Recent advances in the fluorimetric and colorimetric detection of cobalt ions.

Cobalt is an essential metal to maintain several functions in the human body and is present in functional materials for numerous applications. Thus, to monitor these functions, it is necessary to develop suitable probes for the detection of cobalt. Presently, researchers are focused on designing different chemosensors for the qualitative and quantitative detection of the metal ions. Among the numerous methods devised for the identification of cobalt ions, colorimetric and fluorimetric techniques are considered the best choice due to their user-friendly nature, sensitivity, accuracy, linearity and robustness. In these techniques, the interaction of the analyte with the chemosensor leads to structural changes in the molecule, causing the emission and excitation intensities (bathochromic, hyperchromic, hypochromic, and hypsochromic) to change with a change in the concentration of the analyte. In this review, the recent advancements in the fluorimetric and colorimetric detection of cobalt ions are systematically summarized, and it is concluded that the development of chemosensors having distinctive colour changes when interacting with cobalt ions has been targeted for on-site detection. The chemosensors are grouped in various categories and their comparison and the discussion of computational studies will enable readers to have a quick overview and help in designing effective and efficient probes for the detection of cobalt in the field of chemo-sensing.

Synthesis, Crystal Structure and Fluorimetric Study of 2-phenylphthalazin-1(2H)-one: a Highly Selective Florescent Chemosensor for Detection of Fe3+ and Fe2+ Metal Ions.

A ligand, 2-phenylphthalazin-1(2H)-one (K), was synthesized by refluxing 2-formylbenzoic acid with phenyl hydrazine in presence of ethanol. FTIR, elemental analysis and single crystal XRD techniques were used to elucidate the structure. Fluorimetric turn-off response was recorded when solution of ligand (K) in DMF was treated with aqueous solution of Fe3+ and Fe2+ metal ions. No specific changes were observed on addition of other metal ions (Pb2+, Cd2+, Mn2+, Zn2+, Ba2+, Ni2+, Al3+, Ag1+, Co2+, Ca2+, Cu2+, Mg2+, Cr3+). Limit of Detection (LOD) was calculated for Fe2 and Fe3+as 2.4 µM and 2.5µM respectively, which is quite below to the recommended value 5.4 µM of the Environment Protection Agency of USA. Association constants for Fe3+ and Fe2+ metal ions were determined as 6 × 10-4 M-1 and 3.6 × 10-4 M-1 respectively. Benesi-Hildebrand plot confirmed 1:1 binding ratio between metal ions and ligand.