Arresting, Fixing, and Separating Dimers Composed of Uniform Silica Colloidal Spheres


  • This work was supported in part by a Science and Engineering Fellowship from the David and Lucile Packard Foundation and an AFOSR-DURINT subcontract from SUNY Buffalo. Y. X. is an Alfred P. Sloan Research Fellow and a Camille Dreyfus Teacher Scholar. This work used the Nanotech User Facility (NTUF) at the University of Washington, a member of the National Nanotechnology Infrastructure Network (NNIN), which is funded by the NSF. M. I. thanks the Fulbright Foundation and the Spanish Ministry of Education and Science for a postdoctoral fellowship. Supporting Information is available online from Wiley InterScience or from the author.


When fresh tetraethylorthosilicate is introduced into a colloidal suspension of silica spheres, it hydrolyzes and condenses in situ to arrest and fix the dimers resulting from constant collisions between the spheres. By optimizing the experimental parameters (including the length of aging time) and the diameter of the silica spheres, as well as the concentrations of counterions, water, and ammonia, it is possible to routinely produce monodisperse dimers with a yield as high as 50 %. When combined with centrifugation using a density gradient medium, the yield of such dimers could be further increased to 80 %. It is believed that this method will provide a simple and versatile approach to the high-volume production of dimers from spherical colloids composed of different materials. These dimers may find widespread use in a range of applications such as fabrication of photonic crystals and fundamental studies related to colloidal science.