Studies On Application Of Some Nanocomposites In Electrochemical Sensor

Nanocomposite materials have broader application prospects compared with single nanomaterials because of their characteristics of different components. In this paper, poly(methylene blue) doped silica nanocomposites was prepared using electrochemical methods. Its abilities of electrocatalysis and enzyme-loading were studied for application in the measurement of dissolved oxygen and glucose. In addition, gold nanoparticle/carbon nanotube composites were self-assembled on electrode surface for detection on copper ions. The research objections are relevant to biochemical analysis and environment analysis that are hot fields in analytical chemistry in recent years. The present works will play a positive role in developing new nanocomposites and expanding the application range of analytical chemistry. The main works are summarized as follows:1. The poly(methylene blue)(PMB) modified glassy carbon electrode (GCE) exhibiting different electrochemical behavior was prOepared via two methods, respectively. The PMB polymer, derived from the two-step electropolymerization, suffered structure conversion between Poly(LMB) and Poly(MB·) during cyclic voltammetric measurement and exhibited electrocatalytic activity for reduction of dissolved oxygen (DO). The monodispersed hollow methylene blue doped SiO2nanoparticles were synthesized in the W/O microemulsion. A new material, PMB doped SiO2nanocomposites, presenting monolayer sheets with crosslinked cage structure, were electrochemically polymerized on GCE surface. Compared with PMB film, the nanocomposite material provided a significantly improved sensitivity for reduction of DO and an excellent ability to resist interference from macromolecule contaminants. The detection of DO was performed using the nanocomposite material modified electrode. The calibration curve was linear over a DO concentration range of0.112-5.78mM.2. Poly(methylene blue) doped silica nanocomposites (PMB@SiO2(nano)) on glassy carbon electrode (GCE) were synthesized based on a two-step electropolymerization. Compared with poly(methylene blue) film, PMB@SiO2(nano) had more advantages in facilitating electron transfer between glucose oxidase (GOx) and the electrode surface. GOx immobilized on PMB@SiO2(nano) underwent a direct and reversible electrochemical reaction involving two-electron and two-proton exchange. A reagentless glucose biosensor using the nanocomposite modified electrode was developed. The calibration curve was linear over a glucose concentration range of0.01-1.11mM.The apparent Michalis-Menten constant, Km, for the enzymatic reaction was0.50mM. The developed biosensor presented good accuracy, repeatability, reproducibility and stability as well as an excellent ability to resist interference from ascorbic acid and uric acid species. The investigation indicates that PMB@SiO2(nano) has a good potential for application in construction of the third-generation enzyme biosensor as a conducting matrix material.3. Gold nanoparticles (AuNPs) were electrochemically deposited on carbon nanotube (CNTs) modified glassy carbon electrode (GCE). Cysteine/AuNPs/CNTs/GCE was prepared after adsorption of DL-cysteine hydrochloride. The Cu2+@DL-cysteine complex could be formed on the electrode surface in the presence copper ions. The electrochemical measurements on copper ions were performed based on the redox reaction of the immobilized Cu. The factors influencing Cu2+-detection, such as the deposition time of AuNPs, the concentration of DL-cysteine, the accumulation time of Cu2+, pH, etc. were investigated, respectively. Copper ions in solution were detected using differential pulse voltammetry. Under optimum conditions, the signals depended linearly on the Cu2+concentration in the range of0.1～1mM with a detection limit of60nM.