An ultrasensitive and selective Schiff base modified silver nanoparticles-based probe for sensing of copper ions in aqueous medium

We have demonstrated the synthesis and characterisation of methyl (E)-1-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)-9 h-pyrido[3,4-b]indole-3-carboxylate (Schiff base) capped silver nanoparticle for selective monitoring of copper metal ions in water medium. The strategy relies on visual and spectroscopic investigation of copper ions sensing in water. Schiff base capped silver nanoparticles exhibit visual changes with copper ions because of immediate agglomeration of NPs which results in colour changes from orange to brown. In the UV-Visible spectrum, AgNPs exhibited a red-shift of surface plasmon resonance (SPR) band from 444 nm to 799 nm. Our sensing technique is distinct and does not require massive and costly set-up since sensing may be performed visually with naked eye. Moreover, this strategy can detect the copper ions in water with the detection limit of 2.309 × 10⁻⁵ M (0.146 ppm) which is less than the prescribed 3.0 ppm maximum permissible limit of copper ions in drinking water, according to the WHO guidelines. SEM and TEM analysis recorded the morphology and structural features of AgNPs. UV-Visible absorption spectroscopy recorded the shift of the SPR band during the sensing of copper ions. This approach is effective for sensing copper ions in real water samples. As a result, our technique paves the way for the implementation of real-time copper ions sensing in water sources.