Constrution Of Carbon Nitride-based Photoelectrochemical Immunosensor For The Detection Of Virus

The spread of pathogenic viruses has caused serious damage to public health.It is significant to design fast,low-cost and efficient analysis technology to realize rapid and efficient detection of viruses,as well as early warning and treatment of diseases.Photoelectrochemical（PEC）immunosensor is a fast and simple biological detection method,which plays an important role with high sensitivity and easy miniaturization of equipment.It is significant to develop virus detection technology based on PEC method.The core of improving the sensitivity of PEC sensing is the construction of high-efficiency photoelectric active materials.Due to its excellent chemical stability and unique electronic band structure,polymeric carbon nitride（CN）,as a low-cost and stable photoelectric active material,has attracted wide attention in the field of PEC sensing.However,the application of bulk CN is limited due to its slow electron transfer rate,high photogenerated electron-hole recombination rate and low solar energy utilization efficiency.Therefore,this work mainly designs a series of CN-based materials with enhanced PEC performance from three aspects of enhancing the electron transfer rate,broadening the light absorption range and improving the carrier separation efficiency,and successfully constructs PEC immunosensing platforms for the highly sensitive detection of different pathogenic virus proteins.Deeply studying charge transfer and sensor detection mechanisms of carbon nitride materials provide an effective way for CN materials to enhance their PEC properties and broaden their applications in the field of PEC analysis.The specific research contents are as follows:（1）Mn（Ⅱ）modified carbon nitride photoelectric active material（Mn/CN）was prepared by high-temperature thermal polymerization.The atomic size of Mn was introduced into the CN to form an impurity energy level,and the band gap of Mn/CN becomes narrow,which makes the photogenerated electron-hole pair easy to be excited,improves the electron transfer ability,and enhances the PEC performance of Mn/CN,thus improving the detection sensitivity.The introduction of nanobody（Nb）with small molecular weight,stable structure,and high affinity has improved the selectivity of the sensor.A PEC immunosensor based on Mn/CN and Nb was constructed to detect the spike protein of novel coronavirus efficiently.The sensor showed a wide detection range(75 fg m L^–1～150 pg m L^–1),a low detection limit(1.22 fg m L^–1),excellent sensitivity,high selectivity and reproducibility when detecting spike protein.The sensor is of great significance for the sensitive detection of new coronavirus SARS-Co V-2.（2）Although the PEC performance of CN based materials has been enhanced through Mn modification,the absorption ability of CN based materials in the visible region is still weak.To enhance the visible light absorption ability of CN materials,an organic dye Co-Corrole sensitized carbon nitride（Co-Corrole/CN）material was prepared by the mechanochemical synthesis.The introduction of Co-Corrole enhances the visible light utilization of CN and promotes the transport and separation of its carriers on the surface of CN,thus improving the PEC performance of Co-Corrole/CN.Considering that norovirus is the most common pathogen of gastroenteritis and foodborne diseases in children,its high infectivity and pathogenicity are harmful to human beings.A PEC immunosensor based on Co-Corrole/CN with high PEC performance was constructed to detect norovirus capsid protein.This sensor had a wide detection range(750 fg m L^–1～150 ng m L^–1),a low detection limit(750 fg m L^–1),good stability and repeatability,and good accuracy in the detection of actual clinical samples.（3）Based on the advantages of self-powered PEC sensors,they do not require external power during the entire detection process,are simple in configuration,and flexible in operation.Carbon-rich carbon nitride（C-CN）photoelectroactive materials were synthesized by self-assembly and high-temperature copolymerization of locust bean gum biomass as a carbon source with melamine.By replacing the edge N atoms in the tris-triazine ring with C atoms,the band structure of CN is regulated,expanding the light absorption range of C-CN,and achieving efficient separation and migration of photogenerated carriers,thereby improving the PEC performance of C-CN.A membraneless free self-powered PEC immunosensor with C-CN as the photoanode and Pt/C as the cathode was designed to detect norovirus capsid protein.This sensor had a wide detection range(15 fg m L^–1～75 pg m L^–1).Compared with the Co-Corrole/CN-based PEC immunosensor,the sensor had a lower detection limit(5 fg m L^–1),good stability and repeatability,and showed good accuracy in the detection of actual clinical samples.