Dynamic Optical Studies of Transport Phenomena Associated with Melting and Recrystallization at the Nanoparticle-Ice Interface

在化学学部大分子、超分子和纳米化学（MSN）项目的支持下，印第安纳大学的Bogdan Dragnea教授正在利用复杂的显微镜研究纳米颗粒如何影响冰的融化。众所周知，当温度达到32华氏度（0摄氏度）时，冰融化成水。然而，情况并非总是如此。纳米粒子比这句话末尾的句号小一百万倍，却能改变这种转变温度。当嵌入冰中时，纳米颗粒表面附近通常会形成一层薄层，在常温下会融化。Dragnea教授和他的学生一起使用光热显微镜技术来观察纳米粒子被激光快速加热时薄冰层的融化情况。他们的发现可能有助于理解各种环境过程，如大气中冰晶的形成，并提供控制冰表面摩擦和粘附的方法。该项目还为来自不同背景的研究生和本科生提供研究机会。此外，通过与印第安纳大学研究与技术公司（IURTC）的合作，Dragnea教授正在向他的学生介绍创业概念，因为他们将项目的仪器和科学知识转化为可用的技术。Dragnea教授正在开发光热显微镜方法，以获得将纳米颗粒的固体表面与大块冰分离的界面准液体层（QLL）的传输和热力学性质。单纳米粒子具有明确的表面化学和几何形状嵌入在多晶冰的薄膜中。然后用激光激发加热纳米颗粒，提高周围固体的温度。通过测量纳米粒子在不同温度下散射的光来检测量子量子线的形成。通过纳米粒子对激光脉冲的反复吸收来调节界面液体的厚度，从而方便了测量。除了表征球形纳米颗粒的凸表面外，还研究了形状控制纳米颗粒在凹表面附近的QLL的形成。通过光学和热模拟与实验观测的比较，提取了输运和热力学参数。在单个颗粒上进行的实验减轻了与杂质，缺陷和颗粒对颗粒变化相关的挑战，这些变化降低了准确性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program in the Division of Chemistry, Professor Bogdan Dragnea at Indiana University is utilizing sophisticated microscopies to study how nanoparticles affect ice melting. It is well-know that ice melts to form water when the temperature reaches 32 degrees Fahrenheit, or 0 degrees Celsius. However, this is not always the case. Nanoparticles, which are about a million times smaller than the period at the end of this sentence, can change this transition temperature. When embedded in ice, a thin layer often forms near the nanoparticle surface that can melt below normal temperatures. Working with his students, Professor Dragnea uses a photothermal microscopy technique to observe the melting of this thin ice layer when the nanoparticle is rapidly heated by a laser. Their discoveries could have implications for understanding a variety of environmental processes such as ice crystal formation in the atmosphere, as well as provide ways of controlling friction and adhesion on icy surfaces. The project is also providing research opportunities for graduate and undergraduate students from diverse backgrounds. In addition, through collaboration with the Indiana University Research and Technology Corporation (IURTC), Professor Dragnea is introducing his students to entrepreneurial concepts as they translate the project's instrumentation and scientific knowledge into useable technologies. Professor Dragnea is developing photothermal microscopy methods to obtain the transport and thermodynamic properties of the interfacial quasi-liquid layer (QLL) that separates the solid surface of a nanoparticle from bulk ice. Single nanoparticles with well-defined surface chemistries and geometries are embedded in a film of polycrystalline ice. The nanoparticle is then heated by laser excitation, raising the temperature of the surrounding solid. The formation of the QLL is detected by measuring the light scattered by the nanoparticle at various temperatures. The measurement is facilitated by modulation of the interfacial liquid thickness through repeated absorption of laser pulses by the nanoparticle. In addition to characterizing the convex surfaces of spherical nanoparticles, the formation of the QLL near concave surfaces of shape-controlled nanoparticles is also studied. By comparing optical and thermal simulations to experimental observations, transport and thermodynamic parameters are extracted. Experiments performed on individual particles alleviate challenges associated with impurities, defects, and particle-to-particle variations that reduce accuracy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.