Non-Photochemical Laser-Induced Nucleation to Provide Crystallization-on-Demand and to Control Crystal Structure

该基金将用于开发非光化学激光诱导成核，作为提供按需成核、控制晶体结构和提高目前对溶液成核的理解的方法。这项技术的基础是几年前由PI发现的，即强近红外激光脉冲可以在有机小分子的老化过饱和溶液中诱导结晶。在迄今为止研究的情况下，激光诱导成核提高了成核率的10 - 13倍。更有趣的是甘氨酸水溶液的情况，它根据激光偏振状态（线性与圆形）结晶成两种不同的多晶型物，这意味着光电场是造成这种现象的原因。这种多晶型物的“偏振转换”代表了一种控制晶体结构的干净方法。假设光的振荡电场使溶质分子在预成核簇中排列，帮助其组织成特定的晶体结构。该方法也有可能创造一些物质的新的多晶型。新的多晶型物构成了可能具有重要工业应用的新型材料。在未来的三年里，PI建议通过系统地研究其对照明参数（如强度、波长、激光脉冲宽度和偏振状态）的依赖性，更好地理解非光化学激光诱导成核的机制。出于同样的目的，他们还将探索强静电场对过饱和溶液的影响。其他实验将集中在筛选大量的溶剂/溶质系统，以及熔体，以关联的诱导电场的形式的晶体结构，是诱导。这样的筛选还包括寻找新的多晶型。

This grant will be used to develop non-photochemical laser-induced nucleation as amethod for providing nucleation-on-demand, for controlling crystal structure, and forimproving the current understanding of nucleation from solution. The basis of thistechnique is the discovery, made by the PIs several years ago, that intense near-infraredlaser pulses could induce crystallization in aged supersaturated solutions of small organicmolecules. In cases studied so far, laser-induced nucleation enhances the rate ofnucleation by a factor of 10 13 . Even more intriguing is the case of aqueous glycine,which crystallizes into two different polymorphs depending on the laser polarization state(linear vs. circular), which implicates the optical electric field as being responsible for thephenomenon. This "polarization switching" of polymorphs represents a clean method forcontrolling crystal structure. It is hypothesized that the oscillating electric field of thelight is aligning solute molecules in a pre-nucleating cluster, aiding its organization into aparticular crystal structure. The method also has the potential of creating newpolymorphs of some substances. New polymorphs constitute novel materials that mayhave important industrial applications.Over the next three years the PIs propose to gain a better understanding of the mechanismof non-photochemical laser-induced nucleation, by systematically studying itsdependence on illumination parameters such as intensity, wavelength, laser pulse widthand polarization state. With the same goal, they will also explore the effect of a strongstatic electric field on supersaturated solutions. Other experiments would focus onscreening a large number of solvent/solute systems, as well as melts, to correlate the formof the inducing electric field to the crystal structure that is induced. Such screeningwould also include a search for new polymorphs.