Rapid Detection of Metal Ions in the Aqueous Medium by Colorimetry and Surface Enhanced Raman Scattering Using Vanillic Acid-Coated Silver Nanoparticles

Abstract

Rapid and inexpensive detection of heavy metal pollution is highly required these days in order to combat pollution. Noble metal nanoparticles coated by organic molecules having surface plasmon resonance have recently played key role in conceptualizing and fabricating sensing devices for the detection of heavy metals. The present study uses the utility of vanillic acid coated silver nanoparticles (V-AgNPs) synthesized by chemical reduction for the colorimetric and surface-enhanced Raman scattering detection of heavy metal ions in aqueous solution. The synthesized V-AgNPs are of approximately 5–15 nm in size. The addition of synthesized V-AgNPs colloidal solution to control and metal ion laced water samples turns the solution color grayish black except for Cr(III) ions. The addition of V-AgNPs colloidal solution to the water samples containing Cr(III) ions turns the solution transparent. Furthermore, the addition of V-AgNPs to water samples containing Cr(III) ions and Mo(VI) creates unique Raman spectral signatures with high intensities that were used for the identification of these metal ions in aqueous solution. The addition of V-AgNPs to metal ions causes aggregation of the nanoparticles which results in change in color and Raman scattering signals. The obtained color patterns and Raman spectral signatures show the potential of V-AgNPs for low cost, timeless, affordable, convenient, sensitive, selective, and rapid detection of heavy metal ions in aqueous media.

Keywords:

• Colorimetry
• metal ions
• spectrophotometry
• surface enhanced Raman scattering (SERS)
• vanillic acid-coated silver nanoparticles

Acknowledgments

The authors are grateful to UGC, New Delhi, for providing financial assistance to create the confocal Raman microspectroscopy facility under the DST-FIST program to the Department of Physics, University of Allahabad, Allahabad. Ms Aarti Jaiswal and Ms Aparna Tiwari are also thankful to UGC, New Delhi for the financial assistance in form of scholarships.