| Electrochemical sensor, the chemical sensor that translate detecting signal into electric signal by electrochemical effect, is the maturest one in chemical sensors. Electrochemical sensor was widely used in the analytical determination. Enzymatic or protein biosensors, which can detect analytes using the specific reaction of bioactive materials such as the enzyme-substrate, enzyme-coenzyme, antigen-antibody, incretion-acceptor and so on, have attracted much attentions due to their good selectivity. Nanoparticles have many extraordinary features such as huge specific surface area, strong catalytic activity and good bio-compatibility. Study on the electrochemical behavior of protein on the nanoparticles modified electrode is one of the main research works of the thesis. Howerver, the enzymatic or protein biosensors are limited by the stability of the enzyme to both pH value and temperature with the development of biosensor. As such recent effort has been put into producing nonenzymatic biosensors. we also used the nanoparticles to fabricate nonenzymatic biosensors and studied the other electrochemical behaviors of the nanoparticles modified electrode in this paper.This section described the concept, classification and actuality of electrochemical biosensor, the nanoparticles and it's application in electrochemical biosensor, the polymer and graphene and the study of their compounds.In part two, monodispersed urchinlike spherical ceria nanoparticles (CeO2 NPs) with rough surface were prepared via a simple one step hydrolysis process in glycol and have been utilized for immobilization of proteins to fabricate the third biosensor. Those as-prepared CeO2 NPs have good biocompatibility, favorable conductivity, large surface area, as verified by transmission electron microscopy (TEM) and X-ray powder diffraction spectroscopy. UV-vis spectroscopy analysis of the Mb/CeO2 NPs film suggested that the immobilized Mb could retain its natural structure, which is illuminated that the prepared CeO2 NPs have excellent biocompatible. The modified glassy carbon electrode (GCE) by Mb and CeO2 NPs exhibited direct electrochemistry with a fast electron transfer rate (1.03 s-1) and good electrochemical performance to reduce hydrogen peroxide (H2O2). The proposed biosensor shows a linear response to H2O2 concentrations ranging from 0.7μM to 194μM with a detection limit of 0.3μM at a signal-to-noise ratio of 3 and the low value of apparent Michaelis-Menten constant (0.048 mM) indicates enhanced enzyme affinity of Mb to H2O2. Therefore, our experiments implemented the fast direct electron transfer (DET) of proteins indicated the present CeO2 NPs may provide a favorable bio-microenvironment for proteins immobilized on the electrode surface and enhance electron transfer between proteins and electrodes.In part three, a novel hollow matrix, CeO2-ZrO2 solid solution nanocages particles which synthesized by hydrothermal method via Kirkendall Effect, were used for immobilizing myoglobin (Mb) to fabricate protein electrodes suitable for studying the direct electron transfer between the redox centers of proteins and the electrode. The transmission electron microscopy (TEM), UV-vis and electrochemical measurements showed that the matrix was well biocompatible and could retain the bioactivity of immobilized protein to a large extent. The direct electron transfer of the immobilized myoglobin (Mb) exhibited a couple of stable and well-defined redox peaks in 0.1 M pH 6.98 PBS. The Mb/CeO2-ZrO2 modified electrode also exhibited excellent catalytic performance for H2O2 with the detection limit of 1.1μM, apparent Michaelis-Menten constant (KMapp) of 0.128 mM and the linear response range was from 8.5μM to 330μM. This matrix could accelerate the electron transfer between Mb and the electrode with a surface controlled process and an electron transfer rate constant ks was 2.65 s-1. CeO2-ZrO2as a good material for immobilization of protein can facilitate the development of electrochemical biosensor.In part four, direct electron transfer (DET) of myoglobin (Mb) was achieved by its direct immobilization on magnetic glassy carbon electron (MGCE) with the big magnetic Fe3O4@ZrO2 Core-Shell microspheres as binder, the material can fast immobilized on the MGCE. A pair of well-defined redox peaks, characteristic of the protein heme FeⅡ/FeⅢredox couples, was obtained at the Mb/Fe3O4@ZrO2 film on magnetic glassy carbon electrode (MGCE), as a consequence of the direct electron transfer between the protein and the MGCE electrode. The redox peaks were acquired in 0.1 M phosphate buffer solution (pH 6.98) with oxidation potential of-326 mV, reduction potential of-363 mV, the formal potential E0 (E0=(Epa+Epc)/2) at-345 mV and the peak to peak potential separation of 37 mV at 100 mV·s-1. The average surface coverage of the electroactive Mb immobilized on the electrode surface was calculated as 4.82×10-11mol·cm-2. Mb retained its bioactivity on modified electrode and showed excellent electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2). The cathodic peak current of Mb was linear to H2O2 concentration in the range from 1μM to 76μM with a detection limit of 0.32μM (S/N=3). The apparent Michaelis-Menten constant (KMapp) and the electron transfer rate constant (ks) were estimated to be 40μM and 1.4 s-1, respectively. The biosensor achieved the direct electrochemistry of Mb on Fe3O4@ZrO2 Core-Shell microspheres without the help of any supporting film or any electron mediator.In this section we prepared the PANI/GO firstly by in-situ polymerization and then grow up Pt NPs on both of the surfaces of PANI/GO, the Pt NPs which loaded on the PANI/GO has small size and ultra-high density. The structure and character of different compounds were tested with SEM, TEM, XRD, FT-IR and thermogravimetric and so on. We tested the electrochemical behaviors of different modified GCE, and the Pt/PANI/GO/GCE showed excellent electrocatalytic activity to O2 and methanol, it also performed good electricity response of the H2O2 and glucose under the optimized conditions.
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