Organic Molecules Detected By Electrochemical Sensors With Different Dimensional Composites

Composite materials were composed of various materials to improve their properties.In composite materials,a portion was substrate and the other were reinforcements.In this research,three different kinds of electrochemical sensors were constructed based on composite materials with different dimensions and they were applied to determinate several pharmaceutical molecules in real samples.The main contents were listed as follows:1.Caffeic acid(CA)and ferulic acid(FA),as the simple phenolic acids,widely existed in plants and food.In this experiment,graphite-like carbon nitride(g-C3N4)was synthesized by direct heat method and it was applied to determinate CA and FA in food samples with chitosan(C.S).X-Ray diffraction(XRD),ultraviolet visible spectrophotometer(UV-vis),transmission electron microscope(TEM)and near infrared spectroscopy(NIR)illustrated that g-C3N4 was synthesized successfully and had a unique two-dimensional structure.Cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)were used to study the electrochemical activity of g-C3N4/CS/GCE.In acetate buffer solution(ABS,0.1 mol/L,pH=4.5),the modified electrode was proved to have a sensitive response to CA and FA in the range of 1～30 μg/mL and 5-30 μg/mL with the detection limits(LOD)of 0.354 μg/mL and 4.964 μg/mL(S/N=3)by differential pulse voltammetry(DPV).This method could also be used for determination of CA and FA in environmental water,coffee,tea and fruit juice.The results were consistent with high performance liquid chromatography(HPLC).The electrochemical method showed satisfactory results and provided a new approach to determinate phenolic acids with many advantages,such as rapid response,easy operation,low cost and highly sensitive.2.GMDA-AuNPs was successfully prepared based on three-dimensional macroporous adsorption resin(GMDA)and gold nanoparticles(AuNPs)by ultrasound.Particle size analysis,XRD,TEM and others were used to study the size of AuNPs and prove that the material had been successfully synthesized.GMDA-AuNPs were immobilized on glassy carbon electrode and the electrochemical behavior of these modified electrodes were study by CV and EIS.Differential pulse stripping voltammetry(DPSV)was utilized to detect sulfadiazine sodium(SD-Na)in phosphate buffer solution(PBS,0.01 mol/L,pH = 7.5).The result showed that the peak currents of SD-Na had positive correlation with the concentrations in the range of 1～30 μg/mL and LOD was 1.058 μg/mL.The method had good stability and specificity and could be used to detect sulfadiazine sodium in veterinary drugs.3.This research developed a novel electrochemical sensor for determination of chloramphenicol(CAP)in aqueous solutions.The working electrode was fabricated by carboxylic short-chain multi-wall carbon nanotubes(Short-MWNTs-COOH)and silver nanodendrites(AgNDs)based on glass carbon electrode(GCE).Scanning electron microscope(SEM)showed that AgNDs had a three-dimensional dendritic structure and EIS illustrated that Ag nanoparticle had been electrodeposited on modified electrodes successfully.Then,experimental parameters,such as pH,scan,deposition potential and time,were optimized by CV and linear sweep stripping voltammetry(LSSV).Under these optimized conditions,the experiment revealed satisfactory results to detect CAP in the range of 0.3～229 μmol/L and LOD(S/N=3)was 0.049 μmol/L.Compared with HPLC,this sensor had many advantages,such as easy operation,low cost and wide detection range,and had been applied to determinate CAP in real samples successfully.