Preparation Of A Novel Graphite-like Carbon Nitride Electrode And Its Application For Determination Of Cadmium

Cadmium is a heavy metal element with severe poisonous, and it holds a great threat tohuman beings and other living things, so that it is significant to establish a rapid, convenient,viable and effective method to detect cadmium. Compared with other tradional detectionmethods, electroanalysis is applied widely due to the advantages of high sensitivity, low costand easy sample operation and so on. Since bismuth film electrodes owned considerableperformance over mercury film electrodes, it has been occupied an important role in theelectroanalysis of heavy mental ions. In this thesis, cadmium(II) was detected by the squarewave anodic stripping voltammetry based on graphite like carbon nitride modified electrodes,and the main points are summarized as follows:1. g-C3N4was successfully prepared by thermal polycondensation of melamine. Themorphology and composition of the prepared samples were characterized by X-ray diffractionand scanning electron microscopy. The prepared g-C3N4exhibits well crystallinity, sheet-likestructure and agglomerate into large particles. The electrode coated with g-C3N4and Nafioncomposite film performs higher response current than the bare glassy carbon electrode.Accumulation potential, deposition time, pH and film thickness were investigated. Under theoptimal conditions, the current response of the g-C3N4/Nafion film modified electrodetowards the determination of Cd(II) is linear in the range of0.1-14μmol·L-1(R=0.9985), andthe sensitivity is8.03×106μA·mol-1·L with a detection limit of3.3×10-8mol·L(signal/noise=3). The g-C3N4/Nafion film also exhibits anti-interference property, remarkablestability, reproducibility and this electrochemical sensor was also applied to determine tapwater samples.2. In situ plating Bi film method was used in g-C3N4/Nafion composite film modifiedelectrode to determine Cd(II). The electrode in situ plating Bi shows better response than theone without plating Bi film under the same experimental conditions. Concentration ratio ofBi(III) towards Cd(II), accumulation potential, deposition time, pH and film thickness wereinvestigated. Under the optimal conditions, the current response of the g-C3N4/Nafion filmmodified electrode with in situ plating Bi film towards the determination of Cd(II) is linear inthe range of0.1-10μmol·L-1(R=0.9983), and the sensitivity is17.74×106μA·mol-1·L with a detection limit of5.84×10-9mol·L (signal/noise=3).3. CNTs/g-C3N4composites were prepared by ultrasonication of g-C3N4and then mixed withCNTs. The morphology of the prepared composites was characterized by X-ray diffractionand scanning electron microscopy. The expetimental results indicate that the current responseof the CNTs/g-C3N4electrode is superior to bare glassy carbon electrode and g-C3N4electrodefor Cd2+detemination. Under the optimal conditions, the current response of the CNTs/g-C3N4film modified electrode to Cd(II) is linear in the range of0.5-12.0μmol/L (R=0.9945), andthe sensitivity is8.59×106μA·mol-1·L with a detection limit of2.2×10-8mol·L-1(signal/noise=3). The CNTs/g-C3N4film also exhibits anti-interference property, remarkablestability, reproducibility. It is favorable for practical applications and available forsimultaneous detection of other metal ions.