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

Atrazine（ATZ）is one of the most commonly used pesticides in the world.It is considered to be an ecologically safe and green herbicide.However,in recent years,many researches have shown that ATZ,as one of endocrine disruptors has a harmful effect on human’s reproductive,endocrine,central nervous and immune systems.Due to its persistence,high mobility and slow degradation rate,ATZ is commonly found in soil,surface water and food products.ATZ can be constantly detected in drinking water in many EU countries,where the level of ATZ has exceeded the safety limits for human health.So it is very important to develop rapid and accurate methods for determination of ATZ for protecting environmental and human health.Among many techniques for determination of ATZ,Electrochemical and photoelectrochemical techniques have attract considerable attention due to their technical simplicity,fast response,low cost and high sensitivity.Meanwhile,aptamer are employed as the recognition elements because of the merits such as excellent selectivity,strong anti-interference ability and high stability.Therefore,different biosensor platforms have been designed through combination of highly sensitive electrochemical or photoelectrochemical methods with aptamer with the specificity to its target for highly sensitivite and selective detection of ATZ.（1）A label-free electrochemical aptasensor was constructed based on Ni HCF NPs and ERGO for detection of ATZThe electrochemically reduced graphene oxide（ERGO）was obtained by reduction of the graphene oxide immobilized on glassy carbon electrode（GCE）via cyclic voltammetry（CV）technique.ERGO exhibits excellent conductivity and large surface area,which can improve the sensitivity of analytical methods.Then Ni HCF NPs was in situ deposited on the ERGO/GCE by potentiostatic electrodeposition.Ni HCF NPs were used to be as a signal probe with well-defined peaks and good stability.Subsquently,Aunanoparticles（Au NPs）were electrodeposited on Ni HCF NPs/ERGO through CV technique to anchored aptamer and further increase the stability of the electrode.Thus,a label-free electrochemical aptasensor was successfully constructed based on Ni HCF NPs and ERGO for detection of ATZ.When ATZ was added,ATZ-aptamer complexes formed on the sensing surface retarded the electron transfer of the Ni HCF NPs probe,leading to the electrochemical signal decrease.ATZ could be detected quantitatively by measuring the signal change.The designed aptasensor exhibits high sensitivity for detection of ATZ.A linear work curve was obtained in the range of 0.25-250 p M with a low detection limit of 0.1 p M.The aptasensor exhibits also perfect specificity for ATZ in the presence of diverse interferents.Meanwhile,it was successfully used to evaluate the level of ATZ in the real samples.（2）A PEC aptasensor was constructed based on Au NPs/Mo S2QDs/TiO₂ NTs nanocomposite for detection of ATZThe highly orderde vertically aligened TiO₂ NTs was fabricated on the Ti foil by in situ anodic oxidation,possessing stability and biocompatibility.The intrinsic band gap of TiO₂ limited its absorption in the visible region.Moreover,the rapid recombination of photogenerated electrons and holes greatly lowers the quantum efficiency.In this chapter,Mo S2 QDs were preprared by hydrothermal method with a narrow band gap and strong visible absorption which prepared.Then TiO₂ NTs were immersed in Mo S2 QDs solution for a few of seconds to obtain Mo S2 QDs/TiO₂ NTs composite.The composite can accelerate the separation of photogenerated charges and enhanced visible-light absorption.Au NPs were electrodeposited on Mo S2QDs/TiO₂ NTs surface to anchor aptamer and further increase the conductivity of the sensing interface.Thus,a photoelectrochemical aptasensor was developed based on Au NPs/Mo S2 QDs/TiO₂ NTs.In addition of ATZ,ATZ-aptamer complexes with poor conductivity on the aptasensor surface were formed by the binding of aptmenr to ATZ,which increased the steric hinderance of the diffusion of the electron from the solution to thesensing interface,leading to the photocurrent decreased.The PEC aptasensor shows superior analytical performance for ATZ.The proposed PEC aptasensor was exploited to detect ATZ,and a good linear relationship between PEC current and ATZ concentration was obtained in the range of 2.5to 500 p M with the detection limit of 1.0 p M.This PEC aptasensor applied to evaluate the level of ATZ in practical water samples,which would be expected to be an important analytical method in environmental monitoring.（3）A PEC aptasensor was constructed based on Bi OI/TiO₂ nanocomposite for detection of ATZThe highly orderde vertically aligened TiO₂ NTs was fabricated on the Ti foil by in situ anodic oxidation.Bi OI was deposited on the surface of TiO₂ NTs by a hydrothermal method.The combination of Bi OI and TiO₂ NTs could form p-n junction.The energy bands between the two nanomaterials are well matched,and they can enhance the visible light absorption and improve the separation of photogenerated charges.Aptamer with-NH2 was anchored on Bi OI/TiO₂ NTs by covalently bonding using glutaraldehyde as a linker.The PEC aptasensor was fabricated based on Bi OI-TiO₂ NTs composite for detection of ATZ.When ATZ was added,ATZ-aptamer complexes formed on the sensing surface retarded the electron transfer,leading to the photocurrent signal decrease.The design PEC aptasensor exhibits superior analytical performance for detection of ATZ.A linear work curve was obtained in the range of 1.0-600 p M with a detection limit of 0.5p M.The designed PEC aptasensor exhibits good selectivity for ATZ,and can resist the interference in the complicated environment.Thus,the PEC aptasensor was successfully applied to be determine ATZ in environmental samples.