Junio Joseph, Cohen Joel A, Ou-Yang H Daniel
Department of Physics, Lehigh University , Bethlehem, Pennsylvania 18015, United States.
Department of Physics, University of Massachusetts , Amherst, Massachusetts 01003, United States.
J Phys Chem B. 2016 Sep 1;120(34):9187-94. doi: 10.1021/acs.jpcb.6b05608. Epub 2016 Aug 23.
The optical-bottle technique is used to measure osmotic bulk moduli of colloid suspensions. The bulk modulus is determined by optically trapping an ensemble of nanoparticles and invoking a steady-state force balance between confining optical-gradient forces and repulsive osmotic-pressure forces. Osmotic bulk moduli are reported for aqueous suspensions of charged polystyrene particles in NaCl solutions as a function of particle concentration and ionic strength, and are compared to those determined by turbidity measurements under the same conditions. Effective particle charges are calculated from the bulk moduli and are found to increase as a function of ionic strength, consistent with previously reported results.
光镊瓶技术用于测量胶体悬浮液的渗透压体积模量。体积模量是通过光学捕获一组纳米粒子，并在限制光梯度力和排斥渗透压之间建立稳态力平衡来确定的。报道了NaCl溶液中带电聚苯乙烯颗粒水悬浮液的渗透压体积模量随颗粒浓度和离子强度的变化关系，并与相同条件下通过浊度测量确定的结果进行了比较。根据体积模量计算有效粒子电荷，发现其随离子强度增加，与先前报道的结果一致。
