Abstract:
The increasing of toxic heavy metal and nitrate ions contamination in water and food systems in worldwide has become a core problem. Therefore, the development of real-time, highly sensitive and selective, simple technique for detection of nitrate and toxic heavy metals ions (mercury, copper and arsenic) in water and foods at ultralow concentrations are important for maintaining safe water and food supplies. A highly efficient fluorescent chemosensor based on polyaniline supported g-C3N4/CeO2 nanocomposite for arsenic (III), copper (II), mercury (II) and nitrate ions were developed. Nanostructure polyaniline supported g-C3N4/CeO2 nanocomposite has been successfully synthesized by in- situ polymerization method. The structural and morphological as well optical properties of the as- synthesized nanocomposites were characterized by using powder X-ray diffraction (XRD), Fourier- Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Photoluminescence (PL) and UV-Vis spectroscopy. In the absence of metal and nitrate ions, the nanocomposites exhibit high fluorescence intensity. However, the strong coordination of the basic sites to metal and nitrate ions, causes fluorescence quenching via photoinduced electron transfer and static quenching leading to the qualitative and quantitative detection of metal and nitrate ions. This fluorescent chemosensor exhibits high selectivity toward arsenic (III), copper (II), mercury (II) and nitrate ion. The sensor was more sensitive for copper (II) ion than arsenic (III), mercury (II) and nitrate ions because the Stern-Volmer quenching constants (KSV) was found to be greater for copper (II) ion at (3.25x10 4 M -1) compared to 8.12x10 3M -1, 2.93x10 4 M -1and 3.19x10 2M -1 for arsenic (III), mercury (II) and nitrate ions respectively. The practical use of this sensor for arsenic (III), copper (II), mercury (II) and nitrate ion determination in Coca-cola, Tap water, Milk and Lettuce samples respectively, were also demonstrated. The obtained amounts of mercury and nitrate concentrations in milk and lettuce were 56.66 μM and 3.18 mM, which exceeded the allowable limit of 0.1 μM and 5.9 μM for mercury and nitrate contaminations respectively as stated by WHO.
