Preparation Of Graphene And Rare Earth Nanomaterials And Their Applications In Electrochemical Sensors

Nanomaterials were widely used in different fields containing chemistry,biology and material science and so on,due to its unique physicochemical properties.With the rapid development of nanoscience and nanotechnology,preparation methods of nanomaterials of rare earth,graphene and its derivatives were developed rapidly.Because of their excellent electrochemical performance of large surface area,high catalytic and good biocompatibility,nanomaterials of rare earth compound and graphene were widely used in field of electrochemical sensor.Meanwhile electrochemical sensor is an important detection technology in the field of chemical analysis and widely used in the environmental monitoring,pharmaceutical analysis,food processing depending on its wide detection rang,high sensitivity,good stability,simple operation and other advantages.In the paper,novel electrochemical sensors were developed based on nanomaterials for analysis and detection of molecular and ion.The main research results were as follows:?1?A new rare earth oxide of Er₂O₃ was employed for the construction of glucose biosensor.Er₂O₃ was mixed with graphene oxide?GO?to form the supported matrix for immobilization of glucose oxidase?GOD?onto the glassy carbon electrode?GCE?.The nanomaterials of Er₂O₃ and GO were firstly synthesized and characterized by SEM,XRD.The fabrication process for the biosensor was monitored by electrochemical impedance spectroscopy?EIS?and cyclic voltammetry?CV?.The presence of Er₂O₃ could effectively maintain the bioactivity of GOD and enhance the electron transfer rate.The prepared biosensor showed a pair of distinct and well-defined redox peaks,indicating the fast direct electron transfer?DET?rate between the redox-active site of GOD and GCE,which could be attributed to the synergistic effect of the GO/Er₂O₃ nanocomposite.When employed to the electrocatalytic detection of glucose,the CV response of the prepared biosensor decreased against the concentrations of glucose.The calibration curve corresponding to the CV response was linear against the concentrations of glucose ranging from 1 to 10 mM.Moreover,the electrochemical sensor showed good stability and reproducibility.?2?The nanomaterial of n-HoPO₄ was synthesized via the hydrothermal method,and its morphology and component were characterized by SEM and EDS.The composite material of n-HoPO₄ and Hemoglobin?Hb?was dropped onto the surface of the glassy carbon electrode?GCE?so as to construct the biosensor for the detection of hydrogen peroxide.The whole process was characterized by CV and EIS.The n-HoPO₄ showed good electrical conductivity and could promote the direct electron transfer rate between Hb and GCE.The result indicated that Hb/n-HoPO₄/GCE possessed good electrocatalytic ability towards H₂O₂.Under optimal conditions,the biosensor exhibited a good linear detection range from 50 ?M to 1000 ?M?correlation coefficient R2=0.998?with the detection limit of 16.67 ?M?S/N=3?.What's more,the biosensor showed wide detection range,good stability and reproducibility and strong anti-interference ability,and could be used for the real sample detection.?3?Material of grapheme quantum dots was dropped onto the surface of glassy carbon electrode to form its film.Afterwards,electrochemical sensor was successfully designed for determination of nitrite?NO₂^-?.Transmission electron microscopy?TEM?and X-ray diffraction?XRD?was utilized to characterize grapheme quantum dots?GQDs?.Meanwhile,electrochemical behavior of nitrite was researched by cyclic voltammetry?CV?,differential pulse voltammetry?DPV?and current-tine curve?i-t?on surface of modified electrode.The experimental results showed that electrochemical sensor exhibited a good electrocatalysis to NO₂^-and possessed a broad linear range from 1 to 29 ?M,detection limit of 3.33×10-7 M?S/N=3?.The electrochemical sensor showed wide detection range,low detection limit and good stability.?4?The Dy₂?WO₄?₃ was synthesized by hydrothermal method and Au-Dy₂?WO₄?₃ was prepared via the in-situ reduction of chloroaurate acid?HAuCl4?.Nanomaterials were characterized by UV and TEM.The material of Au-Dy₂?WO₄?₃ was dropped onto the surface of glassy carbon electrode for the construction of electrochemical sensor.The modified electrode preparation process was characterized by CV.DPV was employed for researching electrochemical behaviors of UA and NO₂^-on the modified electrode.The results indicated that the electrochemical sensor exhibited a good electrocatalysis to UA and NO₂^-in range of 0.08-1.0 mM and 0.01-1.0 M with the low detection limits of 2.67×10-5 mM and 3.33×10-6 M,respectively.