Supporting Information
Cage Effect in Poly (alkyl-methacrylate) Thin Films Studied by Nile Red Single Molecule Fluorescence Spectroscopy Beatriz Araoz1, Daniela Täuber2, Christian von Borczyskowski2* and Pedro F. Aramendía1*
1
INQUIMAE and Departamento de Química Inorgánica, Analítica y Química Física.
Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Pabellón 2. Ciudad Universitaria. C1428EHA. Buenos Aires 2
Optical Spectroscopy and Molecular Physics Group, Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany
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Figure 1 SI: Accumulated spectra (dots) of all measured single molecules and the ensemble spectrum (solid line) measured in a fluorometer for a NR sample in (A) PMMA film of 200 nm thickness at 296 K and (B) PBMA film of 25 nm thickness at 323 K. Spectra were collected at the same excitation wavelength, thickness and temperature but different concentration. [NR] (Ensemble) = 1x10-5 mol NR/kg polymer and [NR] (Accumulated) = 1x10-12 mol NR/kg polymer.
Table 1 SI: Summary of literature data of NR emission maximum, either in wavelength or in wavenumber, in different solvents together with the corresponding fluorescence energy and the polarity scale ET(30).
Solvent n-hexane
ET(30)10 Reported Value 31.0
Energy Value [eV]
Ref.
19050 cm
-1
2.36
6
-1
2.36
8
n-hexane
31.0
19000 cm
n-dodecane
31.1
531 nm
2.33
1
n-heptane
31.1
529 nm
n-heptane cyclohexane
31.1 31.2
2.34
1
19047 cm
-1
2.36
2
18484 cm
-1
2.29
2
-1
2.33
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cyclohexane carbon tetrachloride carbon tetrachloride carbon tetrachloride
31.2
18750 cm
32.5
17985 cm-1
2.23
2
32.5
17985 cm-1
2.23
2
32.5
18200 cm-1
2.25
6
xylene
33.1
565 nm
2.19
1
toluene
33.9
17574 cm-1
2.18
2
toluene
33.9
570 nm
2.18
4
toluene
33.9
570 nm
2.17
5
2
1,4-dioxane
36.0
17152 cm-1
2.13
2
THF
37.4
16806 cm-1
2.08
2
chloroform
39.1
595 nm
chloromethane
39.1
2.08
1
16800 cm
-1
2.05
6
-1
2.06
2
dichloromethane
40.7
16638 cm
dichloromethane
40.7
16600 cm-1
2.06
6
ethyl acetate
41.1
16806 cm-1
2.08
2
acetone
42.2
608 nm
2.04
1
2.05
2
-1
acetone
42.2
16556 cm
acetone
42.2
615 nm
2.02
3
DMSO
45.1
15898 cm-1
1.97
2
DMSO
45.1
637 nm
1.95
4
DMSO
45.1
650 nm
1.91
5
1.95
6
1.95
3
2.01
2
-1
DMSO
45.1
15800 cm
DMSO
45.1
635 nm -1
acetonitrile
46.0
16260 cm
acetonitrile
46.0
627 nm
1.98
3
acetonitrile
46.0
610 nm
2.03
9
2-propanol
48.4
628 nm
1.97
3
1.97
2
-1
1-butanol
49.7
15923 cm
1-butanol
49.7
633 nm
1.96
3
ethanol
51.9
650 nm
1.91
5
ethanol
51.9
629 nm
1.97
1
1.95
2
-1
ethanol
51.9
15748 cm
ethanol
51.9
635 nm
1.95
3
ethanol
51.9
637 nm
1.95
4
methanol
55.5
15576 cm-1
1.93
2
methanol
55.5
642 nm
1.93
3
methanol
55.5
625 nm
1.98
7
1.96
8
-1
methanol
55.5
15800 cm
ethylene glycol
56.3
654 nm
1.90
4
ethylene glycol
56.3
652 nm
1.90
3
glycerol
57.0
654 nm
1.90
4
water
63.1
657 nm
1.89
1
1.86
2
1.86
3
-1
water
63.1
15037 cm
water
63.1
665 nm
3
Figure 2 SI: Solvatochromic plot correlating energy maximum of NR emission in different solvents as a function of ET(30). The two linear correlations are indicated for the emission energy in eV and correspond: circles, solvents with ET(30) < 36; triangles, solvents with ET(30) > 36.
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Figure 3 SI: Schematic representations of polar and non-polar environments for NR location in PBMA or PPMA and comparison with non-polar environment in hexane (lower right scheme) and in chloroform (lower left scheme) as representative liquid environments for type A and B-C emission spectra, respectively.
Figure 4 SI: Time traces of emission energy for (left) a simulated system with two exchangeable conformations with distinctive emission energies and for (middle) a single molecule experimentally observed in a PBMA film of 200 nm thickness at 278 K.
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The logarithm (right) of the complementary cumulative distribution function, Φc(∆E2), for the left panel (black triangles) and the central panel (hollow circles).
Figure 5 SI: Φc(∆E2) of type A SM spectral fluctuations of NR embedded in PBMA (left column) and PPMA (right column) of 200 nm and 25 nm thickness. Hollow circles: 278 K, hollow squares: 296 K and hollow triangles: 323 K.
Figure 6 SI: Position of the emission maximum in successive frames of all the type A emitting molecules measured in 25 nm PBMA at 323 K and the corresponding assignment to A or B type emission with 2.37 eV as the threshold value.
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