| This thesis involves two parts:Part one Documents reviewToday, nano-science and technology has entered the limelight and has been investigated extensively by governments and scientists all over the world. It is out of question that the revolution of nano-technology is coming. Nanomaterials, with their size in the range of 0.1-100nm, have received considerable attention in the scientific and engineering fields owing to their unique advantages such as high conductivity, large surface-to-volume ratio, extremely high mechanical strength and modulus. With the unique electrical, optical, magnetic and catalytic performances, they are widely applied in various fields and particularly attractive in electroanalytical chemistry. Nanostructured film modified electrodes have attracted much attention for their advantages on excellent stability, conductivity and electro-catalytic ability, the application of which will bring new chances and challenges to physics, chemistry, biology as well as all sectors of technology.Part two Research reportsLanthanum(III) hydroxide nanowires (LNW) is one of rare earth nanaomaterial. Like other nanomaterials, LNW have attractive properties such as high conductivity and large surface-to-volume ratio. On the other hand, the chemical coordination of La(III) in LNW with multi-hydroxyl compound can recognize the class of biomolecules with multi-hydroxyls. Consequently, using the LNW as an electrode material, combining with the advantages of carbon paste electrode, such as nonpoisonous, easy in preparation and renewal, wider potential window, may bring special advantages in developing novel sensing systems. This dissertation focuses on the fabrication and the application of lanthanum(III) hydroxide nanowires modified carbon paste electrodes. The details are given as follows:Chapter one Voltammetric determination of mefenamic acid at Lanthanum hydroxide nanowires modified carbon paste electrodesLanthanum hydroxide nanowires modified carbon paste electrode (LNW/CPE) exhibiting an electrocatalytic response towards the oxidation of mefenamic acid (MFA) is described. The catalytic action of the LNW/CPE on the oxidation of MFA via one-electron and one-proton transfer is attributed to the formation of the porous construction and the increase of efficient surface of the electrode due to the adulteration of LNW with carbon powers. Using the LNW/CPE, a linear sweep voltammetric method for the determination of MFA and other drugs with diphenylamine parent is proposed. A linear range of 2.0×10-11～4.0×10-9 mol·L-1 is obtained along with a detection limit of 6.0×10-12 mol·L-1.Chapter two The enhancement action of lanthanum hydroxide nanowires towards voltammetric response of dobesilate and its applicationVoltammetric response of calcium dobesilate was observably enhanced at LNW/CPE. The enhancement action was characterized by both the increase of peak current and the reduction of peak potential separation of a pair of the redox peak of CD, which resulted from both the physical increase of efficient electrode surface and the chemical coordination action of La(III) in LNW with hydroxyl and sulfonic groups in CD. With the sensitive oxidation peak of CD at the LNW/CPE, a linear sweep voltammetric method for the determination of CD was proposed. A linear range of 3.0×10-10～1.0×10-8 mol·L-1 was obtained along with a detection limit of 5×10-11 mol·L-1.Chapter three Voltammetric determination of glucose based on reduction of copper (II)-glucose complex at Lanthanum hydroxide nanowire modified carbon paste electrodesA novel voltammetric method for the determination of glucose (GO) is proposed based on the reduction of Cu(II) ion in Cu(II)-GO complex at LNW/CPE. In 0.1 mol·L-1 NH3-NH4Cl (pH 9.8) buffer containing 5.0×10-5 mol·L-1 Cu(II) ion, the sensitive reduction peak of Cu(II)-GO complex was observed at -0.17 V , which was mainly ascribed to both the increase of efficient electrode surface and the selective coordination of La(III) in LNW to GO. The increment of peak current obtained by deducting the reduction peak current of the Cu(II) ion from that of the Cu(II)-GO complex was rectilinear with GO concentration in the range of 8.0×10-7～2.0×10-5mol·L-1, with a detection limit of 2.7×10-8mol·L-1.Chapter four A novel electrochemical sensing system for inosine and its application for inosine determination in pharmaceuticals and human serumThe voltammetric behaviors of inosine at LNW/CPE in the present of Cu(II) ion and K2S2O8 were investigated. The oxidation peak at 0.20V was attributed to inosine oxidation in the formed inosine-Cu(II) complex while the reduction peak at -0.20V to Cu(II) ion reduction in the complex. The electrochemical oxidation potential of inosine was reduced, and the analytical sensitivity and selectivity was improved. A novel sensing system for monitoring inosine was proposed. The oxidation peak current at 0.20V was rectilinear with inosine concentration in the range of 4.0×10-9～2.0×10-8 mol·L-1, with a detection limit of 8.3×10-10 mol·L-1. Chapter five Sensing system integrating lanthanum hydroxide nanowires with copper (II) ion for uracil and its applicationA sensing system for uracil was constituted by using LNW/CPE and by introducing copper (II) ion into supporting electrolyte to transform electroinactive uracil to electroactive uracil-Cu(II) complex. The voltammetric responses of all the complexes at LNW/CPE were more sensitive than that at carbon and multiwall carbon nanotube paste electrodes, which resulted from both the large surface effect of LNW and the chemical coordination of uracil with La(III) ion in LNW. With the sensitive oxidation peak of the uracil-Cu(II) complex at LNW/CPE, a linear range of 4.0×10-9～3.0×10-8 mol·L-1 for uracil was obtained along with a detection limit of 2.0×10-10 mol·L-1.
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