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Flash Brillouin Scattering: A Confocal Technique for Measuring Glass Transitions at High Scan Rates
ACS Photonics ( IF 6.5 ) Pub Date : 2020-12-28 , DOI: 10.1021/acsphotonics.0c01533
Konrad Rolle 1 , Hans-Jürgen Butt 1 , George Fytas 1
Affiliation  

Glass transition temperatures Tg are most commonly measured by differential scanning calorimetry, a method that has been extended to the flash scanning calorimetry (FSC) regime by reducing sample volumes. However, significant manual preparation effort can render FSC impractical for, e.g., local probing of spatially heterogeneous specimens. Another strategy can be to select a small volume by focusing down a laser beam, where Brillouin Light Scattering (BLS) is a proven method for confocal Tg measurement. Here, we introduce Flash Brillouin Scattering, which extends BLS to fast scan rates, achieved by periodically heating the probed region with an infrared laser. For comparison with conventional BLS, we first characterize Tg of pure glycerol, and show how rapid quenching produces a less packed glass with downshifted sound velocity. We then turn toward its aqueous solutions, which crystallize too fast for a nonflash approach, and demonstrate scan rates in excess of 105 K/s. These results are of interest not only because glycerol is a model system for hydrogen-bonded glass formers, but also because of its applications as a cryoprotectant for frozen biological samples. Light scattering studies of the latter, currently limited to cryo-Raman spectroscopy, are likely to be complemented by the technique introduced here.

中文翻译:

闪烁布里渊散射:一种用于在高扫描速率下测量玻璃化转变的共焦技术

玻璃化转变温度T g最通常通过差示扫描量热法测量,该方法已经通过减少样品量而扩展至快速扫描量热法(FSC)。但是,大量的手工准备工作可能会使FSC在例如空间异质标本的局部探测中不切实际。另一种策略是通过聚焦激光束来选择较小的体积,其中布里渊光散射(BLS)是用于共焦T g测量的行之有效的方法。在这里,我们介绍了Flash布里渊散射,它将BLS扩展到快速扫描速率,这是通过用红外激光定期加热探测区域来实现的。为了与常规BLS进行比较,我们首先表征T g并展示了快速淬火是如何产生声速低移的填充较少的玻璃的。然后,我们转向其水溶液,该水溶液结晶速度太快,无法进行非闪光处理,并显示出超过10 5 K / s的扫描速率。这些结果令人关注,不仅因为甘油是氢键玻璃形成剂的模型系统,而且还因为它可用作冷冻生物样品的冷冻保护剂。后者的光散射研究目前仅限于低温拉曼光谱,可能会被此处介绍的技术所补充。
更新日期:2021-02-17
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