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Luminescence and Electron Dynamics in Atomically Precise Nanoclusters with Eight Superatomic Electrons.
K L Dimuthu M Weerawardene1, Pratima Pandeya1, Meng Zhou2
1Department of Chemistry , Kansas State University , Manhattan , Kansas 66506 , United States.
Journal of the American Chemical Society
|November 5, 2019
Summary
Gold nanoclusters with similar cores, [Au25(SR)18]- and [Au13(dppe)5Cl2]3+, show distinct emission properties. This study reveals differences in their photodynamics and excited-state lifetimes using experimental and theoretical methods.
Area of Science:
- Materials Science
- Nanotechnology
- Physical Chemistry
Background:
- Gold nanoclusters ([Au25(SR)18]- and [Au13(dppe)5Cl2]3+) share a 13-atom icosahedral core and an 8-electron superatomic configuration.
- Despite structural similarities, significant differences exist in their photoluminescence and time-resolved electron dynamics.
- Understanding these differences is crucial for designing nanoclusters with tailored optical properties.
Purpose of the Study:
- To elucidate the similarities and differences in the emission properties of [Au25(SR)18]- and [Au13(dppe)5Cl2]3+ nanoclusters.
- To theoretically investigate the photodynamic properties of [Au13(dppe)5Cl2]3+ for the first time.
- To correlate observed emission behaviors with electronic structure and decay pathways.
Main Methods:
- Experimental measurements of photoluminescence and photoluminescence decay.
- Time-resolved transient absorption spectroscopy.
- Time-dependent density functional theory (TD-DFT) calculations for radiative and nonradiative decay properties and lifetimes.
Main Results:
- [Au13(dppe)5Cl2]3+ exhibits a single strong emission peak, unlike the weaker bimodal luminescence of [Au25(SR)18]-.
- The strongly emissive state in both nanoclusters arises from S1 deexcitation, with microsecond lifetimes.
- Higher excited states in [Au13(dppe)5Cl2]3+ have shorter lifetimes (<1 ps) compared to [Au25(SR)18]- due to a smaller energy gap between unoccupied orbitals.
Conclusions:
- The electronic structure, specifically the energy gap between degenerate unoccupied orbitals, dictates the excited-state dynamics and emission characteristics of these gold nanoclusters.
- TD-DFT calculations effectively complement experimental data in understanding photophysical processes.
- This study provides fundamental insights into structure-property relationships in gold nanoclusters, guiding future material design.
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