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128th General Meeting of Korean Chemical Society Size-Dependent Light Harvesting from Nonthermalized Excited States of Gold Clusters

Submission Date :
9 / 8 / 2021 , 09 : 36 : 41
Abstract Number :
128090847036
Presenting Type:
Symposium
Presenting Area :
KCS - [International Symposium for Emerging Investigators] Light-Matter Interaction and Electron Transfer: State of the Art and Remaining Challenges
Authors :
SangMyeong Han, Hongmei Xu, Dongil Lee*
Department of Chemistry, Yonsei University, Korea
Assigned Code :
KCS3-13 Assigend Code Guideline
Presenting Time :
WED, 16 : 55
Light harvesting is central to many photonic materials. The light harvesting efficiency in these materials is, however, generally reduced because upper excited-state energy is lost by energy-dissipating internal conversion (IC) and vibrational relaxation processes. Atomically precise gold clusters have emerged as a new class of materials because of their unique bulk-to-molecule transition characters, where discrete electronic states emerge and electronic band energetics lead to quantum confinement effects. Recently, the presence of relatively slow IC processes in the subpicosecond-to-picosecond range has been generally observed in molecule-like gold clusters. Herein, by conjugating energy acceptor aminofluorescein (AF) to the gold nanoclusters, new energy harvesting methodology via energy transfer from the nonthermalized state of gold nanoclusters, which was achieved by relatively slow IC process is demonstrated.
Steady-state photoluminescence measurements of AF-conjugated Au18, Au22, and Au25 clusters show notable AF emission upon high-energy excitation of gold clusters. Femtosecond transient absorption measurements reveal that the IC processes of Au18, Au22, and Au25 are relatively slow whereas IC processes of larger clusters overwhelm the energy transfer rate. Energy gap and spectral overlap have been considered to another descriptor for efficient nonthermalized energy transfer. Herein, a new avenue for energy harvesting from nonthermalized upper excited states of gold clusters, which would otherwise be lost as heat, is opened up.