The researchers first created separate nanoparticles of two materials, lead selenide and magnetic iron oxide, with precise dimensions.

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This would lessen the need to burn coal and oil, and lead to reduced emissions of carbon dioxide and nitrous oxide.

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That would change the way the magnetic field of the iron oxide interacts with the semiconducting behaviour of the lead selenide.

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To get the material to assemble properly, all of the molecules had to be a specific size--11 nanometers for the iron oxide particles, each of which is 60, 000 atoms across, and five nanometers across for the lead selenium quantum dots, each of which contains 3, 000 atoms.

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