Nanostructured Hematite Decorated with Gold Nanoparticles for Functionalization and Biocompatibility

Iron oxides have attracted the attention of researchers due to their abundance, low cost, low toxicity, and versatility of applications. According to the composition and crystalline structure, iron oxides may have characteristics of semiconductors and magnetic materials, such as hematite (alpha-Fe2O3) and magnetite (Fe3O4), respectively. The property of biocompatibility of hematite is essential to be applied in the construction of micro-/nanorobots (MNRs). Herein, the decoration of hierarchically structured core/shell Fe3O4/Fe2O3 microtubes and foils with gold nanoparticles (AuNPs) for functionalization and enhancement of biocompatibility that favor the use in MNR fabrication is presented. In this case, the synthesis of AuNPs takes advantage of the capacity of hematite to reduce Au3+ photochemically under excitation by a sunlight simulator. The yield of AuNPs covering the microtube surface is dependent on the gold salt concentration used for the synthesis. The AuNP-decorated hematite surfaces of the microtube and foil are functionalized with thiol poly(ethylene glycol) fluorescein, exhibiting increase in conductivity favored by irradiation with visible light. AuNPs also favor cell adherence and proliferation with the maintenance of mitochondrial transmembrane potential. Therefore, the hematite surface of the microtubes decorated with AuNPs is a promising material for the application in micro-/nanorobots and bioelectronics.