根據分子和鈉環團簇的交互作用應用密度泛函理論研究表面增強拉曼光譜的機制

DFT and TDDFT study on surface enhanced Raman spectra mechanism in terms of the interaction between molecules and Na clusters

劉丞祐(Cheng-You Liu)

指導教授 ： 郭光宇 ； 林倫年

國立臺灣大學/理學院/物理研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02537

摘要

密度泛函理論(Density functional theory)已經被廣泛用來計算原子分子系統的能態。但是密度泛涵理論的架構主要針對關於基態的系統的研究，對於激發態的研究，含時密度泛涵理論是更為適合。隨著含時密度泛涵理論(Time dependent density functional theory-TDDFT)的進步，這個工作將以TDDFT量子力學模擬為基礎，對於環狀團簇系統的激發態特性有更深的了解。為了能夠更多元的來看系統的特性，將透過使用不同的軟體，包括Gaussion09(linear response-線性響應套件)、Octopus( time propagation-時間傳播套件)，利用每一種軟體長處來研究不同的物理性質。
而近年來表面增強拉曼光譜(surface enhanced Raman spetroscopy)因為儀器和技術的成熟而快速發展，要考慮到光、分子和奈米結構的交互作用，所以需要三者的整合才能提出對SERS的系統做出完整的解釋，所以理論的發展將是未來的重點。
本研究利用含時密度泛涵理論來探討關於單一電子系統的電漿子激發態。會以鈉原子環中的區域表面電漿共振為出發點，以真實時間和真實空間(real time real space)的含時密度泛函理論套件Octopus計算吸收光譜，比較鈉原子環和鈉原子鏈在受到電場干擾時所反應的電漿共振態。並且比較當原子數增加時，吸收光譜的改變和電漿子之間的關係。接著會使用線性響應套件Gaussian來計算吡嗪(pyrazine)吸附在鈉原子環上的表面拉曼增強光譜，並以吸收光譜作為觀點來討論。

關鍵字

密度泛函理論 ； 含時密度泛涵理論 ； 環狀團簇系統 ； 表面增強拉曼光譜 ； 電漿子激發態

並列摘要

Density functional theory (DFT) has been widely utilized to calculate the energy state of atomic and molecular systems. However, DFT’s theoretical framework focuses primarily on the research on the ground state of the systems, so for excited state research, time-dependent density functional theory will be more suitable. Along with the development of the TDDFT, this study will build up on quantum mechanics simulation to gain a deeper understanding of the excited state of the ring-cluster system. To make an in-depth analysis of the property of this system, different software including Gaussion09 (linear response package) and Octopus (time propagation package) were used to look into the different physical properties.
In recent decades, the surface enhanced raman spectroscopy(SERS) developed rapidly due to advancements in devices and technique. However, considering the interaction of light, molecules, and nanostructures, all three of the factors must be accounted for in order to achieve a complete analysis of the SERS system. Thus, theoretical development of SERS will be a key factor in the future.
This research utilizes TDDFT to study the plasmon excited state of single electron system. Based on the localized surface plasmon resonance (LSPR) of sodium ring, the Octopus software (real time and real space) was used to calculate absorption spectrum. The plasmon resonance of sodium ring and sodium chain under electric field was also compared. On the other hand, the absorption spectrum difference and relationship with the plasmon were also compared when the atom number was increased. Finally, using linear response package Gaussian, the SERS of pyrazine attached to the sodium ring was calculated, and further discussion was made with a view of absorption spectrum.

並列關鍵字

DFT ； TDDFT ； ring-cluster system ； SERS ； plasmon excited state

參考文獻

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