONs-AuNRs was recorded on a Shimadzu UV3101PC Spectrophotometer with quartz cuvettes of 10-mm optical path length.
2.2. Synthesis of SPIONs-AuNRs 20 L of 10 mM HAuCl4 aqueous solution and 100 L of 5 mM ascorbic acid aqueous solution were added to 10 mL aminemodified SPIONs solution at 4 ◦ C in turn. This addition procedure was repeated for four times at intervals of 30 min. A gradual change in color from yellow to dark brown occurred during the five additions. After 24 h, the SPIONs-AuNRs was collected by the magnetic separation, washed for several times with excessive ethanol, and re-dispersed into ethanol by ultrasonic dispersion and stored at 4 ◦ C. 2.3. Characterization of SPIONs-AuNRs The morphology, component and structure of SPIONs and SPIONs-AuNRs were characterized via transmission electron microscopy (TEM), energy-dispersive spectra (EDS) and X-ray diffraction (XRD). TEM and EDS images were obtained on a JEM2010 electron microscope attached with an Oxford Link ISIS energy-dispersive spectrometer operating at an accelerating voltage of 200 kV. XRD data were recorded on Rigaku D/Max-2550 V diffractometer using Cu K␣ radiation (40 kV and 40 mA) at a scanning rate of 0.4◦ /min over the range of 30–80◦ . Magnetization measurements were carried at 300 K in a magnetic field (H) of up to 5 kOe with a superconducting quantum-interference device magnetometer (model MPMS, Quantum Design, San Diego, USA) that can measure magnetic moments as low as 10−7 emu. For the magnetization measurements, the SPIONs-AuNRs was prepared in a dry
3. Results and discussion As shown by TEM images in Fig. 1, both SPIONs and SPIONsNH2 have an average particle size of 12 nm and good dispersivity. Some surface defects of SPIONs and SPIONs-NH2 are clearly visible from high-magnification TEM images, as shown in Fig. 2c and d. After introducing Au resource, a dendritic nanostructure with a mean particle size of 35 nm is exhibited of the SPIONs-AuNRs, as shown in Fig. 2a. Several AuNRs radiate along different directions, as directed by white arrows in Fig. 2b. Almost all AuNRs selectively grow along the [1 1 1] direction, and the most prevalent lattice spacing of the (1 1 1) plane of the AuNRs is found to be 0.23 nm in Fig. 2c and d. It is possible that the SPIONs are embodied within the dendritic nanostructure or interconnect with the AuNRs because the SPIONs-AuNRs have been collected by the magnetic separation and Fe and Au elements coexist in the SPIONs-AuNRs at the Au/Fe molar ratio of 2.1 according to the EDS elementary analysis (Fig. 2b). The SPIONs are not clearly visible from TEM imaging, most probably because they have been thickly coated by AuNRs and their electron density is lower than AuNRs. It is notable that amine groups were smartly grafted on the surface of SPIONs as both a chelator of Au ions and a reducer of Au ions to provide both the nucleation positions and the growth drive force for AuNRs, and simultaneously facilitate the selective growth of gold nanoparticles into AuNRs for the remarkably enhanced SPR effect. From Fig. 3a, the XRD pattern of SPIONs matches well with standard reflections of Fe3 O4 (JCPDS No. 65-3107). And after the growth
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Fig. 2. Low-magnification (a), high-magnification (c and d) TEM images and representative elemental mapping (b) of SPIONs-AuNRs.
