Efficient Energy Transfer between Silicon Nanoparticles and a Ru−Polypyridine Complex

Blue-emitting amine-terminated Si nanoparticles (NPs; size, 1.57 ± 0.24 nm) are functionalized with a Ru(bpy) 2 (spb) 2+ [bpy = 2,2 ′ -bipyridine; spb = 4-( p - N -succinimidylcarboxyphenyl)-2,2′-bipyridine] complex. The distance between the dye and the Si core is controlled by different alkyl chain lengths (−C 3 H 6, −C 6 H 12, and −C 11 H 22 ), and the thus formed Si NPs are two-chromophore systems that exhibit dual-emission in two separate regions: blue (∼450 nm, from Si core) and red (∼630 nm, from Ru dye). By measuring the Si/Ru ratio, the extinction coefficient of amino-terminated Si NPs was experimentally determined for the first time (2.6 × 10 5 M −1 cm −1 ). Energy transfer from Si NPs to acceptor molecules [Ru(bpy) 2 (spb) 2+ ] is observed by steady-state and time-resolved fluorescence, and its distance-dependent efficiency is shown to be up to 55% in the case of a short alkyl spacer (−C 3 H 6 ). Energy transfer rates are for all examined cases in the (0.2−2.2) × 10 9 s −1 range.