Research On The Construction And Application Of A New Type Of Photoelectrochemical Aptamer Sensor

Photoelectrochemical?PEC?aptasensor has become a newly photochemical biosensor platform which combines the high sensitivity of PEC sensor with the specific recognition of aptamer sensor.On the one hand,photogenerated electrons produced by photochromics transfer to the electrode that results in generating photocurrent under the illumination.On the other hand,aptamers are immobilized onto the transducer surface for the subsequent target recognition and binding.Due to the advantage of low background,high sensitivity,high selectivity,easy operation and low cost,PEC aptasensor has capacious development foreground for detecting target which has been applied in biological analysis,food detection,environmental protection and other fields.Herein,this paper has constructed different PEC aptasensor based on different materials such as titanium dioxide,semiconductor and tungsten disulfide and so on with different aptamer fixed methods.The main works are as follows:1.A visible-light driven photoelectrochemical?PEC?aptasensor was developed for chloramphenicol?CAP?detection based on trivalent Eu-doped CdS quantum dots-sensitized TiO₂ nanorod arrays(CdS:Eu³⁺QDs/TiO₂ NRAs).TiO₂ NRAs grew on the ITO electrode via hydrothermal synthesis which possess many advantages such as high stability,large surface area,good biocompatibility,nontoxicity,low cost.Carboxyl functionalized Eu³⁺-doped CdS QDs was synthetized via simple co-precipitation method and used as sensitizer to modify TiO₂ nanorod arrays via strong coordination interactions between TiO₂ and carboxyl groups.A structure of waterfall band gradient was established result from lower band gap of CdS?2.4eV?than TiO₂?3.2 eV?,which improved photo-to-current conversion efficiency.Moreover,the introduction of Eu³⁺ions can promote the charge transformation and utilization,thus resulting in a further increasing of photocurrent.Aptamers of CAP were immobilized on the electrode via the amidation reaction.Under optimal conditions,the aptasensor showed a linear PEC response to CAP concentration in the range of 1.0pM-3.0 nM with a detection limit of 0.36 pM.At the meantime,the aptasensor showed good selectivity and stability.The PEC aptasensor was applied to the determination of CAP in spiked milk samples with satisfactory results.The PEC aptasensor provides a fast,simple,convenient strategy.2.A novel photoelectrochemical aptasensor platform for the detection of kanamycin based on the WS₂/CdS/ZnS nanocomposites was established.Firstly,the WS₂ nanosheets were deposited onto ITO substrate by electrophoretic method.CdS nanoparticles were grown via facile successive ion layer absorption and reaction?SILAR?method.Subsequently,the ZnS shell coverd onto CdS nanoparticles by the same method.The ZnS shell,which serves as a passivation layer,could effectively increase the photocurrent by prohibiting the formation of surface defects on CdS QDs and inhibiting the electron recombination.WS₂/CdS/ZnS nanocomposites serve as a base of the PEC aptasensor which has advantages of high specific surface area and good photoelectric effect.Aptamer attached to the electrode by Zn-S bonding and the kanamycin would be oxidized upon capture by aptamer at high potential.Under optimal conditions,the aptasensor demonstrated a linear PEC response to kanamycin concentration in the range of 0.1 pM-5 nM with a detection limit of 0.05 pM?S/N=3?.With good selectivity and sensitivity,the PEC aptasensor was applied to the determination of kanamycin in spiked milk samples and fish with satisfactory results,suggesting that the WS₂/CdS/ZnS on ITO photoelectrode has a promising application in constructing PEC sensor platform.