Detection of Zn Water Pollution by a Biosensor Based on Alkaloids Derived from Iraqi Catharanthus Roseus

Abstract

     In this work, the detection of zinc (Zn) ions that cause water pollution is studied using the CSNPs- Linker-alkaloids compound that was prepared by linking extracted alkaloids from Iraqi Catharanthus roseus plant with Chitosan nanoparticles (CSNPs) using maleic anhydride. This compound is characterized by an X-ray diffractometer (XRD) which shows that it has an orthorhombic structure with crystallite size in the nano dimension. Zeta Potential results show that the CSNPs-Linker-alkaloids carried a positive charge of 54.4 mV, which means it possesses high stability.  The Fourier transform infrared spectroscopy (FTIR) shows a new distinct band at 1708.93 cm^-1 due to C=O esterification. Scanning electron microscope (SEM) images show that the CSNPs- Linker- alkaloids compound have two shapes in the nano dimension: spherical particles and nanotubes, which may be due to nuclei and growth processes, respectively. The energy gap calculated from the photoluminescence spectrum is equal to 2.5 eV.  The Hall effect measurements prove that the synthesized CSNPs- Linker-alkaloids compound is a p-type semiconductor. The cycle voltammetry technique was used to detect the Zn ions in different concentrations in the water by modifying the electrochemical system's glassy carbon electrode (GCE) with a CSNPs-Linker-alkaloids compound. The modified electrode was used to detect Zn ions in the range of (1-8) ppm, which causes water pollution. The best sensor sensitivity R² equals 0.997 for oxidation and 0.993 for reduction. This modified electrode (GCE /CSNPs- Linker-alkaloids) acts as a good biosensor for heavy metals detection in water as well as for biophysics applications.