Today I learned how shining different coloured lights on solutions of silver ions, or silver nanoparticles, can make triangular prisms of silver grow. Chad Mirkin from Northwestern University, showed us this neat trick. The prisms are incredible – all exactly the same size and shape.
To change the size of these triangular prisms Mirkin changes the wavelength of light that he shines on the solutions. And they don’t change that much – rather they make much bigger prisms by sticking the smaller triangles together. The edges of the smaller triangles are made reactive by the action of light. Mirkin says that plasmon excitation is driving this weird chemistry. Plasmons are effects seen at metal surfaces when the particles interact with photons.
It also turns out that changing the pH can help control which sized particle grows. I suppose this makes sense becuase it’s all about silver ions being formed from the silver nanoparticles in solution.
I’m not sure about the usefulness of this work, but those silver triangles are really pretty.