Eco-Friendly Nanoparticles For More Vivid Displays

Scientists in Japan have created light-emitting nanoparticles that are fabricated without the toxic metal cadmium.

AsianScientist (Sep. 13, 2018) – In a study published in NPG Asia Materials, scientists in Japan have developed environmentally-friendly photoluminescent particles that accurately represent the color spectrum.

Most existing displays do not always accurately represent the world’s colors as we perceive them. To make better displays, researchers have focused their efforts on developing light-emitting nanoparticles. However, the metal—cadmium—used in these light-emitting nanoparticles is highly toxic, which limits its applications in medical research and in consumer products. There is thus a need to create non-toxic versions of these nanoparticles that reproduce colors accurately and in a very energy-efficient way.

In this study, researchers at Osaka University have fabricated semiconductor nanoparticles using more eco-friendly materials, namely silver indium disulfide coated in a shell consisting of gallium and sulfur.

“We synthesized non-toxic nanoparticles in the normal way: mix all ingredients together and heat them up. By tweaking the synthesis conditions and modifying the nanoparticle cores and the shells, we were able to achieve fantastic efficiencies and very pure colors,” said study coauthor Professor Susumu Kuwabata of Osaka University, Japan.

Enclosing nanoparticles in semiconductor shells is not a new concept, but the shells that are conventionally used have rigidly arranged atoms inside them. In contrast, the authors of this study managed to produce a coating that is more amorphous.

“The silver indium disulfide particles emitted purer colors after the coating with gallium sulfide. We think the less rigid nature of the shell material played an important part in making the nanoparticles more adaptable, and therefore able to take on more energetically-favorable conformations,” said study first author Assistant Professor Taro Uematsu says.

These findings demonstrate that it is possible to create cadmium-free, non-toxic nanoparticles with very good color-emitting properties by encapsulating nanoparticle cores in amorphous shells.

The article can be found at: Uematsu et al. (2018) Narrow Band-edge Photoluminescence from AgInS2 Semiconductor Nanoparticles by the Formation of Amorphous III–VI Semiconductor Shells.


Source: Osaka University; Photo: Pexels.
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