Synthesis, characterisation and application of thiol-based spectroscopic and electrochemical sensors for detection of iron(III) in environmental samples - A DFT supported comparative study

In the present work, a thiol, 4-((4-hydroxybenzylidene)amino)-N-(4-mercaptophenyl)benzamide (HBMB) was synthesised and subjected to UV-visible measurements for assessing its sensing potential towards diverse metal ions. HBMB was found to exhibit sensitivity towards Fe3+ over a wide linear concentration range from 0.66 mu M to 38.46 mu M (r2 = 0.986 +/- 0.005) with a detection limit of 3.60 x 10-7 M. Electrochemical behaviour of HBMB was investigated using CV and DPV which displayed oxidation peaks at 1.01 V and 0.949 V, respectively. In DPV titration, HBMB exhibited sensitivity towards Fe3+ in a linear concentration range from 0.2 mu M to 5.56 mu M with a detection limit of 5.17 x 10-6 M. HBMB incorporating Fe3+-CPE was found to exhibit Nernstian slope of 18.3 mVdec-1 in the concentration range of 1.00 x 10-5 M - 1.00 x 10-1 M and detection limit of 3.98 x 10-6 M with a short response time of 10 s. DFT studies also confirmed HBMB-Fe3+ complexation with increase in HOMO-LUMO gap from 0.05 hartree to 0.14 hartree and negative binding energy of -0.013 hartree. Moreover, HBMB-based sensors was successfully applied for estimating Fe3+ content in different real samples of water, soil and food grains which could be extended to other samples of biological and environmental importance.