Preparation Of Single-handed Helical Silica-based Hybrid Materials With Circularly Polarized Luminescence Activity

Circularly polarized luminescence(CPL)-active materials have attracted widespread attention due to their potential applications in the fields of optical sensors,3D displays,lasers and optical information storage.In recent years,organic materials with CPL activity have developed rapidly.However,the complicated synthesis and poor thermal stability limit their applications.Organic-inorganic hybrid nanomaterials generally enjoy the advantages of simple synthesis and good thermal stability.Single-handed helical hybrid nanomaterials with CPL activity have been rarely reported.This paper provided a strategy for constructing CPL-active single-handed helical silica-based hybrid nanomaterials through a supramolecular templating approach.Moreover,the process of pH-controlled CPL inversion was investigated preliminary.The results are as follows:Firstly,chiral silica nanotubes were prapared using the supramolecular self-assemblies of a pair of chiral cationic amphiphilic molecules as templates CPL-active hybrid nanomaterials were obtained by using tetraphenylethene(TPE)-containing organosiloxane,TPE-Si,to modify the surface of chiral silica through a post-grafting method.The circular dichroism(CD)spectra showed that TPE units were stacked in a chiral manner within the walls of nanotubes.This indicated that the charity transfer was achieved through covalent bonds.Secondly,single-handed helical TPE-bridged polybissilsesquioxane(TPE-silica)nanotubes with CPL activities were constructed through a supramolecular templating approach using the self-assemblies of chiral cationic amphiphilic molecules as templates and fluorescent organosiloxane BTSTPE as the precursor.The results showed that the morphology of polybissilsesquioxane was controlled by tuning the concentrations of templates,volume ratio of solvents and catalyst.Hybrid silica oligomers were absorbed on the surfaces of the nanofibers by electrostatic interaction and polycondensed to form single-handed helical nanotubes through sol-gel transcription.The CD spectra indicated that the chirality was transferred successfully from chiral supramolecular templates to the TPE scaffolds.Finally,CPL-active single-handed helical TPE-bridged polybissilsesquioxanes were prepared through a supramolecular templating approach using the self-assemblies of chiral anion amphiphilic molecules as templates.Meanwhile,the effect of pH on supramolecular co-assembly was studied.The results showed that pH could affect the accumulation of molecules during the process of cooperative co-assembly,which leads to the inversion of supramolecular chirality and CPL.