In situ preparation of Tricholoma mushroom polysaccharide-g-poly(N,N-dimethyl acrylamide-co-acrylic acid)–CuO composite nanoparticles for highly sensitive and selective sensing of Th4+ in aqueous medium

Abstract

Herein, we report for the first time the highly sensitive and selective sensing of Th⁴⁺ in aqueous solution, using mushroom polysaccharide-based graft copolymer–CuO composite nanoparticles (TMP–CuO NPs), by optical, colorimetric and electrochemical methods. The graft copolymer was prepared in water by a solution phase radical polymerization technique using Tricholoma mushroom polysaccharide (TMP) with a mixture of N,N-dimethyl acrylamide (DMA) and acrylic acid (AA) in the presence of potassium peroxydisulphate (K₂S₂O₈) as the radical initiator. The graft copolymer was characterized by ¹H NMR and FTIR spectroscopy, and FESEM analysis. The TMP–CuO NPs were characterized by UV-visible and FTIR spectroscopy, XRD, EDAX, HRTEM, FESEM, and DLS analyses. The prepared TMP–CuO NPs have unique properties for the sensing of Th⁴⁺ in water medium, which were investigated by optical, colorimetric and electrochemical methods. The UV-absorption spectra showed a significant redshift of the localized surface plasmon (LSPR) band (λ_max) with a gradual decrease in the absorption intensity upon each addition of Th⁴⁺ into the TMP–CuO NPs medium. Also, the reddish brown colour of the TMP–CuO NPs solution changed to colourless after the addition of a certain concentration of Th⁴⁺ ions. Electrochemical studies for the sensing of Th⁴⁺ by cyclic voltammetry showed a clear reduction peak at 1.009 V. The selective detection of Th⁴⁺ in water medium was also investigated in the presence of some environmentally relevant metal ions by using optical and colorimetric analysis. The morphological changes of TMP–CuO NPs in the presence of trace amounts of Th⁴⁺via the formation of the CuO–Th amalgam was confirmed by XPS, XRD, FTIR, FESEM, and EDAX analysis.