MRI: Development of a New Paradigm for Apertureless Near-field Scanning Optical Microscope

MRI：无孔径近场扫描光学显微镜新范例的开发

• 批准号: 0723118
• 负责人: Gang-Yu Liu
• 金额: $ 37.47万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0723118&HistoricalAwards=false
• 关键词: MRI; Development; New; Paradigm; Apertureless

We propose to construct a state-of-the-art tool for imaging materials with high magnification, e.g. visualizing groups of molecules and being able to identify them. Conventional optical microscopes, e.g. a magnifying glass, only allow visualization at micrometer scale, i.e. a fraction of a human hair. This is due to the diffraction limit of visible lights. Using a sharp tip scanning over material surfaces, atomic force microscope enables imaging materials at nanometer level (a small fraction of a human hair), however, provides no information as to what kind of materials (metals, polymers or ions) are under the tip. One mission in the materials science community is to combine the strength of the high resolution in atomic force microscope with the ability to identify materials shown by optical microscope. The new instrument is referred to as a near-filed scanning optical microscope. The task is not trivial due to two competing factors, the need for sufficient light intensity at the imaging site (e.g. using a large probe) and the requirement to make the probe small/sharp to attain optical resolution. This proposal will use a new methods derived from our finding that specific kind of sharp probes glow when one focuses a laser beam at the top tips. The glowing tips provide a "point light source" for imaging and spectroscopy. Preliminary results have demonstrated the feasibility of generating near-filed signals, and we plan to complete the construction of this instrument, to optimize the performance and to demonstrate its applications. Compared with past approaches towards this technique, the proposed method exhibits advantages of high intensity of light, simple to operate, and high resolution. We plan to demonstrate the application and capability of this new instrument by characterization of four classes of important materials: materials containing organic (polymeric) and inorganic (semiconductive) compositions; small inorganic particles with multiple components; carbon nanofibers; and nanomaterials in living cells. The development of this new technique should bring students and postdocs to the forefront of scanning probe microscopy technology and its applications in materials science. The completion of this instrument will enhance the Spectral Imaging Facility (led by the PI) at UCD. We propose a new paradigm for near-field scanning optical microscopy (NSOM). The idea derives from a finding that microfabricated atomic force microscopy (AFM) probes exhibit photoluminescence (PL) upon excitation by a focused laser beam. This PL tip provides a "point light source" for NSOM imaging and spectroscopy. The excitation beam will be focused onto the surface with polarization component perpendicular to the tip axe, as at such we attain laterally localization and enhancement by the AFM tip. Preliminary results have demonstrated the feasibility of generating near-filed signals, and we plan to complete the construction of this instrument, to optimize the performance and to demonstrate its applications. The intrinsic advantages of this approach include: (a) high photon throughput with the ability to tune wavelength; (b) simplicity in detection of near-field optical signals because the PL exhibits different wavelength from the excitation beam; (c) high spatial resolution due to the apertureless AFM platform with sharp probes and effective deflection feedback; and (d) simplicity in operation. Any AFM users should be able to master the operation of this NSOM with a quick training of ca. one week. Development plan includes: (a) design and construction of a low mechanical noise and high stability AFM/NSOM scanning assembly to attain high spatial resolution (10 nm in lateral and 2 nm in normal directions); and (b) attaining true NSOM signal and local spectroscopy information, for which we plan to modify AFM probes to improve the PL efficiency, to build the excitation path and configuration for high near-field enhancement, and to build a high sensitivity and selectivity detection of near field signals. Combining expertise of NSOM instrumentation (Liu), nanofibers and wave guides (Guo), polymer nanocomposite materials (Patten) and nanoparticles with novel applications (Kauzlarich), we plan to use this NSOM for: (a) revealing the protein complex formed at the cell focal adhesion on nanostructures of ligands; (b) investigating the structure and optical property of polymer-nanoparticle composite materials; (c) measuring the structure and wave-guide property of nanowires and nanowire assemblies; and characterizing the structure and optical property of single magnetic core / metal shell particles. The development of this NSOM should bring students and postdocs to the forefront of scanning probe microscopy technology. Students will have a chance to learn and master the skills for the instrumentation of state-of-the-art AFM, optics and detections of optical signals, hardware design for low noise and high stability, electronics for microscopy, and software macros for NSOM. In addition, they will also investigate local interactions between optical excitation and AFM tip, tip-sample interaction, and contrast mechanism for a variety of materials as the initial exploration for NSOM applications in materials research. The completion of this NSOM will enhance the Spectral Imaging Facility (led by the PI) at UCD's organized research unit known as NEAT. The proposed research projects will facilitate further applications of using NSOM for material characterization to reveal the topographic as well as the functionality of the local structures.

