Authors: Ali, AH; Diaz, I; Tsegaye, AA; Mengesha, AT

Acta Chem. Iasi. vol: 30. page: 2067-2438.
Date: . 2022.
Doi: 10.47743/achi-2022-1-0003.

The increasing of toxic heavy metal and nitrate ions contamination in water and food systems worldwide has become a core problem. Therefore, the development of real-time, highly sensitive and selective, simple technique for nitrate and toxic heavy metals ions (mercury, copper and arsenic) detection in water and food at ultralow concentrations are important for maintaining their safe deliveries to consumers. A highly efficient fluorescent chemosensor-based on polyaniline supported g-C3N4/CeO2 nanocomposite for selective heavy metal and nitrate ions have been successfully developed in this research, by in situ polymerization method. The structural, morphological, and optical properties of the 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 (3.25×10(4) M-1) compared to 8.12 x 10(3) M-1, 2.93 x 10(4) M-1 and 3.19 x 10(2) M-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 ions determination in Coca-cola, tap water, milk and lettuce samples respectively, were also applied. The amounts of mercury and nitrate concentrations measured in milk and lettuce were 56.66 mu M and 3.18 mM, exceeding the allowable limits stated by WHO (0.1 mu M for mercury and 5.9 mu M for nitrate, respectively)..