Application Of Two-Dimensional MXene In Photoelectric Biosensor

Photoelectrochemical（PEC）sensing is an advanced platform for fast and accurate monitoring of target compounds because of its high signal-to-noise ratio,fast response and low background noise.According to the transmission pathway of photogenerated electrons,the PEC biosensor is divided into three parts,namely,the generation of excited electrons in PEC active materials,the introduction of special materials to form new electron transfer pathways,and the separation of excited electrons in semiconductors.In the PEC biosensor,the target affects the photoelectric response through specific recognition and is quantified by the magnitude of the photocurrent.Biometric components such as enzymes,antibodies,nucleic acids and peptides have specific recognition effects and can provide good selectivity for biosensors.As a two-dimensional layered material,MXene has been used in optoelectronic sensing because of its excellent surface chemical properties,optical activity,electrical conductivity,rich active catalytic center,adjustable band gap structure,easy surface functionalization and good biocompatibility.This work mainly consists of the following three parts.1.In this study,we synthesized an ultrasensitive TiO₂/MXene/CdS QDs（TiO₂/MX/CdS）heterostructure as a photoelectrochemical immunosensor,which favors energy levels matching and fast electron transfer from CdS to TiO₂ in the help of ultrathin MXene nanosheet.Dramatic photocurrent quenching can be observed upon incubation of the TiO₂/MX/CdS electrode by Cu²⁺solution from 96-well microplate,which caused by the formation of Cu S and subsequent Cu_xS（x=1,2）,reducing the absorption of light and boosting the electron-hole recombination upon irradiation.As a result,the as-prepared biosensor demonstrates a linearly increased photocurrent quenching percentage（Q%）value with CEA concentration ranging from 1 fg/m L to 10ng/m L,as well as a low detection limit of 0.24 fg/m L.Benefit from its excellent stability,high selectivity and good reproducibility of as-prepared PEC immunosensor,we believe that this proposed strategy might provide new opportunities for clinical diagnosis of CEA and other tumor markers.2.In this study,a high-performance CdS/MX/C₃N₄ composite PEC sensing platform was constructed based on ultra-thin MXene nanowires for sensitive dopamine detection.CdS/MX/C₃N₄ heterostructure electrodes were prepared by layer-by-layer deposition method.In this system,when the CdS/MX/C₃N₄ electrode is exposed to visible light,due to the effective level matching between CdS and C₃N₄,the photogenerated electrons can be transferred from the conduction band of C3N4 to the conduction band of CdS.The addition of ultra-thin MXene not only suppresses the self-aggregation of CdS and C₃N₄,but also promotes the rapid charge separation due to the rapid electron transfer in the CdS/MX/C₃N₄ composite electrode.Using CdS/MX/C₃N₄as carrier,a MIP-PEC sensor was prepared and the sensitive detection of dopamine was realized.Under visible light irradiation,the CdS/MX/C₃N₄ composite electrode shows a stable photocurrent signal.After the introduction of poly（o-phenylenediamine）film with special recognition site of dopamine,the photoelectric sensor is selective for the detection of dopamine.The designed CdS/MX/C₃N₄/r MIP photoelectric sensor can sensitively detect dopamine in human serum samples.3.In this study,a photoelectric sensing platform based on ZnS/MX/CdS heterostructure electrode was constructed for sensitive mi RNA detection.ZnS/MX/CdS shows a good photocurrent signal under light,but when the auxiliary DNA and the tested mi RNA 21 are attached to the ZnS/MX/CdS electrode through disulfide bonds,abundant double-stranded DNA is produced by catalytic hairpin assembly,and the photocurrent signal decreases.The mimic enzyme manganese porphyrin（Mn PP）was loaded on double-stranded DNA and 4-chloro-1-naphthol（4-CN）was catalyzed to benzo-4-chloro-hexanedione（4-CD）in the presence of hydrogen peroxide.The photocurrent signal decreased significantly.The sensor has a good linear relationship for the detection of mi RNA 21.This strategy can be used to construct ultra-sensitive PEC biosensors for bioanalysis and disease diagnosis.