Convenient chirality transfer from organics to titania: construction and optical properties

Abstract

Polyethyleneimine (PEI) complexed with chiral D- (or L-) tartaric acid (tart) in water can self-organize into chiral and crystalline PEI/tart assemblies. It has been previously confirmed that the complexes of PEI/tart could work as catalytic/chiral templates to induce the deposition of SiO₂ nanofibres with optical activity but without outwards shape chirality such as helices. In this work, we found that the templating functions of PEI/tart were still effective to prompt the deposition of TiO₂ to form chiral PEI/tart@TiO₂ hybrid nanofibres under aqueous and room temperature conditions within two hours. Furthermore, the co-deposition of TiO₂ and SiO₂ was also fulfilled to yield chiral PEI/tart@TiO₂/SiO₂ nanofibres. These TiO₂-containing hybrid nanofibres showed non-helical shapes on the length scale; however, chiroptical signals with mirror relation around the UV-Vis absorption band of TiO₂ remarkably appeared on their circular dichroism (CD) spectra. By means of the protocols of XRD, TEM, SEM, UV-Vis, CD and XPS, structural features and thermoproperties of the chiral TiO₂ and SiO₂/TiO₂ were investigated.