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

Photoluminescent molecules and nanomaterials have potential applications as active waveguides, but such a use has often been limited by high optical losses and complex fabrication processes. We explored ligand-protected metal nanoclusters (LPMNCs), which can have strong, stable, and tunable emission, as waveguides. Two alloy LPMNCs, Pt₁Ag₁₈ and AuAg_19- (7 ≤ x ≤ 9), were synthesized and structurally determined. Crystals of both exhibited excellent optical waveguide performance, with optical loss coefficients of 5.26 × 10^-3 and 7.77 × 10^-3 decibels per micrometer, respectively, lower than those demonstrated by most inorganic, organic, and hybrid materials. The crystal packing and molecular orientation of the Pt₁Ag₁₈ compound led to an extremely high polarization ratio of 0.91. Aggregation enhanced the quantum yields of Pt₁Ag₁₈ and AuAg_19- LPMNCs 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.