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

Abstract

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.

Light-Emitting Microfibers from Lotus Root for Eco-Friendly Optical Waveguides and Biosensing

“…In acidic environments, the increase in the number of cations can lead to charge–charge repulsion, structural stiffening, and consequently higher emission. Such a fluorescence response is also consistent with intrinsic clustering-triggered emission. ,, The variation of the fluorescence intensity with pH is reversible, as found by measuring the PL intensity upon increasing the pH from 3 to 9 and vice versa in a liquid microenvironment, for 10 consecutive cycles (Figure S11).…”

Carboxylate-Protected “Isostructural” Cu20 Nanoclusters as a Model System: Carboxylate Effect on Controlling Catalysis

“…Featuring absolute monodispersion, well-defined chemical compositions, and a clear molecular structure, ligand-protected atomically precise metal nanoclusters have emerged as a new class of organic–inorganic hybrid nanomaterials. − Nanocluster materials not only have found application in a wide range of fields including catalysis, biology, sensing, electronics, and photonics but also, more importantly, function as a model system to gain insights into the fundamental structure–property relationships and surface/interface coordination chemistry of metal nanomaterials. ,− The organic ligands on the surface are the key to stabilize, shape, and functionalize metal nanoclusters, with thiolate, alkynyl, N-heterocyclic carbene, and phosphine as representative candidates for the access to nanoclusters of gold and silver. ,,,− Notably, the “ligand effect” has been frequently used to rationalize the catalysis of gold- or silver-derived cluster nanocatalysts, thus providing a rational way to modulate their performance. ,,,,,− For example, Jin et al modulated the catalytic properties of Au 25 nanoclusters via thiolate engineering. The catalytic performance of Au 25 in the Ullmann heterocoupling reaction between 4-methyl-iodobenzene and 4-nitro-iodobenzene is highly related to the chemical nature of the thiolate lig...…”

Recent Advances in Long-Lived Emission in Coinage Metal Nanoclusters: Implications for Optoelectronic Applications

“…While researchers endeavor to engineer compounds exhibiting TADF and RTP characteristics, the potential of luminescent materials with extended lifetimes and substantial Stokes shifts comes into full focus. − Conventional semiconductor nanocrystals, or quantum dots, have shown promise in optoelectronic applications due to their high luminous efficiency. − However, their toxicity due to heavy metals incorporated and the hazardous solvents has prompted scientists to actively seek out new materials that are both environmentally safe and sustainable for optoelectronic applications. − MNCs, known for their exceptional photophysical properties, emerge as promising substitutes. The integration of MNCs into these applications is propelling us toward the realm of “green photonics”, a significant aspiration within the scientific community aimed at developing more environmentally friendly and efficient technologies. − The clarification of the mechanism of the delayed emission requires the understanding of the excited state dynamics or the electron transition pathways within MNCs, which could be achieved by carefully tailoring their core and surface states. This understanding is crucial for the subsequent development of new nanoclusters that exhibit extended phosphorescence lifetimes and hold great promise in optoelectronics and bioimaging applications.…”