Embedding hexanuclear tantalum bromide cluster {Ta6Br12} into SiO2 nanoparticles by reverse microemulsion method. Issue 6 (June 2018) - Chen, Wanghui
Abstract: Hexanuclear tantalum bromide cluster units [{Ta6 Br i 12 }L a 6 ] (i = inner, a = apical, L = ligand OH or H2 O) are embedded into SiO2 nanoparticles by a reverse microemulsion (RM) based method. [{Ta6 Br i 12 }Br a 2 (H2 O) a 4 ]· n H2 O (noted TBH) and tetraethyl orthosilicate (TEOS) are used as the starting cluster compound and the precursor of SiO2, respectively. The RM system in this study consists of the n -heptane (oil phase), Brij L4 (surfactants), ethanol, TEOS, ammonia solution and TBH aqueous sol. The size and morphology of the product namely {Ta6 Br12 }@SiO2 nanoparticles are analyzed by HAADF-STEM and EDS mappings. The presence and integrity of {Ta6 Br12 } in the SiO2 nanoparticles are evidenced by EDS mapping, ICP-OES/IC and XPS analysis. The optical properties of {Ta6 Br12 }@SiO2 nanoparticles are analyzed by diffuse reflectance UV-vis spectroscopy, further evidencing the integrity of the embedded {Ta6 Br12 } and revealing their oxidation state. Both {Ta6 Br12 } 2+ and {Ta6 Br12 } 3+ are found in SiO2 nanoparticles, but the latter is much more stable than the former. The by-products in this RM-based synthesis, as well as their related factors, are also discussed.