Scientists in Spain say they have tuned the shape and size of silica nanofibres by using pH-responsive gels as templates. 

Mario Llusar at Universitat Jaume I and colleagues used an organogel as a template for making silica nanofibres. The researchers used pH-sensitive amino acid derivatives as gelators, which form pH-responsive gels. Using a one-pot method, where the gel template is formed in situ, the researchers tuned the shape and size of the templated silica nanofibres by adjusting the pH.

As well as the one-pot route, Llusar used a two-step, so-called post-diffusion method in which the gel template is pre-formed. 'The post-diffusion strategy results in thicker nanofibers and/or nanotubes, with thicker mesoporous channels, and is a more flexible alternative,' said Llusar. 

Markus Antonietti, a materials scientist at the Max Planck Institute of Colloids and Interfaces, Germany said, 'the structures are conveniently made on the larger scale; are made of "non-risky" silica; show high absolute pore volumes; and are interesting for functional release applications based on their nano-capillarity.' 

Llusar said he is fascinated by the possibilities that chemists now have to use different self-assembly or co-assembly methods to make inorganic and hybrid materials with tailored properties. 'Undoubtedly, the design of highly anisotropic one-dimensional nanostructures by combining sol-gel and self-assembly procedures will continue to be a focus of intense research in the future,' he said. 

The researchers plan to extend their work to more complex inorganic systems and have already begun by looking at the templating of iron-oxide-based nanofibres. 

Katherine Davies