Molecular Hopper Crystals and Electron Beam-Triggered Reversible Actuation,Chemistry of Materials

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Molecular Hopper Crystals and Electron Beam-Triggered Reversible Actuation
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-09-15 , DOI: 10.1021/acs.chemmater.0c02892
N. Senthilnathan ₁ , T. P. Radhakrishnan ₁

Affiliation

Molecular crystals with unusual morphologies characteristic of “hopper crystals” have rarely been explored; such structures are potentially useful for eliciting specific responses to external fields or stimuli. Upon simple reprecipitation and controlled growth, select members of a family of strongly zwitterionic molecules, assembling in non-centrosymmetric lattices, are shown to form microcrystals with novel “hopper” morphology. The molecular aggregation is monitored by their characteristic fluorescence enhancement; X-ray diffraction, microscopy, and surface potential mapping provide insight into the development of the unique morphology. Under optimized conditions of electron beam irradiation in a scanning electron microscope, the prototype microcrystal is found to exhibit smooth, prominent, and reversible actuation. Even though electrically triggered macromolecular actuators as well as mechanically responsive and photo/thermosalient molecular crystals are known, controlled bending/folding induced by electron beams are rare and have been demonstrated only in specialized nanostructures. The current observations with a simple small-molecule-based hopper microcrystal are analyzed by a detailed examination of the crystal lattice structure and asymmetric dipole distribution, together with the simulations of the electron beam interactions. An empirical model developed for the responses in the local electrostatic field provides a mechanistic understanding of the actuation process.

中文翻译：

分子漏斗晶体和电子束触发可逆驱动

很少研究具有“漏斗晶体”特征的异常形态的分子晶体。这样的结构对于引起对外部场或刺激的特定反应可能是有用的。通过简单的再沉淀和受控的生长，显示出以非中心对称晶格组装的强两性离子分子家族的选定成员形成具有新颖“料斗”形态的微晶。分子聚集通过其特征性的荧光增强来监测。X射线衍射，显微镜和表面电势图谱可洞悉独特形态的发展。在扫描电子显微镜中优化的电子束辐照条件下，发现原型微晶显示出平滑，突出和可逆的驱动。即使已知电触发的大分子致动器以及机械响应的和光/热敏的分子晶体，但是由电子束引起的受控的弯曲/折叠是罕见的，并且仅在专门的纳米结构中得到了证明。通过对晶格结构和不对称偶极分布的详细检查，以及电子束相互作用的模拟，分析了基于简单小分子的料斗微晶的当前观察结果。针对局部静电场中的响应而开发的经验模型提供了对驱动过程的机械理解。由电子束引起的可控制的弯曲/折叠很少见，并且仅在专门的纳米结构中得到证明。通过对晶格结构和不对称偶极子分布的详细检查，以及对电子束相互作用的模拟，可以分析基于简单小分子的料斗微晶的当前观察结果。针对局部静电场中的响应而开发的经验模型提供了对驱动过程的机械理解。由电子束引起的可控制的弯曲/折叠很少见，并且仅在专门的纳米结构中得到证明。通过对晶格结构和不对称偶极子分布的详细检查，以及对电子束相互作用的模拟，可以分析基于简单小分子的料斗微晶的当前观察结果。针对局部静电场中的响应而开发的经验模型提供了对驱动过程的机械理解。

更新日期：2020-10-13

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