Surface-Enhanced Raman Detection of Low-Concentration Methylene Blue Using Nanoparticles Functionalized with 12-Mercaptododecanoic Acid

Abstract

The development of sensitive and magnetically recoverable SERS substrates is of interest for the detection of organic pollutants at low concentrations. In this study, Fe3O4-СА@Au-12-MDA nanoparticles were synthesized for use as a SERS substrate in the detection of methylene blue dye within a concentration range of 10-2-10-7 M. The Fe3O4 magnetic nanoparticles were modified with citric acid, followed by gold deposition and surface functionalization with 12-mercapto-dodecanoic acid. The stepwise modification of the nanoparticles was confirmed by FTIR, SEM-EDX and XRD, which revealed the presence of Au and organic functional groups whilst preserving the crystalline structure of Fe3O4. The Fe3O4-СА@Au-12-MDA-based SERS substrate exhibited signal enhancement compared to conventional Raman spectroscopy. For the characteristic bands at 1623 and 1396 cm-1, the approximate EF values reached 0.11×105 and 0.15×105, respectively, corresponding to 5.95- and 5.40 times signal enhancement. The estimated LOD values calculated using the 3σ criterion were 4.05×10-8 and 5.97×10-8 M for the respective bands. The calibration curves demonstrated good linearity with R2 values of 0.94-0.99 for SERS measurements. The results obtained demonstrate the potential of Fe3O4-СА@Au-12-MDA nanoparticles a magnetic SERS platform for the detection of low concentrations of organic dyes.