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 10–100nM with coefficient of regression R2=0.9993 and LOD of 3nM and sensitivity of 2.99μAnM−1cm−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 R2=0.9961. The LOD and LOQ values for amperometric detection were 4nM and 12nM, respectively with the sensitivity value of 10.81μAnMcm−2.