Understanding how chemical reactions happen on tiny crystals in liquid solutions is central to a variety of fields, including materials synthesis and heterogeneous catalysis, but obtaining such an understanding requires that scientists observe reactions as they occur.
By using coherent X-ray diffraction techniques, scientists can measure the exterior shape of and strain in nanocrystalline materials with a high degree of precision. However, carrying out such measurements requires precise control of the position and angles of the tiny crystal with respect to the incoming X-ray beam. Traditionally, this has meant adhering or gluing the crystal to a surface, which in turn strains the crystal, thus altering its structure and potentially affecting reactivity.
Image: Scientists have found a way to use “optical tweezers” by employing lasers, a mirror and a light modulator to anchor a crystal in solution. The “tweezers” have made it possible to conduct X-ray diffraction measurements of a crystal suspended in solution.
Credit: Robert Horn/Argonne National Laboratory.