Ni-sinapic acid nanocomposite in the selective sensing of permanganate ions

Abstract

A polyphenolic acid assisted synthesis of Ni nano particles for absorption spectrophotometric sensing of MnO4- ions in micro molar range is reported here. The synthesis was carried out using a green approach where sinapic acid acts as a capping agent. The synthesized nano particle was then characterized using UV–Vis spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, powder X-ray diffraction analysis, X-ray photoelectron spectroscopy. The particle size is around 5 to 10 nm with the presence of both porosity and nano crystallinity as obtained from the transmission electron microscopic analysis. This nano particle can selectively sense permanganate ions in presence of different co-existing ions with the limit of detection (LOD) 0.413 µM. The sensing mechanism was examined with the isothermal titration calorimetry (ITC) and X-ray photoelectron spectroscopy (XPS). Isothermal titration calorimetric data suggests that the interaction between permanganate and the nano particle is enthalpy driven process with ΔH and ΔG values are −80 kcal/mol and −5.72 kcal/mol respectively. XPS data confirmed the presence of Ni(II) ions in the Ni-SA NPs and the atomic percentage of the same differed in presence of KMnO4. There was no significant interference from the contemporary ions and even in the presence of Mn2+ ion. The method has also been applied for the natural water samples and for vegetable. ∼ 88 to 108 % of the added KMnO4 could be recovered from the tap water sample using our prepared methodology. The limit of detection and the present technique are compared with the previously reported literature and have been found to be comparable, even in solvent-free conditions and using simple instrumentation.