Name: Creating Topographical and NanoIR Images of the Multipolymer Sample
Uploaded: 2023-06-23T14:55:00
Description: Watch this Scientific Journal Video about Creating Topographical and NanoIR Images of the Multipolymer Sample at JoVE.com

creating topographical and nanoir images of the multipolymer sample

通过纳米级红外光谱探索多相聚合物系统

Atomic force microscopy (AFM) has become essential to image and characterize the morphology of a wide variety of samples with nanoscale resolution1,2,3. By measuring the deflection of an AFM cantilever resulting from the interaction of the sharp tip with the sample surface, nanoscale functional imaging protocols for local stiffness measurements and tip-sample adhesion have been developed4,5. For soft condensed matter and polymer analysis, AFM measurements exploring the nanomechanical and nanochemical properties of local domains are highly sought after6,7,8. Before the emergence of nanoscale infrared (nanoIR) spectroscopy, AFM tips were chemically modified to assess the presence of different domains from the AFM force curve and deduct the nature of the tip-sample interaction. For instance, this approach was used to unveil the transformation of microdomains of poly(tert-butyl acrylate) at the surface of cyclohexane-treated polystyrene-block-poly(tert-butyl acrylate)block copolymer thin films at the sub 50 nm level9.
The combination of infrared (IR) light with AFM has had a significant impact on the field of polymer science6. Conventional IR spectroscopy is a widely used technique for studying the chemical structure of polymeric materials10,11, but it fails to provide information on individual phases and interphase behavior, as the regions are too small compared to the size of the IR beam used to probe the sample. The problem holds with IR microspectroscopy, as it is restricted by the optical diffraction limit6. Such measurements average the contributions of the entire region excited by the IR light; the signals resulting from the presence of nanoscale phases inside the probed region either exhibit complex fingerprints that should be deconvoluted during post-processing or are lost due to a signal level below the detectable level. Hence, it is essential to develop tools capable of nanoscale spatial resolution and high IR sensitivity to explore nanoscale chemical features in complex media.
Schemes to achieve nanoIR spectroscopy have been developed, first using a metallic AFM tip as a nanoantenna12,13, and more recently exploiting the AFM cantilever&#39;s ability to monitor changes in the photothermal expansion incurred during IR illumination of the sample12,14,15. The latter uses a pulsed, tunable IR light source tuned to an absorption band of the material probed, which causes the sample to absorb radiation and undergo photothermal expansion. This approach is well-suited for organic and polymeric materials. The pulsed excitation makes the effect detectable by the AFM cantilever in contact with the sample surface in the form of an oscillation. The amplitude of one of the contact resonances of the system observed in the frequency spectrum is then monitored as a function of illumination wavelength, which constitutes the nanoIR absorption spectrum of the material beneath the AFM tip15. The spatial resolution of nanoIR imaging and spectroscopy is limited by various effects of the photothermal expansion of the material. It has been evaluated that photothermal nanoIR spectroscopy using contact mode AFM can acquire the vibrational absorption spectra properties of materials with sub 50 nm scale spatial resolution14, with recent work demonstrating the detection of monomers and dimers of &#945;-synuclein16,17. However, quantitative studies of the performance of nanoIR measurements on heterogeneous polymeric materials assembled in various configurations, such as the case of absorbers of finite dimensions embedded in the volume of various polymeric films, remain limited.
This article aims to create a polymeric assembly with an embedded feature of a known dimension to evaluate the sensitivity of photothermal expansion and spatial resolution of nanoIR during surface analysis. The protocol covers the preparation of a polyvinyl alcohol (PVA) polymer thin film on a silicon substrate and the placement of a three-dimensional polystyrene (PS) bead onto or embedded in the PVA film, which constitutes the formation of the model system. NanoIR imaging and spectroscopy measurements are described in the context of evaluating the signals generated by the same PS bead positioned on or beneath the PVA film. The influence of the bead position on the nanoIR signals is evaluated. Methods to assess the spatial footprint of the bead in the nanoIR map are discussed, and the effects of several parameters are considered.

