Singapore's Institute of Bioengineering and Nanotechnology has engineered the world's first tri-continuous mesoporous silica - a complex structure useful for catalysis, separation and drug delivery
Singapore's Institute of Bioengineering and Nanotechnology (IBN) has developed the first tri-continuous mesoporous material using a unique surfactant template. This completely new porous structure had previously only been predicted mathematically.1
Recently published in Nature Chemistry,2 this novel material, which is named IBN-9 after the research institute, is the first hexagonal nanoscale construct with three unconnected interwoven channels. It is said to be by far the most complex mesoporous nanostructure to have been synthesised in real-life and represents a new class of mesoporous materials.
Mesoporous silica materials have huge surface areas, making them ideal for use as catalysts to facilitate chemical reactions. The materials consist of pores of 2-50 nanometres (nm) in size. Their uniform nanometre-sized pores allow them to separate molecules by size difference. Their pores may also be used to trap drug molecules for controlled drug release. The ability to tailor the pore structure of mesoporous material is, therefore, of fundamental importance for various chemical and biological applications.
"IBN-9 demonstrates that it is possible to create three interwoven but independent pore channel systems along with a unique nanofibre morphology. Such a mesostructure makes distinct diffusion rates in different directions possible. This property would be very attractive for gas separation and drug delivery systems," says IBN executive director, Professor Jackie Y. Ying, who led this research.
Prior to IBN's work, there had already been interest towards tailoring mesoporous materials with unique pore structures and pore sizes. The most complex of these were the bi-continuous structures, which contain two unconnected interwoven channels. These materials are synthesised via self-assembly of silica around surfactant templates.
IBN researchers successfully synthesised the first tri-continuous mesoporous structure by using a specially designed surfactant template, N,N-dimethyl-L-phenylalanine. This surfactant has an unusual "tunable" head-group as well as a long hydrocarbon tail that has variable levels of water-repellent (hydrophobic) qualities.
By systematically changing the synthesis conditions using this surfactant, IBN researchers are able to achieve structures with increasing mean curvatures from the bi-continuous cubic IBN-6 to the tri-continuous 3D hexagonal IBN-9, and finally to the 2D hexagonal IBN-10.
The structural complexity of IBN-9 and its sister materials opens the possibility of creating even more complex multi-continuous meso-structures in the future.