Structural Evolution of Colloidal Crystals with Increasing Ionic Strength Michael A. Bevan,* Jennifer A. Lewis, ²,‡ Paul V. Braun, ² and Pierre Wiltzius ²,§ Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 Received March 21, 2004. In Final Form: June 5, 2004 We have directly observed the structural evolution of colloidal crystals as a function of increasing ionic strength using confocal scanning laser microscopy. Silica colloids were sedimented onto a glass substrate in deionized water to create large, single domain crystals. The solution ionic strength was then increased by one of three methods of controlled electrolyte addition: (1) direct injection of electrolyte solutions, (2) single step diffusion of electrolyte solutions through a dialysis membrane, and (3) multiple step diffusion of electrolyte solutions of increasing ionic strength through a dialysis membrane. During direct injection of electrolyte solutions, initially large, single domain colloidal crystals were shear melted and then evolved into polycrystalline structures at low ionic strengths and gels at higher ionic strengths. Diffusion of electrolyte solutions though dialysis membranes in a single step produced gradient-driven transport that also melted initial single domain crystals to yield polycrystalline and gel structures similar to the injection approach. Interestingly, the multistep diffusion of several electrolyte solutions through dialysis membranes facilitated retention of large, single domain crystals even as particles came into adhesive contact. This was achieved by reducing the contraction rate of the crystalline lattice to allow sufficient time for diffusion-limited configurational rearrangements to occur within the evolving structure. These mechanically robust, single domain colloidal crystals may find important applications as templates for photonic materials and sensors. Introduction Three-dimensional microperiodic structures fabricated from colloidal “building blocks” may find widespread technological use in applications such as advanced ce- ramics, 1 composites, 2 sensors, 3 and templates for photonic band gap materials. 4 Aqueous colloids are known to self- assemble into large, single crystal domains at low ionic strength conditions. 5 However, these crystals are me- chanically weak due to the extended electrostatic double layer surrounding each particle. 6 As a result, simple shear alone is sufficient to induce melting 7 and structural transitions. 8 Moreover, attempts to create dried, adhesive colloidal crystals from such systems are generally limited by the formation of polycrystalline domains and cracks during drying. 9 Several methods for assembling large, single domain crystals have recently been introduced, which rely on capillary-driven consolidation (e.g., using a fluidic cell 10 or dip coating 11,12 ) or colloidal epitaxy. 13 However, scant attention has been given to creating mechanically robust crystals through tuning colloidal interactions to produce adhesive particle contacts while simultaneously preserv- ing long-range order. Our approach relies on first as- sembling colloidal crystals with repulsive electrostatic interactions that extend well away from the particle surfaces, followed by tuning particle interactions through controlled electrolyte addition to allow van der Waals attraction to dominate. Because the face-centered cubic (fcc) crystal structure is the lowest free energy configu- ration for colloids with repulsive electrostatic, 5,14,15 hard sphere, 16-18 and attractive van der Waals potentials, 19-21 in principle it should be possible to design processes for assembling single domain, fcc colloidal crystals at nearly any ionic strength. This is true provided that challenges, such as formation of kinetically trapped glassy 22-24 or irreversible gel 25,26 structures, associated with simply increasing the attraction between colloids via uncontrolled electrolyte addition can be overcome. Several studies have probed structures, interactions, and dynamics relevant to colloidal crystal assembly using * To whom correspondence should be addressed. E-mail: [email protected]. Current address: Department of Chemical Engineering, Texas A&M University, College Station, TX 77843- 3122. ² Department of Material Science and Engineering. ‡ Department of Chemical and Biomolecular Engineering. § Department of Physics. (1) Lewis, J. A. J. Am. Ceram. Soc. 2000, 83, 2341. (2) Ash, B. J.; Schadler, L. S.; Siegel, R. W. Mater. Lett. 2002, 55, 83. (3) Holtz, J. H.; Asher, S. A. Nature 1997, 389, 829. (4) Yablonovitch, E. Phys. Rev. Lett. 1987, 58, 2059. (5) Sirota, E. B.; Ou-Yang, H. D.; Sinha, S. K.; Chaikin, P. M. Phys. Rev. Lett. 1989, 62, 1524. (6) Russel, W. B.; Saville, D. A.; Schowalter, W. R. Colloidal Dispersions; Cambridge University Press: New York, 1989. (7) Grier, D. G.; Murray, C. A. J. Chem. Phys. 1994, 100, 9088. (8) Ackerson, B. J.; Clark, N. A. Phys. Rev. A 1984, 30, 906. (9) Routh, A. F.; Russel, W. B. Langmuir 1999, 15, 7762. (10) Park, S. H.; Xia, Y. Langmuir 1999, 15, 266. (11) Jiang, P.; Bertone, J. F.; Hwang, K. S.; Colvin, V. L. Chem. Mater. 1999, 11, 2132. (12) Vlasov, Y. A.; Bo, X.-Z.; Sturm, J. C.; Norris, D. J. Nature 2001, 414, 289. (13) van Blaaderen, A.; Ruel, R.; Wiltzius, P. Nature 1997, 385, 321. (14) Kose, A.; Ozka, M.; Takano, K.; Kobayashi, Y.; Hachisu, S. J. Colloid. Interface Sci. 1973, 44, 330. (15) Monovoukas, Y.; Gast, A. P. Langmuir 1991, 7, 460. (16) Hachisu, S.; Kobayashi, Y. J. J. Colloid. Interface Sci. 1974, 46, 470. (17) Ackerson, B. J.; Schatzel, K. Phys. Rev. E 1995, 53, 6448. (18) Gasser, U.; Weeks, E. R.; Schofield, A.; Pusey, P. N.; Weitz, D. A. Science 2001, 292, 258. (19) Smithline, S. J.; Haymet, A. D. J. J. Chem. Phys. 1985, 83, 4103. (20) Marr, D. W.; Gast, A. P. J. Chem. Phys. 1993, 99, 2024. (21) Kose, A.; Hachisu, S. J. Colloid Interface Sci. 1976, 55, 487. (22) Tokuyama, M. Phys. Rev. E 2000, 62, R5915. (23) Rosenbaum, D.; Zamora, P. C.; Zukoski, C. F. Phys. Rev. Lett. 1996, 76, 150. (24) Dawson, K. A. Curr. Opin. Colloid Interface Sci. 2002, 7, 218. (25) Buscall, R.; Mills, P. D. A.; Goodwin, J. W.; Lawson, D. W. J. Chem. Soc., Faraday Trans. 1 1988, 84, 4249. (26) Lin, M. Y.; Lindsay, H. M.; Weitz, D. A.; Ball, R. C.; Klein, R.; Meakin, P. Nature 1989, 339, 360. 7045 Langmuir 2004, 20, 7045-7052 10.1021/la0492658 CCC: $27.50 © 2004 American Chemical Society Published on Web 07/22/2004
Structural Evolution of Colloidal Crystals with Increasing Ionic Strength
May 17, 2023
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