NSF Award
2419539
Nontechnical Description<br/><br/>Near-infrared light lies beyond the limits of the human eye but is valuable for applications in medicine, telecommunications, and optical computing. Near IR luminescence is especially valuable for medical imaging as longer wavelengths of light penetrate deeper into biological tissues. However, few materials emit light in the near IR with wavelengths between 1 and 1.7 microns. This project explores ultrasmall gold nanoparticles, roughly a nm in diameter and with merely dozens of gold atoms each. Their desirable properties include high stability, biocompatibility, and near IR luminescence. The luminescence of these nanoparticles is very sensitive to the number of constituent atoms, requiring atomically precise control. By precisely controlling the number of atoms per particle, one can tailor the wavelength of emitted near-infrared light. This project aims to achieve high brightness and wavelength tuning of near-IR luminescence from atomically precise, quantum-sized gold nanoparticles though a combination of new synthesis methods and comprehensive optical characterization. The project will provide training opportunities for students to prepare them for future technical careers. The PI will actively work to broaden participation in STEM through outreach and broaden exposure of the research through conference presentations and a focused symposium on the topic of luminescent nanoclusters.<br/><br/>Technical Description<br/><br/>A myriad of new phenomena emerge in quantum-sized gold nanoparticles. These include quantized energy levels, single-electron transitions, and near-IR luminescence (700 – 1700 nm). However, the current quantum yields of luminescence from gold nanoclusters are still less than 5% and tuning of wavelength to longer wavelengths remains challenging. The vast majority of luminescent gold nanoclusters are still imprecise at the atomic level, and their structures are unknown, which precludes precise structure-property correlations. To tackle these challenges, this project aims to develop an atomically precise approach for gold nanoclusters and further devise effective strategies to enhance their near-infrared luminescence. By combing atomically precise synthesis of gold nanoclusters and spectroscopic analyses, the fundamental mechanism is to be mapped out. This will form the basis for devising strategies for the suppression of non-radiative pathways, thereby enhancing the efficiency of luminescence. Structural control of gold nanoclusters with atomic precision also allows for extending the luminescence wavelength into the second near-infrared window (>1 micron). The project aims to achieve definitive relationship between the atomic-level structure and the optical properties of gold nanoclusters, which could become a paradigm for the studies of other types of electronic and optical materials. The fundamental knowledge on manipulating the electronic excited states in metal nanoclusters may broadly benefit quantum science and technology.<br/><br/>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.
