Controlling Circularly Polarized Luminescence Using Helically Structured Chiral Silica as a Nanosized Fused Quartz Cell

Abstract

Circularly polarized luminescence (CPL) is typically achieved with a chiral luminophore. However, using a helical nanosized fused quartz cell consisting of chiral silica, we could control the wavelength and helical sense of the CPL of an achiral luminophore. Chiral silica with a helical nanostructure was prepared by calcining a mixture of polyhedral oligomeric silsesquioxane (POSS)-functionalized isotactic poly(methacrylate) (it-PMAPOSS) and a small amount of chiral dopant. The chiral silica encapsulated functional molecules, including luminophores, along the helical nanocavity, leading to induced circular dichroism (ICD) and induced circularly polarized luminescence (iCPL). Because chiral silica can act as a helical nanosized fused quartz cell, it can encapsulate not only the luminophore but also solvent molecules. By changing the solvent in the luminophore-containing nanosized fused quartz cell, the wavelength of the CPL was controlled. This method provides an effective strategy for designing novel CPL-active materials.

Figure 1

(a) Chemical structure of it-PMAPOSS. (b) TEM image of chiral silica prepared from (R)-BN. The inset shows a highly magnified image. (c) VCD spectra of chiral silica prepared from it-PMAPOSS with enantiomeric BN.

Figure 2

(a–c) ECD spectra of (a) chiral silica/phenol, (b) chiral silica, and (c) phenol measured in MeOH/H₂O solution. (d, e) Highly magnified UV–vis spectra of chiral silica/phenol and phenol in MeOH/H₂O solution. (f) Schematic of the J-aggregation state of phenol in a chiral silica helical nanocavity.

Figure 3

(a) Chemical structure of pyranine. (b) Photographs of chiral silica/pyranine in MeOH (left) and H₂O (right) upon UV irradiation at 340 nm. (c) CPL and corresponding PL spectra of chiral silica associated with pyranine under excitation at 340 nm.

Figure 4

(a) g_lum spectra of S-silica/pyranine in MeOH and H₂O upon UV irradiation at 340 nm. (b) CPL and corresponding PL spectra of dry-state chiral silica associated with pyranine under excitation at 340 nm.