Harnessing the Synergy Between Upconverting Nanoparticles and Lanthanide Complexes in a Multi-Wavelength Responsive Hybrid System.

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1 Electronic Supporting Information for: Harnessing the Synergy Between Upconverting Nanoparticles and Lanthanide Complexes in a Multi-Wavelength Responsive Hybrid System. Riccardo Marin, a Ilias Halimi, a Dylan Errulat, a Yacine Mazouzi, a Giacomo Lucchini, b Adolfo Speghini, b Muralee Murugesu a * and Eva Hemmer a,c * a Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada. b Nanomaterials Research Group, Dipartimento di Biotecnologie, Università di Verona, and INSTM, UdR Verona, Strada Le Grazie 15, I Verona, Italy. c Centre for Advanced Materials Research (CAMaR), University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada. Table of content Comparison of the absorption properties of [Tb 2] and [Eu 2] in solution and solid-state 1 Transmission and scanning electron micrographs of the UCNPs + [Tb 2] hybrid system 2 Profilometry of the UCNPs + [Tb 2] hybrid system prepared with a 1:1 ratio and a concentration of 40 mg ml Energy dispersive X-ray spectroscopy (EDX) measurements of the UCNPs + [Tb 2] hybrid system prepared with a 1:1 ratio and a concentration of 40 mg ml Study of the effect of solution concentration on the film morphology 5 Study of the effect of the ratio between UCNPs and [Ln 2] on the film morphology 7 Study of the energy transfer in chloroform 11 Additional hyperspectral imaging of the UCNPs + [Tb 2] hybrid system 12 Hyperspectral imaging of the UCNPs + [Tb 2] hybrid system grown from low-concentration mixture 14 Hyperspectral imaging of the UCNPs + [Eu 2] hybrid system grown from low concentration mixture 15

2 Comparison of the absorption properties of [Tb2] and [Eu2] in solution and solid-state Figure S1. Comparison between absorption (solution), diffuse reflectance (DRS), and excitation spectra (solid-state) of [Eu 2] (A) and [Tb 2] (B). The broad-band features at shorter wavelength (i.e. higher energy) are due to the ligand absorption (S 0 S i). The signals ascribed to direct Ln 3+ photon absorption are marked with dashed vertical lines and assigned to the respective 4f-4f transitions. Passing from a chloroform solution to solid-state (dry form) the ligands energy level experienced a red-shift due to energy stabilization. The different profile featured by DRS and excitation spectra (recorded monitoring the emission at 612 and 547 nm for [Eu 2] and [Tb 2], respectively) arises from the different efficiency of the energy transfer mechanisms that ultimately lead to the population of the emitting level of the respective Ln 3+ ion. S1

3 Transmission and scanning electron micrographs of the UCNPs + [Tb2] hybrid system Figure S2. TEM images of hybrid systems prepared on TEM grids using the same concentration of UCNPs and [Tb 2] (approximately 10 mg ml-1 in a 1:1 ratio) with oleate-coated (A) or ligand-free (B) UCNPs. In the former case the complex crystals grow over a large scale and the UCNPs cover them, assembling in a continuous fashion. Instead, ligand-free UCNPs tend to form separate clusters that do not cover evenly the surface of the substrate, also hindering the growth of [Tb 2] crystals. SEM micrographs (C and D) of the hybrid system presented in A show the presence of large crystals covered by a blanket of UCNPs. Scale bars are 1 µm. S2

4 Profilometry of the UCNPs + [Tb2] hybrid system prepared with a 1:1 ratio and a concentration of 40 mg ml -1. Figure S3. The film obtained from a mixture of UCNPs an [Tb 2] in a 1:1 ratio and a concentration of 40 mg ml -1 had a thickness of approximately 7 ± 2 μm as determined from profilometry scans executed along two orthogonal profiles (i.e. A North-to-South, B West-to-East). S3

5 Energy dispersive X-ray spectroscopy (EDX) measurements of the UCNPs + [Tb2] hybrid system prepared with a 1:1 ratio and a concentration of 40 mg ml -1. Figure S4. The EDX spectrum (A) recorded from a single spot (in B) showed the presence of all the expected elements of which the UCNPs and [Tb 2] are composed. (Na, Gd, F, and Yb from the UCNPs and Tb from [Tb 2]). The signal from Tm could not be detected due to the low doping concentration (0.5 %). The signal from gold is highlighted with an asterisk. The EDX profiles obtained along two different regions of the film (B and C) showed a homogeneous distribution of the elements of interest, confirming the continuous and concomitant presence of the two moieties used to prepare the film. Scale bars in the SEM pictures in B and C are 200 μm. S4

