Colorimetric and Surface Enhanced Raman Scattering (SERS) Detection of Metal Ions in Aqueous Medium Using Sensitive, Robust and Novel Pectin Functionalized Silver Nanoparticles

For maintaining water quality, planning remediation strategies and ecosystem restoration, the detection of metal ions in aquatic water bodies is very important. Colorimetry as well as plasmon-enhanced spectroscopy using plasmonic particles tailored and decorated by organic molecules provides promising simple, portable, robust and economically viable sensing systems for metal ions in field or in point of care settings. For this purpose, silver nanoparticles functionalized with pectin (P-AgNPs) have been synthesized by a microwave assisted method for the detection of metal ions [Cr(III), Cr(VI), Se(IV), Mn(II), Fe(II), As(V), and Hg(I)] in aqueous solution using colorimetry and SERS. The addition of P-AgNPs imparts a black and brown color to the water samples containing Fe(II) and Mn(II) ions while a reddish brown color is observed in water samples containing Cr(III) and As(V) ions. The Raman measurements of different concentrations of Cr(III), Cr(VI), Se(IV), Mn(II), As(V), and Hg(I) ions mixed with synthesized colloidal P-AgNPs solution have also been recorded. The addition of metal ions to the P-AgNPs solution induces alteration in the spectral features of the peaks of P-AgNPs. In addition, they also lead to formation of new characteristic bands. Significant enhancement in the intensity has been observed for these bands in the form of SERS signals. These peculiar characteristic peaks may be used for the detection of the metal ions in aqueous solution. This study demonstrates applicability of P-AgNPs as a colorimetric and plasmon enhancing spectroscopic agent for the simple, prompt, easily accessible and portable tool for the detection of metal ion pollution in aqueous medium.