Supporting Information

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1 Supporting Information Superparamagnetic luminescent 3 O 4 /SiO 2 composite particles for signal augmentation by magnetic harvesting as potential water detectors Tobias Wehner, Karl Mandel *, Michael Schneider, Gerhard Sextl and Klaus Müller- Buschbaum * Julius-Maximilians-University Würzburg, Institute of Inorganic Chemistry, Am Hubland, D97074 Würzburg, Germany Fraunhofer Institute for Silicate Research, ISC, Neunerplatz 2, D97082 Würzburg, Germany Julius-Maximilians-University Würzburg, Chair of Chemical Technology of Materials Synthesis, Röntgenring 11, D97070 Würzburg, Germany AUTHOR INFORMATION Corresponding Author k.mueller-buschbaum@uni-wuerzburg.de karl-sebastian.mandel@isc.fraunhofer.de S-1

2 Synthesis of superparamagnetic nanocomposite microparticles The synthesis of superparamagnetic Fe 3 O 4 /SiO 2 microparticles has been reported before. S1 In brief, iron salts were dissolved in deionized water at room temperature. The addition of ammonia solution led to the precipitation of agglomerated magnetite (Fe 3 O 4 ) nanoparticles. To form a stable nanoparticle sol (ferrofluid), nitric acid was added to the washed precipitate. Subsequently, again, ammonia solution was added to the stabilized sol and the mixture was heated to 70 C in air with stirring. To form the silica-matrix, a sodium silicate solution was added slowly through a syringe needle. The obtained product was magnetically removed and washed. S1 Synthesis of 2 [Ln 2 Cl 6 (bipy) 3 ] 2bipy and [LnCl 3 (py) 4 ] 0,5py (Ln = Eu, Tb) Prior to the MOF syntheses, anhydrous lanthanide chlorides were prepared by the ammonium halide route S2 by reaction of Tb 4 O 7 or Eu 2 O 3 with NH 4 Cl in concentrated HCl via the salt [NH 4 ] 3 [LnCl 6 ] followed by thermal decomposition and purification by sublimation. The synthesis of 2 [Ln 2 Cl 6 (bipy) 3 ] 2bipy (Ln = Eu, Tb) was carried out according to reference S3 by an organic melt approach, in which LnCl 3 and 4,4 -bipyridine were heated and excessive 4,4 - bipyridine was removed by subsequent sublimation. For the syntheses of the lanthanide pyridyl complexes [LnCl 3 (py) 4 ] 0,5py (Ln = Eu, Tb) the halides LnCl 3 were treated with excessive amounts of pyridine and heated under reflux according to reference. S4 Analytical investigations Fluorescence microscopy images were obtained on an inverted fluorescence microscope (Zeiss, Axiovert 200 M) equipped with a 120 W Xe lamp using a 10x objective and FITC filters. Samples were prepared under inert gas atmosphere on an object plate. S-2

3 Excitation and emission spectra were recorded with a Horiba Jobin Yvon Fluorolog 3 photoluminescence spectrometer equipped with a 450 W Xe lamp, an integration sphere, Czerny Turner double grating (1200 grooves per mm), excitation and emission monochromators and FL-1073 PMT detector. To block the 1 st and 2 nd harmonic oscillation of the light source, an edge filter (400 nm) was used. PXRD analysis was carried out on a Bruker D8 Discover diffractometer with Da Vinci design, focusing Göbel mirror and linear LynxEye detector. Powder samples were prepared in Lindemann glass capillaries with 0.3 mm diameter under inert gas atmosphere. The samples were measured in transmission geometry using CuK α radiation (λ = Å). Magnetic properties of vacuum dried particles were studied with a vibrating sample magnetometer (VSM, VersaLabTM 3T, Cryogenfree Vibrating Sample Magnetometer), cycling the applied field from 30 to +30 koe for two times with a step rate of 100 Oe/s. Detailed analyses were carried out by cycling the applied field from -5 to +5 koe with 5 Oe/s. The temperature was set to 293 K (20 C, RT). Scanning electron microscopy (SEM) was carried out with a Zeiss Supra 25 SEM at 3 kev. Energy dispersive X-ray analyses (EDX) were conducted at 15 kev at a working distance of 8 mm. The specific surface area was measured by N 2 adsorption using Brunauer Emmett Teller (BET) analyses following DIN66131 with a Quantachrome Instruments Autosorb 3B. S-3

4 2 Figure S1: Powder diffraction patterns of the composite systems [Ln 2 Cl 6 (bipy) 3 ] 2bipy@Fe 3 O 4 SiO 2 compared to a pattern of 2 [Eu 2 Cl 6 (bipy) 3 ] 2bipy simulated from the single crystal structure and to Fe 3 O 4 SiO 2 microparticles. Figure S2: The MOF@magnetic particle system exhibits superparamagnetic properties. The overlap of superparamagnetic and paramagnetic properties are well-pronounced in the magnetization curves for the Tb system (a) and less prominent for the Eu system (b) at high external field (approximately visible in the region above 0.8 T), which fits well to the fact that Tb has a susceptibility which is ten times higher than that of Eu. S-4

5 Figure S3: Luminescence intensity / H 2 O concentration dependence as exponential fit of the emission intensity decrease of 2 [Eu 2 Cl 6 (bipy) 3 ] 2bipy@Fe 3 O 4 /SiO 2 in hexane (left) and toluene (right). Literature S1 S2 S3 S4 Mandel, K.; Hutter, F.; Gellermann, C.; Sextl, G. Modified Superparamagnetic Nanocomposite Microparticles for Highly Selective Hg II or Cu II Separation and Recovery from Aqueous Solutions. ACS Appl. Mater. Interfaces 2012, 4, Taylor, M. D.; Carter, C. P. Preparation of Anhydrous Lanthanide Halides, Especially Iodides. J. Inorg. Nucl. Chem. 1962, 24, Bünzli, J. C.;Eliseeva, S. V. in Springer Series on Fluorescence: Lanthanide Luminescence: Photophysical, Analytical and Biological Aspects, Vol. 7 (Eds: O. S. Wolfbeis, M. Hof.), Springer Verlag, Berlin, Li, J.-S.; Neumüller, B.; Dehnicke, K. Pyridin-Komplexe von Seltenerd-Trichloriden. Synthese und Kristallstrukturen von [YCl 3 (Py) 4 ] und [LnCl 3 (Py) 4 ] 0,5 Py mit Ln = La und Er. Z. Anorg. Allg. Chem. 2002, 628, S-5