6 Study of the effect of solution concentration on the film morphology Assessing the effect of the starting solution concentration on film morphology, it was found that concentrations below 40 mg ml -1 led to rather discontinuous films (Figure S-3). Fixing the [Tb 2] concentration at 40 mg ml -1 and changing the UCNPs-to-[Tb 2] ratio between 2:1 (Figure S-4), 1:1 (Figure S-5), 1:2 (Figure S-6), and 1:4 (Figure S-7) it was observed that the presence of a higher amounts of UCNPs was required for the formation of a homogeneous and continuous film. However, at a ratio of 2:1 the emission of the complex became quite dim. Overall, the best tradeoff in terms of film homogeneity, upconverted light emission, and UV- and NIR-triggered [Tb 2] emission was realized with a 1:1 ratio (despite the scattering in this film, as inferred by the recorded absorption spectrum). Altogether, this evidence suggests that the UCNPs interact with the complex during the drying process and that they play a major role in controlling the morphology of the composite: when lowering the UCNPs amount, the complex aggregated and formed preferentially large crystals instead of distributing evenly throughout the film. As such, passing from the lowest to the highest tested UCNPs content, the rim of the films became smoother and lesser complex accumulated at the boundaries of the film. S5

7 Figure S5. Concentration effect on the formation of hybrid films: the concentration of the UCNPs/[Tb2] solutions was between 40 and 5 mg ml-1 (for each moiety), while the UCNPs-to-[Tb2] ratio was kept constant (1:1). Photographs of the different films (A) and corresponding absorption spectra (B). Bright field and UV-excited photomicrographs taken on three different spots (indicated in A) of the film (C). For the sake of comparison, the excitation power and exposure time were kept constant when acquiring the photomicrographs under UV illumination. Scale bars in C are 100 μm. S6

8 Study of the effect of the ratio between UCNPs and [Ln2] on the film morphology Figure S6. Hybrid system film obtained using a solution an UCNPs-to-[Tb 2] ratio of 2:1 ([Tb 2] concentration: 40 mg ml -1 ). Bright field (A) and UV-excited (B) photomicrographs taken on six different spots of the film (C). Absorption spectrum of the film (D). Magnification of the film along with the marked spots from where the photomicrographs were acquired (E). At each spot, spectra under UV (F) and 980 nm (G) excitation were recorded. The optical performance of the film was evaluated considering: (H) the ratio between the emission of [Tb 2] under UV (direct) and NIR (indirect) excitation, and (I) the ratio between the indirectly excited [Tb 2] emission and thulium upconverted blue emission. The spectral ranges used for the integration of the emissions are shown in (F) and (G) as shaded areas in dark green ([Tb 2] direct excitation), light green ([Tb 2] indirect excitation), and blue (Tm). Scale bars in A and B are 100 μm. Dashed lines in F and G are drawn in correspondence of the same absolute intensity value (7000 a.u.). S7

9 Figure S7. Hybrid system film obtained using a solution an UCNPs-to-[Tb 2] ratio of 1:1 ([Tb 2] concentration: 40 mg ml -1 ). Bright field (A) and UV-excited (B) photomicrographs taken on six different spots of the film (C). Absorption spectrum of the film (D). Magnification of the film along with the marked spots from where the photomicrographs were acquired (E). At each spot, spectra under UV (F) and 980 nm (G) excitation were recorded. The optical performance of the film was evaluated considering: (H) the ratio between the emission of [Tb 2] under UV (direct) and NIR (indirect) excitation, and (I) the ratio between the indirectly excited [Tb 2] emission and thulium upconverted blue emission. The spectral ranges used for the integration of the emissions are shown in (F) and (G) as shaded areas in dark green ([Tb 2] direct excitation), light green ([Tb 2] indirect excitation), and blue (Tm). Scale bars in A and B are 100 μm. Dashed lines in F and G are drawn in correspondence of the same absolute intensity value (7000 a.u.). S8

10 Figure S8. Hybrid system film obtained using a solution an UCNPs-to-[Tb 2] ratio of 1:2 ([Tb 2] concentration: 40 mg ml -1 ). Bright field (A) and UV-excited (B) photomicrographs taken on six different spots of the film (C). Absorption spectrum of the film (D). Magnification of the film along with the marked spots from where the photomicrographs were acquired (E). At each spot, spectra under UV (F) and 980 nm (G) excitation were recorded. The optical performance of the film was evaluated considering: (H) the ratio between the emission of [Tb 2] under UV (direct) and NIR (indirect) excitation, and (I) the ratio between the indirectly excited [Tb 2] emission and thulium upconverted blue emission. The spectral ranges used for the integration of the emissions are shown in (F) and (G) as shaded areas in dark green ([Tb 2] direct excitation), light green ([Tb 2] indirect excitation), and blue (Tm). Scale bars in A and B are 100 μm. Dashed lines in F and G are drawn in correspondence of the same absolute intensity value (7000 a.u.). S9

