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Update(MM/DD/YYYY):04/23/2019

Control of Mesochannels in Graphene-Mesoporous Silica Nanocomposite

– Control of depth and diameter of perpendicularly-oriented mesochannels –


Researcher: Zheng-Ming Wang, Chief Senior Researcher, Water Environment Technology Research Group, Environmental Management Research Institute

Points

  • Synthesis technique for a nanocomposite in which a graphene sheet is sandwiched between mesoporous silica films
  • The mesochannels in the silica are oriented perpendicularly to the graphene surfaces, and channel depth and diameter can be controlled.
  • Potential for use in applications including molecular sieve sensing and drug delivery systems
Figure
Formation mechanism of graphene-mesoporous silica nanocomposite with mesochannels of silica perpendicularly aligned toward graphene layers


Background

The creation of nanocomposites of graphene and mesoporous silica is expected to produce materials that combine the characteristics of both. When these materials are employed in applications such as sensing materials, the channels must be oriented perpendicularly to the substrate. However, conventional synthesis techniques, in which surfactant molecules are used as molecules that form templates for the creation of channels (template molecules), mainly produce materials in which the silica channels are oriented parallel to the substrate. In order to realize perpendicularly oriented channels, it has been necessary to use high-cost template molecules or external (electric or magnetic) fields.

Overview

In collaboration with the University of Toronto (Canada), AIST has developed a technique that makes it possible to control the diameter and depth of mesochannels oriented perpendicularly to the graphene surfaces in a sandwich-type nanocomposite formed by covering both obverse and reverse surfaces of a graphene sheet (a sheet having the thickness of a single carbon atom) with mesoporous silica films of several tens of nanometers thick. By combining the properties of graphene, such as electrical conductivity, thermal conductivity, and light-induced heat generation, and the porosity of mesoporous silica, it is possible to give graphene-mesoporous silica sandwich-type nanocomposites new functions. These composites are formed by growing porous silica on both sides of a graphene sheet in a solution of graphene oxide (a precursor of graphene), a source of organic silicon, and a surfactant. The diameter and depth of the channels of the silica can now be controlled, which was previously impossible. These parameters are important factors affecting functions including adsorptive activity for molecules entering the channels of the mesoporous silica film, the diffusion distance of adsorbed molecules and reacting molecules, and threshold values for the size of molecules selected by the material. It is considered that the ability to control the diameter and depth of the channels will expand the range of application of the materials, and it is expected to find use in applications including molecular sieve sensing of contaminants and drug delivery systems.







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