Mumbai A nine-member team led by the Tata Institute of Fundamental Research (TIFR) has developed black gold nanoparticles by tinkering with gold nanoparticles that can capture carbon dioxide (CO2) and convert it into fuel, and purify seawater into potable water.The scientists achieved this feat by changing the size of gold nanoparticles and the distance between them, causing them to absorb the entire visible and near-infrared region of solar light and turning black. Using solar energy, the black gold powder acted as a catalyst to convert CO2 to methane at atmospheric pressure and temperature. The black gold, the scientists said, could possibly be used to reduce the CO2 concentration, formed by industrial and vehicular emissions, in our atmosphere that leads to global warming.“There will be a day when taxes will be levied on CO2 emissions; the more you generate the more you pay. With rising CO2 concentration levels, every government will have to find a way to capture and convert CO2,” said Vivek Polshettiwar, lead author and associate professor, department of chemical sciences, TIFR. “Black nano gold will be useful since all industries emit CO2.”In May, CO2 levels in the earth’s atmosphere crossed 415ppm (parts per million) for the first time in recorded history based on data from the Mauna Loa Observatory in Hawaii.Akin to real trees that use CO2, sunlight and water to produce food, researchers said the developed black gold acts as an artificial tree because it also uses CO2, sunlight and water to produce methane — a core component in compressed natural gas used to power vehicles. In addition, black gold can also be used to convert seawater into potable water using the heat that the powder generates after absorbing sunlight, according to the researchers.With the aim of commercialising the product, the team will now focus on improving the yield of methane by further redesigning the catalyst.“The field of injection of gold particle plasmon-induced hot electrons to carry out catalysis is very contemporary and is being pursued in many laboratories across the world. The present work by TIFR brings to the table a new and more efficient platform to pursue this goal,” said Ajay Sood, professor at the department of physics, Institute of Science at Bengaluru, who was not involved in the study and described the work as “significant”.The work ‘Plasmonic colloidosomes of black gold for solar energy harvesting and hotspots directed catalysis for CO2 to fuel conversion’ is published in Chemical Science journal of the Royal Society of Chemistry.