Fabrication Of Novel Photoelectrochemical Sensors And The Applications In Devices

Photoelectrochemical(PEC)sensor is a kind of novel detection sensor,which was widely investigated in the decade.The signal is measured due to the impact of the target concentration on photoelectric conversion properties of photoelectric material.In a PEC sensing system,with light as excitation signal and electrical signal as the detection signal,excitation process and detection signal are separated.Therefore PEC detection has the advantage of low background and sensitivity similar to electrochemiluminescence.Meanwhile,the low voltage in the PEC process also gives a rather mild testing environment and therefore more suitable for biological analysis.PEC sensor shows unique advantages and broad application prospects in biological analysis.The proper use of the charge carrier and conductive type of semiconductor,and full use of photoelectric active material inject new vitality for PEC sensor.1.Carbon nitride nanosheets sensitized quantum dots as photocathode for photoelectrochemical biosensingA highly efficient photocathode,based on graphite-like carbon nitride nanosheets(CNNS)sensitized CdTe quantum dots(QDs),was constructed for PEC biosensing.Using dissolved oxygen as an electron acceptor,the hybrid photocathode showed a sensitive photocurrent response at-0.2 V bias potential under 405 nm illumination.The CdTe/CNNS hybrid photocathode demonstrates about 100%increase of photocurrent compared to CdTe QDs modified electrode owing to the formation of heterojunction through contact of twosemiconductor materials.The improved charge separation efficiency was identified by the extension of electron transit time(?d)and electron lifetime(in)in this PEC system.The introduction of Cu2+ on the surface of hybrid photocathode could decrease photocurrent via the exciton trapping quenching effect.A sensitive PEC sensor for Cu2+was thus developed with a good linear range from 20 nM to 100 ?M and a detection limit of 3.3 nM.Moreover,the hybrid photocathode showed acceptable stability and excellent anti-interference ability,and was successfully applied in the detection of Cu2+in human hair samples.The CNNS-sensitized photocathode provides a good alternative for enhancement of the PEC signal transduction and could be widely used in biosensing and clinical diagnosis.2.Wavelength-resolved ratiometric photoelectrochemical technique:design and sensing applicationsIn this work,a wavelength-resolved ratiometric photoelectrochemical(WR-PEC)technique was investigated and employed to construct a new type of PEC sensor with good sensitivity and anti-interference ability.The WR-PEC hybrid photoelectrodes were stepwise assembled by semiconductor quantum dots(QDs)and photoactive dyes.Under continuous irradiation,photocurrent-wavelength(I-?)curves reveal the dependence of the photocurrent on the wavelength.By monitoring the ratios of two different PEC peak values,a wavelength-resolved ratiometric strategy was realized.Using CdS QDs and methylene blue(MB)as photoactive models,a dual-anodic WR-PEC sensor was established for sensitive detection of Cu2+.This ratiometric strategy was identified to be on the basis of quenching effect of Cu2+towards CdS QDs and enhancement of MB photocurrent through catalytic oxidation of leuco-MB.Under continuous illumination from 400 nm to 800 nm at 0.1 V bias potential,a WR-PEC sensor for Cu2+was developed with a wide linear range and a detection limit of 0.37 nM.This WR-PEC greatly improved anti-interference ability in complex environment,and showed acceptable stability.Moreover,using the CdS/magnesium phthalocyanine(MgPc)and CdTe/MgPc as photoelectrodes,the anodic-cathodic and dual-cathodic WR-PEC sensors were established,respectively.The WR-PEC technique would serve as a novel concept for design ratiometric or multi-channel PEC sensors.3.Smart Tablet System:A Portable,Vizualized and Reversiable Mobile Photoelectrochemical Sensing DeviceIn this work,we constructed a complete mobile photoelectrochemical analytical system.Based on Smart Tablet structure,a really visualized PEC sensing device with portability and reversibility was designed and developed.The Smart Tablet structure was assembled by a sandwich ITO slices structure with dye sensitized TiO2 and NiO nanosheet film separated with each other.While irradiated by LED flashlight,the dye sensitized TiO2 would act as electro-source to bring NiO nanosheet to different color state,and the color change can be distinguished by naked eyes.By monitoring the color change,visualized PEC sensing platform was constructed successfully.Using Cu2+as a model analyte,based on the quenching effect to photovoltage through the formation of exciton trapping,a portable,visualized mobile PEC device for the detection of Cu2+was established.The determination of Cu2+ within a wide range could be realized through recording photovoltage,RGBavg and using naked eyes.The device exhibited considerable stability and could be recycling used through simple operation.The Smart Tablet PEC system provides a novel idea to design practical PEC sensor and might serve as a powerful tool for clinical detection.