Hollow particles as controlled small space to functionalize materials

Molecules indicate a particular property by obeying a special characteristic in small space in some cases. It was discovered for a liquid phase such as decreasing the melting point in a nano-sized pore. A special phenomenon may also occur in the gas phase in a small space. To demonstrate this prediction, I have begun trying to fabricate a small space. A nano-sized hollow structure is very attractive for obtaining a small space. An inorganic template using inorganic particles is a facile technique to obtain hollow particles with various shapes, sizes, from nano to micron, and also different shell microstructures. This paper describes the sol–gel synthesis that is useful to form the shell structure of hollow particles and then how to control the particle structure using various templating routes. The hollow particles are used for the fabrication of air/solid composites with a controlled small space. These structure controls provide wide applications such as superior thermal insulation films, anti-corrosion films, and unexpected “easy-to-grip” volleyball coatings, etc. In addition to our achievements using hollow silica nanoparticles, the development of applications such as the lithium ion battery, biomedical products, catalysts, etc., will be outlined.