Nanocomposites containing embedded superparamagnetic iron oxide nanoparticles and rhodamine 6G

Abstract: Bifunctional nanocomposites possessing superparamagnetism and traceability with optical methods were prepared. The superparamagnetic properties were achieved by introducing highly concentrated, ca. 13nm-sized maghemite (γ-Fe2O3) nanoparticles into a silica matrix based on tetraethylorthosilicate (TEOS) and bis-1,2-(triethoxysilyl)ethane (BTSE). Traceability was attained by simultaneously incorporating a small amount of rhodamine 6G fluorescent dye into the same silica matrix. Agglomeration of the highly concentrated maghemite nanoparticles during the preparation procedure was prevented by pre-coating them with a 1–2nm thick silica layer. The nanocomposites exhibited a relatively high magnetization of ∼20emu/g. Superparamagnetism was demonstrated using ZFC and FC measurements. Although the presence of the nanoparticles modified the transparency of the pristine silica matrix, we show that the incorporated rhodamine 6G exhibits a well-resolved, blue-shifted peak in the fluorescence spectrum, with a maximum at about 552nm. The bifunctionality of the present nanocomposites could be interesting for the preparation of similar materials for biomedical applications. [Copyright &y& Elsevier]