Construction Of Photoassisted Dual-photoelectrode Self-powered Sensor And Applications For Microcystins Detection

Microcystin-leucine-arginine（MC-LR）and microcystin-arginine-arginine（MC-RR）are serious threats to the ecological environment and human health due to their wide distribution and high toxicity,so it is necessary to develop a sensitive,reliable,convenient and inexpensive detection method.The self-powered sensor detection method based on photo-assisted fuel cell（PFC）inherits the advantages of conventional electrochemical detection techniques.Meanwhile,it consists of only two electrodes without external power supply,which is convenient for device integration and can meet the above detection requirements.In this work,based on the principle of Fermi energy level matching,the materials of photoanode/photocathode were selected.The biospecific photocathode-based mediator-free self-powered sensor was constructed to achieve accurate detection ofMC-LR.The sensitivity ofMC-LR detection was further enhanced by using nanoenzyme-induced enzymatic biodeposition to amplify the response signal.Finally,the field detection ofMC-RR was successfully established by using sunlight instead of the instrument light source,adding internal reference electrode and employing an ordinary multimeter as the signal output device.The main research contents are as follows:1.Based on the principle of Fermi energy level matching,the PFC based self-powered sensing platform was constructed with nanoparticle-CdS-modified ZnO nanorods（CdS/ZnO NRs）as the photoanode material and electrodeposition-generated CuSCN NRs as the photocathode material.The Fermi energy level difference between the photoanode and photocathode was sufficient to drive the sensor to supply energy for its own detection in the absence of redox medium.It avoided interfering photocurrents generated by non-specific redox reactions of external electron donors（or acceptors）during the detection process,which enhanced the anti-interference capability of the sensing detection.Meanwhile,the coupling of the detection（MC-LR）and the aptamer occured on the photocathode,which avoided the false positives caused by the hole redox small molecules generated on the surface of the photoanode.By the way,it also enhanced the accuracy of the sensing detection.The constructed media-free dual-photoelectrode self-powered aptasensing detection platform about output power density(P_max)showed a good linearity in the logarithm ofMC-LR concentration in the range of 0.10 pM-10 nM with the detection limit as low as 33 fM.This method achieved the sensitive quantitative detection ofMC-LR in fish samples.2.Based on the above work,the PFC self-powered sensor combined with enzymatic reaction was constructed by using ZnO NRs as photoanode materials and nano-CuS as photocathode materials,and introducing Co₃O₄ hollow nanospheres（Co₃O₄ HNPs）with peroxidase-like activity into the MC-LR sensing system.The results show that Co₃O₄ HNPs could not only compete with photoanode for light energy,but also induce insoluble biological precipitation on the electrode surface by triggering the enzymatic reaction,thus inhibiting the electron transfer from photoanode to photocathode.This resulted in the unraveling of the double chain structure of the aptamer and the corresponding complementary chain in the presence of the target MC-LR,and then the aptamer-modified Co₃O₄ HNPs detached from the electrode surface to capture MC-LR,which made less Co₃O₄ HNPs available for enzymatic reaction on the electrode surface.Therefore,it increased the P_max of the sensor.The constructed signal amplification PFC sensing platform based on the Co₃O₄HNPs nanoenzyme-induced enzymatic reaction was constructed with a wider linear range and lower detection limit than the above work.It showed good linearity in the logarithm ofMC-LR concentration in the range of 10 fM to 10 nM,and the detection limit was as low as 3.3 fM.3.In order to meet the needs of field detection,the common multimeter was used as the electrical signal output device;and the sunlight was used to replace the instrumental light source.A PFC self-powered sensor for detecting MC-RR was constructed by selecting the photoactive materials CdS/ZnO NRs as photoanode materials and CoMoS₄ HNPs as photocathode materials that can capture sunlight and have high light energy utilization.It was shown that the quantitative detection ofMC-RR based on the signal ratio between the working electrode and the internal reference electrode,showed good linearity in the logarithm ofMC-RR concentration in the range of 1.0 pg/L to 20μg/L,and the detection limit was as low as 0.33 pg/L.By the way,it avoided the influence of environmental changes.The developed self-powered sensing device has the advantages of minitype,portability,anti-interference and sunlight drive,which can realize the field monitoring ofMC-RR in lake water.