SUPPORTING INFORMATION

Transcription

1 Electronic Supplementary Material (ESI) for New Journal of Chemistry. This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2017 SUPPORTING INFORMATION Luminescence and energy transfer in β-nagdf 4 : Eu 3+, Er 3+ nanocrystalline samples from a room temperature synthesis Gabriella Tessitore, a* Anja-Verena Mudring, b and Karl W. Krämer. a a University of Bern, Department of Chemistry and Biochemistry, Freiestrasse 3, 3012 Bern, Switzerland. b Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, Stockholm, Sweden. address: Gabriella.Tessitore@dcb.unibe.ch

2 Experimental Section Synthesis of anhydrous rare earth acetates - The rare earth oxides were dissolved in a 50:50 v/v mixture of bidistilled water and glacial acetic acid (Merck, 99.9%) at 120 C. After a clear solution was obtained, the solvent was completely evaporated, and the dry powder further heated to 180 C in vacuum for 24 hours. The acetate hydrates transform to the anhydrous acetates under these conditions, as verified by powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA), see Figs. S1-2. Characterization methods - X-ray diffraction (XRD) patterns were measured on a STOE StadiP powder diffractometer in reflection geometry (Bragg-Brentano). A zero-reflection α-quartz sample holder was covered by a thin film of the nanoparticles. Cu K α1 radiation (λ= Å) was used from a 40kV 40mA X-ray source and a focusing α-quartz (101) monochromator. The data were recorded by a linear position sensitive detector with 0.01 resolution in 2- Theta. The thermal decomposition of the rare earth acetate hydrates was investigated by thermogravimetric analysis (TGA) on a Mettler TGA / SDTA 851e with 5 K/min. heating rates and a nitrogen gas flow of 20 ml/min. Transmission electron microscopy (TEM) pictures of the nanoparticles were obtained from water solutions with a particle concentration of 1 g/l dried on copper TEM grids with 300 mesh. Low resolution micrographs were recorded on a Philips CM12 TEM. A tungsten filament was used as 120 kv electron beam source. The pictures were recorded with an Olympus-SIS Morada CCD side-mounted camera (11 Megapixels) with fold magnification (micrographs with 200 nm scale bar). Higher resolution pictures were obtained on a Tecnai G2 Spirit BioTWIN TEM using a LaB kv electron beam. The images were recorded by an Olympus-SIS Veleta CCD side-mounted camera (4 Megapixels) at fold magnification (micrographs with 50 nm scale bar) and a FEI Eagle CCD bottom-mounted camera (16 Megapixels) at fold magnification (micrographs with 20 nm scale bar). The particle size was evaluated with help of the ImageJ 1.49v software (National Institute of Health, USA). Luminescence and excitation spectra were measured on a Horiba Jobin Yvon Fluorolog 3-22 spectrometer. As excitation source the light from a 450 W Xenon lamp was dispersed by a double monochromator (330 nm blaze, 1200 groves/mm). The luminescence was recorded using a single monochromator (330 or 500 nm blaze, 1200 groves/mm) and a cooled photomultiplier (Hamamatsu R928P). Dried powder samples were filled in glass tubes of 1 mm inner diameter. For comparative measurements of the luminescence intensity only the sample tubes were exchanged in a standard test setup. The reliability and repeatability of the measurements is better than 5%. All spectra were measured at room temperature. 2

3 Table S1 (A) Composition of the mother solutions. The molar weight (MW) is given in g/mol and the weight of the components in g. (B) Eu 3+ and Er 3+ contend of the samples for the 1% and 5% dopant series. The name of the mother solutions refers to (A) and the weight is given in g. A) Mother solutions Compound MW Name weight/g g/mol 1% Eu 3+ 5% Eu 3+ 1% Er 3+ 5% Er % NH 4F EG Gd(AcO) Eu(AcO) Er(AcO) NaCl NH 4F EG = ethylene glycol, AcO - = acetate B) Dopant series Name weight/g Name weight/g Eu% Er% 1% Eu 3+ 1% Er 3+ Eu% Er% 5% Eu 3+ 5% Er

