Multicolor Emitters Research Articles

Visual analysis of Alzheimer disease biomarker via low-potential driven bipolar electrode

Developing a simple, economical, and accurate diagnostic method has positive practical significance for the early prevention and intervention of Alzheimer's disease (AD). Herein, combining a closed bipolar electrode (BPE) chip with multicolor electrochemiluminescence (ECL) imaging technology, we constructed a low-voltage driven portable visualized ECL device for the early screening of AD. By introducing parallel resistance, the total resistance of the circuit was greatly reduced. A classical mixture of Ir(ppy)3 and Ru(bpy)32+ was used as multicolor emitters of the anode with TPrA as the co-reactant. Capture of amyloid-β (Aβ) through antigen-antibody recognition, and signal amplification by electroactive covalent organic frameworks (COF) probe at the cathode of BPE caused the significantly increased faradaic current. The electrical balance of the BPE system resulted in the change of the emission color from green to red at the anode. The ECL-BPE sensor shows good reproducibility and high sensitivity with detection limit of 1 pM by naked eye. The driving voltage is 3.0 V, which means the chip could be driven by two fifth batteries. The visualized ECL-BPE sensor provides a promising point-of-care testing (POCT) tool for the screening of Alzheimer's-related diseases in the early stage.

Organic polymorph-based alloys for continuous regulation of emission colors

<h2>Summary</h2> The luminescence of organic semiconductor materials is the key function for their lighting and display applications. Continuous regulation of emission colors based on one organic molecule system is still a challenge because of their individual emission band. Here we present a novel strategy for modulation of crystal nuclei and growth rates for different crystal phases, which contributes to fine synthesis of the organic polymorph-based alloy microwires that successfully exhibit continuous regulation of emission colors from blue to green. High supersaturation facilitates formation of <i>α</i>-phase microwires with blue emission (CIE [0.17, 0.23]), and low supersaturation is beneficial for self-assembly of <i>β</i>-phase microwires with green emission (CIE [0.29, 0.58]). Impressively, these organic polymorph-based alloy microwires were applied successfully to multicolor display and optical waveguides, which offer potential applications as continuous multicolor emitters for advanced photonics.

InGaN quantum well with gradually varying indium content for high-efficiency GaN-based green light-emitting diodes.

High-efficiency GaN-based green LEDs are of paramount importance to the development of the monolithic integration of multicolor emitters and full-color high-resolution displays. Here, the InGaN quantum well with gradually varying indium (In) content was proposed for improving the performance of GaN-based green LEDs. The InGaN quantum well with gradually varying In content not only alleviates the quantum-confined Stark effect (QCSE), but also yields a low Auger recombination rate. Consequently, the gradual In content green LEDs exhibited increased light output power (LOP) and reduced efficiency droop as compared to constant In content green LEDs. At 60 A/cm2, the LOPs of the constant In content green LEDs and the gradual In content green LEDs were 33.9 mW and 55.2 mW, respectively. At 150 A/cm2, the efficiency droops for the constant In content green LEDs and the gradual In content green LEDs were 61% and 37.6%, respectively. This work demonstrates the potential for the gradual In content InGaN to replace constant In content InGaN as quantum wells in LED devices in a technologically and commercially effective manner.

Building multi-color emitters with tailored lanthanide-based supramolecular metallogels

Multicomponent lanthanide-based metallogel offers unique prospects to access versatile, dynamic supramolecular soft materials with hierarchical stimuli-responsiveness and tunable functions, particularly for applications in the optical display field. In this work, a novel ligand L bearing classical coordinating terpyridine (tpy) and hosting 24-Crown-8 (24C8) moieties was synthesized with a function-oriented design principle, which further allowed the complexation between L and a series of lanthanide ions (Ln). Interestingly, several L-Ln complexes with 1:1 stoichiometry were found to be able to gel the solvent toluene/CH3CN (1:1), and thus lanthanide-based metallogels were successfully prepared. The L-Eu and L-Tb gel was found to be emissive and further utilized to produce a white light emitter through fine adjustment of stoichiometry among Eu, Tb, and L. Importantly, the multicomponent gel strategy was employed, and additional non-coordinating chromophores were introduced into the metallogel system. Thus a broad-spectrum of emission was achieved, and these multicomponent emissive gels were successfully applied as a photo printer. The metallogels also showed multiple stimuli-responsiveness such as pH, guest molecules thanks to the anchoring of predesigned functional moieties such as tpy and 24C8 on the ligand L. It is assumed that our multicomponent metallogel research shown here may open new avenues towards the design and preparation of intelligent and tunable hybrid lanthanide-based optical materials.

