MRI: Colloidal Characterization Capability through Combined DLS-ACS Analysis

技术这项奖励来自重大研究仪器计划，用于资助在单个铁基样品上建立一个集成的粒子特性分布测量系统。当悬浮粒子之间的强相互作用可以压倒涨落耗散和热化时，胶体动力学就特别复杂。这个问题在磁流体中表现得尤为明显，因为长距离的磁偶极相互作用会导致胶体逐渐团聚和丧失理想的胶体特性。一类特殊的磁流体被称为铁磁流体，其中特殊制造的铁磁纳米粒子悬浮在液晶基质中，由于其强大的磁光响应而越来越受欢迎。亚铁化合物的长期稳定性依赖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颗粒间的磁性吸引。铁运动学的正确的动力学表示要求修改数学动力学方程以包含粒间力，并在整个粒子的物理、磁学和电学性质系综上求平均。具有Zeta电位能力的动态光散射被用来确定颗粒大小和表面电荷，然后该信息被前馈给具有扫频能力的交流磁化率测量，该测量将颗粒磁性表征为其物理尺寸的函数。随着纳米粒子科学和技术的发展，各种类型的液体悬浮纳米粒子(胶体)在科学、工程和环境应用中被证明是特别重要的。了解区分分散悬浮与沉积或团聚的关键纳米颗粒参数将导致更好的工程材料类别，如磁流体、纳米药物递送剂和生物燃料，并改善对海洋和湖泊中水文流动的环境理解。这一奖项来自主要研究仪器项目，用于建立一对互补的表征仪器。第一种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，这些信息被前馈给磁性测量AC磁化率(ACS)，该测量使用相同的胶体样品，并表征粒子的磁化分布和磁开关行为。DLS还将用于研究水文沉积研究，如动力学、密度和浊流。除了胶体研究，化学系、物理系以及大气和水文科学系的几个本科生班级将把这些表征技术纳入他们的教学实验室。

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.