Design And Applications Of Semiconductor Nanomaterials In Electrochemical And Photoelectrochemical Analysis

Bio-molecules are an important class of substances that balance human physiological activities.Their highly sensitive detection and analysis can help people reveal the basic rule of information generation,storage,transmission,processing,transformation and control in life systems,which accurately explain the meaning of life.The mechanism of vital activity is of great significance for the discovery and treatment of a variety of human diseases.Biosensors are one of the main tools for detecting bio-molecules.They are bio-functional sensors made of bioactive substances and equipped with appropriate signal converters.The research work in this thesis focuses on the preparation of transition metal phosphides and metal oxides to construct new electrochemical and photoelectrochemical biosensors,which includes utilizing transition metal phosphide semiconductor nanomaterials to build a new electrochemical?EC?sensing analysis platform.Establishing metal oxide-nano-composite nanomaterials for novel photoelectrochemical?PEC?sensing analysis platform,and realized highly sensitive and selective detection of H₂O₂ released from living tumorigenic cells?RAW 264.7?.On this basis,we combine the metal oxide with the recognition unit to design an efficient charge transfer channel and construct a highly efficient photoelectrochemical aptasensor.In addition,we have developed a new generation of near infrared?NIR?responsive photoelectrochemical sensing detection platform based on the plasmon resonance nanoparticles and two-dimensional photonic crystals,which will open up a new in vivo biosensing model for effective detection of important biomolecules in deep tissue or even in organs and brain of living body.The specific work of this paper includes the following five aspects:Chapter 1:OverviewThis chapter mainly introduces the theory,concept,and application of electrochemical biosensors,photoelectrochemical overview,the classification and development of photoelectrochemical biosensors.Finally,we proposed the concept of research and innovation of this paper.Chapter 2:Copper phosphide nanowires for sensitive electrochemical detection of H₂O₂ release from living cellsIn this work,we clearly demonstrate the use of transition-metal phosphides to set up a new cathodic analysis platform for sensitive and selective electrochemical nonenzymatic detection of H₂O₂.The noble metal-free electrocatalyst of copper phosphide nanowires on three-dimensional porous copper foam?Cu₃P NWs/CF?is fabricated with electrochemical anodized Cu?OH?₂ NWs as precursor.The Cu₃P NWs/CF-based sensor presents excellent electrocatalytic activity for H₂O₂ reduction with a detection limit of 2 nM,which guarantees the possibility of sensitive and reliable detection of H₂O₂ release from living tumorigenic cells.Chapter 3:New photocathodic analysis platform with quasi-core/shell-structured TiO₂@Cu₂O for realizing the photoelectric reduction detectionIn this work,we clearly demonstrate the use of a p-type semiconductor,Cu₂O,as the core unit of a photocathode to set up a new photocathodic analysis platform.With the help of a facile protection strategy,the Cu₂O photocathode presented efficient photoelectrochemical performance for H₂O₂ sensing with a detection limit of 0.15?M,which allowed the new photocathodic analysis platform to detect H₂O₂ released from living tumorigenic cells.The protected TiO₂ layer was coated on Cu₂O to form a quasi-core/shell structure?TiO₂@Cu₂O?through a facile sol-gel method,which significantly enhanced the photostability,comparable to the TiO₂@Cu₂O samples prepared by a complicated atomic layer deposition method.The photocathodic detection strategy opens up a new detection approach,extends the application range of semiconductor materials,and thus sheds light on the further fusing of photoelectrochemical technique with analytical methods.Chapter 4:Gold nanoparticles decorated hematite photoelectrode for sensitive and selective photoelectrochemical aptasensing of lysozymePhotoelectrochemical aptasensor is a new and promising detection platform with both high sensitivity and good selectivity.As a biomolecular recognition unit,aptamers have high affinity and specificity for target selection.In this work,an efficient photoelectrochemical aptasensor based on Au nanoparticles?NPs?decorated Fe₂O₃nanorod photoelectrode is rationally designed,fabricated,and exhibited excellent sensitivity and selectivity for detection of lysozyme?Lys?with an ultralow detection limit of 3 pM and wide detection range from 10 pM to 100 nM.The Au NPs not only act as anchor to establish an efficient charge transfer channel between the photoelectrode and the aptamer,but also help to enhance the PEC performance through adjusting the carrier density of Fe₂O₃.The rationally designed photoelectrode opens up a distinctive avenue for promoting the photoelectrochemical aptasensor to be a versatile analysis method.Chapter 5:Plasmonic nanoparticles on nanocavity photonic crystal to establish near-infrared responsive photoelectrochemical sensorPEC biosensing is a new method in analytical technique.However,limited by the short penetration depth of ultraviolet-visible light in deep tissue,the application of PEC sensing in vivo is seriously obstructed,and the exploration of near infrared light responsive PEC sensors are desirable.In this work,the Au NPs with surface plamonic resonance property are deposited on two dimensional TiO₂ nanocave photonic crystal,which can implement sensitive detection.In addition,the aptamers,molecular recognition units,are further modified on the surface of photoelectrodes,which is helpful to realize selective detection.The proposed novel near infrared PEC aptasensor will open up a new in vivo biosensing model for effective detection of important biomolecules in deep tissue or even in organs and brain of living body.