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.

Tremendous developments in electrochemical immunosensors have facilitated cost‐effective, rapid and robust detection of many analytes. Among the significant developments, electrochemical immunosensors capable of simultaneously detecting several analytes have begun to emerge. In addition, recent progress in materials science and engineering has yielded nanostructured materials of various geometries that were readily exploited to provide a compatible medium for many biomolecules in immunoassays. Applications of these nanostructured materials to electrochemical immunosensor developments have significantly improved sensor performance in terms of their electrical, chemical and transport properties. This review provides a survey of innovative immunosensor developments involving a range of nanomaterials exploited in designing sensing platforms and efficient detection markers to achieve substantial signal amplifications and thereby outstanding detection characteristics.

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Key indicatorsSingle-crystal X-ray study T = 293 K Mean (C-C) = 0.008 Å R factor = 0.056 wR factor = 0.128 Data-to-parameter ratio = 12.4For details of how these key indicators were automatically derived from the article, see