| With the rapid development of society, environmental health has become one of the most challenging issues in China. Thus, quantitative and rapid determinations of trace pollutants in enviromental and foodstuff samples, and comprehensive analyses of corresponding biomarkers in biological samples are essential to evaluate the effects of environmental factors on human health.Electrochemical sensors possess many unique properties, such as high sensitivity, simple operation, low cost, less samples required and easy miniaturization and so on. Thus, they have been widely used in the fields of food and drug analysis, environmental monitoring, clinical diagnosis, defence and security. Moreover, the development of nanotechnology, especially the spring up of functional nano-materials and nano-composites has injected new vitality to the development of electrochemical sensors. In this work, several nano-materials had been successfully used for the fabrication of electrochemical sensors utilized in the fields of food analysis, environmental monitoring and medical pathology studies. The main results are summarized as follows:(1) An efficient approach for the fabrication of pesticide biosensors by amino functionalized carbon nanotubes was introduced. Compared with the pristine,-COOH and-OH decorated CNTs, a larger amount of enzymes were adsorbed on the surface of CNT-NH2with a favorable orientation and the best amperometric response of acetylthiocholine chloride (ATCh) was obtained on the AChE/CNT-NH2/GC electrode. Furthermore, the biosensor modified with CNT-NH2showed a high affinity to ATCh and could catalyze the hydrolysis of ATCh with an apparent Michaelis-Menten constant (Km) value of67.4μM Using paraoxon as a model compound, the biosensor achieved wide linear ranges from0.2nM to1nM and1nM to30nM, and a low detection limit of0.08nM. Moreover, the biosensor had also been successfully employed for the determination of low concentrations of pesticides in real vegetable samples.(2) A facile and sensitive choline biosensor was successfully developed based on nano-manganese dioxide (nano-MnO2), which was synthesized in-situ at the surface of the glassy carbon electrode by one-step electrodeposition. The synthesized nano-MnO2had highly sponge-like nanostructures, which were good for electrons and mass transporting when used as electrocatalysts. Moreover, nano-MnC>2had shown good hydrophilicity, which could facilitate the immobilization of enzyme and prepare a suitable micro-environment for enzyme-substrate interaction. Upon optimized conditions, a wide linear range (8.0μM-1.0mM) and a low detection limit (5.0μM) were obtained. Besides, the biosensor was successfully employed to detect choline in real samples, providing a promising alternative for the practical application.(3) A hexachlorobenzene electrochemical sensor based on nitrogen doped graphene (N-rG) and chitosan were fabricated by layer-by-layer assembly technique. In this system, the nitrogen doped reduced graphene provided good electrocatalytic activity for the reduction of hexachlorobenzene. Besides, graphene had shown good adsorption affinity to hexachlorobenzene due to the dominant role of π-π stacking interaction. Upon optimized conditions, the self-assembly electrode possessed an excellent sensing performance for the detection of hexachlorobenzene, with a wide linear range from3μg/L to10mg/L, and a low detection limit of1.72μg/L. Moreover, the sensor had been successfully applied for the detection of hexachlorobenzene in practical water samples.(4) A H2O2sensor based on Pt-Au/rGSs/GCE was fabricated by cyclic voltammetry method using the surfactant Brij58as a soft template. Owing to the synergetic effects of the bimetallic NPs and rGSs, the amperometric H2O2sensor had shown high sensitivity and could operate at a low potential of0V. Under this circumstance, not only the common anodic interferences induced from ascorbic acid, uric acid and dopamine, but also the cathodic interference induced from endogenous O2could be effectively avoided. Therefore, the whole experiment could be carried out without removing oxygen. Upon optimized conditions, wide linear ranges (1μM-1.78mM and1.78mM-16.8mM) and a low detection limit (0.31μM) were obtained. Besides, with rat pheochromocytoma cells as model, the proposed sensor had been successfully used in the detection of H2O2released from the cancer cells, providing a promising alternative for H2O2monitoring in the fields of physiology, pathology and diagnosis.
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