Study Of Novel Nanomaterials And Their Applications In Environmental And Biological Sensing

The nanomaterials have attracted more interest in the study of researchers from the early 1980s, because of the special physical, chemical properties and broad application. Nano materials can be divided into three categories:the nanoparticles. nano solid and nano assembly system. Nanomaterial is the particle with the scale in 1～100 nm. The unique structure makes it has four effects:surface effect, small size effect, quantum size effect and macroscopic quantum tunnel effect. Nanoparticles with unique chemical and physical properties can be applied in the field of electrical, optical, catalytical, magnetic materials, biological technology, drug delivery, etc. The Use of nanomaterials and nanotechnology modified electrodes and nano materials luminescent quantum dots and combination of molecular imprinting technique to analyze the testing substance made the measurement rapid and convenient.In recent years, chemical modified electrode has become hotpot in the research. The most obvious advantage of modified electrode is that they can be modified with functional group as people needed. The application of the quantitative measurement is the combination system of separation, gathering and measurement to extend the range of electrochemical analysis. Because of its excellent selectivity, high sensitivity, rapid response, low cost and continuous on-line measurement in complex system. It has been widely used in the environment monitoring, biology, medical science, medicine, food and military and promising for these fields.This paper are focusing on the research of modified method for electrode and probe the catalytic process of electro-active molecule and surface of the electrode to prepare the good selective, high sensitive biosensors. Meanwhile, we made use of the modified electrode to study the pesticide in vegetables and fruits and neurotransmitters in brains. The results of the tests are proved to be good. In this paper, we used the materials such as carbon nanotubes, redox enzyme, PAMAM preparared metal nanoparticles and silica molecularly imprinted materials with quantum dots as reaction platform. We characterized the surface topography by SEM. TEM to study the sensors. In the aspect of chemical modified electrodes. we used the methods of current-time curves, ac impedance, circular voltammetric to investigate electrochemical properties and catalytic response mechanism of the active substances on modified electrodes on the desighed functionally electrodes and thus build the effective new chemical modified electrodes for environmental and food safety detection. This paper also discussed the luminescent quantum dots and silicon ball of molecularly imprinted materials for detection of parathion-methyl. This thesis will strive to combination of nanotechnology, molecular imprinting technique, quantum dot technology, and environmental science, food safety, neurotransmitters detection The primary research work is as follows:Chapter 1 OverviewIn this part, a detailed outlines and reviews mainly on the characteristics, preparation and application of nano materials. It also contains the summary of the chemical modified electrode and the combination of nano materials and electrode.. After a review of CMEs. the development and application of nanotechnology and molecularly imprinted technology into biosensors and application of quantum dots with MIP technology were highlighted. Finally, we emphatically pointed out the purpose and significance of the dissertation, its innovation spot and content as well.Chapter 2 Layer-by-Layer self-assembled acetylcholinesterase/ PAMAM- Au on CNTs modified electrode for sensing pesticides electrode for sensing pesticidesIn this paper. an acetylcholinesterase (AChE)/dendrimers polyamidoamine (PAMAM)-Au/Carbon nanotubes (CNTs) multilayer modified electrode based on LbL self-assembled technique was employed in the detection of carbofuran in samples. The configuration of the nanostructure on the electrode provided a favorable environment to the immobilization of AChE. The modified films also improved the electrocatalytic characteristics and electron transfer speed between the films and the surface of electrode. The PAMAM-Au nanoparticless were characterized by SEM and UV-VIS methods. A set of experimental conditions were also optimized for the detection of the pesticides. A linear response over cabofuran concentration in the range of was exhibited with a detection limit of. The biosensor showed high sensitivity, good stability and reproducibility with promising application.Chapter 3 On-line microdialysis system with poly (amidoamine)-encapsulated Pt nanoparticles biosensor for glutamate sensing in vivoIn this work, an amine-terminated poly (amidoamine) dendrimer containing Pt nanoparticles (PAMAM/Pt)nanocomposite was synthesized and a novel amperometric H2O2 biosensor based on PAMAM/Pt and MWCNTs was developed. The resulting film of MWCNTs/PAMAM/Pt was characterized by transmission electron microscopy (TEM), linear sweep voltammetry (LSV) and amperometric i-t curve. It demonstrates excellent electrocatalytic responses toward the reduction of H2O2 at -200 mV (vs.SCE) without HRP participation. Immobilized with glutamate oxidase (GlutaOx), an effective glutamate biosensor, was fabricated, and the in vivo detection for glutamate was realized combining with the on-line microdialysis system. The glutamate biosensor showed good linear range from1.0μM to 50.0μM with the detection limit of 0.5μM (S/N=3). The basal level of glutamate in the striatum of rat was detected continuously with this on-line system and was calculated to be 5.80±0.12μM (n=3). This method was proved to be sensitive and selective and may be feasible in the further application of physiology and pathology.Chapter 4 Determination of Parathion-methyl in Vegetables by Fluorescent-Labeled Molecular Imprinted PolymerA novel sensor for the determination of parathion-methyl based on couple grafting of functional molecular imprinted polymers (MIPs) was fabricated which is developed by anchoring the MIP layer on surfaces of silica particles embedded CdSe quantum dots by surface imprinting technology. The synthesized molecular imprinted silica nanospheres (CdSe@SiO2@MIP) allows a high selectivity and sensitivity of parathion-methyl via Fluorescence intensity decreasing when the M1P material rebinding the parathion-methyl molecule. Compared with the MIP fabricated in traditional method, the template of parathion-methyl was easier to remove from the CdSe@SiO2@MIP imprinted material. Under the optimal conditions, the Fluorescence intensity of parathion-methyl at the imprinted sensor was detected by spectrofluorophotometer. The relative fluorescence intensity of CdSe@SiO2@MIP decreased linearly with the increasing concentration of parathion-methyl range from 0.013 mg Kg-1 to 2.63 mg Kg-1 with a detection limit (3σ2) of 0.004 mg Kg-1 (S/N=3), which is lower than the MIP in tradition. The imprinted film sensor was applied to detect parathion-methyl in vegetable samples without the interference of other organophosphate pesticides and showed a prosperous application in the field of food safety.