Nano-structured Interface To Build And Its Application In The Preparation Of Horseradish Peroxidase Sensing

Nanomaterials and nanotechnology attract more and more interesting because of their special properties and potential applications. The aim of the nanotechnology is to develop the functional devices for high selective and sensitive assay in analytical chemistry.In this work, the nanomaterials and composite nanomaterials are used to construct the electrochemistry biosensors by means of the combination of biochemistry, molecular self-assembly nanomaterial and biosensor will be discussed.1. Developing three new methods to immobilize Horseradish Peroxide (HRP) to construct interface in analyzing Hydrogen Peroxide.(1) In the second chapter, composite film is formed by combining Gold Nanoparticles (GNPs) with Nano TiO2, which is used to immobilize HRP firstly. The experiment validates that the composite film can provide conductive channels and reduce the distance between the electrode and the centre of HRP. Direct electrochemistry of HRP has been realized by this methold. UV-VIS Spectrophotometer and Transmission electron microscope (TEM) are used to characterize the change of the composite film. The result shows that HRP contain its own bioactivity. The HRP modified electrode also exhibites a good catalytic activity towards the reduction of H2O2. The responses of H2O2 are linearly proportional to the concentration from 2.5×10-6～1.75×10-5 M with a detection limit of 1.2×10-6 M (S/N = 3).(2) In the previous study, we know the humidity and the temperature influencing the preparation of the modified electrode. Besides, it takes long time to make the film dry and needs more HRP.In the chapter 3, the self-assembled methold is introduced to contruct the interface of HRP biosensor. Direct electrochemistry of HRP is observed at glassy carbon electrode (GCE) modified with two steps of self-assemblies by poly (dimethyl diallyl) ammonium chloride (PDDA) and GNPs through electrostatic interaction. UV-VIS Spectrophotometer and Scanning electron microscopy (SEM) are used to monitoring the process of the self-assembly. The responses of H2O2 were linearly proportional to the concentration from 1.0×10-6 to 3.0×10-6 as well as 3.0×10-6 to1.0×10-4 M with a detection limit of 4.2×10-7 M (S/N = 3).(3) We attempt to design the component and the structure of the molecular with the aim to achieve accurate SAMs with special function.In the chapter 4, phytic acid sodium is introduced to replace polyelectrolyte due to controlling the structure difficultly. Phytic acid and GNPs are assembly onto the surface of Gold electrode to forming the Layer-by-Layer assembly three-dimensional interface which is used to absorb HRP. Surface Enhanced Raman Scattering (SERS) and electrochemical impedance are applied to characterizing the process of forming membrance. The responses of H2O2 are linearly proportional to the concentration from 2.5×10-5～1.0×10-4 as well as 1×10-4～4×10-3 M with a detection limit of 8.6×10-6 M (S/N = 3).2. Electrochemical and Raman Scattering Studies of Short-chain L-cysteine Self-assembled Monolayers on the Gold Surface(4) In recent years, SAMs attracts an increasing attention and has been widely used. The defects of the SAMs have seldom investigated by the technology of electrochemistry and Raman scattering spectroscopy until now. L-cysteine with functional group- amido and carboxyl has been normally used in modified electrode, electrocatalysis and biosensor. In the chapter 5, using potassium ferricyanide as an electron transfer prober, the electrochemical behavior of the L-cysteine and dodecanethiol monolayers on the gold electrode surface is investigated. Surface enhanced Raman scattering spectroscopy is applied to confirm the dense and stability of the L-cysteine monolayer using dodecanethiol as a prober for detecting the defects.