Construction Of Pec Sensors Based On Precisely Controlled CdS Semiconductor Nanomaterials And Their Applications

Objective:To prevent the recombination of the photogenerated electron-hole,promote photocurrent response and diminish photocorrosion effects of CdS semiconductor nanomaterials,CdS-based composite nanomaterials with excellent photoelectrochemical（PEC）performance were synthesized at the atomic level.High-efficient PEC sensors based on CdS composite nanomaterials were successfully constructed,which provide potential applications for drug quality control,early disease diagnosis and environmental monitoring.Methods:（1）In the first part:the synthesis of CdS-Au composite nanomaterials was carried out by deposition-precipitation（DP）method,and CdS-Au composite nanomaterials were modified on the working electrode surface with electrochemical impedance spectroscopy（EIS）and photocurrent analysis.The changes in photocurrent values of different concentrations of ascorbic acid（AA）solutions were investigated under optimal conditions,the reproducibility,selectivity and stability of the CdS-Au PEC sensor were effectively evaluated.Afterwards,the self-constructed PEC sensor can be successfully applied to the detection of AA in vitamin C tablets and real blood samples.At last,the mechanism of the PEC sensor for the detection of AA to be further clarified.（2）In the second part:a series of CdS/x Ni O（x presents the number of ALD cycles）composite nanomaterials with accurate and controllable at the atomic level were synthesized by atomic layer deposition（ALD）.The PEC biosensor with excellent performance based on CdS/80Ni O composite nanomaterials was constructed and successfully applied to the highly sensitive determination of glucose concentration.Under the optimal experimental conditions,we analyzed the relationship between the photocurrent signal and glucose concentration,and explored the selectivity and stability of the CdS/80Ni O-glucose oxidase（CdS/80Ni O-GOD）PEC biosensor.In conclusion,the self-constructed PEC biosensor can be used to detect the content of glucose in real serum and has illustrated the detection mechanism.（3）In the third part:The CdS/80Ni O-Au composite nanomaterials were prepared by DP and ALD methods.The CdS/80Ni O-Au,aptamer and bovine serum albumin（BSA）were modified sequentially on the surface of fluorine doped tin oxide（FTO）working electrode,and the various modifications of the FTO working electrode were characterized by measurements of the EIS and the photocurrent response.The detection of different concentrations of E.coli O157:H7 can be achieved with the CdS/80Ni O-Au/aptamer/BSA/FTO working electrode under optimal conditions.In this study,the PEC aptasensor was applied for the measurement of the selectivity,reproducibility and stability,the recoveries of water samples were determined and the detection mechanism of the aptasensor was analyzed and discussed.Results:（1）The results of the photocurrent response analysis indicated that the optimal detection conditions for the PEC sensor are as follows:the concentration of CdS-Au composite nanomaterials was 5 mg·m L^-1,the applied potential was 0.2 V and the p H of the phosphate buffer solution（PBS）was 7.40.Under the ideal conditions,the AA concentration was linearly related to the photocurrent signal in the range of 0.01?mol·L^-1-200?mol·L^-1,the regression equation was y=0.18x+4.39（R²=0.9942）,the detection limit was 0.2 nmol·L^-1（S/N=3）,and the sensitivity was 642.9μA·(mmol·L^-1)^-1·cm^-2.Remarkably,the PEC sensor based on CdS-Au composite nanomaterials showed excellent selectivity,reproducibility and stability.The content of AA in the unexpired vitamin C tablets was 97.0±0.6 mg,whereas the content of AA in the expired vitamin C tablets was82.9±0.5 mg,with the average recoveries of serum samples ranging from 99.2%to100.3%.（2）The precisely controlled CdS/x Ni O composite nanomaterials with excellent photoelectrochemical performance at the atomic level were successfully synthesized by ALD.The experimental results showed that the photoelectrochemical performance of the PEC biosensor was best when the number of deposition cycles was 80,the concentration of CdS/80Ni O was 5 mg·m L^-1,the applied potential was 0.2 V,and the volume of GOD was30?L.The PEC biosensor demonstrated a satisfactory linear response to glucose in the range of 0.0-11.0 mmol·L^-1,the sensitivity was 44.0?A·(mmol·L^-1)^-1·cm^-2 and exhibited a low detection limit was 3.4×10^-10 mol·L^-1（S/N=3）under ideal conditions.The coexisting serum dopamine（DA）,sucrose,ascorbic acid（AA）and sodium chloride（Na Cl）had almost negligible effects on the measurement,and the PEC biosensor showed high stability.Finally,the self-constructed PEC biosensor can be applied to detect the content of glucose in serum with relative standard deviations（RSDs）ranging from 1.3%to 2.2%.（3）The CdS/80Ni O-Au composite nanomaterials were fabricated by DP technique and ALD method.The experimental results demonstrated that the photocurrent signal of the self-constructed PEC aptasensor reached the maximum value when the concentration of CdS/80Ni O-Au was 3 mg·m L^-1,the applied potential was 0.2 V,the concentration of AA was 15 mmol·L^-1,the concentration of the aptamer was 0.8?mol·L^-1,the incubation time was 12 h for the aptamer and the incubation time was 60 min for E.coli O157:H7.At the ideal experimental conditions,the PEC aptasensor based on CdS/80Ni O-Au is successfully developed for different concentrations of E.coli O157:H7 detection,with a linear correlation between the photocurrent intensity and the logarithm of E.coli O157:H7concentration in the range of 1.0-1.0×10⁵ CFU·m L^-1 and the detection limit as low as 0.32CFU·m L^-1（S/N=3）.The PEC aptasensor exhibited outstanding selectivity,reproducibility and stability,and the average recoveries were in the range of 98.8%-100.9%for the detection of real water samples.Conclusion:In this paper,a series of CdS-based composite nanomaterials with significantly enhanced photoelectric activity were synthesized by DP method and ALD technique.On this basis,the high-performance PEC（biosensors）sensors were constructed which achieved simple,rapid and highly sensitive detection of targets.The self-constructed PEC（biosensors）sensors were applied for drug quality monitoring,early disease diagnosis and environmental monitoring,the experimental results were satisfactory and in accordance with related national regulations.The results of this study provide a new idea for the application of PEC（biosensors）sensors based on CdS photoelectric active composite nanomaterials in the field of medicine,pharmacy and environment.