Nanostructures silica helical

Figure 3.13 (Top) TEM micrographs of (a-i) silver nanocoils prepared by backfilling, (j-k) helical mesoporous silica grown inside nanochannels of different sizes (indicated below each micrograph). (Bottom) Schematic of differing confined nanostructural evolution with decreasing diameter of the nanochannels [56],...

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. 

Another area which was initiated during last year is development of chiral metal oxide based nanomaterials such as chiral Ti02 nanofibres and chiral ZrOj nanotubes. It is anticipated that these chiral metal oxide nanostructures will find very important applications as asymmetric catalysts. In addition the progress in the fabrication of mesoporous silica based chiral nanostructures e.g. helical architectures) should open new opportunities in chiral separation of enantiomeric compounds. 

Helical silica nanostructures Asymmetric No Sol-gel polymerization using chiral cationic gelator to induce formation of helical bundles (many silica nanotubes). Acidic conditions needed for helidty. Straight nanotubes obtained under basic conditions. [23]... 

Helical silica nanostructures Asymmetric No Surfactants used as templates [25]... 

Yang, Y.G., Suzuki, M., Owa, S., Shirai, H. and Hanabusa, K. (2006) Control of helical silica nanostructures using a chiral surfactant. Journal of Materials Chemistry, 16(17), 1544-50. 

Kinetically controlled formation of helical mesoporous silica nanostructures correlated to a ribbon intermediate phase. RSCAdv., 1, 229-237. 

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