Title: Quantum Confined Stark Effect in Au-8 and Au-25 Nanoclusters
Authors: Wen, Xiaoming
Yu, Pyng
Toh, Yon-Rui
Tang, Jau
Department of Photonics
Issue Date: 21-Feb-2013
Abstract: The quantum confined Stark effect is investigated for the first time in bovine serum albumin (BSA) protected Au-8 and Au-25 nanoclusters. We observed a red-shift of 63 meV in Au-8 nanoclusters upon an increase in pH from 2.14 to 12.0. Such behavior could be well explained in terms of the presence of a linear polar component and a quadratic polarizable component. In contrast, Au-25 nanoclusters exhibit more complicated Stark shifts due to their specific core/semiring structure. A plateau of the Stark shift was observed in both absorption and fluorescence, showing an offset of 30 meV. The lifetime measurements confirm that the plateau is due to the screening effect of the semirings in Au-25@BSA. Moreover, the dual fluorescent bands of Au-25 nanoclusters exhibit two different Stark shifts of 79 and 52 meV, respectively. The experimental data indicate that the Stark shift in both Au-8@BSA and Au-25@BSA has a significant linear polar component due to their asymmetric structure. This study suggests that gold nanoclusters can become a potentially useful candidate in probing local electric fields and also in pH-sensing in nanoscale environment of biological systems.
URI: http://dx.doi.org/10.1021/jp3116676
ISSN: 1932-7447
DOI: 10.1021/jp3116676
Volume: 117
Issue: 7
Begin Page: 3621
End Page: 3626
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