A plasmonic random laser tunable through stretching silver nanowires embedded in a flexible substrate has been investigated.

Highly efficient inorganic phosphors are desirable for lighting-emitting diode light sources, and increasing the doping concentration of activators is a common approach for enhancing the photoluminescence quantum yield (PLQY). However, the constraint of concentration quenching poses a great challenge for improving the PLQY. Herein, we propose a fundamental design principle by separating activators and prolonging their distance in Eu²⁺-activated Rb₃Y(PO₄)₂ phosphors to inhibit concentration quenching, in which different quenching rates are controlled by the Eu distribution at various crystallographic sites. The blue-violet-emitting Rb₃Y(PO₄)₂:xEu (x = 0.1%–15%) phosphors, with the occupation of Rb1, Rb2 and Y sites by Eu²⁺, exhibit rapid luminescence quenching with optimum external PLQY of 10% due to multi-channel energy migration. Interestingly, as the Eu concentration increases above 20%, Eu²⁺ prefer to occupy the Rb1 and Y sites with separated polyhedra and large interionic distances, resulting in green emission with suppressed concentration quenching, achieving an improved external PLQY of 41%. Our study provides a unique design perspective for elevating the efficiency of Eu²⁺-activated phosphors toward high-performance inorganic luminescent materials for full-spectrum lighting.

Localized surface plasmon resonance (LSPR) is essentially a collective oscillation of free electrons in nanostructured metals. Interband excitation may also produce conduction-band electrons above the Fermi level. However, a question here is whether these excited electrons can take part in plasmonic oscillation. To answer this question, femtosecond pump-probe measurements on gold nanoparticles were performed using interband excitation, where the pump pulse produced a large amount of electrons in the sp-conduction band and left holes in the d-band. Probing by transient absorption spectroscopy, we resolved an induced LSPR feature located at a red-shifted spectrum. This feature cannot be observed for a pumping photon energy lower than the threshold for interband transition. The commonly observed red-shift or broadening of LSPR spectrum due to electron-electron and electron-phonon scattering under strong optical excitation can be ruled out for understanding this feature by a comparison between the plasmonic dynamics at a pump above and below the interband-transition threshold. In particular, a “holding” time of about 1 ps was resolved for the interband-excitation-induced electrons to relax to the LSPR oscillation.