Gel-limited synthesis of dumbbell-like Fe₃O₄–Ag composite microspheres and their SERS applications

Abstract

A novel gel-limited strategy was developed to synthesize dumbbell-like Fe3O4-Ag composite microspheres through a simple one-pot solvothermal method. In such a reaction system, a special precursor solution containing oleic, water, ethanol and silver ions was used and transformed into a bulk gel under heating at the very beginning of the reaction, thus all the subsequent reactions proceeded in the interior of the gel. The gel-limited reactions had two advantages, on the one hand, the magnetic Fe3O4 microspheres were fixed in the gel which avoided them aggregating together, whereas on the other hand, the silver ions stored in the gel could be gradually released and tended to diffuse towards the nearest Fe3O4 microsphere, which favored the generation of a dumbbell-like Fe3O4-Ag structure. From the time-dependent experiments under optimal conditions, the typical growth process of dumbbell-like structures clearly demonstrated that a silver seed first appeared on the surface of a single Fe3O4 microsphere, which then grew bigger slowly and finally formed a dumbbell-like Fe3O4-Ag structure. Moreover, the formation of the gel was found to be strongly affected by the ratio of water and ethanol in the precursor solution, which further influenced the morphologies of the Fe3O4-Ag microspheres. Furthermore, the effect of lattice match between Fe3O4 and Ag on the final products was also proven from the control experiments by using a template with a different surface crystalline structure. When used as SERS substrates, the final dumbbell-like Fe3O4-Ag microspheres show fast magnetic separation and the selective detection of thiram for the surface capped oleic chain during the growth process.

Highly Efficient, Low-Cost, and Magnetically Recoverable FePt–Ag Nanocatalysts: Towards Green Reduction of Organic Dyes

“…From the TEM images of FePt–Ag 5 mg–60 mL and FePt–Ag 10 mg–60 mL, Ag seeds are found to be coherent with FePt nanocrystals owing to the effect of the two chelating sulfur groups provided by the PEI-DTC polymers. It is commonly known that the brightness in the TEM image reflects the ability of the transmitted electrons from the different substances and is proportional to the atomic number of the substances [ 62 ]. Unfortunately, because both FePt and Ag nanocrystals have high atomic numbers, it is hard to distinguish the two nanomaterials from TEM images.…”

Recent Novel Hybrid Pd–Fe3O4 Nanoparticles as Catalysts for Various C–C Coupling Reactions

“…Several attempts have been taken to design new hybrid nanocomplexes with well-defined multicomponents by controlling the size and shapes of these materials through solution growth structure [89][90][91]. Nasrollahjadeh et al [4] reported on the eco-friendly synthesis of Pd/Fe 3 O 4 NPs using Euphorbia condylocarapa M. bieb root extract and applied as a magnetically recyclable catalyst for Suzuki and Sonogashira coupling reaction.…”

Polyethyleneimine-mediated seed growth approach for synthesis of silver-shell silica-core nanocomposites and their application as a versatile SERS platform

“…As illustrated in Scheme 1a, the target analyte with specic affinity could be enriched with SiO 2 @PEI@Ag NPs; the formed complexes were separated by centrifugation and dropped on a silicon chip for SERS measurement. We detected the Raman signals of trace thiram, a widely used sulfur-containing fungicide, 37,38 to prove the practicability of the SiO 2 @PEI@Ag NPs. The Raman mapping of the thiram at the 1383 cm À1 band conrms the good reproducibility and reliability of Raman detection with SiO 2 @PEI@Ag NPs as SERS substrate (Fig.…”