Ternary noble metal–semiconductor nanocomposites (NCs) with core–shell–satellite nanostructures have received widespread attention due to their outstanding performance in detecting pollutants through surface-enhanced Raman scattering (SERS) and photodegradation of organic pollutants. In this work, ternary Au@Cu2O–Ag NCs were designed and prepared by a galvanic replacement method. The effect of different amounts of Ag nanocrystals adsorbed on the surfaces of Au@Cu2O on the SERS activity was investigated based on the SERS detection of 4-mercaptobenzoic acid (4-MBA) reporter molecules. Based on electromagnetic field simulations and photoluminescence (PL) results, a possible SERS enhancement mechanism was proposed and discussed. Moreover, Au@Cu2O–Ag NCs served as SERS substrates, and highly sensitive SERS detection of malachite green (MG) with a detection limit as low as 10−9 M was achieved. In addition, Au@Cu2O–Ag NCs were recycled due to their superior self-cleaning ability and could catalyze the degradation of MG driven by visible light. This work demonstrates a wide range of possibilities for the integration of recyclable SERS detection and photodegradation of organic dyes and promotes the development of green testing techniques.

Au@Cu2O core-shell nanocomposites (NCs) were synthesized by reducing copper nitrate on Au colloids with hydrazine. The thickness of the Cu2O shells could be varied by adjusting the molar ratios of Au: Cu. The results showed that the thickness of Cu2O shells played a crucial role in the catalytic activity of Au@Cu2O NCs under dark condition. The Au@Cu2O-Ag ternary NCs were further prepared by a simple galvanic replacement reaction method. Moreover, the surface features were revealed by TEM, XRD, XPS, and UV–Vis techniques. Compared with Au@Cu2O NCs, the ternary Au@Cu2O-Ag NCs had an excellent catalytic performance. The degradation of methyl orange (MO) catalyzed by Au@Cu2O-Ag NCs was achieved within 4 min. The mechanism study proved that the synergistic effects of Au@Cu2O-Ag NCs and sodium borohydride facilitated the degradation of MO. Hence, the designed Au@Cu2O-Ag NCs with high catalytic efficiency and good stability are expected to be the ideal environmental nanocatalysts for the degradation of dye pollutants in wastewater.

In this work, a molecularly imprinted polymer (MIP)-based SERS sensor for selective, sensitive, quantitative, and recyclable detection of paclobutrazol residues in complex environments has been proposed. In this strategy, Fe3O4@SiO2–Au@Ag (FSAA) nanocomposites with tunable Au@Ag interparticle gaps are constructed. Then, by tuning the Au@Ag nanogaps and investigating the SERS enhancement mechanism of FSAA, we achieve the optimal SERS substrate, FSAA-40. After combining with MIPs, we can selectively detect paclobutrazol in soil with a detection limit of 0.075 μg/g. When the paclobutrazol concentration ranges from 0.075 to 12.75 μg/g, the SERS intensity shows a linear correlation, which opens the possibility for quantitative detection. Our magnetic MIP-based SERS sensor can be easily separated, efficiently recycled, and expanded to more universal environments, which demonstrates a promising future in food and environmental safety.

The Fe3O4@Au core–shell nanocomposites, as the multifunctional magnetic surface enhanced Raman scattering (SERS) substrates, were fabricated successfully by the seeds growth method based on the Fe3O4–Au core-satellite nanocomposites. The SERS properties of the Fe3O4–Au core-satellite nanocomposites and the Fe3O4@Au core–shell nanocomposites were compared using 4-aminothiophenol (4-ATP) as the probe molecule. It was found that Fe3O4@Au core–shell nanocomposites showed better SERS performance than Fe3O4–Au core-satellite nanocomposites. The Au shell provided an effectively large surface area for forming sufficient plasmonic hot spots and capturing target molecules. The integration of magnetic core and plasmonic Au nanocrystals endowed the Fe3O4@Au core–shell nanocomposites with highly efficient magnetic separation and enrichment ability and abundant interparticle hot spots. The Fe3O4@Au core–shell nanocomposites could be easily recycled because of the intrinsic magnetism of the Fe3O4 cores and had good reproducibility of the SERS signals. For practical application, the Fe3O4@Au core–shell nanocomposites were also used to detect thiram. There was a good linear relationship between the SERS signal intensity and the concentration of thiram from 1 × 10−3 to 1 × 10−8 M and the limit of detection was 7.69 × 10−9 M. Moreover, residual thiram on apple peel was extracted and detected with a recovery rate range of 99.3%. The resulting substrate with high SERS activity, stability and strong magnetic responsivity makes the Fe3O4@Au core–shell nanocomposites a perfect choice for practical SERS detection applications.

In this study, the three-dimensional (3D) flowerlike porous Fe 3 O 4 microcrystals were prepared by a self-assembly approach with the assistance of ethylene glycol (EG). The generation mechanism of the 3D flowerlike Fe 3 O 4 microcrystals was revealed through controlling the parameters of the hydrothermal reaction time, the molar mass of the urea, and the calcination temperature. The proposed 3D flowerlike Fe 3 O 4 microcrystals exhibited superparamagnetic behaviors with high saturation magnetization (i.e., up to 73.1 emu• g −1 ) at room temperature. The Fe 3 O 4 −Au magnetic composites (MCs) were further prepared by a seed deposition process, and surface features were revealed by TEM, XRD, XPS, UV−vis, and SQUID techniques. Compared with the Fe 3 O 4 microcrystals themselves, the Au (∼20 nm) covered Fe 3 O 4 microcrystals provided efficient and recyclable catalytic performance (e.g., unprecedented high turnover frequency of 2.874 min −1 ) for 4-nitrophenol (4-NP). More importantly, the proposed Fe 3 O 4 −Au MCs could be used to reduce 4-NP for more than six cycles, elaborating that Fe 3 O 4 −Au MCs are promising catalysts in the field of environmental purification.