Novel Photoelectrochemical Bioanalysis Based On Three-dimensional Electrodes

With the wide application of sensing technology in modern life,photoelectrochemical(PEC)bioanalysis,which was evolved from electrochemical analysis,has become an important sensing technology due to its remarkable advantages in terms of low cost,fast response,high sensitivity and selectivity.In PEC bioanalysis,the excitation source(light)and detection signal(current)are totally separated which endow the potentially high sensitivity and low background signals.Under proper light irradiation,the charge transfer of PEC reactions between electron donor/acceptor and photoactive material occurs on the working electrode to realize the detection of target analyte.Acctually,PEC bioanalysis is still in the early stage because of its short development time,especially in the arena of practical applications such as clinical diagnosis and in vivo detection.Therefore,efficient detection and amplification strategies via integrating the rational design of photoactive materials are highly needed.On the basis of this requirement,the main contents of this dissertation are summarized as follows:1.Photoconductive polymer and titania nanotube array interfaced by platinum Nanoparticles:An enhanced scheme for non-enzymatic PEC glucose bioanalysisThis work presents the synthesis,characterization and PEC bioanalytical application of a ternary hybrid nanostructure of photoconductive polymer polythiophene/Pt nanoparticles/TiO₂ nanoarrays(PTh/Pt NPs/TiO₂ NAs)with enhanced properties.Specifically,the PTh/Pt NPs/TiO₂ NAs was fabricated via an all-electrochemistry procedure,consisting of electrochemical anodic oxidation of TiO₂NAs,electrochemical deposition of Pt NPs and electrochemical polymerization of PTh.Due to the fast electron transfer of TiO₂ NAs and favourable visible light absorption capacity of PTh,the ternary composite exhibited enhanced PEC property as compared to its binary counterparts.Herein,Pt NPs served as electron transport medium as well as nonenzymatic catalysts for glucose oxidation which can avoid complex enzyme modification processes.The applicability of the resulted PEC sensor for non-enzymatic glucose sensing was then verified with good performance with the linearity range of5×10^-5-7.5×10^-3 mol L^-1.As far as we know,such an all-electrochemistry fabrication of ternary PTh/Pt NPs/TiO₂ NAs has never been reported for novel PEC bioanalysis.It is believed that numerous photoconductive polymer-based heterostructures could be tailored for general PEC bioanalysis of various analytes of interest in the future.2.Cathodic PEC enzymatic biosensor based on three-dimensional nickel foam electrodesThis work reports the innovative design and application of a three-dimensional(3D)TiO₂@Cu₂O@nickel foam electrode synergized with enzyme catalysis toward the proof-of-concept study for oxygen-independent photocathodic enzymatic detection.Herein,we present the design,characterization,and implementation of 3D TiO₂@Cu₂O@nickel foam photocathodes for the firstO₂-independent example.In such a configuration,the Cu₂O acted as the visible-light absorber,while the TiO₂ shell would simultaneously function as a protective layer for Cu₂O and as a desirable substrate for the immobilization of enzyme biomolecules.Especially,as the conduction band position of TiO₂ was lower than the redox potential of(O₂/O₂^-),so thatO₂ can't serve as electron acceptor which resulted the uniqueO₂-independent PEC property of the as-designed photocathode.Exemplified by glucose oxidases,the as-developed photocathodic enzyme sensor exhibited positive response to glucose because H₂O₂ can accept electrons from the photocathode.As various oxidases could be integrated with the system,this protocol could serve as a universalO₂-independent platform for many other targets.This work is also anticipated to catalyze more studies in the advanced 3D photoelectrodes toward innovative enzymatic applications.3.A novel PEC immunosensor based on three-dimensional carbon fiber electrodesThis work reports a novel synthetic methodology for the fabrication of 3D nanostructured Cd S@carbon fiber(CF)networks and the validation of its feasibility for application as a general platform for PEC bioanalysis towards the model target protein of fatty-acid-binding protein(FABP),a kind of biomarker of acute myocardial infarction.Specifically,3D architectures are currently attracted increasing attention in various fields due to their intriguing properties,while Cd S has been most widely utilized for PEC bioanalysis application due to its narrow band gap,proper conduction band and stable photocurrent generation.Using Cd S as a representative material,this work realized the innovative synthesis of 3D Cd S@CF networks via a simple solvothermal process.Exemplified by sandwich immunoassay of FABP,the as-fabricated 3D Cd S@CF networks exhibited superior properties and the assay demonstrated good performance in terms of sensitivity and selectivity.This work features novel fabrication of 3D Cd S@CF networks that can serve as a general platform for PEC bioanalysis.The methodology reported here is expected to inspire new interest for fabrication other 3D nanostructured Cd-chalcogenide(S,Se,Te)@CF networks for wide applications in biomolecular detection and beyond.4.Split-type CuO-mediated PEC immunoassayBased on the aboved work,this work reports a customized methodology for the fabrication of 3D Cd S nanosheet(NS)-enwrapped carbon fiber framework(CFF)and its utilization for sensitive split-type CuO-mediated PEC immunoassay.Specifically,the 3D Cd S NS-CFF was fabricated via a solvothermal process,while the sandwich immunocomplexing was allowed in a 96 well plate with CuO NPs as the signaling labels.The subsequent release of the Cu²⁺ions was directed to interact with the Cd S NS,generating trapping sites and thus inhibiting its photocurrent generation.In such a protocol,the 3D Cd S NS-CFF photoelectrode could not only guarantee its sufficient contact with the Cu²⁺-containing solution but also supply plenty Cd S surface for the Cu²⁺ions.Because of the target-dependent release of the Cu²⁺ions and its proper coupling with the 3D Cd S NS-CFF photoelectrode,a sensitive split-type PEC immunoassay was achieved for the detection of brain natriuretic peptide(BNP).This system exhibited good stability and selectivity,and its applicability for real sample analysis was also demonstrated via comparison with the commercial BNP enzyme-linked immunosorbent assay(ELISA)kit.We expect this work could stimulate more interest in the design and utilization of 3D photoelectrodes for novel PEC bioanalysis.