【摘要】：基于密度泛函理論計算和拉曼光譜理論分析,我們研究了對巰基吡啶(4MPY)分子的拉曼光譜和其在銀上的表面增強拉曼光譜(SERS),并進一步探討了SERS與界面吸附結(jié)構(gòu)、異構(gòu)化、質(zhì)子化和氫鍵作用以及低能激發(fā)態(tài)的關(guān)系。首先,我們對兩種分子異構(gòu)體的相對穩(wěn)定性和拉曼光譜進行了理論分析。在此基礎(chǔ)上,進而研究了該分子與不同銀簇作用時的拉曼光譜,結(jié)果表明,4MPY以巰基硫與銀簇作用形成強的Ag S鍵,導致拉曼光譜的線型不依賴于所選銀簇的大小。接著我們考慮了吡啶氮端作用的兩種情況。(1)當4MPY-銀簇復合物同時以吡啶氮與水簇或水合質(zhì)子簇形成氫鍵時,結(jié)果表明吡啶環(huán)的部分振動頻率隨氫鍵和質(zhì)子化發(fā)生藍移。(2)當考慮吡啶氮與銀簇作用時,吡啶環(huán)三角畸變振動發(fā)生藍移。上述情況不僅解釋了實驗觀測的振動頻率變化,而且表明了化學環(huán)境改變對相對拉曼強度的影響。最后,我們計算了當對巰基吡啶分子以單端或雙端與銀簇作用,在考慮激發(fā)光與低能激發(fā)態(tài)的能量匹配時,拉曼光譜強度與低能激發(fā)態(tài)的關(guān)系。計算結(jié)果表明,在雙端吸附構(gòu)型下,與吡啶氮成鍵的銀簇受激發(fā)產(chǎn)生電荷轉(zhuǎn)移態(tài),不僅導致吡啶環(huán)v_(12)、v_1和v_(8a)振動的拉曼信號增強,而且選擇性地增強吡啶環(huán)C H面內(nèi)對稱彎曲振動v9a的拉曼信號。
[Abstract]:Based on density functional theory (DFT) calculation and Raman spectrum analysis, we studied the Raman spectra of 4-mercaptopyridine (4MPY) molecules and their surface-enhanced Raman spectra (SERS) on silver, and further discussed the adsorption structure and isomerization of SERS with the interface. The relationship between protonation and hydrogen bonding and low energy excited states. Firstly, the relative stability and Raman spectra of the two isomers are theoretically analyzed. On this basis, the Raman spectra of the molecule interacting with different silver clusters have been studied. The results show that 4MPY formed a strong Ag / S bond by mercaptosulfur and silver clusters, leading to the linear type of Raman spectra independent of the size of the selected silver clusters. Then we consider two cases of nitrogen terminal interaction of pyridine. (1) when 4MPY- silver cluster complex forms hydrogen bond with water cluster or hydrated proton cluster with pyridine nitrogen at the same time, The results show that the partial vibration frequency of pyridine ring is blue shifted with hydrogen bond and protonation. (2) when the interaction of pyridine nitrogen with silver cluster is considered, the triangular distortion vibration of pyridine ring is blue shifted. The above results not only explain the vibration frequency change observed in the experiment, but also indicate the influence of the chemical environment change on the relative Raman intensity. Finally, we calculate the relationship between Raman spectrum intensity and low energy excited states when we consider the energy matching between excited light and low energy excited states when the mercaptopyridine molecules interact with silver clusters at one or two ends. The calculated results show that the charge transfer states of the silver clusters bonded to pyridine nitrogen are generated under the two-terminal adsorption configuration, which not only leads to the enhancement of Raman signals of the virion vibration of the pyridine ring v _ (12) / v _ (1) and v _ (8a). Moreover, the Raman signal of symmetric bending vibration v9a in the plane of pyridine ring C ~ (2 +) H is selectively enhanced.
【作者單位】： 廈門大學化學化工學院化學系 固體表面國家重點實驗室 能源材料化學協(xié)同創(chuàng)新中心;
【基金】：國家自然科學基金(21273182,21533006,21373172)資助項目~~
【分類號】：O641.1

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