Shining Rings: A New Material Emits White Light When Exposed To Electricity

Scientists at Nagoya University have developed a new way to make stimuli-responsive materials in a predictable manner. They used this method to design a new material, a mixture of carbon nanorings and iodine, which conducts electricity and emits white light when exposed to electricity. The team's new approach could help generate a range of reliable stimuli-responsive materials, which can be used in memory devices, artificial muscles and drug delivery systems, among other applications.

Stimuli-responsive materials alter their own properties in response to external stimuli, such as photo-irradiation, heat, pressure and electricity. This feature can be controlled for a wide range of uses, such as in optical discs, computer memories and displays, as well as artificial muscles and drug delivery systems.

Researchers have been working to develop new stimuli-responsive materials in a predictable fashion. However, it has been extremely difficult to design and control the complex molecular arrangements of the materials.

Now, a simple and reliable method to synthesize stimuli-responsive materials has been developed by a team led by Nagoya University's JST-ERATO Itami Molecular Nanocarbon Project and the Institute of Transformative Bio-Molecules (ITbM). The results of this study were recently reported in the journal Angewandte Chemie International Edition.

The 'responsive porous host' method takes a molecule with a porous framework and binds to it a 'guest' molecule that is likely to react to external stimuli (Figure 1a). In this case, the team found that [10]cycloparaphenylene ([10]CPP), a hydrocarbon molecule composed of 10 para-connected benzene rings, made an ideal host when combined with iodine (I). Iodine situated itself inside the porous carbon rings, and reacted to electric stimulation. Not only did it conduct electricity, it also emitted a white light, which is unusual (Figure 1b). Typically, many other components are required to obtain the white color. This shows the potential of the new material, [10]CPP-I, for next generation illumination systems.

"This 'responsive porous host' approach is expected to be applicable to different stimuli, such as photo-irradiation, heat application and pH change, and open the path for devising a generic strategy for the development of stimuli-responsive materials in a controllable and predictable fashion," said Dr. Hirotoshi Sakamoto, a group leader of the JST-ERATO project.