我们建议构建一种最先进的工具，用于成像具有高放大倍数的材料，例如可视化分子组并能够识别它们。 常规光学显微镜，例如放大镜，仅允许以千分尺的比例可视化，即一小部分人头发。 这是由于可见光的衍射极限。 但是，在材料表面上尖锐的尖端扫描，原子力显微镜可以在纳米水平（一小部分人的头发）上实现成像材料，但没有提供有关哪种材料（金属，聚合物或离子）在尖端下方的信息。 材料科学界的一个任务是将原子力显微镜高分辨率的强度与识别光学显微镜显示的材料的能力相结合。 新仪器称为近乎修复的扫描光学显微镜。 由于两个竞争因素，该任务并非微不足道，需要在成像位点进行足够的光强度（例如，使用大型探针）以及使探针较小/尖锐以达到光学分辨率的要求。 该提案将使用一种从我们发现的新方法中得出的新方法，即当人们将激光束聚焦在最重要的尖端时，特定的尖锐探针发光。 发光的尖端为成像和光谱法提供了“点光源”。 初步结果证明了生成近乎修订的信号的可行性，我们计划完成该工具的构造，以优化性能并演示其应用。 与过去的这种技术方法相比，所提出的方法具有高强度，易于操作和高分辨率的优势。 我们计划通过表征四类重要材料的表征来证明这种新仪器的应用和能力：含有有机（聚合物）和无机（半导体）组成的材料；具有多个组分的小无机颗粒；碳纳米纤维；和活细胞中的纳米材料。 这项新技术的开发应将学生和博士后带到扫描探针显微镜技术及其在材料科学中的应用的最前沿。 该仪器的完成将增强UCD处的光谱成像设施（由PI领导）。 我们提出了一个用于近场扫描光学显微镜（NSOM）的新范式。 该想法来自一个发现，焦点激光束激发后，微生物原子力显微镜（AFM）探针表现出光致发光（PL）。 该PL尖端为NSOM成像和光谱法提供了“点光源”。 激发光束将以垂直于尖端轴的极化成分聚焦到表面上，因为在这种情况下，我们可以通过AFM尖端横向定位和增强。 初步结果证明了生成近乎修订的信号的可行性，我们计划完成该工具的构造，以优化性能并演示其应用。 这种方法的固有优势包括：（a）具有调节波长能力的高光​​子吞吐量； （b）检测近场光学信号的简单性，因为PL表现出与激发光束不同的波长； （c）由于无尖锐的AFM平台而引起的高空间分辨率，并具有尖锐的探针和有效的挠度反馈； （d）操作中的简单性。 任何AFM用户都应该能够通过快速培训CA掌握该NSOM的操作。一周。 开发计划包括：（a）设计和构建低机械噪声和高稳定性AFM/NSOM扫描组件，以达到高空间分辨率（侧向10 nm，正常方向为2 nm）； （b）获得真正的NSOM信号和局部光谱信息，我们计划修改AFM探针以提高PL效率，以建立激发路径和配置，以实现高近场增强的高度，并构建近场信号的高灵敏度和选择性检测。 结合NSOM仪器（LIU），纳米纤维和波浪指南（GUO），聚合物纳米复合材料（Patten）和纳米颗粒与新颖应用（Kauzlarich）（Kauzlarich），我们计划使用此NSOM来进行：（a）揭示在细胞局部在Nananosstirons of Nananosstress的蛋白质复合物形成的蛋白质复合物， （b）研究聚合物 - 纳米颗粒复合材料的结构和光学特性； （c）测量纳米线和纳米线组件的结构和波化特性；并表征单磁芯 /金属壳颗粒的结构和光学特性。这种NSOM的开发应将学生和博士后带到扫描探针显微镜技术的最前沿。 学生将有机会学习和掌握最先进的AFM仪器的技能，光学信号的光学和检测，低噪声和高稳定性的硬件设计，显微镜的电子设备以及NSOM的软件宏。 此外，他们还将研究光激发与AFM尖端，尖端样本相互作用以及各种材料的对比机制之间的局部相互作用，作为材料研究中NSOM应用的初步探索。 该NSOM的完成将增强UCD有组织的研究单元的光谱成像设施（由PI领导）。 拟议的研究项目将促进将NSOM用于材料表征揭示地形以及局部结构的功能的进一步应用。