SUPPORTING INFORMATION. a) Anorganische Chemie I-Festkörperchemie und Materialien, Ruhr-Universität Bochum, D Bochum,

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1 SUPPORTING INFORMATION Facile preparation of quantum cutting GdF 3 :Eu 3+ nanoparticles from ionic liquids Chantal Lorbeer a, Joanna Cybinska a,b, Anja-Verena Mudring a * a) Anorganische Chemie I-Festkörperchemie und Materialien, Ruhr-Universität Bochum, D Bochum, b) Faculty of Chemistry, University of Wrocław, Joliot-Curie 14, PL Wrocław, Poland Experimental Section Preparation of [C 4 mim][cl]. The ionic liquid [C 4 mim][cl] was prepared according to a common literature procedure 1. 1-Methylimidazole (73 ml, 0.9 mol) was heated under reflux with 1-chlorobutane (95 ml, 0.9 mol) in acetonitrile (110 ml) for 72 h. After complete removal of acetonitrile under vacuum, the product was dissolved in dichloromethane and recrystallized from toluene at -50 o C. White crystals of product were isolated by filtration, washed with cold toluene, and dried in vacuo. Yield: g (78 %). 1 H NMR (250 MHz, CDCl 3 ): (s, 1H, imidazole C(2)H), 7.50 (d, 1H, imidazole CH=CH), 7.37 (d, 1H, imidazole CH=CH), 4.30 (t, 2H, NCH 2 ), 4.10 (s, 3H, NCH 3 ), 1.87 (quin., NCH 2 CH 2 ), 1.34 (sext., 2H, NCH 2 CH 2 CH 2n ), 0.93 (t, CH 3 ). 13 C{ 1 H} NMR (74.5 MHz, CDCl 3 ): , , , 48.53, 35.40, 31.48, 19.41, Anal. Calcd for C 8 H 15 N 2 Cl: C, 55.0; H, 8.7; N, Found: C, 54.8; H, 8.7; N, Preparation of [C 4 mim][bf 4 ]. The task-specific ionic liquid (TSIL) [C 4 mim][bf 4 ] was prepared according to a common literature procedure 2. 1-Butyl-3-methylimidazolium chloride (122.1 g, 0.7 mol) was stirred with sodium tetrafluoroborate (76.9 ml, 0.7 mol) in acetonitrile (800 ml) for 72 h at room temperature. After filtration, the mixture was stirred for additional 24 h with 5 g activated carbon. The activated carbon was removed by filtration and 1 P. Wasserscheid, T. Welton (Eds.), Ionic Liquids in Synthesis, Wiley VCH, Weinheim, Lala in P. Wasserscheid, T. Welton (Eds.), Ionic Liquids in Synthesis, Wiley VCH, Weinheim, 2008.

2 acetonitrile was completely removed under vacuum. The residual liquid was mixed with dichloromethane (300 ml) and washed with little amounts of water in order to remove the chloride (silver nitrate test). The colorless liquid was isolated and dried in vacuo. Yield: g (85 %). 1 H NMR (250 MHz, CDCl 3 ): 8.64 (s, 1H, imidazole C(2)H), 7.37 (d, 2H, imidazole CH=CH), 4.14 (t, 2H, NCH 2 ), 3.88 (s, 3H, NCH 3 ), 1.80 (quin., NCH 2 CH 2 ), 1.25 (sext., 2H, NCH 2 CH 2 CH 2n ), 0.86 (t, CH 3 ). 13 C{ 1 H} NMR (74.5 MHz, CDCl 3 ): , , , 48.87, 35.30, 31.12, 18.52, Anal. Calcd for C 8 H 15 N 2 BF 4 : C, 42.5; H, 6.7; N, Found: C, 42.2; H, 6.6; N, General Synthesis of nano-lnf 3. To avoid undesired oxygen impurities in the reaction products the synthesis was carried out under inert atmosphere. In a typical synthesis, 150 mg Gd(Ac) 3 4H 2 O (99.9%, ABCR) and the desired amount (see below) of Eu(Ac) 3 H 2 O (99.9%, Alfa Aesar) is dissolved in 2 ml ethylene glycol (99 %, J.T. Baker). ESI-Table 1. Amounts of Gd(Ac) 3 4H 2 O and Eu(Ac) 3 H 2 O used for synthesis. 6 ml of the TSIL [C 4 mim][bf 4 ] are added and the reaction mixture is stirred until a homogenous solution is obtained. The reaction solution is then placed in a compression-proof reaction vessel and heated in a single mode microwave (Discover, CEM) operating at a frequency of 2455 MHz within 5 minutes to 120 C. This temperature is held for additional ten minutes by automatically adjusting the radiation power of the microwave. During the reaction, temperature and pressure surveillance is assured. After the reaction the reaction mixture is cooled to room temperature by means of pressurized air. To isolate the LnF 3 nanoparticles, the obtained colloidal solution is centrifuged under ambient conditions. The solid LnF 3 nanomaterial is washed several times with ethanol (p.a., Riedel de Haën) and dichloromethane (99.9%, Fisher Scientific). After drying at 60 C, the colorless powder LnF 3 powders which were obtained in quantitative yield were checked for identity by powder X-ray analysis.

