title: Controlled Clustering in Binary Charged Colloids by Adsorption of Ionic Surfactants.
abstract: We report on the controlled clustering of oppositely charged colloidal particles by the adsorption of ionic surfactants, which tunes charge numbers Z of particles. In particular, we studied the heteroclustering of submicron-sized polystyrene (PS) and silica particles, both of which are negatively charged, in the presence of cetylpyridinium chloride (CPC), a cationic surfactant. The surfactant concentration Csurf was selected below the critical micelle concentration. As CPC molecules were adsorbed, Z values of the PS and silica particles decreased, inverting to positive when Csurf exceeded the isoelectric point Ciep. Hydrophobic PS particles exhibited much lower Ciep than hydrophilic silica particles. At Csurf valuess between their Ciep values, the particles were oppositely charged, and clustering was enabled. To explain the clustering behavior, we investigated adsorption isotherms of the CPC and screened-Coulomb-type pair potential. Expected applications of the present findings are the control of colloidal associations and construction of various particle types into heterogeneous colloidal clusters.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Nagoya City University , 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nakamura
authors.affiliation: Graduate School of Pharmaceutical Sciences, Nagoya City University , 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603, Japan.
authors.forename: Manami
authors.initials: M
authors.lastname: Okachi
authors.affiliation: Graduate School of Pharmaceutical Sciences, Nagoya City University , 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Toyotama
authors.affiliation: Graduate School of Pharmaceutical Sciences, Nagoya City University , 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Okuzono
authors.affiliation: Graduate School of Pharmaceutical Sciences, Nagoya City University , 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603, Japan.
authors.forename: Junpei
authors.initials: J
authors.lastname: Yamanaka
mesh_terms: D000327:Adsorption; D002594:Cetylpyridinium / Q000737:chemistry*; D003102:Colloids; D008823:Micelles; D011108:Polymers / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D003102:Colloids; D008823:Micelles; D011108:Polymers; D011137:Polystyrenes; D011725:Pyridines; D013451:Sulfonic Acids; D013501:Surface-Active Agents; D012822:Silicon Dioxide; D002594:Cetylpyridinium; C030953:2-vinylpyridine; C077114:styrenesulfonic acid polymer