Ionic colloidal crystals: Ordered, multicomponent structures via controlled heterocoagulation.
We propose a new type of ordered colloid, the "ionic colloidal crystal" (ICC), which is stabilized by attractive electrostatic interactions analogous to those in atomic ionic materials. The rapid self-organization of colloids via this method should result in a diversity of orderings that are analogous to ionic compounds. Most of these complex structures would be difficult to produce by other methods. We use a Madelung summation approach to evaluate the conditions where ICC's are thermodynamically stable. Using this model, we compare the relative electrostatic energies of various structures showing that the regions of ICC stability are determined by two dimensionless parameters representing charge balance and the spatial extent of the electrostatic interactions. Parallels and distinctions between ICC's and classical ionic crystals are discussed. Monte Carlo simulations are utilized to examine the glass transition and melting temperatures, between which crystallization can occur, of a model system having the rocksalt structure. These tools allow us to make a first-order prediction of the experimentally accessible regions of surface charge, particle size, ionic strength, and temperature where ICC formation is probable.
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Garry R
GR
Maskaly
R Edwin
RE
García
W Craig
WC
Carter
Yet-Ming
YM
Chiang
D001703:Biophysics / Q000379:methods; D003102:Colloids / Q000737:chemistry*; D004247:DNA / Q000737:chemistry; D007477:Ions; D007700:Kinetics; D008968:Molecular Conformation; D009010:Monte Carlo Method; D055672:Static Electricity
D003102:Colloids; D007477:Ions; D004247:DNA