Toward efficient long-wavelength III-nitride emitters using a hybrid nucleation layer.

The realization of efficient III-nitride emitters in the green-to-amber region is fundamental to the monolithic integration of multicolor emitters and the development of III-nitride-based full-color high-resolution displays. A hybrid nucleation layer, which includes sputtered AlN and mid-temperature GaN components, was proposed for the development of efficient III-nitride emitters in the green-to-amber region. The mid-temperature GaN component in the hybrid nucleation layer induced the formation of a stacking fault band structure, which effectively relaxed the misfit stress at the GaN/sapphire interface. A reduced dislocation density and in-plane compressive stress in InGaN/GaN multiple quantum wells were obtained on the hybrid nucleation layer in comparison with the conventional sputtered AlN nucleation layer. Consequently, a significantly enhanced internal quantum efficiency and improved light output power were achieved for the LEDs grown on the hybrid nucleation layer. This gain is attributed to the increased localization depth and spatial overlapping of the electron and hole wave functions. In the present study, the hybrid nucleation layer provides a promising approach for the pursuit of efficient III-nitride emitters in the green-to-amber region.

Zirconium Metal-Organic Frameworks Containing a Biselenophene Linker: Synthesis, Characterization, and Luminescent Properties.

The bicyclic ditopic linker 2,2'-biselenophene-5,5'-dicarboxylic acid (H2SpSp), specifically designed for metal-organic framework (MOF) construction, has been synthesized in good yield and fully characterized. The corresponding zirconium MOF (Zr-MOF) [Zr6O4(OH)4(SpSp)3.8Cl4.4] (1; where missing linkers are replaced by chloride anions as shown by X-ray fluorescence and elemental analysis) is isostructural with its bithiophene and bithiazole analogues. Starting from 1, an extension of the biselenophene-based Zr-MOF family has been successfully achieved, exploiting the structural analogy of the five-membered heterocycles selenophene, thiophene, and thiazole. Thus, three mixed-linker MOFs containing variable amounts of different bis(heterocyclic) dicarboxylic acids have been prepared and fully characterized: the two double-mixed [Zr6O4(OH)4(SpSp)2.6(TpTp)1.3Cl4.2] (2; H2TpTp = 2,2'-bithiophene-5,5'-dicarboxylic acid) and [Zr6O4(OH)4(SpSp)2(TzTz)1.8Cl4.4] (3; H2TzTz = 2,2'-bithiazole-5,5'-dicarboxylic acid) materials, as well as the triple-mixed [Zr6O4(OH)4(SpSp)1.6(TpTp)1.2(TzTz)1.4Cl3.6] (4) compound. The four MOFs are luminescent under UV irradiation, exhibiting emission wavelengths falling in the blue-green visible region, as observed for their constitutive linkers. These materials open new horizons in the preparation of porous luminescent sensors or multicolor emitters for light-emitting diodes.

Synthesis of amphoteric fluorescent copolymers: materials exhibiting multicolor photophysical properties

Six emissive amphoteric copolymers were prepared and characterized (1H NMR, DSC, steady-state UV–vis, and emission spectroscopy) in the paper. A system of multi-color emitters, composed of P1 (green and yellow), P2 (green), P3 (red), P4 (blue), P5 (yellow) and P6 (green and yellow), were presented. P5 showed multicolor fluorescence that belonged to the color-specially emissive system at different excitation wavelengths, and P6 exhibited color-correlated emission by efficient energy transfer.

