Fe3O4–Ag Janus composites were synthesized using a two-step solvothermal method. The optimal growth process was determined by investigating the relationship between the particle morphologies and reaction time. Magnetic and Raman spectroscopic measurements showed that the as-synthesized Janus composites have both good magnetic response and significant surface-enhanced Raman scattering (SERS) effects, as well as reproducibility. The calculated Raman enhancement factor reached an unprecedented magnitude of 109 compared with the values of other Fe3O4–Ag compounds. Furthermore, the SERS effect was exhibited even at a concentration of probe molecules as low as 10−13 M. This demonstrates that the as-synthesized Fe3O4–Ag Janus composite particles have promise for application as separable, highly sensitive SERS substrates.
A novel Au NPs/GeO 2 nanozymes are developed as Surface-Enhanced Raman Scattering (SERS) substrates with the promising prospect for detection ChI. Herein, it is discovered that both Au NPs and GeO 2 nanozymes have peroxidase-like activity, catalyzing colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to produce blue TMB ox . Interestingly, compared with single Au NPs or GeO 2 nanozymes, the Au NPs/GeO 2 nanozymes show stronger peroxidase-like activity, and significantly ameliorated SERS signal of TMB ox . The mentioned two enhancements are ascribed to a positive synergistic function of Au NPs/GeO 2 nanozymes. Surprisingly, choline iodide (ChI) can inhibit the positive synergy in Au NPs/GeO 2 nanozymes, and slow down the reaction of TMB-H 2 O 2 -Au NPs/GeO 2 system. On this foundation, a new Au NPs/GeO 2 SERS technique with high sensitivity, label-free detection method of choline iodide (ChI) is established, suggesting that Au NPs/GeO 2 nanozymes have the potential application of water environment.
The Surface-enhanced Raman scattering (SERS) effect on the surface of metal conductors can significantly improve the sensitivity of molecular detection. Therefore, it is widely used in the field of chemical sensors. The nanostructure of the metal surface strongly influences the strength of the SERS by adsorption and surface electric field. Herein, we combine microfluidic technology with electroless silver plating to produce hollow microspheres with different wall thicknesses. The microspheres have a diameter of 400 μm and a spherical shell thickness of 40–100 μm. The spherical shell has a porous structure formed by phase separation, on which nanosilver particles can be deposited. The silver-polymer hybrid microspheres can adsorb dyes in aqueous solution and produce significant SERS effects, and the Raman signal enhancement factors can be up to 7.11 × 10 11 . Computational simulations and experimental results show that the Raman enhancement effect is related to the distance between the silver particles on the surface and the hollow structure of the microspheres.
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