2021年"Park AFM奖学金"获奖者公布: 分别在Nature Catalysis和ChemSusChem发表研究成果

Park Systems中国分公司（以下称为Park原子力显微镜）在中国于2018年开设了Park AFM奖学金项目。Park AFM奖学金面向中国各大高校研究室的科研人员，提供3000元人民币的奖学金，旨在鼓励年轻科学家们通过分享讨论研究成果进一步推进学者们在纳米科学领域的成果进度。所有纳米科学领域使用Park原子力显微镜产品进行单独研究或共同研究者都可申请。奖学金获得者由Park Systems美国技术应用部门的专业人员评估决定。

2021年度的"Park AFM奖学金"项目吸引了来自中国各大顶尖高校及研究机构的多位科研人员们参与申请。经过激烈角逐及Park美国应用部门的专业人员评估，来自清华大学未来实验室的副研究员陈迪博士后和来自华南理工大学化学与化工学院的王静禹博士后被评为"2021年Park AFM奖学金"的获奖者。

2021年奖学金获得者—陈迪博士

2020年1月还在斯坦福大学读博士后的陈迪博士以第一作者的身份在Nature Catalysis上发表了以"Constructing a pathway for mixed ion and electron transfer reactions for O2 incorporation in Pr0.1Ce0.9O2−x"为标题的论文 （以O2插入Pr0.1Ce0.9O2−x为案例构建离子和电子混合反应的反应路径)，该论文指出在界面电荷转移反应中，反应路径的复杂性随转移的电荷数而增加，并且在反应同时涉及电子（电荷）和离子（物质）时变得更加复杂。这些被称作的混合离子和电子转移（MIET）反应在嵌入/插入电化学至关重要，例如氧还原/演化的电催化剂和锂离子电池电极。了解MIET反应途径，特别是确定反应决速步(RDS)，对于在分子、电子和点缺陷层面上的界面工程至关重要。在这项工作中，我们开发了一个通用的实验和分析框架，用于解析在Pr0.1Ce0.9O2−x中插入O2（气）的反应途径。通过在控制固体中的氧活度和氧气分压的同时测量电流密度-过电势曲线，以及通过原位近常压X射线光电子能谱对化学驱动力和静电驱动力进行定量分析，我们对100多种反应途径进行了筛选，最终确定4种为可能的反应途径，并指出这4种反应途径的限速步均为电中性氧分子的解离过程。陈迪博士在本研究中使用了Park Systems XE-100对氧化物薄膜样品的表面粗糙度和晶粒尺寸进行了表征。可在Nature期刊查看原文。

作为2021年Park AFM奖学金的第一位获奖者，NanoScientific Magazine对陈迪博士进行了相关研究的英文采访，采访报道会更新在2021年秋季刊杂志上，敬请关注！

Park AFM Scholarship Awards –

 Dr. Di Chen

Introduction:

Dr. Di Chen is an associate research fellow of the Future Laboratory, Tsinghua University. He got his B.S. from Tsinghua University and Ph.D from MIT, both in Materials Science and Engineering. He completed his postdoc training at Stanford University. His research group works on the electrochemical reactions at the interfaces.

1.   Please summarize the research you do and explain why it is significant?  

We focused on understanding the high temperature reactions at the solid-gas interface. We used Pr-doped C_eO₂ thin film electrode as an example. By conducting in operando APXPS/APXAS characterizations, we clearly confirmed that there is no surface potential at the solid-gas interface. Combining current-voltage measurements under different applied bias with theoretical model simulations (defect chemistry and microkinetic models), we established a versatile method to determine the rate-determining step of oxygen incorporation reaction. We believe this method could be further extended to many other systems such as proton exchange membrane fuel cells and lithium batteries.

2.   How might your research be used?   

This research built a method to understand the rate-determining step of the oxygen incorporation reaction at the cathode of solid oxide fuel cells (SOFCs), which was considered as a main limiting parameter for the application of SOFCs at larger scale. We think this research would be useful for people to further design and improve the cathode materials in SOFCs and help to develop more renewable energy systems with high efficiency.

3.   What features of Park AFM are the most beneficial and why?

To understand the reactions on the surface of the thin film electrode, it is quite important for us to characterize the surface structure, which would influence the physical and chemical properties of the materials. Atomic force microscopy is a powerful tool characterize the surface structure. The AFM from Park satisfies our research needs very well. Park AFM has a function to fast load and unload the tip, which saved our time and reduce the loss of tips.

2021年奖学金获得者—王静禹博士

2020年3月王静禹博士在ChemSusChem期刊上发表了"Atomic Force Microscopy and Molecular Dynamics Simulations for Study of Lignin Solution Self-Assembly Mechanisms in Organic–Aqueous Solvent Mixtures"（中文题目："原子力显微镜结合分子动力学模拟研究木质素在有机-水混合溶剂中自组装机理")的论文，该项工作称：

近年来，木质素基纳米材料作为一种具有优异行的木质素产品受到越来越多的关注。将木质素分子制备成具有均一纳米结构的木质素纳米材料，可以有效地提升木质素的分散性、抗氧化性、抗紫外老化性等性能。其中，溶液自组装法具有操作简单、适用范围广、过程可调控性强等特点，是制备木质素基纳米材料最重要的方法之一。在木质素的溶液自组装过程中，木质素分子在良溶剂中的解聚和劣溶剂中的聚集是两个关键步骤。对木质素在良溶剂和劣溶剂中分子间作用力变化进行定量研究，有助于从分子层面理解木质素的聚集行为，实现木质素自组装的精确调控，从而指导制备具有特定结构、尺寸和性能的木质素基纳米材料。因此，我们利用原子力显微镜（Park Systems, XE-100）对木质素在有机溶剂-水体系下，自组装过程中的分子间作用力进行了定量测试。并进一步结合分子动力学模拟揭示了木质素自组装过程中的内在驱动机制。

