| Research on the morphology-dependent electrochemistry sensing properties of metal oxides is one of the hotspots in the fields of electrochemical analysis because of the unique advantages of metal oxides in photoelectric catalytic activity, specific surface area, and electronic transmission performance. Morphology-controlled preparation methods for aluminas, iron oxyhydroxide and ceria were studied and the influences of morphology on the electrochemical enhancement were systematically studied in this thesis. As a result, novel highly sensitive electrochemical sensing platforms were constructed of neurotransmitter, endocrine disruptors, phenolic pollutants and food colourants. The research work of this thesis mainly contains the following six parts:(1) Using Al(NO3)3·9H2O as the Al source and urea as the base source, different-shaped aluminas were readily prepared by changing the reaction time via hydrothermal reaction. It was found that the morphology and the electrochemical sensing properties of alumina were heavily dependent on the reaction time. When extending the reaction time from 6 h to 24 h, the obtained alumina samples changed from amorphous bumps to regular microfibers in diameter of 200 nm. Moreover, the BET surface area, electrochemical response area and electron transfer ability were gradually enhanced. The electrochemical behaviors of amaranth on the surface of alumina that prepared by different reaction time. The oxidation signals of amaranth increased remarkably and then kept stable. Electrochemical tests proved that alumina microfibers were more active for the oxidation of amaranth and exhibited much higher enhancement effect, compared with alumina bumps. The influences of pH value, amount of alumina microfibers, and accumulation time on the signal enhancement of amaranth were discussed. As a result, a novel electrochemical method was developed for the detection of amaranth. The linear range was from 1 to 150 nM, and the limit of detection was 0.75 nM after 1-min accumulation. The analytical application in drink samples was investigated, and the relative error was less than 10% compared with the values that obtained by high-performance liquid chromatography.(2) By controlling the molar ratio of 1:9:90 for Al, urea and H2O, porous alumina microfibers were prepared after 24 h-reaction, and then used to modify the carbon paste electrode. The electrochemical behaviors of ponceau 4R and tartrazine were studied, and two oxidation waves at 0.67 and 1.01 V were increased remarkably on alumina mircrofibers-modified electrode. The oxidation mechanisms were studied, and their oxidation reaction involved one electron and one proton. Baed on the strong signal amplification strategy, a novel electrochemical method was developed for simultaneous detection of ponceau 4R and tartrazine. The linear rangers were 1-100 nM and 5-140 nM for ponceau 4R and tartrazine. The detection limits were 0.8 nM and 2.0 nM. This new sensor was used in different drink samples, and the relative errors were less than 9%, compared with the values that obtained by high-performance liquid chromatography.(3) Using the mixture solution containg Fe(NO3)3·9H2O?EG and PEG 2000 as the solvothermal system and NaA?NH3·H2O and NH4Ac as the morphology-tuning reagents, iron oxyhydroxide (FeOOH) structures with the morphology of bulk, nano-sheet, nano-sphere, and nano-rod were prepared. The electrochemical behaviors of diethylstilbestrol (DES) and bisphenol A (BPA), two typical environmental estrogens, were studied. The electrochemical reactivity of the prepared FeOOH sampels toward the oxidation of DES and BPA were morphology-dependent. The differences of electron transfer rate and accumulation efficiency were the dominant reason for different signal enhancement abilities of FeOOH. The FeOOH-4 nanorods that prepared in the presence of NH4Ac were more sensitive for the oxidation of DES and BPA, and significantly enhanced the oxidation signals of DES and BPA. Thereafter, an electrochemical platform was established for the simultaneous detection of DES and BPA. The linear ranges were 1-1000 nM and 1-1000 nM for DES and BPA, and the detection limits were 3.5 nM and 5.0 nM. This new sensing platform was used in the analysis of water samples, and the results were compared with the values that obtained by high-performance liquid chromatography. The relative errors were less than 6.93%? 8.81% for DES and BPA.(4) The electrochemical behaviors of 4-chlorophenol (4-CP), a highly toxic environment pollutant, were studied. It was found that the irreversible oxidation process of 4-CP involved one electron, and its oxidation peak currents increased greatly on the surface of FeOOH nanorods-modified CPE (FeOOH/CPE). The signal enhancement mechanism for 4-CP was studied using electrochemical impedance spectroscopy and chronocoulometry revealing that the prepared FeOOH nanorods effectively improve the electron transfer ability and surface adsorption efficiency of 4-CP. The influences of pH value, amount of FeOOH nanorods and accumulation time were examined. As a result, a rapid and simple electrochemical method was developed for the rapid determination of 4-CP. The linear range was from 10 to 500 nM, and the detection limit was 3.2 nM. It was used in different water samples, and the results consisted with the values that obtained by high-performance liquid chromatography.(5) The surface area of the above iron oxyhydroxide (FeOOH) nanorods is measured to be 170.34 cm2 g-1, and the pore size is about 9.04 nm, from the nitrogen sorption isotherms. The adsorbing capacity and electron transfer resistance of the bare carbon paste electrode (CPE) and FeOOH nanorods-modified CPE (FeOOH/CPE) toward tetrabromobisphenol A (TBBPA), and it was found that FeOOH nanorods effectively improve the electron transfer ability and surface adsorption efficiency of TBBPA, and the oxidation signals enhance greatly on the surface of FeOOH nanorods. Using the FeOOH nanorods as the sensing materials, a highly-sensitive and selective electrochemical sensor was developed for TBBPA. The linear range is from 1.50 to 50.00 ?g L"1, and the detection limit is 0.75 ?g L1 (1.38 nM). This new sensing system was used in different water samples, and the recovery was over the range from 96.8% to 101.6%.(6) The oxidation behaviors of dopamine (DA) and epinephrine (EP) were studied, and it was found that the morphology of CeO2 greatly influenced the response signals of DA and EP. The composite sensitive membrane constructed by CeO2 straw-like bundles with higher specific surface area possesses the most significant signal enhancement effect. The influences of pH value, accumulation potential and time, modifier amount of CeO2 samples suspension and Nafion were examined on the oxidation signals of DA and EP. Thereafter, a novel electrochemical method was established for the simultaneous detection of DA and EP in the presence of ascorbic acid and uric acid with high concentration, and the detection limit was 2.85 nM and 0.67 nM. This new sensing system was used in human serum real samples, and the recovery was over the range from 98.5% to 103.8%. |
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