ACYS. Supporting Information: Water-Dispersible Iron Oxide Magnetic Nanoparticles with Versatile Surface Functionalities

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1 Supporting Information: Water-Dispersible Iron Oxide Magnetic Nanoparticles with Versatile Surface Functionalities Haiou Qu, Daniela Caruntu, Hongxue Liu, Charles J. O Connor* Fe() +Fe()+ NaOH+ DEG Heating Ligand Molecule ACYS Dopamine ABA MUA Citric acid Scheme 1. Illustration of the synthesis route for SPIONs with different coating and the corresponding molecular structures for the capping ligand.

2 a) b) c) d) Figure S1. TEM images of Fe3O4 nanoparticles with different coating (a) citric acid (b) aminobenzoic acid (c) dopamine (d) mercaptoundecanoic acid.

3 8 6 a) b) DEG stablized Fe ACYS coated Fe c) citric acid coated Fe 3 5 d) ABA coated Fe e) 5 f) dopamine coated Fe 3 MUA coated Fe Figure S2. Histogram of the particles sizes from Fe 3 nanoparticles with different coating (a) before injecting the new ligand (b) acetylcysteine (c) citric acid (d) aminobenzoic acid (e) dopamine (f) mercaptoundecanoic acid.

4 C Ka 8 Intensity 6 FeKa O Ka FeLa S Ka FeKb Energy(Kev) Figure S3. EDS spectrum of acetylcysteine coated Fe 3 nanoparticles. a) b) c) Figure S4. (a) Photos of Fe 3 nanocrystals aqueous solutions in response to external magnetic fields. Fe 3 nanocrystals dispersed in (b) physiological saline solution and (c) PBS buffer solution.

5 6 AYCS Citric Acid MUA ABA Dopamine Figure S5. Zeta potentials of functionalized nanoparticles as a function of ph value in physiological saline solution. It is not clear that why ACYS and MUA coated nanoparticles can only be well dispersed in basic condition and show negative Zeta potential. A possible explanation is that some of the thiol groups of MUA and ACYS or carbonyl groups 1 from the amide bond of ACYS coordinate with the iron cations on the surface of magnetite which leaves uncoordinated carboxylate groups exposed to the aqueous solution and get deprotonated under basic condition. a) b) Figure S6. TEM images of Fe 3 nanoparticles after coupling fluorescence molecules. (a) fluorescein-citric acid-fe 3 (b) rhodamine B-ABA- Fe 3.

6 Transmittance a) b) Wavenumber(cm -1 ) Figure S7. FT-IR spectra of functionalized magnetic nanoparticles after the conjugation with fluorescence molecules (a) fluorescein-citric acid (b) rhodamine B -ABA.

7 Figure S8. Decay curves of (a) fluorescein in ethanol (b) fluorescein on citric acid modified Fe 3 nanoparticles by monitoring 5 nm emission under 337 nm N 2 pulse laser excitation. Both of the curves can be fitted to single exponential: I= I exp(-t/τ).

8 Temperature Saturation Magnetization of Functionalized Fe 3 Nanoparticles with Different Ligand Shell (emu g -1 ) ACYS MUA ABA Dopamine Citric acid 5K 66.2 (8.7) a 64.3 (79.4) 69.9 (84.2) 71.7 (84.4) 62.7 (83.6) K 54.4 (66.4) 53.1 (69.5) 57.9 (69.8) 57.7 (67.8) 51.3 (68.4) a Saturation magnetization of Fe 3 nanoparticles normalized to the weight of magnetic core. Table S1. Saturation magnetization of functionalized Fe 3 nanoparticles. Temperature Saturation Magnetization of Fluorescence Molecule Conjugated Fe 3 Nanoparticles (emu g -1 ) rhodamine conjugated ABA coated Fe 3 fluorescein conjugated-eda-citric acid coated Fe 3 5K K Table S2. Saturation magnetization of fluorescence molecules conjugated Fe 3 nanoparticles. ACYS ABA Dopamine MUA Citric Acid Surface coverage (%) Capping ligand per particle Table S3. Surface coverage and the number of surface capping ligand molecules with respect to each functionalized nanoparticle. The number of ligand molecules on the surface of the magnetic nanoparticles is calculated in the following steps. 2 Assuming that each nanocrystal has spherical shape and all the nanocrystals are identical, the mass of a single nanocrystal is calculated by using bulk magnetite density 5.2 g cm -3 and the radius of each functionalized nanoparticles (i.e. 3 nm for citric acid coated nanoparticles). The mass of the same nanocrystals without the surface atomic layer is derived by using radius of 3 nm minus the surface atomic layer with Fe-O distance of 2.45Å. The fraction of the number of the surface metal atoms over the number of the total metal atoms per particle is equal to the ratio between the mass of the surface atomic layer and total mass of a single nanocrystal. Then, with the mole ratio of magnetite to each capping ligand, the fraction of iron ions covered by capping ligand

9 can be calculated. From the calculation, for ACYS, ABA, dopamine and citric acid coated nanoparticles, most of the carboxylate anion acts as a bidentate chelating ligand where two oxygen atoms coordinate with one iron atom. For MUA coated nanoparticles, only % of the iron atoms are covered by the capping molecules. In this case every carboxylate anion of MUA acts as a bidentate bridging ligand where the oxygen atoms are bound to adjacent iron metals/sites. Due to the steric hindrance from long carbon chain, the iron atoms on the surface are not fully covered by MUA. From infrared spectroscopy studies, all five samples show clear symmetric and asymmetric COO stretches which support the above calculation. 1 Li, Z.; Chen, H.; Bao, H.; Gao, M., Chem. Mater. 4, 16, Caruntu, D.; Remond, Y.; Chou, N. H.; Jun, M.-J.; Caruntu, G.; He, J.; Goloverda, G.; O'Connor, C.; Kolesnichenko, V., Inorg. Chem. 2, 41, 6137.