of AuNRs on the surface of SPIONs, the XRD pattern of SPIONsAuNRs still clearly present the characteristic peaks of SPIONs, as shown by * in Fig. 3b, which could be resulted from the incomplete coverage of Au on the surface of SPIONs [18]. Besides, the XRD pattern of SPIONs-AuNRs also exhibit the characteristic peaks of metallic Au (JCPDS 04-0784), as shown by # in Fig. 3b. An intense and broad NIR absorbance band of SPIONs-AuNRs is centered at 754 nm, as shown in Fig. 4. In addition, there are two much weaker visible absorbance bands at 500–650 nm. This great red shift in the SPR from 532 nm to 754 nm would be attributed to the high aspect ratio of AuNRs and/or the dendritic nanostruc-
ture of SPIONs-AuNRs, because higher aspect ratio of AuNRs would lead to stronger SPR effect and the dendritic nanostructure with the appropriate shell thickness also would enhance the SPR effect as reported previously [19]. The normalized saturation magnetizations of SPIONs and SPIONs-AuNRs at 300 K both were very high, as shown in Fig. 5. Compared with the bare SPIONs (74.5 emu/g Fe3 O4 ), the SPIONsAuNRs have the lower saturation magnetization (23.2 emu/g Fe3 O4 ) because of the relatively low density of the magnetic component with the dendritic nanostructure. For SPIONs single crystals, the saturation magnetization increased with the increase of crystal size from 4 nm to 12 nm, owing to the loss of the surface defects and/or the enhancement of surface magnetism etc. [10,20]. In this work, the AuNRs coating on or interconnection with SPIONs could
Fig. 3. XRD patterns of SPIONs (a) and SPIONs-AuNRs (b).
Fig. 4. UV–vis–NIR absorbance spectrum of SPIONs-AuNRs.
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Acknowledgments This work was financially supported by the Nature Science Foundation of China (50778036) and the Social Development Foundation of Jilin Province (20060405 and 20086035). References
Fig. 5. Normalized SPIONs (a) and SPIONs-AuNRs (b) magnetization per gram of SPIONs vs field strength at 300 K.
decrease the surface defects of SPIONs, and could also provide the heterogenerous nucleation positions for AuNRs and inducing their selective growth. 4. Conclusions In summary, the novel dendritic nanostructure of SPIONsAuNRs with the mean particle size of 35 nm has been successfully synthesized for the first time via using amine-modified SPIONs as the nucleation center of AuNRs by a facile route. The AuNRs coating radiates from SPIONs and selectively grows along the [1 1 1] direction. The SPIONs-AuNRs show the intense NIR absorbance at 754 nm and the high saturation magnetization of 23.2 emu/g Fe3 O4 . The synthesized SPIONs-AuNRs present great potentials for applications in the optical/magnetic-resonance bimodal imaging and the photothermal/magnetothermal combined therapy, especially in medical diagnosis and synchronous therapy.
[1] J. Kim, Y. Piao, T. Hyeon, Chem. Soc. Rev. 38 (2009) 372. [2] C.G. Wang, J. Chen, T. Talavage, J. Irudayaraj, Angew. Chem. Int. Ed. 48 (2009) 2759. [3] T. Nakayama, T.A. Yamamoto, Y.H. Choa1, K. Niihara, J. Mater. Sci. 35 (2000) 3857. [4] T.H. Ji, V.G. Lirtsman, Y. Avny, D. Davidov, Adv. Mater. 13 (2001) 1253. [5] W.L. Shi, H. Zeng, Y. Sahoo, T.Y. Ohulchanskyy, Y. Ding, Z.L. Wang, M. Swihart, P.N. Prasad, Nano Lett. 6 (2006) 875. [6] C. Xu, J. Xie, D. Ho, C. Wang, N. Kohler, E.G. Walsh, J.R. Morgan, Y.E. Chin, S. Sun, Angew. Chem. Int. Ed. 47 (2008) 173. [7] C.L. Fang, K. Qian, J.H. Zhu, S.B. Wang, X.X. Lv, S.H. Yu, Nanotechnology 19 (2008) 125601–125611. [8] X.J. Ji, R.P. Shao, A.M. Elliott, R.J. Stafford, E. Esparza-Coss, J.A. Bankson, G. Liang, Z.P. Luo, K. Park, J.T. Markert, C. Li, J. Phys. Chem. C 111 (2007) 6245. [9] Y.W. Jun, J.W. Seo, A. Cheon, Acc. Chem. Res. 41 (2008) 179. [10] Y.W. Jun, J.H. Lee, J. Cheon, Angew. Chem. Int. Ed. 47 (2008) 5122. [11] A.K. Gupta, M. Gupta, Biomaterials 26 (2005) 3995. [12] S. Laurent, D. Forge, M. Port, A. Roch, C. Robic, L.V. Elst, R.N. Muller, Chem. Rev. 108 (2008) 2064. [13] S.E. Skrabalak, J.Y. Chen, Y.G. Sun, X.M. Lu, L. Au, C.M. Cobley, Y.N. Xia, Acc. Chem. Res. 41 (2008) 1587. [14] B. Qiao, L. Liu, J. Zhang, Y.Q. Deng, J. Catal. 