MRI: Colloidal Characterization Capability through Combined DLS-ACS Analysis

该奖项来自主要研究仪器计划，资助在单个铁氧体样品上建立一个集成的颗粒特性分布测量系统。当悬浮粒子之间的强相互作用可以压倒波动耗散和热化时，胶体动力学特别复杂。这个问题在铁磁流体中非常明显，在铁磁流体中，长距离磁偶极子相互作用会导致逐渐聚集和失去理想的胶体特性。一类特殊的铁磁流体被称为铁磁流体，其中特别制造的铁磁纳米颗粒悬浮在液晶基质中，由于其强磁光响应而越来越受欢迎。铁离子学的长期稳定性取决于表面活性剂的加入，这些表面活性剂支持足够的电荷或空间效应来抵消粒子间的磁力。铁动力学的正确动态表示要求对数学动力学方程进行修改，以包含粒子间的力，并对粒子物理、磁性和电学性质的整个集合进行平均。具有ζ电位能力的动态光散射用于确定颗粒尺寸和表面电荷，然后将该信息反馈给具有扫频能力的交流磁化率测量，该扫描频率能力表征颗粒磁性作为其物理尺寸的函数。然后，这些组合分布用于开发和验证先进的动力学模型，并评估胶体对团聚和沉积的稳定性。随着纳米颗粒科学技术的发展，各种类型的液体悬浮纳米颗粒（胶体）被证明对科学、工程和环境应用具有特别重要的意义。了解区分分散悬浮液与沉淀或结块的关键纳米颗粒参数，将导致更高级的工程材料，如铁磁流体、纳米药物递送剂和生物燃料，以及改善对海洋和湖泊水文流动的环境理解。该奖项来自主要研究仪器项目，资助建立一对互补的表征仪器。第一个工具使用动态光散射（DLS）来确定颗粒大小和表面电荷分布。然后，这些信息被反馈到磁测量，交流磁化率（ACS），利用相同的胶体样品，并表征颗粒的磁化分布和磁开关行为。DLS还将用于研究水文沉积研究，如动态密度和浊度流。除了胶体研究外，化学、物理、大气和水文科学系的一些本科课程将在他们的教学实验室中纳入这些表征技术。

TechnicalThis award from the Major Research Instrumentation Program funds the establishment of an integrated particle property distribution measurements system on a single ferronematic sample. Colloid dynamics are particularly complex when strong interactions amongst the suspended particles can overwhelm the fluctuation-dissipation and thermalization. This problem is prominently manifest in ferrofluids where long range magnetic dipole interactions can lead to gradual agglomeration and loss of desirable colloidal characteristics. A particular class of ferrofluids known as ferronematics, where specially fabricated ferromagnetic nano-particles are suspended in liquid crystal host matrices, is gaining increasing popularity due to their strong magneto-optical response. Long term stability of ferronematics depend on the incorporation of surfactants that support sufficient electric charge or steric effects to counteract the inter-particle magnetic attraction. Proper dynamical representation of ferronematics requires that the mathematical dynamical equation be modified to incorporate the inter-particle forces and be averaged over the entire ensemble of particle physical, magnetic, and electric properties. Dynamic light scattering with zeta-potential capability is used to determine particle size and surface charge and then that information is fed forward to the ac susceptibility measurement with swept frequency capability that characterizes particle magnetics as a function of its physical dimension. The combined distributions are then used to develop and validate advanced dynamical models and to evaluate colloid stability against agglomeration and sedimentation.Non TechnicalAs the science and technology of nanoparticles evolve, various classes of liquid suspended nanoparticles (colloids) are proving to be of particular importance to science, engineering, and environmental applications. Understanding the critical nanoparticle parameters that differentiate dispersed suspension from sedimentation or agglomeration will lead to superior classes of engineered materials such as ferrofluids, nano-drug delivery agents, and biofuels, as well as improved environmental understanding of hydrologic flows in oceans and lakes. This award from the Major Research Instrumentation program funds the establishment of a complementary pair of characterization instruments. The first tool determines particle size and surface charge distributions using Dynamic Light Scattering (DLS). That information is then fed forward to a magnetic measurement, AC Susceptibility (ACS), that utilizes the same colloid sample and characterizes the particle magnetization distribution and magnetic switching behavior. DLS will also be used for studying hydrologic sedimentation research such as dynamics density and turbidity flows. In addition to colloidal research, several undergraduate classes in the departments of chemistry, physics, and atmospheric and hydrological sciences will incorporate these characterization techniques in their instructional laboratories.