Indium Incorporation into InGaN Quantum Wells Grown on GaN Narrow Stripes.

InGaN quantum wells were grown using metalorganic chemical vapor phase epitaxy (vertical and horizontal types of reactors) on stripes made on GaN substrate. The stripe width was 5, 10, 20, 50, and 100 µm and their height was 4 and 1 µm. InGaN wells grown on stripes made in the direction perpendicular to the off-cut had a rough morphology and, therefore, this azimuth of stripes was not further explored. InGaN wells grown on the stripes made in the direction parallel to the GaN substrate off-cut had a step-flow-like morphology. For these samples (grown at low temperatures), we found out that the InGaN growth rate was higher for the narrower stripes. The higher growth rate induces a higher indium incorporation and a longer wavelength emission in photoluminescence measurements. This phenomenon is very clear for the 4 µm high stripes and less pronounced for the shallower 1 µm high stripes. The dependence of the emission wavelength on the stripe width paves a way to multicolor emitters.

Wavelength-Tunable Waveguide Emissions from Electrically Driven Single ZnO/ZnO:Ga Superlattice Microwires

Because of the superlattice structures comprising periodic and alternating crystalline layers, one-dimensional photon crystals can be employed to expand immense versatility and practicality of modulating the electronic and photonic propagation behaviors, as well as optical properties. In this work, individual superlattice microwires (MWs) comprising ZnO and Ga-doped ZnO (ZnO/ZnO:Ga) layers were successfully synthesized. Wavelength-tunable multipeak emissions can be realized from electrically driven single superlattice MW-based emission devices, with the dominant wavelengths tuned from ultraviolet to visible spectral regions. To illustrate the multipeak character, single superlattice MWs were selected to construct fluorescent emitters, and the emission wavelength could be tuned from 518 to 562 nm, which is dominated by Ga incorporation. Especially, by introducing Au quasiparticle film decoration, emission characteristics can further be modulated, such as the red shift of the emission wavelengths, and the multipeaks were strongly modified and split into more and narrower subbands. In particular, electrically pumped exciton-polariton emission was realized from heterojunction diodes composed of single ZnO/ZnO:Ga superlattice MWs and p-GaN layers in the blue-ultraviolet spectral regions. With the aid of localized surface plasmons from Au nanoparticles, which deposited on the superlattice MW, significant improvement of emission characteristics, such as enhancement of output efficiencies, blue shift of the dominant emission wavelengths, and narrowing of the spectral linewidth, can be achieved. The multipeak emission characteristics would be originated from the typical optical cavity modes, but not the Fabry-Perot mode optical cavity formed by the bilateral sides of the wire. The resonant modes are likely attributed to the coupled optical microcavities, which formed along the axial direction of the wire; thus, the emitted photons can be propagated and selected longitudinally. Therefore, the novel ZnO/ZnO:Ga superlattice MWs with a quadrilateral cross section can provide a potential platform to construct multicolor emitters and low-threshold exciton-polariton diodes and lasers.

Preparation and characterization of tunable YVO 4: Bi 3+, Sm 3+ phosphors

Yttrium vanadate phosphors co-doped with Bi 3+- and Sm 3+ ions have been prepared via the solid-state reaction as well as via the sol–gel method. The luminescence studies demonstrate the potential of the prepared phosphors as multi-color emitters, which can be achieved by adjusting the excitation wavelengths. The excitation spectra of Bi 3+- and Sm 3+ co-doped phosphors clearly revealed energy transfer from Bi 3+ to Sm 3+ ions. When the co-doped phosphors were excited at 254 nm, the emission from Bi 3+ was dominant. Upon excitation at 365 nm, the emission from both Bi 3+ and Sm 3+ was detected. With 410 nm excitation, Sm 3+ ions were selectively excited to yield intense red emission. It is shown that the prepared phosphors with optimal concentrations of Bi 3+ and Sm 3+ can be excited at 254, 365 and 410 nm to yield yellow, orange and red emissions, respectively.