Study On Functioned Graphene Nano-Composites Modified Electrode For Detection Of Lead

The pollution of heavy metal has shown a deteriorating trend and greatly endangered the health of human beings and the natural environment in our worldwide. With the rapid industrial development today, inevitably, the heavy metals are widely used in various fields of environment and food health. And it's hard to prevent if we don't take care of it. Calling for environmental supervision departments to strengthen the environmental monitoring and protection, it's imperative to developed a fast-simple and fast-accurate detection and monitoring equipment. The susject chosen the graphene as a base material and synthesized a series of composites of nitrogen-doped graphene/metal nanoparticles after reduction and nitrogen-doping of graphene oxide via electrochemical means. A seriers of lead electrochemical sensors were built to achieve a high sensitivity and steady and rapid detection by modifying the composites onto the glassy carbon electrode surface.First of all, nitrogen-doped graphene was hydrothermally synthesized by reduction of graphene oxide with urea as the nitrogen source. After that, we designed and synthesized three kinds of nanoparticles with different morphologies, including AuNPs, Au@Fe₃O₄ and Au@SiO₂@Fe₃O₄ nanoparticles. After mixing with nitrogen-doped graphene, we prepared AuNPs/NG, Au@Fe₃O₄/NG and Au@SiO₂@Fe₃O₄/NG composites. Moreover, the SEM, the FT-IR spectrum and the XRD spectrum were used to characterize these composites.Secondly, on the basis of successful synthesis of composites, these three composites were modified on the GCE surface by dropping method. After drying, the electrodes were immersed into the L-cysteines solution to prepare the L-cys/AuNPs/ NG/GCE, L-cys/Au@Fe₃O₄/NG/GCE and L-cys/Au@SiO₂@ Fe₃O₄/NG/ GCE electrochemical sensors.Finally, cyclic voltammetry?CV? and square wave anodic stripping voltammetry?SWV? were used to investigate the electrochemical response between sensors and lead. The result of CV exhibited that the conductivity of the working electrode modified with the composites was improved greatly. The SWV examined the differences between the electrodes modified with different composites and the response signal of lead. It's found that the nitrogen-doped graphene/metal nanoparticles modified electrode functionized with L-cysteines have a best electrochemical signal. Besides, we studied the effects of different experiment condition, including the amount of modified materials, the preconcentration time and the pH of solution, to optimal experiment condition. Compared the response signal curves of three different electrochemical sensors, it's found that the different structure of nanoparticles have different effects towards lead. Most importantly, the properties between nanoparticles can achieve complementary advantages. And the synergies in different nanoparticles can promote to realize a best performance. The results showed that all of the three sensors have excellent electrochemical signals toward lead ions and could reach lower limit of detection?LOD?. Furthermore, L-cys/Au@SiO₂@Fe₃O₄/NG/GCE electrochemical sensor exhibited a shortest preconcentration time, a best stability, a lowest LOD and a most excellent interference property. In a word, the experiment has successfully constructed of lead-ion electrochemical sensors which realized the trace detection of lead ions, which is greatly worth of application and promotion.