Linear and Nonlinear Optical Response in Silver Nanoclusters: Insight from a Computational Investigation

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• 作者：Paul N. Day ; Ruth Pachter ; Kiet A. Nguyen ; Terry P. Bigioni
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：February 4, 2016
• 年：2016
• 卷：120
• 期：4
• 页码：507-518
• 全文大小：580K
• ISSN：1520-5215

文摘

We report a density functional theory (DFT) and time-dependent DFT (TDDFT) investigation of the thiolated silver nanoclusters [Ag₄₄(SR)₃₀]^4–, Ag₁₄(SR)₁₂(PR′₃)₈, Ag₃₁(SG)_19, Ag₃₂(SG)₁₉, and Ag₁₅(SG)₁₁, which were synthesized and for which one-photon absorption (OPA) characterization is available. Our computational investigation based on careful examination of the exchange-correlation functional used in DFT geometry optimization and for the linear optical properties predictions by TDDFT, demonstrated good agreement with the measured linear absorption spectra, however dependent on the applied functional. Following the benchmarking, we evaluated the two-photon absorption (TPA) response using TDDFT, noting that accurate prediction of OPA is important for suppositions on the spectral range for TPA enhancement because of the sensitivity to the excitation energies. Although the TPA cross-section results are complicated by resonance effects and quantifying TPA cross sections for these systems is difficult, our results indicate that the nanoclusters Ag₁₅ and Ag_31/32 are likely to have large TPA cross sections. The spherical symmetry of the Ag₄₄ and Ag₁₄ nanoclusters leads to applicability of superatom theory, while it is not as useful for the more oblate geometries of the Ag₁₅ and Ag_31/32 systems.