Ligand-protected metal nanoclusters as low-loss, highly polarized emitters for optical waveguides.

Photoluminescent molecules and nanomaterials have potential applications as active waveguides, but have often been limited by high optical losses and complex fabrication processes. We explored ligand-protected metal nanoclusters, which can have strong, stable and tunable emission, as waveguides. Two alloy ligand-protected metal nanoclusters, Pt 1 Ag 18 and Au x Ag 19-x (7 ≤ x ≤ 9), were synthesized and structurally determined. Crystals of both nanoclusters exhibit excellent optical waveguide performance, with optical-loss coefficients of 5.26 × 10 -3 and 7.77 × 10 -3 decibels per micrometer, dB μm -1 , which are lower than those demonstrated by most inorganic, organic, and hybrid materials. The crystal packing and molecular orientation of the Pt 1 Ag 18 compound led to an extremely high polarization ratio of 0.91. Aggregation enhanced the quantum yields of Pt 1 Ag 18 and Au x Ag 19-x nanoclusters by 115- and 1.5-fold, respectively. This photonic cluster with low loss and high polarization provides a generalizable and versatile platform for active waveguides and polarizable materials.