CAREER: Understanding the Formation Mechanism of Binary SAMs to Create an Experimental Phase Diagram

职业：了解二元 SAM 的形成机制以创建实验相图

• 批准号: 2045012
• 负责人: Lynna Avila-Bront
• 金额: $ 41.74万
• 依托单位: College of the Holy Cross
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-05-01 至 2026-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2045012&HistoricalAwards=false
• 关键词: CAREER; Understanding; Formation; Mechanism; Binary

In this project, funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Dr. L. Gaby Avila-Bront of the College of the Holy Cross is using a microscope capable of visualizing individual molecules to understand the fundamental driving forces that determine how a mixture of different molecules bound to a surface forms a two-dimensional pattern. Although surfaces modified with molecular patterns find many applications including serving as chemical and physical sensors, it is currently not possible to precisely control the composition of a molecular pattern composed of dissimilar molecules on a surface. Furthermore, prior to mixing, there is no knowledge of what two-dimensional patterns may form, or what new properties of the surface will be observed. Even though the behavior of mixtures has been thoroughly investigated in three-dimensions, the picture is not complete because current treatments do not properly consider chemical processes that occur on surfaces. This presents a challenge for understanding how molecules mix on surfaces, and predicting the pattern of a mixture of molecules on a surface. Successfully addressing these issues could provide scientists with unprecedented top-down control over surface modification with molecular patterning. All of the research in this lab is conducted and driven by undergraduate students. These students will conduct the experiments, analyze and interpret the data, and will be encouraged to present their findings at scientific conferences, while working closely with Dr. Avila-Bront to produce manuscripts for publication. In doing so, the students are developing and honing their problem-solving skills so that they can transfer these skills in the post-graduate fields of their choice.The overall goal of this work is to understand the mechanism of two-dimensional mixing processes and construct the experimental phase diagram of two-component (binary) self-assembled monolayers (SAMs). An experimental phase diagram of a binary SAM would enable the enrichment or separation of two-dimensional materials based on thermodynamic conditions, as well as the design of surfaces with deliberate preformed patterns. SAMs of organothiol compounds on noble metal surfaces are model two-dimensional systems that have been extensively characterized and utilized in numerous applications. However, as SAM functionalities have been extended, central questions about the mechanism of SAM phase behavior remain unanswered. An experimental phase diagram for a binary SAM has never been reported because it is very difficult to control the composition of a binary SAM. Therefore, this project begins by creating a library of binary monolayers composed of aliphatic and aromatic organothiols on the (111) surface of gold. The structure of the SAM is to be molecularly resolved using STM (Scanning Tunneling Microscopy) in ambient conditions, and contact angle measurements will be made to quantify the ordering properties of the SAM. Once this library is established, a model binary monolayer of known composition will be constructed. The composition of the monolayer will be interrogated using X-ray photoelectron spectroscopy and reductive desorption. An experimental phase diagram will then be constructed by correlating the phases present in this model binary monolayer to the chemical composition of the monolayer at different temperatures. The accuracy of the resulting phase diagram will be tested by using it to predict the monolayer structure of novel SAMs. The broader impacts of this work will include the training and mentoring of undergraduate students in chemical research. In addition, Dr. Avila-Bront is establishing a community outreach program and expanding remote outreach to elementary schools--including a program where undergraduate students work with elementary students on science-fair projects-- with virtual workshops aimed at encouraging critical assessment of science in the popular media.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.

在这个由化学部门化学结构动力学和机制（CSDM-A）项目资助的项目中，圣十字学院的L. Gaby Avila-Bront博士正在使用一种能够可视化单个分子的显微镜来了解决定不同分子的混合物如何与表面结合形成二维模式的基本驱动力。虽然用分子模式修饰的表面有许多应用，包括用作化学和物理传感器，但目前还不可能精确控制表面上由不同分子组成的分子模式的组成。此外，在混合之前，不知道会形成什么样的二维模式，也不知道会观察到表面的什么新特性。尽管混合物的行为已经在三维空间中进行了彻底的研究，但由于目前的处理方法没有适当地考虑表面上发生的化学过程，所以情况还不完整。这对理解分子如何在表面混合以及预测表面上分子混合物的模式提出了挑战。成功地解决这些问题可以为科学家提供前所未有的自上而下的控制表面修饰分子模式。本实验室的所有研究都是由本科生进行和推动的。这些学生将进行实验，分析和解释数据，并鼓励他们在科学会议上展示他们的发现，同时与阿维拉-勃朗特博士密切合作，撰写论文发表。在这样做的过程中，学生们正在发展和磨练他们解决问题的能力，以便他们可以将这些技能转移到他们选择的研究生领域。本工作的总体目标是了解二维混合过程的机制，并构建双组分（二元）自组装单层（SAMs）的实验相图。二元SAM的实验相图将使基于热力学条件的二维材料的富集或分离，以及设计具有故意预制图案的表面成为可能。有机硫醇类化合物在贵金属表面上的sam是一种模型二维系统，已经被广泛地表征并应用于许多应用中。然而，随着SAM功能的扩展，关于SAM阶段行为机制的核心问题仍然没有答案。由于很难控制二元地对空导弹的组成，因此从未报道过二元地对空导弹的实验相图。因此，本项目首先在金（111）表面创建一个由脂肪族和芳香有机硫醇组成的二元单层库。在环境条件下使用STM（扫描隧道显微镜）对SAM的结构进行分子解析，并进行接触角测量以量化SAM的有序特性。一旦建立了这个库，一个已知组成的模型二元单层将被构造。利用x射线光电子能谱和还原性脱附对单层的组成进行研究。然后，通过将模型二元单层中存在的相与不同温度下单层的化学成分相关联，构建实验相图。所得相图的准确性将通过使用它来预测新型SAMs的单层结构来检验。这项工作的更广泛的影响将包括对化学研究的本科生的培训和指导。此外，阿维拉-勃朗特博士正在建立一个社区外展项目，并扩大对小学的远程外展——包括一个让本科生与小学生一起参与科学展览项目的项目——以及旨在鼓励大众媒体对科学进行批判性评估的虚拟研讨会。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。