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

Wang, Xiaojian; Yin, Bing; Jiang, Lirong; Yang, Cui; Liu, Ying; Zou, Gang; Chen, Shuang; Zhu, Manzhou · Science · 2023

basic_science · Level V

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Abstract

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, Pt<sub>1</sub>Ag<sub>18</sub> and Au<i><sub>x</sub></i>Ag<sub>19-</sub><i><sub>x</sub></i> (7 ≤ <i>x</i> ≤ 9), were synthesized and structurally determined. Crystals of both exhibited excellent optical waveguide performance, with optical loss coefficients of 5.26 × 10<sup>-3</sup> and 7.77 × 10<sup>-3</sup> decibels per micrometer, respectively, lower than those demonstrated by most inorganic, organic, and hybrid materials. The crystal packing and molecular orientation of the Pt<sub>1</sub>Ag<sub>18</sub> compound led to an extremely high polarization ratio of 0.91. Aggregation enhanced the quantum yields of Pt<sub>1</sub>Ag<sub>18</sub> and Au<i><sub>x</sub></i>Ag<sub>19-</sub><i><sub>x</sub></i> 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.