The Electrochemical And Photoelectrochemical Sensor Based On Nucleic Acid Aptamer For Polychlorinated Biphenyls Determination

Polychlorinated biphenyls?PCBs?are a kind of persistent pollutants with low concentration in the environment.Due to their good stability,poor degradation,biological accumulation and the toxicity of PCBs has been accumulated and spreaded in the environment,which cause a serious threat on the environment and human health.Therefore,it is great significance to the development of a reliable and sensitive method to detect PCBs.Electrochemical and photoelectrochemical analysis methods have the advantages of high sensitivity,simple experimental instruments,low cost and online real-time detection.At present,biosensing technology based on electrochemical and photoelectrochemical analysis has shown a wide application prospect in the field of environmental analysis.So,it has been attracted much attention about the research.Here,the recognition element is one of the important components in biosensor,such as antibody,aptamer so on.The aptamer is used as the recognition element,which can achieve the specific recognition of the target.with high affinity and specific recognition ability,it can play an anti-interference role in the complex system.In this paper,a single PCBs aptamer is used as the recognition element,it was modified in varies nanomaterials to construct some electrochemical and photoelectrochemical aptamer sensor sensing interfaces to detect PCBs.Moreover,PCB77 and PCB72 were used to the target.This thesis includes the following research contents:?1?An electrochemical aptasensor was constructed base on NiHCF NPs-rGO hybrid nanomaterials for detecting of PCB77NiHCF NPs was co-precipitated in situ on the rGO surface.The NiHCF NPs-rGO hybrid nanomaterials with the size of 5 nm NiHCF NPs were first synthesized.In the hybrid materials,rGO with high specific surface area and good conductivity can provide more space for the load of NiHCF NPs,and it improves the conductivity of the compounds.NiHCF NPs can be used as a signal probe,which shows a great peak shape,reversible ability and good stability.Here,the PCB77 aptamer is anchored on the NiHCF NPs-rGO hybrid materials by the covalent bond reaction.A lable-free electrochemical aptasensor was constructed for the detection of PCB77 and has a good analytical performance.The measured current and PCB77 concentration displays a good linear response range from 1.0 to 100.0 ng/L,and the low detection limit is 0.22 ng/L.Meanwhile,aptasensor has a good selectivity because the specificity and high affinity of aptamer to PCB77.In addition,the sensor can highly sensitive and selectived detect PCB77 in actual environment.?2?A photoelectrochemistry aptasensor was constructed based on CDs/Ti O2 nano-composites for detection of PCB77 with the help of Exo-IFirstly,carbon quantum dots with excellent dispersion and stability were prepared by electrochemical electrolysis.After,Ti O2 nanorods were prepared on FTO electrode by hydrothermal method.CDs was deposited on Ti O2 NRs by electrochemical deposition,so CDs/Ti O2 NRs/FTO was prepared.In this way,the visible light absorption capacity of Ti O2 NRs was expanded,and the recombination rate of photogenerated electron hole pairs was reduced.Then,the complementary strand DNA was anchored on the surface of CDs/Ti O2 NRs/FTO by cross-linking agent,and then the aptamer was hybridized with the base complementary pairing principle.The aptamer was fixed on the surface of the composite electrode,and the photochemical aptasensor was prepared based on CDs/Ti O2 NRs/FTO.When PCB77 is added,the specific effect of the aptamer on PCB77 is much greater than the synergistic effect of hybridization with complementary DNA,resulting in the separation of the aptamer from the electrode surface and the increase in photocurrent.At this time,the exonuclease I present in the electrolyte solution cleaves the aptamer-PCB77 complex in the solution to release the PCB77.When the cycle participates in the recognition reaction,the photocurrent further increases to achieve signal amplification.Thus,photoelectrochemistry aptasensor can realize highly sensitive and highly selective quantitative detection of PCB77,with a linear range of 0.003-3 ng/L and a detection limit of 0.33pg/L.?3?A photochemical aptasensor was constructed based on Ti-C₃N₄/Zn O NRs for detection of PCB72First,Ti-C₃N₄ was synthesized by calcination.After,Zn O nanorods were synthesized on FTO electrode by preparing seed layer.The Ti-C₃N₄ /Zn O NRs/FTO nanocomposite was synthesized by hydrothermal method to expand the visible light absorption capacity of Zn O NRs,and the recombination rate of photoelectron hole pairs is also reduced.The aptamer was modified to the surface of Ti-C₃N₄/Zn O NRs/FTO by cross-linking agent,the photochemical aptasensor was prepared based on Ti-C₃N₄/Zn O NRs/FTO.The aptasensor showed good analytical performance for the detection of PCB72,with a linear range of 1-500 ng/L and a detection limit of 0.21ng/L.