as well as a CPL signal could be detected in the co-gel. Additionally, if the co-gel
was exposed to an ammonia atmosphere, both fluorescence and CPL could be
switched off. Therefore, this co-gel system achieved a dual switch of fluorescence
and CPL (Fig. 11.16a). Because of protonation by acetic acid, the co-gel showed
strong fluorescence when under excitation at 447 nm. Meanwhile, CPL was
also detected, as verified by the mirror image CPL spectra in Fig. 11.16b. As
shown in Fig. 11.16c, when the L-15/PBI film was exposed to HCl atmosphere,
appearing the fluorescence and CPL curve. However, if exposing the film to an
ammonia atmosphere, the fluorescence and CPL will be wiped out. The g lum value
showed stable repeatability after several cycle treatments. Therefore, a chiroptical
switch based on acid–base exposure regulated could be fabricated.
In the co-assembly system, gelator with photochromic properties could also
construct the CPL switch. As illustrated in Fig. 11.17, a photo-switched nanostructure, formed by photosensitive cinnamic acid derivatives (L- or D-16) through
self-assembly, can successfully change from superhelix to nanokebab by light
irradiation, resulting from the dimerization of cinnamic acid. Meanwhile, the supramolecular chirality could be reversed [39]. Furthermore, fluorescent achiral dyes (CBS)
could embed into these helical nanostructures and induced chirality was observed
as well as CPL properties. These nanohelixes could turn into nanokebabs by irradiated
with UV light (365 nm), and both the inversion of helicity and CPL were observed.
Interestingly, the handedness of CPL showed that following the supramolecular
chirality of the nanoassemblies rather than the intrinsic molecular chirality. Based
Fig. 11.15 (a) Schematic representation of chiral nanotubes formed by L-/D-14 encapsulated
different AIE luminophores. (b) The photograph of AIEgens-loaded co-gels under UV light
irradiation. (c) Mirror image CPL spectra of TPE (λ ex ¼ 300 nm), HPS (λ ex ¼ 365 nm), β-DCS
(λ ex ¼ 354 nm), α-DCS (λ ex ¼ 363 nm), MeCNS (λ ex ¼ 376 nm), BuCNS (λ ex ¼ 376 nm) in L-14
(solid lines) or D-14 (dash lines) host gels; all the co-gel samples were made in DMSO/H 2 O (1/1,
v/v) mixing solvents. Reproduced with permission [37]. Copyright 2017, Wiley-VCH
11 Circularly Polarized Luminescence from Gelator Molecules: From Isolated. . .
267
was exposed to an ammonia atmosphere, both fluorescence and CPL could be
switched off. Therefore, this co-gel system achieved a dual switch of fluorescence
and CPL (Fig. 11.16a). Because of protonation by acetic acid, the co-gel showed
strong fluorescence when under excitation at 447 nm. Meanwhile, CPL was
also detected, as verified by the mirror image CPL spectra in Fig. 11.16b. As
shown in Fig. 11.16c, when the L-15/PBI film was exposed to HCl atmosphere,
appearing the fluorescence and CPL curve. However, if exposing the film to an
ammonia atmosphere, the fluorescence and CPL will be wiped out. The g lum value
showed stable repeatability after several cycle treatments. Therefore, a chiroptical
switch based on acid–base exposure regulated could be fabricated.
In the co-assembly system, gelator with photochromic properties could also
construct the CPL switch. As illustrated in Fig. 11.17, a photo-switched nanostructure, formed by photosensitive cinnamic acid derivatives (L- or D-16) through
self-assembly, can successfully change from superhelix to nanokebab by light
irradiation, resulting from the dimerization of cinnamic acid. Meanwhile, the supramolecular chirality could be reversed [39]. Furthermore, fluorescent achiral dyes (CBS)
could embed into these helical nanostructures and induced chirality was observed
as well as CPL properties. These nanohelixes could turn into nanokebabs by irradiated
with UV light (365 nm), and both the inversion of helicity and CPL were observed.
Interestingly, the handedness of CPL showed that following the supramolecular
chirality of the nanoassemblies rather than the intrinsic molecular chirality. Based
Fig. 11.15 (a) Schematic representation of chiral nanotubes formed by L-/D-14 encapsulated
different AIE luminophores. (b) The photograph of AIEgens-loaded co-gels under UV light
irradiation. (c) Mirror image CPL spectra of TPE (λ ex ¼ 300 nm), HPS (λ ex ¼ 365 nm), β-DCS
(λ ex ¼ 354 nm), α-DCS (λ ex ¼ 363 nm), MeCNS (λ ex ¼ 376 nm), BuCNS (λ ex ¼ 376 nm) in L-14
(solid lines) or D-14 (dash lines) host gels; all the co-gel samples were made in DMSO/H 2 O (1/1,
v/v) mixing solvents. Reproduced with permission [37]. Copyright 2017, Wiley-VCH
11 Circularly Polarized Luminescence from Gelator Molecules: From Isolated. . .
267