A TEM (transmission electron microscope) image of copper sulfide/cadmium sulfide heterostructure nanoparticles (source: Kyoto University)
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The diffusion/reflectance spectrums of sunlight spectrum (purple), copper sulfide nanoparticle (black) and copper sulfide/cadmium sulfide heterostructure nanoparticle (red) (source: Kyoto University)
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A Japanese research group announced Feb 4, 2019, that it has synthesized a high-efficiency photocatalyst responsive to infrared light.

Its external quantum efficiency is 3.8% with a wavelength of 1,100nm. With the photocatalyst, the group succeeded in generating hydrogen by using light with a wavelength of 1,500nm, which is the maximum wavelength of sunlight that reaches the surface of the earth. This means that the photocatalyst can carry out energy conversion of almost all of sunlight in the infrared region with a high efficiency.

The group consists of researchers from Kyoto University, Toyota Technological Institute, Kwansei Gakuin University, Ritsumeikan University and National Institute for Materials Science (NIMS).

Photoelectric conversion using LSPR (localized surface plasmon resonance) is expected to be a key technology for high-efficiency energy conversion of infrared light because LSPR has properties that enable to control light having a wide wavelength range from ultraviolet to infrared regions. This time, the group synthesized heterostructure nanoparticles connecting cadmium sulfide nanoparticles and copper sulfide (Cu7S4) nanoparticles, which triggers LSPR with light in the infrared region. And the group evaluated its activity as a hydrogen-generating photocatalyst.