Synthesis of 3D hierarchical Fe₃O₄/graphene composites with high lithium storage capacity and for controlled drug delivery

Three-dimensional (3D) hierarchical Fe₃O₄/graphene nanosheet (GNS) composites have been synthesized using a simple in situ hydrothermal method. Characterization shows that the Fe₃O₄ nanoflowers are highly encapsulated in a GNS matrix. The Fe₃O ₄/GNSs-1 nanocomposite (60 wt % of Fe₃O₄ in the composites) exhibits a stable capacity of ∼605 mAh g^-1 with no noticeable fading for up to 50 cycles in the voltage range of 0.001-3.0 V, and the superior performance of Fe₃O₄/GNSs-1 is clearly established by comparison of the results with those from Fe₃O ₄/GNSs-2 (23 wt % of Fe₃O₄ in the composites) and bare Fe₃O₄. In addition, another possible application of the drug delivery with the composites shows that the loading of rhodamine B (RB) on Fe₃O₄/GNSs increased linearly with the increase in the initial RB concentration, and the loading capacity of Fe₃O ₄/GNSs-1 was as high as 3.18 mg mg^-1. The excellent electrochemical performance of the composites and highly efficient loading of RB could be attributed to the enhanced electronic conductivity and the large surface areas of the Fe₃O₄/GNSs in which the hierarchical structure of Fe₃O₄ nanoflowers are highly encapsulated in the GNS matrix.