Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong.
Langmuir. 2012 Nov 20;28(46):16022-8. doi: 10.1021/la303547m. Epub 2012 Nov 9.
Bimodal colloidal mixtures of nanoparticles and microparticles may show different phase behaviors depending upon the interparticle interaction of both species. In the present work, we examined the stabilization of spherical microparticles using highly charged, spherical nanoparticles. Total internal reflection microscopy (TIRM) was used to measure the interaction forces between a charged microparticle and flat glass substrate in aqueous solutions at varying volume fractions of nanoparticles of the same sign. We found that, in the system containing of highly charged nanoparticles, microparticle, and glass substrate, non-adsorbing charged nanoparticles in solution did not lead to depletion attraction. Instead, the addition of nanoparticles was to consistently create a repulsive force between the microparticle and glass substrate even at a very low nanoparticle volume fraction. This result might attributed to the formation of thin shells (halos) with a high local nanoparticle volume fraction to the region near the glass surface, resulting in electrostatic repulsion between the decorated surfaces. This study demonstrates that nanoparticle halos can also arise in binary systems of mutually but highly repulsive microparticle/nanoparticle dispersions.
双模态胶体纳米粒子和微米粒子的混合物可能表现出不同的相行为，这取决于两种物质的颗粒间相互作用。在本工作中，我们使用带高电荷的球形纳米粒子来稳定球形微米粒子。全内反射显微镜（TIRM）用于测量带同种电荷的微米粒子与平面玻璃基底之间在不同纳米粒子体积分数的水溶液中的相互作用力。我们发现，在含有带高电荷的纳米粒子、微米粒子和玻璃基底的体系中，溶液中不吸附的带电纳米粒子不会导致耗尽吸引力。相反，即使在纳米粒子体积分数非常低的情况下，纳米粒子的加入也会在微米粒子和玻璃基底之间产生持续的排斥力。这一结果可能归因于在玻璃表面附近区域形成具有高局部纳米粒子体积分数的薄壳（晕圈），导致修饰表面之间的静电排斥。本研究表明，纳米粒子晕圈也可以在相互但高度排斥的微米粒子/纳米粒子分散体的二元体系中产生。