11 Figure S9. Hybrid system film obtained using a solution an UCNPs-to-[Tb 2] ratio of 1:4 ([Tb 2] concentration: 40 mg ml -1 ). Bright field (A) and UV-excited (B) photomicrographs taken on six different spots of the film (C). Absorption spectrum of the film (D). Magnification of the film along with the marked spots from where the photomicrographs were acquired (E). At each spot, spectra under UV (F) and 980 nm (G) excitation were recorded. The optical performance of the film was evaluated considering: (H) the ratio between the emission of [Tb 2] under UV (direct) and NIR (indirect) excitation, and (I) the ratio between the indirectly excited [Tb 2] emission and thulium upconverted blue emission. The spectral ranges used for the integration of the emissions are shown in (F) and (G) as shaded areas in dark green ([Tb 2] direct excitation), light green ([Tb 2] indirect excitation), and blue (Tm). Scale bars in A and B are 100 μm. Dashed lines in F and G are drawn in correspondence of the same absolute intensity value (7000 a.u.). S10

12 Study of the energy transfer in chloroform Figure S10. Study of the energy transfer from UCNPs to [Tb 2] in a chloroform mixture of the moieties. Tm 3+ emission at 362 nm ( 1 D 2 3 H 6) is not detectable with the experimental setup employed for the study. Nonetheless, this transition is expected to play the major role in the transfer mechanism like in the solid-state hybrid system, due to its overlap with the excitation spectrum of the complex (recorded monitoring the 547 nm emission of Tb 3+ ). Tm 3+ 1 D 2 3 F 4 band is quenched (approx. 12%) to an extent that depends on the amount of [Tb 2] complex introduced in the mixture. The different profile of the excitation and absorption spectra of the complex stems from the different efficiency of the energy transfer mechanisms that follows a photon absorption from the ligands to populate the emitting level of Tb 3+. S11

13 Additional hyperspectral imaging of the UCNPs + [Tb2] hybrid system Figure S11. Hyperspectral mapping of additional ROIs of a newly prepared hybrid film (UCNPs+[Tb 2], concentration: 40 mg ml -1, ratio 1:1). Photomicrographs of the film under white and UV light illumination (A, E, I) along with ROI over which spectral maps (B, F, J) were obtained S12

14 (λ ex = 980 nm). Tm 3+ and indirectly triggered Tb 3+ emissions were monitored over an area of approximately 20 x 20 μm 2. The absolute intensities of the emission bands for both UCNPs and the complex remained relatively constant within each ROI. It is to be mentioned that this film was prepared from a different batch of sub-10-nm UCNPs. Hence, the slight deviation of the ratio between the complex vs Tm 3+ : 1 G 4 3 H 6 (squares) and Tm 3+ : 1 G 4 3 F 4 vs Tm 3+ : 1 G 4 3 H 6 integrated emissions (circles) from the ones reported in Figure 5C and 5D is a consequence of unavoidable batch-to-batch variability in the properties of the UCNPs. Scale bars are 20 μm in the photomicrographs and 5 μm in ROI and spectral maps. S13

15 Hyperspectral imaging of the UCNPs + [Tb2] hybrid system grown from lowconcentration mixture Figure S12. Results of the hyperspectral mapping of the hybrid system obtained from the low concentration (5 mg ml -1 ) mixture of UCNPs and [Tb 2]. Photomicrographs for the hybrid system under white and UV light illumination along with the region of interest (ROI) (A) over which spectral maps under 980 nm light irradiation were obtained (B). Tm 3+ and indirectly triggered Tb 3+ emissions were monitored over an area of approximately 20 x 20 μm 2. The absolute intensity of the emission bands for both UCNPs and the complex are maximum in correspondence of the needle-like crystals (C spots 1 and 2). This, along with the constancy of the ratio between the integrated emission of the complex vs Tm 3+ : 1 G 4 3 H 6 transition (squares) and Tm 3+ : 1 G 4 3 F 4 vs Tm 3+ : 1 G 4 3 H 6 (circles) confirms the simultaneous presence of both moieties throughout the hybrid system and the interaction between them (D). Scale bars are 20 μm in the photomicrographs and 5 μm in ROI and spectral maps. S14

16 Hyperspectral imaging of the UCNPs + [Eu2] hybrid system grown from low concentration mixture Figure S13. Hyperspectral mapping of the hybrid system obtained from the low concentration (5 mg ml -1 ) mixture of UCNPs and [Eu 2]. Photomicrographs for the hybrid system under white and UV light illumination along with the region of interest (ROI) (A) over which spectral maps under 980 nm light irradiation were obtained (B). Tm 3+ and indirectly triggered Eu 3+ emissions were monitored over an area of approximately 20 x 20 μm 2. The absolute intensity of the emission bands for both UCNPs and the complex are maximum in correspondence of the needle-like crystals (C spots 1, 2 and 3). This, along with the constancy of the ratio between the integrated emission of the complex vs Tm 3+ : 1 G 4 3 H 6 transition (squares) and Tm 3+ : 1 G 4 3 F 4 vs Tm 3+ : 1 G 4 3 H 6 (circles) confirms the simultaneous presence of the two moieties through the hybrid system and the interaction between them (D). Scale bars in the photomicrographs are 20 μm and in ROI and spectral maps are 5 μm. S15