Construction Of Graphene-based Photoelectrochemical Sensors And Their Applications For Antibiotic Detection

Residues caused by the abuse of antibiotics will lead to the resistance of bacteria and harm to human health through the food chain.Therefore,it is urgent to explore a sensitive and efficient even with multiple detection capabilities method of antibiotic detection.Photoelectrochemical（PEC）aptamer sensing technology has been widely used in the field of analysis and detection due to its advantages of low cost,fast response,high sensitivity,high affinity and high specificity.Highly active photosensitive materials can provide a good background for the construction of sensitive PEC aptasensor.The introduction of use novel sensing strategy is of great significance to construct high PEC performance sensor with multiplex detection capability.Graphene-based materials have good electrical conductivity,stable physical and chemical properties and large specific surface area,which can be used to modify semiconductor materials to prepare functional materials with high PEC activity.In this paper,three kinds of graphene-based functional composites with excellent PEC property were prepared by introducing defect engineering and ion doping.Subsequently,three PEC aptasensors were constructed by modifying biometric elements.The bias potential controlling strategy realize the specific and sensitive detection of one and two antibiotics,and the sensors was successfully used for the detection in food samples.Specific research contents are as follows:1.Reduced graphene oxide supported Bi³⁺doped black titanium dioxide composites(Bi³⁺/B-Ti O₂/r GO)were prepared by solvothermal-calcination method.The PEC performance of Bi³⁺/B-Ti O₂/r GO was tested and it was found that the composites had stable photocurrent response.Compared with Ti O₂,B-Ti O₂ and B-Ti O₂/r GO,the PEC response of prepared Bi³⁺/B-Ti O₂/r GO under visible light is increased by 40.0,4.0and 2.4 times,respectively.Compared with Ti O₂,the photocurrent of B-Ti O₂ enhanced due to the existence of oxygen vacancy（OVs）,while the photocurrent of Bi³⁺/B-Ti O₂/r GO enhanced due to the increase of OVs and the increase of charge transfer rate.Meanwhile,r GO inhibited the aggregation of B-Ti O₂ nanoparticles and reduced the rapid recombination of photoexcited electron-hole pairs.The electrons in the Bi³⁺6s orbital were excited to the Ti⁴⁺3d orbital,which reduced the band gap and promoted the effective separation of photogenerated carriers.Bi³⁺/B-Ti O₂/r GO was combined with specific aptamer to construct a selective and sensitive PEC aptasensor for tobramycin（TOB）detection.The sensor achieved rapid response over a wide linear range（0.001～50 ng/m L）with a low detection limit（0.33 pg/m L）.The results indicated that the prepared photoactive material Bi³⁺/B-Ti O₂/r GO has a high application potential in PEC sensors.2.Three-dimensional nitrogen doped graphene-loaded Zn In₂S₄（Zn In₂S₄/3DNG）functional material was prepared by a simple one-step solvothermal method.Since the porous structure of 3DNG promoted the transfer rate of photogenerated carriers,the photocurrent of Zn In₂S₄/3DNG was significantly higher than that of Zn In₂S₄,and the absorption of visible light enhanced.Based on Zn In₂S₄/3DNG,a PEC aptasensor for the detection of oxytetracycline（OTC）was constructed,which expressed high sensitivity and selectivity.The high photocurrent of the composite and the construction of“signal of”mode expand the detection range of OTC,as well as achieved rapid reaction in the linear range of 0.001 nmol/L to 5000 nmol/L,with a low detection limit（0.33 pmol/L）.The constructed aptasensor has also been successfully applied to the detection of OTC in chicken.3.Copper indium disulfide decorated with 3DMG（Cu In S₂/3DMG）composite with cathodic current was prepared by solvothermal method.Combining with Bi³⁺/B-Ti O₂/r GO nanocomposite from the first work,which could generate anodic current,a bias potential-controlled PEC aptasensor was prepared for simultaneous detection of ENR and CIP.Based on the potentiometric-resolved photocurrents,the cathodic photocurrent generated by Cu In S₂/3DNG and the anodic photocurrent generated by Bi³⁺/B-Ti O₂/r GO could be clearly distinguished without interfering with each other;After modifying specific aptamers,the dual detection of ENR and CIP was realized.The PEC sensor showed a good linear relationship between the photocurrent and logarithm of concentration in the detection range of 0.01～10000 ng/m L to ENR and0.01～1000 ng/m L to CIP,with the detection limit of 3.3 pg/m L.In addition,the dual detection of ENR and CIP in milk samples was achieved,indicating the potential application of the PEC aptasensor in multiple detection of antibiotics in food.