Visible Light-Activated Ultralong-Lived Triplet Excitons of Carbon Dots for White-Light Manipulated Anti-Counterfeiting.

Room temperature phosphorescence (RTP) has emerged as an interesting but rare phenomenon with multiple potential applications in anti-counterfeiting, optoelectronic devices, and biosensing. Nevertheless, the pursuit of ultralong lifetimes of RTP under visible light excitation presents a significant challenge. Here, new phosphorescent materials that can be excited by visible light with record-long lifetimes are demonstrated, realized through embedding nitrogen doped carbon dots (N-CDs) into a poly(vinyl alcohol) (PVA) film.

Directional Self-Assembly of Facet-Aligned Organic Hierarchical Super-Heterostructures for Spatially Resolved Photonic Barcodes.

Organic multicolor heterostructures with spatially resolved luminescent colors and identifiable patterns have exhibited considerable potential for achieving micro-/nanoscale photonic barcodes. Nevertheless, such types of barcodes reported thus far are exclusively based on a single heterostructure with limited coding elements. Here, a directional self-assembly strategy is proposed to achieve high-coding-capacity spatially resolved photonic barcodes through rationally constructing organic hierarchical super-heterostructures, where numerous subheterostructure blocks with flat hexagonal facets are precisely oriented with their specific facets via a reconfigurable capillary force.

Suppressing phase disproportionation in quasi-2D perovskite light-emitting diodes.

Electroluminescence efficiencies and stabilities of quasi-two-dimensional halide perovskites are restricted by the formation of multiple-quantum-well structures with broad and uncontrollable phase distributions. Here, we report a ligand design strategy to substantially suppress diffusion-limited phase disproportionation, thereby enabling better phase control. We demonstrate that extending the π-conjugation length and increasing the cross-sectional area of the ligand enables perovskite thin films with dramatically suppressed ion transport, narrowed phase distributions, reduced defect densities, and enhanced radiative recombination efficiencies.

Solid-State Fluorescent Carbon Dots with Unprecedented Efficiency from Visible to Near-Infrared Region.

Developing solid-state luminescent materials with bright long-wavelength emissions is of considerable practical importance in light-emitting diodes (LEDs) but remains a formidable challenge. Here, a novel structure engineering strategy is reported to realize solid-state fluorescence (FL)-emitted carbon dots (CDs) from visible to near-infrared region. This is the first report of such an extended wavelength emission of self-quenching-resistant solid-state CDs.

2D/3D heterostructure derived from phase transformation of 0D perovskite for random lasing applications with remarkably improved water resistance.

Phase transformation between metal halide perovskites serves as a promising route to create new optoelectronic functionalities. Nevertheless, the transformation reported thus far mainly involves the transition between two individual phases (, 0D-3D and 3D-2D), while the transition from one phase to a heterostructure with distinct phases has been rarely disclosed. Here, we report a straightforward one-step procedure to directly convert 0D perovskite to 2D/3D heterostructures and demonstrate the application of the derivatives in random lasing beyond 0D perovskite.

Laterally Engineering Lanthanide-MOFs Epitaxial Heterostructures for Spatially Resolved Planar 2D Photonic Barcoding.

Metal-organic frameworks (MOFs) heterostructures with domain-controlled emissive colors have shown great potential for achieving high-throughput sensing, anti-counterfeit and information security. Here, a strategy based on steric-hindrance effect is proposed to construct lateral lanthanide-MOFs (Ln-MOFs) epitaxial heterostructures, where the channel-directed guest molecules are introduced to rebalance in-plane and out-of-plane growth rates of the Ln-MOFs microrods and eventually generate lateral MOF epitaxial heterostructures with controllable aspect ratios. A library of lateral Ln-MOFs heterostructures are acquired through a stepwise epitaxial growth procedure, from which rational modulation of each domain with specific lanthanide doping species allows for definition of photonic barcodes in a two-dimensional (2D) domain with remarkably enlarged encoding capacity.

