Construction Of Photoelectrochemical Aptasensors Based On Graphitic Carbon Nitride Photoelectronic Active Materials For Antibiotic Detection

The widespread use of antibiotics around the world has led to serious pollution of soil and water,and the enhancement of antibiotic resistance caused by accumulation in organisms has posed a more and more serious threat to human health.In order to effectively track and control antibiotic pollutants,it is essential to develop rapid and efficient detection methods.Compared with other traditional determination methods,photoelectrochemical aptasensor is a novel strategy,which fully takes advantage of the merits of photocatalysis and electrochemical detection,with the strengths of high sensitivity,strong selectivity,low background signal,simple operation and moderate cost.It has been widely used in biological analysis,pollutant detection and food monitoring.For the design and development of photoelectrochemical aptasensors,it is particularly important to select suitable photoelectronic active materials,since the efficient and stable signal output is a prerequisite to ensure excellent performance.In this paper,four kinds of g-C₃N₄-based photoelectronic active materials with excellent photoelectrochemical properties were prepared by different strategies.At the same time,combined with antibiotic specific aptamer probe,four kinds of self-powered photoelectrochemical aptasensors were developed for the efficient detection of antibiotics in water.The electron transfer mechanism of photoelectronic active materials and the detection principle of the sensors were deeply studied.Meanwhile,the effects of different experimental conditions on the detection performance of the sensor were studied,and the optimum conditions for the detection of antibiotics were optimized.Finally,the potential of g-C₃N₄-based photoelectronic active materials in complex environment was discussed.The main research contents are as follows:(1)By using the strategies of morphology control,element doping and surface plasmon resonance,Au nanoparticles-decorated phosphorus-doped porous ultrathin g-C₃N₄nanosheets(Au/PCN-S)was prepared.The porous ultra-thin structure significantly increases the specific surface area of PCN-S,and greatly improves the biocompatibility and visible light absorption.Au NPs not only provides stable modification sites for aptamers,but its unique surface plasmon resonance effect further enhances the photoelectrochemical properties of the composites.The photocurrent of Au/PCN-S was significantly improved under visible light irradiation.Based on the three-electrode detection system and combined with oxytetracycline(OTC)specific aptamer,a novel self-powered photoelectrochemical aptasensor was developed.The detection range of sensor is 0.5 to 200 n M with high sensitivity and selectivity.And the provided detection limit is 0.34 n M.The proposed aptasensor also showed good reproducibility and stability.In addition,the successful application of the sensor in actual environmental samples also shows great potential for its practical application.(2)Based on g-C₃N₄nanosheet,an Ag₂Cr O₄/g-C₃N₄/GO ternary composite(CAG-30)was prepared with Z-scheme heterojunction.And an efficient self-powered photoelectrochemical aptasensor was established with chloramphenicol(CAP)specific aptamer.The experimental results show that the Z-scheme heterojunction of CAG-30 has excellent photoelectrochemical properties and significantly improves the photocurrent response.In addition,the electron transfer path in Z-scheme heterojunction is confirmed by the detection of free radical products and DFT simulation results.Due to the specific recognition of aptamer probe and CAP molecule,the selectivity and sensitivity of the sensor are significantly improved.In addition,the developed photoelectrochemical aptasensor has the advantages of wide linear range,low detection limit,high reproducibility and good stability.The effective detection range is 0.5 p M to 50 n M and the lowest detection limit is 0.29 p M.Through the detection of CAP in pig urine and river water,the practicability of the sensor is proved successfully.(3)A novel dual Z-scheme heterojunction system based on WO₃/g-C₃N₄/Mn O₂ternary composite was firstly designed and prepared.And a self-powered photoelectrochemical aptasensor for OTC detection was developed by using double electrode detection mode and OTC specific aptamer.The unique dual Z-scheme heterojunction design allows full play to the complementary properties of these three materials and ensures the high stable photocurrent output of the photoanode,which is due to its wide light absorption range and high electron-hole pairs separation efficiency.In addition,the photocathode modified with reduced graphene oxide(r GO)and Au NPs provides high conductivity and abundant aptamer binding sites,which provides excellent selective recognition and self-powered supply for the sensor by receiving electrons from the photoanode.For the detection of OTC,the sensor has a wide detection range of 1 p M-150 n M and a low detection limit of 0.1 p M.In addition,the developed photoelectrochemical aptasensor has good selectivity,reproducibility and stability,and can be used in practical samples.(4)According to the regulation of morphology and structure,a kind of 3D g-C₃N₄nanomaterial with high specific surface area and excellent photoelectrochemical properties was prepared.3D g-C₃N₄has a three-dimensional open frame porous structure,which can produce highly stable anodic current as a photoanode.At the same time,the porous N-doped Cu₂O@C material with core-shell structure was prepared by using copper-based metal-organic frame structure,which further improved the light absorption capacity of the photocathode while protecting the Cu₂O with good photoelectrochemical properties from oxidation.Through the difference of Fermi energy between the two materials,based on the double electrode detection system,a photo-fuel cell type double photosensitized self-powered photoelectrochemical aptasensor was constructed for CAP detection.The sensor can achieve good detection results in the range of CAP concentration of 0.5 p M-300 n M,and the lowest detection limit is 0.1 p M.It not only shows good selectivity,stability and repeatability,but also has good applicability to actual river water samples.