Development of Scanning Nano-Raman Spectroscopy with Apertureless Near-Field Optics

继续纳米科学和纳米技术的最新进展需要发展具有纳米级横向分辨率的化学、构象和应力分析方法。核磁共振计划的这一奖项的目标是开发一种空间分辨率为10-50 nm的扫描拉曼光谱仪，具有强烈增强的光学信号。拟议工作的一个中心特征是使用无孔近场光学来提供拉曼信号强度的至少10X10的增益，而不是目前可用的基于光纤产生的孔径限制光学的商业仪器可以实现的增益。这种方法将提供精细的空间分辨率和使用扫描金属尖端的拉曼信号的大的局部增强。这种增强对于测量来自小体积的信号是绝对必要的。这项工作的长期目标是开发一种能够检测单分子的拉曼光谱仪。在实现这项工作的总体目标方面，将实现以下具体目标：(1)开发产生金属尖端的技术，提供对拉曼信号的强烈局部增强；(2)为特定的实验任务优化提供入射光和收集拉曼信号的不同光学方案；以及(3)构建具有纳米空间分辨率的扫描拉曼光谱仪原型。由核磁共振计划支持的扫描纳米拉曼光谱仪(SNRS)的开发将适用于几项科学活动。在研究人类血液蛋白在明确定义的表面上的吸附时，SNRS将提供关于蛋白质在吸附时构象变化的横向分辨信息。表面纳米结构域在嵌段共聚生物材料中的分布、胶原纤维的组装和纤维蛋白的形成是进一步的生物材料问题，SNRS仪器将为这些问题提供独特的信息。胶粘剂共混物表面化学成分的横向变化也可以用SNR来绘制，并与表面机械性能的变化相关联。在长支链和直链的混合物中，SNRS将提供一种横向分辨的非破坏性方法来研究具有同位素标记的混合物的近表面组成。它还将提供一种无需标记即可研究近表面成分的方法。其他研究活动包括研究聚合物刷和树枝状大分子的杂化纳米结构，绘制各种超薄膜的表面功能图，包括具有混合功能的自组装单分子膜。扫描纳米拉曼光谱仪的发展将对国家的学术研究基础设施产生重大影响，不仅是聚合物材料，还包括半导体技术、生物技术和生物学。它将提供前所未有的测量，将促进在纳米尺度上更好地理解材料的结构/性能关系。

Continuing the recent progress in nanoscience and nanotechnologies requires the development of methods of chemical, conformational, and stress analysis with nanoscale lateral resolution. The objective of this award from the MRI Program is to develop a scanning Raman spectrometer with spatial resolution of the order of 10-50 nm with a strongly enhanced optical signal. A central feature of the proposed work is the use of apertureless near- field optics to provide a gain of at least 10 exp.10 in intensity of the Raman signal over what may be achieved with currently available commercial instruments based on aperture-limited optics created with fibers. This approach will provide both exquisite spatial resolution and large local enhancement of the Raman signal using a scanning metallic tip. The enhancement is absolutely essential for measurement of the signal from small volumes. A long-term goal of the work is development of a Raman spectrometer capable of single molecule detection. The following specific objectives will be met in achieving the overall goal of the work: (1) Development of the technology for the creation of a metallic tip providing strong local enhancement of the Raman signal; (2) Optimization of different optical schemes for providing the incident light and collecting the Raman signal for particular experimental tasks; and (3) Construction of the scanning Raman spectrometer prototype with nanometer scale spatial resolution. Development of a scanning nano-Raman spectrometer (SNRS) supported under the MRI Program will be applicable to several scientific activities. In the study of adsorption of human blood proteins to well-defined surfaces, SNRS will provide laterally resolved information on conformational changes in the protein upon adsorption. The distribution of surface nano-domains in biomaterials from block copolymers, assembly of collagen fibrils, and fibrin formation are further biomaterials problems for which the SNRS instrument will provide unique information. Lateral variations in chemical composition at the surface of adhesive blends can also be mapped with SNRS and correlated with variations in surface mechanical properties. In blends of long-branched and linear chains SNRS will provide a laterally resolved alternative non-destructive method to study near surface composition in blends with isotopic labeling. It will also offer a means to study near surface composition without labeling. Additional research activities include the study of hybrid nanostructures from polymer brushes and dendrimers and mapping of surface functionality in ultrathin films of various sorts, including self-assembled monolayers with mixed functionalities. Development of the scanning nano-Raman spectrometer will have a significant impact on the Nation's academic research infrastructure not only polymeric materials, but also semiconductor technology, biotechnology and biology. The unprecedented measurements it will provide will promote better understanding of structure/property relationships in materials on the nanometer scale.