Non linear magnetic behaviour around zero field of an assembly of superparamagnetic nanoparticles

Transcription

1 This journal is The Royal Society of Chemistry 0 Supporting information Non linear magnetic behaviour aroun zero fiel of an assembly of superparamagnetic nanoparticles Caroline e ontferran, 4, Yoann Lalatonne,, Dominique Bonnin 3, Laurence otte *, Philippe ono 3 - CSPBAT laboratory, UR 744 CNRS, University of Paris 3, France, - Service éecine Nucléaire, Hôpital Avicenne, Bobigny, France 3- LPE, UPR 5 CNRS, ESPCI ParisTech, France 4- agnisense France, Paris, France *Corresponing author laurence.motte@univ-paris3.fr,laurence.motte-torcheux@univ-paris3.fr Telephone: ++33(0) ; Fax: ++33(0)

2 This journal is The Royal Society of Chemistry 0 ultiparametric Testing In an attempt for multiparametric feasibility, two SP probes : lab-mae -Fe O 3 nanoparticles an commercial Estapor beas (00/50, erck), are mixe at ifferent ratios. The iron concentration of the two ferrofluis was ajuste in orer to obtain IAplex signatures at isointensity. Fig. SA shows the IAplex signatures of the two kins of particles. Fig. SB-D shows the experimental IAplex signatures measure by mixing the two kins of particles in various proportions an the corresponing calculate curves. A rather goo agreement is obtaine between experimental an calculate curves. This confirms the high sensitivity of measuring B(H)/H for characterization an separation purpose. Figure S: A : IAplex signature for nanoparticles (ashe line) an Estapor beas (soli line). Experimental (open circles) an calculate (soli line) curves for 75%-5% (B), 50%-50% (C), an 5%-75% (D) nanoparticles-estapor mixtures. Synthesis an characterization of Fe O 3 nanoparticles Soium n-oecyl sulfate (99%, Alfa Aesar), imethylamine solution (40%, Fluka), Iron (II) Chlorie Tetrahyrate (Sigma Alrich) were use as receive. Water is purifie with a illipore system (resistivity 8..cm). Concerning lab-mae nanoparticles, they are synthesize accoring to a proceure alreay escribe. Briefly, non coate Fe O 3 particles were synthesize by reaction of ferrous oecyl sulfate with imethylamine in water for two hours at 8 C. The nanocrystal surface is then functionalize with 5-

3 This journal is The Royal Society of Chemistry 0 hyroxy-5,5-bis(phosphono)pentanoic aci, which allows a goo ispersion in water of the nanoparticles. The nanoparticles surface is characterize via infrare spectroscopy (Fig. S). Figure S: Infrare spectra of free 5-hyroxy-5,5-bis(phosphono)pentanoic aci (HBP) (otte line) an 0nm Fe O nanoparticles (soli line). The spectrum of free HBP molecule contains peaks at 706cm - (C=O), 637cm - (carboxylic C-O), 309 an 3cm - (CH ), 46 an 059cm - (P-O). The spectrum of coate nanoparticles presents a very intense ban at 577cm - attribute to Fe an a large intense vibration ban between 50 an 950cm - which correspons to the P-O absorption ban. Compare to free molecule, this moifie ban inicates that the molecule is bone at the surface of the particle via the hyroxymethylenebisphosphonate terminal function. The coating rate has been quantifie via the P-O area ban an is evaluate as about 500 HBP molecules per nanoparticle. Nanoparticles crystal size an structure were characterize by X-ray iffraction (XRD) an Transmission Electron icroscope (TE). XRD pattern (Fig. S an S3) was measure with an X-ray power iffractometer moel X Pert PRO, PD, PANalytical, Almelo, the Netherlans, CoKα beam in Bragg Brentano geometry (y/y) was use combine with a fast etector base on real time multiple strip technology (X Celerator). Crystal XRD size was etermine with the Scherrer formula. TE images were obtaine using a FEI C0 icroscope an samples were prepare by epositing a rop of nanoparticles suspension on carbon coate copper gris place on a filter paper.

