Electrochemical Applications Based On Hierarchical Nanocomposites

Transition metal or its oxides were considered to be a good artificial enzyme for wide utilization in electrochemical sensor, electro-catalysis and so on. While it exists some fatal weakness result to some undesirable influence, such as it lacks of selectivity due to it as an artificial enzyme and the single metal or its oxide will often suffer the natural defects of the electrical conductivity because of the agglomeration of nanoparticles. Hence it is important to improment the specifity and to search a new effective support materials. Molecular imprintingtechnology is a kind of preparation polymer technology for a particular molecule has specific recognition performance. The molecular imprinted polymers possess lots of advantages such as high affinity and selectivity, good stability, low preparation cost long service life and so on. Ion selective electrode is a kind of electrochemical sensors for detection the ion concentration by the untilization of the membrane potential. However, it is easy to form a water layer between the ion selective membrane and ion conductor. It will result to the instability of the membrane potential. Three-dimensional porous carbon(3D-PC) produced by metal organic framework possesses open connection holes, inner hydrophobic, large capacity and the potential stability. Biomass-derived 3D-PC may be the most suitable support materials due to large specific surface area, huge sources, low cost and easy preparation. So this paper aim to build better electrochemical sensor from the above aspects. The main work is as follows:1.In this work we prepared a new molecularly imprinted polymer(MIP) designed by self-polymerization ofdopamine on the Fe3O4nanoparticles(NPs) surface in weak base aqueous solution in thepresence of template thionine. The magnetic molecular imprinted polymers(MMIPs) were characterized by scanning electron microscopy,X-ray diffraction and Energy Dispersive X-Ray Spectroscopy. To further study the electrochemical property of the sensor influenced by the amount of the template molecules. The experimental result was shown that the electrocatalytic detection of MMIPs towards H2O2 exhibited good linear relationship in the range of 4.082 nM~9?Mwith low detection of1.583 nM when the concentration of thionine is 20?M. the eletrocatalytic detection of MMIPs toward Acetylcholine(ATCL) exhibited well linear relationship in the range of 2.85~160 ?M with low detection of 0.856 uM. The result is that the linear relationship of Acetylcholine esterase(AChE) and Choline oxidase(ChoX) respectively is 0.526~20000 ng/m L and 22.76~400 ng/mL. The low detection of AChE and ChoX is 0.158 ng/m L and 6.829 ng/mL.2. A three-dimensional(3D) kenaf stem-derived 3D porous carbon(3D-PC)/Co3O4 precusor compositewas constructed based on the 3D-PC loaded on Co3O4 precusor by hydrothermal method. After that, the 3D-PC/Co3O4 composite was constructed by the calcining the 3D-PC/Co3O4 precusor composite. The 3D-PC /Co3O4 composite can used as one electrode for glucose detection because of the kenaf stem derived porous carbon have good electric conductivity. It also simplifys the process of the electrode preparation. The 3D-PC can provide more electrochemical active site to immobilized Co3O4 nano clusters for avoiding the stack of the Co3O4 nanoparticles because of it has huge specific surface area. Proved by the experiment results, the electrochemical detection of 3D-PC /Co3O4 one electrode toward by glucose showed wonderful linear relationship in the range of 0.088-7 mM(R2=0.9947) with low detection of 26 ?M(S/N=3).3. The new type of solid-contact ion-selective electrode(SC-ISE) was constructed based on a three-dimensional(3D) porous carbon(PC) by calcining Zn4O(BDC)3(MOF-5, BDC =1,4-benzenedicarboxylate) as the intermediate layer between a glassy carbon electrode and an ionophore-doped ISE membrane(H+-ISM). We further studied the H-ISM/3D-PC/GCE stability, electrical conductivity, the linearity scope and interference immunity by the chronopotentiometry, EIS and potentiometric technology. The study found the eletrochemical detection of H-ISM/3D-PC/GCE toward pH exhibited well linear relationship in the range of pH=4.5 ~8.0 which is suitable for testing the change of pH in vivo. Finally, this new solid ion selective electrode can be used to detection the value of 0.2 pH change in vivo for real-time.