High Yield Synthesis of Bracelet-like Hydrophilic Ni-Co Magnetic Alloy Flux-closure Nanorings

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1 Supporting information High Yield Synthesis of Bracelet-like Hydrophilic Ni-Co Magnetic Alloy Flux-closure Nanorings Ming-Jun Hu, Yang Lu, Sen Zhang, Shi-Rui Guo, Bin Lin, Meng Zhang, Shu-Hong Yu* Experimental section Chemicals. The chemicals nickel (II) acetylacetonate (Ni(acac) 2, 95%) and cobalt(ii) acetylacetonate (Co(acac) 2, > 99%) were purchased from Alfa Aesar. Triethylene glycol (TREG), polyvinylpyrrolidone (PVP, M w 40,000), phenol, hexamethyltetramine (HMT), ethyl acetate and ethanol were purchased from the Shanghai Reagent Company (P. R. China). All the chemicals were used as obtained without further purification. Synthesis of Ni-Co nanorings. In a typical procedure, a mixture of analytically pure Co(acac) 2 ( g, mol), Ni(acac) 2 (95%) ( g, mol) and PVP (2.5 g) was added into 15 ml TREG solution. After stirring for half an hour at 135 o C in an oil bath, the transparent solution was quickly transferred into a Teflon lined stainless steel autoclave with a capacity of 22 ml. The autoclave was sealed and maintained in an oven of 240 o C for 3 h, and then naturally cooled to room temperature, a light black solution formed, which was then diluted with 40 ml ethanol and ethyl acetate (volume ratio = 1:3), centrifuged, washed several times with ethanol to remove ions and possible remnants, collected, and vacuum dried for further characterization. Synthesis of Ni-Co@phenol formaldehyde resin nanorings. A light black solution containing alloy nanoparticles prepared by hydrothermal reaction described above was diluted by 30 ml S1

2 ethyl acetate, stirred for 3 mins, and left undisturbed for 5 mins. After that, two-layers of solution will form. The solution in above layer was removed. Then, the solution was washed several times according to such a method until above layer solution becomes clear. The above-layer with transparent ethyl acetate was removed, and some viscous flow was left. Then, a suitable amount of distilled water was added to completely dissolve the viscous flow by stirring. After that, a small amount of distilled water was added to form 26 ml transparent solution. 4 ml 0.1 M phenol solution and 30 mg hexamethyltetramine (HMT) were added into above solution to form 30 ml transparent solution under stirring. The transparent solution was transferred into a 50 ml Teflon lined stainless steel autoclave. The autoclave was sealed in an oven of 160 o C for 4 h. After the solution was cooled to room temperature, the obtained black solid product was collected by magnetic attraction of an external magnet, and then washed with distilled water and absolute ethanol three times respectively for further characterization. Characterization. The samples were characterized by different analytic techniques. X-Ray powder diffraction (XRD) was carried out on a Rigaku D/max-rA X-ray diffractometer with Cu Ka radiation (λ = A ), the morphologies of as-prepared product were observed by scanning electron microscope (SEM, JSM-6700F), transmission electron microscope (TEM, Hitachi H-800). High-resolution transmission electron microscope (HRTEM) photos were performed on a JEOL-2010 transmission electron microscope. Local EDS analysis was performed using a OXFORD INCA system with the smallest analysis spot of 10 nm. The X-ray photoelectron spectra (XPS) were recorded on an ESCALab MKII X-ray photo-electron spectrometer using Mg Ka radiation exciting source. The magnetic properties of Ni 7 Co 3 nanoparticles were investigated using a superconducting quantum interface device (SQUID) S2

