Selective Colorimetric Detection of Mn²⁺ and Cr²⁺ Ions using Silver Nanoparticles Modified with Sodium Dodecyl Sulfonate and -Cyclodextrin

The present study was conducted to determine manganese (Mn2+) and chromium (Cr2+) ions in aqueous systems with a simple, rapid, sensitive, selective and cost-effective colorimetric approach. Sodium dodecyl sulfonate (SDS) and beta-cyclodextrin (CD) were used as both stabilizer and surface functionalizing agents for the synthesis of silver nanoparticles (AgNPs). Synthesized AgNPs were characterized by FT-IR spectroscopy, UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and dynamic light scattering (DLS) techniques. The effect of pH on the stability of nanoparticles was investigated. SDS modified silver nanoparticles (SDS-AgNPs) and SDS with beta-cyclodextrin modified silver nanoparticles (SDS-CD-AgNPs) demonstrated sensitive and selective colorimetric detection of Mn2+ and Cr2+ ions at ppm level, respectively. The prepared SDS-AgNPs and SDS-CDAgNPs solution showed a color change visible to the naked eye from yellow to orange upon adding Mn2+ and Cr2+ ions, respectively; however, other metal ions did not induce such a change. In addition, the results of SEM TEM and DLS" for both sensors showed the aggregation of nanoparticles after adding Mn2+ or Cr2+. Overall, the results of this study show the successful synthesis of AgNPs, SDS-AgNPs, and SDS-CD-AgNPs as simple, rapid, sensitive, selective colorimetric sensors with high potential for rapid and on-site detection of Mn2+.