Photoelectrochemical Sensors Based On Multi-level Signal Amplification Strategies

With the continuous development of chemical sensing technology,photoelectrochemical?PEC?sensing technology shows the unique advantages and broad prospects in the analysis of detection and molecular recognition,provides a new way for the development of new type high sensitive sensor.PEC sensor signal amplification,the main purposes is to improve the performance of the sensor,the most important thing is to realize high sensitive and low concentration detection of determinand.Therefore,development of high sensitivity of signal amplification technology has become the focus of the current analysis research direction.The material selection of photosensitive layer and the assembly of signal recognition layer are two big key points to build PEC sensor.In order to enhance the response signal,build a multi-level signal amplification system,combined with PEC sensing and different s ignal amplification method,such as new type nanocomposites,enzyme catalysis,hybridization reaction,prepared a series of optical chemical sensors based on the strategy of multi-level signal amplification,used for tumor markers,heavy metal ions,such as environmental pollutants of high sensitive detection.Mainly from the preparation of new nanocomposites,photosensitive layer building,assembly of molecular signal recognition and innovation of signal amplification technology had carried on the exploration,and various signal amplification technology was applied to the study of sensors.The major research works focus on signal amplification as follows:1)Taking advantage of CdSe/melamine network as label and Au-TiO₂ as substrate,a novel signal amplification strategy PEC biosensor has been developed for sensitive and specific detection of cancer biomarker carcinoembryonic antigen?CEA?.After the formed Ab₂-CdSe/melamine network labels were captured onto the electrode surface via the specific antibody-antigen interaction,the photoelectric activity could be further enhanced via the interaction between the Au-TiO₂ substrate and CdSe/melamine network.Under the optimal conditions,the fabricated PEC immunosensor displayed a wide linear range(0.005¹000ng·mL^-1)and low detection limit(5 pg·mL^-1).In addition,the immunosensor was performed with good stability and reproducibility,and in the actual determination of CEA has huge potential application.2)Based on surface plasmon resonance?SPR?,the interaction between the T-Hg²⁺-T interaction and DNA-CdSe specific binding of signal amplification technology,a novel PEC biosensor for the sensitive detection o f mercury ions has been designed.MoS₂-Au@Ag composites was first prepared as basal material based on the SPR effect of Au@Ag enhance photoelectric response of MoS₂ NSs,which improved electron transfer rate,and realized the signal amplification.In the presence of Hg²⁺,due to the T-Hg²⁺-T coordination effect,encourage T single-strand DNA self folding hairpin structure formation.Then signal molecules CdSe QDs are drawn close to the electrode surface and improved the charge transfer rate,which further amplified the response signal.The results show that this method exhibits high specificity and sensitivity,and quite valuable for the detection of Hg²⁺,and it has vast application potential.3)Based on Cu:TiO₂/g-C3N4 as photosensitive activity basement and enzymatic reaction in situ produce ascorbic acid?AA?as electron donor,a novel signal amplification strategy PEC biosensor has been developed for sensitive and specific detection of CEA.Cu doping can regulate the forbidden band width of TiO₂,enhance its conductivity and electrochemical performance.Cu:TiO₂/g-C₃N₄ enhanced photoelectric activity,and improved the separation efficiency of photo-induced holes-electrodes and effective charge transfer.With alkaline phosphatase?ALP?as a biomarker and Au NPs is compound to the detection antibody,and through sandwich immune into the electrode surface.ALP catalyzed ascorbic acid phosphate?AAP?produce AA as hole trapping agent.AA can provide electronic to consume photo-induced holes,and can also form AA-Ti compounds to improve the photoelectric conversion performance of basal material for further realize the dual amplification of optical signals.According to the change of the photocurrent response,can realize the quantitative detection of CEA.The sensor has the advantages including rapid response,high sensitivity and wide linear range,low detection limit,which could be applied in the actual samples tested.4)By combining proximity ligation assay with PEC sensing technology,a novel PEC immunosensor was described for the detection of estradiol.Taken Au-TiO₂ as a photosensitive basal and multifunctional carrier.Connected the signal DNA modified with CdSe QDs to DNA2-Ab₂ by DNA hybridization technology.After antigen-antibody specificity combination,the CdSe QDs-signal DNA sequence hybridized with the capture DNA on the electrode surface via the proximity effect.It makes CdSe QDs are drawn close to the electrode surface and efficient charge transfer,resulting in a significant photocurrent.The estrad iol was measured in the linear range of 0.001 to 100 ng·mL^-1 with a detection limit of 1 pg·mL^-1,and the proposed PEC sensor showed excellent specificity,stability and reproducibility.