Nanoindentation of Molecular Crystals: Lessons Learned from Aspirin.
Nanoindentation of Molecular Crystals: Lessons Learned from Aspirin.
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DOI：
10.1021/acs.cgd.0c00635
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发表时间：
2020-09-02
影响因子：
3.8
通讯作者：
Cruz-Cabeza AJ
中科院分区：
文献类型：
--
作者：
Gabriele BPA;Williams CJ;Lauer ME;Derby B;Cruz-Cabeza AJ
纳米压痕能够测量几微米尺寸的单晶的机械性能。然而，这种实验技术直到最近才被应用于分子晶体。这种技术的应用分子晶体和金属和其他无机物之间的关键区别被确定。由此，提出了用于测量具有药用价值的分子晶体的硬度和弹性模量的方案。使用I型阿司匹林作为模型系统，探讨了单晶样品表面制备（洗涤和切割）对表面粗糙度的影响。我们使用的校准样品的硬度和刚度接近的分子晶体的采集更准确的数据的重要性。晶体生长过程中形成的溶剂闭塞的问题进行了讨论，作为材料性能变化的来源，以及尖端污染。有人提出，这在一定程度上解释了显着更大的变化，不同的单晶之间的测量的机械性能相比，在一个独特的样品上进行。由于压痕模量和硬度对于低深度压痕可以显著变化，因此在宽范围的深度上对样品进行测试，这揭示了获取数据所需的最小穿透深度。这个实验是至关重要的，需要对每个研究中的系统进行，因为它可以确定最小工作负载。压痕后成像与晶体学分析和分子模拟相结合，可以表征和合理化的材料塑性变形机制。我们分享我们在分子晶体纳米压痕方面的实践经验。虽然这种技术已被广泛应用于金属和无机物，但分子晶体的操作方面很少被考虑。讨论了分子晶体纳米压痕的关键问题，从标定样品的选择到最佳压痕条件和成像。
Nanoindentation enables the measurement of mechanical properties from single crystals with dimensions of a few micrometers. This experimental technique, however, has only recently been applied to molecular crystals. Key differences between the application of this technique to molecular crystals and metals and other inorganics are identified. From this, protocols for the measurement of hardness and elastic modulus of molecular crystals of pharmaceutical interest are proposed. Using form I aspirin as a model system, the impact of single crystal sample surface preparation (washing and cleaving) on the surface roughness is explored. We show the importance of using a calibration sample with hardness and stiffness close to that of molecular crystals for the acquisition of more accurate data. The issue of solvent occlusions formed during crystal growth is discussed as a source of material property variation as well as tip contamination. It is proposed that this in part explains the significantly larger variation of the measured mechanical properties among different single crystals compared to those performed on a unique sample. Because both the indentation modulus and the hardness can vary significantly for low depth indents, samples were tested over a wide range of depths, which revealed that a minimum depth of penetration is required for the acquisition of data. This experiment is crucial and needs to be carried out for every system under study since it allows for the determination of the minimum-working load. Post-indentation imaging combined with crystallographic analysis and molecular simulations allows for the characterization and rationalization of the material plastic deformation mechanisms. We share our practical experience in nanoindentation of molecular crystals. While this technique has been widely applied to metals and inorganics, operational aspects specific to molecular crystals had less often been considered. We discuss key aspects for nanoindentation of molecular crystals from the choice of calibration sample to best indentation conditions and imaging.
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影响因子：
3.8
作者：
Bauer, Johannes D.;Haussuehl, Eiken;Robertson, Struan
通讯作者：
Robertson, Struan
影响因子：
1.8
作者：
HARDING, MM;RULE, RJ;DAVEY, RJ
通讯作者：
DAVEY, RJ
影响因子：
3.8
作者：
Kiran, M. S. R. N.;Varughese, Sunil;Desiraju, Gautam R.
通讯作者：
Desiraju, Gautam R.
影响因子：
15
作者：
Krishna, Gamidi Rama;Devarapalli, Ramesh;Reddy, C. Malla
通讯作者：
Reddy, C. Malla
影响因子：
2.7
作者：
Kaufman, Jessica D.;Miller, Gregory J.;Klapperich, Catherine M.
通讯作者：
Klapperich, Catherine M.