Construction Of Aptasensors And Self-powered Sensors With Composite Photoelectrochemical Materials

As a newly emerging but dynamically developing analytical technique,photoelectrochemical?PEC?sensing platforms have been widely applied in biological and environmental analysis,due to their synergetic advantages of photocatalysis and electroanalysis.To promote the analytical performance of PEC sensing,in this project,we designed photoelectrocatalytic electrode by modifying functionalized semiconductor nanomaterials,and proposed serval photoelectrochemical analysis methods towards different target analytes in three-electrode or two-electrode system by introducing different specific recognition elements.The main contents of this dissertation were shown below.?I?.A novel cathodic“signal-off”strategy was proposed for photoelectrochemical?PEC?aptasensing of oxytetracycline?OTC?.The PEC sensor was constructed by employing a p-type semiconductor BiOI doped with reduced graphene oxide?rGO?as photoactive species and OTC-binding aptamer as a recognition element.The morphological structure and crystalline phases of obtained BiOI-rGO nanocomposites were characterized by scanning electron microscopy?SEM?and X-ray diffraction?XRD?.The UV-visible absorption spectroscopic analysis indicated that doping of BiOI with graphene improved the absorption of materials in the visible light region.Moreover,graphene could facilitate the electron transfer of BiOI modified electrode.As a result,the cathodic photocurrent response of BiOI under visible light irradiation was significantly promoted when a suitable amount of graphene was doped.When amine-functionalized OTC-binding aptamer was immobilized on the BiOI-rGO modified electrode,a cathodic PEC aptasensor was fabricated,which exhibited a declined photocurrent response to OTC.Under the optimized conditions,the photocurrent response of aptamer/BiOI-rGO/FTO was linearly proportional to the concentration of OTC ranging from 4.0 to 150 nM,with a detection limit?3S/N?of0.9 nM.This novel PEC sensing strategy demonstrated an ultrasensitive method for OTC detection with high selectivity and good stability.?II?.A self-powered sensing system possesses the capacity of harvesting energy from the environment and has no requirement for external electrical power supply during the chemical sensing of analytes.Herein,we design an enzyme-free self-powered sensing platform based on a photofuel cell?PFC?driven by visible-light,using glucose as a model analyte.The fabricated PFC consists of a Ni?OH?2/CdS/TiO2 photoanode and a hemin-graphene?HG?nanocomposite coated cathode in separated chambers.Under visible-light irradiation,glucose in the anodic chamber is facilely oxidized on Ni?OH?2/CdS/TiO2 while H2O2 in the cathodic chamber is catalytically reduced by HG,which generates a certain cell output sensitive to the variation of glucose concentration.Thus,a PFC based self-powered sensor is realized for glucose detection.Compared to the existing enzymatic self-powered glucose sensors,our proposed PFC based strategy exhibits much lower detection concentration.Moreover,it avoids the limitation of conventional enzyme immobilized electrodes and has the potential to develop high-performance self-powered sensors with broader analyte species.?III?.A photocathode-based photocatalytic fuel cell?PFC?was fabricated and proposed as a self-powered sensor for p-nitrophenol?p-NP?detection.The PFC was comprised of a photocathode and an anode in separated chambers,which could generate suitable power output under photoirradiation to drive the sensing process.In this device,p-type PbS quantum dots-modified glass carbon electrode?GCE?served as the photocathode for the reduction of p-NP under photoirradiation while graphene-modified GCE was employed as the anode for the oxidation of ascorbic acid.To improve the selectivity of the PFC sensor,p-NP binding molecularly imprinted polymer?MIP?was introduced on the photocathode.Under optimal conditions,the open circuit voltage of the constructed PFC sensor was found to sensitively respond to p-NP in a wide concentration range from 0.05?M to 20?M.The proposed sensor exhibited high selectivity,good reproducibility,and stability,demonstrating the successful combination of MIP with photocathode in construction of high-performance PFC self-powered sensors for pollutant monitoring.?IV?.A membraneless,hydrogen peroxide-based photocatalytic fuel cell was proposed and applied in the self-powered sensing of polychlorobiphenyl.The PFC was comprised of a g-C3N4-Au modified photoanode and a Graphene-Hemin cathode.H2O2 was photocatalytically oxidized on the photoanode and electrocatalytically reduced on the cathode,which induced the electrons transfer and generated a certain electric power output.The proposed photofuel cell exihibited an acceptable output performance and good stability.To fabricate the self-powered sensor,3,3',4,4'-Tetrachlorobiphenyl?PCB77?-binding aptamer was assembled on the photoanode to act as the recognition element.Under optimal conditions,the open circuit voltage of the PFC was found to sensitively respond to PCB77in a concentration range from 10¹000 ng·mL^-1,with a detection limit of 4.5 ng·mL^-1.This novel strategy not only provided a new perspective for the construction of self-powered sensing platforms,but also broaden the application area of PFCs.