3 Characterization and physico-chemical properties: XRD. XRD measurements were carried out on a Huber G670 diffractometer (Rimsting, germany) operation with Mo K radiation ( = nm. g f Intensity [a.u.] e d c b Θ [ ] a ESI-Figure 1. X-ray diffraction pattern of (a) GdF 3 PDF , (b) EuF 3 PDF , (c) GdF 3, (d) GdF 3 :Eu 0.5 %, (e) GdF 3 :Eu 5 %, (f) GdF 3 :Eu 10 %, (g) EuF 3.

4 Luminescence spectroscopy. For the fluorescence measurements, a Fluorolog FL3-22 spectrometer from Horiba Jobin Yvon was used. Energy [ev] 4,5 4 3,5 3 2,5 d 1 d 2 c 1 Intensity [a.u.] c 2 b 1 b 2 a 1 a Wavelength [nm] ESI-Figure 2. Excitation spectra of : (a) EuF 3 at room temperature (1) and 77 K (2), (b) GdF 3 :Eu 3+ (0.5%) at room temperature (1) and 77 K (2), (c) GdF 3 :Eu 3+ (5%) at room temperature (1) and 77 K (2) and (d) GdF 3 :Eu 3+ (10 %) at room temperature (1) and 77 K (2). Assignment: with following assignment:320 nm - 7 F 0 5 H 6 ; 363 nm - 7 F 0 5 D 4 ; 378 nm - 7 F 0 5 G 2 ; 397 nm - 7 F 0 5 L 6, (strongest); and 467 nm - 7 F 0 5 D 2 ) for Eu 3+ ion and at 320 and 277 nm (strongest) originate from the transitions of 8 S 7/2 6 P J and 8 S 7/2 6 I J of Gd 3+, respectively.

5 Energy [ev] 2,4 2,3 2,2 2,1 2 1,9 1,8 5 D 1 7 F J J= D 0 7 F J J= d 1 d 2 Intensity [a.u.] c 1 c 2 b 1 b 2 a 1 a Wavelength [nm] ESI-Figure 3. Emission spectra excited under 393 nm (a) EuF 3 at room temperature (1) and 77 K (2), (b) GdF 3 :Eu 3+ (0.5%) at room temperature (1) and 77 K (2), (c) GdF 3 :Eu 3+ (5%) at room temperature (1) and 77 K (2) and (d) GdF 3 :Eu 3+ (10 %) at room temperature (1) and 77 K (2).