3 magnetometer (Quantum Design MPMS XL). MRI imaging. For T 2 -weighted magnetic resonance imaging (MRI) of the Ni 7 Co 3 alloy with a 3 T clinical MRI instrument containing a head coil (Siemens), TSE (Turbo spin echo) sequence was used: TR: 5000 ms, TE: 102 ms. Alloy solution (25 mg/ml) were mixed with different volume 1.5wt% agarose solution to make this concentration gradient. As the concentration of the alloy increases from 0 to 1.25 mg/ml, the signal intensity of the MR image declines, indicating that this alloy have the potential to be used as a T 2 MRI contrast agent. MTT assay analysis. Hela cells (Human derived) were used for MTT assay. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay can be used to quantify the viability of cells. Briefly, cells per well were seeded into a 96-well plate. After overnight incubation, the products at concentrations ranging from 0 to 100 μg/ml in PBS (ph 7.4) were added. After 48 h incubation at 37 o C, the MTT was added into each well containing cells. and continued incubating for 4 h. All medium is removed and DMSO is added to each well, then absorbance was measured by microplate reader (BMG). S3

4 111 Intensity (a.u.) θ/degree Figure S1. XRD pattern of the as-prepared sample Ni 7 Co 3 alloy nanoparticles j CKa Counts NiLl NiLa CuLl NiKa CoLl CoLa CuLa CoKa CoKb CuKa NiKb CuKb Figure S2. Energy-disperse X-ray spectrum (EDS) taken on the selected area containing Ni 7 Co 3 nanoparticles. kev S4

5 70000 Relative Intensity (CPS) C1s N1s O2s Co2p Ni2p Binding Energy (ev) Figure S3. XPS spectrum of the obtained Ni 7 Co 3 nanorings. Figure S4. (a) HRTEM image of a typical Ni 7 Co 3 nanoparticle. (b) Magnified HRTEM image in selected area marked in (a). S5

6 Figure S5. (a-b) TEM images and (c-d) SEM images of the Ni 7 Co 3 nanoparticles synthesized under single-side magnet induced external magnetic field. The Ni 7 Co 3 alloy nanochains were synthesized under the same conditions as those for Ni 7 Co 3 nanorings. A slab magnet was placed on the top of autoclave in the synthesis. Figure S6. SEM images of Ni-Co alloy microwires composed of a lot of nanoparticles. The Ni 7 Co 3 alloy microwires were synthesized under the same reaction conditions as those for Ni 7 Co 3 nanorings but under an induced external magnetic field using a 0.08 T double-side symmetrical magnet. Two same slab magnets were placed standing at two sides of autoclave symmetrically. S6

7 Figure S7. (a-c) TEM images of Ni 7 Co formaldehyde resin nanorings synthesized in aqueous solution of phenol and hexamethyltetramine at 160 o C for 4 h. (d-e) SEM images Ni 7 Co formaldehyde resin nanorings. Figure S8. (a) TEM image of Ni 3 Co 7 nanoparticles. (b) TEM image of Ni 5 Co 5 nanoparticles. In the synthesis of Ni 3 Co 7 nanoparticles and Ni 5 Co 5 nanoparticles, the total precursor concentration was kept constant and was the same as the precursor concentration in the synthesis of Ni 7 Co 3 nanorings, and the molar ratios of Ni(acac) 2 and Co(acac) 2 were changed into 3:7 and 5:5, respectively. Other experimental conditions were the same as the conditions for the synthesis of Ni 7 Co 3 nanorings. S7

8 M (emu/g) H(Oe) Figure S9. The hystersis loop for as-synthesized Ni 7 Co 3 nanorings at 300 K. Figure S10. (a), (b) Photograph of the Ni 7 Co 3 nanorings dispersed in the water and response to external magnetic field. S8

9 3.0 Ni 7 Co OD control 1ng/ml 10ng/ml 100ng/ml 1ug/ml 10ug/ml Figure S11. MTT cytotoxicity assay of the prepared Ni 7 Co 3 nanorings. [Ni+Co] (mg/ml) T 2 -weighted Image Figure S12. T 2 -weighted magnetic resonance images of the prepared Ni 7 Co 3 nanorings. S9