Interparticle Interactions and Direct Imaging of Colloidal Phases Assembled from Microsphere-Nanoparticle Mixtures

@article{martinez05, abstract = {Abstract: We investigate the interparticle interactions, phase behavior, and structure of microsphere-nanoparticle mixtures that possess high size and charge asymmetry.1 We employ a novel Monte Carlo simulation scheme2 to calculate the effective microsphere interactions in suspension, yielding new insight into the origin of the experimentally observed behavior.3 The initial settling velocity, final sediment density, and three-dimensional structure of colloidal phases assembled from these binary mixtures via gravitational settling of silica microspheres in water and index-matched solutions exhibit a strong compositional dependence. Confocal laser scanning microscopy is used to directly image and quantify their structural evolution during assembly. Below a lower critical nanoparticle volume fraction (nano < L,C), the intrinsic van der Waals attraction between microspheres leads to the formation of colloidal gels. These gels exhibit enhanced consolidation as nano approaches L,C. When nano exceeds L,C, an effective repulsion arises between microspheres due to the formation of a dynamic nanoparticle halo around the colloids. From this stable fluid phase, the microspheres settle into a crystalline array. Finally, above an upper critical nanoparticle volume fraction (nano > U,C), colloidal gels form whose structure becomes more open with increasing nanoparticle concentration due to the emergence of an effective microsphere attraction,3 whose magnitude exhibits a superlinear dependence on nano.}, address = {Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1304 West Green Street, Urbana, Illinois 61801, and Physics Department, Emory University, Atlanta, Georgia 30322}, author = {Martinez, C. J. and Liu, J. and Rhodes, S. K. and Luijten, E. and Weeks, E. R. and Lewis, J. A. }, citeulike-article-id = {1678101}, doi = {http://dx.doi.org/10.1021/la050382s}, journal = {Langmuir}, keywords = {colloidal-gel, colloids, confocal, depletion, structure}, month = {October}, number = {22}, pages = {9978--9989}, posted-at = {2007-09-20 05:13:21}, priority = {0}, title = {Interparticle Interactions and Direct Imaging of Colloidal Phases Assembled from Microsphere-Nanoparticle Mixtures}, url = {http://dx.doi.org/10.1021/la050382s}, volume = {21}, year = {2005} }

TY - JOUR ID - martinez05 L3 - citeulike-article-id:1678101 TI - Interparticle Interactions and Direct Imaging of Colloidal Phases Assembled from Microsphere-Nanoparticle Mixtures JF - Langmuir VL - 21 IS - 22 SP - 9978 EP - 9989 AD - Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1304 West Green Street, Urbana, Illinois 61801, and Physics Department, Emory University, Atlanta, Georgia 30322 N2 - Abstract: We investigate the interparticle interactions, phase behavior, and structure of microsphere-nanoparticle mixtures that possess high size and charge asymmetry.1 We employ a novel Monte Carlo simulation scheme2 to calculate the effective microsphere interactions in suspension, yielding new insight into the origin of the experimentally observed behavior.3 The initial settling velocity, final sediment density, and three-dimensional structure of colloidal phases assembled from these binary mixtures via gravitational settling of silica microspheres in water and index-matched solutions exhibit a strong compositional dependence. Confocal laser scanning microscopy is used to directly image and quantify their structural evolution during assembly. Below a lower critical nanoparticle volume fraction (nano < L,C), the intrinsic van der Waals attraction between microspheres leads to the formation of colloidal gels. These gels exhibit enhanced consolidation as nano approaches L,C. When nano exceeds L,C, an effective repulsion arises between microspheres due to the formation of a dynamic nanoparticle halo around the colloids. From this stable fluid phase, the microspheres settle into a crystalline array. Finally, above an upper critical nanoparticle volume fraction (nano > U,C), colloidal gels form whose structure becomes more open with increasing nanoparticle concentration due to the emergence of an effective microsphere attraction,3 whose magnitude exhibits a superlinear dependence on nano. KW - colloidal-gel KW - colloids KW - confocal KW - depletion KW - structure AU - Martinez, CJ AU - Liu, J AU - Rhodes, SK AU - Luijten, E AU - Weeks, ER AU - Lewis, JA PY - 2005/10/25/ UR - http://dx.doi.org/10.1021/la050382s ER -