261 (2009) 241. [15] S. Minico, S. Scire, C. Crisafulli, R. Maggiore, S. Galvagno, Appl. Catal. B-Environ. 28 (2000) 245. [16] J. Park, K.J. An, Y.S. Hwang, J.G. Park, H.J. Noh, J.Y. Kim, J.H. Park, N.M. Hwang, T. Hyeon, Nat. Mater. 3 (2004) 891. [17] F. Chen, W.B. Bu, Y. Chen, Y.C. Fan, Q.J. He, M. Zhu, X.H. Liu, L.P. Zhou, S.J. Zhang, W.J. Peng, J.L. Shi, Chem.-Asian J. 4 (2009) 1809. [18] H.L. Liu, J.H. Wu, J.H. Min, J.H. Lee, Y.K. Kim, J. Nanosci. Nanotechnol. 9 (2009) 754. [19] T. Placido, R. Comparelli, F. Giannici, P.D. Cozzoli, G. Capitani, M. Striccoli, A. Agostiano, M.L. Curri, Chem. Mater. 21 (2009) 4192. [20] K.H. Hsu, J.H. Wu, Y.Y. Huang, L.Y. Wang, H.Y. Lee, J.G. Lin, J. Appl. Phys. 97 (2005) 114322.
Contents lists available at ScienceDirect
Materials Science and Engineering B journal homepage: www.elsevier.com/locate/mseb
Facile synthesis of a novel dendritic nanostructure of Fe3 O4 -Au nanorods Sui-Yi Zhu, Lei-Lei Zhang, Qi Yu, Tian-Zhu Wang, Jing Chen, Ming-Xin Huo ∗ Department of Environmental Science and Engineering, Northeast Normal University, Changchun 130024, China
a r t i c l e
i n f o
Article history: Received 12 April 2010 Received in revised form 2 July 2010 Accepted 9 July 2010 Keywords: Gold Iron oxide Nanostructure Near-infrared Superparamagnetism
a b s t r a c t A novel dendritic nanostructure of Fe3 O4 -Au nanorods (SPIONs-AuNRs) has been fabricated by a facile route. The dendritic SPIONs-AuNRs show a mean particle size of 35 nm, the intense near-infrared (NIR) absorbance at 754 nm and the strong superparamagnetism, implying the potential applications in the fields of the optical/magnetic-resonance bimodal imaging and the photothermal/magnetothermal combined therapy, the low temperature catalysis and the magnetic separation. © 2010 Published by Elsevier B.V.
1. Introduction Bimodal imaging and multifunctional therapy with optical/magnetic nanostructure materials have received increasing attention [1–8]. The superparamagnetic iron oxide nanoparticles (SPIONs) with the particle size of about 12 nm have been proved to be of the optimal mass magnetization values [9,10]. Multifunctional SPIONs have been designed as magnetic-resonance imaging contrast agents to detect cancer cells and tissues [9–12]. In addition, new opportunities in both cellular optical imaging and therapy in intact tissues have been spawned by nanoparticles, such as gold nanoshells, nanorods, nanocages and so on, with absorbances 106 -fold more than that of organic dyes [2,4,7,13]. For these nanoparticle geometries, the surface plasmon resonance (SPR) peak of gold shifts to the near-infrared (NIR) region (700–850 nm) where the absorbances of soft tissue, hemoglobin and water absorb are weak, compared with spherical solid gold nanoparticles. Furthermore, combining SPIONs with gold nanorods (AuNRs), an optical/magnetic bimodal imaging would further provide richer anatomic information at the multi-levels of molecule, cell and tissue, and the photothermal/magnetothermal multifunction would favor advancing the therapy strategy [1,2,8]. Moreover, the conjoint nanostructure of SPIONs and AuNRs could catalyze the oxidation of CO and VOCs at the relatively low temperature, and could be easily separated via the magnetic field [14,15].
