a spontaneous symmetry breaking and the g lum value was Æ0.8 Â 10
À2
, as
shown in Fig. 11.12a. Interestingly, in such a system mechanical stirring could
enhance the g lum values during the supramolecular gelation process (Fig. 11.12b).
In addition, the obtained gel dispersion was quite stable and the CPL remained
even after stopping the stirring. However, the direction of the CPL signals could not
be controlled by the stirring direction. The direction of CPL signals can be readily
regulated by adding some simple chiral dopants (Fig. 11.12c). More interestingly,
the g lum value was also amplified by chiral dopants (Æ 2.3 Â 10
À2 ).
In some cases, the CPL from the nanoassemblies based on achiral molecules showed
a morphology dependence. As illustrated in Fig. 11.13, twisted ribbons, nanobelts
and trumpet-like nanostructures can be formed from an achiral C 3 -symmetric molecule
via the assembly in a mixed DMF/water solvent [35]. At a unity mixing ratio, nanobelts
were observed. Upon increasing the amount of dimethylformamide (DMF), nanotwists
and nanotrumpets were formed by such nanobelts through twisting and rolling,
respectively. Intriguingly, the nanotwists showed supramolecular chirality with
relatively strong CPL performance (g lum ¼ Æ 2.1 Â 10
À2
) although the component
compound is achiral, while the other nanostructure could not.
Fig. 11.11 Chemical structures of 11, Rhodamine B and (a) CPL spectra recorded with counterclockwise (CCW, blue line) stirring, clockwise (CW, red line) stirring, and no stirring (black line).
The inset shows the four faces of the cuvette detected for the CPL measurements. (b) Statistical
distributions of g lum values in five different samples under CCW (blue) and CW (red) stirring
preparation in four faces of the sample cuvette. Reproduced with permission [33]. Copyright 2011,
Wiley-VCH
11 Circularly Polarized Luminescence from Gelator Molecules: From Isolated. . .
263
À2
, as
shown in Fig. 11.12a. Interestingly, in such a system mechanical stirring could
enhance the g lum values during the supramolecular gelation process (Fig. 11.12b).
In addition, the obtained gel dispersion was quite stable and the CPL remained
even after stopping the stirring. However, the direction of the CPL signals could not
be controlled by the stirring direction. The direction of CPL signals can be readily
regulated by adding some simple chiral dopants (Fig. 11.12c). More interestingly,
the g lum value was also amplified by chiral dopants (Æ 2.3 Â 10
À2 ).
In some cases, the CPL from the nanoassemblies based on achiral molecules showed
a morphology dependence. As illustrated in Fig. 11.13, twisted ribbons, nanobelts
and trumpet-like nanostructures can be formed from an achiral C 3 -symmetric molecule
via the assembly in a mixed DMF/water solvent [35]. At a unity mixing ratio, nanobelts
were observed. Upon increasing the amount of dimethylformamide (DMF), nanotwists
and nanotrumpets were formed by such nanobelts through twisting and rolling,
respectively. Intriguingly, the nanotwists showed supramolecular chirality with
relatively strong CPL performance (g lum ¼ Æ 2.1 Â 10
À2
) although the component
compound is achiral, while the other nanostructure could not.
Fig. 11.11 Chemical structures of 11, Rhodamine B and (a) CPL spectra recorded with counterclockwise (CCW, blue line) stirring, clockwise (CW, red line) stirring, and no stirring (black line).
The inset shows the four faces of the cuvette detected for the CPL measurements. (b) Statistical
distributions of g lum values in five different samples under CCW (blue) and CW (red) stirring
preparation in four faces of the sample cuvette. Reproduced with permission [33]. Copyright 2011,
Wiley-VCH
11 Circularly Polarized Luminescence from Gelator Molecules: From Isolated. . .
263