Plasmon Resonance of Isolated Gold Hollow Nanoparticles and Nanoparticle Pairs: Insights from Electronic Structure Calculations
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- 作者：Huili Ma ; Fang Gao ; WanZhen Liang
- 刊名：The Journal of Physical Chemistry C
- 出版年：2012
- 出版时间：January 19, 2012
- 年：2012
- 卷：116
- 期：2
- 页码：1755-1763
- 全文大小：614K
- 年卷期：v.116,no.2(January 19, 2012)
- ISSN：1932-7455
文摘
Because the feature sizes of noble metal nanoparticles (NPs) are smaller than a few of nanometers, simulations including quantum effects and atomistic details are inevitable. In this work, we report a detailed electronic structure study on the plasmon resonance of isolated gold hollow nanoparticles (NPs) and NP pairs. The long-range-corrected (LRC) density functional theory (DFT) has been employed. We find that the plasmon resonance of small-size gold NPs is very sensitive to NP sizes and interparticle distances. When the NP鈥檚 size changes from Au32 to Au17鈥?/sup>, the high-energy absorption maximum blue shifts 50 nm and when the interparticle distance of Au17鈥?/sup> NP pairs changes from 1.15 to 0.83 nm, the corresponding blue shift is 40 nm. The spectral line width becomes narrower as the NP size increases and the interparticle distance reduces. The insight of how the plasmon-resonance peaks of a NP pair are formed and how they are sensitive to the interparticle separation is revealed by the plots of transition densities and frontier molecular orbitals (MOs) as a function of the interparticle distances. As the two NPs approach near touching contact, they are strongly coupled and a bond-forming step takes place, which is verified by the significant overlap between the unoccupied MOs. The strong coupling between the wave functions results in the electrons to redistribute. As a result, we observe that a large number of electrons are localized in the gap and the nearest neighboring atoms of a closely spaced NP pair. The localized electrons enhance the electromagnetic field in the gap of the NP pair, leading to a pronounced red shift and increasing polarizability for the plasmon-resonance peaks, and many new absorption peaks appeared in low-energy range.