∗ Corresponding author at: Department of Environmental Science and Engineering, Northeast Normal University, 5268 Ren-Min Street, Changchun 130024, China. Tel.: +86 0431 85099169; fax: +86 0431 85099169. E-mail address: [email protected] (M.-X. Huo). 0921-5107/$ – see front matter © 2010 Published by Elsevier B.V. doi:10.1016/j.mseb.2010.07.024
However, a major challenge is how to fabricate the nanostructure of smaller than 50 nm integrating SPIONs with AuNRs and simultaneously maintain excellent multifunctional features of NIR absorbance and superparamagnetism. Herein, we demonstrate a novel dendritic nanostructure of Fe3 O4 -Au nanorods (SPIONsAuNRs) and their self-assembly route. As far as we know, this novel dendritic nanostructure of SPIONs-AuNRs with the particle size of 35 nm was rarely reported. 2. Material and methods 2.1. Synthesis and amine modification of SPIONs The SPIONs were synthesized following the procedure proposed by Hyeon and co-workers [16,17]. In a typical experiment for ∼12 nm SPIONs, iron-oleate (5.4 g, 6 mmol) was dissolved in 1octadecene (40 mL) together with oleic acid (12 mmol). The mixture was first heated to 80 ◦ C to accelerate the dissolution of solid ironoleate, and then heated to 120 ◦ C under a nitrogen atmosphere and maintained at this temperature for 2 h to get rid of air and water in the system. The reaction mixture was directly heated to 320 ◦ C and kept for 2 h. The obtained black-brown suspension was cooled to room temperature, washed with hexane and ethanol, and collected by the magnetic separation. The final product could be easily re-dispersed into toluene or other non-polar solvents. To provide heterogeneous nucleation positions for AuNRs, the SPIONs were modified with amine groups. In a typical experiment, the SPIONs were dispersed into water-free toluene followed by refluxing. Then the methanol solution of N-[N -(2aminoethyl)aminoethyl]-3-aminopropyl-methyldimethoxysilane (DETA-MDMS) was added dropwise under vigorously stirring. After
S.-Y. Zhu et al. / Materials Science and Engineering B 175 (2010) 172–175
173
Fig. 1. Low-magnification and high-magnification TEM images of SPIONs (a) and (b), and SPIONs-NH2 (c) and (d).
24 h, the amine-modified SPIONs (SPIONs-NH2 ) were collected by centrifuge at 20,000 rpm for 10 min on a GL-23 M high-speed refrigerated centrifuge (XiangYi Centrifuge Instrument Co., Ltd.), washed for several times with excessive ethanol, and re-dispersed into water by ultrasonic dispersion.
powder form by evaporating the water from the solution. The background magnetic moments from the sample capsules (container) were found to be negligible (∼10−5 emu). UV–vis–NIR absorbance spectrum of SPIONs-AuNRs was recorded on a Shimadzu UV3101PC Spectrophotometer with quartz cuvettes of 10-mm optical path length.
2.2. Synthesis of SPIONs-AuNRs 20 L of 10 mM HAuCl4 aqueous solution and 100 L of 5 mM ascorbic acid aqueous solution were added to 10 mL aminemodified SPIONs solution at 4 ◦ C in turn. This addition procedure was repeated for four times at intervals of 30 min. A gradual change in color from yellow to dark brown occurred during the five additions. After 24 h, the SPIONs-AuNRs was collected by the magnetic separation, washed for several times with excessive ethanol, and re-dispersed into ethanol by ultrasonic dispersion and stored at 4 ◦ C. 2.3. Characterization of SPIONs-AuNRs The morphology, component and structure of SPIONs and SPIONs-AuNRs were characterized via transmission electron microscopy (TEM), energy-dispersive spectra (EDS) and X-ray diffraction (XRD). TEM and EDS images were obtained on a JEM2010 electron microscope attached with an Oxford Link ISIS energy-dispersive spectrometer operating at an accelerating voltage of 200 kV. XRD data were recorded on Rigaku D/Max-2550 V diffractometer using Cu K␣ radiation (40 kV and 40 mA) at a scanning rate of 0.4◦ /min over the range of 30–80◦ . Magnetization measurements were carried at 300 K in a magnetic field (H) of up to 5 kOe with a superconducting quantum-interference device magnetometer (model MPMS, Quantum Design, San Diego, USA) that can measure magnetic moments as low as 10−7 emu. For the magnetization measurements, the SPIONs-AuNRs was prepared in a dry
