Sunxuehao

Nature Photonics, Published online: 28 November 2022; doi:10.1038/s41566-022-01100-0

A layer-by-layer assembly route to achieve circularly polarized luminescence (CPL) with both high anisotropic factor and photoluminescence quantum yield is developed. The excellent CPL performance arises from the efficient generation of linearly polarized luminescence from the aligned quantum nanorods and then transformation to CPL by an inorganic nanowire-based quarter-wave plate.

Abstract

Materials with exceptional circularly polarized luminescence (CPL) are important in multi-field applications such as 3D display, anti-counterfeiting, sensing, spin electronics, etc. Although CPL properties have been widely investigated ranging from the traditional chiral organic molecules to the emerging chiral inorganic nanomaterials and their assemblies, a trade-off between the luminescence efficiency (quantum yield, ϕ) and the luminescence dissymmetry factor (g _lum) is always the bottleneck for all the chiral luminescent materials, which hinders their practical application. Herein, a new route to overcome the paradox through rationally assembling quantum nanorods and ultrathin inorganic nanowires into ordered multilayer structures is reported, achieving both high ϕ and g _lum. In these assembled structures, the aligned quantum nanorods emit linearly polarized light that is then transformed to CPL by the aligned ultrathin nanowire assemblies with precisely controlled phase retardation. This method is universal and readily extended to versatile 1D nanomaterials, paving the way for the practical applications of CPL active materials.

Accelerating electron-transfer dynamics by TiO₂-immobilized reversible single-atom copper is proposed for enhancing artificial urea photosynthesis using N₂ and CO₂ in pure H₂O. The quasi-in-situ characterizations reveal that the accelerated electron-transfer dynamics can be attributed to the reversibility of single-atom Cu for ensuring multi-electron-demand and supply of urea photosynthesis, thereby yielding as high as 432.12 µg g_cat. ⁻¹ of urea.

Abstract

Photocatalysis as a sustainable technology is expected to provide a novel sight for the green synthesis of urea directly using N₂, CO₂, and H₂O under mild conditions. However, the fundamental issue of inefficient electron transfer in photocatalysis strongly hinders its feasibility, especially for the above multi-electron-demanding urea synthesis. Herein, an effective strategy of accelerating electron-transfer dynamics is reported by TiO₂-immobilized reversible single-atom copper (denoted as Cu SA-TiO₂) to enhance the performance for photosynthesis of urea from N₂, CO₂, and H₂O. As revealed by a series of quasi-in-situ characterizations (e.g., electron paramagnetic resonance, and wavelength-resolved and femtosecond time-resolved spectroscopies), the expedited dynamics behaviors originating from reversible single-atom copper in as-designed Cu SA-TiO₂ (electron extraction rate: over 30 times faster than the reference photocatalysts) allow the assurance of abundant and continual photogenerated electrons for multi-electron-demanding co-photoactivation of N₂ and CO₂, resulting in considerable rates of urea production. The strategy above for improving the photoelectron-extraction ability of photocatalysts will offer a high-efficiency and promising route for artificial urea photosynthesis and other multi-electron-demanding photocatalytic reactions.