Fluorescence and Phosphorescence Anisotropy from Oriented ... The gel was then poured into an ice-cold petri-dish and dried at room temperature for 24 hours ...
Supporting information
Fluorescence and Phosphorescence Anisotropy from Oriented Films of Thermally Activated Delayed Fluorescence Emitters. Heather F. Higginbotham, Marc. K. Etherington, Andrew P. Monkman* Department of Physics, Durham University, South Road. DH1 3LE. UK
Contents Experimental procedures Absorbance spectra of TADF materials in PE film Anisotropy of 2,8-DPTZ-DBTO2 and 3,7-DPTZ-DBTO2 in solution Anisotropy of 2,8-DPTZ-DBTO2 and 3,7-DPTZ-DBTO2 in an un-stretched film Anisotropy versus film stretch direction 2-PTZ-DBTO2 transition dipole moments determined by fluorescence polarisation spectroscopy Time-resolved polarisation spectra of Ren5 at different film positions
Experimental Procedures Synthesis Synthesis of 2,8-DPTZ-DBTO2 The synthetic procedure of 2,8-DPTZ-DBTO2 can be found within literature.1 Synthesis of 3,7-DPTZ-DBTO2 The synthetic procedure of 2,8-DPTZ-DBTO2 can be found within literature.2 Synthesis of 2-DPTZ-DBTO2 The synthetic procedure of 2,8-DPTZ-DBTO2 can be found within literature.3
Experimental Methods Steady state polarisation spectroscopy Fluorescence polarisation spectroscopy uses polarised excitation light to selectively excite those molecules with an absorption dipole in line with the vector of the incoming light. Emission is then collected through a second polariser, which is set either to the same polarisation (conventionally vertical-Ivv) as the excitation beam or perpendicular (horizontalIvh) to the beam. The difference between the intensity collected with vertical and horizontal polarisation is used to determine the change between the absorption and emission dipole moments, resulting in the determination of anisotropy. The G factor was determined following our previous literature procedure.4,5 using 9,10-diphenylanthracene (DPA) and 4(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) in dilute solution.
Fluorescence polarisation spectra were taken on a Jobin Yvon Horiba Fluorolog 3, calibrated for detector efficiency using company supplied, instrument specific calibration files. The instrument’s L shaped- configuration accommodates 2 polarisers; one on the excitation and one on the emission side of the sample, to produce both polarised excitation (0 °, vertical polarisation used) and to detect a change in polarisation upon passing through the sample. Time-resolved polarisation spectroscopy Time-resolved polarisation spectroscopy was performed by exciting the sample with a Nd:YAG laser (EKSPLA), 10 Hz, 355 nm. The vertically polarised emission output was passed through a UV polariser (0 o) before being directed to the sample, held under vacuum in a cryostat. Sample emission was directed through a second visible light polariser (400-800 nm) and onto a spectrograph and gated iCCD camera (Stanford Computer Optics). Spectra taken at different delay times, with modulation of the emission polariser were used to determine anisotropy from different excited states. Polyethylene film preparation To induce alignment into samples, transparent stretchable films were prepared from stirring 120 mg/mL of ultra-high molecular weight polyethylene film (PE) and the emitting material in o-xylene (Analytical grade, Sigma Aldrich) at 140 °C for 30 minutes or until gelation was obtained. The gel was then poured into an ice-cold petri-dish and dried at room temperature for 24 hours before being peeled from the dish. Films were then placed on a hot plate at 100 °C and manually stretched to the desired stretch ratio. Stretch ratio was determined to be the length of the stretched material divided by the initial length of the film. The un-stretched films were estimated to be approximately a few 100 µm thick, while stretched films
(stretched to a minimum of 10 times their original length) were estimated to be at least half the thickness. The prepared films were held in an in-house sample holder that allows for 360 ° in-plane rotation. Stretched films were placed in the sample holder with their stretch directions aligned with the vertical polarisation. This film orientation was assigned as 0 o. Rotation of the film in-plane to where the film is placed with the stretch direction horizontal to the vertical polarisation with assigned as 90o.
Absorbance spectra of TADF materials in PE film a)
b)
c)
Figure S1: Absorbance spectrum of PE film containing 1% w/w a) 2,8-DPTZ-DBTO2 b) 3,7DPTZ-DBTO2 c) 2-DPTZ-DBTO2
Anisotropy of 2,8-DPTZ-DBTO2 and 3,7-DPTZ-DBTO2 in solution a)
b)
Figure S2: Dilute solution of 10 μM a) 2,8-DPTZ-DBTO2 b) 3,7-DPTZ-DBTO2 excited at 370 nm in toluene. Note: The normalised emission spectrum is added in black for clarity
Anisotropy of 2,8-DPTZ-DBTO2 and 3,7-DPTZ-DBTO2 in an un-stretched film a)
b)
Figure S3: Un-stretched film of 1% a) 2,8-DPTZ-DBTO2 b) 3,7-DPTZ-DBTO2 excited at 370 nm. Note: The normalised emission spectrum is added in black for clarity
Anisotropy versus film stretch direction a)
b)
Figure S4: Anisotropy versus film stretch direction in a stretch film containing 1% 2-DPTZDBTO2 a) 430 nm (emission from the 1LE state) b) 570 nm (emission from the 1CT state)
2-PTZ-DBTO2 transition dipole moments determined by fluorescence polarisation spectroscopy
Figure S5: Transition dipole moments of 1LE (blue), 1CT (yellow) and 3LE (green) as determined by fluorescence polarisation spectroscopy of 2-PTZ-DBTO2.
Time-resolved polarisation spectra of Ren5 at different film positions
Figure S6: Time-resolved anisotropy of 1% 2-PTZ-DBTO2 stretched film excited at 355 nm at 3µs (black spectra) and 200 μs (purple spectra) with anisotropy () recorded at 0 o (dark grey line- 3 µs, dark purple line-200 µs) and 90 o (light grey line- 3 µs , pink line 200 µs) film alignment. *The monotone lines (black, grey) refer to data recorded at 3 µs relating to the TADF emission from the 1CT state. The pink/purple lines refer to data recorded at 200 µs, relating to phosphorescence emission from the 3LE state. The identity of these states was previously outlined in literature.3
References
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