Hierarchical conjugate structure of γ-Fe2O3 nanoparticles and PbSe quantum dots for biological applications

The development and characterization of a unique conjugated structure comprised of gamma-Fe2O3 nanoparticles (NPs) and PbSe nanocrystal quantum dots (NQDs), bonded via chemical functional groups, are discussed. Compatibility with an aqueous environment was rendered by exchanging the traditional organic surfactants (oleic acid) of the PbSe NQDs and gamma-Fe2O3 NPs with 2-aminoethanethiol and polyhedral silsesquioxane hydrate octakis ligands, respectively. Comparison of the transmission electron microscopy (TEM) images of the PbSe NQDs and gamma-Fe2O3 NPs capped with either organic or water-soluble ligands highlights the preservation of the morphology and size of both types of nanoclusters upon ligand exchange. Furthermore, the absorbance, photoluminescence (PL), and Fourier transform infrared spectra of the PbSe QDs revealed that the optical properties of the NQDs were retained during the surfactant exchange. High-resolution TEM images of the complete conjugated structure validate the presence of the coupling between the PbSe NQDs and the gamma-Fe2O3 NPs. This unique system has substantial advantages for biological applications such as bio-sensing, detection of cancer cells, and drug delivery.