Visualizing Nanoparticle Packing at Liquid Interfaces

可视化液体界面处的纳米粒子堆积

• 批准号: 1807255
• 负责人: Thomas Russell
• 金额: $ 68.67万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1807255&HistoricalAwards=false
• 关键词: Visualizing; Nanoparticle; Packing; Liquid; Interfaces

NON-TECHNICAL ABSTRACTNanoparticles, objects not much larger than molecules, assemble in two- and three-dimensions into materials with unique and technologically important properties. Until recently, this assembly could not be directly seen because of the very small size of nanoparticles. For this proposal, a new imaging method has been developed that can resolve the structure and motions of individual nanoparticles assembled on a liquid interface. The method combines the high resolution of electron microscopy, about 100-1000 times greater than optical microscopy, with the nonvolatility of ionic liquids, essentially liquid salts, to probe the two-dimensional assembly of nanoparticles as a function of nanoparticle size, geometry, bulk chemistry, surface chemistry, and degree of liquid wetting. Unlike larger particles, nanoparticles can interact with each other over distances as large as the particles themselves, a feature that facilitates assembly into well-ordered structures. Also unlike larger particles, these interactions are weak, allowing the particles to "jiggle around" so as to find the best arrangement. In many experiments, different sorts of nanoparticles are mixed, increasing the diversity of the ordered structures, or in other cases, creating a frozen disordered "jammed" state. Determining conditions under which nanoparticle particles organize, understanding how these changes affect organization, and uncovering ways to make completely disordered systems are the key project objectives. This research is performed by undergraduate, graduate, and post-doctoral fellows, and the outcomes are often striking images or movies easily understandable by everyone. In the long term, the tools and techniques emerging from this research should apply easily to other technologically important materials such as gels, emulsions, liquid crystals, and suspensions, all of which display bulk properties determined by nanoscale features and events.TECHNICAL ABSTRACTDespite a need to impose vacuum, scanning electron microscopy can be performed on open liquid specimens when the components are wetted by, or dispersed in, a nonvolatile ionic liquid. At an imaging resolution of 3-5 nm, several frames per second can be acquired over an unlimited time. Preliminary experiments established the feasibility of scanning-electron-microscope, single-particle tracking even for dense nanoparticle packings and non-spherical particle shapes. The method functions much like optical video microscopy but at 10-100X greater magnification. Two-dimensional nanoparticle ordering on ionic liquid surfaces is now pursued comprehensively and quantitatively, examining effects of nanoparticle size, geometry, bulk chemistry, surface chemistry (i.e., polymer ligand type), and degree of liquid wetting. In addition, different types of nanoparticles are mixed. Unlike larger colloidal particles, nanoparticle interactions are typically weak, allowing equilibrium assembly under Brownian motion alone. The interaction potential will be evaluated for all listed parameters, with greatest attention on ligand type, which controls the interaction length scale, reaching or exceeding the particle size. Ligands also affect the contact angle, which dictates how deeply the interface-trapped particle protrudes into the underlying liquid, and, in turn, this depth influences particle dynamics. A new transmission-electron-microscopy approach to nanoparticle contact angle is being assessed, and by the new scanning-electron-microscopy tracking method, the associated interfacial nanoparticle dynamics are being quantified. Both ordered and disordered dense nanoparticle packings are being studied, with the latter facilitated by mixing particles of different size/shape. To control nanoparticle areal density, a unique device for control of interfacial area is placed inside the microscope, with areal adjustments made in situ as image sequences are collected. Assembly into dense structures is analyzed by calculating translational and orientational parameters. Lastly, an interesting and unexplained coupling between the electron beam of the microscope and solid metallic or metal-coated nanoparticles is being pursued to create precise nanoparticle patterns on liquid surfaces.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.

