Ultrastrong Red Circularly Polarized Luminescence Promoted from Chiral Transfer and Intermolecular Förster Resonance Energy Transfer in Ternary Chiral Emissive Nematic Liquid Crystals

Abstract

Chiral emissive liquid crystals (N*-LCs) have been proved to greatly amplify the circularly polarized luminescence (CPL) signals due to highly regular spiral arrangement of dyes in a well-organized liquid crystals system. Normally, CPL materials with a high luminescence dissymmetry factor (g lum) and quantum yield (QY) can meet the real application requirement. Here, four chiral aggregate-induced emission (AIE) active donors (Guests A1–A4: R-C2, R-C4, R-C6, R-C8, chiral dopant, and energy donor) and achiral AIE-active acceptors (Guest B: PBCy, CPL emitter) were doped into the commercial nematic liquid crystals E7 (N-LCs, Host) to form CPL-active ternary chiral emissive N-LCs (T-N*-LCs), respectively. This kind of T-N*-LCs could emit strong red CPL with QY = 16.56% and g lum up to 1.51 through intermolecular energy transfer and chirality induction from the supramolecular self-assembly of T-N*-LCs. This work provides the effective strategy for the development of high g lum CPL materials.

Frontiers in circularly polarized luminescence: molecular design, self-assembly, nanomaterials, and applications

“…In the past several years, there have been more and more reports on chiral emissive liquid crystals (N*-LCs) as CPL-active materials. These materials can self-assemble as highly regular helical arrangement in LC medium after annealing treatment as a result of the LC-templated molecular reorientation, which is beneficial for the enlarged effect of the induced CPL signals [101][102][103][104][105][106][107]. In 2020, Cheng's group [101] realized the recyclable CPL response behavior in N*-LCs doped with the axially chiral molecules (R/S)-37 (Figure 12a).…”

Full‐Color and White Circularly Polarized Luminescence Promoted by Liquid Crystal Self‐Assembly Containing Chiral Naphthalimide Dyes

“…The high QY values of N*‐LCs could be due to the limited free motion of the benzene rings from fluorine, triphenylethylene, and TPE moieties in high viscosity E7 (29 cp), which can lead to nonradiation transition. [ 27 ] Compared with the emission of R‐ N*‐LCs‐1a‐1c, S‐ N*‐LCs‐2a‐2c possessed about 10–20 nm red‐shift (Figure 4b) similar to DCM solutions or cast films. We think this kind of intramolecular hydrogen bond in D‐A type S‐ 2a‐2c can be still kept in LCs E7 medium.…”

“…[ 26 ] Recently, ultrastrong CPL response (QY = 16.56%, g em = 1.51) was observed from achiral AIE‐active dye through intermolecular energy transfer and chirality induction mechanism between chiral AIE‐active donors and achiral AIE‐active acceptor, which further demonstrates highly regular spiral arrangement of dyes could promote chirality enlargement in well‐organized LCs system. [ 27 ]…”

Multi‐Light‐Responsive Upconversion‐and‐Downshifting‐Based Circularly Polarized Luminescent Switches in Chiral Metal–Organic Frameworks

“…Energy‐transfer‐amplified CPL has been reported in certain organic systems. [ 63,67,68 ] However, this is the first example of an energy‐transfer‐amplified CPL in an organic–inorganic complex system based on the photon UC process. These results will assist in expanding strategies for fabricating high‐performance CPL‐active materials.…”