Supplementary Information
Gadolinium doped Europium Sulfides Srotoswini Kar, William Boncher, Daniel Olszewski, Normal Dollahon, Richard Ash, Sarah Stoll. Experimental. The dithiocarbamate precursors were prepared according to previously published procedures.1 For low doping levels Eu1-xGdxS, for x< 0.1, stock solutions of the Gd precursor were prepared and diluted to obtain the low concentrations described below. Eu1-xGdxS polycrystalline powder. Precursors with ratios of the dithiocarbamate precursors (Eu(S2CNEt2)Phen:Gd(S2CNEt2)3Phen) to result in x = 0.003, 0.004, 0.006, 0.03, 0.05, 0.1 were dissolved in CHCl3, for intimate mixing, and the solvent evaporated. The powders were loaded in a quartz tube inside a glove box and the system was sealed and heated to 700°C for 5 hours. Black crystalline materials were isolated. Eu1-xGdxS nanoparticles. Eu0.99Gd0.01S: [N(H2Et2)Eu(S2CNEt2) 4] (0.2081 g, 0.254 mmol) and [Gd(S2CNiBu2)3Phen] (0.0024 g, 0.0025 mmoles) were dissolved in oleylamine (2.4 mL), resulting in a red-orange solution. In a three-neck flask, triphenylphosphine (3.81 g) and oleylamine (2.4 mL) were heated to 265°C under nitrogen. The precursor was quickly injected into the hot OA/TPP mixture and the temperature was maintained at 265°C for 1 h. The temperature was then reduced to 70°C, and anhydrous ethanol (100 mL) was added to the solution. In a glove box the solution was transferred to a centrifuge tube, and centrifuged at 3800 rpm for 30 minutes. The yellow-green supernatant was discarded, and the purple-black powder dissolved in anhydrous heptanes (2 mL). Fresh ethanol (100 mL) was added to the dark purple solution, and the precipitate was isolated by centrifugation, and dried in vacuo. Eu0.975Gd0.025S: the precursor amounts were [N(H2Et2)Eu(S2CNEt2) 4] (0.2081 g, 0.254 mmol) and [Gd(S2CNiBu2)3Phen] (0.0062 g, 0.0065 mmol), and the rest of the procedure was the same as described above. Characterization. Structural. X-ray powder diffraction patterns were obtained using a Rigaku RAPID Curved IP X-ray powder diffractometer with Cu-Kα radiation and an image plate detector. Samples were prepared for TEM measurements by dipping carbon coated copper TEM grids five to six times into solutions of the nanoparticles, allowing the grids to dry briefly before re-immersion. Images were taken on a Hitachi H-7600 with an EDAX eds analysis system and an AMT digital camera.
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Siddall, T. H.; Stewart, W. E. J. of Inorg. and Nuclear Chem. 1970, 32(4), 1147-1158, b) Jorgensen, C. K. Molec. Phys. 1962, 5, 271. S1
Elemental. Europium-gadolinium ratios were determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Samples were ablated using a 213nm wavelength ultraviolet laser (New Wave UP213) and ratios measured using a ThermoFinnigan Element 2 magnetic sector, single collector ICP-MS. Samples were ablated with a 15µm spot and a photon flux between 2 and 3Jcm-2 and a laser repetition rate of 7Hz. A mixture of both spots and lines were used for measurement, with no discernable difference in the results. Ablation was into a stream of helium, with downstream mixing into the Ar flow for introduction into the plasma. NIST610 (a synthetic glass doped with lithophile trace elements) was ablated under matching conditions (though with a larger spot size) for standardization. Both Eu isotopes (151 and 153) were measured as were all 7 Gd isotopes (152, 154, 155, 156. 156, 158 and 160). All were measured in analog mode due to the high Eu and Gd concentrations, but 152Gd and 154Gd were not usefully determined due to their low natural abundance. The other five Gd isotopes were used for elemental ratio determination. Other rare earths were measured, but remained largely below detection. Elemental ratios were determined using LAMTRACE software, with an assumed Eu abundance – hence ratio determination rather than absolute abundances. Both Eu and the abundant Gd isotopes gave internally consistent results and isotopic ratios with the expected natural abundances. Samples were mounted on double sided tape, with the fine powders pressed into the tape with a clean spatula to ensure adherence to the surface. Based on the Eu:Gd ratio, the composition for the polycrystalline samples determined from ICP-MS is listed in the table below. For the nanoparticles, x = 0.01 (found 0.0062(3)) and x = 0.025 (found 0.0178(4)). Magnetic. Magnetic measurements were made on a QD SQUID from 100 to 5K in fields ranging from 500 to 5000 Oe. Crystalline, powdered samples containing ca. 1-20 mg of compound were loaded into a gelatin capsule and packed with quartz wool. The sample was positioned within a plastic straw for analysis. The diamagnetic correction of the sample holder was measured and subtracted from the data, and the diamagnetic correction for the sample was calculated using χd = (-184.03/2)10-6 emu-mole. The paramagnetic Curie Temperature, Θ, was determined using 1/χ versus T plots. The plots were fit using a linear regression and the theta and R2 values are listed in the table below. For the nanoparticles, x = 0, theta was 17.63 (R2 = 1.0000), x = 0.0062(3), theta was 7.82 K (R2 = 0.9995) and x = 0.0178(4), theta was 5.85K (R2 = 0.9992). Table 1. Summary of elemental and magnetic data for polycrystalline Eu1-xGdxS. “x” Experimental x Theta R2 0.0000 0.0000 19.05 1.0000 0.0040 0.00177(3) 30.08 0.9974 0.0030 0.0030(9) 21.23 0.9998 0.0060 0.00636(26) 19.68 1.0000 0.0300 0.017(2) 19.14 1.0000 0.0500 0.0264(5) 18.06 1.0000 0.1000 0.068(1) 17.97 1.0000
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S1. Representative X-ray Powder Diffraction Pattern of Eu1-xGdxS, for Eu0.90Gd0.1S. S2. Representative TEM of Eu1-xGdxS (Eu0.90Gd0.1S) polycrystalline sample. S3. Representative EDS of Eu1-xGdxS, (Eu0.90Gd0.1S) polycrystalline sample. S4. Reduced magnetization versus T for Eu1-xGdxS (x = 0.003-0.1) polycrystalline sample. S5. 1/chi versus T for Eu1-xGdxS (x = 0.003-0.1) polycrystalline sample. S6. X-ray Powder Diffraction pattern of Eu1-xGdxS (x~ 0.01) nanoparticles. S7. Reduced magnetization versus T for nanoparticles of EuS, Eu0.99Gd0.01S, and Eu0.98Gd0.02S.
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S1. Representative X-ray Powder Diffraction Pattern of Eu1-xGdxS, for Eu0.90Gd0.1S.
S2. Representative TEM of Eu1-xGdxS (Eu0.90Gd0.1S), for polycrystalline sample.
S3. Representative EDS of low doped Eu1-xGdxS, (Eu0.90Gd0.1S).
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S4. Reduced magnetization versus T for Eu1-xGdxS (x = 0.001-0.1) polycrystalline sample.
S5. 1/chi versus T for Eu1-xGdxS (x = 0.001-0.1) polycrystalline sample.
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S6. X-ray Powder Diffraction pattern of Eu1-xGdxS (x~ 0.99) nanoparticles.
S7. Reduced magnetization versus T for nanoparticles of EuS, Eu0.99Gd0.01S, and Eu0.98Gd0.02S.
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