原位水中石粒子的液体扫描电镜表征
Summary
本文采用原位液体扫描电子显微镜对去离子水中的石颗粒进行 real-time 成像和元素组成分析。
Abstract
原位水中石 (AlOOH) 粒子的成像和元素分析是利用系统进行液体真空界面 (chomiak-salvi) 和扫描电子显微镜 (SEM) 的分析而实现的。本文介绍了将真空相容 SAVLI 与扫描电镜相结合, 获得高真空液中颗粒的二次电子 (SE) 图像的方法和关键步骤。能量色散 x 射线光谱学 (EDX) 用于获得液体和控制样品中的颗粒元素分析, 包括只去离子水和空通道。合成的石 (AlOOH) 颗粒悬浮在液体中作为一个模型在液体 SEM 插图。结果表明, 粒子可以在 SE 模式下成像, 分辨率很好 (即, 400 nm)。与 DI 水和空通道控制相比, AlOOH EDX 谱显示了铝 (Al) 的显著信号。原位液体扫描电镜是一种强有力的技术来研究液体中的微粒与许多令人兴奋的应用。本程序旨在提供技术 know-how, 以进行液体扫描电镜成像和 EDX 分析使用 chomiak-salvi 和减少潜在的陷阱时, 使用这种方法。
Introduction
扫描电子显微镜 (SEM) 被广泛应用于研究各种标本的高分辨率成像1。与 SEM 相关的能量色散 x 射线光谱 (EDX) 能够测定元素组成1。传统上, SEM 是用于成像只有干和固体样品。在过去30年中, 开发了环境扫描电镜 (镜) 分析的部分水合样品在蒸汽环境2,3,4,5。然而, 镜无法图像的湿, 完全流体样品与理想的高分辨率6。用 sem7,8对湿法样品进行了扫描电镜成像。然而, 这些细胞主要开发为生物标本和散射电子成像, 并且为应用是更容易接近的为那些设计9,10。
为了解决在使用 SEM 分析其本机液态环境中的各种样品时所面临的挑战, 我们发明了一种真空兼容微流控装置, 用于在液体真空界面 (chomiak-salvi) 上进行分析, 以使高空间分辨率的次级用扫描电镜中的高真空模式对液体样品进行电子 (SE) 成像和元素分析。这项新技术包括以下独特的特点: 1) 液体在直径为 1-2 µm 的小孔径中直接探测;2) 液体通过表面张力在孔内举行;和 3) chomiak-salvi 是便携的, 可以适应多个分析平台11,12,13,1415,16,17 ,18。
chomiak-salvi 由100纳米厚的氮化硅 (SiN) 膜和200µm 宽的微通道组成, 由烷 (矽) 块制成。应用原膜窗口密封微通道。在以前的论文和专利11、19、20中详细介绍了制造细节和关键设计考虑事项。目前, 一家领先的显微镜耗材制造商和分销商已经购买了销售 chomiak-salvi 设备的许可证, 以商用的液体扫描电镜应用21,22。
chomiak-salvi 在 vacuum-based 分析仪器中的应用已被证明使用各种水溶液和复杂的液体混合物, 包括生物膜, 哺乳动物细胞, 纳米粒子和电极材料12,14,17,20,23,24. 然而, 上述工作大多采用飞行时间二次离子质谱法作为关键的分析工具, 因此尚未充分探讨液体 chomiak-salvi 扫描电镜的应用. 在这项工作中, chomiak-salvi 已被用来研究更大的非胶体微粒液体利用 SEM 成像和 EDX 元素分析。样品由我们实验室合成的 AlOOH 颗粒组成。Submicrometer-sized 石颗粒是已知的高放射性废物在汉福德网站上存在。它们是缓慢的溶解, 并可能导致流变问题的废物处理。因此, 有能力在液体25中表征石粒子是很重要的。这种技术方法可用于研究石在各种物理化学条件下, 以提高对这些微粒和相关流变特性的认识。为了研究悬浮在液体中的颗粒, 利用这些粒子 step-by 了如何将 chomiak-salvi 应用到高真空扫描电镜中。文中重点介绍了 chomiak-salvi 和 sem 集成以及 sem 数据采集的关键技术要点。
该协议提供了液体样品分析使用 chomiak-salvi 和液体 sem 成像, 对于那些谁有兴趣利用这一新技术在不同应用的液体 sem 在未来的演示。
Protocol
Representative Results
Discussion
SEM 是一种功能强大的技术在表面表征的有机和无机材料的纳米 (nm) 水平高分辨率1。例如, 它被广泛用于分析固体和干燥样品, 如地质材料26和半导体27。然而, 由于在电子显微镜1所需的高度真空环境中液体的不相容性, 它对湿和液体样品的定性有局限性。SEM 样品制备通常需要脱水或 freeze-drying 的水合标本, 特别是生物标本<sup cl…
Disclosures
The authors have nothing to disclose.
Acknowledgements
我们感谢太平洋西北国家实验室 (4500亿) 核过程科学倡议 (NPSI)-实验室定向研究和发展基金 (LDRD) 的支持。Dr. Sayandev 查特吉提供了合成的石粒子。通过格雷斯威利环境分子科学实验室 (emsl-lv) 的一般用户提案提供了仪器接入。emsl-lv 是一个由生物和环境研究办公室 (BER) 在4500亿主办的国家科学用户设施。4500亿由巴特尔在合同 DE-AC05-76RL01830 下经营。
Materials
| Carbon Coater | Cressington | 208 Carbon | It is accompanied with thickness monitor MTM-10. |
| SEM | FEI | Quanta 3D FEG | It provides highly resolved scanning electron microscopy and elemental analysis. |
| System for Analysis at the Liquid Vacuum Interface (SALVI) | Pacific Northwest National Laboratory | N/A | SALVI is a unique, vacuum compatible microfluidic cell that enables the characterization of the liquid sample using vacuu- based scientific instrument. |
| PEEK Union | Valco | ZU1TPK | The polyether ether ketone union is used for connecting the inlet and outlet of SALVI |
| Syringe | BD | 309659 | 1 mL |
| Pipette | Thermo Fisher Scientific | 21-377-821 | Range: 100 to 1,000 mL |
| Pipette Tip 1 | Neptune | 2112.96.BS | 1,000 µL |
| Pipette Tip 2 | Rainin | 17001865 | 20 µL |
| Syringe Pump | Harvard Apparatus | 70-2213 | It is used to inject the liquid sample into the SALVI device. |
| pH meter | Fisher Scientific/accumet | 13-636-AP72 | It is used for measuring the pH of AlOOH in DI water. |
| Barnstead Ultrapure Water System, UV/UF | Thermo Scientific Barnstead | Nanopure diamond D11931 | It is used for producing DI water. |
| Centrifuge tubes | Fisher scientific/Falcon | 15-527-90 | 15 mL |
| Bransonic ultrasonic cleaner | Sigma-Aldrich | 2510 | It is used to ultrasonicate the AlOOH liquid sample. |
| Balance | Mettler Toledo | 11106015 | XS64 |
| AlOOH | Pacific Northwest National Laboratory | N/A | It is synthesized by scientists at Pacific Northwest National Laboratory. |
| xT microscope Control | FEI | Quanta 3D FEG | Default microscope control software of SEM Quanta 3D FEG |
| EDAX Genesis software | EDAX | N/A | The software is used for collecting the EDX elemental information of the samples. |
| Teflon tubing | SUPELCO | 58697-U | It is used for introducing the sample into the microchannel and holding adequate volume of liquid. |
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