4 Figure S1: Powder X-ray diffraction patterns of gadolinium acetatte hydrate (top) and anhydrous gadolinium acetate (bottom) measured with Cu K α1 radiation. The structural parameters were published in [S1]. Figure S2: Thermogravimetric analysis of rare earth acetate hydrates RE(AcO) 3 aq with RE = Gd, Eu, and Er. Curves are normalized to 200 C. The samples were heated by 5 K/min in a flow of 20 ml/min dry N 2. 4

5 Figure S3: TEM pictures of β-nagdf 4: 2% Eu 3+, 3% Eu 3+ (top) and β-nagdf 4: 0.4% Eu 3+, 0.6% Eu 3+ (bottom) nanocrystalline samples. Scale bars a given below the images. Figure S4: Emission spectra of bulk β-nagdf 4: 5% Er 3+ powder for Gd 3+ and Er 3+ excitation at 273 nm (36630 cm -1 ) and 377 nm (26525 cm -1 ), respectively. 5

6 Figure S5: Emission spectra of β-nagdf 4: 1% and 5% Er 3+ bulk samples for Gd 3+ and Er 3+ excitation at 273 nm ( cm -1 ) (A,B) and 377 nm ( cm -1 )(C,D), respectively. The intensity is normalized to the transition indicated by an asterisk. 6

7 Figure S6: Luminescence spectra of β-nagdf 4: x% Eu 3+, y% Er 3+ nanocrystalline samples for Gd 3+ excitation at 273 nm ( cm -1 ). Figure S7: Integrated intensity of the Eu 3+ 5 D 0 7 F 2 (red square), Gd 3+ 6 P J 8 S 7/2 (purple circle), and Er 3+ 2 P 3/2 4 I 13/2 (green triangle) luminescence of β-nagdf 4: x% Eu 3+, y% Er 3+ nanocrystalline samples shown in Fig. S6. The empty (filled) symbols refer to a 1% (5%) total doping for x% Eu 3+ and y = 1 - x (y = 5 - x) % Er 3+. Gd 3+ was excited at 273 nm ( cm -1 ). The integrated intensity is reported on a logarithmic scale. 7

8 Figure S8: Luminescence spectra of β-nagdf 4: x% Eu 3+, y% Er 3+ nanocrystalline samples for Er 3+ excitation at 377 nm ( cm -1 ). Figure S9: Expanded luminescence spectra from Fig. 8. Spectra are normalized to the Eu 3+ 5 D 0 7 F 2 emission at 615 nm ( cm -1 ), marked by an asterisk. The Er 3+ emission are marked as (a) 4 G 11/2 4 I 13/2, (b) 4 S 3/2 4 I 15/2, and (c) 2 H 9/2 4 I 13/2. 8

9 Figure S10: Normalized luminescence spectra of β-nagdf 4: x% Eu 3+, y% Er 3+ nanocrystalline samples for Eu 3+ excitation at 394 nm ( cm -1 ). Spectra are normalized to the Eu 3+ 5 D 0 7 F 2 emission at 615 nm ( cm -1 ), marked by an asterisk. Figure S11: Luminescence spectra of β-nagdf 4: x% Eu 3+, y% Er 3+ nanocrystalline samples for Eu 3+ excitation at 394 nm ( cm -1 ). 9

10 Figure S12: Integrated intensity of the Eu 3+ 5 D 0 7 F 2 (red square) luminescence of β-nagdf 4: x% Eu 3+, y% Er 3+ nanocrystalline samples shown in Fig. S10. The empty (filled) symbols refer to a 1% (5%) total doping for x% Eu 3+ and y = 1 - x (y = 5 - x) % Er 3+. Eu 3+ was excited at 394 nm ( cm -1 ). The integrated intensity are reported on a logarithmic scale. Reference [S1] C. Heinrichs, PhD thesis, Universität zu Köln, Synthese und Charakterisierung wasserfreier Selterdmetall-Nitrate, -Acetate und -Oxyacetate,