Europium Doped Atomically Precise Bismuth Oxido Nanoclusters as Molecular Building Blocks for Photoluminescent Hybrid Materials
Rico Thomas, Senthil Kumar Kuppusamy, Tobias Rüffer, Marcus Weber, Mario Ruben, Michael MehringABSTRACT
Structural and optical characterization of Eu 3+ doped atomically precise bismuth oxido nanoclusters (BiO‐NCs) of about 2 nm in size is reported. The BiO‐NC [Bi 38 O 45 (NO 3 ) 24 (dmso) 28 ]:Eu ( C‐1 D :Eu ) is transformed into soluble methacrylate ( − OMc) coordinated [Bi 38 O 45 (OMc) 24 (dmso) 4 ]:Eu·4dmso·4H 2 O ( C‐2 D :Eu ) and [Bi 38 O 45 (OMc) 24 (EtOH) 10 ]:Eu·4EtOH ( C‐2 E :Eu ) by ligand exchange and without changing the amount of Eu 3+ doping ( ω ≈ 1%). Based on SC XRD analysis of C‐1 D :Eu and C‐2 E :Eu partial substitution of the bismuth atoms with preference in the inner {Bi 6 O 9 } core of the {Bi 38 O 45 } cluster is suggested. Temperature dependent photoluminescence studies show bismuth‐ and europium‐based dual emission at low temperatures, whereas only the latter is preserved at room temperature. As a result of the low‐symmetry environment of Eu 3+ a remarkable intensity of the 5 D 0 → 7 F 0 (electric dipole) transition is observed, accompanied by lifetimes of about 2 ms and quantum yields ranging from 53% ( C‐2 D :Eu) to 65 % ( C‐1 D :Eu) . The solubility of C‐2 E :Eu enables its use for the synthesis of organic–inorganic hybrid materials. Thus, transparent hybrid materials were prepared by radical copolymerization of methyl methacrylate, 2‐hydroxyethyl methacrylate and C‐2 E :Eu , showing distinct photoluminescence characteristics even with a low Eu 3+ content of 2.7·10 −5 mol%.