A Study Of Electrochemical Sensors Based On Graphene Composites For The Copper Ion Detection

With the rapid development of industry, a series of prominent environmental pollution problems, especially, the pollution of heavy metal ions existing in water environment, have emerged. Copper, as one of closely associated with human beings heavy metal materials, has detrimental risk to both human health and ecological systems. Therefore, to explore some new materials and high-efficiency and accurate methods to detect and monitor the heavy metal ions is critical. A series of graphene-based nanomaterials were synthesized based on graphene oxide modified with chemical or physical methods. Analytical performance of the obtained graphene-based composites modified glassy carbon electrodes for the determination of Cu²⁺ in the solution were evaluated by differential pulse anodic stripping voltammetry?DPV?. The main contents are as follows:1. Firstly, graphene oxide?GO? was synthesized with the improved Hummers method. Next, by utilizing the surface-exposed epoxy groups in GO and the terminal amino in branched polyethyleneimine?PEI?, PEI covalent modified graphene oxide was synthesized via the nucleophilic substitution. And using sodium borohydride as reducing agent to obtain PEI-RGO nanocomposites. Finally, we modified a glass carbon electrode?GCE? using PEI-RGO nanocomposites as sensing material to fabricate an electrochemical platform for the detection of Cu²⁺ in solution by differential pulse anodic stripping voltammetry?DPV?. Highly selective detection toward Cu²⁺ was achieved in the PEI-RGO/GCE due to the PEI can recognize Cu²⁺with high selectivity via a coordination action. The calibration curves was ipc??A?=0.00527c??mol/L? + 0.8150 for Cu²⁺ in the ranges of 1 to 70umol/L. The limit of detection was 0.35?mol/L based on three times of the background noise?S/N=3?. It demonstrated that the PEI-RGO nanocomposite was a promising sensing material for highly selective detection toward Cu²⁺ in water environment.2. After reduction the as-obtained graphene oxide to graphene, we use L-tryptophan to non-covalent modify graphene via the strong ?-? interaction between graphene?RGO? and L-tryptophan?L-Trp?. Trp-RGO nanocomposites were modified on glassy carbon electrodes to detect copper ions in solution. It was found that Trp-RGO modified GCE exhibited excellent sensitivity for the detection of Cu²⁺,which could be attributed to combination the benefits of the coordination between Trp and Cu²⁺, and specific surface area and excellent electric catalytic performance of RGO. The calibration curves was ipc??A?=0.8081c??mol/L? + 5.9128 for Cu²⁺ in the ranges of 0.24 to 48?mol/L. The limit of detection was 0.0064?mol/L based on three times of the background noise?S/N=3?. The Trp-RGO/GCE showed excellent stability for repetitive DPV measurements with a relative standard deviation?RSD? of2.13%.3. Using graphene oxide as the precursor, amino-functionalized graphene?NH₂-G? materials were prepared, in which the electrochemical performance and dispersity of graphene sheets can be improved. Then, amino-functionalized graphene/chitosan?NH₂-G/Cs? composites were synthesized by electrostatic interaction between chitosan and amino-functionalized graphene. A novel Cu²⁺electrochemical sensor based on NH₂-G/Cs composites modified glassy carbon electrode was obtained. Combined with the improved electrochemical performance and high surface area of NH₂-G and excellent film-forming ability and high affinity to Cu²⁺ of Cs, the proposed sensor provided a good platform for highly selective and sensitive detection of Cu²⁺. The calibration curves was ipc? ?A?=1.0553c??mol/L?+2.9608 in the ranges of 0.4 to 40?mol/L. The limit of detection was 0.04?mol/L based on three times of the background noise?S/N=3?.