A Multifocal Approach for Improving the Speed of 1064 nm Raman Microscopy

在化学系化学测量与成像项目的支持下，加州大学戴维斯分校的陈教授正在开发一种新的成像仪器来观察化学样品。他计划设计并制造一种显微镜，可以提高成像速度，并且可以进入深红外区域（1064nm波长激发），这将允许检测深层嵌入的化学物质。陈教授的新仪器有望在许多领域发挥作用，包括法医学、药剂学、考古学和农业等。陈教授还计划与他在内华达大学里诺分校的合作者合作，将这种方法应用于研究植物组织从环境中吸收纳米粒子的过程。他们感兴趣的特定类型的纳米颗粒，碳纳米管（CNT），被用于许多商业产品，它们不可避免地释放到环境中，造成许多潜在的环境、食品安全和人类健康问题。了解碳纳米管吸收到植物材料中的基本机制对于减轻这种影响非常重要。这项研究工作的合作性质为参与的学生提供了化学测量和环境工程界面的独特体验。它还促进了加州大学戴维斯分校和内华达大学里诺分校的跨学科科技活动。为配合这项研究，陈教授现正发展一项教育及外展计划，让本地高中及大学本科生参与。提高成像速度是拉曼显微镜领域面临的主要挑战。这个项目的重点是通过开发一种新的多焦点系统来解决这个问题，该系统旨在同时检测样品内多个区域的光谱。这种多焦点设计产生一个二维激光光斑阵列来照亮样品，激光光斑通过使用快速扫描镜以确定的模式扫描激光束来快速打开和关闭，以获得一系列叠加的光谱数据，然后反卷积以最小的光谱串扰从每个激光焦点检索单个光谱。该项目的目标是将该设计集成到配备砷化铟镓（InGaAs）光电二极管线性阵列的1064 nm拉曼显微镜中，并在快速读出速率下展示改进的成像速度。研究了成像速度和信噪比与不同尺寸的激光焦阵列的关系，确定了最优的多焦设计。然后使用该仪器利用碳纳米管的特征g波段和d波段拉曼特征对被吸收到植物组织中的碳纳米管进行成像。将根据拉曼图像确定和量化碳纳米管的摄取和保留时间以及空间分布。微生物活性（多环芳烃（PAH）降解细菌）对碳纳米管降解的影响及其对碳纳米管植物吸收动力学的影响将被研究。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。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Chan at the University of California, Davis, is developing a new imaging instrument to look at chemical samples. He plans to design and build a microscope that can improve the imaging speed and can go to the deep infared region (1064 nm wavelength excitation), which would allow the detection of deeply embedded chemical species. Professor Chan's new instrument is expected to be useful in many areas, including forensics, pharmaceutics, archaeology, and agriculture, to name a few. Professor Chan also plans to work with his collaborator in University of Nevada, Reno, to apply this method to study the uptake of nanoparticles from the environment in plant tissue. The particular type of nanoparticles they are interested in, carbon nanotubes (CNT), are used in many commercial products and their inevitable release into the environment poses many potential environmental, food safety, and human health concerns. Understanding the fundamental mechanisms of CNT uptake into plant materials is very important to mitigate this effect. The collaborative nature of this research effort provides participating students with unique experience at the interface of chemical measurement and environmental engineering. It also promotes cross-disciplinary activities in science and technology at UC Davis and University of Nevada, Reno. In synergy with the research, Professor Chan is developing an education and outreach program to include participation of local high school and college undergraduate students. Improving imaging speed is a major challenge in the field of Raman microscopy. This project is focused on addressing this issue by developing a novel multifocal system designed to detect spectra from multiple regions within a specimen simultaneously. This multifocal design generates a 2-D array of laser spots that illuminate the sample, and the laser spots are rapidly turned on and off by scanning the laser beam using fast scan mirrors in defined patterns to acquire a series of superimposed spectral data that is then deconvoluted to retrieve the individual spectra from each laser focus with minimal spectral crosstalk. The goal of this project is to integrate this design into a 1064 nm Raman microscope equipped with an indium gallium arsenide (InGaAs) photodiode linear array and to demonstrate improved imaging speeds at fast read out rates. The imaging speed and signal-to-noise ratio is characterized as a function of different sized laser focal array patterns and the optimal multifocal design is determined. This instrument is then used to image carbon nanotubes that have been uptaken into plant tissues using the characteristic G-band and D-band Raman signatures of CNTs. Uptake and retention times, as well as spatial distribution of the CNTs are to be determined and quantified based on the Raman images. The effect of microbial activity (polycyclic aromatic hydrocarbon (PAH)-degrading bacteria) on CNT degradation and its impact on CNT plant uptake dynamics is to be investigated.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.