Nanocomposites containing embedded superparamagnetic iron oxide nanoparticles and rhodamine 6G

Bifunctional nanocomposites possessing superparamagnetism and traceability with optical methods were prepared. The superparamagnetic properties were achieved by introducing highly concentrated, ca. 13 nm-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 1–2 nm thick silica layer. The nanocomposites exhibited a relatively high magnetization of ∼20 emu/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 552 nm. The bifunctionality of the present nanocomposites could be interesting for the preparation of similar materials for biomedical applications.