Design And Applications Of Photoelectrochemical Biosensors Based On N-type Semiconductor Materials

Photoelectrochemical?PEC?sensor is a new kind of detection method emerging after the electrochemical,photochemical and optical analysis in recent years.The basic principle of PEC bioanalysis is developed on the change of photocurrent or photovoltage,which is caused by the chemical or physical interaction between the analyte and the photoactive substance.The PEC sensor possesses the advantages of low background interference,high sensitivity and fast response due to its unique signal transducing modality,excitation energy source of light and readout signal of electricity.Among them,the development of PEC sensors based on nano-semiconductor materials has attracted much attention,which is mainly due to the unique photoelectric chemical properties and superior biosolubility of this materials.However,nano-semiconductor PEC sensor still has considerable difficulties and challenges,such as synthesizing cheap and efficient nano-semiconductor photoelectrochemical active material,improving the selectivity of sensors,reducing the cost of sensors,improving the detection methods and developing new detection methods of PEC sensors.To solve these problems,TiO₂ and BiVO₄ of n-type semiconductor materials with good stability and non-toxic are selected as the research objects to improve the photoelectric conversion efficiency of the material in the visible region through the improvement of synthesis conditions,ion doping and Au NPs modification.A novel recognition unit PEC aptamer sensor based on the formation of Au-S bond was firstly set up to accomplish the sensitive and selective detection of biological molecules.In order to further reduce the cost and improve the universality of the sensor,a new type of PEC sensor without recognition unit was proposed based on chemical bonding or electrochemical enrichment means,which also achieve high sensitive and selective detection of biological molecules and metal ions.This paper provides a new idea for PEC sensing and more possibilities for solar energy utilization.The content mainly includes the following parts:Chapter 1: OverviewThis chapter systematically introduces the research background,working principle and progress of PEC sensors,as well as the characteristics and improvement of nanosemiconductor photoelectric materials.We focus on the research progress and existing problems of PEC sensors based on n-type nano-semiconductor material TiO₂ and Bi VO₄.Finally,we proposed the research content and significance of this paper.Chapter 2: Photoelectrochemical aptasensor for the sensitive and selective detection of kanamycin based on Au nanoparticle functionalized self-doped TiO₂ nanotube arraysIn this work,a new photoelectrochemical aptasensor with Au NPs functionalized self-doped TiO₂ nanotube arrays?Au/SD-TiO₂ NTs?as core sensing unit and aptamers as recognition unit was set up to accomplish the sensitive and selective detection of kanamycin with the lowest detection limit of 0.1 n M.The Au/SD-TiO₂ NTs photoelectrode was rationally designed with synergistic effect between surface plasmon resonance from the Au NPs and inter-bands from the self-doping induced Ti3+ center,which boosted the PEC performance under visible light irradiation.This work not only confirmed the feasibility of PEC aptamer biosensor based on TiO₂ NTs,but also opened up a new detection approach for the design of PEC sensor.Chapter 3: Sputtering gold nanoparticles on nanoporous Bi VO₄ for sensitive and selective photoelectrochemical aptasensing of thrombinIn this work,we report the first demonstration of an efficient photoelectrochemical aptasensor based on sputtering Au nanoparticle-modified nanoporous Bi VO₄ for the excellent sensitive and selective detection of thrombin.Characterization of materials aproved that the sputtering method not only guarantees a better seamless connection between the Au NPs and Bi VO₄,but also achieves a superior electronic structure of Bi VO₄ through the highly energetic bombardment of Au NPs for further defect engineering.In addition,the PEC aptamer sensor was assembled by integrating an aptamer into the surface of electrode by the Au-S bond,which realized the high sensitivity and selectivity of thrombin detection with a low detection limit of 0.5 p M and a large linear rang.Finally,the PEC aptamer sensor was successfully used to detect thrombin in human serum based on the non-toxic and biosoluble properties of Au/Bi VO₄ material.This work showed PEC aptamer sensor has a good development prospecta and provides more possibilities for the utilization of solar energy.Chapter 4: Recognition unit-free and self-cleaning photoelectrochemical sensing platform on TiO₂ nanotube photonic crystals for sensitive and selective detection of dopamineFor implementing a simple biosensor without loss their sensitivity and selectivity,a prototype of recognition biomolecule unit-free PEC sensing platform with selfcleaning activity is proposed with TiO₂ nanotube photonic crystal?TiO₂ NTPCs?materials as photoelectrode,and dopamine?DA?molecule as both sensitizer and target analyte.The unique adsorption between DA and TiO₂ NTPCs induces the formation of charge transfer complex,which not only expends the optical absorption of TiO₂ into visible light region,thus significantly boosts the PEC performance under illumination of visible light,but also implements the selective detection of DA on TiO₂ photoelectrode.This simple but efficient PEC analysis platform presents a low detection limit of 0.15 nm for detection of DA,which allows to realize the sensitive and selective determination of DA release from the mouse brain for its practical application after coupled with a microdialysis probe.The DA functionalized TiO₂ NTPCs PEC sensing platform opens up a new PEC detection model,without using extrabiomolecule auxiliary,just with target molecule naturally adsorbed on the electrode for sensitive and selective detection,and paves a new avenue for biosensors design with minimalism idea.Chapter 5: A novel photoelectrochemical stripping analysis based on Bi VO₄ for highly selectivity and sensitivity detection of silver ionsIn this work,the anodic stripping method and photoelectrochemical technique are integrated into a new detection platform of PEC stripping analysis?PECSA?with Bi VO₄ as both optoelectronic material and an electrochemical enrichment candidate.Compared with the traditional electrochemical anodic stripping method,this new analysis platform is more sensitive in the detection of silver ion?Ag⁺?,which is mainly due to the fact that the PECSA possess both the enrichment effect of anodic stripping method and the high sensitivity of photoelectric chemistry.In addition,this strategy also offers new selectivity dimensions through the potential-dependent response and thus implements reproducible,sensitive,and selective detection of Ag⁺ in real biological and environmental samples.The success of PECAS strategy shed light on the rational combination of various analysis techniques for versatile applications.