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

在化学系大分子、超分子和纳米化学(MSN)计划的支持下，印第安纳大学的Bogdan Dragnea教授正在利用尖端的显微镜研究纳米颗粒如何影响冰融化。众所周知，当温度达到32华氏度或0摄氏度时，冰就会融化形成水。然而，情况并不总是如此。纳米颗粒比这句话末尾的周期小约一百万倍，可以改变这种转变温度。当嵌入到冰中时，在纳米颗粒表面附近通常会形成一层薄层，在正常温度下可以融化。Dragnea教授与他的学生合作，使用光热显微镜技术观察当纳米颗粒被激光快速加热时，这层薄冰层的融化情况。他们的发现可能对理解各种环境过程有影响，例如大气中冰晶的形成，以及提供控制冰面上摩擦和粘合的方法。该项目还为不同背景的研究生和本科生提供了研究机会。此外，通过与印第安纳大学研究和技术公司(IURTC)的合作，Dragnea教授正在向他的学生介绍创业概念，因为他们正在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散装冰分开的界面准液体层(QLL)的传输和热力学性质。单个纳米粒子具有明确的表面化学结构和几何结构，嵌入在多晶冰的薄膜中。然后，纳米颗粒被激光激发加热，从而提高周围固体的温度。通过测量纳米粒子在不同温度下的散射光来检测量子发光的形成。通过纳米颗粒对激光脉冲的重复吸收来调制界面液体厚度，从而便于测量。除了表征球形纳米粒子的凸面外，还研究了形状可控纳米粒子凹面附近量子发光的形成。通过比较光学和热模拟与实验观测，提取了输运和热力学参数。对单个颗粒进行的实验缓解了与降低精确度的杂质、缺陷和颗粒之间的差异相关的挑战。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.