Optical 'tweezers' combine with X-rays to enable analysis of crystals in liquids

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. "With optical tweezers, you can capture a single particle in its native state in solution and watch its structural evolution," said Linda Young, Argonne distinguished fellow.