Collaborative Research: EAGER: Designing Nanomaterials to Reveal the Mechanism of Single Nanoparticle Photoemission Intermittency

合作研究：EAGER：设计纳米材料揭示单纳米粒子光电发射间歇性机制

• 批准号: 2345581
• 负责人: Preston Snee
• 金额: $ 19.54万
• 依托单位: University of Illinois at Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-01-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2345581&HistoricalAwards=false
• 关键词: Collaborative; Research; EAGER; Designing; Nanomaterials

In this collaborative EAGER project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Chemistry Division, Preston Snee of the University of Illinois at Chicago, Kristin Wustholz of the College of William and Mary, and Haw Yang of Princeton University seek to resolve the longstanding mystery of quantum dot blinking. Quantum dots are nanometer size semiconductor particles that have potential for applications in a variety of technologies, including energy-efficient displays, low-cost solar cells, and as biomedical research tools. Although these dots are fluorescent, single particles do not emit uniformly as they turn off and on randomly. This “blinking” phenomenon remains a challenge to explain, and this lack of a deep understanding limits the practical development and application of quantum-dot technology. The team of Snee, Wustholz and Yang combines expertise in chemical synthesis, advanced imaging, and statistical analysis, and is evaluating blinking behavior of various quantum-dot samples whose surface structures have been systematically varied using synthetic chemistry. The graduate and undergraduate researchers working on this project will gain a wide range of experience in experimental and computational chemistry. The collaborating research groups are also engaging in public outreach and the development of a free (online) physical chemistry textbook. The results of this NSF supported project are being incorporated into the textbook and outreach activities where appropriate.The quantum dot blinking phenomenon is generally described using power-law probability statistics to describe the emission "off" and "on" timescales; however, there is no straightforward physical explanation for this behavior. The central hypothesis of this EAGER proposal is that quantum-dot blinking is essentially the result of interactions of photo-generated excitons with the surface trap states, and that the emission probability distribution function reflects a distribution of trap barrier activation energies. The general functional form of this model is attributed to Albery (1985), who sought to explain electron transfer between semiconductor surfaces and adsorbed molecules. In contrast to the power-law function, the Albery model predicts a lognormal function. Furthermore, the Snee group recently demonstrated that quantum dots can exhibit lognormal blinking by manipulating the surface chemistry. Secondary hypotheses of this EAGER proposal are that 1) the apparent power-law dependence reported in the large body of existing experimental works is the result of uncontrolled surface chemistries and improper assumptions regarding how the photon counts should be "binned" in time, and 2) the defect sites interact with molecular oxygen, and that this interaction results in behavior that is a discrete sum of lognormal distributions that appear nearly identical to a power-law distribution. These hypotheses are being examined through combined quantum-dot synthesis, single particle imaging, and photon counting experiments. The analysis of blinking statistics utilizes maximum likelihood estimation, which addresses previous problems with arbitrary binning of blinking data that can lead to erroneous conclusions.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.

在这个由大分子，超分子和纳米化学计划的合作急切项目中，伊利诺伊大学芝加哥大学的普雷斯顿·斯尼（Preston Snee），威廉和玛丽学院的克里斯汀·沃斯索尔斯（Kristin Wustholz），普林斯顿大学的霍恩·杨（Haw Yang of PrinceTon）寻求解决悠久的量子神秘之谜。量子点是纳米尺寸的半导体颗粒，尽管这些点是荧光的，但具有在多样性中应用的潜力，单个颗粒在关闭和随机关闭时不会均匀地发射。这种“眨眼”现象仍然是解释的挑战，缺乏深刻的理解限制了量子点技术的实际发展和应用。 SNEE，Wustholz和Yang团队结合了化学合成，高级成像和统计分析方面的专业知识，并正在评估各种量子点样品的闪烁行为，其表面结构使用合成化学系统地在系统上变化。从事该项目的研究生和本科研究人员将在实验和计算化学方面获得广泛的经验。合作的研究小组还从事公共宣传和免费（在线）物理化学教科书的发展。该NSF支持的项目的结果已被纳入教科书和外展活动中。通常使用幂律概率统计数据来描述量子点闪烁现象，以描述排放“ OFF”和“ ON”时标。但是，对于这种行为没有直接的物理解释。该急切建议的中心假设是，量子点闪烁本质上是光产生的激子与表面陷阱状态的相互作用的结果，并且发射概率分布函数反映了陷阱屏障激活能的分布。该模型的一般功能形式归因于Albery（1985），他试图解释半导体表面和吸附分子之间的电子转移。与幂律函数相反，Albery模型预测了对数正态函数。此外，SNEE组最近证明量子点可以通过操纵表面化学来表现出对数正态的眨眼。 Secondary hypotheses of this EAGER proposal are that 1) the apparent power-law dependence reported in the large body of existing experimental works is the result of uncontrolled surface chemistries and improper assumptions regarding how the photon counts should be "binned" in time, and 2) the defect sites interact with molecular oxygen, and that this interaction results in behavior that is a discrete sum of lognormal distributions that appear almost identical to a power-law 分配。这些假设正在通过量子点合成，单个粒子成像和光子计数实验进行检查。闪烁统计数据的分析利用了最大的似然估计，该估计解决了可能导致结论错误的闪烁数据的任意构造的先前问题。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响审查标准来通过评估来诚实地认为通过评估来诚实地支持。