3. Results and discussion As shown by TEM images in Fig. 1, both SPIONs and SPIONsNH2 have an average particle size of 12 nm and good dispersivity. Some surface defects of SPIONs and SPIONs-NH2 are clearly visible from high-magnification TEM images, as shown in Fig. 2c and d. After introducing Au resource, a dendritic nanostructure with a mean particle size of 35 nm is exhibited of the SPIONs-AuNRs, as shown in Fig. 2a. Several AuNRs radiate along different directions, as directed by white arrows in Fig. 2b. Almost all AuNRs selectively grow along the [1 1 1] direction, and the most prevalent lattice spacing of the (1 1 1) plane of the AuNRs is found to be 0.23 nm in Fig. 2c and d. It is possible that the SPIONs are embodied within the dendritic nanostructure or interconnect with the AuNRs because the SPIONs-AuNRs have been collected by the magnetic separation and Fe and Au elements coexist in the SPIONs-AuNRs at the Au/Fe molar ratio of 2.1 according to the EDS elementary analysis (Fig. 2b). The SPIONs are not clearly visible from TEM imaging, most probably because they have been thickly coated by AuNRs and their electron density is lower than AuNRs. It is notable that amine groups were smartly grafted on the surface of SPIONs as both a chelator of Au ions and a reducer of Au ions to provide both the nucleation positions and the growth drive force for AuNRs, and simultaneously facilitate the selective growth of gold nanoparticles into AuNRs for the remarkably enhanced SPR effect. From Fig. 3a, the XRD pattern of SPIONs matches well with standard reflections of Fe3 O4 (JCPDS No. 65-3107). And after the growth
174
S.-Y. Zhu et al. / Materials Science and Engineering B 175 (2010) 172–175
Fig. 2. Low-magnification (a), high-magnification (c and d) TEM images and representative elemental mapping (b) of SPIONs-AuNRs.
of AuNRs on the surface of SPIONs, the XRD pattern of SPIONsAuNRs still clearly present the characteristic peaks of SPIONs, as shown by * in Fig. 3b, which could be resulted from the incomplete coverage of Au on the surface of SPIONs [18]. Besides, the XRD pattern of SPIONs-AuNRs also exhibit the characteristic peaks of metallic Au (JCPDS 04-0784), as shown by # in Fig. 3b. An intense and broad NIR absorbance band of SPIONs-AuNRs is centered at 754 nm, as shown in Fig. 4. In addition, there are two much weaker visible absorbance bands at 500–650 nm. This great red shift in the SPR from 532 nm to 754 nm would be attributed to the high aspect ratio of AuNRs and/or the dendritic nanostruc-
ture of SPIONs-AuNRs, because higher aspect ratio of AuNRs would lead to stronger SPR effect and the dendritic nanostructure with the appropriate shell thickness also would enhance the SPR effect as reported previously [19]. The normalized saturation magnetizations of SPIONs and SPIONs-AuNRs at 300 K both were very high, as shown in Fig. 5. Compared with the bare SPIONs (74.5 emu/g Fe3 O4 ), the SPIONsAuNRs have the lower saturation magnetization (23.2 emu/g Fe3 O4 ) because of the relatively low density of the magnetic component with the dendritic nanostructure. For SPIONs single crystals, the saturation magnetization increased with the increase of crystal size from 4 nm to 12 nm, owing to the loss of the surface defects and/or the enhancement of surface magnetism etc. [10,20]. In this work, the AuNRs coating on or interconnection with SPIONs could
Fig. 3. XRD patterns of SPIONs (a) and SPIONs-AuNRs (b).
Fig. 4. UV–vis–NIR absorbance spectrum of SPIONs-AuNRs.
