Synthesis Of Carbon-based Nanocomposites And Its Application In Amino Acids Electrochemical Sensors

Amino acids are essential building blocks of biological molecules and they have aclose relationship to life activities of biology, so it is very important to deminineamino acids with high-sensitivity and high-effectivity. Electrochemical sensor hasbeen extensively applied in reliable detection of amino acids due to its simplity,low-cost and high-selectivity. In the theses, a series of electrochemical sensors foramino acids detection were developed based on Fe₃O₄-graphene oxide （Fe₃O₄-GO）nanocomposites modified glassy carbon electrode （GCE）, cobalt nanoparticles （CoNPs） electrodeposited on graphene modified GCE and Co NPs doped electrospuncarbon nanofibers （CNFs）. These works mainly covered the following areas:1. In the first part, the Fe₃O₄-GO nanocomposites were prepared by a chemicalco-precipitation. The results showed that ultrafine Fe₃O₄NPs was prepared anddensely assembled on GO nanosheets. The Fe₃O₄-GO exhibits a large surface area andhigh catalysis towards the oxidation of cysteine and N-acetyl cysteine, which could beused for cysteine and N-acetyl cysteine sensing. The excellent catalytic activity, highsensitivity and good stability made such Fe₃O₄-GO nanocomposites to be promisingnanomaterials for constructing nonenzymatic sensors.2. In the second part, three-dimensional （3D） Co NPs networks were prepared bydirectly electrodepositing Co NPs on graphene/GCE and accordingly a novel aminoacids sensor was developed. The resulted sensor displayed a good electrocatalyticactivity for the oxidation of cysteine and N-acetyl cysteine and with a high sensitivityand well stability. The good elecctroactalytic activity might be ascribed to the existingof graphene which provided a large surface area （both surfaces） to increase thequantity of Co NPs and to reduce the size of the electrodeposited Co NPs. The largesurface-to-volume ratio of the small Co NPs produced a large total surface area thatprovided more chances to contact amino acids, which improved the catalyticperformance of the sensor.3. The third part was focused on the syntheses of Co NPs doped electrospunCNFs and their application as a novel amino acids sensor. Scanning electronmicroscope images showed that a large number of Co NPs were formed and disperseduniformly on the CNFs or embedded in the CNFs matrix to produce a3D structure.The electrochemical results indicated that the Co NPs-CNFs showed a good electrocatalytic activity towards the oxidation of cysteine and N-acetyl cysteine, andthe current response of the Co NPs-CNFs/GCE was sensitive to pH of the electrolytesolution. The peak current was quite large at pH13.0but greatly suppressed at pH7.5.Therefore the electrode could realize pH-controlled oxidation of amino acids.