以丙酮-水体系为例，酶解木质素（EHL）在水和丙酮中发生明显聚集（图1 a和1 c），而在丙酮-水混合溶剂中（水体积分数30%），EHL发生解聚（图1 b）。证明水和丙酮均为EHL的劣溶剂，而丙酮-水混合溶剂为EHL的良溶剂。分子间作用力测试显示，EHL在水中的作用力为-1.21±0.18 mN/m，在丙酮中作用力为-0.75±0.35 mN/m（负值表示吸引力）。而在丙酮-水混合溶剂中，EHL分子间作用力仅为-0.15±0.08 mN/m，相比于在水中和丙酮中分别减少了88%和80%。实验结果证明，木质素的溶剂环境由良溶剂逐步转变为劣溶剂过程中，木质素分子的分子间作用力逐渐变大，导致木质素分子慢慢聚集，形成一定的纳米结构，直到溶液自组装完成。如图1（d）、1（e）和1（f）所示，分子动力学模拟结果与上述实验结果一致。水分子和丙酮分子对木质素模型物亲水官能团和疏水官能团的径向分布函数（RDF）计算结果表明，丙酮分子更密集地分布在木质素疏水官能团（碳链和苯环）周围，使得木质素分子的疏水部分溶剂化（图1 g），而水分子更密集地分布在木质素亲水官能团（酚羟基和醇羟基）周围，使得木质素分子的亲水部分溶剂化（图1h）。上述实验和模拟结果证明，木质素在有机溶剂-水混合溶剂中，亲水官能团与疏水官能团均能很好地溶剂化，分子间作用力小。随着水或有机溶剂的增加，溶剂体系从良溶剂转变为劣溶剂，木质素分子间相互作用力增大，导致亲水或疏水部分开始聚集并诱导自组装过程。

图1 EHL在（a）水、（b）丙酮-水（水体积分数30%）和（c）丙酮中的溶解情况和分子间作用力；木质素模型物在（d）水、（e）丙酮-水（水体积分数30%）和（f）丙酮中的分子动力学模拟结果；混合溶剂中，水分子和丙酮分子对木质素（g）疏水官能团和（h）亲水官能团的RDF

根据上述机理，可以很好地控制木质素的聚集行为和自组装过程，从而制备木质素基纳米材料。如图2（a）所示，EHL被溶解于丙酮-水混合溶剂中，并未观察到明显的光散射现象，证明EHL在其中没有明显聚集。随着水或丙酮的加入，混合溶剂从EHL的良溶剂逐渐变为EHL的劣溶剂，当丙酮-水混合溶剂中丙酮含量增加到99.8%或水含量增加到70%时，溶液中出现明显的光散射现象，证明EHL形成了聚集体。AFM形貌图（图2 b）和SEM图（图2 c）证明通过该方法成功制备了直径为100 nm左右的均一的木质素正、反相胶体球。

  图5 EHL在丙酮-水混合溶剂体系中的自组装：（a）EHL溶液的光散射现象（丁达尔效应）；（b）EHL纳米胶体球的原子力显微镜形貌图，比例尺为1 μm； （c）EHL纳米胶体球的扫描电镜图，比例尺为300 nm

Park AFM Scholarship Awards – Dr. Jingyu Wang

来自NanoScientific Magazine的采访内容如下：

1.  Please summarize the research you do and explain why it is significant?

Natural polymers possess multiple advantages including eco-friendly, low cost, biocompatible, and biodegradable properties. Such advantages make natural polymers-based nanomaterials exhibit great potential in energy, biomedicine, and electronics fields. In order to deliver these great properties from molecular scale to mesoscopic and macroscopic scale, basic understanding of natural polymers is indispensable. One of my major research focuses on exploring the intermolecular interaction and solution behavior of natural polymers. Another major research of mine focuses on how to precisely control the supramolecular structure of natural polymers. These studies would provide fundamental understanding for the interaction mechanism of natural polymers in solution and significant guidance for the fabrication of natural polymers-based nanomaterials.

2.  How might your research be used?

My researches provide the quantitatively interaction results, such as intermolecular force and solution behavior, which reveal the interaction mechanism of natural polymers. From the basic science perspective, these results provide basic thermodynamics and kinetics understanding of natural polymer. From the application perspective, these studies provide significant guidance for the fabrication of natural polymers-based nanomaterials. For example, I explore the interaction between lignin molecules in solution. By revealing the change rule of intermolecular force between lignin, I reveal the self-assembly mechanism of lignin in organic solvent-water mixture and fabricate the uniform lignin nanoparticle with tunable size and great surface chemical properties.

3.  What features of Park AFM are the most beneficial and why?

Park Systems is the top AFM manufacturer in worldwide. Their AFM possesses various modules, which could realize multiple functions. In terms of my researches, the force measurement module is most helpful. This module enables researchers to obtain quantitative force information of physical, chemical, and biological interactions. By different modification to AFM probe and substrate, I can obtain the force-distance (F-D) curve between natural polymers in different media. Based on the F-D curves, many essential results could be investigated, such as intermolecular force, viscoelasticity and energy consumption.

Park中国还特别定制纯银奖章，所有在论文里使用Park机台并在论文里面提到Park机台的老师或者学生都可以申请纯银奖章，并百分百获奖！

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