Supporting information for Manuscript entitled Tunable photoluminescence across the

Transcription

1 Supporting information for Manuscript entitled Tunable photoluminescence across the visible spectrum and photocatalytic activity of mixed-valence rhenium oxide nanoparticles. Yong-Kwang Jeong 1, Young Min Lee 2, Jeonghun Yun 2, Tomasz Mazur 1, Minju Kim 1,2, Young Jae Kim 1,2, Miroslaw Dygas 1, Sun Hee Choi 3, Kwang S. Kim 2, Oh-Hoon Kwon 1,2, Seok Min Yoon 1 *, Bartosz A. Grzybowski 1,2 * 1. Center for Soft and Living Matter, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea 2. Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea 3. Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea smy1201@ibs.re.kr, grzybor72@unist.ac.kr Table of Contents: Section S1. Characterization of MVReO NPs by TEM, XRD and XPS. Section S2. Time-correlated single-photon counting (TCSPC) studies of tunable photoluminescence depending on excitation wavelength of MVReO NPs. Section S3. L-1 edge XANES and contents of Re oxidation states of the MVReO NPs. Section S4. Simulated absorption spectra and density of states (DOS) of MVReO NPs. Section S5. Photocatalytic degradation of methyl orange (MO) by MVReO NPs. Section S6. Supplementary references: S1

2 Section S1. Characterization of MVReO NPs by TEM, XRD and XPS. Figure S1. PXRD spectra illustrates structural transformation from Re 2 O 7 to ReO 3 upon heating the Re 2 O 7 to 200 o C (in 1-octadecene with oleic acid). (a) PXRD of pristine ReO 3 has perovskite-like unit cell (space group: pm-3m, a = b = c = 3.75, α = β = γ = 90 o JCPDF number: ). (b) PXRD of MVReO NPs shows the same reflections as the pristine ReO 3 crystal structure. Panels (b) to (d) illustrate how the PXRD spectra change when the Re 2 O 7 precursor is subject to increasing reaction temperatures. (e) PXRD pattern of commercially available Re 2 O 7 powder. (f) Scheme illustrating transformation of Re 2 O 7 structure into ReO 3. S2

3 Figure S2. TEM images of MVReO NPs fractioned according to size by centrifugation. 2 TEM images show batches with average sizes (a) 22 ± 6.0 nm, (b) 33 ± 7.1 nm (c) 69 ±13.1 nm. Figure S3. XPS spectra of the batches of particles having average sizes of (a) 30 nm and (b) 70 nm. S3

4 Section S2. Time-correlated single-photon counting (TCSPC) studies for tunable photoluminescence depending on excitation wavelength of MVReO NPs. Figure S4. Excitation-wavelength-dependent photoluminescence (EWDP) according to sizes of MVReO NPs. EWDP of (a) 20 nm, (b) 30 nm, and (c) 70 nm MVReO NPs. (d) The graph plots emission wavelength vs. excitation wavelength according to different particle sizes. Figure S5. Fluorescence kinetic profiles of MVReO NPs in 1-octadecene. The samples were excited at (a) 450 nm and (b) 510 nm. Fluorescence kinetic profiles were monitored at various wavelengths, the representative examples of which are given in each panel. S4

5 Figure S6. Comparison of the MVReO NPs PL decays with variation of excitation wavelength. Fluorescence kinetic profiles were monitored at (a) 530 nm, (b) 550 nm, and (c) 600 nm. Figure S7. Normalized time-resolved PL spectra of MVReO NPs constructed from fluorescence transients with excitation at (a) 450 nm and (b) 510 nm. S5

6 Section S3. L-1 edge XANES and contents of Re oxidation states of the MVReO NPs. Figure S8. X-ray absorption near edge structure (XANES) for L 1 -Edges of commercially available Re 2 O 7 (Sigma-Aldrich, black), ReO 3 (Sigma-Aldrich, red), ReO 2 (Sigma-Aldrich, blue), and 20 nm (green), 30 nm (pink), and 70 nm (khaki) MVReO NPs. Table S1. The contents of +7 and +6 states in MVReO NPs calculated based on linearcombination-fits and using Re 2 O 7 and ReO 3 reference spectra for the Re L 3 -edge. Particle size +7 state (%) +6 state (%) 20 nm nm nm S6

