Tang Weiwei, Yang Taimin, Tu Qing, Calderon Hector A, Robles Hernandez Francisco C, O'Reilly Padraic, Jing Yun, Park Sung, Rimer Jeffrey D
Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204.
School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering and Low-Carbon Technology, The Co-Innovation Center of Chemistry and Chemical Engineering of Tianjin, Tianjin University, Tianjin 300072, China.
Proc Natl Acad Sci U S A. 2025 Jul 29;122(30):e2426814122. doi: 10.1073/pnas.2426814122. Epub 2025 Jul 21.
Understanding and exploiting material flexibility through phenomena such as the bending and twisting of molecular crystals has been a subject of increased interest owing to the number of applications that benefit from these properties, such as optoelectronics, mechanophotonics, soft robotics, and smart sensors. Here, we report the growth of spontaneously bent and twisted ammonium urate crystals induced by the keto-enol tautomerism of the urate molecule. The major tautomer is native to biogenic crystals, whereas the minor tautomer functions as an effective crystal growth modifier to induce naturally bent and twisted ammonium urate crystals. We show that the degree of curvature can be tailored based on the judicious selection of growth conditions. A combination of state-of-the-art microscopy and spectroscopy techniques are used to characterize the origin of bending. Spatially resolved nano-electron diffraction and high-resolution electron microscopy of naturally bent crystals show nearly single crystallinity with local lattice deformations generated by a combination of screw and edge dislocations. These observations are consistent with photoinduced force microscopy and contact resonance atomic force microscopy, which confirmed spatially resolved changes in the intermolecular interactions and the mechanical properties throughout the cross-sectional and axial regions of bent crystals. A mechanism of bending involving the generation of regionally specific dislocations is proposed as an alternative to more commonly reported models. These findings highlight a unique characteristic of tautomeric crystals that may have broader implications for other biogenic materials.
通过分子晶体的弯曲和扭曲等现象来理解和利用材料的柔韧性，由于众多应用受益于这些特性，如光电子学、机械光子学、软体机器人技术和智能传感器，已成为一个越来越受关注的主题。在此，我们报道了尿酸盐分子的酮 - 烯醇互变异构诱导自发弯曲和扭曲的尿酸铵晶体的生长。主要互变异构体是生物源晶体所固有的，而次要互变异构体作为一种有效的晶体生长改性剂，可诱导自然弯曲和扭曲的尿酸铵晶体。我们表明，可以基于对生长条件的明智选择来调整曲率程度。结合使用最先进的显微镜和光谱技术来表征弯曲的起源。对自然弯曲晶体的空间分辨纳米电子衍射和高分辨率电子显微镜显示，其具有近乎单晶性，且由螺旋位错和刃位错共同产生局部晶格变形。这些观察结果与光诱导力显微镜和接触共振原子力显微镜一致，后者证实了在弯曲晶体的横截面和轴向区域中分子间相互作用和机械性能的空间分辨变化。提出了一种涉及产生区域特异性位错的弯曲机制，作为对更常见报道模型的一种替代。这些发现突出了互变异构晶体的一个独特特性，这可能对其他生物源材料具有更广泛的意义。
