Research On Electrochemical Sensor For Heavy Metal Ions Detection

The pollution of heavy metal ions is one of the most serious pollutions due to its harm, persistence and universality. How to detect the heavy metal ions accurately, quickly and conveniently has become a common project for researchers all over the world. Compareing with traditional ion-analysis technologies, electrochemical sensors have a lot of advantages such as the fast detection speed, the simple operability, the uncomplex pretreatment and the low cost. In addition, electrochemical sensors have good feasibility and prospect in the area of ion-analysis. Thus, it is significant to study the electrochemical sensors for heavy metal ions detection.This thesis focuses on developing different electrochemical sensors for heavy metal ions detection combining different technologies and materials such as green metals, screen-printed technology, porous materials, self-assembly, organic ligand probe, DNA molecular probe. The detailed content is as followed:1. Fabricated two bismuth-antimony film electrodes based on the glassy carbon electrode and screen-printed carbon electrode, which were named Bi-Sb film glassy carbon electrode (Bi-SbGCE) and Bi-Sb film screen-printed carbon electrode (Bi-SbSPCE). The performance of the two proposed electrodes to detecting lead(Ⅱ) was also studied, and it was demonstrated that the bismuth-antimony film electrode was better than the corresponding single bismuth film electrode or antimony film electrode. The linear range of Bi-SbGCE and Bi-SbSPCE to lead(Ⅱ) are1μg/L～60μg/L and0.1μg/L～90μg/L respectively.2. A new disposable bismuth-coated porous screen-printed carbon electrode (Bi-P-SPCE) for trace heavy metal ions detection was developed. The Bi-P-SPCE was fabricated by two processes:firstly, the porous screen-printed carbon electrode (P-SPCE) was prepared by combing a printing procedure of a graphite-based layer doped with CaCO3powders with a subsequent dissolution of these powders; secondly, a bismuth film layer was formed on the P-SPCE by in situ electrodepositing Bi(Ⅲ) along with accumulating analytes. Due to the rough surface, large active area and low background noise of P-SPCE, the electrode exhibited significantly enhanced sensitivity for lead(Ⅱ) and cadmium(Ⅱ) detection compared to screen-printed carbon electrode (SPCE) and glassy carbon electrode (GCE). This easy-to-prepare and low-cost electrode was also successfully applied to real water sample analysis. 3. The performance of bismuth film screen-printed carbon electrode (Bi-SPCE) was studied between simultaneous detection and individual detection based on Pb(Ⅱ)-Cd(Ⅱ) and Pb(Ⅱ)-Zn(Ⅱ) systems. The results indicated that there was mutual influence existing among the metal ions when the simultaneous determination takes place by using anodic stripping voltammetry. The detection of one target ion would also be related to the other analyte in the system besides itself in the proposed condition.4. Two electrodes were prepared by self-assembly process on gold electrode for copper(Ⅱ) detection. L-cysteine was modified on gold electrodes via Au-S bond to develop the first electrode and its ability to detect copper(Ⅱ) was investigated by cyclic voltammetry and square wave stripping voltammetry. On the other hand, four small thio organic molecules were designed and synthesized, and Ligand04was successfully modified on gold electrode via Au-S bond. The Ligand04modified gold electrode showed good linear relationship with the concentration of copper(Ⅱ) in certain range.5. A novel electrochemical biosensor for Hg(Ⅱ) determination based on Hg(Ⅱ)-induced DNA hybridization was developed. Owing to forming thymine-Hg(Ⅱ)-thymine (T-Hg(Ⅱ)-T) complexes in the presence of Hg(Ⅱ), this new DNA biosensor was demonstrated valid and efficient to detect trace Hg(Ⅱ) with high sensitivity and good selectivity, without forming hair bin structure nor adscititious indicator. The limit of detection of the proposed DNA biosensor to Hg(Ⅱ) is0.6nM (S/N=3).6. A multi-array microfluid chip combining self-assembly and electrochemical detection was designed. The proposed microfluid chip was cheap and easy to be prepared. The preparation of the chip and the detection principle were disscussed.