非技术性质的纳米颗粒，即不比分子大多少的物体，以二维和三维的形式组装成具有独特和重要技术特性的材料。直到最近，由于纳米颗粒的尺寸非常小，人们还无法直接看到这种组装。对于这一提议，已经开发了一种新的成像方法，该方法可以解析组装在液体界面上的单个纳米粒子的结构和运动。该方法结合了电子显微镜的高分辨率(约为光学显微镜的100-1000倍)和离子液体(主要是液体盐)的不挥发性，以探测纳米颗粒的二维组装，作为纳米颗粒尺寸、几何形状、体化学、表面化学和液体润湿度的函数。与更大的颗粒不同，纳米颗粒可以在与颗粒本身一样大的距离内相互作用，这一特征有助于组装成有序的结构。与较大的粒子不同的是，这些相互作用很弱，允许粒子“晃动”以找到最佳排列方式。在许多实验中，不同种类的纳米颗粒混合在一起，增加了有序结构的多样性，或者在其他情况下，创造了一种冻结的无序“堵塞”状态。确定纳米颗粒组织的条件，了解这些变化如何影响组织，以及发现使系统完全无序的方法是该项目的关键目标。这项研究是由本科生、研究生和博士后研究员进行的，结果往往是每个人都很容易理解的引人注目的图像或电影。从长远来看，这项研究中产生的工具和技术应该很容易应用于其他技术上重要的材料，如凝胶、乳液、液晶和悬浮液，所有这些材料都表现出由纳米级特征和事件决定的整体性质。技术摘要尽管需要施加真空，但当组分被非挥发性离子液体润湿或分散在其中时，可以对开放液体样品进行扫描电子显微镜检查。在3-5 nm的成像分辨率下，可以在无限时间内每秒采集几帧。初步实验确定了扫描电子显微镜、单颗粒示踪的可行性，即使是对致密的纳米颗粒填充和非球形颗粒。这种方法的功能很像光学视频显微镜，但放大倍数要大10-100倍。目前，离子液体表面的二维纳米粒子有序化研究是全面和定量的，考察了纳米粒子的尺寸、几何形状、体化学、表面化学(即聚合物配体类型)和液体润湿度的影响。此外，还混合了不同类型的纳米颗粒。与较大的胶体颗粒不同，纳米颗粒的相互作用通常很弱，仅在布朗运动下就可以进行平衡组装。将评估所有列出的参数的相互作用势，其中最关注的是配体类型，它控制相互作用长度的范围，达到或超过颗粒大小。配体还会影响接触角，接触角决定了界面捕获的粒子在底层液体中的突出深度，而该深度又会影响粒子的动力学。一种新的纳米粒子接触角的透射电子显微镜方法正在被评估，并且通过新的扫描电子显微镜跟踪方法，相关的纳米粒子界面动力学正在被量化。人们正在研究有序和无序的致密纳米颗粒填充，后者通过混合不同大小/形状的颗粒来促进。为了控制纳米颗粒的面密度，在显微镜内放置了一个独特的界面面积控制装置，并在采集图像序列时原位进行面积调整。通过计算平移和取向参数，分析了组装成致密结构的过程。最后，在显微镜的电子束和固体金属或金属涂层纳米颗粒之间进行了一种有趣且无法解释的耦合，以在液体表面创建精确的纳米颗粒图案。这一奖项反映了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。

项目成果

Impact of Electron Energy and Dose on Particle Dynamics Imaging in the Scanning Electron Microscope

电子能量和剂量对扫描电子显微镜中粒子动力学成像的影响

• DOI: 10.1017/s1431927619009085
• 发表时间: 2019
• 期刊: Microscopy and Microanalysis
• 影响因子: 2.8
• 作者: Gao, Yige;Srivastava, Satyam;Kim, Paul Y.;Hoagland, David A.;Russell, Thomas P.;Ribbe, Alexander E.
• 通讯作者: Ribbe, Alexander E.

Assessing Pair Interaction Potentials of Nanoparticles on Liquid Interfaces

• DOI: 10.1021/acsnano.8b08189
• 发表时间: 2019-03-01
• 期刊: ACS NANO
• 影响因子: 17.1
• 作者: Kim, Paul Y.;Gao, Yige;Russell, Thomas P.
• 通讯作者: Russell, Thomas P.

In Situ Electron Microscopy of Poly(ethylene glycol) Crystals Grown in Thin Ionic Liquids Films

在离子液体薄膜中生长的聚乙二醇晶体的原位电子显微镜

• DOI: 10.1002/pol.20190120
• 发表时间: 2020
• 期刊: Journal of Polymer Science
• 影响因子: 3.4
• 作者: Srivastava, Satyam;Ribbe, Alexander E.;Russell, Thomas P.;Hoagland, David A.
• 通讯作者: Hoagland, David A.

Bidisperse Nanospheres Jammed on a Liquid Surface

• DOI: 10.1021/acsnano.0c04682
• 发表时间: 2020-08-25
• 期刊: ACS NANO
• 影响因子: 17.1
• 作者: Gao, Yige;Kim, Paul Y.;Russell, Thomas P.
• 通讯作者: Russell, Thomas P.