Research On Photoelectrochemical Sensing Mechanism And Application Based On Bismuth/Carbon-based Composites

Since the reform and opening up,the rapid economic development has improved the people’s living standards,and the consideration of food nutrition has become increasingly important.At the same time,health problems caused by food and drug safety and diseases caused by people’s behaviors and lifestyles are also on the rise.In the modern food industry,the status of antioxidants and antibiotics as"stars"of food additives is also becoming more and more prominent.Therefore,the scientific use of antioxidants and antibiotics is particularly important for human health,and the importance of monitoring and controlling antioxidants and antibiotic content in food is self-evident.In view of this situation,two composite nanosystems based on bismuth-based materials and carbon-based materials were designed and synthesized,and two label-free photoelectrochemical（PEC）sensors were successfully constructed to selectively detect and quantify ascorbic acid and tetracycline in food.The specific research content is as follows:1.Ascorbic acid（AA）,commonly known as vitamin C,is one of the most common biological small molecules in the human body and is an essential micronutrient.In this paper,a sensitive and selective PEC sensor based on a Z-scheme Bi₂S₃/NGQDs heterojunction was successfully constructed by a simple hydrothermal process for the detection of AA,and various characterization techniques were used to study the microstructure and components.The separation of photogenerated carriers is facilitated by the introduction of nitrogen doped graphene quantum dots（NGQDs）with Bi₂S₃ nanorods to form a Z-scheme heterojunction（Bi₂S₃/NGQDs）,which was used as efficient photoactive species.The photocurrent of the Bi₂S₃/NGQDs-based sensor is significantly increased in the presence of AA,and the sensor still shows excellent selectivity and stability for the detection of AA in the presence of other antioxidants and small molecule interference.In the process of AA detection,the prepared PEC sensor achieved a wide linear range of 0.1μM-5μM and 5μM-1380μM with a detection limit of 36 n M.At the same time,the possible mechanism of Bi₂S₃/NGQDs to enhance the photoactivity and selective detection of AA was also investigated.The proposed PEC sensor realized the determination of AA in real red peppers and commercially available vitamin C tablet samples.2.Among various antibiotics,the broad-spectrum antibiotic tetracycline（TC）has become one of the most widely used antibiotics in the treatment of animal and human infectious diseases due to its low cost and superior effective antibacterial properties.Unfortunately,after the abuse and release of tetracycline into the environment,it causes it to enter rivers,lakes and even soil,and then be absorbed by plants and animals along the biological chain,and eventually accumulate in the human body,seriously affecting human health.In this paper,a simple low-cost label-free PEC biosensing platform based on red blood cell shaped Bi VO₄ modified g-C₃N₄ was designed for tetracycline detection under room temperature.The prepared g-C₃N₄/Bi VO₄ heterojunction not only demonstrated a high surface area,excellent physicochemical stability and favorable PEC activity but also can be employed as nanostructure support for aptamers to construct a visible-light-driven PEC aptasensor due to richπ-πaccumulation sites.More importantly,the proposed PEC aptasensor showed a favorable linear toward tetracycline in the range from 5 n M to 200 n M with a detection limit of 1.6 n M,which well covered the Food Standards Testing requirements.Practical food sample analysis further revealed the accuracy and feasibility of the g-C₃N₄/Bi VO₄ heterostructure based PEC platform.It is expected that such a label-free and cost-effective PEC strategy should act as a promising candidate for TC determination in food quality control and supervision.