以拉曼光譜探討光化學反應

Probing Photochemical Reactions by Raman Spectroscopy

陳緗翎(Hsiang-Ling Chen)

指導教授 ： 李世琛

中原大學/理學院/化學研究所/碩士(2017年)

https://doi.org/10.6840/cycu201700128

摘要

本研究主要以光譜分析技術探討拉曼基材與量測分子在光化學反應下的表面增強拉曼散射(SERS)變化。研究分為兩部份：第一部份利用奈米氧化銀在可見光照射下還原為銀粒子的光敏感性，實驗使用兩種不同晶體形狀奈米氧化銀並以甲烯基藍(MB)作為銀的偵測分子，當照光時間增加，MB的表面增強拉曼散射效應也因此提高。藉一級反應動力學公式計算光化學過程中銀生成的kobs速率常數值並得到八面體氧化銀的kobs小於正立方體氧化銀的kobs。當MB濃度減小，MB分子多平行吸附氧化銀晶體上，當MB濃度增大，MB分子多垂直吸附氧化銀晶體上；第二部份以奈米金的表面電漿子共振(SPR)特性，使用與奈米金吸收波長相近的532 nm雷射激發，透過不同濃度奈米金粒子的表面電漿子催化不同濃度對-胺基苯硫酚(4-ATP)進行耦合反應(coupling reactions)，化學轉換形成具有偶氮鍵–N=N–的4,4'-二巰基偶氮苯(DMAB)，隨著雷射照光時間增加，DMAB的SERS訊號越彰顯，故可以得到反應過程中偶氮鍵生成的速率常數值k。實驗也利用Michaelis-Menten動力學方程式作出的Lineweaver-Burk獲得最大速率(Vmax)及催化劑-分子親和力(Km)，在奈米金濃度較高情況下，Vmax與Km隨照光時間越久而越大，充分生成DMAB需要較長時間，而奈米金濃度較低的狀況下，Vmax與Km隨照光時間越小，反應中形成較多nano Au-4-ATP複合物。

關鍵字

拉曼光譜；光化學反應；氧化銀；對-胺基苯硫酚

並列摘要

This study primarily used spectral analysis techniques to investigate surface-enhanced Raman scattering (SERS) changes during photochemical reactions of Raman substrates and detection molecules. The study is divided into two parts. The first part utilizes the photosensitivity of silver oxide nanoparticles which reduces the nanoparticles to metallic silver upon their illumination with visible light. Two types of silver oxide nanoparticles with different crystal shapes were used in this experiment and methylene blue (MB) was used as a molecule detector for metallic silver, so that as the illumination time increases, the SERS effect of MB will also increase due to its interaction with metallic silver. The metallic silver formation rate constant (kobs) during the photochemical reaction was calculated using first-order kinetic equations, the kobs of octahedral silver oxide becomes smaller than that of cubic silver oxide. At lower MB concentrations, as the MB molecules mainly adsorb in a parallel fashion onto the silver oxide crystals. At higher MB concentrations, as the MB particles mainly adsorb perpendicularly onto the silver oxide crystals. The second part of this study utilizes the surface plasmon resonance (SPR) of gold nanoparticles via 532 nm laser excitation, which is close to the absorption wavelength of gold nanoparticles. The SPR of gold nanoparticles in varying concentrations is then used to catalyze the coupling reactions of 4-aminothiophenol (4-ATP) (also in varying concentrations) to form azo-bond-containing 4,4'-dimercaptoazobenzene (DMAB) molecules. As the laser illumination time increases, the SERS signal of DMAB will become increasingly distinct, which enables measurements of k, the rate constant of azo-bond formation during the reaction. During this experiment, the Lineweaver-Burk based on the the Michaelis-Menten kinetic equation were also used to obtain the maximal velocity (Vmax) and catalyst- substance affinity (Km). At higher gold nanoparticle concentrations, Vmax and Km increase with increased illumination time, and a relatively long time is required for the full generation of DMAB. At lower gold nanoparticle concentrations, however, Vmax and Km decrease with illumination time, and nano Au-4-ATP compounds are preferentially generated in the reaction instead.

並列關鍵字

Raman spectroscopy ； Photochemical reaction ； silver oxide ； 4-aminothiophenol

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