4 Figure S3: XRD pattern 0nm Fe O nanoparticles. Figure S4: XRD pattern of Ferrotec Nanoparticles The stars Figure S3 inicate the presence of NaCl resiue. Phases ientifie are maghemite Fe O 3 an magnetite Fe 3 O 4 (EVA software (version 3, Bruker-AXS, Karlsruhe, Germany, ) an JCPDS-International Centre for Diffraction Data Power Diffraction File (PDF-, JCPDS-ICDD, Newtown Square, PA)). Crystal size is etermine via the Scherrer equation an is 9.9nm. The meian iameter 0 an stanar eviation w are euce from TE ata measurements, simulating the iameter istribution with a lognormal function g() escribe in equation (). 0 ln exp ) ( g () The parameter is relate to the stanar eviation w by the relation (). ln 4 ln me me w w () Electronic Supplementary aterial (ESI) for Analyst This journal is The Royal Society of Chemistry 0

5 This journal is The Royal Society of Chemistry 0 agnetic properties of Fe O 3 nanoparticles agnetic properties were measure using a superconucting quantum interference evice (Quantum Design SQUID agnetometer PS-5T) at 300 K an the IAplex technology. Samples measure with SQUID are liqui suspensions in water, 0.5wt%, conitione in silicone capsules supplie by Plastem S.A. Concerning the IAplex, samples are also liqui suspensions in water 0.5wt% an wt%, conitione in 500µL Eppenorf. The saturation magnetization is obtaine by the extrapolation of the plot of magnetization vs the inverse of the fiel at the origin (Fig. S4). Figure S5: agnetization as function of /H. The re line is the asymptote when /H tens to zero. The intersection between this asymptote an y- axis is the experimental saturation magnetization sat. Consiering a core-shell system, the spin canting thickness e an the corresponing magnetic size ( 0 - e) are euce from the equation () e sat satbulk () 0 For the lab-mae nanoparticles with 0 = 0.5nm as TE iameter an sat = 6emu/g, we calculate a magnetic size of m = 9.6nm, corresponing to a non magnetic layer of e 0.45 nm. We estimate the contribution of the shell in the total volume of the particles from the equation (3). %( V shell 3 3 V Vcristalline V shell magnetic 0 m ) (3) V V cristalline cristalline We so obtaine a shell contribution of 4% of the particle volume. 3 0 The Langevin moel of superparamagnetism 4 can be use to escribe the non-linear magnetization curve of the nanoparticles, assuming that particles o not interact, by the equation (4). sat0h kbt coth kbt (4) sat H sat 0

6 This journal is The Royal Society of Chemistry 0 ν is the volume of the magnetic core, is the particle ensity (4900kg.m -3 for maghemite), sat (emu.g - ) is the saturation magnetization of the particle, T is the sample temperature in Kelvin (taken to be 300 K), μ 0 is the permeability of vacuum (4π 0 7 H.m - ), H is the applie fiel (in A.m - ) an k b is the Boltzmann constant, J.K -. As to moel the experimental magnetic ata, we have use the Langevin equation weighte by a lognormal function (equation ). The experimental curves at high an meium magnetic fiel ranges are fitte with Langevin equation weighte by log-normal istribution. At low magnetic fiel range, the experimental curve are fitte with the sum of Langevin equations weighte by log-normal istribution an corresponing to separate contributions. The secon erivative of the magnetization fit at high an meium magnetic fiel ranges is compare with the IAplex signature (Figure S5). Figure S6: Secon erivative of the magnetization fit at high an meium magnetic fiel range (otte line) superpose with the IAplex signal (soli line). The secon erivative of the high an meium magnetic fiel magnetization fit presents a peak-topeak line with in fiel H pp = 4.4 ± 0. ka.m - which is about 3.7 times bigger than the IAplex signature (H pp = 3.9 ± 0. ka.m - ).. Lalatonne, Y. et al. Bis-phosphonates-ultra small superparamagnetic iron oxie nanoparticles: a platform towars iagnosis an therapy. Chemical Communications, (008).. Caizer, C. Saturation magnetization of [gamma]-feo3 nanoparticles isperse in a silica matrix. Physica B: Conense atter 37, 7-33 (003). 3. illan, A. et al. Surface effects in maghemite nanoparticles. Journal of agnetism an agnetic aterials 3, L5-L9 (007). 4. u Trémolet e Lacheisserie, E. agnétisme Fonements Vol. I. (Grenoble Science, Grenoble; 000).