Hard-templating Of Chiral Inorganic Nanomaterials With Optical Activity

Chirality is universal in nature and it is one of important properties of nature.A series of chiral organic functional materials have been synthesized by imitating chiral structure in nature.Additionally,mechanisms involved in chirality formation and unique properties of the chiral organic functional materials have been deeply studied.In recent years,chiral inorganic materials have attracted great attention because of their unique physical and chemical properties comparing with organic materials.Although many efforts have been made on synthesis of chiral inorganic materials,it is still a challenge to explore new types of optically active（OA）inorganic materials.Thus it is very important to synthesize chiral inorganic nanomaterials and study their optical activity.Here,chiral inorganic nanomaterials with OA have been synthesized,also structure of the nanomaterials and mechanism of their OA have been investigated.In Chapter 1,research background of chiral inorganic nanomaterials was summarily introduced.Different generations of OA,synthesis methods and promising applications of chiral inorganic nanomaterials were reviewed.Also research strategies and significance of this topic were proposed.In Chapter 2,double helically chiral polypyrrole（PPy）and chiral carbon nanotubes with electron transition-based OA（ETOA）were synthesized via soft-templating method.In this chapter,we used long chain amino acid derivatives superstructure as the soft template to synthesize PPy,which was induced to form around the soft template.Then carbon nanotubes were obtained after calcination of chiral PPy nanotubes.Circular dichroism spectra indicated that chiral PPy nanotubes and chiral carbon nanotubes exhibit strong optical activity.The optical activity of chiral PPy nanotubes and chiral carbon nanotubes were derived from long-range helical arrangement of pyrrole chromophore group and carbonaceous structure.Consequently,excitation could be delocalized throughout the entire aggregates,resulting in preferentially absorbing one circular polarization over the other,giving rise to preferential optically active signals.In Chapter 3,chiral CCN@ZnS nanocomposites with ETOA have been synthesized via hard-templating method.Carbon nanotubes have been obtained by the calcination of chiral PPy nanotubes.The carbon nanotubes were coated with sodium dodecyl sulfate and the zinc and sulfide ions have been loaded by immersing the material in the aqueous solution.Chiral CCN@ZnS nanocomposites exhibited optical response to circularly polarized light（CPL）at the wavelength of 200-335 nm.This was attributed to the semiconductor ZnS-based electronic transitions from the valence band to the conduction band.In Chapter 4,chiral mesoporous TiO₂ nanowires with ETOA have been synthesized via hard-templating method.Chiral PPy nanotubes and chiral carbon nanotubes were chosen as hard templates,and TiO₂ was coaxially formed on the helical carbonaceous nanotubes.After removing the template by calcination at high temperature in air,TiO₂ nanocrystals with the original axial channel were obtained along with the formation of mesopores through nanocrystal packing.The left-handed and right-handed TiO₂ nanofibre obtained by hard-templating method showed symmetry ETOA-based CD signal in range of 330-350nm.In the chiral aggregates of TiO₂ with long-range helical orientation,excitation could be delocalized throughout the entire aggregates,resulting in preferentially absorbing one circular polarization over the other,giving rise to preferential optically active signals.In Chapter 5,the contents of this thesis were summarized and carried on a forecast to the following research.