7 Section S4. Simulated absorption spectra and density of states (DOS) of MVReO NPs. To understand the doping effect, the band structure and absorption spectra of the 2x2x2 supercell of ReO 3 family were investigated using density functional theory (DFT). The GGA- PBE xc-functional 3 and the PAW basis set 4 were employed using the VASP package. 5 We considered the doped cases that Re(IV) and Re(VII) ions were added to the center of a supercell (Figures S9a and S9b). To describe Re(VII), 15 valence electrons were used for Re. In addition, one oxygen-vacant state per 2x2x2 supercell (VacO or Ø) was studied (Fig S9c). VASP package 6 was used, and GGA-PBE xc-functional 7 was employed within the PAW basis set 8. The absorption spectra and density of state (DOS) profile of each case were obtained using GW0 approximation. 9 Figure S9. Schematic view of (a) pristine, (b) heavily doped ReO 3, and (c) oxygen vacant systems for simulated absorption spectra and DOS. In (c), an oxygen vacant site is indicated with yellow color. S7

8 Figure S10. Simulated absorption spectra of the pristine ReO 3, Re(IV) doped ReO 3, Re(VII) doped ReO 3, and ReO 3 including oxygen vacancy. The absorption of the pristine ReO 3 around nm is very weak, while the MVReO NPs doped heavily with Re(IV) and Re(VII) show enhanced absorption in the visible, which is consistent with the experimental absorption spectra (see Fig. 3a). Figure S11. Calculated DOS profiles. Since the Re(IV)-doped case has an odd number of electrons, the two spin states are different. The Re(IV)- and Re(VII)-doped cases show virtual s-orbital originated DOS. S8

9 Figure S12. Comparison of the Re (VII) impurity s-orbital DOS with the total s-orbital DOS. Unoccupied s-orbital states up to 3.7 ev originate from the impurity s-orbital. S9

10 Section S5. Photocatalytic degradation of methyl orange (MO) by MVReO NPs. Figure S13. Photocatalytic degradation of methyl orange (MO) under visible light or in the dark by TiO 2 (Evonik P25) or MVReO NPs. (a) and (b) give time changes in the absorption spectra of MO in the presence of TiO 2 photocatalyst under dark and under visible light, respectively. (c) and (d) give time changes in the absorption spectra of MO in the presence of MVReO photocatalyst under dark and under visible light, respectively. Numbers in the legends are time in minutes. S10

11 Figure S14. (a) UV/VIS absorption spectrum of TiO 2 and (b) Photodegradation of methyl orange (10-4 M 10mL) under Xe-lamp (300W, output power 100 mw) with the same amounts of like-sized P-25 (red line) or MVReO (black line) nanoparticles present. Figure S15. Raw UV-Vis spectra recorded during irradiation with a Xe-lamp (300W, output power 100mW) for photodegradation of methyl orange (10-4 M 10mL) in the presence of the same amounts of like-sized P-25 (left) or MVReO (right) nanoparticles. Legends specify irradiation times in hours. S11

12 Section S6. Supplementary references: 1. O. Akbulut, Mace, C. R.; Martinez, R. V.; Kumar, Ashok A.; Nie, Z.; Patton, M. R.; Whitesides, G. M., Nano letter, 2012, 12, Biswas, K.; Rao, C. N. R., J. Phys. Chem. B, 2006, 110, Perdew, J.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, Kresse, G.; Joubert, D. Phys. Rev. B 1999, 59, Kresse, G.; Furthmüller, J. Phys. Rev. B, 1996, 54, Hedin, L. Phys. Rev. 1965, 139, A796. S12