Overcoming Adsorption Limitations for Surface Enhanced Spectroscopy Measurements

新的生物、化学和放射制剂每天都在威胁着环境和人类的安全。虽然在小分子检测方面取得了重大进展，但在提供灵活的检测方法以实现准确的化学鉴定和对某些分子的敏感和选择性检测方面仍然存在挑战。在化学系化学测量和成像项目的支持下，爱荷华大学的Haes教授专注于开发表面敏感技术，如表面增强拉曼散射（SERS）作为分子检测工具。SERS是一种基于光的技术，用于识别和量化吸附在金属表面的分子。大多数分子不粘附在金属表面，限制了SERS和类似方法的实用性。Haes教授和她的团队使用实验和建模方法来开发SERS技术，以便它可以用于提供高选择性和高灵敏度的精确化学鉴定。通过这项研究，Haes教授为研究生和本科生提供了解决实际问题的机会。Haes的研究小组与K-12学生一起开展拓展活动，重点关注“事物的大小”。这个项目帮助学生通过实践活动了解尺寸对纳米尺度和宏观尺度物体特性的影响。未被充分代表的少数族裔学生是通过爱荷华大学模范指导中心招收的。此外，所有人员都参与教育发展和推广活动，旨在向爱荷华州K-12年级的学生介绍科学。具体来说，海斯博士开发了一个“事物的大小”展览，用于展示纳米尺度和宏观尺度物体的大小的学习游戏。他们以公共电视台（DragonTV on Nano）开发的教育活动为基础，提供与(1)什么是纳米相关的互动活动？十亿米有多大？十亿分之一米有多小？(2)为什么“纳米金”是红色而“纳米银”是黄色？(3)我的纳米银袜子没有气味，但我是否应该担心纳米银会进入我的身体？该项目寻求关于如何以及为什么一些分子难以使用SERS检测的答案。尽管使用SERS直接检测小分子有许多成功的例子，但至少存在三个问题，包括：(1)聚集引起的纳米材料不可预测的特性，(2)某些类别的分子与表面的低效结合，以及(3)与目标分子相关的低信号。这两个研究问题的答案是不同的纳米颗粒形态和溶液条件。研究任务集中于定量分子结合指标和SERS增强，以及评估溶液条件如何影响结合指标、纳米颗粒稳定性和SERS活性。确定了关键的实验设计特征，从而促进了吸附物-表面相互作用的合理和可重复性，从而促进了使用表面增强光谱直接检测分子。学生在纳米科学，光谱学和测量科学领域进行培训。通过支持的研究，Haes研究小组正在制定设计规则，克服当前的测量挑战，从而扩大SERS在各种应用中的效用。

New biological, chemical, and radiological agents threaten the environment and human safety every day. While significant advances in small molecule detection have been made, challenges still exist in providing flexible detection methodologies for accurate chemical identification and sensitive and selective detection of some molecules. With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Haes at the University of Iowa focuses on developing surface sensitive techniques such as surface enhanced Raman scattering (SERS) as a tool molecular detection. SERS is a light-based technique that is used to identify and quantify molecules that adsorb onto metal surfaces. Most molecules do not stick to metal surfaces, limiting the utility of SERS and similar methods. Professor Haes and her group use both experimental and modeling methods to develop the SERS technique so that it can be used to provide accurate chemical identification with high selectivity and sensitivity. Through this research, Professor Haes provides opportunities to graduate and undergraduate students to work on practical problems. The Haes research group performs outreach activities with K-12 students that are focused on the "Size of Things". This project helps students learn about the implications of size on the properties of nanoscale and macroscale objects through hands-on activities. Underrepresented minority students are recruited through the University of Iowa's Center of Exemplary Mentoring. In addition, all personnel participate in educational development and outreach activities geared towards introducing science to Iowa's students in grades K-12. Specifically, Dr. Haes develops a "Size of Things" exhibit for display with a learning game for the size of nanoscale and macroscale objects. They build off of educational activities developed by Public Television (DragonTV on Nano)and provide interactive activities related to (1) What is a nanometer? How big is one billion meters? How small is one-billionth of a meter?; (2) Why is "nanogold" red and "nanosilver" yellow?; and (3) My nanosilver socks do not smell but should I be worried that the nanosilver will get into my body? This project seeks answers regarding how and why some molecules are difficult to detect using SERS. Despite many successful examples of direct small molecule detection using SERS, at least three issues remain including: (1) unpredictable properties of nanomaterials that arise from aggregation, (2) inefficient binding of some classes of molecules to surfaces, and (3) low signals associated with targeted molecules. The two research questions are answered by varying nanoparticle morphology and solution conditions. Research tasks focus on quantifying molecular binding metrics and SERS enhancements and evaluating how solution conditions impact binding metrics, nanoparticle stability, and SERS activity. Key experimental design features are identified so adsorbate-surface interactions are rationally and reproducibly promoted thus facilitating direct detection of molecules using surface-enhanced spectroscopies. Students are trained in the areas of nanoscience, spectroscopy, and measurement science. Through the supported research, the Haes research group is developing design rules that overcome current measurement challenges thus expanding the utility of SERS in a variety of applications.