Investigation On Enzyme-free Electrochemical Sensors Based On Nanomaterials

With the appearance of new nanomaterials and nanocomposite and the constant innovation of modified methods of electrodes, sensing research based on nanomaterials, especially enzyme-free electrochemical sensing research, shows great potential. In this dissertation, eight kinds of enzyme-free electrochemical sensors were fabricated based on nanomaterials and the electrocatalysis of sensors were investigated in details. The new electrochemical methods for the determination of nitrite, glucose, catechol, hydroquinone, Hydrogen peroxide and hydroxylamine were set up. These results are significant to enrich the research of electrochemical sensors and provide new thoughts for the construction of high sensitive and selective electrochemical sensors. These results also broaden the application range of nanomaterials. The dissertation consists of four chapters. The author's main contributions are summarized and presented as follows:1. By electrodeposition in which MWCNTs were used as template, three kinds of enzyme-free electrochemical sensors based on porous CoOx/MWCNTs, ZrO2/MWCNTs, TiO2/MWCNTs nanocomposite were fabricated and their electrocatalytic behaviors were investigated, respectively. The corresponding electrochemical methods were presented for the determination of NO2-, catechol and hydroquinone, respectively. The experimental results indicated that CoOx/MWCNTs and ZrO2/MWCNTs showed excellent electrocatalytic activity toward the oxidation of nitrite. The linear range for the determination of nitrite were found to be5.0×10-7～2.5×10-4mol·L-1and5.0×10-7～1.1×10-3mol·L-1, respectively. And the detection limit was3.0×10-7mol·L-1(S/N=3). TiO2/MWCNTs can distinguish between catechol and hydroquinone, and showed excellent catalytic properties toward the oxidation of catechol and hydroquinone. The linear range for the determination of catechol and hydroquinone were found to be1.5×10-6～3.0×10-4mol·L-1and3.0×10-4～3.5×10-3mol·L-1. The linear range for the determination of hydroquinone were2.5×10-6mol·L-1～2.0×10-4mol·L-1and4.0×10-4mol·L-1～2.0×10-3mol·L-1.And the detection limit was8.0×10-7mol·L-1(S/N=3). The electrochemical sensors based on the three porous nanomaterials indicated these characteristics of simple preparation, high sensitivity and fast response, which were mainly because large specific surface area of porous nanocomposite can promote electronic transfer and improve the catalytic performance of nanocomposite.2. By electrodeposition and self-assembly, three kinds of enzyme-free electrochemical sensors based on Au/Ch, Cu/MnO2and Ag/L-Cys were fabricated and their electrocatalytic behaviors were investigated. The new electrochemical methods were presented for the determination of hydroxylamine, glucose, H2O2. The experimental results indicated that Au/Ch showed excellent electrocatalytic activity toward the oxidation of hydroxylamine. The linear range for the determination of hydroxylamine was found to be1.3×10-6～8.0×10-4mol·L-1and the detection limit was6.0×10-7mol·L-1(S/N=3). Cu/MnO2exhibited excellent electrocatalytic activity toward the oxidation of glucose. The oxidation peak current had a linear relationship with the concentration of glucose in the range from2.5×107mol·L-1to1.0×10-3mol·L-1with a very low detection limit of1.0×10-7mol·L-1(S/N=3). Ag/L-Cys showed excellent electrocatalytic activities toward the reduction of H2O2with the linear range of2.5×10-6mol·L-1to1.5×10-3mol·L-1. The detection limits were7.0×10-7mol·L-1(S/N=3). The three electrochemical sensor based on self-assembly have the advantages of simple structure, flexible control and good stability.3. The formation of Thulium (Ⅲ) hexacyanoferrate (Ⅱ)(TmHCF) nanoparticles induced by enzymatic reaction on the surface of carbon-paste electrode (CPE) and GOx-CHIT/GCE was described and characterized. The new electrochemical methods were presented for the determination of glucose. The experimental results indicated that the linear relationship between current response of TmHCF and glucose concentration were3.9×10-4～7.0mol·L-1and2.0×10-5～1.4×10-2mol·L-1, respectively. These research explore new application of the biological catalysis in electroanalytical chemistry, offer new ideas for the synthesis of nanomaterials, and provide a general platform for the construction of electrochemical biosensors.