UV-vis and fluorescence spectroscopy

UV-vis spectroscopy was performed on an Agilent Cary 50 instrument connected to a cryostat from Quantum Northwest, Modell Luma 40 (temperature accuracy ±0.15 K) in 10 × 10 mm quartz cuvettes with 3 mL volume. Fluorescence spectra were recorded on a Varian Cary Eclipse Fluorescence Spectrometer and corrected for variations in wavelength dependent photomultiplier response using correction curves generated on the instrument. For all spectroscopy experiments, non-degassed solvents of spectroscopy grade were used.

Fluorescence quantum yields (φF) were determined according to:

the subscripts X and Ref denote unknown samples and references, m depicts the slope from the linear fit of integrated fluorescence intensity versus 1−10Abs(λexc) at the excitation wavelength (which was kept constant for the sample and reference), and η is the refractive index of the used solvents. Rhodamine 101 in ethanol was used as reference (φF = 0.91).³⁹

The fluorescence quantum yields for DiI-CT and DiI are 0.32 in benzene and 0.10 in ethanol at 25°C. The value for DiI in ethanol is in accordance with the literature.⁴⁰