TY - JOUR
T1 - Charge nonuniformity light scattering
AU - Jones, Joseph F.
AU - Holtzer, Gretchen L.
AU - Snyder, Charles
AU - Yake, Allison M.
AU - Velegol, Darrell
N1 - Funding Information:
The authors thank the National Science Foundation for funding this research through CRAEMS Grant CH3-0089156. The authors also thank Joshua Cuppett for help with setting up the light scattering device.
PY - 2005/10/5
Y1 - 2005/10/5
N2 - Classical models for colloidal forces assume that the particles are uniformly charged. However, charge nonuniformity can decrease suspension stability and reduce the accuracy of colloidal assemblies. Our lab group has previously seen that polystyrene latex particles are often nonuniformly charged, through the experimental technique of "rotational electrophoresis" [J.D. Feick, N. Chukwumah, A.E. Noel, D. Velegol, Langmuir 20 (2004) 3090]. Even though rotational electrophoresis is unique in finding zeta potential nonuniformity on individual particles, the technique is currently time-consuming and for practical reasons is limited to particles larger than 1 μm in size. We now introduce a modification of the rotational electrophoresis technique: "charge nonuniformity light scattering" (CNLS). CNLS takes advantage of two effects: (1) nonuniformly charged particles will rotate in an applied electric field and (2) light scattering from anisotropic particles changes when the particles align, an effect already used in the electric light scattering technique. By "visualizing" rotational electrophoresis with light scattering and interpreting the results with electrokinetic modeling, CNLS enables a measurement of zeta potential distribution for a colloidal suspension of particles with anisotropic geometry. In order to test the method, we synthesized model colloidal doublets composed of spheres with zeta potentials ζ1 and ζ2. Using translational electrophoretic mobility experiments, we found the difference ζ2 - ζ1 for our doublets. We then conducted experiments with CNLS, which gave the same value of ζ2 - ζ1, verifying the accuracy of the technique. Thus, CNLS allows for much more rapid measurements of charge nonuniformity and will soon be applied to more challenging systems.
AB - Classical models for colloidal forces assume that the particles are uniformly charged. However, charge nonuniformity can decrease suspension stability and reduce the accuracy of colloidal assemblies. Our lab group has previously seen that polystyrene latex particles are often nonuniformly charged, through the experimental technique of "rotational electrophoresis" [J.D. Feick, N. Chukwumah, A.E. Noel, D. Velegol, Langmuir 20 (2004) 3090]. Even though rotational electrophoresis is unique in finding zeta potential nonuniformity on individual particles, the technique is currently time-consuming and for practical reasons is limited to particles larger than 1 μm in size. We now introduce a modification of the rotational electrophoresis technique: "charge nonuniformity light scattering" (CNLS). CNLS takes advantage of two effects: (1) nonuniformly charged particles will rotate in an applied electric field and (2) light scattering from anisotropic particles changes when the particles align, an effect already used in the electric light scattering technique. By "visualizing" rotational electrophoresis with light scattering and interpreting the results with electrokinetic modeling, CNLS enables a measurement of zeta potential distribution for a colloidal suspension of particles with anisotropic geometry. In order to test the method, we synthesized model colloidal doublets composed of spheres with zeta potentials ζ1 and ζ2. Using translational electrophoretic mobility experiments, we found the difference ζ2 - ζ1 for our doublets. We then conducted experiments with CNLS, which gave the same value of ζ2 - ζ1, verifying the accuracy of the technique. Thus, CNLS allows for much more rapid measurements of charge nonuniformity and will soon be applied to more challenging systems.
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U2 - 10.1016/j.colsurfa.2005.06.045
DO - 10.1016/j.colsurfa.2005.06.045
M3 - Article
AN - SCOPUS:25444492575
SN - 0927-7757
VL - 267
SP - 79
EP - 85
JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects
JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects
IS - 1-3
ER -