Synthesis and characterization of 4-Halobenzylidene malanonitriles for optical detection of Nickel (II) ions in aqueous solution.

In this work, we have developed fluorescent detection techniques for the determination of Ni2+ ions in aqueous medium with sensitivity using metal coordinating fluorescent molecules namely 4-Halobenzylidene malanonitrile. The halogen substituted benzylidene malanonitile were synthesised Knoevenagel condensation reaction of various halogen substituted aromatic aldehydes with malanonitrile and products were characterised by IR and NMR spectroscopy. The obtained benzylidene malanonitiles and are exhibited a fluorescent emission with a peak of 430 nm, 440 nm and 448 nm for chloro, bromo and fluoro substituted compounds, respectively. The intensity of optical emission of the studied molecules is increased proportional to the addition of Ni2+ ions. The effect of different halogen substitution on the fluorescence behaviour of benylidene malononitrile has also been investigated. The synthesised title compounds showed a lowest detection limit of 10-20 M for the Nickel (II) ions in aqueous solution under UV-Vis absorption spectra. The molecule 4- Bromobenzylidene malanonitrile exhibited a lowest detection limit of 10-19 M for the Nickel (II) ions in, aqueous solution, photoluminescence analysis.

PbS/graphene hybrid nanostructures coated glassy carbon electrode for the electrochemical sensing of copper ions in aqueous solution.

In this research, we have studied the electrochemical sensing of Cu(II) ions in aqueous solution using PbS/Graphene composite nanostructure coated glassy carbon electrode (GCE). The SEM-EDAX analysis revealed that the lead sulphide nanocrystals are homogeneously embedded on the graphene nanosheets with an uniform particle size of 100 nm, and the elements presents 92.32% and Lead content of 5.45% and Sulfur content of 0.91%. Raman spectra exhibits G with respect to the E2g sp2 hybridized C-C and D band with respect to the A1g mode in the disordered edge region of the GNS. The composite nanostructure coated GCE (PbS/Graphene/GCE) was prepared and its performance in the existence of metal ions such us Cd(II),Pb(II), Mg(II), Cu(II) and Ni(II) was studied using the current voltage curves in double distilled water within the scan rates of 25 to 300mVs-1. The PbS/Graphene coated carbon electrode exhibited the higher anodic and cathodic peak current for copper solution than the other metal ions studied, which various linearly proportional to concentration. The electrochemical sensing characteristics PbS/GNS/GCE was found to be significant towards detecting Cu2+ ion within the concentration range of 1 × 10-4 to 1 × 10-8 M, with a lowest sensing detection limit of 1 × 10-8 M.