作者聚焦：探索多相聚合物系统的纳米级红外光谱进展  

纳米级红外光谱探索多相聚合物体系的进展

Our group focuses on advancing the field of nanoscale functional imaging and spectroscopy to study complex systems with an emphasis on nanoscale infrared spectroscopy. Our research aims to develop methods that allows us to make sense of the behavior of heterogeneous systems by studying their nanoscale properties. Understanding the role of actuations at different frequencies to extract information about the sample is essential.As this is complicated, developing samples that can be modeled with physics simulation packages is also important. A nanoscale infrared spectroscopy determining the penetration depth of the measurement and understanding how subsurface features affect the signal detected by the AFM tip is very important. This protocol proposes a simple approach to create a model system that enables quantifying the penetration depth of nanoscale infrared spectroscopy, and the effect of JUUL heating on the sample response involved in the measurement of multi-phase polymer materials.Our team will continue to focus on developing new ideas to improve nanoscale infrared spectroscopy and other nanoscale functional tools to explore real-life systems at a small scale.

Watch this Scientific Journal Video about Creating Topographical and NanoIR Images of the Multipolymer Sample at JoVE.com

Creating Topographical and NanoIR Images of the Multipolymer Sample  

创建多聚物样品的形貌和纳米红外图像

对于 NanoIR 测量，将原子力显微镜 （AFM） 放在从形貌图像中识别出的感兴趣特征上。选择 NanoIR 控制面板中的音叉图标以确定悬臂的接触谐振频率。然后设置一个照明波数来激发材料中的光热膨胀。接下来，设置要扫描的激光脉冲频率范围，并设置NanoIR激光器的占空比。在激光脉冲调谐窗口中选择采集。将标记条定位在峰上，以选择尖端样品系统的第二个接触共振，以进行 NanoIR 测量。单击优化按钮，将红外激光焦点区域的中心与悬臂尖端的位置对齐。获取红外激光照明背景。选择 NanoIR 光谱的波数范围、步长和平均值数。然后通过将光热振幅除以衰减的背景来对光谱进行背景校正。在激光脉冲调谐窗口中启用锁相环或PLL自动调谐。然后调整最大和最小频率，以在常规控制面板中以第二谐振模式为中心的扫描范围。单击PLL控制面板中的零，然后单击激光脉冲调谐窗口中的确定。通过选中 NanoIR 控制面板中启用的 IR 成像复选框来启用 IR 成像。在成像视图控制面板中，选择高度、振幅二和相位二，以获取样品的形貌和化学图像。然后将采集方向设置为跟踪或回溯。选择 AFM 扫描控制面板中的扫描图标。然后在捕获控制面板中选择现在或帧结束图标以保存图像。要导出数据，请右键单击数据列表中的图像或光谱文件名。选择“导出”，然后选择要导出的文件格式。最后，将文件保存在所需的计算机文件夹中。聚苯乙烯的NanoIR光谱产生了两个红外波段，对应于苯基部分在1， 600波数处的拉伸模式和在1， 730波数处拉伸的环子集。PVA的NanoIR光谱与FDIR光谱表现出更好的一致性，主要吸收带以1， 730波数为中心。NanoIR光谱用于选择沉积在PVA表面的聚苯乙烯珠和涂有PVA的聚苯乙烯珠的化学成像的照明波数。接下来，在不同激光功率下，在覆盖有PVA的聚苯乙烯珠上收集光谱。聚苯乙烯在1， 600波数处的信号显著低于PVA在1， 750波数处的信号。然而，有人指出，增加激光功率会导致更高的比率。

Research

JoVE Journal

Engineering

Creating Topographical and NanoIR Images of the Multipolymer Sample

Advances in Nanoscale Infrared Spectroscopy to Explore Multiphase Polymeric Systems

Multiphase polymeric systems encompass local domains with dimensions that can vary from a few tens of nanometers to several micrometers. Their composition ...