Synthesis and characterization of novel imine substituted phthalocyanine for sensing of l-cysteine

Abstract New mono-nuclear cobalt (II) tetra[4-(2-{(E)-[(4-bromophenyl)imino]methyl}phenoxy)] phthalocyanine (CoTBrImPc) complex has been synthesized for the first time in pure state. The synthesized dark blue coloured complex was characterized by elemental analysis, IR, UV–Vis, NMR, Mass, powder X-ray diffraction and thermogravimetric analysis (TGA) to understand the structural integrity, purity and crystalline property of the complex. The synthesized phthalocyanine complex was found to be electrochemically active and it was immobilized on the glassy carbon electrode by drop-casting method and used for the detection of l -cysteine. The CoTBrImPc modified electrode was found to be a good electrocatalyst for the catalytic oxidation of l -cysteine with shift in the overpotential towards less positive potential and an increase in the catalytic current compared to bare glassy carbon electrode (GCE). The linear response was observed for the voltametric detection of l -cysteine in the concentration range 10–100 nM with coefficient of regression R 2  = 0.9993 and LOD of 3 nM and sensitivity of 2.99 μA nM −1  cm −2 . The amperometric sensor was also developed for the detection of l -cysteine which showed linear response in the concentration range same as that of cyclic voltammertry technique with a linear equation y = 0.7582x + 16.9535 and correlation coefficient of R 2  = 0.9961. The LOD and LOQ values for amperometric detection were 4 nM and 12 nM, respectively with the sensitivity value of 10.81 μA nM cm −2 .