Embedding hexanuclear tantalum bromide cluster {Ta6Br12} into SiO2 nanoparticles by reverse microemulsion method
2018
Chen, Wanghui | Wilmet, Maxence | Truong, Thai Giang | Dumait, Noée | Cordier, Stéphane | Matsui, Yoshio | Hara, Toru | Takei, Toshiaki | Saitō, Norio | Nguyễn, Thị Kim Ngân | Ohsawa, Takeo | Ohashi, Naoki | Uchikoshi, Tetsuo | Grasset, Fabien
Hexanuclear tantalum bromide cluster units [{Ta₆Brⁱ₁₂}Lᵃ₆] (i = inner, a = apical, L = ligand OH or H₂O) are embedded into SiO₂ nanoparticles by a reverse microemulsion (RM) based method. [{Ta₆Brⁱ₁₂}Brᵃ₂ (H₂O)ᵃ₄]·nH₂O (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 {Ta₆Br₁₂}@SiO₂ nanoparticles are analyzed by HAADF-STEM and EDS mappings. The presence and integrity of {Ta₆Br₁₂} in the SiO₂ nanoparticles are evidenced by EDS mapping, ICP-OES/IC and XPS analysis. The optical properties of {Ta₆Br₁₂}@SiO₂ nanoparticles are analyzed by diffuse reflectance UV-vis spectroscopy, further evidencing the integrity of the embedded {Ta₆Br₁₂} and revealing their oxidation state. Both {Ta₆Br₁₂}²⁺ and {Ta₆Br₁₂}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.
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