Synthesis of Sensitive and Robust Lignin Capped Silver Nanoparticles for the Determination of Cobalt(II), Chromium(III), and Manganese(II) Ions by Colorimetry and Manganese(II) Ions by Surface-Enhanced Raman Scattering (SERS) in Aqueous Media

Abstract

Plasmonic nanoparticles functionalized by organic molecules appear to be a promising approach for developing detection systems for effective, simple, sensitive, selective, and cost-effective colorimetry and surface-enhanced Raman scattering (SERS) agents to generate characteristic color patterns and spectral fingerprints of metal ions for their identification and quantification in aqueous solution. In order to achieve this goal, silver nanoparticles functionalized with lignin(L-AgNPs) were synthesized by a microwave-assisted method and used for the determination of Co(II), Cr(III), and Mn(II) in aqueous solution using colorimetry and SERS. In the presence of the L-AgNPs colloidal solution, water samples containing Mn(II) ions turn black, while those containing Cr(III) ions become reddish brown. Moreover, in water samples with Co(II) ions, the addition of L-AgNPs solution leads to formation of a brown precipitate and the water samples become transparent. The ultraviolet-visible spectra of the Co(II)-, Cr(III)-, and Mn(II)-spiked water mixed with L-AgNPs colloidal solution show that these metal ions modify the localized surface plasmon resonance (LSPR) band of L-AgNPs which is caused by the aggregation induced by metal ions in the colloidal solution. The potential of the synthesized L-AgNPs colloidal solution has also been explored for SERS measurements of the metal ions. In the presence of L-AgNPs, significant enhancement in the Raman signal is observed for Mn(II) which is not seen in case of other metal ions showing its selectivity for this ion. The study is helpful in conceptualizing, designing, and fabricating nanoparticles for colorimetry- and SERS-based devices for metal sensing applications.

Keywords:

• Colorimetric detection
• heavy metals
• lignin-functionalized silver nanoparticles (L-AgNPs)
• surface-enhanced Raman scattering (SERS)

Additional information

Funding

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