Transfer of Chiral Information from Silica Hosts to Achiral Luminescent Guests: a Simple Approach to Accessing Circularly Polarized Luminescent Systems

Abstract

Systems that show circularly polarized luminescence (CPL) are usually constructed in one of two possible ways: either covalently binding the chiral moieties (usually organic compounds) to luminophores (inorganic or organic compounds) or associating the luminophores as guests with chiral hosts (usually organic compounds). Herein, we propose inorganic‐based CPL‐active systems constructed by the “chiral host‐luminescent guest” strategy, in which silica acts as a chiral host to endow various luminescent guests with CPL. The chiral silica was modified by silane coupling with amino or phenyl groups to allow interaction with luminescent guests, and then used in combination with acidic achiral dyes, lead‐halide type perovskites, and aggregation‐induced emission luminogens (AIEgens). Interestingly, when these achiral guests were noncovalently confined in surface‐modified chiral silica, the guests showed chiroptical behavior in the circular dichroism (CD) spectra, and thus became CPL active, even though they are not inherently chiral. The surface functional groups on the silica play very important roles in transferring the chiral information from the silica to the guests. This work provides a new concept for constructing CPL‐active systems using inorganic materials as a chiral source.

Template-assisted self-assembly of achiral plasmonic nanoparticles into chiral structures

“… 114 Another example is the use of chiral silica grown onto complexes of polyethyleneimine–tartaric acid as a backbone, which allowed binding, complexation or in situ formation of different types of achiral emitters that became CD- and CPL-active. 115 Chirality transfer to achiral luminogens has been demonstrated by the use of a wide range of chiral templates, including gels made of supramolecular assemblies 116 and chiral smectic liquid crystal phases, 117 as well as metal–organic frameworks. 118 Once incorporated and organized within the chiral template, the achiral chromophores display CPL.…”

Endowing inorganic nanomaterials with circularly polarized luminescence

“…[ 65 ] Kawai et al., constructed the nanofiber‐based chiral silica systems with CPL activity to endow inorganic luminescent achiral guests such as lead‐halide type perovskites with CPL feature. [ 66 ] Zhao's group recently constructed a spirocyclic nonnuclear silver cluster compound by sharing the vertices of the two in‐situ generated heteroaryl diide‐centered metal rings. The core‐peripheral type clusters form micrometer‐long nanofibers along with strong CPL ( g lum = 0.16) under the different assembly processes.…”

A versatile messenger for chirality communication: asymmetric silica framework

“…A first example is to prepare sub-10 nm fluorescent lanthanide oxide NPs on SiO 2 nanofibers. Eu 3+ (or Tb 3+ ) ions absorbed by PEI/tart@SiO 2 are transformed into sub-10 nm crystalline Eu 2 O 3 (or Tb 2 O 3 ) NPs after calcination at 900 °C [Figure 9A] [51] . Around the characteristic emission bands of lanthanide ions (615 nm for Eu 2 O 3 and 545 nm for Tb 2 O 3 ), the positive CPL signals (i.e., I L > I R ) of these NPs on L-SiO 2 appear, while negative signals (i.e., I L < I R ) occur on D-SiO 2 [Figure 9B].…”