We demonstrate that the fluorescence emission that originated from a cyanine dye forming H-aggregates with a narrow absorption band and a remarkably large Stokes shift can be induced by symmetry breaking. The H-aggregate formation was successfully induced using chirally assembled cationic gemini surfactants with enantiomeric tartrate counterions as templates in water.
Synthesis of chiral inorganic or hybrid nanomaterials through sol-gel transcription of chiral organic templates has attracted a great deal of interest for more than a decade. However, the chiral nature of these inorganic matrices has never been directly observed. For the first time, we report a direct evaluation of chirality on noncrystalline silica chiral nanoribbons by vibrational circular dichroism (VCD) measurements. Strong Cotton effect around 1150-1000 cm from Si-O-Si asymmetric stretching vibration was observed. Surprisingly, calcination of these hybrid nanoribbons doubled the intensity of Cotton effects. On the basis of transmission electron microscopy observations, IR, VCD, NMR, and Raman spectroscopies, we demonstrate that the silica chirality originates from twisted siloxane network composed of chiral arrangement of the Si-O-Si bonds. Our findings clearly prove the presence of chiral organization of amorphous silica network, making them very promising chiral platforms for chiral recognition, optical applications, or asymmetric catalysis.
Using direct sulfation of cellulose, we prepared sulfated cellulose (CS) with various degrees of substitution of sulfate groups (DS), which we used as dopants for PEDOT. PEDOT/CS were prepared via in situ chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) in an aqueous CS solution. Films of the obtained PEDOT/CS were formed using spin-coating. As a reference, a PEDOT/PSS film was also formed. The electrical conductivity of the PEDOT/CS film with a DS of 1.03 was 0.576 S m À1 . In contrast, the electrical conductivity of the PEDOT/PSS film was 0.0153 S cm À1 . Using Raman spectroscopy, we found that the 1400 and 1500 cm À1 bands correspond to the C a QC b vibrations in the five-member PEDOT ring. Compared with the band of the PEDOT/PSS film, the band of the PEDOT/CS film red-shifted from 1437 to 1433 cm À1 and narrowed. We attributed the increased electrical conductivity of the PEDOT/ CS film to a greater proportion of the quinoid structure than in PEDOT contained in PEDOT/PSS.
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