UC Irvine

AgN-DNAs lie at the unique intersection of metal cluster science and DNA nanotechnology, combining the atomic precision of ligand-stabilized metal clusters with the sequence programmability of DNA nanomaterials. By varying the nucleobase composition, it is possible to fine-tune their composition and geometry, and thereby tune their photophysical properties. These capabilities make AgN-DNAs promising candidates as tunable emitters for applications in biological imaging, benefiting from their small molecular-like size, bright emission, low toxicity, and cost-effective synthesis. AgN-DNAs are known for their rod-like nanocluster geometries and nanosecond-lived fluorescence. One of the most exciting prospects for AgN-DNAs is their potential for emission in the second near-infrared (NIR-II) region, which is crucial for deep tissue imaging due to its ability to penetrate tissue for several centimeters. With the aim to fully realize the potential of AgN-DNAs for NIR-II imaging, it is essential to develop a deeper understanding of how their structure relates to their optical properties so that NIR-II-emitting AgN-DNAs can be effectively designed.Recent breakthroughs in AgN-DNA structure and composition revealed important correlations between nanocluster structure and photophysical behavior. These insights have been made possible by advances in mass spectrometry and crystallography of pure AgN-DNAs, in combination with high-throughput experiments and machine learning algorithms to design AgN- DNAs with targeted properties. This approach has been particularly useful given the challenges of growing AgN-DNA crystals that are suitable for diffraction studies and the complexity of determining precise molecular formulas via mass spectrometry, as traditional methods alone are insufficient for exploring the vast sequence space of DNA templates that could guide the creation of novel AgN-DNAs. This dissertation discusses groundbreaking discoveries in AgN-DNA structure, ligand composition and photophysical properties that have been enabled by high throughput synthesis and fluorimetry together with detailed analytical studies of purified AgN-DNAs. We unveil the first known AgN-DNAs that contain eight valence electrons and exhibit only microsecond-lived luminescence, making them the first reported DNA-stabilized luminescent quasi-spherical superatoms. Our discovery of a new class of chloride-stabilized AgN-DNAs enabled the first ab initio calculations of AgN-DNA electronic structure and introduced promising strategies to stabilize these emitters in biologically relevant conditions. Finally, we reported dual-emissive AgN-DNAs with fluorescence in the NIR-I spectral window and microsecond-lived photoluminescence in the NIR-II spectral window, opening the door to the tissue transparency window for effective fluorescence imaging in the NIR-II range.