Magnetic-metals sunflower nanocomposites for significant fluorescence enhancement

The surface enhanced fluorescence effect of metal-enhanced substrates has been intensively investigated. However, recent developments of fluorescence substrates based on novel composites have attracted much attention. In this paper, Ag@Fe₃O₄ nanocomposites with special sunflower structures were synthesized by a typical solvothermal method. The fluorescence enhancement of as-prepared substrates was able to be optimized by adjusting the concentration of fluorescent molecules and Ag@Fe₃O₄ within the appropriate range. Moreover, the calculated fluorescence enhancement factor reached 13.2 fold while the concentration of detected Rhodamine B was 10⁻⁶ mol/L and limit of detection was as low as 7.59 × 10⁻⁸ mol/L. The significantly enhanced fluorescence mainly resulted from great electromagnetic enhancement and good stability could derive from appropriate distance between the fluorescent molecules and Ag nanoparticles in these special nanostructures. Furthermore, the excellent recyclability was ascribed to fast and reversible magnetic response of Fe₃O₄ nanoparticles surrounding the surface of Ag core. Therefore, sensitive and reproducible magnetic-metal substrates were obtained for efficient fluorescence detection.