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Researchers in Canada have succeeded in nanopatterning by constructing nanostructured titania within the tiny pores on a silicon surface. very small 'islands' of titania surrounded by silicon can be made if gold nanoparticles was placed selectively on the islands and the particles would be trapped because they would not be able to migrate over the silicon to meld with gold particles on other titania islands. The researchers have found a versatile technique to make parallel functionalization of silicon on the surface and the chemistry could be done either inside or outside the pores on silicon previously etched with nanoscale patterns.
Long polymers called block copolymers that have two different strands of polymers forced with each other through covalent links were used. These polymers under certain conditions separate out to form nanoscale structures and spontaneously self-assemble into complex hexagonal arrays patterns. In the block polymers having two polymer strands with different properties, the silicon surface is contacted by two different blocks of which one block can transport hydrofluoric acid (HF) reagents to the surface of the silicon to etching it.
The orientation of starting silicon makes functionalized structures with regular shapes while HF concentration controls their size. The chemical properties of the structures inside the pores are different from the flat top silicon surface so that reactions can be made to occur either inside the pores, or on top, or in both areas at the same time.
Nanopatterning in this way could be important in areas as diverse as catalysis and tissue engineering and interfacing for example the neurons. Titania can be used in devices like bone implants.