Mid-infrared Intraband and Localized Surface Plasmon Resonance Spectroscopies of Doped Semiconductor Nanocrystals

化学系的大分子、超分子和纳米化学计划支持圣母大学的Masaru Kuro教授和他的研究小组研究半导体纳米晶体的光学性质。分子和半导体纳米晶体与光发生反应，显示出独特的“指纹”，可用于识别它们。库诺教授的研究有助于开发新的分析检测技术，用于监测对健康、安全和国家安全至关重要的微量化学和生物物质。了解半导体纳米晶体的基本光学性质，对于开发低成本的手机红外摄像头和可以在室温下工作的红外探测器也有意义。库诺教授和他的团队开展了亲身实践的推广活动，如热成像套件，以吸引较低收入的学生和南本德社区学校系统的少数族裔学生在STEM职业生涯中感兴趣。纳米晶体(NC)合成的最新进展使稳定的、具有显著掺杂密度的自掺杂半导体NCS的发展成为可能。这些NC表现出中红外带内和局域表面等离子体共振(LSPR)。然而，对于它们对纳米管尺寸、形状、表面化学和掺杂密度/掺杂活化度的依赖关系却知之甚少。这是由于掺杂的NC系综中存在的不均匀，这在目前的胶体NC合成中是不可避免的。对单个NC进行高灵敏度、中红外光学测量的手段有限。在化学系大分子、超分子和纳米化学项目的支持下，库诺教授的研究团队解决了这一领域的重要需求。该研究小组采用了一种新开发的超分辨率红外吸收技术，称为红外光热外差成像(IR-PHI)，来测量自掺杂NCS的局部吸收。这些测量反过来可以更好地了解这些半导体NC的基本性质，以及在高掺杂密度下带内跃迁演变为集体LSPR的过程。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry supports Professor Masaru Kuno and his research group at the University of Notre Dame to study the optical properties of semiconductor nanocrystals. Molecules and semiconductor nanocrystals react with light to exhibit unique "fingerprints" that can be used in their identification. Professor Kuno's research contributes to the development of new analytical detection technologies for monitoring trace amounts of chemical and biological substances that are important to health, safety, and national security. Understanding fundamental optical properties of semiconductor nanocrystals also has implications in the development of low cost infrared cameras in cellphones and infrared detectors that can operate at room temperature. Professor Kuno and his group develop hands-on outreach activities such as thermal imaging kits to bring interest lower income and minority students in the South Bend Community School system in STEM careers. Recent advances in nanocrystal (NC) synthesis have enabled the development of stable, self-doped semiconductor NCs with significant doping densities. These NCs exhibit mid-infrared intrabands and localized surface plasmon resonances (LSPRs). However, little is understood about their dependence on the NC size, shape, surface chemistry, and doping density/dopant activation. This is due to the inhomogeneities present in doped NC ensembles, which is unavoidable in current colloidal NC syntheses. Limited means exist for conducting highly sensitive, mid-infrared optical measurements of single NCs. With this support from the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division, Professor Kuno’s research team addresses this important need in the field. The research team employs a newly developed, super-resolution infrared absorption technique, called infrared photothermal heterodyne imaging (IR-PHI), to measure the local absorption of self-doped NCs. These measurements, in turn, can enable better understanding of the fundamental properties of these semiconductor NCs and of the evolution of intraband transitions into collective LSPRs at high doping densities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.