Luminomagnetic core-shell nanoparticles for detection of metallic ions

In this work, luminomagnetic core-shell nanoparticles of Fe3O4@SiO2@RhB@SiO2 were prepared aimed their application as nanosensor for Cu2+. For this purpose, the size of magnetic core (MNps) and thickness of SiO2 shell were modulated and their influence on the luminescent properties were investigated. PEG-assisted solvothermal method was used to prepare the MNps. PEG 4000, PEG 8000 and PEG 20000 were used as surfactants in the solvothermal method, producing MNPs of 145, 107 and 97 nm, respectively. The modified Stöber method was used to deposit the silica on the MNPs. Two different concentrations of TEOS, Fe3O4 and NH4OH were used, following the ratios of reagents described in the literature[1]. These coatings were named as FeSi4K_100, FeSi4K_50, FeSi8K_100, FeSi8K_50, FeSi20K_100 and FeSi20K_50. The effect of dilution was verified and TEM analysis showed silica coated nanoparticles with relative uniform size distribution. Fe3O4@SiO2 nanoparticles exhibited suitable magnetic response, facilitating their separation from reaction media. Rhodamine B (RhB), a fluorescent complexing agent and enable to response to Cu2+, was deposited on core-shell nanoparticles via modified microemulsion-assisted[2]. Diluted nanoparticles dispersions showed a fluorescent emission band characteristic around 572 nm under excitation at 495 nm. Experiments with Cu2+ (fluorescence quenching) were carried out with FeSi4K_100, FeSi8K_100 and FeSi20K_100 functionalized with RhB, showing changes in the emission band.