Atomically Precise Nanoparticles

Atomically Precise Nanoparticles

January 21, 2020

Address

797 E. Tyler St.
Tempe, AZ 85281

Location

Biodesign Institute, CL1-21

Date and Time

February 7, 2020, 10:30 am (Length: 1 hour 0 minutes)

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Thalappil Pradeep, PhD, Institute Professor, Indian Institute of Technology Madras

Recent research has revealed many nanoparticles whose properties depend on the number and spatial arrangement of their constituent atoms. This distinct atom-dependence of properties is particularly noticeable in ligand protected, atomically precise clusters of noble metals. They behave like molecules and show unusual properties such as luminescence in the visible and near-infrared regions. Their molecule-like behavior is elegantly shown by atom and structure conserving chemical reactions between them. Several archetypal nanoparticle clusters, Ag25(SR)18 and Au25(SR)18 (-SR = alkyl/aryl thiolate), have been used for such reactions. Despite their geometric robustness and electronic stability, reactions between them in solution at room temperature produce alloys AgmAun(SR)18 (m+n = 25), keeping their M25(SR)18 composition, structure and topology intact. We captured one of the earliest events of the process, the formation of the dianionic adduct [Ag25Au25(SR)36]2-, by electrospray ionization mass spectrometry. Molecular docking simulations and density functional theory (DFT) calculations also suggest that metal atom exchanges could occur through adduct formation. Such isomorphous transformations between nanoparticles imply that microscopic pieces of matter can be transformed to chemically different entities, preserving their structures in the nanometric regime. Intercluster interactions can also produce cluster dimers and unusual, well-defined alloys that reflect the shell structure of certain reactants. Atom exchanges suggest interesting dynamics in solution. Early results of these investigations will be presented. New experiments confirm the chemical diversity possible in such systems and exhibit properties useful for potential applications.

Hosted by Biodesign Center for Molecular Design and Biomimetics.