The Construction Of Titanium Oxide Semiconductor Photoelectrochemical Biosensor And Its Application In Bioassay

Photoelectrochemical?PEC?biosensor is a kind of analysis device that detects the biological molecules with photocurrent or photovoltage signals by means of photoelectric active materials and biorecognition units.It presents obvious advantages of high photoelectric conversion efficiency,good biocompatibility,high stability,and non-toxicity.By analyzing the relationship between the photoelectric signals and the concentrations of the targets,the quantitative determination of the targets can be realized.In PEC detection,light is utilized to excite the photoactive species and the electrical signal is transduced as the detection readout,thus the distinct excitation sources and detection signals contributes potentially high sensitivity due to the reduced background noise.However,so far,most of the PEC biosensors still utilize ultraviolet?UV?or visible light as the excitation light source,which bring serious damage to biomolecules due to the high energy of the photons,and thus decrease the accuracy of the sensors.In addition,the low penetration depth of the short wavelength excitation source to biological tissue is also limiting the applications of PEC biosensors in living organism analysis.In order to broaden the application range of the PEC biosensors,titanium oxides semiconductor materials with good biocompatibility are selected as the core unit to construct the PEC biosensors with different optical response ranges.The light response range of the biosensors has been extended from the UV region to the visible region,and further reached the near-infrared?NIR?II region,the so-called“transparent window of biology”.The breakthrough of PEC analysis technology from in vitro biomolecules detection to in vivo real-time online monitoring has been finally successfully achieved.The works in this thesis mainly include the following parts:Chapter 1:IntroductionThis chapter mainly introduces the research background and basic principles of PEC,the classification and characteristics of semiconductor materials used in PEC applications,and the important applications of PEC in the fields of energy and biosensing.The research background,working principle and classification of PEC biosensors are emphasized,and the research progress and challenges of PEC biosensors based on TiO_x semiconductor materials are introduced.Finally,the research content,research purpose,significance and research innovation of this paper are summarized.Chapter 2:Highly Sensitive Identification of Phosphorylated Peptides with a Ratiometric Photoelectrochemical Biosensor Based on Different Crystal Phase TiO₂ SemiconductorThe sensitive detection of phosphopeptides is greatly significant and necessary in the fields of medicinal and bioanalytical chemistry,currently,which goal is mainly implemented through mass spectrometric?MS?method.However,the instrument of MS is very complicated and expensive,and MS is not capable of site-selective determination of phosphorylated amino acid residues.Exploration of a facile and reliable technique with high reproducibility both can sensitive discriminate the normal and phosphorylated peptides,more importantly,and can distinguish the different phosphorylated sites in peptides,is highly desirable.In this chapter,we propose a ratiometric photoelectrochemical?PEC?strategy based on the totally opposite PEC response of phosphopeptides on rutile and anatase TiO₂-based photoelectrodes,which allow us to sensitively distinguish the non-phosphopeptides and phosphopeptides,to detect the concentrations of the phosphopeptides,and to recognize the phosphorylated residues in a site-selective sensing model.The ratiometric PEC strategy significantly minimizes operation process,simplifies instrumentation,and envisions its promising and wide applications in biology,analytical chemistry,and clinic diagnostics.Chapter 3:Photoelectrochemical Biosensor Based on Defects Engineered TiO₂Nanotube Photonic Crystals Coupled with Plasmonic Gold Nanoparticles and its Application for in Vivo BioanalyisThe typical PEC biosensing is still limited under illumination of ultraviolet and visible?UV/Vis?light,which hampers its in vivo detection in deep tissues.Expanding the optical absorption wavelength of photoelectrodes from UV/Vis light region into near infrared?NIR?light region is highly desirable due to its deep tissue penetrability and minimal invasiveness for organ-isms,but the exploration of facile strategy to implement efficient NIR absorption with biocompatible materials is still a big challenge.In this chapter,under guidance of theorical calculations,we propose a strategy through modulation of bulk/surface defects and decoration of Au nanoparticles on TiO₂nanotube photonic crystals to implement efficient NIR response,and thus successfully realize sensitive and selective PEC detection of antibiotics in real bio-and experimental-samples under NIR illumination,in addition,we first implement the in vivo PEC detection under illumination of NIR light.We have faith in that this new NIR photoelectric responsive strategy will provide a broad idea and platform for detection of life-related biomolecules in deep tissues or even in vivo for real-time measurement and shed light on the intrinsic connections be-tween biomarkers and clinical diseases.Chapter 4:Fabrication of Hybrid 2D TiO_x Photonic-Plasmonic Resonators for Photoelectrochemical Biosensing Applications in Visible LightEffective light-trapping at nanoscale is vital for efficient photoelectrochemical?PEC?applications.Photonic and plasmonic resonators are the two most promising approaches for this purpose,and the synergetic combination of these two resonators will tail the propagation lengths of incident light along with field enhancements,and thus presents further enhanced light-trapping activity.In this chapter,we propose a new hybrid photonic-plasmonic resonator through sputtering plasmonic Au nanoparticles?NPs?into the two-dimensional photonic TiO_x nanocavity.Through facile controlling the size of Au NPs,the matching of resonant wavelength of plasmonic Au NPs and photonic nanocavities maximize the light-trapping intensity and thus further improve the PEC performance.Furthermore,for expanding the PEC applications,after functionalization of Au NPs with aptamer as biomolecular recognition unit,a PEC aptasensor is also proposed and presents the highest sensitivity for antibiotic detection.Chapter 5:Rationally Engineered Photonic-Plasmonic Synergistic Resonators in Second Near-Infrared Window for in Vivo Photoelectrochemical BiodetectionThe introduction of photonic technologies into bio-detection fields is in high demand to accelerate understanding vital movements in molecular level.Great difficulty lies in the fact that the short penetration of photons in bio-tissues limits the practical applications of in vivo bio-detection.In this chapter,we overcome this long-standing technical challenge through first introducing a new synergistic photonic-plasmonic resonator in second near infrared window to realize efficient light trapping in this“bio-transparent zone”.The well-match of photonic and plasmonic resonances in the same wavelength significantly increases the light-matter interplay activity,with60%increase of quality factors,thus allows us to pioneeringly implement the sensitive photoelectrochemical in vivo bio-detection of macrophage cells in the tail vein of living mouse.These synergistic photonic-plasmonic resonators promise bridges between vital photonic phenomena and practical bio-detections or clinic applications.