Chiral hybrid nanostructures

Fischer et al. have reported a new approach for production of hybrid nanocolloids with programmed three-dimensional shape and material composition (Fig. 23). ° The fabrication process involves a combination of low-temperature shadow deposition with nanoscale patterning and enables the production of nanocolloids with anisotropic three-dimensional shapes, feature sizes down to 20 nm and a wide choice of materials. As one example of the structures the researchers have fabricated hundreds of billions of plasmonic Au or Ag Cu nanohelices, which have demonstrated circular dichroism and tuneable chiroptical properties. 

In overall this work presents a convenient method to the fabrication of various complex 3D nanostructures with tailored electric, magnetic, optical and mechanical properties. 

In another work, silica nano helices have been prepared from the organic self-assemblies of -tartrate amphiphiles by sol-gel transcription. Then this chiral nanostructures were functionalized with (3-aminopropyl)-trietho)y-silane (APTES) or (3-mercaptopropyl)triethoxysilane (MPTES) and decorated with gold nanoparticles of various diameters (1-15 nm) resulting in nanohelix hybrid structures (Fig. 25). ° It was found that the surface plasmon resonance intensity of these nanohybrid systems increased with gold particle size. Gold nanoparticles of 10-14 nm diameter have clearly showed a surface enhanced effect on Raman spectroscopy. This sj tem is a unique example of the 3D hybrid network that could be used as ultrasensitive chemical and biological sensors for detection of molecules of interest in liquids by accumulation under flow. 

---

X. Wu et al. reported new chiral hybrid mesoporous silica based nanostructures which were formed by an assembly of uniform hollow... 

Figure 9.8) [70]. This work is part of a broader activity in the field of binaphthyl-based chiral macrocycles for chiroptical sensing and chiral nanostructuring [71-87]. The macrocycle 23 incorporates a Binol unit. In order to counterbalance the inherent distortion brought about by the binaphthyl units into the macro-cyclic framework, sp carbon atoms, imparting a higher conformational freedom with respect to sp- or sp -hybridized carbon atoms, have been introduced. 

---