Design of Function-oriented Carbon-based Sensor and the Analytic Applications of Biomolecules and Environmental Ions

Author:Liu Shuang Yan

Supervisor:chen yong mei


Degree Year:2018





In the field of electrochemical analysis,a response with high sensitivity,high reproducibility and high stability of the analyte has been the pursuit of the electrochemical sensor diligently,and the construction of the electrochemical sensor depends on the design of the electrode materials and the structure of the electrode.Different performance of electro analysis request different functional requirements for electrode materials and structures of electrochemical sensors.In this paper,for the electroanalysis of small biomolecules and heavy-metal ions,carbon-based electrochemical sensors based on traditional and new sp2 hybrid carbon materials are designed,and the functionalized carbon materials and electrode structures in the field of electroanalysis are investigsted.The specific contents are as follows:1.The preparation of glassy carbon electrode(GCE)with strong adsorption interface and its analytic application of 5-hydroxyindoleacetic acid(HIAA):A major obstacle to the electro analysis of HIAA is that the weak interaction between HIAA and the traditional electrode causes a irreversible behavior of electrode reaction,and makes it difficult to provide a quantitative basis.In order to enhance the interaction force between HIAA and the surface of electrode,an adsorption capacity-oriented electrochemical sensor is proposed.In this paper,the oxygen-containing groups such as hydroxyl and carboxyl group are introduced into GCE surface by electrochemical oxidation in acidic medium.The obtained oxidized GCE(OGCE)adsorbs HIAA and its intermediate products via the formation of hydrogen bonds and reduces irreversibility.The kinetics of HIAA on OGCE are studied and the reaction mechanism is proposed.After three cycles of cyclic voltammetric scanning,the current remaines stable,makes it possible to analyze HIAA quantitatively on the basis of the stable current.The linear range is 1.52-58.6 μM,and the limit of detection is 0.917 μM,while the RSDofcurrent is only 1.34%.The 500-1000 folds of inorganic salts,1000 folds of urea,and 500 folds of glucose shows no interference in detection.2.The preparation of graphite felt electrode(GFE)with large area and strong adsorption interface and its analytic application of HIAA:A higher response sensitivity for HIAA is proposed on the basis of the foregoing.One of the effective methods to enhance sensitivity is that the sensor has large surface area,and GFE just has the characteristics of large area and high porosity.However,its hydrophobic surface hinders its large area performance.In order to improve the hydrophilicity and construct the adsorption interface at the same time,the chemical oxidation method in concentrated acid is adopted to pretreat GFE.The results show that the hydroxyl and carboxyl groups formed on the surface of the electrode show a stronger adsorption behavior for HIAA than OGCE,as it could catch the reduced products that OGCE could not capture.Thus,the reversibility of electrode reaction and the CV characteristics of HIAA change further.After the supplement of the reaction mechanism of HIAA,the quantitative analysis is carried out.A good linear relationship in the range of 0.35-26.5 M was obtained and the detection limit of 0.0941 μmol/L was 10 times lower than that of OGCE.3.The preparation of carbon nano tubes(CNTs)modified electrode with specific adsorption interfaces and its analytic application of DA:the main obstacle to the electrochemical detection of DA is the overlapping signal interference from the coexisting ascorbic acid(AA)and uric acid(UA).To this end,the requirement for selective detection on the electrode is put forward.Considering that DA is positively charged while AA and UA are negatively charged under specific pH,an electrode with negative interface is proposed to specifically adsorb DA.In this paper,SDPAS/PPy/CNTs modified gold electrode is prepared by electrochemical polymerization.A negative SDPAS-co-PPy copolymer is confirmed to be produced in pH 6.0 solution.With the electrostatic repulsion to AA and UA ions and the electrostatic attraction to DA,AA and UA molecules,the signals are separated and no interference are observed during coexistence detection,resulting in a higher selectivity and sensitivity than unmodified electrode.A good linearity was obtained in the range of 0.827-104 μmol/L with a LOD of 0.105 μmol/L by SWV method,and finally it realized the detection in simulate serum samples.4.The preparation of reduced graphene oxide/carbon nanotubes(RGO/CNTs)modified electrode with 3D electronic transmission and its analytic application of DA:The electrochemical detection of DA is also limited by the lack of sensitivity,and the enhancement of sensitivity can be achieved by speeding up the rate of heterogenous electron transport.Therefore,a RGO/CNTs sensing electrode for 3D electron-conduction is prepared by microwave method,combined with the characteristics of ID CNTs and 2D RGO.The results show that with ferrocene as a catalyst and carbon source,ADC as an expander,and acetonitrile as a solvent,a 30 s microwave treatment is enough to grow carbon nanotubes on the surface of graphene.The diameter and density of CNTs are affected by the amount of ADC and ferrocene respectively.3D RGO/CNTs modified GCE shows a faster heterogenous transfer rate constant.The CV method is empolyed to quantify DA,leading to a well linear relation in 3.33-198 μmol/L.5.The preparation of bismuth film modified screen-printed electrode(Bi-SPCE)with microintegrated structure and its analytic application to heavy metal ions:Electroanalysis of heavy metal ions in water requires an on-the-spot monitoring.Therefore,a small-scale and portable sensor is demanded.In this paper,the self-made screen-printed electrode(SPCE)is used as carbon electrode,and the SPCEis modified bypre-lating bismuth film on the surface to obtain Bi-SPCE by electrochemical deposition.The research shows that the self-made SPCE exhibits good conductivity,stability and reproducibility.The effects of electroplating conditions on the morphology and properties of the Bi-SPCE are investigated and optimized,containing plating voltage,time,and the concentration of bismuth ions and additive.A shape of porous gridding flower is obtained.The pH,enrichment potential,enrichment time and equilibrium time during the simultaneous detection of Pb2+,Cd2+ and Zn2+ are also optimized.After optimization,the lowest detection limit and RSD of Pb2+,Cd2+ and Zn2+can be 7.1 μg/L and 1.97%,which reveals a good sensitivity and stability.Finally,the Bi-SPCE was successfully applied for analysis of these heavy metals in real water samples.