Efficient open-air synthesis of Mg2+-doped CsPbI3 nanocrystals for high-performance red LEDs.

Inorganic CsPbI3 perovskite nanocrystals (NCs) exhibit remarkable optoelectronic properties for illumination. However, their poor stability has hindered the development of light-emitting diodes (LEDs) based on these materials. In this study, we propose a facile method to synthesize Mg2+-doped CsPbI3 NCs with enhanced stability and high photoluminescence (PL) intensity under ambient air conditions. Theoretical calculations confirm that doped NCs possess stronger formation energy compared to undoped NCs. The undoped CsPbI3 NCs emit red light at approximately 653 nm. We optimize the doping ratio to 1/30, which significantly enhances the photoluminescence of single-particle CsPbI3 NCs. Subsequently, we fabricate a red LED by combining the CsPbI3 NCs with a blue chip. The resulting LED, based on the doped CsPbI3 NCs, exhibits excellent performance with a high luminance of 4902.22 cd m-2 and stable color coordinates of (0.7, 0.27). This work not only presents a simple process for synthesizing perovskite NCs but also provides a design strategy for developing novel red LEDs for various applications.

Multiplexed detection of heavy metal ions by single plasmonic nanosensors.

Detection of multiple analytes simultaneously in small liquid samples with high efficiency and precision is highly important to the fields like water quality monitoring. In this letter, we present a multiplexed nanosensors with position-encoded aptamer functionalized gold nanorods for heavy metal ions detection. The individual gold nanorods respond specifically to two different heavy metal ions (Pb2+ and Hg2+) with a spectral shift in the scattering spectrum. We used a home-built spectral imaging dark-field microscope to measure the response of thousands of single plasmonic nanosensors with relatively high time resolution and precision. To explore the performance and limit of detection (LOD) of our nanosensor and setup, we recorded the concentration-dependent response of our position-encoded nanosensors with a series of mixture solutions that contain different concentrations of Hg2+ and Pb2+ ions. The LOD levels of our system are around 5 nM for Pb2+ ions and 1 nM for Hg2+ ions. Our method and results demostrate the nanomolar sensitivity and the potential to detect more different heavy metal ions.

Design of phoxonic virtual waveguides for both electromagnetic and elastic waves based on the self-collimation effect: an application to enhance acousto-optic interaction.

The dual beam guides for transverse-electric and transverse-magnetic polarizations of electromagnetic (EM) wave and elastic wave in defect-free phoxonic crystals are reported. The realization for phoxonic virtual waveguides relies on dual flat equifrequency contours (EFCs) enabling self-collimation for EM and elastic waves. As a possible application of our work, the enhanced acousto-optic (AO) interaction in this kind of defect-free phoxonic waveguide, just as it does in defect-based waveguides, is further studied. Results show that obvious shifts of the transmission peaks of EM waves exist for both polarizations during one period of the elastic wave, and single-phonon exchange dominates the AO interaction. This kind of phoxonic virtual waveguide provides an effective platform to enhance AO interaction and exhibits some advantage over defect-based waveguides by properly manipulating the photonic and phononic dispersion surfaces.

All-inorganic CsPbBr3 perovskite quantum dots embedded in dual-mesoporous silica with moisture resistance for two-photon-pumped plasmonic nanoLasers.

Lead halide perovskite nanocrystals with efficient two-photon absorption and ease of achieving population inversion have been recognized as good candidates to achieve frequency up-conversion for biophotonics applications, but suffer from the limitation of the miniaturization of the device and its corresponding poor stability when exposed to atmospheric moisture. Here we demonstrate the miniaturization of plasmonic nanolasers via embedding perovskite quantum dots (QDs) in rationally designed dual-mesoporous silica with gold nanocore. The nanocomposite supports resonant surface plasmon-polaritons (SPPs), which overlap both spatially and spectrally with the CsPbBr3 QDs. The outcoupling between surface plasmon oscillations and photonics modes within a wavelength range completely overcomes the loss of localized surface plasmons, and finally contributes to a novel application of two-photon-pumped nanolasers. Large optical gain under two-photon excitation was observed as a result of resonant energy transfer from excited perovskite QDs to surface plasmon oscillations and stimulated emission of surface plasmons in a luminous mode. The outmost organic-inorganic hybrid shells of the dual-mesoporous silica nanocomposites act as a protective layer of the perovskite QDs against water and endow the nanocomposites with superhydrophobicity. This work provides an alternative inspiration for the design of new two-photon pumped nanolasers.