Langmuir-Blodgett films of Nafion-nitrogen Doped Carbon Nanotubes as New Sensing Materials for the Determination of Caffeine in Tea

In this work, Langmuir-Blodgett (LB) technique was proposed to fabricate the homogeneous and controlled films of Nafion-nitrogen doped carbon nanotubes (Nafion-NCNTs). Microstructure and electrochemical performance of LB films of Nafion-NCNTs was characterized by atomic force microscopy (AFM) images, scanning electron microscopy (SEM) images and electrochemical experiments. Moreover, the LB film of Nafion-NCNTs was transferred to the surface of glassy carbon (GC) electrode to fabricate the electrochemical sensor to apply for determination of caffeine. Electrochemical experiments show that the LB films of Nafion-NCNTs modified GC electrode can effectively increase electrochemical response of caffeine. Under the optimum conditions, the oxidation peak current of caffeine was proportional to its concentration in the range of 8.0 × 10 -8 ~ 4.0 x 10 -6 mol L -1 , with a detection limit of 2.0 × 10 -8 mol L -1 . And the modified GC electrode showed excellent selectivity, good stability and repeatability. It also was successfully used for determination of the content of caffeine in tea samples.