Research On A New Method Of Photoelectrical Signal Amplification And Biosensing Based On Nanometerials

Photoelectric chemistry（PEC）analysis is a new detection technology emerging in recent years,which plays an important role in the development of analytical methods.So far,photoelectric chemistry technology has attracted much attention due to its advantages of low detection background signal,low operation requirements for researchers and high sensitivity of detection system.PEC system is a mixture of PV and EC.Light is used as excitation source and electrical current is the detection signal,which greatly reduces the background signal.The light source excites the photoactive material to generate photogenerated electrons,which transfer to the electrode surface to present photocurrent,realizing the conversion of light energy to electric energy.The high efficiency of the PEC process is attributed to the directional migration and rapid conduction of photogenerated electrons by the external circuit,which effectively inhibits the electron-hole pair recombination.So far,various PEC biosensors have been developed for different targets,including bacteria,protein,nucleic acid,organic small molecule,metal ions,etc.This work mainly analyzes the photoelectric properties of various photoactive materials and combines with nucleic acid amplification technology to achieve trace detection of cancer markers and environmental pollutants,mainly carrying out the following three aspects of work:1.Based on the photoelectric mechanism of 3D CdSe QDs-DNA NR sensitized mesoporous SnO₂nanoflowers,an ultra-sensitive PEC and ECL biosensor was designed,and the cyclic amplification of the target was realized by using ExoⅢtriggered bipedal DNA walker-cascade amplification strategy.The photosensitive CdSe QDs have well-matched band-edge energy level with the mesoporous SnO₂nanoflowers.The highly efficient photosensitive 3D CdSe QDs-DNA reticulated nanomaterials displayed much high stability and controllability.Furthermore,the target-induced biped DNA walker-cascade amplification strategy can generate a large amount of output DNA,which was used to link numerous 3D CdSe QDs-DNA nanonetwork signal probes to generate greatly amplified ECL and PEC signals for sensitive detection of HIV.This method provides a versatile biosensing strategy using the 3D CdSe QDs DNA sensitization probes for ultra-sensitive detection of multiple biomolecules,which has promising application for the early diagnosis of disease.2.A phenomenon of polarity-switching-photocurrent of AgInS₂ quantum dots（QDs）-DNA nanowires reversing nitrogen-doped porous carbon-Zn O（NPC-Zn O）nanopolyhedra was found for the first time,and a versatile photoelectrochemical（PEC）biosensor with reversed signal was innovatively proposed for dual-target detection.NPC-Zn O is a photoactive material with excellent PEC properties,while AgInS₂ QDs as a photosensitive material match NPC-Zn O in energy level,which not only promotes the transfer of photogenerated carriers but also switches the direction of PEC current.When target Hg²⁺induced-cyclic amplification process generated abundant RDNA,the DNA nanowires signal probe with plenty of QDs were linked to the NPC-Zn O/electrode by RDNA,generating greatly amplified polarity-reversed photocurrent for signal“ON”detection of Hg²⁺.After specific binding of target（aflatoxin B1,AFB1）to its aptamer,the signal probes of AIS QDs-DNA nanowires are released,realizing signal“OFF”assay of AFB1.The proposed new PEC biosensor effectively avoid both false positive and negative phenomena in assay process.3.Based on the experimental phenomenon of AIS/ZnS QDs nanosignal probe sensitizing WSe₂nanoseed,a novel PEC sensor platform is proposed to realize the ultra-sensitive detection of“on-off”signals of human tumor necrosis factor TNF-αand methylase Dam MTase.The WSe₂nanoflower background signal is small,which is an excellent substrate for PEC sensor platform.As a photosensitive material,AIS/ZnS QDs matches the WSe₂level,thus promoting the transfer of photogenerated electrons and obtaining higher photocurrent signal.In the presence of target TNF-α,the combination of target TNF-αand aptamer Apt 2 can connect AIS/ZnS QDs loaded signal probe Apt-SP to the electrode to generate signal on state and realize the detection of TNF-α.Subsequently,the target Dam MTase induces hairpin H_Dammethylation and is cut by endonuclease Dpn I,which results in AIS/ZnS QDs shedding on Apt-SP surface and signal off state,thus realizing dual-target detection.The biosensor has the advantages of low detection limit and wide detection range,and provides prospects for clinical diagnosis.