Detection of potentially toxic metals by SERS using salen complexes

Area of Science:

• Analytical Chemistry
• Environmental Science
• Materials Science

Background:

• Surface-enhanced Raman scattering (SERS) provides unique spectral fingerprints for discriminating between metal complexes.
• SERS offers a promising avenue for developing sensitive and straightforward methods for metal ion detection and quantification in solutions.
• Environmental monitoring of potentially toxic metals (PTMs) is crucial for public health and ecosystem safety.

Purpose of the Study:

• To utilize SERS for the detection and quantification of specific metal ions (Ni(II), Cu(II), Mn(II), Co(II)) in solution.
• To demonstrate the capability of SERS in identifying individual metal ions within a mixture using a single ligand and preparation method.
• To assess the limits of detection (LOD) for these metal ions and compare them with established water quality guidelines.

Main Methods:

• Complexation of Ni(II), Cu(II), Mn(II), and Co(II) with a salen ligand in solution.
• Acquisition and analysis of SERS spectra for each metal complex.
• Determination of the limit of detection (LOD) for each metal ion using the SERS method.
• Analysis of a contaminated water sample for Mn(II) concentration.

Main Results:

• SERS spectra exhibited distinct spectral differences for each metal-salen complex, enabling specific identification of Ni(II), Cu(II), Mn(II), and Co(II).
• The LODs for Ni(II), Cu(II), and Mn(II) were determined to be 1, 2, and 2 μg L⁻¹, respectively, which are below the WHO's recommended limits for drinking water.
• The LOD for Co(II) was 20 μg L⁻¹, with no WHO limit set due to typically low environmental concentrations.
• Mn(II) was detected at 800 μg L⁻¹ in a contaminated water sample.

Conclusions:

• SERS, utilizing the salen ligand, effectively discriminates and identifies multiple metal ions based on unique spectral fingerprints.
• The developed SERS method is sensitive enough to detect Ni(II), Cu(II), and Mn(II) below WHO recommended limits for drinking water.
• This approach provides a versatile and sensitive platform for the environmental monitoring of potentially toxic metals in aqueous samples.