Topological-Distortion-Driven Amorphous Spherical Metal-Organic Frameworks for High-Quality Single-Mode Microlasers.

Metal-organic frameworks (MOFs) have recently emerged as appealing platforms to construct microlasers owing to their compelling characters combining the excellent stability of inorganic materials and processable characters of organic materials. However, MOF microstructures developed thus far are generally composed of multiple edge boundaries due to their crystalline nature, which consequently raises significant scattering losses that are detrimental to lasing performance. In this work, we propose a strategy to overcome the above drawback by designing spherically shaped MOFs microcavities.

Spatially Responsive Multicolor Lanthanide-MOF Heterostructures for Covert Photonic Barcodes.

Micro/nanoscale photonic barcodes based on multicolor luminescent segmented heterojunctions hold potential for applications in information security. However, such multicolor heterojunctions reported thus far are exclusively based on static luminescent signals, thus restricting their application in advanced confidential information protection. Reported here is a strategy to design responsive photonic barcodes with heterobimetallic (Tb /Eu ) metal-organic framework multicolor heterostructures.

Gram-Scale Synthesis of 41% Efficient Single-Component White-Light-Emissive Carbonized Polymer Dots with Hybrid Fluorescence/Phosphorescence for White Light-Emitting Diodes.

Fluorescent carbon dots (CDs) are compelling optical emitters to construct white light-emitting diodes (WLEDs). However, it remains a challenge to achieve large-scale and highly efficient single-component white-light-emissive CDs suitable for WLED applications. Herein, a low cost, fast processable, environmentally friendly, and one-step synthetic approach is developed for the preparation of gram-scale and highly efficient single-component white-light-emissive carbonized polymer dots (SW-CPDs).

Dynamically wavelength-tunable random lasers based on metal-organic framework particles.

We propose a strategy to construct dynamically tunable random lasers by continuously adjusting the excited state of gain molecules spatially confined in the nanoporous channels of metal-organic framework particles. Wavelength-tunable random lasers are achieved by thermally manipulating the intramolecular charge transfer process of gain molecules. The wavelength-tunable response to thermal stimuli exhibits excellent reversible behavior.

Porous Core-Shell CuCo S Nanospheres as Anode Material for Enhanced Lithium-Ion Batteries.

Porous core-shell CuCo S nanospheres that exhibit a large specific surface area, sufficient inner space, and a nanoporous shell were synthesized through a facile solvothermal method. The diameter of the core-shell CuCo S nanospheres is approximately 800 nm" the radius of the core is about 265 nm and the thickness of the shell are approximately 45 nm, respectively. On the basis of the experimental results, the formation mechanism of the core-shell structure is also discussed.

Enabling random lasing in an ultrabroad spectral range with robust platforms based on amorphous media.

Random lasing with coherent feedback has been achieved in an ultrabroad spectral range of 533-870 nm when employing robust platforms based on amorphous media to provide optical feedback and modulating the gain curve. The pump threshold of the resultant random lasing is comparable to those reported with strongly scattering centers in crystalline forms and highly efficient microfiber systems. The findings suggest that amorphous media could serve as the base of robust platforms to investigate light-matter interactions in complex media and to create highly efficient light-emitting devices.

Controlling Random Lasing with Three-Dimensional Plasmonic Nanorod Metamaterials.

Plasmonics has brought revolutionary advances to laser science by enabling deeply subwavelength nanolasers through surface plasmon amplification. However, the impact of plasmonics on other promising laser systems has so far remained elusive. Here, we present a class of random lasers enabled by three-dimensional plasmonic nanorod metamaterials.

Wavelength-tunable spasing in the visible.

A SPASER, short for surface plasmon amplification by stimulated emission of radiation, is key to accessing coherent optical fields at the nanoscale. Nevertheless, the realization of a SPASER in the visible range still remains a great challenge because of strong dissipative losses. Here, we demonstrate that room-temperature SPASER emission can be achieved by amplifying longitudinal surface plasmon modes supported in gold nanorods as plasmon nanocavities and utilizing laser dyes to supply optical gain for compensation of plasmon losses.

