Tunable Circularly Polarized Luminescence via Chirality Induction and Energy Transfer from Organic Films to Semiconductor Nanocrystals

Abstract

Circularly polarized luminescent (CPL) films with high dissymmetry factors hold great potential for optoelectronic applications. Herein, we propose a strategy for achieving strongly dissymetric CPL in nanocomposite films based on chirality induction and energy transfer to semiconductor nanocrystals. First, focusing on a purely organic system, aggregation-induced emission (AIE) and CPL activity of organic liquid crystals (LCs) forming helical nanofilaments was detected, featuring green emission with high dissymmetry factors g lum ∼ 10 −2 . The handedness of helical filaments, and thus the sign of CPL, was controlled via minute amounts of a small chiral organic dopant. Second, nanocomposite films were fabricated by incorporating InP/ZnS semiconductor quantum dots (QDs) into the LC matrix, which induced the chiral assembly of QDs and endowed them with chiroptical properties. Due to the spectral matching of the components, energy transfer (ET) from LC to QDs was possible enabling a convenient way of tuning CPL wavelengths by varying the LC/QD ratio. As obtained, composite films exhibited absolute g lum values up to ∼10 −2 and thermally on/off switchable luminescence. Overall, we demonstrate the induction of chiroptical properties by the assembly of nonchiral building QDs on the chiral organic template and energy transfer from organic films to QDs, representing a simple and versatile approach to tune the CPL activity of organic materials.

Reflection-influenced circularly polarised luminescence in dye-embedded polymer-stabilised cholesteric liquid crystal films

“…2 Therefore, improving the g lum value is regarded as one of the most important challenges in the field of CPL research. 3 Up to now, researchers have developed various strategies, 4 such as supramolecular self-assembly or co-assembly including liquid crystals (LCs), 1 d ,5 charge and energy transfer, 6 photon upconversion, 7 and helical polymers. 8 Among them, dye-embedded cholesteric LCs (CLCs) have gained much more attention due to their unique optical properties to afford CPL with an incomparably high g lum value, as well as their excellent generality for embedding almost all emitters.…”

Organic chiral nano- and microfilaments: types, formation, and template applications

“…The calculated |g lum | values were one order of magnitude lower than for the AIE dye HPS (|g lum | on the order of 10 À2 ) perhaps due to some degree of luminescence quenching once the QDs decorate the HNFs at QD concentrations reaching up to 8.5 wt%. 187 The examples discussed here in more details are, of course, only emblematic for the wide range of possible or already realized applications for chiral nano-and microfilaments. Not any less noteworthy are applications ranging from sensing 188,189 to (bio)-medical uses.…”

Bottom‐Up Assembly of Inorganic Particle‐Based Chiroptical Materials

“…In a recent work, they employed helical nanofilaments comprising chiral luminophores to achieve CPL via aggregation‐induced emission (AIE). [ 82 ] Co‐assembly of spectrally matched InP/ZnS QDs enabled energy transfer between emissive LCs and QDs. This allowed tailoring CPL wavelength by varying LC/QD ratios ( g CPL ≈10 −2 ).…”