GOALI: Chiroptical Anisotropy

目标：手性光学各向异性

• 批准号: 1105000
• 负责人: Bart Kahr
• 金额: $ 49万
• 依托单位: New York University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1105000&HistoricalAwards=false
• 关键词: GOALI; Chiroptical; Anisotropy

TECHNICALThe two-century struggle to measure chiroptical properties of organized, anisotropic media leaves an enormous hole in the science of molecular and materials chirality. What little has been learned during the past three decades has come haltingly. In order to unravel averaged, pseudo-scalar solution chiroptical effects into quantities that can be compared with electronic structures of real molecules, a database of molecular crystal tensors is required. They must be measured using a methodology that is robust, can be easily adopted, and can generate the quantity of data that enables comparison, analysis, and understanding. Mueller matrix imaging polarimetry is the solution because all linear optical properties can be determined simultaneously, it can assay depolarization in imperfect samples, and is suited to the treatment of non-normal incidence analytically. A fast device without moving optical components will require the synchronous operation of four photoelastic modulators. This has never been achieved but will be carried out with Hinds Instruments of Hillsboro, Oregon, a leading developer of photoelastic modulators and polarimeters, through collaboration of postdoctoral researchers in Oregon and New York. The need for a commercial, turnkey polarimeter for oriented materials is essential because chiroptical anisotropy is a chasm too large for one group to bridge. With this device, the optical rotation of isomorphous molecular crystals that lend themselves to the interpretation of small structural perturbations will be measured. To avoid complications associated with excitonic interactions in resonance, the anisotropy of circular dichroism of "oriented gases" of dyes in host crystals will be studied. Mueller matrix microscopes and polarimeters are also applicable to meso-structured materials such as cholesteric liquid crystals and chiral sculpted meta-materials. NON TECHNICALExactly two hundred years ago (1811) François Arago first observed the rotation of the plane of light polarization passing through a crystal of quartz along the direction of highest symmetry. It is been said that no phenomenon "has had so profound an effect on chemical thought as that of natural optical rotatory power" (Liehr, 1954. Unfortunately, since that time it has been almost impossible to measure optical rotation in organized media like crystals along general directions because the electromagnetic field of light suffers greater perturbations in low-symmetry environments that mask the phenomenon of interest. Thus, we remain ignorant about the orientation dependence of optical rotation in molecules, a fundamental light-matter interaction. Our project is aimed at developing an instrument for measuring the polarization state of light in any medium quickly and accurately enough so that we can derive the essential quantities. The device is based on photoelastic modulators that can change the polarization state of light at a rate of ~50,000 times per second. Using four such modulators, built by our GOALI partner, Hinds instruments, we can generate a complex signal that can be treated by the mathematical techniques of one of Arago's colleagues', Fourier. We have established a relationship with the Bronx Academy of Science and Technology, an underserved public high school with 98% native Spanish speakers. We provide, in addition to research opportunities in our lab during the summer and academic year, SAT tutoring, an advantage commonly exercised in wealthy school districts. We are convinced that creating scientists, especially those from underrepresented groups, requires first developing within students, one-by-one, scientific identities, and ensuring that the basics are attended.

技术两个世纪以来，测量有组织的各向异性介质的手性特性的斗争在分子和材料手性科学中留下了一个巨大的漏洞。在过去30年里，人们几乎没有学到的东西，现在来得有些停顿。为了将平均的伪标量溶液手势效应分解成可以与真实分子的电子结构相比较的量，分子晶体张量的数据库是必需的。必须使用健壮的、易于采用的、能够生成能够进行比较、分析和理解的数据量的方法来衡量它们。米勒矩阵成像偏振法是一种解决方案，因为它可以同时测定所有的线性光学性质，它可以测量不理想样品的退偏振，并且适合于非正入射的解析处理。一个没有移动光学元件的快速器件将需要四个光弹调制器同步工作。这一目标从未实现过，但将通过俄勒冈州和纽约的博士后研究人员的合作，与俄勒冈州希尔斯伯勒的Hinds Instruments进行合作，Hinds Instruments是光弹性调制器和偏振仪的领先开发商。由于手性各向异性是一个太大的鸿沟，一组人无法弥合，因此需要一种用于定向材料的商用、交钥匙偏振仪是必不可少的。利用这个装置，将测量有助于解释微小结构扰动的同构分子晶体的旋光。为了避免与激子共振相互作用有关的复杂问题，我们将研究染料在主体晶体中“定向气体”的圆二向色性的各向异性。米勒矩阵显微镜和偏振仪也适用于介观结构材料，如胆甾型液晶和手性雕刻超材料。早在两百年前(1811年)，弗朗索瓦·阿拉戈首次观测到通过石英晶体的光偏振面沿最高对称性方向的旋转。有人说，没有任何现象“对化学思维的影响像天然的光学旋转力那样深刻”(Liehr，1954)。不幸的是，从那时起，几乎不可能测量像晶体这样的有序介质中沿一般方向的旋光，因为光的电磁场在低对称性环境中遭受更大的扰动，从而掩盖了感兴趣的现象。因此，我们仍然忽略了分子中旋光的方位依赖性，这是一种基本的光-物质相互作用。我们的项目旨在开发一种足够快速和准确地测量任何介质中光的偏振态的仪器，以便我们能够推导出必要的量。该装置基于光弹调制器，可以每秒~5万次的速度改变光的偏振状态。使用我们的目标合作伙伴Hinds仪器公司制造的四个这样的调制器，我们可以产生一个复杂的信号，可以用Arago的一位同事傅立叶的数学技术来处理。我们已经与布朗克斯科学与技术学院建立了合作关系，这是一所服务不足的公立高中，98%的人以西班牙语为母语。除了暑假和学年期间在我们实验室的研究机会外，我们还提供SAT辅导，这是富裕学区常见的优势。我们坚信，培养科学家，特别是那些来自代表性不足的群体的科学家，需要首先在学生中一个接一个地培养科学认同感，并确保基本的课程都能参加。