Unidirectional spaser in symmetry-broken plasmonic core-shell nanocavity.

The spaser, a quantum amplifier of surface plasmons by stimulated emission of radiation, is recognized as a coherent light source capable of confining optical fields at subwavelength scale. The control over the directionality of spasing has not been addressed so far, especially for a single-particle spasing nanocavity where optical feedback is solely provided by a plasmon resonance. In this work we numerically examine an asymmetric spaser - a resonant system comprising a dielectric core capped by a metal semishell.

Plasmonically controlled lasing resonance with metallic-dielectric core-shell nanoparticles.

We experimentally demonstrate the capability of tailoring lasing resonance properties by manipulating the coupling between surface plasmons and photons in random lasing media composed of metallic-dielectric core-shell nanoparticles and organic dyes. It is revealed that core-shell nanoparticle-based systems exhibit optical feedback features distinctive from those containing pure metallic nanoparticles, provided that the scattering strength is weak enough. The pump threshold increases with an increment in the shell thickness, which can provide a direct proof that the local field enhancement plays a central role in the emergence of coherent feedback.

Random lasing in ballistic and diffusiveregimes for macroporous silica-based systems with tunable scattering strength.

We have systematically investigated random lasing properties in weakly scattering systems composed of a macroporous silica disk immersed in a dye solution where the solvent is a mixture of two alcohols. Controlling the refractive index of the mixed solvent allows us to vary the scattering strength over a wide range. We have found two different scattering regimes where sharp spectral spikes with linewidth less than 1.

Two-photon-excited fluorescence from silicate glass containing tantalum ions pumped by a near-infrared femtosecond pulsed laser.

We report a novel phenomenon in sodium-calcium-silicate glass doped with Ta(5+). Under irradiation with a 780 nm femtosecond pulsed laser, strong blue emission centered at about 420 nm could be observed. The spectral characteristics are similar to those pumped by ultraviolet photons.

Superbroadband 1310 nm emission from bismuth and tantalum codoped germanium oxide glasses.

Near-infrared broadband emission from bismuth-tantalum-codoped germanium oxide glasses was observed at room temperature when the glasses were pumped by an 808 nm laser diode. The emission band covered the O, E, S, C, and L bands (1260-1625 nm), with a maximum peak at approximately 1310 nm, a FWHM broader than 400 nm, and a lifetime longer than 200 micros. The observed broadband luminescence was attributed to bismuth clusters in the glasses.

Broadband infrared luminescence from Li2O-Al2O3-ZnO-SiO2 glasses doped with Bi2O3.

The broadband emission in the 1.2~1.6mum region from Li2O-Al2O3-ZnO-SiO2 ( LAZS ) glass codoped with 0.

Infrared broadband emission of bismuth-doped barium-aluminum-borate glasses.

We report near infrared broadband emission of bismuth-doped barium-aluminum-borate glasses. The broadband emission covers 1.3microm window in optical telecommunication systems.

Near infrared broadband emission of bismuth-doped aluminophosphate glass.

Near infrared broadband emission characteristics of bismuth-doped aluminophosphate glass have been investigated. Broad infrared emissions peaking at 1210nm, 1173nm and 1300nm were observed when the glass was pumped by 405nm laser diode (LD), 514nm Ar+ laser and 808nm LD, respectively. The full widths at half maximum (FWHMs) are 235nm, 207nm and 300nm for the emissions at 1210nm, 1173nm and 1300nm, respectively.

Bismuth- and aluminum-codoped germanium oxide glasses for super-broadband optical amplification.

Broadband infrared luminescence from bismuth-doped germanium oxide glasses prepared by a conventional melting-quenching technique was discovered. The absorption spectrum of the glasses covered a wide range from the visible to the near-infrared wavelength regions and consisted of five broad peaks below 370, 500, 700, 800, and 1000 nm. The fluorescence spectrum exhibited broadband characteristics (FWHM) greater than 300 nm with a maximum at 1300 nm pumped by an 808-nm laser.