Fabrication Of Electrochemical Sensor Based On Functionalized Graphene And Its Application In Pharmaceutical Analysis

Graphene?Gr?,a two-dimensional,single-layer sheet of sp2 hybridized carbon atoms,has unique advantages in the construction of electrochemical sensor owing to its large specific surface area,high electronic conductivity and excellent mechanical strength.However,Gr sheets tend to form irreversible agglomerates through ?-?stacking and Van Der Waals interaction,which greatly limits the practical applications.To avoid this problem,some functionalized reagents were introduced to the Gr surface.At the same time,metal oxide can be loaded on the surface which further form Gr-metal oxide composites.Through the synergistic effect of Gr and metal oxide,excellent electrochemical sensors can be frabicated.According to the ideas,a series of voltammetric sensors based on functionalized graphene were prepared,which implemented the sensitive determination of drug molecules.The content mainly included the following three sections:?1?In this part,poly?diallyldimethylammonium chloride?-functionalized graphene?PDDA-Gr?was prepared via a simple wet chemical method.Characterization was performed by ultraviolet/visible spectra?UV-vis?,fourier transform infrared spectroscopy?FT-IR?,X-ray diffraction?XRD?and transmission electron microscopy?TEM?.The voltametric sensor based on this nanocomposite was used to detect hyperin.Under the optimized conditions,a lower detection limit of5×10-9mol L^-1?S/N=3?and a wide linear detection range from 7×10-9to 7×10-7mol L^-1 were achieved by the differential pulse voltammetry?DPV?.Additionally,this simple,sensitive sensor was proved to be suitable for the determination of hyperin in Chinese herb Hypericum Perforatum with satisfactory results.?2?Based on the first system,the PDDA-Gr showed excellent electrical conductivity and large surface area,in order to improve the performence of the sensor,well dispersed titanium dioxide nanoparticles on poly?diallyldimethylammonium chloride?-functionalized graphene?TiO₂-PDDA-Gr?nanocomposites were successfully synthesized via a facile and green strategy.The simultaneous reductionof grapheme oxide?GO?and formation of TiO₂ to produce the TiO₂-PDDA-Gr were achieved under mild reaction conditions with the green reducing agent,PDDA.A sensitive voltammetric sensor based on TiO₂-PDDA-Gr modified glassy carbon electrode was constructed and used in establishing electroanalytical method for determination of esculetin.Under the optimized conditions,a lower detection limit of4×10^-9mol L^-1?S/N=3?and a wide linear detection range from 1×10^-8to 3.5×10^-6mol L^-1 were achieved by differential pulse voltammetry?DPV?.Additionally,this simple,sensitive sensor was proved to be suitable for the determination of esculetin in Chinese herb Viola yedoensis Makino and Cortex Fraxini.?3?According to the first system and second system,the PDDA-Gr combine with metal oxide was proven to be excellent electrical conductivity and large surface.Ti and Zr belong to the same family,the Zr O₂-PDDA-Gr was prepared by the same method of the second system and it was proved to be an excellent probe for electrochemical sensing toward Diosmin.The electrochemical characteristics of Diosmin were studied in detail and dynamics parameters of electrode process were also calculated to discuss the reaction mechanism.Under the optimized conditions,a lower detection limit of 2×10^-9 mol L^-1?S/N=3?and a wide linear detection range from 5×10^-9to 2×10^-6mol L^-1were achieved by differential pulse voltammetry?DPV?.Additionally,this simple,sensitive sensor was used in determination of Diosmin in lemon leaves and tablets with satisfactory results.