In present study, a novel and facile electrochemical sensor based on glassy carbon electrode (GCE) modified with nitrogen-doped carbon nanotubes (N-CNT) decorated with poly (L-Cysteine) (PLCY) were fabricated and applied for the simultaneous voltammetric determination of theophylline (THEO) and caffeine (CAF). The morphology and structure of multilayer film modified on the surface of glassy carbon electrode were investigated successfully by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Raman Spectroscopy. And the properties of the modified electrode were investigated by Chronocoulometry (CC), Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) were utilized to investigate the electrochemical behavior of THEO and CAF on the composite film modified electrode. The results showed that the determination towards THEO and CAF can be operated at the same potential window with the oxidation current peak separated and non-interfering respectively. Compared to the bare GCE, the PLCY/N-CNT/GCE can signally meliorate the electrocatalytic activity towards the oxidation of THEO and CAF with a remarkably increase in the anodic peak currents of 495.94% and 465.48%. Under the optimal conditions, the fabrication multilayer film sensor had excellent performances in determination towards THEO and CAF with a wide linear dynamic range from 0.10 to 70.0 μM and 0.40–140.0 μM, low detection limit (S/N = 3) of 0.033 μM and 0.20 μM, respectively. The PLCY/N-CNT/GCE sensor also had advantages as easy-made, high-sensitivity, stability and reproducibility. Moreover, it was successfully used to analyze the THEO and CAF in green tee, oral theophylline sustained release tablets and energy drink sample with a satisfactory result.

本研究制备了一种新型的，简便的电化学传感器，该传感器基于修饰有掺杂半胱氨酸（PLCY）的氮掺杂碳纳米管（N-CNT）修饰的玻碳电极（GCE），并用于同时伏安法测定。茶碱（THEO）和咖啡因（CAF）。通过扫描电子显微镜（SEM），透射电子显微镜（TEM）和拉曼光谱法成功地研究了玻碳电极表面修饰的多层膜的形貌和结构。并通过计时容量法（CC），循环伏安法（CV）和差动脉冲伏安法（DPV）研究了修饰电极的性能，研究了THEO和CAF在复合膜修饰电极上的电化学行为。结果表明，对THEO和CAF的测定可以在相同的电位窗口下进行，氧化电流峰分离且无干扰。与裸露的GCE相比，PLCY / N-CNT / GCE可以显着改善对THEO和CAF氧化的电催化活性，阳极峰值电流显着增加495.94％和465.48％。在最佳条件下，制造的多层膜传感器对THEO和CAF的测定具有出色的性能，线性动态范围从0.10至70.0μM和0.40至140.0μM，检测限低（S / N = 3）为0.033μM，并且分别为0.20μM。PLCY / N-CNT / GCE传感器还具有易于制造，高灵敏度，稳定性和可重复性的优点。而且，