| 摘要: | 表面增強拉曼光譜（surface-enhanced Raman spectroscopy, SERS）是一種功能強大的分析技術，能夠藉由分子震動產稱的獨特光譜，辨識出待測物的結構。因此，拉曼光譜可以被視為分子的指紋。DNA定序是藉由四種鹼基（腺嘌呤、胞嘧啶、鳥嘌呤和胸腺嘧啶）產生的訊號差異，判定鹼基排列順序的技術。由於SERS具備極高的辨識度，有潛力應用於DNA定序。在本研究中，我們利用InGaN 量子井研製SERS基板，希望以此紀錄DNA鹼基產生的訊號差異。InGaN量子井可藉由局部表面電漿共振（localized surface plasmon resonance）及電荷轉移（charge transfer）增強SERS訊號，產生每種鹼基專屬的光譜。除此之外，InGaN量子井還能形成高密度的 “熱點”，讓SERS影像展現大範圍的亮點。利用這些影像，我們記錄到每種鹼基的特徵峰，包含: 腺嘌呤的1000 cm-1，胞嘧啶的1241 cm-1，胸腺嘧啶的1668 cm-1和鳥嘌呤的1478 cm-1。利用這些訊號的半高寬，我們估計出每種鹼基的弛豫時間 (relaxation time): 胞嘧啶0.30 ps (C-C伸縮振動)、胸腺嘧啶 0.30 ps (N-H和C-H彎曲振動)、鳥嘌呤 0.30 ps (C=N伸縮振動) 和腺嘌呤0.21 ps (PO43-伸縮振動）。這些結果有機會用來檢測DNA中不同的鹼基。;Surface-enhanced Raman spectroscopy (SERS) has emerged as a powerful analytical technique since it reveals detailed insights into the vibrational modes of molecules, which is often regarded as the molecular fingerprints. DNA sequencing is the process of determining the precise order of nucleobases (adenine, cytosine, guanine, and thymine) within a DNA molecule. Because of its excellent specificity, SERS can be a potential tool for DNA sequencing. In this study, we explore the viability of using SERS to differentiate nucleobases. To achieve the goal, InGaN quantum wells were employed to build the SERS substrates. The nitride quantum wells enhance the Raman signals via two mechanisms in SERS, namely localized surface plasmon resonance (LSPR) and charge transfer (CT), which result in the distinct SERS spectrum of each nucleobase. In addition, the quantum wells produce the SERS images with multiple “bright” regions, attributed to the much densified hot spots. With the SERS images, we recorded the characteristic bands (the “fingerprints”) for each nucleobase, including 1000 cm-1 for Adenine, 1241 cm-1 for Cytosine, 1668 cm-1 for Thymine and 1478 cm-1 for Guanine. The four vibrational modes are of the relaxation time (approximately 0.30 ps for the C-C stretching of Cytosine, N-H and C-H bending of Thymine, C=N stretching of Guanine and 0.21 ps for the PO43- stretching of Adenine). These distinct signals can be used to identify the nucleobases in DNA’s with different sequences. |