6 Energy [ev] 4 3,8 3,6 3,4 3,2 3 2,8 2,6 Gadolinium 6 P 7/2 8 S Europium 5 D 3 7 F J J= 4 5 c 1 c 2 Intensity [a.u.] b 1 b 2 a 1 a Wavelength [nm] Energy [ev] 2,4 2,3 2,2 2,1 2 1,9 1,8 J= D 1 7 F J c 1 J= D 0 7 F J Intensity [a.u.] c 2 b 1 b 2 a 1 a Wavelength [nm] ESI-Figure 4. Emission spectra excited under 275 nm with using a Xe lamp (a) EuF 3 at room temperature (1) and 77 K (2), (b) GdF 3 :Eu 3+ (0.5%) at room temperature (1) and 77 K (2), (c) GdF 3 :Eu 3+ (5%) at room temperature (1) and 77 K (2) and (d) GdF 3 :Eu 3+ (10 %) at room temperature (1) and 77 K (2)

7 ESI-Figure 5. CIE colour coordinates for EuF 3 (blue square) and GdF 3 :Eu 5% (red circle) at RT ESI-Table 2. The table collects the decay time of GdF 3 :Eu recorded at 293 and 77 K, excitation lines :275 and 395 nm.

8 Weight equation used to quantum yield calculation: where p CR and p DT are the probabilities of cross relaxation and direct energy transfer from Gd 3+ 6 G J to Eu 3+, respectively, and R( 5 D 0 / 5 D 1,2,3 ) 6 G J and R( 5 D 0 / 5 D 1,2,3 ) 6 P J are the 5 D 0 / 5 D 1,2,3 emission intensity ratios upon 6 G J excitation and upon 6 I J excitation, respectively.

9 TEM. TEM pictures were obtained using a Hitachi H-8100 with an acceleration voltage of 200 kv. The preparation of the sample was accomplished by suspending the colourless powder in ethanol by treating it in an ultrasonic bath for 20 minutes, a drop of the obtained suspension was then deposited on a carbon film supported copper grid. The particle size distribution was obtained by measuring the size of the synthesized particles on different overview TEM images with the program item (Olympus Soft Imaging System). In images with agglomeration, only particles at the border were considered. The averaged particle size and the standard deviation were calculated from the data Number Particle size [nm] ESI-Figure 6. Particle size distribution in GdF 3. ESI-Figure 7. SAED pattern of GdF 3.

10 Ch. Lorbeer, J. Cybinska, A.-V. Mudring, Facile preparation of quantum cutting GdF3:Eu3+ nanoparticles from ionic liquids ESI-Figure 8. TEM pictures of GdF3. 1,0 C Kα 0,6 Gd Mα Gd Mβ Gd Lα Gd Lβ2 0,2 Gd Lβ1 Gd Mγ Gd Ln Cu Kα Gd Lγ 0,4 F Kα Cu Lα Intensity [cps] 0,8 Cu Kβ 0, Energy [kev] ESI-Figure 9. EDX of GdF3.

11 Ch. Lorbeer, J. Cybinska, A.-V. Mudring, Facile preparation of quantum cutting GdF3:Eu3+ nanoparticles from ionic liquids ESI-Figure 10. TEM pictures of GdF3:Eu 10 % B 1,0 C Kα 0,6 0,4 Gd Mβ Gd Lβ2 0,2 Gd Lβ1 Eu Lβ Eu Mα Eu Lα Al Kα Gd Lγ, Eu Lγ Cu Kα Gd Lα F Kα Cu Lα Intensity [cps] 0,8 Cu Kβ 0, Energy [kev] ESI-Figure 11. EDX of GdF3:Eu 10 %.

12 Ch. Lorbeer, J. Cybinska, A.-V. Mudring, Facile preparation of quantum cutting GdF3:Eu3+ nanoparticles from ionic liquids ESI-Figure 12. SAED of GdF3: Eu 5 %. ESI-Figure 13. TEM pictures of GdF3: Eu 5 %. B 1,0 C Kα 0,6 Gd Lα Cu Kα Gd Mα Gd Lβ1 Eu Lβ Eu Mα Gd Lβ2 0,2 Eu Lα Gd Lγ, Eu Lγ 0,4 F Kα Cu Lα Intensity [cps] 0,8 Cu Kβ 0, Energy [kev] ESI-Figure 14. EDX spectrum of GdF3:Eu 5 %. 10