| Currently, the worldwide production of phenolic endocrine disruptors became very large, because of widespread applications and stable performance. However, relative researches have shown that phenolic endocrine disruptors are estrogenic and are listed as one of the most widely distribution of endocrine disrupting chemicals (EDCs). Long-term exposure of humans and wild animals in an environment containing phenolic endocrine disruptors, it will induce cancer, deformities, the abnormalities of reproductive system and other diseases. Therefore, it is very important to develop a sensitive, fast and accurate method for the determination of phenolic endocrine disruptors.In this study, a series of electrochemical sensors based on nanomaterials, molecularly imprinted polymers (MIPs), sol-gel and avidin-biotin system for the detection of bisphenol A (BPA), 4-nonylphenol (4-NP) and octylphenol (OP) were fabricated. The experimental results showed that the proposed sensors exhibited high selectivity, excellent stability, good repeatability, a wide linear range, lower limit of detection and successful application in real samples.The main contents of this work were as follows:1. A novel bisphenol A biosensor based on amperometric detection has been developed using molecularly imprinted polymers and gold nanoparticles (AuNPs). The sensitive layer was prepared by electropolymerization of 2-aminothiophenol on a gold nanoparticles modified glassy carbon electrode (AuNPs-GCE) in the presence of bisphenol A as a template. Cyclic voltammetry (CV) and amperometric measurements were used to monitor the process of electropolymerization. The properties of the layer were studied in the presence of Fe(CN)63-/Fe(CN)64- redox couples and also by the use of amperometric measurements. The linear response range of the sensor was between 8.0×10-6 to 6.0×10-2mol L-1, with a detection limit of 1.38×10-7mol L-1 (S/N=3). The proposed molecularly imprinted polymers sensor exhibited good selectivity for bisphenol A. The stability and repeatability of the molecularly imprinted polymers senor were all found to be satisfactory. The results from sample analysis confirmed the applicability of the molecularly imprinted polymers sensor to quantitative analysis.2. A novel electrochemical imprinted sensor for sensitive and convenient determination of bisphenol A was developed. Multi-walled carbon nanotubes (MWCNTs) and gold nanoparticles were introduced for the enhancement of electronic transmission and sensitivity. Thin film of molecularly imprinted sol-gel polymers with specific binding sites for bisphenol A was cast on gold electrode by electrochemical deposition. The resulting composites were characterized by cyclic voltammetry and UV-visible absorption spectrum. Rebinding experiments were carried out to determine the specific binding capacity and selective recognition of the sensor. Rebinding experiments were carried out to determine the specific binding capacity and selective recognition of the sensor. The linear range was from 1.13×10-7 to 8.21×10-3mol L-1, with the limit of detection of 3.6×10-9mol L-1 (S/N=3). The imprinted sensor was successfully tested to detect bisphenol A in real samples.3. A novel electrochemical sensor for sensitive and fast determination of 4-nonylphenol was developed. Titanium oxide (TiO2) nanoparticles and gold nanoparticles were introduced for the enhancement of electron conduction and sensitivity. 4-nonylphenol-imprinted functionalized gold nanoparticles composites with specific binding sites for 4-nonylphenol was modified on electrode. The resulting electrodes were characterized by cyclic voltammetry. Rebinding experiments were carried out to determine the specific binding capacity and selective recognition. The linear range was over the range from 4.80×10-4 to 9.50×10-7mol L-1, with the detection limit of 3.20×10-7mol L-1 (S/N=3). The sensor was successfully employed to detect 4-nonylphenol in real samples.4. We introduced molecularly imprinted polymers, functionalized gold nanoparticles and avidin-biotin to fabricate a biosensor for the detection of octylphenol. We chose octylphenol, 4-aminothiophenol and thioglycolic acid as the template molecule, functional monomer and stabilizer, respectively. These substances were used to form imprinted functionalized gold nanoparticles composites with gold nanoparticles. The octylphenol-imprinted functionalized gold nanoparticles composites were modified on the electrode through the biotin-avidin system. Strong affinity between avidin and biotin will increase the stability of the sensor. The linear range for octylphenol concentrations was from 9.55×10-4 to 5.00×10-7mol L-1 with the limit of detection of 1.40×10-7mol L-1. This electrochemical biosensor showed good stability, repeatability and selectivity. The sensor was successfully applied to the detection of real samples. The recovery study of octylphenol in real samples gave values from 93.5 to 96%, which confirmed that the sensor had a high accuracy.5. A novel bisphenol A electrochemical sensor based on molecularly imprinted polymers and multi-walled carbon nanotubes-cobalt phthalocyanine (CoPc) composites has been developed. The experiment of cyclic voltammetry was used for real-time monitoring of the construction process of the sensor. Meanwhile, UV-visible absorption spectrum indicated that the preperation effect of molecularly imprinted polymers and the extraction of template molecules were very satisfactory. The experimental results showed that molecularly imprinted polymers and multi-walled carbon nanotubes-cobalt phthalocyanine composites greatly improved the selectivity and the current response of the sensor, respectively. The linear response range was between 1.12×10-7 to 1.34×10-3mol L-1, with a detection limit of 3.4×10-9mol L-1 (S/N=3). The proposed sensor exhibited high selectivity, excellent stability and good repeatability. The sensor was successfully employed to detect BPA in pure water and milk samples. |
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