Clear mechanistic insights into excited state dynamics in thiolate-protected gold nanoclusters are vital for understanding the origin of the photocatalytic enhancement via metal nanoparticles in the visible region. Even though extensive experimental studies have been performed on the nonradiative relaxation dynamics of the anionic [Au25(SR)18]-1 thiolate-protected gold nanocluster, the neutral and the cationic clusters have been studied less thoroughly. The experimental findings suggest that the electronic and optical properties are highly sensitive to the structure and charge state of the Au25(SR)18 cluster. Therefore, in this work, the nonradiative excited state relaxations of the neutral and cationic [Au25(SH)18]q [q = 0, +1] clusters are investigated theoretically to characterize the electron relaxation dynamics. The core and higher excited states lying in the energy range 0.0 – 2.2 eV are investigated using time-dependent density functional theory (TD-DFT). The quantum dynamics of these states are studied using a decoherence-corrected fewest switches surface hopping method in a real-time Kohn-Sham approach to DFT (FSSH-TDKS). The population transfers of the core states and higher excited states are compared between the neutral, cationic and anionic clusters. The calculated decay time constants for neutral and cationic are compared with the anionic cluster to qualitatively understand the differences and similarities in the electron-nuclear dynamics in the clusters when the charge is varied. The spectral densities are also calculated to understand the electron-phonon interactions that lead to electronic relaxations.

Theoretical investigation of electron-nuclear dynamics in the neutral and cationic [Au25(SH)18]q [q = 0, +1] thiolate-protected gold nanoclusters

253rd National Meeting (2017)

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