Jong-Sung Yu tells Journal of Materials Chemistry about his hot paper.

1. Could you explain the significance of your article to the non-specialist and what has motivated you to conduct this work?
Silica materials with uniform ordered porosity and well-defined geometry have become attractive to many scientists due to their great application potential.  Our new materials are uniform silica spheres, each with a solid silica core surrounded by a mesoporous (pore diameter between 2nm to 50nm) silica outer shell.  The liquid colloidal method using surfactants has been known for some time as a fascinating method for the synthesis of mesoporous silica spheres.  However, the resulting mesoporous particles are polydisperse or not spherical, and/or the outer mesopore channels possess random pore orientations or are parallel to the curved silica surface.  So far, there has been no success in the synthesis of monodisperse mesoporous silica spheres with mesopore channels normal to the surface, which is beneficial for many applications. Such situations disturb uniform matrix formation for delicately controlled experiments such as drug delivery and photonics.  In addition, whereas our materials with cylindrical mesopores normal to the chemically functionalizable surface are optimal for unhindered access to the pore interiors for applications such as catalysis and selective adsorption, the porous channels parallel to the surface are so much more beneficial.  This is the first work that deals with the two important issues of particle monodispersity and mesopore orientation, both of which should be addressed for practical applications of the mesoporous materials.

2. Where do you see this work developing in the future?
Tailor-made mesoporous silica spheres show great potential in many emerging applications such as biomedical diagnosis or drug/gene delivery systems, where they are used as an effective vehicle for transferring those active ingredients. Our current samples may provide additional advantages due to the potential modification of the inner core silica materials with other materials such as novel metals or metal oxides, in addition to the outer mesoporous shell, which will provide "a new bottle for old wine" to the researchers having trouble with the conventional supports.  Furthermore, the current method can also applied to the generation of flat thin film silica materials with mesopore channels normal to the surface, which may be useful for many fundamental and industrial researches as a new substrate.  

3. Are there any particular challenges facing future research in this area?
The key to broadening future research and applications in this area will be working out how to increase the mesopore ordering without loss of the particles' uniformity and monodispersity, and how to control the thickness of the outer shell as well as the particle size.  Enlarging the pore size of the mesoporous shell without distorting the particle morphology will be another important issue in any delivery system designed to accommodate bulky active ingredients.  Synthesis of thin films with perpendicular ordered mesopore channels will be a further challenge, which may well open up more possibilities.

Jong-Yun Kim (left) received his PhD from Korea Advanced Institute of Science and Technology in 1999. His research interests range from surfactant self-assembly systems to analytical chemistry. As a chemical engineer, he is developing state-of-the-art "process analytical technology" for powder process monitoring by utilizing the mesoporous silica spheres as reference materials.

Jong-Sung Yu (centre) received a PhD in Chemistry from the University of Houston at 1990. Professor Yu has been a professor in the Chemistry Department at Hannam University since 1993. Currently, he serves as an editor of Journal of Experimental Nanoscience and Carbon Science. His research interests are broadly based on materials chemistry regarding synthesis, functionalization and characterization of novel nanostructured materials, and their applications to fuel cells, sensors, solar cells, photonics, bio-chips and nanoelectronics.

Suk Bon Yoon (right) received his PhD in Chemistry from Hannam University under the supervision of Professor Jong-Sung Yu in 2006. He has published 33 journal papers and 9 patents on the syntheses and applications of nano-engineered silica and carbon materials.  He is now at Korea Atomic Energy Research Institute as a postdoctoral fellow to work with Dr Jong-Yun Kim. His current research concentrates on the synthesis of large mesoporous silica microspheres as a reference material for the determination of an isotopic ratio during a single particle analysis.