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Acknowledgments This work was financially supported by the Nature Science Foundation of China (50778036) and the Social Development Foundation of Jilin Province (20060405 and 20086035). References
Fig. 5. Normalized SPIONs (a) and SPIONs-AuNRs (b) magnetization per gram of SPIONs vs field strength at 300 K.
decrease the surface defects of SPIONs, and could also provide the heterogenerous nucleation positions for AuNRs and inducing their selective growth. 4. Conclusions In summary, the novel dendritic nanostructure of SPIONsAuNRs with the mean particle size of 35 nm has been successfully synthesized for the first time via using amine-modified SPIONs as the nucleation center of AuNRs by a facile route. The AuNRs coating radiates from SPIONs and selectively grows along the [1 1 1] direction. The SPIONs-AuNRs show the intense NIR absorbance at 754 nm and the high saturation magnetization of 23.2 emu/g Fe3 O4 . The synthesized SPIONs-AuNRs present great potentials for applications in the optical/magnetic-resonance bimodal imaging and the photothermal/magnetothermal combined therapy, especially in medical diagnosis and synchronous therapy.
[1] J. Kim, Y. Piao, T. Hyeon, Chem. Soc. Rev. 38 (2009) 372. [2] C.G. Wang, J. Chen, T. Talavage, J. Irudayaraj, Angew. Chem. Int. Ed. 48 (2009) 2759. [3] T. Nakayama, T.A. Yamamoto, Y.H. Choa1, K. Niihara, J. Mater. Sci. 35 (2000) 3857. [4] T.H. Ji, V.G. Lirtsman, Y. Avny, D. Davidov, Adv. Mater. 13 (2001) 1253. [5] W.L. Shi, H. Zeng, Y. Sahoo, T.Y. Ohulchanskyy, Y. Ding, Z.L. Wang, M. Swihart, P.N. Prasad, Nano Lett. 6 (2006) 875. [6] C. Xu, J. Xie, D. Ho, C. Wang, N. Kohler, E.G. Walsh, J.R. Morgan, Y.E. Chin, S. Sun, Angew. Chem. Int. Ed. 47 (2008) 173. [7] C.L. Fang, K. Qian, J.H. Zhu, S.B. Wang, X.X. Lv, S.H. Yu, Nanotechnology 19 (2008) 125601–125611. [8] X.J. Ji, R.P. Shao, A.M. Elliott, R.J. Stafford, E. Esparza-Coss, J.A. Bankson, G. Liang, Z.P. Luo, K. Park, J.T. Markert, C. Li, J. Phys. Chem. C 111 (2007) 6245. [9] Y.W. Jun, J.W. Seo, A. Cheon, Acc. Chem. Res. 41 (2008) 179. [10] Y.W. Jun, J.H. Lee, J. Cheon, Angew. Chem. Int. Ed. 47 (2008) 5122. [11] A.K. Gupta, M. Gupta, Biomaterials 26 (2005) 3995. [12] S. Laurent, D. Forge, M. Port, A. Roch, C. Robic, L.V. Elst, R.N. Muller, Chem. Rev. 108 (2008) 2064. [13] S.E. Skrabalak, J.Y. Chen, Y.G. Sun, X.M. Lu, L. Au, C.M. Cobley, Y.N. Xia, Acc. Chem. Res. 41 (2008) 1587. [14] B. Qiao, L. Liu, J. Zhang, Y.Q. Deng, J. Catal. 261 (2009) 241. [15] S. Minico, S. Scire, C. Crisafulli, R. Maggiore, S. Galvagno, Appl. Catal. B-Environ. 28 (2000) 245. [16] J. Park, K.J. An, Y.S. Hwang, J.G. Park, H.J. Noh, J.Y. Kim, J.H. Park, N.M. Hwang, T. Hyeon, Nat. Mater. 3 (2004) 891. [17] F. Chen, W.B. Bu, Y. Chen, Y.C. Fan, Q.J. He, M. Zhu, X.H. Liu, L.P. Zhou, S.J. Zhang, W.J. Peng, J.L. Shi, Chem.-Asian J. 4 (2009) 1809. [18] H.L. Liu, J.H. Wu, J.H. Min, J.H. Lee, Y.K. Kim, J. Nanosci. Nanotechnol. 9 (2009) 754. [19] T. Placido, R. Comparelli, F. Giannici, P.D. Cozzoli, G. Capitani, M. Striccoli, A. Agostiano, M.L. Curri, Chem. Mater. 21 (2009) 4192. [20] K.H. Hsu, J.H. Wu, Y.Y. Huang, L.Y. Wang, H.Y. Lee, J.G. Lin, J. Appl. Phys. 97 (2005) 114322.