Fluorescence upconversion properties of a chiral polybinaphthyl induced by two‐photon absorption

Abstract

ABSTRACT:The fluorescence properties of a chiral polymer based on optically active polybinaphthyls were studied in tetrahydrofuran solution. One-photon excited fluorescence of the polymer was located in the range of $ 596 nm and the corresponding lifetime was $ 4.38 ns. From the excitation spectra and emission spectra excited at 800 nm, the upconversion fluorescence emission was observed. When excited by using 800 nm fs laser pulses with different input irradiances, the peak fluorescence intensity of the solution provides square dependence with the input irradiance power, giving an evidence for two-photon excited fluorescence. Furthermore, open aperture Z-scan measurements were performed at different irradiation intensities to confirm two-photon absorption property of the solution at 800 nm excitation.

Relationships between main-chain chirality and photophysical properties in chiral conjugated polymers

“…21,22 In addition, the changeable dihedral angle from 60 to 120 between the two bulky naphthyl groups of the non-planar binaphthyl offers a feasible way to control the effective conjugation length, and thus the emission color of the conjugated polymer chain without the need to insert an additional bandgap adjusting unit. 23 As a result, binaphthyl-based conjugated polymers have found impressive applications in optoelectronics, such as in organic light emitting diodes (OLEDs), 24 transistors, 25 non-linear optics, 26,27 and solar cells. 28 In the above research elds of conjugated polymers, however, the effects of chirality on the optoelectronic properties have been less addressed and R-binaphthyls were used in most reports because it is widely believed that the stereo conformations of the R-and S-enantiomers have identical or symmetric optical and electronic properties in symmetric environments.…”