These micro-size dandelion-like structures are small, but they have a big effect when they cover a material’s surface. So-called flower carbon nanotubes (FCNTs) developed by Prabhat K. Agnihotri’s team at the Indian Institute of Technology Ropar can absorb more than 99.9% of the light that falls on them, producing vanishingly black materials (bottom). The researchers make the FCNTs at roughly 800 °C by first growing the “stems” from acetylene gas, which forms carbon nanotubes on contact with small islands of an iron catalyst on a silicon surface. As the tip of the stems grow, the catalyst becomes less active till growth stops. By flowing hydrogen over those stems, Agnihotri’s team reactivates the iron catalyst and breaks it into smaller pieces, which are treated with acetylene gas again to make the smaller “petal” structures.
Credit: Viney Ghai, Read the paper at ACS Appl. Nano Mater. 2019, DOI: 10.1021/acsanm.9b01950
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